ArticlePDF Available

Biodiesel production using heterogeneous catalysts

January 2011
Bioresource Technology 102(3):2151-61

January 2011
102(3):2151-61

Authors:

Surbhi Semwal

Research & Development Centre, Indian oil corporation, Faridabad

Ajay Arora

indian oil corporation

Rajendra P Badoni

University of Petroleum & Energy Studies

Deepak K. Tuli

DBT-IOC

The production and use of biodiesel has seen a quantum jump in the recent past due to benefits associated with its ability to mitigate greenhouse gas (GHG). There are large number of commercial plants producing biodiesel by transesterification of vegetable oils and fats based on base catalyzed (caustic) homogeneous transesterification of oils. However, homogeneous process needs steps of glycerol separation, washings, very stringent and extremely low limits of Na, K, glycerides and moisture limits in biodiesel. Heterogeneous catalyzed production of biodiesel has emerged as a preferred route as it is environmentally benign needs no water washing and product separation is much easier. The present report is review of the progress made in development of heterogeneous catalysts suitable for biodiesel production. This review shall help in selection of suitable catalysts and the optimum conditions for biodiesel production.

Transesterification of vegetable oil.

…

ester content from palm kernel oil over supported metal oxides calcined at different temperature ( ** Reaction conditions: 60 °C, 10 wt.% of catalyst amount, methanol: oil molar ratio 65:1 and 3 h of reaction time).

…

Figures - uploaded by Surbhi Semwal

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Review

Biodiesel production using heterogeneous catalysts

Surbhi Semwal

, Ajay K. Arora

, Rajendra P. Badoni

, Deepak K. Tuli

⇑

College of Engineering, University of Petroleum & Energy Studies, Dehradun 248007, India

Research & Development Centre, Indian Oil Corporation Limited, Sector-13, Faridabad 121007, India

article info

Article history:

Received 5 May 2010

Received in revised form 21 September

2010

Accepted 18 October 2010

Available online 23 October 2010

Keywords:

Biodiesel

Homogeneous catalyst

Heterogeneous catalyst

abstract

The production and use of biodiesel has seen a quantum jump in the recent past due to beneﬁts associ-

ated with its ability to mitigate greenhouse gas (GHG). There are large number of commercial plants pro-

ducing biodiesel by transesteriﬁcation of vegetable oils and fats based on base catalyzed (caustic)

homogeneous transesteriﬁcation of oils. However, homogeneous process needs steps of glycerol separa-

tion, washings, very stringent and extremely low limits of Na, K, glycerides and moisture limits in biodie-

sel. Heterogeneous catalyzed production of biodiesel has emerged as a preferred route as it is

environmentally benign needs no water washing and product separation is much easier. The present

report is review of the progress made in development of heterogeneous catalysts suitable for biodiesel

production. This review shall help in selection of suitable catalysts and the optimum conditions for bio-

diesel production.

1. Introduction

Bio-based alternative fuels such as ethanol, biodiesel have been

in focus for the reasons which are by now well understood. Heavy

consumption of fossil resources, effect on global warming and con-

cerns of energy security are main drivers for growth of biofuels. Re-

cent studies on life cycle analysis (LCA) of biodiesel have shown a

very appreciable reduction of greenhouse gas (GHG) by their use as

a blend component of transport fuel. Biodiesel produced by transe-

steriﬁcation of vegetable oils and animal fats using homogeneous

base catalyst (Fig. 1) has seen several folds increase in last few

years for their commercial production and use as a blending com-

ponent in transport fuels.

Fatty acid methyl esters (FAME) have found favour for use as a

blend component of petro-diesel fuel due to lack of aromatics, neg-

ligible sulfur content, higher lubricity and very high cetane values

(Dorado et al., 2003). FAME (Biodiesel) mixes freely in all propor-

tions with petro-diesel and its use has been approved by almost

all the major automotive manufactures. Biodiesel can be used in

conventional compression ignition engines, which need almost

no modiﬁcation. Though biodiesel has been approved for use in

automotives as a blend with normal petro-diesel, there are very

stringent quality norms prescribed by several countries. ASTM

speciﬁcations listed and detailed by Sarin et al. (2007), which

any biodiesel must meet before it can be used as an auto fuel com-

ponent. There are very low limits on Na/K, organic/inorganic acids,

phosphorous, glycerides and water content. Therefore, biodiesel

production processes need to have in-built capability to meet these

speciﬁcations.

The most widely used industrial method for the commercial

production of biodiesel from vegetable oils/fats is a base catalyzed

transesteriﬁcation process using KOH or NaOH as the homoge-

neous catalyst and MeOH as the lower alcohol (Fig. 1). The advan-

tage of this process is production of methyl esters at very high

yields under mild conditions and reaction generally takes about

an hour for completion (Meher et al., 2006). Several oils, both edi-

ble and non-edible such as sunﬂower oil (Arzamendi et al., 2008),

palm (Li and Xie, 2006) and jatropha (Tiwari et al., 2007) have been

transesteriﬁed for biodiesel production. However, major quality re-

lated problems were encountered and it was main hindrance for

large scale industrial production of biodiesel by homogeneously

catalyzed transesteriﬁcation. Production costs were rather high

(Ma and Hanna, 1999) as the process involved number of washing

and puriﬁcation steps in order to meet the stipulated quality. It

was quite difﬁcult to remove the traces the K/Na remaining in

the product and separation of glycerin also posed technical chal-

lenges. The higher amount of water used in washing and conse-

quent treatment of the resulting efﬂuent added to the overall

process cost. Any commercial biodiesel plant must have the in-

built capability to handle a variety of different feedstocks which

may differ very widely in quality. The vegetable oils may be from

edible sources, non-edible sources, waste cooking oils, animal fats,

algae, fungi etc. (Canakci, 2007; Granados et al., 2007; Ji et al.,

2006; Karmee and Chadha, 2005).

In Europe and US, the primary sources for producing biodiesel

are edible oils like rapeseed, sunﬂower, and soybean. In countries

doi:10.1016/j.biortech.2010.10.080

⇑

Corresponding author. Tel.: +91 129 22 94 273; fax: +91 129 22 85 340.

E-mail address: tulidk@iocl.co.in (D.K. Tuli).

Bioresource Technology 102 (2011) 2151–2161

Contents lists available at ScienceDirect

Bioresource Technology

journal homepage: www.elsevier.com/locate/biortech

like India, non-edible oils like jatropha and karanjia are being pro-

moted on a very large scale, as these can be grown on marginal and

waste lands (Azam et al., 2005). Several other non-edible seeds like

Guizotia abyssinica (Sarin et al., 2009a) have also been evaluated

for their biodiesel potential. The conventional biodiesel production

process of base catalyzed homogeneous transesteriﬁcation face dif-

ﬁculties to handle multiple feed stocks. Oils (nonedible) with high-

er fatty acid content lead to formation of soap and consequent loss

of oil and problems of product separation (Kwiecien et al., 2009).

Due to these issues a large number of alternative methods were

developed. These include supercritical process (Minami and Saka,

2006) and enzymatic process (Shimada et al., 2002). Supercritical

process is also one of the promising methods for biodiesel produc-

tion as this process is very fast and is carried out without catalyst.

Some production plants in Europe use this technology, but due to

high temperature and pressure requirement of this process, it

translates to higher capital costs and that restricts its commercial

utilization. Sharma et al. (2006) explored a single pot process for

transesteriﬁcation of jatropha oil.

Enzyme based transesteriﬁcation is also one of the option for

biodiesel production and is generally carried out at moderate tem-

perature with high yields. Lipase enzymes (used with different

supports by immobilization or encapsulation etc.) are used for

transesteriﬁcation reaction (Caballero et al., 2009; Macario et al.,

2007, 2009). This process can tolerate free fatty acid and water

without soap formation and thereby making separation of biodie-

sel and glycerol easier. Enzyme cost and its deactivation due to

feed impurities are major hindrance for commercial viability of this

process (Dizge et al., 2009).

Biodiesel synthesis using solid catalysts instead of homoge-

neous liquid catalyst could potentially lead to economical produc-

tion costs because of reuse of the catalyst (Suppes et al., 2004) and

offer the possibility for carrying out both transesteriﬁcation and

esteriﬁcation simultaneously (Furuta et al., 2004).

Additional beneﬁt with solid based catalyst is the lesser con-

sumption of catalyst. As per studies, for production of 8000 tonnes

of biodiesel, 88 tones of sodium hydroxide may be required

(Mbaraka and Shanks, 2006), while only 5.7 tonnes of solid

supported MgO is sufﬁcient for production of 100,000 tonnes of

biodiesel (Dossin et al., 2006).

One disadvantage with use of solid catalyst is the formation of

three phases together with oil and alcohol, which leads to diffusion

limitations thus decreasing the rate of the reaction (Mbaraka and

Shanks, 2006). This mass transfer difﬁculty is overcome by using

a co-solvent such as tetrahydrofuran (THF), dimethyl sulfoxide

(DMSO), n-hexane and ethanol, which assist miscibility of oil and

methanol leading to increase in the rate of reaction. Use of catalyst

supports, which can provide more speciﬁc surface area and pores

for active species, where they can anchor and react with large tri-

glyceride molecules is another solution for encountering the poor

mass transfer (Zabeti et al., 2009). Some researchers (Di Serio

et al., 2008) have reviewed the signiﬁcance of solid catalysts for

biodiesel production. However, till date few detailed kinetic stud-

ies and the mechanism of acid and base catalysts using solid cata-

lysts have been reported in the literature (Furuta et al., 2004;

Suppes et al., 2004).

Chemistry of heterogeneous catalyst reported, includes metal

hydroxides (Dalai et al., 2006), metal complexes (Abreu et al.,

2003), metal oxides such as calcium oxide (Granados et al.,

2007), magnesium oxide (Wang and Yang, 2007), zirconium oxide

(Jitputti et al., 2006), zeolites, hydrotalcites and supported cata-

lysts (Xie and Huang, 2006). These types of catalysts have been

investigated as solid catalysts which overcome some of the draw-

back on use of homogeneous catalysts. The order of activity among

alkaline earth oxide catalysts was observed to be BaO > SrO > -

CaO > MgO (Cantrell et al., 2005).

The present review discusses the use of acid, base, acid–base so-

lid catalysts such as metal oxides, supported catalysts and zeolites

etc., and enzymatic catalysts for biodiesel synthesis. This review

paper presents a comparative description of continuous biodiesel

production processes, through transesteriﬁcation reaction using

acid, base, acid–base heterogeneous catalysts and enzymatic cata-

lysts so that proper catalyst and optimum reaction conditions can

be selected.

2. Heterogeneous catalysts

2.1. Basic solid catalysts

Various basic metal oxide type catalysts have been reported in

literature for biodiesel synthesis. Some of the high performing cat-

alyst preparations and their application in biodiesel synthesis are

summarized here.

Liu et al. (2007) studied SrO metal oxide for transesteriﬁcation

of soybean oil. Catalyst preparation was carried out by calcinations

of SrCO

at 1200 °C for 5 h. SrO has strong basicity H



= 26.5 and

have BET surface area of 1.05 m

/g. The conversion obtained was

95% at temperature of 65 °C, catalyst content of 3 wt.%, molar ratio

of methanol to oil of 12:1 and reaction time of 30 min. Further, bio-

diesel yield was only slightly reduced when the SrO catalyst is sub-

sequently reused for 10 cycles. Mechanism given by authors is as

described in Fig. 2. The main step is formation of ionic complex

by SrO with methanol.

Liu et al. (2008) studied transesteriﬁcation of soybean oil to bio-

diesel using CaO as a solid catalyst. The BET surface area of the cat-

alyst was 0.56 m

/g. The reaction was carried out using 12:1 M

ratio of methanol to oil, 8 wt.% catalyst concentration at 65 °C. Bio-

diesel yield (95%) was obtained when reaction was carried out for

3 h. The authors also reported comparative activity of CaO with

and KF/

catalysts. Preparation of these cata-

lysts was carried out by an impregnation method with the help

of aqueous solution of potassium carbonate/potassium ﬂuoride

and then calcination of impregnated catalysts at 550 °C for 5 h. It

was observed that CaO maintained sustained activity for longer

time (20 cycles) after repeated use and biodiesel yield was also

not affected, while K

and KF/

catalysts were

not able to maintain activity and biodiesel yield also got affected

after every use. This was because that the alkali metal compounds

dissolved in methanol, which reduced the active ingredients and

thereby decreasing biodiesel yield in the subsequent experiments.

It was also observed in this study that the presence of water, if in

small amount of about 2.8 by wt.% of soybean oil, act as promoter,

but if amount of water increases (more than 2.8 by wt.% of soybean

oil) it hydrolyzed FAME under basic conditions and also induced

soap formation.

The catalytic activity of activated calcium oxide was also evalu-

ated by Granados et al. (2007) for production of biodiesel by

OCOR'

OCOR''

COCOR'''

3 ROH

COH

ROCOR'

ROCOR''

ROCOR'''

catalyst

triglyceride alcohol mixture of

alkyl esters

glycerol

R', R'', R''' = Hydrocarbon chain ranging from 15 to 21 carbon atoms

(FAME)

Fig. 1. Transesteriﬁcation of vegetable oil.

2152 S. Semwal et al. / Bioresource Technology 102 (2011) 2151–2161

transesteriﬁcation of sunﬂower oil in batch reactor at 13:1 metha-

nol to oil molar ratio, 3 wt.% catalyst content at 60 °C. Under these

conditions, reaction was complete in 100 min giving 94% conver-

sion. The speciﬁc surface area of catalyst was 32 m

/g and mean

pore size diameter (MPS) was approx. 25–30 nm. The authors ob-

served poisoning of active surface site of CaO by the atmospheric

O and CO

. Therefore, to improve catalytic activity of CaO, it

was subjected to an activation treatment at high temperature

(P700 °C) before the reaction and as a result of this, the main poi-

soning species (the carbonate group) from the surface was re-

moved. When catalyst was activated at high temperature, some

leaching of the active species was observed. However, leaching

amount did not result in signiﬁcant reduction of catalyst activity

and the catalyst was reusable for 8 cycles. However, yield of FAME

reduced from more than 90% in the ﬁrst cycle to 80% in the second

cycle and thereafter the performance stabilized.

Veljkovic et al. (2009) described the kinetics of CaO heteroge-

neously catalyzed methanolysis of sunﬂower oil. The optimal

CaO calcination temperature was 550 °C. They observed 98% yield

in the transesteriﬁcation with 6:1 M ratio of sunﬂower oil to meth-

anol, 1 wt.% catalyst (based on oil wt.) at 60 °C within 2 h reaction

time.

Sarin et al. (2009b) reported use of seashell and eggshells as a

catalyst for production of biodiesel from various feed stocks such

as jatropha, castor, sunﬂower, soybean, rapeseed, cotton, corn,

coconut oils etc., in a batch and continuous reactor. The catalyst

combination of seashell and eggshells contained between 10–90%

and 90–10% respectively. The reaction was performed using

1 mol of vegetable oil and 6 mol of methanol and 4 wt.% of catalyst

composition. 98% conversion was achieved within 2 h.

Kawashima et al. (2009) studied catalytic activity of calcium

oxide (CaO) as a heterogeneous catalyst for biodiesel production

by the transesteriﬁcation of rapeseed oil. The author pretreated

CaO with methanol for activation. CaO was activated with metha-

nol at 25 °C for 1.5 h so that small amount of CaO could be con-

verted into Ca(OCH

)

, which exhibits a higher catalytic activity

than non-activated CaO. Rapeseed oil was thus transesteriﬁed

using Ca(OCH

)

to produce FAME and glycerine. During the

transesteriﬁcation reaction, the produced glycerin reacted with

CaO at 60 °C, and a CaO-glycerin complex was formed as secondary

catalyst, which then accelerated the transesteriﬁcation reaction.

While this CaO-glycerin complex exhibited a high catalyst activity,

the reaction advanced further and generated more glycerin. To

determine the exact pattern of catalytic activity, XRD measure-

ments of activated CaO, non-activated CaO, Ca(OH)

, and

Ca(OCH

)

were performed and it was observed that XRD spectrum

of activated CaO was similar to that of non-activated CaO but

exhibiting small diffraction peak attributed to Ca(OCH

)

and

Ca(OH)

. This was responsible for the observed differences in the

catalytic activity and the basic strengths of non-activated CaO,

Ca(OH)

. The activated CaO has basic strength in the range of

10.1–11.1. While Ca(OCH

)

had a high basic strength in the range

of 11.1–15.0 and these results explained the reasons why

Ca(OCH

)

exhibited a higher catalytic activity for the transesteri-

ﬁcation reaction than CaO and Ca(OH)

Kouzu et al. (2008) studied CaO catalyst for transesteriﬁcation

of soybean oil at 12:1 M ratio of methanol to oil at 500 rpm and

at reﬂux temperature for 2 h in glass batch reactor and achieved

93% biodiesel yield. CaO was obtained after calcination of pulver-

ized lime stone at 900 °C for 1.5 h. Calcium diglyceride and calcium

methoxide were used as reference samples. Further on comparison

it was observed that the BET surface area of fresh CaO is 13 m

whereas surface area of CaO collected after conversion was

11 m

/g. While the BET surface area of reference samples such as

calcium diglyceroxide and calcium methoxide were 11.3 m

and 44 m

/g, respectively.

Catalytic activity of calcium based metal oxides such as CaTiO

CaMnO

,Ca

, CaZrO

and CaO–CeO

in the methanolysis of

rapeseed oil was studied by Kawashima et al. (2008). The authors

also studied the change of activity on replacement of Ca with bar-

ium, magnesium, or lanthanum. The reaction was carried out in a

batch reactor at 60 °C with 6:1 M ratio of methanol to rapeseed

oil for 10 h, resulting in yield of 79–92%. It was found that CaZrO

and CaO–CeO

show high durability, ester yields greater than 80%

and has the potential to be used in biodiesel production processes

as heterogeneous base catalysts. For synthesis of CaTiO

, an equi-

molar mixture of TiO

and CaCO

was milled in an agate mortar

then mixture calcined in air to 500 °C and subsequently at

1050 °C for 2 h. For preparing Ca

,Fe

and CaCO

were

milled with molar ratio of 1:2 and calcined in air to 900 °C and then

-OH

Sr OSr O

O H

OR R

OCH

OSr O

ROH

OSr O

OH CH

OCH

ROH

Sr O

O H

OCH

OSr O

OCH

ROH

Fig. 2. Mechanism of SrO catalyst transesteriﬁcation.

S. Semwal et al. / Bioresource Technology 102 (2011) 2151–2161 2153

at 1050 °C for 4 h. Due to calcination step at high temperature, the

surface area of each of the catalysts was small and varied from

7.7 m

/g for MgCeO

to 0.71 m

/g for Ca

. The basic strengths

of CaTiO

were in the range of 6.8–7.2. CaMnO

,Ca

, CaZrO

and CaCeO

showed the highest basic strength, while Ba, Mg, and

La series catalysts had weaker basic strength. Hence, Ca series cat-

alysts exhibit the high catalytic activity for the transesteriﬁcation

reaction.

MgO-catalyzed transesteriﬁcation reaction, at industrially rele-

vant conditions was reported by Dossin et al. (2006) in batch and

continuous stirred tank reactors. A kinetic model based on the

three steps ‘Eley–Rideal’ type mechanism assuming methanol

adsorption as rate-determining step was proposed. Two processes

were simulated, ﬁrst for transesteriﬁcation of ethyl acetate with

methanol in a batch slurry reactor and second, transesteriﬁcation

of triolein with methanol to form methyl oleate in a continuous

slurry reactor and results were used to simulate biodiesel produc-

tion from rapeseed oil. In a continuous stirred reactor volume of

25 m

containing 5700 kg of MgO catalyst continuous production

of 100,000 tonnes of biodiesel per year can be achieved. These re-

sults were compared by the author with homogeneously catalyzed

transesteriﬁcation processes.

supported on MgO catalyst was prepared by mixing

and MgO as carrier in a mortar. The mixture calcined at

600 °C for 3 h, thus forming catalyst for synthesis of biodiesel from

soybean oil with the yield of 99.5% (Liang et al., 2009). These re-

sults indicate that carriers increased the reaction yield and basic

carriers have higher activities than acidic carriers. The catalytic

activity of the K

/MgO was higher than that of K

due to

the interaction between K

and MgO and because of the high

degree of dispersion of the active sites on the surface of MgO.

The maximum activity of catalyst was obtained when the loading

ratio was 0.7 and after 2 h reaction time the maximum conversion

was achieved in transesteriﬁcation when operating parameters are

set at 70 °C, 6:1 M ratio methanol to oil with 50 mg (0.01 wt.% of

oil) catalyst. The MgO supported K

catalyst was most efﬁcient

among all the catalyst from different carriers. After 6 cycles, the

catalytic activity decreased minutely but activity was regained

after calcination. The loss of the active sites on the catalyst was

also investigated.

Transesteriﬁcation of different edible and non-edible oils (such

as sunﬂower, soybean, ricebran and jatropha) using Mg/Zr catalyst

(catalyst ratio 2:1 wt/wt.%) have been reported by Sree et al., 2009.

Mg/Zr was prepared by co-precipitation method by dissolving

Mg(NO

)

and ZrO(NO

)

in deionised water. pH was controlled

at 10 by mixing of two precursors like KOH and K

. The precip-

itate was ﬁltered then washed and calcined at 650 °C for 4 h. The

XRD results indicated that ZrO

was in tetragonal phase, while

MgO was in rocksalt form. The catalyst showed small Zr and large

Mg crystallite sites, making Zr strongly interacted with MgO. How-

ever the high transesteriﬁcation activity of Mg/Zr catalyst might be

due to the presence of higher number of total basic sites. Total ba-

sicity of catalyst was 1204

mol/g while surface area was 47 m

/g.

The transesteriﬁcation reaction was carried out at 65 °C with a

53:1 M ratio of methanol to oil and a catalyst amount of 0.1 g

(0.1 wt.% of oil), to achieve the conversion of about 98% in

50 min. Due to higher number of total basic sites; the high transe-

steriﬁcation activity of catalyst was achieved. Insigniﬁcant de-

crease of yield up to 5% was observed during transesteriﬁcation

of sunﬂower oil after fourth cycle.

Samart et al. (2009) utilized 15 wt.% KI loaded on mesoporous

silica as a solid base catalyst for transesteriﬁcation of soybean oil

with optimum reaction conditions of 16:1 methanol to oil ratio,

5 wt.% catalyst at 70 °C in 8 h. Conversions of 90% were obtained.

The maximum activity of catalyst was obtained when KI solution

got impregnated on mesoporous silica by incipient wetness

impregnation with concentration of 15 wt.%. The X-ray diffraction

(XRD) patterns of KI/mesoporous silica after calcinations showed

that the characteristic peaks of potassium oxide (K

O) face-cen-

tered cubic crystal at 2hequal 25.3°, 41.9°, 51.9°, and 66.9°, while

the characteristic peaks of silicate hydrate phase (SiO

O) is at

21.8°and 35.7°but there was no characteristic peak of KI in the

XRD pattern because all of KI phases were transformed into K

phase.

Alumina-supported potassium iodide catalyst was applied for

biodiesel synthesis from soybean oil. The catalyst was prepared

by impregnation of powdered alumina with an aqueous solution

of KI, 35 wt.% KI loaded on Al

and calcined at 500 °C for 3 h

has best catalytic activity and highest basicity (1.5607 mmol/g)

(Xie and Li, 2006). The catalyst activity was dependent on

strength of basic sites as well as upon their amount. On

comparison of alumina loaded with KI, KF, KOH, K

, KBr and

KNO

, the order of conversion reported by the authors was

KI/Al

>KF/Al

>KOH/Al

>KNO

/Al

>KBr/

NaX zeolite loaded with 10% KOH (KOH/NaX) was reported as a

base catalyst in soybean oil transesteriﬁcation performed by Xie

et al. (2007). NaX zeolite was ﬁrst dried at 110 °C for 2 h then

impregnated with aqueous solution of KOH for 24 h followed by

drying and by heating at 120 °C for 3 h. The reaction was per-

formed at reﬂux temperature (65 °C), 10:1 M ratio of methanol to

oil and 3 wt.% catalysts. 85.6% conversion was achieved within

8 h. The results obtained by X-ray diffraction analysis showed

striking similarity in XRD pattern between KOH/NaX samples and

parent zeolites. Further, it was observed by SEM results that NaX

zeolite and KOH/NaX catalysts have nearly spherical shape crystal

with size of 2–4

m. The basic strengths of the catalyst as observed

was 15.0 < H_ < 18.4 and it’s very likely that higher percentage of

KOH (>10%) resulted in agglomeration of active sites and hence

lowering the surface areas for active components and resulting

lower the catalytic activity. The regenerated catalyst provides the

conversion rate of 84.3%.

Faria et al. (2008) utilized tetramethylguanidine, which is cova-

lently bonded onto silica gel surface (SiG), as solid catalyst for

transesteriﬁcation of soybean oil with methanol. SiG catalyst was

prepared by suspending activated silica gel in dry xylene and the

new agent silylant (Silylant was prepared by reacted SiCl with tri-

ethylamine). The SEM image showed that SiG catalyst particles had

spherical morphology with average size of about 1

m. It was also

observed that in SiG catalyst covalent immobilization of tetra-

methylguanidine onto the silica gel surface existed, which was

conﬁrmed by FTIR,

Si and

C NMR spectrums. The pore size

and BET surface area was 8.78 ± 0.73 nm and 216.14 ± 34 m

1

respectively. The reaction was performed with 1.5 g methanol,

10 g oil and catalyst content of 0.5 g (0.05 wt.% of oil) at 80 °C

and after 3 h, 86% of soybean oil was converted to biodiesel. The

yield decreased continuously from 86% to 62% after catalyst is

recycled for 9 times due to activity drop by loss of the weakly at-

tached tetramethylguanidine to the silica surface.

Georgogianni et al. (2009a) studied conversion of used soybean

frying oil over Mg MCM-41, Mg–Al hydrotalcite and K

impreg-

nated zirconia catalysts and found that the Mg–Al hydrotalcite

has the greater activity due to higher basicity. After 25 h under

operation conditions of 60 °C, 5 g oil, 65 ml methanol and 0.5 g of

catalyst (0.1 wt.% of oil), 97% of oil was converted to biodiesel.

Mg/Al hydrotalcite catalyst was synthesized by using mixture of

Mg(NO

)

O, Al(NO

)

O and (NH

)

at 65 °C for 1 h.

The pH was controlled at 5 by concentrate ammonia solution.

The mixture was agitated for 3 h at 65 °C and precipitate was ﬁl-

tered, dried and the calcined at 500 °C for 3 h.

Georgogianni et al. (2009b) also tested Mg MCM-41, Mg–Al

hydrotalcite and K

impregnated zirconia catalysts and found that

2154 S. Semwal et al. / Bioresource Technology 102 (2011) 2151–2161

Mg–Al hydrotalcite was more active catalyst due to its highly basic

nature for transesteriﬁcation of rapeseed oil giving quantitative

yield. MCM-41 also gave high yields of methyl esters in the transe-

steriﬁcation reaction (conversion 87%). Authors also compared

these results with that of homogenous catalyst (NaOH) in the

transesteriﬁcation reaction under identical reaction conditions

and found that the homogenous catalyst accelerated the transeste-

riﬁcation reaction signiﬁcantly and gave the equivalent conversion

only within 15 min.

KF/ZnO catalyst has been reported as solid base catalyst for the

transesteriﬁcation of palm oil with methanol to produce biodiesel

(Hameed et al., 2009). The KF/ZnO was synthesized by impregna-

tion of the ZnO support with aqueous of KF2H

O followed by over-

night drying at 110 °C and calcination at 600 °C for 5 h. A loading of

35 wt.% of KF was done on ZnO and good conversions were

achieved.

Yan et al., 2009 studied the ZnO-La

catalyst for transesteriﬁ-

cation of unreﬁned and waste oil. ZnO-La

was prepared by

homogeneous co-precipitation method where 2 M Zn(NO

)

and

1 M La(NO

) solutions were prepared in distilled water. These solu-

tions, with various Zn–La ratios, were mixed with a 2 M urea solu-

tion and the resulting mixture calcined at 450 °C for 8 h. The

catalyst with 3:1 ratio of Zinc to lanthanum was found to exhibit

highest activity in the transesteriﬁcation of unreﬁned or waste

oil. A strong interaction between Zn and La species was observed

with enhanced catalytic activities. The catalyst was active in both

transesteriﬁcation and esteriﬁcation reactions, and with no hydro-

lytic activity.

Sr(NO

)

/ZnO catalyst has been reported by Yang and Xie, 2007

for soybean oil transesteriﬁcation with methanol at 65 °C.

Sr(NO

)

/ZnO was prepared by an impregnation method with an

aqueous solution of an alkaline earth metal nitrate and calcined

at 600 °C for 5 h. The optimum catalytic activity was obtained by

loading 2.5 mmol of strontium nitrate Sr(NO

)

/g on ZnO. The ba-

sicity of catalyst was 10.8 mmol/g and 94.7% soybean oil conver-

sion was achieved after 5 h with 5 wt.% of Sr(NO

)

/ZnO and 12:1

methanol/oil molar ratio. However, Sr(NO

)

/ZnO after recovery

exhibited lower catalytic activity with a conversion of soybean

oil of 15.4% and it’s basicity decreased from 10.32 to 6.79 mmol/

g. This was due to decomposition of reactants and products on

the active sites and their interactions during the reaction. But the

catalytic activity of reused catalyst was regained by impregnating

it in an aqueous solution of Sr(NO

)

. They also observed that the

co-solvent such as dimethyl sulfoxide (DMSO), n-hexane and tetra-

hydrofuran (THF) overcomes the mixing problems of transesteriﬁ-

cation system and among them THF was the most effective co-

solvent which increased the conversion rate of soybean oil up to

96.8%.

The activity and selectivity of NaOH/

-Al

catalyst for the

transesteriﬁcation of sunﬂower oil with methanol was investigated

by Arzamendi et al. (2007). NaOH/

was synthesized by

incipient wetness impregnation of the 212–300

m size fraction

of alumina. Prior to use alumina support was calcined at 500 °C

for 12 h. Subsequently, the required amount of NaOH solution

were slowly added to the support, dried for 12 h at 120 °C followed

by calcination at 400 °C for 12 h. NaOH contents of the ﬁnal solids

were 10.7 and 19.3 wt.% and this was referred as 10-Al and 19-Al

respectively. XRD analysis revealed that a calcined and non-cal-

cined 19-Al catalyst was very similar with the presence of NaOH

and Na

diffraction peaks, both as hydrated compounds, as well

as sodium aluminate (NaAlO

). These results indicate that NaOH

has reacted with the support giving rise to the formation of alumi-

nate. For calcined sample, the reaction was performed at 50 °C,

12:1 M ratio of methanol/oil with 19-Al at 0.4 wt.% of NaOH which

gave the conversion rate of about 86% for 24 h. While the conver-

sion for the non-calcined 19-Al sample increased up to 99%. Thus

the result indicated that calcination of NaOH/

catalyst had

a negative effect on their activity.

Benjapornkulaphong et al. (2009) compared the catalytic per-

formance of Al

–supported alkali, alkali earth metal oxides and

effect of calcination temperature on activity of different catalyst

for transesteriﬁcation of palm kernel oil and crude coconut oil with

methanol. They found that Ca(NO

)

/Al

calcined at 450 °C was

the most suitable catalyst giving 94.3% conversion, however when

the calcination temperature was increased the methyl ester forma-

tion dropped due to the formation of inactive metal aluminates. On

the other hand NaNO

/Al

and KNO

/Al

improved methyl es-

ter formation tendency at the calcination temperature of above

550 °C but LiNO

/Al

catalyst was active with conversion of

91.6% at 450 °C calcination and 93.4% at 550 °C. Mg(NO

)

/Al

catalyst was not active at any calcination temperature (conversion

10.4% at 450 °C). These catalysts were prepared by the incipient

wetness impregnation of aqueous solution of the corresponding

metal salt precursors (nitrate salt of alkali and alkali earth metals)

on an aluminum oxide support followed by calcination at 450 °C

for 2 h. XRD results indicated that after calcination at 450 °Cof

Ca(NO

)

/Al

catalyst, mainly CaO species were formed. But

when the calcination was performed at higher temperature, crys-

talline CaO peak decreased. After 3 h of reaction time, at 60 °C with

65:1 M ratio of alcohol/oil and 10 wt.% catalyst content, the maxi-

mum conversion achieved was 94.3% from palm kernel oil whereas

only 85% conversion was obtained in the case of crude coconut oil

due to high acid value and moisture content of crude coconut oil

than palm kernel oil. But when catalyst amount was increased

from 15 to 20 wt.%, the conversion of crude coconut oil also in-

creased from 94% to 99.8%. Results of experiment are tabulated

in Table 1.

Kumar et al. (2010) reported an effective catalyst composition

which contained major amount of nickel zinc aluminate supported

on clay and alumina. On a continuous reactor system, this catalyst

gave conversion in the range of 40–60% at 200 °C and 40 bar

pressure.

Abdullah et al., 2009 reported use of SBA-15 as a neutral mate-

rial made up of Si-O-Si network as a catalyst for biodiesel produc-

tion. The incorporation of potassium into mesoporous SBA-15 (K/

SBA-15) imparted basicity to make it suitable for base catalyzed

reaction like transesteriﬁcation of palm oil. The authors used a

composite experimental design for optimization of biodiesel yield

so that this mathematical model could predict the biodiesel yield

at any point of time in the experimental domain as well as the

determination of the optimal biodiesel conditions with sufﬁcient

degree of accuracy. K/SBA-15 was prepared by impregnating the

high surface area material (mesoporous SBA-15) with 20 wt.%

KOH solution for 24 h. After that, catalyst was dried followed by

calcination at 350 °C for 3 h. The speciﬁc surface area of the cata-

lyst was high and has relatively easy diffusion of reactants in the

mesopores and thereby allowing the use of the mesoporous cata-

lyst at high temperature without suffering major structure modiﬁ-

Table 1

Methyl ester content from palm kernel oil over supported metal oxides calcined at

different temperature (**Reaction conditions: 60 °C, 10 wt.% of catalyst amount,

methanol: oil molar ratio 65:1 and 3 h of reaction time).

Catalyst Optimum calcination

temperature (°C)

Methyl ester

content (wt.%)**

450 0

LiNO

550 93.4

NaNO

O3 650 95.1

KNO

550 94.7

Mg(NO

)

450 10.4

Ca(NO

)

450 94.3

S. Semwal et al. / Bioresource Technology 102 (2011) 2151–2161 2155

cation. 93% conversion was achieved in 5 h at 70 °C with methanol/

oil molar ratio of 11.6 and catalyst content of 3.91 wt.%.

2.2. Acidic solid catalysts

Di Serio et al. (2007) investigated application of vanadyl phos-

phate (VOP) as catalyst in the transesteriﬁcation of soybean oil.

They found that the catalyst was active in transesteriﬁcation reac-

tion with 80% methyl ester yield obtained only after 1 h reaction

time even though the speciﬁc surface area of catalyst was low

(2–4 m

/g). Vanadyl phosphate was prepared from the suspension

of V

in diluted phosphoric acid and then calcined at 500 °C for

2 h. The catalytic activity was increased by the increasing the cal-

cination temperature, which helped in removing the hydration

water of the sample and thus, increasing the concentration of the

coordinatively unsaturated VO group and resulted in increased Le-

wis acidity of solids. XRD results indicated that uncalcined VO-

2H

O has crystallographic

form of peaks while another

crystallographic

peaks was observed in the case of calcined

VOPO

(VOP

500

Shu et al. (2009) studied carbon based solid acid catalyst for

transesteriﬁcation of cottonseed oil with methanol. The carbon

based solid acid catalyst was prepared by the sulfonation of car-

bonized vegetable oil asphalt. The catalyst was prepared from car-

bonized vegetable oil asphalt and concentrated H

solution.

Both these ingredients were heated at 210 °C in an oil bath for

10 h. The suspension was diluted by de-ionized water and dried

at 120 °C for 4 h to obtain the sulfonated vegetable oil asphalt cat-

alyst. The authors also compared transesteriﬁcation efﬁciency of

asphalt-based catalyst with sulfonated multi-walled carbon nano-

tubes (s-MWCNTs) and observed that the asphalt-based catalyst

showed higher activity than the s-MWCNTs with 90% conversion.

This is because of high Bronsted acid site density (2.21 mmolg

1

loose irregular network and large pores (43.90 nm), which provide

more acid sites for the reactants. The low surface area

(7.48 m

1

) and high SO

H density (2.21 mmol g

1

) of the dry

sulfonated carbon catalysts indicated that most of the SO

groups were in the interior of the catalyst. The sulfonated polycy-

clic aromatic hydrocarbons provided an electron-withdrawing

function to keep the acid site stable. The morphology of carbon cat-

alyst (SEM) indicated that after the sulfonation treatment by con-

centrated H

, the particle agglomerates had disintegrated to

some extent and the pores have became larger. The disintegration

of the agglomerated particles also implied that the prepared car-

bon material catalyst had a high quantity of external acid sites

which can be made available to the reactant. The catalyst was able

to catalyze the transesteriﬁcation reaction for two cycles without

any treatment, but from third cycle, activity decreased due to

swelling effect. In recycling experiments combined inﬂuence of

catalyst swelling and deactivation due to leaching of SO

H can

be seen and further more it was observed that activity improved

when swelling exceeded the effect of the leaching of SO

H group.

Sulfated zirconia solid acid catalyst was studied for transesteri-

ﬁcation reaction of soybean oil and simultaneous esteriﬁcation of

oleic acid with methanol and ethanol in a high pressure reactor

by Garcia et al. (2008). Sulfated zirconia was prepared by either

solvent free method (S-ZrO

) or standard precipitation method

(SZ). In solvent free method ZrOCl

8H

O and (NH

)

are mixed

in molar ratio of 1:6 for 20 min at room temperature and calcined

at 600 °C for 5 h. Whereas, in standard precipitation method, SZ

was prepared by precipitation of zirconium oxychloride hydrate

(ZrOCl

.8H

O) with ammonium hydroxide at pH 8.5 and then

washed, dried and after that powder was sulfated by impregnated

and then calcined at 650 °C for 4 h. They found that sulfated

zirconia prepared by solvent free method was very active in the

transesteriﬁcation as well as esteriﬁcation reaction. The conversion

in alcoholysis catalyzed by S-ZrO

obtained under optimized con-

ditions at 120 °C, 5 wt.% of catalyst (w/w) was 98.6% (methanoly-

sis) and 92% (ethanolysis) respectively after 1 h. The performance

of ethanolysis was not as good as in methanolysis due to the higher

water content of ethanol (0.44%) compared to methanol (0.08%). S-

ZrO

was an amorphous material while SZ are crystalline (tetrago-

nal and monoclinic phases of zirconia) as depicted by XRD.

Carma et al. (2009) studied the Al-MCM-41 mesoporous

molecular sieves with Si/Al ratio of 8 for esteriﬁcation of palmitic

acid with methanol, ethanol and isopropanol. The catalyst

Al-MCM-41 with ratio of 8 of Si/Al, produced the highest conver-

sion at 130 °C, 0.6 wt.% catalysts with alcohol to acid molar ratio

of 60 and reaction time of 2 h. The conversion rates for catalyst

were 79%, 67%, and 59% for methanol, ethanol, and isopropanol,

respectively. Catalyst Al-MCM-41 was synthesized by dissolving

aluminum chloride hexahydrate (AlCl

.6H

O) in a cetyltrimethyl-

ammonium (CTABr) and sodium hydroxide (NaOH) under

intense agitation and by adding tetraethylorthosilicate (TEOS).

The ﬁnal product was then dried in an oven at 105 °C for 24 h, fol-

lowed by thermal treatment in oven at 550 °C for 7 h and thus,

eliminating the surfactant residue (CTABr) from the pores of the

aluminosilicate. The catalyst was calcined at 480 °C for 3 h. XRD re-

sult showed that the samples have crystallographic patterns char-

acteristic of the mesoporous solid aluminosilicate Al-MCM-41. An

increase in the amount of aluminum incorporated into the mesop-

ores leads to disorder in the structural arrangement of Al- MCM-

41.

Zeolite beta modiﬁed with La (La/zeolite beta) had been tested

as a solid acid catalyst for methanolysis of soybean oil (Shu et al.,

2007). Zeolite beta has a high silica zeolite, containing an intersect-

ing three dimensional structure of 12 member ring channels. Due

to this relatively voluminous channel structure, it is possible to

carry out numerous acid catalyzed reactions effectively. The La/

zeolite beta catalyst was prepared by an ion exchange method by

the suspension of zeolite beta in lanthanum nitrate (La(NO

)

aqueous solution under vigorous stirring at room temperature for

3 h and dried at 100 °C for 24 h and ﬁnally calcined at 250 °C for

4 h. The conversion of triglyceride of 48.9 wt.% was observed.

The SEM result indicated that crystal structure of La/zeolite beta

became considerably less agglomerated than zeolite beta due to

the modiﬁcation because of La

(Na

is exchanged with La

that instable framework aluminum will be stabilized). The higher

Si/Al ratio can be related to higher structure stability of the tetra-

hedral framework aluminum. FTIR result indicated La/Zeolite beta

shows higher conversion and stability than zeolite beta for the pro-

duction of biodiesel, which may be correlated to the higher quan-

tity of external Bronsted acid sites available for the reactants (the

increment of the intensity of Bronsted acid sites can be attributed

to the presence of Si–OH–La groups and La–OH groups in the La/

zeolite beta after ion exchange).

Karmee and Chadha (2005) used Hb-zeolite, montmorillonite K-

10 and ZnO catalysts for transesteriﬁcation of non-edible oil of

crude Pongammia Pinnata with 1:10 M ratio of oil/methanol,

0.575 g (0.115 wt.% of oil) catalyst in 5 g oil at 120 °C. They found

that ZnO gave the highest conversion rate of 83%, while Hb-zeolite,

montmorillonite K-10 catalyst gave low conversion rates of 59%

and 47% respectively after 24 h of reaction time.

Jitputti et al. (2006) compared the catalyst activities of several

acidic and basic solids catalysts such as ZrO

, ZnO, SO

2

=SnO

2

=ZrO

, KNO

/KL zeolite and KNO

/ZrO

for transesteriﬁcation

of crude palm kernel oil (PKO) and crude coconut oil (CCO) with

methanol. Among the catalysts, sulfated zirconia (SO

2

=ZrO

), a

super acid gave the highest amount of methyl ester yield due to

its high acid strength. The reaction was carried out at 200 °C with

1 wt.% catalyst content, 50 bar pressure and 6:1 of methanol/oil ra-

tio in a high pressure reactor. After 1 h reaction time, 90.3 and 86.3

2156 S. Semwal et al. / Bioresource Technology 102 (2011) 2151–2161

wt.% of methyl ester was obtained in the crude palm kernel oil and

crude coconut oil respectively. While in comparison ZrO

gave the

lower amounts of methyl esters content and yield. Crude palm ker-

nel oil yielded higher methyl ester than crude coconut oil due the

higher free fatty acid and water content of crude coconut oil which

reduced the methyl ester yield. The activity of solid catalysts

for crude palm kernel oil transesteriﬁcation was SO

2

=ZrO

2

=SnO

> ZnO > KNO

/ZrO

> KNO

/KL zeolite > ZrO

. In the

case of crude coconut oil the catalysts activity was in order

of SO

2

=ZrO

>SO

2

=SnO

> ZnO > KNO

/KL zeolite > KNO

/ZrO

ZrO

. However as compared with SO

2

=SnO

and SO

2

=ZrO

, the

basic ZnO catalyst gave higher methyl ester contents (98.9%) but

a lower methyl ester yield (86.1%) in PKO. In addition, spent

2

=ZrO

, was not directly reused for transesteriﬁcation (yield

only 27.7 wt.%), as catalyst deactivated due to combination of cat-

alyst leaching and blocking of active sites by the products or unre-

acted starting materials.

Application of sodium molybdate (Na

MoO

) was reported by

Nakagaki et al. (2008) for the methanolysis of different types of lip-

ids derived from soybean oil such as reﬁned soybean oil (0.7 mg

KOH/gm acid value), degummed soybean oil (1.0 mg KOH/gm acid

value, 180 ppm of phosphorous as phosphatides) and used frying

oil (1.5 mg KOH/gm acid value). The reaction was carried out at

65 °C with 54:1 of methanol/oil ratio, 5 wt.% catalyst contents in

3 h. The conversion achieved for reﬁned soybean oil, degummed

soybean oil and used frying oil were 95.6 wt.%, 92.6 wt.% and

94.6% respectively. The catalytic activity of the compound was

attributed to the presence of the sites of molybdenum (VI) that

has high Lewis acidity and can polarize at the alcohol O–H bond

leading to a transient species, which has high nucleophilic charac-

ter. Na

MoO

was synthesized by treating MoO

at 550 °C for 2 h

with NaOH solution. Subsequently MeOH was added and Na

MoO

O ﬁltered, washed by methanol and acetone and dried at

120 °C for 3 h.

Furuta et al. (2004) studied solid superacid catalysts such as

sulfated tin oxide (STO), tungstated zirconia-alumina (WZA) and

sulfated zirconium-alumina (SZA) for transesteriﬁcation of soy-

bean oil with methanol at 300 °C with 4.0 g of catalyst: molar ratio

of methanol to oil was 40:1. For the preparation of tungstated

zirconia-alumina (WZA), a mixture of hydrated zirconia powder

(amorphous), hydrated alumina (pseudo-boehmite), aqueous

ammonium metatungstate solution and de-ionized water were

put into a kneader with stirring for 25 min and there after extruded

in cylindrical pellets shape and followed by drying at 130 °C and

calcination at 800 °C for 1 h. The authors observed that among

the catalysts, tungstated zirconia-alumina catalyst showed highest

activity for transesteriﬁcation with 94% conversion in 8 h reaction

time while sulfated tin oxide and sulfated zirconium-alumina gave

80% and 70% conversions respectively.

Peng et al. (2008) prepared SO

2

/TiO

–SiO

solid for the produc-

tion of biodiesel from low cost feedstocks (50% oleic acid + 50% re-

ﬁned cotton seed oil) with high FFAs in autoclave reactor at 200 °C,

with molar ratio of methanol to oil 9:1 and 3 wt.% catalyst concen-

tration. The 92% conversion was obtained within 70 min reaction

time. SO

2

/TiO

–SiO

catalyst was synthesized when SiO

powder

was slowly added to tetraisopropyl titanate solution of isopropyl

alcohol under reﬂux for 4 h and dried at 110 °C for 2 h and then cal-

cined at 450 °C for 4 h. The subsequent TiO

–SiO

particles were

soaked in H

for 1 day and then dried. SO

2

/TiO

–SiO

was ﬁ-

nally obtained after calcination at 500 °C for 4 h. The authors ob-

served that the large speciﬁc surface area of catalyst (258 m

/g)

and the average pore diameter (10.8 nm) of the catalyst was big

enough for reactant and product molecules to pass through the

channels. The effect of FFA amount on the yield of esters was stud-

ied by adding 10, 30, 50 and 80 wt.% oleic acid to reﬁned cotton-

seed oil under similar reaction conditions and it was observed

that the FFA content increased the yield of methyl ester and the

rate of esteriﬁcation of oleic acid was higher than the rate of

transesteriﬁcation of cottonseed oil due to the better solubility of

FFAs of cottonseed oil in methanol.

Zirconia supported tungsten oxide (WO

/ZrO

) has been tested

as a solid acid catalyst for esteriﬁcation of palmitic acid with meth-

anol (Ramu et al., 2004). The catalyst was prepared by impregna-

tion of zirconium hydroxide gel with ammonium meta tungstate

with 2.5–25 wt.% WO

loading. The catalyst was dried and ﬁnally

calcined at 500 °C. The maximum conversion of 98% was obtained

at 5 wt.% WO

/ZrO

catalyst in 6 h reaction time. The presence of

crystalline WO

and monoclinic phase of zirconia appeared to re-

duce the catalytic activity. The acidity of 5 wt.% WO

/ZrO

catalyst

was 1.04 mmol/g, which decreased by increasing the amount of

due to excess coverage of WO

species on ZrO

Lopez et al., 2007 studied tungstated zirconia (ZrO

=WO

2

)as

strong solid acid catalyst for both esteriﬁcation and transesteriﬁca-

tion with methanol as a reactant. The authors evaluated the effect

of calcination temperature (400–900 °C) on the catalytic properties

of tungusted zirconia. Catalytic activities of esteriﬁcation and

transesteriﬁcation were increased with the formation of polymeric

W species in the presence of the tetragonal phase of the ZrO

sup-

port. They concluded that the optimum calcination temperature

800 °C was efﬁcient to activate tungstated zirconia for both transe-

steriﬁcation and esteriﬁcation reactions. They examined the

transesteriﬁcation of liquid-phase of triacetin at 60 °C and esteriﬁ-

cation of acetic acid at 60 °C (liquid phase) and 120 °C (gas phase)

with methanol. The maximum catalytic activity was obtained with

catalyst calcined at 800 °C due to the Bronsted acid sites which

contribute most of the activity.

Sreeprasanth et al. (2006) reported Fe–Zn double–metal cya-

nide (DMC) complex as a solid acid catalyst for esteriﬁcation/

transesteriﬁcation of sunﬂower oil. Double-metal cyanide com-

plexes have zeolite- like cage structures (Graverau and Garnier,

1984). The catalyst was synthesized by mixing three solutions;

aqueous solution of K

Fe(CN)

3H

O, a solution of ZnCl

in mixture

of distilled water and tert-butanol and a solution of tri-block

copolymer, in mixture of water and tert-butanol. The catalyst

was hydrophobic and contained only Lewis acidic sites. This is be-

cause of coordinatively unsaturated Zn

ions in the structure of

the Fe–Zn complex. The Fe–Zn complexes had a spherical morphol-

ogy as shown by scanning electron microscopy (SEM). The transe-

steriﬁcation reaction took place at temperature of 170 °C, with

methanol/oil ratio of 15:1 and 3 wt.% of catalyst and after 8 h of

reaction time and 98.3 wt.% conversions was obtained. The catalyst

was compatible for both esteriﬁcation (high amount of FFA in the

oil) and transesteriﬁcation. The water content did not inﬂuence

the FAME yield due to hydrophobicity of surface. The catalyst

was reused without any puriﬁcation and no signiﬁcant drop of

activity was detected in the transesteriﬁcation reaction.

2.3. Acid–base solid catalysts

Cheaper feedstocks like waste oils, animal fats cannot be con-

verted to biodiesel using the conventional base mediated process,

as the FFA of oils creates the problems of saponiﬁcation. Acids

can esterify FFA but the slow rates and limitation of using expen-

sive metallurgy makes it less accepted. Heterogeneous catalysts

having both acidic and basic sites have been investigated which

could esterify FFA and at the same time transesterify triglycerides

to biodiesel.

Lin et al. (2006) reported synthesis of mixed metal oxide meso-

porous silica material for TG transesteriﬁcation and simultaneous

esteriﬁcation of FFA. They prepared these mesoporous calcium sil-

icate mixed metal catalysts having different amount of calcium

oxide. A co-condensation method was used for preparation in

S. Semwal et al. / Bioresource Technology 102 (2011) 2151–2161 2157

which cetyltrimethyl ammonium bromide (CTAB) provided the mi-

celles template in a NaOH catalyzed reaction of tetraethylorthosil-

icate (TEOS) and the metal oxide. The catalyst after isolation was

freed from surfactant CTAB by calcination at 600 °C for 6 h. SEM/

TEM showed increased structural disorder with increasing content

of calcium oxide. XRD analysis showed total absence of peaks asso-

ciated with CaO and solid state NMR showed the structure similar

to crystalline calcium silicate. These catalysts could esterify soy-

bean oil in methanol in 24 h (80 °C) and could also esterify the free

acids. The recovered catalysts could be reused 30 times for transe-

steriﬁcation and 8 times for esteriﬁcation without signiﬁcant loss

of catalyst activity.

Lin et al. (2008) obtained a patent for preparation of mesopor-

ous calcium, magnesium silicate and barium silicate by co-conden-

sation method. By forming a mixed oxide from strong basic metal

oxide and weak acidic silica, the acidity of silica was signiﬁcantly

enhanced. In calcium silicates mixed oxide, silica sites were lewis

acidic, Ca sites as basic and hydroxyl group on surface acted as

Brönsted acids. The co-condensation procedure adopted were sim-

ilar to the one reported by authors earlier (Lin et al., 2006). The

three catalysts, having different Ca/Si ratios, were able to transe-

sterify soybean oil in 90–100% conversion level. The effective tem-

perature range was claimed to be 80 °C and complete conversion

took more than 26 h. Under similar conditions complete esteriﬁca-

tion of poultry fat acids could be achieved in 24 h. All the catalysts

were evaluated for recyclability’s and no loss of activity was no-

ticed in 20 cycles.

Very recently Macario et al. (2010) reported a biodiesel produc-

tion process by homogeneous/ heterogeneous catalyst system of

acid–base type. First the acid catalyst, both strong acid type USY,

BEA and weak acid catalyst of the type MCM-41 were prepared

by hydrothermal synthesis procedures. Later, for preparation of

acid–base type catalyst, potassium (K) was loaded on different

materials by ionic exchange methods. For K loading, the calcined

catalyst materials were treated with 1 M KCl solution at 80 °C

and the ratio of solid/solution was kept at 0.01 g/mL. These K

loaded samples were calcined again at 300 °C for 8 h. Transesteri-

ﬁcation reactions were carried out at 100 to 180 °C, molar ratio

of oil to methanol at 1:20, and using 5 wt.% of catalyst. At the

end of reaction, the catalyst was separated by centrifugation,

washed with water and dried overnight at 120 °C. It was observed

that strong acid catalysts like USY, BEA were not good for triglyc-

eride conversion and commercial potassium silicate was found to

be much better. The K loading of MCM-41 increased the conversion

of triglyceride to a great extent but biodiesel production was low

as the main products were FFA (32%), mono-glycerides (42%). The

K loaded delaminated zeolites (K ITQ-6) gave 97% triglyceride con-

version and biodiesel yield of 80%, under the similar reaction con-

ditions. However, when the recovered catalyst was recycled, a

sharp decrease in biodiesel yield was observed and this has been

attributed to leaching of K from the catalyst. The authors proposed

a conceptual ﬂow sheet of a continuous process in which two ﬁxed

bed reactors were employed, one for transesteriﬁcation and the

other for the catalyst regeneration.

2.4. Enzymatic catalysts

Considering the problems of saponiﬁcation during the transe-

steriﬁcation process, of oil having FFA, by adopting the basic cata-

lyst and slow reaction rate in acid catalyzed reactions, large efforts

have been made to investigate the enzymatically catalyzed transe-

steriﬁcation of oils. Enzymatic transesteriﬁcation avoids soap for-

mation, works at neutral pH, lower reaction temperatures and

thus can be economical. The reusability of enzymes by immobiliz-

ing these on solid supports have provided a new window of oppor-

tunity. Several methods for enzymatic immobilization like

covalent bonding, cross-linking and micro-encapsulation have been

reported. Lipase has been the main enzyme used for transesteriﬁca-

tion, as these are cheaper and are able to catalyze both hydrolysis

and transesteriﬁcation of triglycerides at very mild conditions and

thus are considered for biodiesel production (Goncalves et al.,

1996; Huge-Jensen et al., 1988; Oliveira et al., 1997).

Catalytic behavior of the Rhizomucor miehei lipase (RML) immo-

bilized on zeolite materials has been studied by Macario et al.

(2007) for biodiesel synthesis with olive oil, containing 76 wt.%

of oleic acid, and methanol. The result shows that biocatalysts have

high capabilities to transesterify fatty acids in olive oil for several

cycles with higher total biodiesel productivity compared to using

free enzyme. The results indicated that the zeolitic materials, hav-

ing a large number of Si-OH groups, are able to adsorb the lipase

enzyme in its open conformation. Silicalite-1 obtained by different

synthesis routes (synthesized in alkaline system and ﬂuorine med-

ia i.e. S1 and F-S2) and delaminated zeolite ITQ-2 has been pre-

pared as lipase-supports. The results were compared with free

enzyme and lipase covalently attached to the functionalized sepi-

olite/AlPO

. For the synthesis of enzyme immobilization, the RML

enzyme and the calcined support (wt. ratio: free enzyme/support

equal to 2.5) were mixed in 0.2 M phosphate buffer pH 7, and stir-

red at 250 rpm for 24 h at 0 °C. The support with immobilized li-

pase was separated by ﬁltration, washed with de-ionized water

and dried at 25 °C overnight. The total protein concentration was

calculated by UV absorption at 280 nm. The transesteriﬁcation

reaction were carried out at 40 °C temperature, 5:1 ratio of meth-

anol to oil (Ma and Hanna, 1999), 0.6 g for lipase/S1 and lipase /

ITQ-2 catalysts, 0.4 g for lipase/sepiolite/AlPO

or 100 mg of free li-

pase for 3 h reaction time. It was evaluated that the oleic acid con-

version of Lipase/ S1 and Lipase/ITQ-2 and free lipase were about

100%, 91% and 100%. Whereas, the lower oleic acid conversion

(about 65%) and methyl oleate content (about 43%) was obtained

of Lipase/sepiolite/AlPO

, but the stability of the lipase/sepiolite/

AlPO

biocatalyst was higher than that of the lipase/S1 and lipase/

TQ-2 biocatalysts. The authors also examined the productivity (mg

of methyl oleate/mg of enzyme/h of reaction) of catalysts and ob-

served that catalysts prepared by adsorption show the highest pro-

ductivity (more than twice) than free enzyme. However, the lipase/

sepiolite–AlPO

catalyst had a lower productivity than free lipase

as the covalent binding forces reduced the catalytic activity of

the immobilized lipase. The enzyme immobilized on zeolites was

recycled several times but it gradually leached from the support.

The methyl oleate content of biocatalysts was drastically decreased

from ﬁrst cycle to third cycle. The methyl oleate content decreased

from 79% to 51% for lipase/S1, and from 70% to 43% for lipase/ ITQ-

2. However, the lipase/sepiolite/AlPO

catalyst does not show any

enzyme leaching due to covalent binding of enzyme and support.

The recovered catalyst was washed with n-hexane, dried at room

temperature and stored at 0 °C until subsequent use.

Macario et al. (2009) reported that encapsulation of lipase en-

zyme (Rhizomucor miehei lipase) in highly ordered mesoporous

matrix by a sol–gel method that involves the hydrolysis/ polycon-

densation of a silica precursor at neutral pH and room tempera-

ture. The enzyme is encapsulated within the micellar phase of

the surfactant that is self-assembled with silica. The encapsulated

biocatalyst has been used for the transesteriﬁcation reaction of tri-

olein with methanol under solvent free conditions. The highest

fatty acid methyl esters yield (77%) was obtained after 96 h at

40 °C, with triolein:methanol molar ratio of 1:3 and 5 wt.% of cat-

alyst (1.5 wt.% of enzyme). For the preparation of heterogeneous li-

pase enzyme, two different immobilization procedures such as

encapsulation and the adsorption procedure were studied. In

encapsulation procedure, lipase solution was added to the cetyl-

trimethylammonium bromide (CTMABr) solution and stirred for

1 h at room temperature. The silica precursor was then introduced

2158 S. Semwal et al. / Bioresource Technology 102 (2011) 2151–2161

into the solution and, subsequently, ethanolamine (20 wt.%) was

added. The gelation was slow and the sol–gel was stirred for 24 h

at room temperature and pH 7.2 followed by the ﬁltration. After

that the liquid was analyzed by UV-adsorption at 280 nm to deter-

mine the degree of enzyme encapsulation and the enzyme/silica

weight ratio in the ﬁnal solid catalyst (immobilization yield). In

adsorption-immobilization procedure, 50 ml of a 0.2 M phosphate

buffer solution (pH 7.0) and RML was added to the support in pow-

der form. The mixture was stirred (250 rpm) for 24 h at room tem-

perature. The support with adsorbed lipase was washed twice with

de-ionized water and dried at 25 °C overnight and then the total

protein concentration was measured by UV absorption method at

280 nm. Various enzyme contents of MCM-41 were prepared by

this method and the authors observed that the immobilization

yield of lipase turns out to be higher than 95% for all the samples.

The order of the mesoporous structure moderately decreases when

the enzyme content increases, with molar ratio of enzyme to silica

ranging from 0.005 to 0.020. The pore diameter and BET surface

area and pore diameter were increased by increasing the enzyme

amount that produces the swelling of the micelle of surfactant.

The yield of methyl esters and the enzyme activity increases with

the amount of lipase loaded. It was observed that the FAME yields

of free lipase at 18 h of reaction are lower than those obtained with

the encapsulated lipase. But after 70 h, the FAME yield is close to

80% for the encapsulated and 50% for free lipase. Therefore, due

to interaction of hydrophobic chains of the surfactant with the

hydrophobic patches of the enzyme, enzyme structure gets opened

and accessibility of the lipase catalytic centre to the reactants gets

increased. Hence, even after the presence of surfactant, enzyme

activities are not inhibited. Total productivity of the immobilized

enzyme is almost six times higher than the one obtained using free

lipase.

Caballero et al. (2009) studied the free and immoblized Pig pan-

creatic lipase (PPL) enzyme on sepiolite for transesteriﬁcation of

sunﬂower oil and alcohol. The optimum reaction conditions of free

and immobilized Pig pancreatic lipase were: reaction temperature

of 40 °C, oil to ethanol ratio of 2:1 v/v, pH of 12 and catalyst con-

tents of 0.01 g (0.1 wt.% of total substrate) for free PPL and 0.5 g

of demineralised sepiolite containing 0.01 g of immobilised PPL

(0.1 wt.% of total substrate) for immobilized PPL. The PPL activity

was increased on increasing pH value (12) and the maximum bio-

diesel yield found after 10 h reaction time was around 57.7% and

26.9% for free PPL and immobilized PPL respectively. The enzyme

PPL was immobilized on sepiolite, which is a natural silicate having

ﬁbrous structure, after acid treatment to remove Mg atoms. The

Mg free sepiolite was treated with PPL enzyme in ethanol at 0 °C

for 24 h, centrifuged to remove the non-immobilized enzyme.

Through the immobilized enzyme was less efﬁcient as compared

to the free enzyme, but the ease of recyclability and retention of

initial enzyme activity were major factors favour of its use for bio-

diesel production.

Immobilized Lipase (Thermomyces lanuginosus) on novel micro-

porous polymer matrix (MPPM) has been tested for the transesteri-

ﬁcation reaction of sunﬂower, soybean and waste cooking oils with

methanol as a low cost biocatalyst (Dizge et al., 2009). Poly HIPE

using styrene, divinylbenzene, and polyglutaraldehyde was used

to synthesize Microporous polymeric matrix (MPPM) containing

aldehyde functional group. Thermomyces lanuginosus lipase was

covalently attached onto MPPM with 80%, 85%, and 89% immobili-

zation efﬁciencies using bead, powder, and monolithic forms,

respectively. MPPM synthesis (monolithic, bead, and powder

forms), microporous polymeric biocatalyst (MPPB) preparation by

immobilization of lipase onto MPPM and biodiesel production by

MPPB are the three aspect of the process on which research is fo-

cused. MPPM was prepared by polymerizing the continuous phase

of a high internal phase emulsion consisting of organic and water

phases. The organic phase was composed of styrene, divinylben-

zene, and Span 80. While potassium persulphate and polyglutaral-

dehyde solution were contained in water phase. Immobilization of

lipase was carried out by reaction of powder (4–8 mesh in size) or

bead matrix with enzyme in calcium acetate buffer (25 mM, pH 6)

at 26 °C for 25 h with gentle shaking (250 rpm). Then, to remove the

unbound enzyme the immobilized enzyme was washed with ace-

tate buffer. SEM micrographs and FTIR spectrum showed that

copolymer can be produced as a porous structure having aldehyde

functional groups. The immobilization efﬁciencies obtained using

bead and powder forms were 80% and 85%, respectively. The transe-

steriﬁcation reaction was carried out in accordance with design of

experiment based on Taguchi methodology at 65 °C, 1:6 M ratio

of oil and methanol, 250 rpm of stirring and 0.0108 wt.% of immo-

bilized lipase (powder or bead form) for 24 and 5 h in batch reactor.

Methanol was added to the mixture in three-steps to avoid strong

methanol inhibition. In 5 h reaction time, biodiesel yields for sun-

ﬂower oil was 63.8%, 81.1%, and 86.9% using monolithic, bead,

and powdered MPPB, respectively. It was observed that the most

effective biocatalyst was powdered MPPB for the production of bio-

diesel as it get efﬁciently mixed with reactants during reaction. It

was also observed that the immobilized enzyme retained the activ-

ity during 10 repeated batch reactions.

3. Conclusions

Several solid acidic catalysts have been investigated for biodie-

sel synthesis but their uses have been limited due to lower reaction

rates and unfavorable side reactions. Basic heterogeneous catalysts

have also been investigated but their activity gets degraded in the

presence of water. Acid–base catalysts are one of the potential cat-

alysts because they catalyze both esteriﬁcation and transesteriﬁca-

tion simultaneously. Enzymatic catalysts though highly promising

but are rather slow. For a successful commercial catalyst, catalyst

life, recyclability and lower cost are extremely important as these

have a direct effect on overall cost of the process. Only few reports

indicate the commercial level production of biodiesel by adopting

the heterogeneous catalyst route.

Acknowledgements

The authors would like to express their gratitude to the Univer-

sity of Petroleum and Energy Studies, Dehradun and to Manage-

ment of R&D Centre, Indian Oil Corporation Limited, Faridabad

for the permission to publish this work.

One of the author (S. Semwal) would like to thank University of

Petroleum and Energy Studies for award of research fellowship.

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Feb 2021

The dwindling of global petroleum deposits and worsening environmental issues have triggered researchers to find an alternative energy such as biodiesel. Biodiesel can be produced via transesterification of vegetable oil or animal fat with alcohol in the presence of a catalyst. A heterogeneous catalyst at an economical price has been studied widely for biodiesel production. It was noted that various types of natural waste shell are a potential calcium resource for generation of bio-based CaO, with comparable chemical characteristics, that greatly enhance the transesterification activity. However, CaO catalyzed transesterification is limited in its stability and studies have shown deterioration of catalytic reactivity when the catalyst is reused for several cycles. For this reason, different approaches are reviewed in the present study, which focuses on modification of waste-shell derived CaO based catalyst with the aim of better transesterification reactivity and high reusability of the catalyst for biodiesel production. The catalyst stability and leaching profile of the modified waste shell derived CaO is discussed. In addition, a critical discussion of the structure, composition of the waste shell, mechanism of CaO catalyzed reaction, recent progress in biodiesel reactor systems and challenges in the industrial sector are also included in this review.

Biodiesel production from rubber seed oil using calcined eggshells impregnated with Al 2 O 3 as heterogeneous catalyst: A comparative study of RSM and ANN optimization Graphic abstract Keywords Artificial neural network · Biodiesel · Response surface methodology · Transesterification · Rubber seed oil

Article

Mar 2020

Experimental parameters influencing the transesterification of rubber seed oil (RSO) to biodiesel using alumina (Al 2 O 3) impregnated on calcined eggshells (Al 2 O 3 /calcined eggshells) were studied in the present work. Parameters were optimized using response surface methodology (RSM) and artificial neural network (ANN). A conversion of 98.9% was observed for RSO at optimum conditions of 12:1 methanol: oil molar ratio, 3 (wt%) catalyst concentration and 4 (h) of reaction time. A significant quadratic model with molar ratio as the most influencing process parameter and a coefficient of determination, R 2 , of value equal to 0.9379 is observed from RSM analysis. Best validation performance of 5.8595 at epoch-1 and R 2 value equal to 0.9740 was observed from ANN modeling. On comparing RSM and ANN models, it is concluded that ANN is a better tool for predicting the conversion of RSO to biodiesel with minimum error.

Biodiesel production from rubber seed oil using calcined eggshells impregnated with Al2O3 as heterogeneous catalyst: A comparative study of RSM and ANN optimization

Article

Feb 2020

Experimental parameters influencing the transesterification of rubber seed oil (RSO) to biodiesel using alumina (Al2O3) impregnated on calcined eggshells (Al2O3/calcined eggshells) were studied in the present work. Parameters were optimized using response surface methodology (RSM) and artificial neural network (ANN). A conversion of 98.9% was observed for RSO at optimum conditions of 12:1 methanol: oil molar ratio, 3 (wt%) catalyst concentration and 4 (h) of reaction time. A significant quadratic model with molar ratio as the most influencing process parameter and a coefficient of determination, R2, of value equal to 0.9379 is observed from RSM analysis. Best validation performance of 5.8595 at epoch-1 and R2 value equal to 0.9740 was observed from ANN modeling. On comparing RSM and ANN models, it is concluded that ANN is a better tool for predicting the conversion of RSO to biodiesel with minimum error.

Energy Sources, Part A: Recovery, Utilization, and Environmental Effects Optimization and modeling of biodiesel production using fluorite as a heterogeneous catalyst Optimization and modeling of biodiesel production using fluorite as a heterogeneous catalyst

Article

Nov 2018

Application of a novel heterogeneous catalyst fluorite (calcined fluorspar CaF 2) in biodiesel preparation from a highly viscous non-edible rubber seed oil has been studied. Optimization of process parameters and effect of process parameters on biodiesel conversion is done using response surface methodology (RSM) with central composite design analysis. The optimum process conditions, i.e., 12:1 molar ratio (mol/mol), 4 (wt%) catalyst, and 5 h of reaction time for a conversion of 95.95% oil to biodiesel conversion were observed. A quadratic regression model to predict the conversion in terms of process parameters was obtained. Artificial neural network (ANN) with the Levenberg-Marquardt algorithm is also attempted, with the best performance of 0.80239 at epoch-3 and a mean square error of 1.24. On comparison of the coefficient of determination, R 2 , the value obtained from both RSM and ANN it is observed that the ANN model predicts conversion better than RSM, with minimum error. ARTICLE HISTORY

ENVIRONMENTAL IMPACTS ASSESSMENT OF REAL ESTATE PROJECT AT PALLABI EASTERN HOUSING AREA IN DHAKA CITY, BANGLADESH

Conference Paper

Full-text available

Nov 2022

Md. Yachin Islam

Dhaka is the capital city of Bangladesh. A lot of people migrate every day. For their survival, the housing sector is flourishing day by day. The demand impacts the supplies. A number of people are doing housing business to support the situation. Still, on the contrary, they are grabbing a lot of green fields or water bodies from private properties evacuating the owners. One of the ill examples is considered as Pallabi Eastern Housing 2nd Phase Project. The study is to find the socio-economic status of the land owners and local inhabitants who are evicted from their land for the project. According to the primary observation and information collected from different sources, approximately 350 families are relocated. Of the 45 relocated people placed under survey from the questionnaire survey by snowball sampling, it was found that most people were displaced from their original location through the involuntary procedure. The income level, housing condition, and utility facilities are worse off than before the resettlement. They are unaware of taking action against the developer for the deprivation in the land price. The study discovered different aspects that clarified how land developers exploited the local people. The four different actors, namely land developers, local musclemen, local officials, and local people, were identified who actively played various roles in this relocation procedure. A few scopes are identified to rehabilitate the victims to recover from their present situation. Government should adequately care about the reallocated people to compensate at the current rate considering the long period of suffering. There is scope for more intensive study on the topic.

Experimental Investigation of Characterization of Emissions from Waste Cooking Oil Biodiesel

Chapter

Nov 2021

This study focused on recycling used cooking oil from residential dwellings and making it a promising alternative to fossil fuel and the collected oil was converted into biodiesel and tested on a diesel engine rig. The fuel consumption of biodiesel was observed to be slightly higher compared to standard diesel due to the lower heating value of the biodiesel in addition to its higher viscosity and density. Lower emissions of CO and HC have observed in biodiesel compared to diesel whereas the CO2 emissions were almost the same for both fuels. The NOX emissions were observed to be higher as compared to diesel due to several factors like higher oxygen content in biodiesel, short ignition delay, and advances in injection and combustion of the engines.

Conversion of Karanja oil to biodiesel using modified heterogeneous base catalyst

Article

Full-text available

May 2021
ENVIRON PROG SUSTAIN

In the recent times, biodiesel production from various non‐edible oil sources has received a lot of attention. Karanja oil is chosen mainly due to its availability and low cost. It is a nitrogen fixing tree cultivated to enhance soil quality. Transesterification of Karanja oil to biodiesel using a basic solid modified heterogeneous catalyst has been discussed in the present study. Aluminum nitrate Al(NO3)3 impregnated on calcined marble (Al(NO3)3/calcined marble), prepared by wet impregnation method (25%), is used as a modified heterogeneous base catalyst. Surface morphology of the synthesized catalyst is determined using a scanning electron microscope (SEM) analyzer and the composition of various elements present in the prepared catalyst is analyzed using energy dispersive spectrometer (EDS analyzer). 67.56 (wt/wt) of calcium oxide (CaO) is observed for calcined marble and 78.19 (wt/wt %) of CaO has been noticed for impregnated catalyst (Al(NO3)3/calcined marble). A maximum biodiesel yield of 96.5% and a conversion of 97.43% was obtained at an optimum methanol:oil molar ratio of 9:1 (mol/mol), 4 (wt %) of catalyst concentration and 1.5 (h) reaction time respectively. The entire composition of formed biodiesel is determined using gas chromatography–mass spectrometry (GC–MS) analyzer and conversion of Karanja oil to biodiesel is measured using ¹H‐nuclear magnetic resonance (NMR) analyzer.

Synthesis of aluminum chloride hexahydrate/polyvinyl alcohol catalyst for biodiesel production

Article

Apr 2021

The replacement of traditional diesel fuels with an alternative energy source like biodiesel is an excellent choice to lessen the depletion of non-renewable energy source such as fossil fuels. For application of low-cost heterogeneous catalyst for generation of biodiesel, most of waste-based catalysts are derived from inexpensive CaO resources. In this research, heterogeneous catalyst aluminum chloride hexahydrate (AlCl36H2O)/PVA was synthesized from aluminum foil wastes supported by PVA. Transesterification was used to produce biodiesel from waste cooking oil (WCO). The effect of aluminum chloride hexahydrate (AlCl36H2O)/PVA catalyst towards the yield percentage of FAME was investigated using three different operating conditions. Parameters optimized in transesterification included methanol to oil ratio (6:1, 12:1 and 18:1), reaction temperature (55℃, 60℃, and 65℃), and amount of catalyst (2 wt%, 5 wt%, and 8 wt%). The findings showed that the catalyst loading of 2 wt%, methanol to oil molar ratio of 6:1, and temperature of 55℃ yielded the highest biodiesel yield from WCO. This study proves that heterogeneous catalyst aluminum chloride hexahydrate (AlCl36H2O)/PVA can replace homogeneous catalysts and to simplify the manufacturing of biodiesel, especially in the separation phase.

Process Parameter Optimization in Acid Value Minimization of Rubber Seed Oil Conversion to Biodiesel using Al2O3/Calcined Eggshells as Catalyst - RSM and ANN Studies

Article

Sep 2020

The main objective of the present work is to work on optimization of process parameters in acid value minimization of biodiesel produced from rubber seed oil (RSO) using Al2O3/Calcined Eggshells as a heterogeneous catalyst. Optimization of process parameters was performed using response surface methodology (RSM) and artificial neural network (ANN). Acid value of raw RSO is reduced from 67.6 (mg KOH/g oil) to 2.97 (mg KOH/g oil) and later it has been reduced to 0.33 (mg KOH/g oil) in the synthesized biodiesel. Form the ANOVA analysis of RSM studies, it is observed that the designed quadratic model and the parameter methanol: oil molar ratio (mol/mol) are significant. ANN model with best validation performance of 0.00065251 at epoch-2 is observed. On comparison of coefficient of regression R2 value of 0.8885 for RSM studies and 0.9939 for ANN studies it was noticed that ANN is the best fit model with minimum error.

Transesterification of Silver Fish Oil (Mene maculata) with CaO Catalyst from Chicken Egg Shells

Article

Full-text available

Jul 2019

Silver fish (Mene maculata) is a type of pelagic fish found in the Moluccas sea, this fish has a high oil content so that it is easy to extract the oil content for transesterification. The transesterification reaction of oil from silver fish oil needs a catalyst, and heterogenous catalyst is a better choice. This study was determined the fatty acid methyl ester composition of M. maculata by transesterification process using heterogeneous CaO catalyst from chicken egg shells through 3 steps i.e. oil isolation, CaO catalyst synthesis, and oil transesterification reactions. Oil isolation was carried out by soxhletation method using petroleum ether with the oil content was 13.51%. Synthesis of CaO catalyst was carried out by calcination at 1000 °C for 2 hours and then charactererized by XRD. Fish oil is transesterified using CaO catalyst in a ratio of 11% (w/v) of the mixture. Furthermore, fatty acid methyl esters obtained were analyzed using GC-MS. The results showed 6 methyl ester fatty acids as composition of transesterification products which were methyl myristic (11.85%), methyl palmitoleate (8.71%), methyl palmitic (25.13%), methyl oleic (9.49%), methyl stearic (10.04%), and methyl 5,8,11,14-eikosatetraenoate (1.96%).

Kinetics of sunflower oil methanolysis catalyzed by calcium oxide

Article

Full-text available

Sep 2009
FUEL

The methanolysis of sunflower oil was studied in the presence of CaO previously calcined at various tem- peratures and the optimal temperature for CaO calcination was determined. The sigmoidal process kinet- ics was explained by the initial triglyceride (TG) mass transfer controlled region, followed by the chemical reaction controlled region in the latter reaction period. The TG mass transfer limitation was due to the small available active specific catalyst surface, which was mainly covered by adsorbed mole- cules of methanol. In the later phase, the adsorbed methanol concentration decreased, causing the increase of both the available active specific catalyst surface and the TG mass transfer rate, and the chem- ical reaction rate become smaller than the TG mass transfer rate.

Structure de la phase cubique de l'hexacyanoferrate(III) de zinc: Zn3[Fe(CN)6]2.nH2O

Article

Full-text available

Aug 1984

Transesterification of Soybean Oil to Biodiesel with Zn/I 2 Catalyst

Article

Full-text available

Feb 2006

Zn/I2 was found to be a practical and effective catalyst for the transesterification of soybean oil with methanol. A study for optimizing the reaction conditions such as the molar ratio of methanol to oil, the reaction time and the catalyst amount, was performed. The highest conversion of 96% was obtained under the optimum conditions. Further, the effect of free fatty acids and water in the soybean oil on the catalytic activity of the catalysts was also investigated.

Biodiesel production process by homogeneous/heterogeneous catalytic system using an acid-base catalyst

Article

Jan 2010

Development of heterogeneous base catalysts for biodiesel production

Article

Jan 2009

Heterogeneous Catalysts for Biodiesel Production

Article

Jan 2008

The production of biodiesel is greatly increasing due to its enviromental benefits. However, production costs are still rather high, compared to petroleum-based diesel fuel. The introduction of a solid heterogeneous catalyst in biodiesel production could reduce its price, becoming competitive with diesel also from a financial point of view. Therefore, great research efforts have been underway recently to find the right catalysts. This paper will be concerned with reviewing acid and basic heterogeneous catalyst performances for biodiesel production, examining both scientific and patent literature.

Use of anhydrous sodium molybdate as an efficient heterogeneous catalyst for soybean oil methanolysis

Article

Dec 2008
APPL CATAL A-GEN

Sodium molybdate (Na2MoO4) has been synthesized and investigated as a heterogeneous catalyst for the methanolysis of different types of renewable lipid sources derived from the soybean oil. Transesterification reactions occurred under relatively mild conditions, requiring low temperatures, short times and normal pressure. The methyl esters synthesized were characterized by reverse-phase and size-exclusion chromatography and hydrogen-nuclear magnetic resonance spectroscopy. The catalyst was characterized by X-ray diffraction, thermogravimetric analysis, and Fourier transform infrared spectroscopy (FTIR). It is very efficient for the transesterification reaction of triglycerides with methanol, with yields higher than 95% of methyl esters. The molybdenum(VI)-complex has a high Lewis acidity and most certainly act on alcohol O–H bond leading to a transient species which has high nucleophilic character. The catalyst was easily recovered and after being washed showed capacity of recyclability for another catalytic reaction with similar activity.

Increasing stability and productivity of lipase enzyme by encapsulation in a porous organic-inorganic system

Article

Feb 2009
MICROPOR MESOPOR MAT

In this work, we report the encapsulation of lipase enzyme in highly ordered mesoporous matrix by a sol–gel method that involves the hydrolysis/polycondensation of a silica precursor at neutral pH and room temperature. The enzyme is encapsulated within the micellar phase of the surfactant that is self-assembled with silica. The encapsulated biocatalyst has been used for the transesterification reaction of triolein with methanol under solvent free conditions. The highest fatty acid methyl esters yield (77%) was obtained after 96h at 40°C, with triolein:methanol molar ratio equal to 1:3 and with a very low amount of enzyme. Total productivity of the immobilized enzyme is almost six times higher than the one obtained using free lipase. The results clearly indicate that the immobilization procedure of lipase preserves the mobility of the enzyme and allows to increase its stability.

Esterification and transesterification on tungstated zirconia: Effect of calcination temperature

Article

Apr 2007

As part of ongoing efforts to investigate heterogeneous catalysts for biodiesel synthesis, the catalytic activity of the strong solid acid tungstated zirconia (WZ) was studied for the esterification of acetic acid (in both the gas and liquid phase) and the transesterification of triacetin (a synthetic triglyceride in the liquid phase) with methanol. Acetic acid and triacetin were used as model compounds for free fatty acids (FFAs) and triglycerides, respectively. Complex mixtures of FFAs and triglycerides are typical biodiesel precursors found in unrefined vegetable oils, animal fats, and waste greases. The effect of calcination temperature (400–900 °C) on the catalytic properties of WZ was investigated with the goal of determining the optimum pretreatment temperature and increasing the understanding of the nature of the active sites for esterification and transesterification. Catalyst characterization by powder X-ray diffraction, Raman spectroscopy, TGA, elemental analysis, and total BET surface area allowed us to correlate the changes in catalyst physicochemical properties with calcination temperature. Ion-exchange/titration and NH3-TPD were used to characterize the number and strength of the acid sites. Esterification and transesterification rates (on a catalyst weight basis) increased with increasing surface WOx densities between 1.9 and 6.6 W-atoms nm−2 and then decreased for densities above 6.6 W-atoms nm−2. The growth of WO3 crystalline species resulted in lower esterification and transesterification rates, consistent with a decrease in the number of active sites. For the catalyst that exhibited the optimum catalytic activity (calcined at 800 °C), selective poisoning of the potential catalytic centers revealed that Brønsted sites play the major role in carrying out these reactions.

Synthesis of biodiesel from soybean oil and methanol catalyzed by zeolite beta modified with La3+

Article

Dec 2007
CATAL COMMUN

La/zeolite beta was prepared by an ion exchange method and used to synthesize the biodiesel (fatty acid methyl esters, FAME). The La(NO3)3 was applied as the ion exchange precursor to incorporate La ion into zeolite beta. The composition of the zeolite beta before and after ion exchange was analyzed by the SEM microphotographs and EDS spectrograms, the Brønsted and Lewis acid sites were investigated by FTIR imaging. The transesterification was carried out in a batch reactor and the composition of the FAME product was determined by a potassium hydroxide saponification method. The syntheses conditions with respect to catalytic activities have been optimized individually. Results of the experiment showed that La/zeolite beta shows higher conversion and stability than zeolite beta for the production of biodiesel, which may be correlated to the higher quantity of external Brønsted acid sites available for the reactants. The product consists of a mixture of monoalkyl esters primarily, and when the methanol/ soybean oil molar ratio was 14.5, reaction temperature at 333K, reaction time 4h and catalyst/soybean oil mass ratio of 0.011, the conversion of triglyceride 48.9wt% was obtained from this optimal reaction condition.

Biodiesel production using heterogeneous catalysts

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