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Radioisotopic investigation of the oleic acid-1-14C HDO reaction pathways on sulfided Mo/P/Al2O3 and NiW/Al2O3 catalysts
Abstract
Oleic acid labeled with radioactive carbon at the carboxyl group (oleic acid-1-14C) has been applied to follow the hydrotreating process (reactions) of this compound over Mo/P/Al2O3 and NiW/Al2O3 catalysts, treated with H2S. The aim of the present study was to expose the transformation of the carboxyl group, including its splitting from the oleic acid, on two catalysts of substantially different chemical content.
A flow-system catalytic reactor equipped with a special unit for microanalysis was applied for the study of the decarboxylation, decarbonylation and hydrodeoxygenation reactions at atmospheric pressure in the stream of hydrogen gas of different rates in the temperature range of 573–673 K. The gas products contained only 14CO, 14CO2 and 14CH4. One of the alkanes among the products formed in the hydrodeoxygenation process (C18H38) was also radioactive. No radioactive products were detected among the alkanes with carbon number < 18. The ratio of ∑C1 formation the ∑14C1products from the oleic acid conversion was lower, than that of the C17H3514CH3 produced. This is explained by the higher energy barrier, i.e. activation energy value, required for the dissociation of the Csingle bondC bond on the catalysts–being an inevitable condition of the formation of 14C1-products–than that of the 14Csingle bondO bond dissociation on these catalysts, required for the transformation of 14COOH + 1/2H2→14CO2 + H2O.
It is stated that at the applied conditions, only small amounts of sulfur leave the 35S-labeled sulfided catalyst samples, consequently the sulfur loss of the samples can influence the catalytic behavior of these samples only after a longer period.
The experiments serve for a general conclusion: the radioactive microanalytical method based on the application of oleic acid-1-14C, is suitable for testing and evaluation of new catalyst samples in hydrotreating process of natural triglycerides.
... Recently, the HDO reaction mechanism was investigated using oleic acid labeled with radioactive carbon at the carboxyl group as the FA over Mo/P/Al 2 O 3 and NiW/ Al 2 O 3 catalysts [33]. However, few attempts were made in the past to develop a suitable kinetic model for the HDO of vegetable oils and TGs. ...
... These reactions are thermodynamically favorable under the experimental conditions. The CO, CO 2 , and CH 4 were observed as the radioactive during HDO of oleic acid labeled with radioactive carbon at the carboxyl group [33]. This result is in agreement with the proposed reaction mechanism. ...
The present work provides a systematic study to delineate the reaction mechanism and develop a mechanistic kinetic model for the hydrodeoxygenation (HDO) of triglycerides (TG) over alumina supported nickel catalyst. The HDO of 1:2 molar mixtures of tripalmitin and tristearin was studied in a batch reactor over a wide range of process conditions. The results showed that TG instantaneously converted to respective fatty acids. The fatty acids further converted to the fatty aldehydes. The fatty aldehydes, then, rapidly converted to alkanes by two parallel reaction pathways. The decarbonylation of fatty aldehyde (RP-I) was the dominating route compared to the reduction of the fatty aldehyde to fatty alcohol followed by its dehydration and hydrogenation (RP-II). A mechanistic kinetic model was developed based on the observed reaction pathway to correlate the experimental
results. The rate constants for the conversion of palmitic acid and stearic acid to alkanes were matched closely with each other thereby demonstrating that HDO is independent of fatty acid chain length. The developed kinetic model was further validated using experimental data at various hydrogen-to-nitrogen mole ratios in the
gas phase. Furthermore, the rate constants obtained for various catalyst loadings were correlated by a linear equation with zero intercept.
... The derivable products were mostly long chain hydrocarbons in the diesel and jet fuels range. Fatty acids commonly found in the algae oils include oleic, stearic, abietic and A. Galadima et al. linoleic acids [127][128][129][130]. All of these compounds were long chain carbon derivatives with compatibilities to produce diesel range products following the HDO process. ...
Sequel to the future challenges identified in the energy indicators, the exploration of algae-biomass resources increasingly becoming an issue of interest. Algae-derived oils are accordingly considered as alternative fuels with great future prospects. However, their direct utilization is scientifically difficult due to associated complex compositions. So far, hydrodeoxygenation (HDO) of the oils is increasingly viewed as the reliable upgrading process for deriving high quality fuels. The paper therefore explored and critically examined substantial literature on the updates related to catalyst design and testing for HDO, the influence of oil production techniques on its susceptibility to HDO, effects of parameters such as catalyst sulfidation, modification to phosphides, nature of support systems and preparation versus reaction conditions. In addition to highlights on reaction mechanisms, the paper also discussed the effect of hydrothermal treatment on HDO catalyst stability and provided insights into areas for further investigations.
... [102] at 320 -380 o C, 40 -70 bar with H2/oleic acid ratio of 600 Nm 3 /m 3 and by Szarvas et al. [103] using phosphorus impregnation at 300 -400 o C and 1 bar. Sousa et al. [99] investigated DO of palmist fat using Pd/C catalyst at 300 o C and 10 bar for 5 h, resulting in 96% conversion where 5% is produced bio-jet fuel [99]. ...
Worldwide consumption of energy produced from fossil fuel is forecasted to grow. This trend leads to both environmental pollution and the depletion of fossil fuel resources. Green diesel is a suitable candidate to substitute petroleum based-diesel due to its plentiful raw materials, non-polluting production process, and cost-effectiveness. Green diesel production is stated as simple, efficient, and relatively clean process. Deoxygenation (DO) is crowned as the best available technology to produce green diesel from palm fatty acid distillate (a side product of palm oil production) and other oils using heterogeneous catalysts such as zeolites. The capability of catalysts can be improved by optimizing operating parameters, treating and modifying catalysts and with the use of nano-sized catalytic materials. These activities contribute to stronger and more active Bronsted-Lewis acid-base sites and enlarged crystallite sizes, which improve the DO efficiency, selectivity, and reusability, to produce high-grade green diesel with less oxygen content.
... At the beginning of the oleic acid conversion reaction a strong increase in the concentration of stearic acid is observed, which is attributed to the saturation by H 2 of the double bond (-C = C-) of the oleic acid (Szarvas et al. 2015;Mäki-Arvela et al. 2007). Subsequently, with the increase in the concentration of C 17 n-alkanes as the main product and the appearance in low concentration of n-C 18 , the concentration of stearic acid gradually decreased. ...
Renewable biodiesel with a high content of n-C 17 alkanes was prepared through the catalytic hydrodeoxygenation of oleic acid under optimum conditions of temperature, reaction time and weight percentage of Ni deposited in γ-Al 2 O 3 . The hydrotreated vegetable oil (HVO) was blended with petrodiesel (20 % and 40 % of HVO) to evaluate its behaviour in a diesel engine. Comparative studies of power and emission of atmospheric pollutants such as NO x , CO, HC and smoke were evaluated under prepared blends and petrodiesel. The presence of HVO biodiesel at full load generated a slight decrease in power compared to petrodiesel; however, the decrease in emission of pollutants when using the blends containing HVO was significant. In the case of 40 % HVO were able to reduce more of 20 % of CO and HC emissions, and more than 40 % reduction in smoke when compared with petrodiesel. The NO x emissions of the blends with HVO had a significant slightly decrease. Further, the properties of Ni/γ-Al 2 O 3 catalysts are justified by the results of EDS characterization, surface area (SBET), XRD, XPS, HR-TEM and it’s capacity to produce biodiesel.
... Two main treatments may be carried out for bio-oils upgrading: cracking or hydrodeoxygenation (HDO) reactions [11,12]. Since cracking processes usually produce high amounts of undesired coke [11,12], in the last few years HDO reactions have attracted much attention as more efficient and sustainable processes offering a suitable means to convert oxygenrich bio-oils to hydrocarbons and other compounds of interest [9,[13][14][15]. ...
The hydrodeoxygenation (HDO) of guaiacol is a model reaction for the upgrading of the lignin component of bio-oils, in the framework of the production of fuels from the most abundant and renewable biomass source. While Ni-based catalysts are now widely recognized as suitable catalysts for this reaction, the role of the catalyst support is far less investigated. In this work, Ni-based catalysts for the HDO reaction of guaiacol were prepared using a series of alumina-silica supports characterized by a different amount of silica (0–40%). A wide range of metal contents (0–45%) was also investigated. The reaction was performed in H2 at 50 bar and 300 °C, determining conversion, product distribution and HDO degree. Besides a notable role played by the Ni amount, the catalyst performance is markedly affected by the morphological and surface features of the support. The measured isoelectric point of the bare supports appeared to be predictive of the final performance of the relative Ni-based catalyst: the more acidic the isoelectric point, the better the overall performance of the catalyst. A regeneration treatment in mild conditions was developed to fully restore the starting surface features of the catalysts.
... However, noble metal-based catalysts could significantly raise the cost of deoxygenation processing [39]. Other approaches involve the use of bimetallic Al 2 O 3supported catalysts in sulfide forms (NiMoS/Al 2 O 3 and CoMoS/Al 2 O 3 ) for deoxygenation reactions [40][41][42]. However, they have many drawbacks, such as rapid deactivation by coke deposition and a need for the addition of sulfur donor compounds (H 2 S, low sulfur content in bio-feedstock) [29,43]. ...
Support- and sulfide-free cobalt molybdenum catalysts are prepared via different synthetic procedures for catalytic deoxygenation of oleic acid under inert (N2) and solvent-free conditions. Among the tested catalysts, the CoMo catalyst prepared via a sol-gel method achieves the highest catalytic performance, namely, 88.9% oleic acid conversion, with 48.1% C9–C17 selectivity, and 69.6% oxygen removal rate, owing to its excellent physical properties. Additionally, oxygen vacancy is formed in CoMo catalyst during sol-gel synthesis process and it also effect on the catalytic activity. Examination of the deoxygenation reaction over pre-reduced catalysts reveals that the CoMoO4 species is the active species in the CoMo catalysts. The fuel properties of the resultant products are affected strongly by the catalytic performances of the CoMo catalysts. The biofuel produced using the CoMo catalyst prepared via the sol-gel method showed the highest calorific value (10,119 cal/g) and the lowest viscosity (31.5 cP), and, consequently, this CoMo catalyst exhibits the highest catalytic activity and has significant potential for application in biofuel production.
... Recently, the hydrodeoxygenation (HDO) process has been industrialized to form diesel fuel from vegetable oils. Hydrodeoxygenation of triglycerides at higher temperatures using a heterogeneous catalyst produces long-chain saturated hydrocarbons from C4 to C24, typically, C16 to C18 (Szarvas et al., 2015). Development of sulfur-free and without a supported catalyst was the new access for conversion of renewable sources into paraffinic liquid fuel. ...
Mesoporous nickel stabilized with silica species was used as magnetically separable hydodeoxygenation catalyst, to convert glyceride model compound (stearin) to diesel fuel, as an alternative to environmentally hazardous sulphided catalysts. The catalyst was synthesised by hydrothermal method using an organosilane as a source of Si to stabilize the Ni structure as well as to create mesopores. The catalyst was characterized by nitrogen sorption, XRD, TEM, H2 chemisorption, XPS, NH3-TPD and TPR. The material has high surface area (205 m2/g), small nanocrystallite size (5.4 nm, by XRD; 7 nm by H2 chemisorption) and 20% metal dispersion. The acidity of the catalyst was measured to be 0.28 mmol/g. Catalyst life and activity was measured in fixed-bed reactor. Nearly complete glyceride conversion (100%) and 88% selectivity for C10-C17 hydrocarbons has been achieved at 350 °C. The conversion and yield of diesel increased with increase in temperature from 325 °C to 350 °C.
... The main reaction pathways were hydrodeoxygenation (producted n-C 18 and n-C 16 ) and decarbonylation (producted n-C 17 and n-C 15 ) and the ratio of these two pathways (hydrodeoxygenation/decarboxylation) based on product ratio (n-C 18 /n-C 17 ) was about 1.3 under catalyst HC-5. The reaction pathways of oleic acid over sulfided Mo/P/Al 2 O 3 and NiW/Al 2 O 3 catalysts were also studied by Szarvas et al. [39] and the experimental results indicated that both catalysts were active in hydrodeoxygenation. ...
Inedible camelina oil (CSO) contains fatty acids with a high degree of unsaturation (1.8 double bonds per fatty acid on average). CSO was hydrotreated at temperatures 340–370 °C, pressures of 15–50 bar, and liquid hour space velocities (LHSVs) of 0.8–1.1 h⁻¹ for the production of hydrocarbons that are usable as diesel components. First, hydrotreating pure CSO at 340–370 oC and low hydrogen pressures of 15–25 bar led to the formation of a mixture of n-/iso- alkanes, aromatics, and higher olefins. The presence of C=C double bonds in the CSO molecule affected the progress of the side reactions and caused rapid deactivation and coking of the catalyst, especially at low hydrogen partial pressure. Hydrotreatment co-processing of polyunsaturated CSO and partially hydrogenated CSO was then done with two different gas oils or two paraffinic solvents in the range of concentration 5–20%. Co-hydrotreatment took place in a bench-scale trickle-bed reactor using commercial NiMoP/γ-Al2O3 catalysts (catalysts A and B) and a prepared catalyst, NiMoCuP/ZrO2-γ-Al2O3 (catalyst C). High triacylglyceride conversion to hydrocarbons was achieved when CSO was hydrogenated in a mixture with paraffinic solvents on NiMoP/γ-Al2O3 catalysts at hydrogen partial pressures above 30 bar and temperatures above 350 oC. CSO decarboxylation/decarbonylation reactions prevailed over hydrodeoxygenation. Hydrodeoxygenation (72%) was predominant for catalyst C with significant methanation of CO and CO2. There was a complete TAG conversion into hydrocarbons when co-processing a mixture of CSO and atmospheric gas oil at a temperature of 360 oC, LHSV of 0.8 h⁻¹, a hydrogen pressure of 50 bar, and various ratios of hydrogen to raw material from 312 to 656 NL.L⁻¹. The deoxygenation activity decreased in the order of catalysts C>B>A. Increasing the ratio of H2 to feed had a positive effect on the composition and properties of the liquid product. During experiments with catalyst C at 50 bar, 370°C, and ratios of hydrogen to raw material of 293–656 NL.L⁻¹, the cetane index increased from 46 to 58, and the polyaromatic content decreased from 12.5 to 4.4 wt.%. The sulphur and nitrogen contents of the product (29.5 mg.kg⁻¹ and 13.2 mg.g⁻¹) were higher than expected. In the case of catalyst C, the degree of desulphurization was lower than that of catalysts A and B.
Hydrodesulfurization of thiophene has been studied over alumina supported sulfided molybdena, nickel-promoted molybdena and over nickel (Mo, NiMo and Ni) catalysts. The experiments were carried out with a mixture of thiophene, labeled with radioactive carbon (thiophene-[G-]-14C) and of non-radioactive tetrahydrothiophene (1:1 mol ratio) in a micro catalytic system. It was established, that the main products were tetrahydrothiophene-14C, 1-butene-14C, 2-butene-14C, butane-14C. Tetrahydrothiophene-14C was a major intermediate in the conversion of thiophene—14C in the experimental condition applied. The amounts of converted tetrahydrothiophene on the catalysts were substantially higher than those of thiophene under the same conditions. Hydrothiophene and dihydrothiophene—14C were intermediate products in the hydrodesulfurization of thiophene and tetrahydrothiophene. The hydrodesulphurization of tetrahydrothiophene was paired with dehydrogenation, producing small amounts of thiophene. The experimental results have been considered in the discussion of the mechanism of thiophene and tetrahydrothiophene desulfurization reaction pathway.
The influence of adding manganese to an Al2O3 support for preparing NiMo catalysts for the hydroconversion of soybean oil was herein evaluated. Two different Mn contents (1 and 5 mol % Mn) were used while Al2O3-Mnx (x = 1 or 5 % mol Mn) were obtained by sol-gel method. The NiMo catalysts were obtained by wetness co-impregnation of nickel and molybdenum precursors onto the as-formed supports considering two different pH of impregnation (5 or 9). Solids were then characterized at the oxide state at different stages of preparation before being sulfide at 400 °C for 4 h with 10% H2S/H2. Catalysts were then characterized at the sulfide state and evaluated for the hydroconversion of new and waste soybean oil at 380 °C, PH2 = 40 bars. Results show clearly the superiority of NiMo catalysts supported on Al2O3 with 1% mol Mn for the hydroconversion of new and waste soybean oil due to the stabilization of manganese oxide species on the alumina support helping to redisperse the Ni-promoted MoS2 active phase. This study shows that through a precise control of the addition of manganese to Al2O3, it is possible to obtain very highly active NiMo catalysts for the hydroconversion of vegetable oils.
Due to increasing air transportation the demand for jet fuels grew significantly in the last decade. Hydrocarbon processing companies and different research groups began investigating the possible production routes of suitable kerosene fractions in order to produce fuel for jet engines not only on crude oil base, but from alternative sources, too. The Carbon Offset and Reduction Scheme for International Aviation program will be started in the near future with the target to decrease the carbon dioxide emission of the aviation significantly. This carbon dioxide reduction can only be achieved with using jet fuels derived from alternative sources. The aim of experimental work was to study the catalytic conversion of waste coconut oil which was mixed in straight-run kerosene fractions in 10, 30, and 50 % to produce alternative component containing jet fuel at various process parameters (temperature = 280 – 360 °C, liquid hourly space velocity = 1.0 – 3.0 h-1, pressure = 30 bar, hydrogen/feedstock volume ratio = 600 Nm3/m3) on a sulfided nickel molybdenum/alumina catalyst. Based on the experimental results, the yield of the target product changed between 65 – 95 % depending on the rate of desulfurization, deoxygenation and aromatic saturation. The target products had very high smoke point (>40 mm) resulting very low particle emission during the use of this biojet fuel.
Predicting the hydrotreating performance of industrial catalysts used for upgrading heavy oils is hampered by the unknown chemistry behind it. In this work, we have used a set of chromatographic and mass spectrometric techniques (APPI/ESI FT-ICR MS, FID-MS GC × GC and PFPD GC) for acquiring a more precise composition of the feed and products of the hydrotreatment of a blend of light cycle oil and scrap tire oil (20 vol%) using three benchmark catalysts: CoMo/Al2O3, NiMo/SiO2-Al2O3 and NiW/USY zeolite. Despite the different nature of the catalysts, the composition of the products was relatively similar, indicating the slower and controlled transformation of the heaviest molecules of the feed, particularly in tire oil. A faithful analysis of these molecules by combining the results of the analysis clarifies the multiple mechanisms affecting hydrotreating simultaneously: hydrodearomatization, hydrocracking, hydrodesulfurization, hydrodeoxygenation and hydrodenitrification. An effort has been made to use these results in a quantitative manner for catalyst screening.
In this study, the deoxygenation of oleic acid under a N2 atmosphere over metal oxide catalysts is investigated for the production of green diesel hydrocarbons. The molybdenum oxide catalysts with promoters (Ni, Co, and Cu) and varying catalyst loadings (19–34 wt%) on γ-Al2O3 support are prepared by an incipient wetness impregnation method and characterized by XRD, FE-SEM/EDX, TEM, XPS, and N2 sorption. The catalytic testing is carried out in a batch reactor with various reaction times (3–9 h) and temperatures (300–350 °C) under N2 pressure (10 and 40 bar). The NiMo oxide/γ-Al2O3 exhibits the highest performance with over 80% conversion and good selectivity toward C17 hydrocarbon products. The catalytic performance of the NiMo oxide/γ-Al2O3 remains stable during 4 reaction cycles. Decarboxylation (DCO2) and decarbonylation (DCO) are observed to be the reaction pathways of the deoxygenation and these reactions are enhanced by increasing reaction temperature and time. Stearic acid and other hydrogenated compounds were produced via the in situ hydrogenation which was proposed as a competitive reaction in the deoxygenation of oleic acid under the N2 pressure. The DFT calculations confirm that the dehydrogenation and hydrogenation reactions could occur on the MoO3 surface. These processes are responsible for the in situ formation of hydrogen species, leading to the formation of hydrogenated products. Hydroxyl groups on the terminal oxygen sites created by dehydrogenation could contribute to the surface vacancy and further promote the DCO2 or DCO pathway. The molybdenum oxide-based catalysts show a great potential for green diesel production without the use of H2 feed.
The Al2O3 supported monometallic Co, Ni and Mo and bimetallic CoMo and NiMo catalysts were compared in rapeseed oil hydrodeoxygenation (HDO) reaction after in situ sulfidation. The reaction was described by five pseudo-first order rate constants (k1–k5) for the simplified reaction scheme: triglycerides (Tgs) to octadecane (k1); Tgs to oxygenates (Oxs; i.e., sum of fatty acids, fatty alcohols, and esters of fatty acids and fatty alcohols) (k2); Tgs to heptadecane (k3); Oxs to octadecane (k4), and Oxs to heptadecane (k5). The empirical pseudo-first order rate constant of the hydrocarbons (Hcs) product formation (kHc) increased in the order Ni/Al2O3 ~ Co/Al2O3 < CoMo/Al2O3 ~ Mo/Al2O3 ≪ NiMo/Al2O3 showing hence a significant synergy between Ni and Mo. All monometallic catalysts exhibited k1 and k3 practically zero and the reaction proceeded essentially through the formation of the oxygenated reaction intermediates (high k2). The Co/Al2O3 and Ni/Al2O3 catalyzed selectively hydrodecarboxylation (HDC) of fatty acids (high k5). Over Mo/Al2O3, the HDO pathway, however, was nearly the exclusive one (high k4). CoMo/Al2O3 and NiMo/Al2O3 catalysts yielded both HDO and HDC products suggesting partial synergy in the relative selectivity HDO/HDC between Co(Ni) and Mo.
Nickel based metal organic frameworks (Ni-MOFs) were successfully synthesized using new conjugated carboxylic acid linkers. These conjugated carboxylic acid linkers were synthesized using mild Heck coupling that led to the incorporation of functional groups not possible by traditional synthetic methods. Control of linker size allows for porosity tuning of the crystalline network and high surface area, that, in theory, results in the increased accessibility to Ni metal centers for catalysis. The resultant crystalline Ni-MOFs displayed BET surface areas as high as ∼314 m2/g. To investigate their catalytic activity for conversion of oleic acid to liquid hydrocarbons, Ni-MOFs were grown on zeolite 5A beads that served as catalytic supports. The resultant catalysts displayed heptadecane yields as high as ∼77% at mild reaction conditions, one of the highest yields for non-noble metal containing catalysts. The catalytic activity correlated to the concentration of acid sites. A slight decrease in catalytic activity was observed after catalysts recycling.
Alumina supported NiMo catalysts were synthesized. The prepared NiMo catalysts were activated by DMDS in a sulfidation process and characterized. The sulfided NiMo catalysts were next used in hydrodeoxygenation (HDO) of oleic acid in a batch reactor. Afterwards, the NiMo catalyst were recovered and used in another set of HDO reactions of oleic acid under the same conditions used in the previous HDO reactions. After the HDO experiments, the active phase and deposited coke on spent catalysts were characterized. The results indicated that higher concentrations of DMDS promoted the production of heptadecane (C17) but had no effect on the production of octadecane (C18). Moreover, the XPS results revealed the promotional effect of DMDS concentration on maintenance of the sulfidity of the catalysts. In addition, the results for the experiments with the second run catalyst revealed a clear deactivation due to increased coke depositions. Furthermore, after two repeated experiments with first run and second run catalysts, it was observed that coke formation decreased when the concentration of DMDS was increased. These results clearly indicate a correlation between the concentration of DMDS and coke formation.
We studied hydrodeoxygenation of model compounds for vegetable oil into diesel-range hydrocarbons on a sulfided NiMo/γ-Al2O3 catalyst under trickle-flow conditions. Methyl oleate (methyl ester of oleic acid, a C18 fatty acid with one unsaturated bond in the chain) represented the C18 alkyl esters in natural fats, oils and greases. The effect of temperature and pressure on activity and product distribution (mainly C17 and C18 hydrocarbons) were studied. Hydrolysis of the methyl ester results in fatty acid intermediates, which are converted by direct hydrodeoxygenation to C18 hydrocarbons or decarbonated (by decarbonylation or decarboxylation) to C17 hydrocarbons. Reactant inhibition is more pronounced for the former route. The reaction is hardly inhibited by H2S, H2O, CO and tetralin solvent. H2S and to a lesser extent H2O increase the C17/C18 hydrocarbon ratio, because they inhibit direct hydrodeoxygenation more than decarbonation. The catalyst surface contains different sites for direct hydrodeoxygenation and decarbonation reactions. During methyl oleate HDO, the catalyst slowly deactivated, mainly due to blocking of Lewis acid sites of the alumina support that catalyze methyl oleate hydrolysis. The catalyst was much more active in the HDO of triolein (glyceryl trioleate, representative triglyceride model compound) than in methyl oleate HDO, to be attributed to very facile hydrolysis of triglycerides. Although the overall kinetics of methyl oleate and triolein HDO were similar, our results show that the catalyst and H2S play a much more important role in the hydrolysis of methyl oleate than in hydrolysis of triglycerides.
We herein report an atom-economic approach to produce aviation fuel range hydrocarbons and aromatics from oleic acid without an added hydrogen donor. The effects of catalyst loading, reactant loading, and reaction temperature on the conversion of oleic acid and the yields of hydrocarbons and aromatics were investigated. The conversion of oleic acid was 100%, and the yield of heptadecane (the main product) can reach 71% after 80 min at 350 °C. Moreover, an aromatics yield of 19% was determined, which is the critical composition of the aviation fuels due to their ability to maintain the swelling of fuel system elastomers, indicating that it is a complicated reaction system including in-situ hydrogen transfer, aromatization, decarboxylation and cracking. To probe the mechanism of the conversion of oleic acid without an added hydrogen donor, variations of the reactant and products as time elapsed at different temperatures and the reaction behavior of 1-heptadecene at 350 °C in the catalysis system were investigated. The main mechanism proposed was that oleic acid was decarboxylated to 8-heptadecene, followed by the dehydrogenation of 8-heptadecene to polyenes. Then, polyenes were cyclized to aromatics by an intramolecular Dials-Alder reaction, which provided hydrogen to hydrogenate the unreacted oleic acid to stearic acid. Finally, stearic acid was decarboxylated to heptadecane.
Intrinsic kinetics, diffusivity, energy calculations and reaction mechanism studies for the conversion of plant-oil triglycerides over Ni-W/SiO2-Al2O3 hydrocracking catalyst is reported. Specific insights into reaction mechanisms, are established using kinetic modeling and validated with experimental results. Diffusion studies and effectiveness factor calculations established diffusion–free intrinsic kinetics, with an activation energy of 115 kJ/mole required for triglycerides conversion. Thermodynamic calculations further established that the heat released during propane removal step (1.15 MJ/kg) was 8-times higher than that for hydrodeoxygenation step (0.14 MJ/kg) and lowest for hydrocracking reactions (0.08 MJ/kg). Such high exothermicity resulted in high temperature gradient across the catalyst bed (370 °C above the reaction temperature).
In the light of general evaluation of the radioisotopic data obtained during the years of our research two possible ways of sulfur transfer from the catalyst into H2S in the course of thiophene HDS have been reconsidered. These are (i) sulfur exchange between H2S formed and the catalyst sulfur and (ii) extrusion of sulfide sulfur into the gas phase by the interaction of the catalyst SH group with H2 with the further formation of H2S. The data of our radioisotopic studies supports the second way, which proceeds within the “forcing out” mechanism. This mechanism assumes either of the two possible schemes of H2S formation—(a) H2 interaction with the catalyst bridge sulfur and (b) H2 interaction with the SH group. The radioisotopic studies support the second possibility.
The production of gas oil blending components which a new application of the Pt/SAPO-11 is introduced, while the effect of
oxygenic compounds on the isomerization of paraffin mixtures is highlighted. The experiments were carried out on 0.5% Pt/SAPO-11
catalyst at 300–380°C, 30–80bar, liquid hourly space velocity=0.75–2.0h−1 and H2/hydrocarbon ratio=400Nm3/m3, while 0.25–5.0% oleic acid was added to the feedstock. At the favourable operational parameters the isoparaffins concentration
of the products (cetane number: 78–86, cold filter plugging point: between −19 and −10°C) reached 65–72%, if the oleic acid
content of the feedstock was lower than 0.5%. These isomer contents were significantly decreased by increasing the oleic acid
content of the feedstock.
KeywordsBio gas oil–Green diesel–Isomerization–Oxygenic compounds–Oleic acid
The deoxygenation of methyl octanoate and methyl stearate over alumina-supported Pt was studied in both the vapor phase in
a flow reactor and in the liquid phase in a semibatch reactor. The conversion of both methyl esters resulted in hydrocarbons
with one carbon less than the fatty acid of the corresponding ester as the dominant products. In the vapor phase, acid and
other oxygenates were observed in low concentrations, but they were not detected when the reaction was conducted in the liquid
phase. Under He, condensation products (from esterification and ketonization) were observed. By contrast, under H2, mostly paraffins were obtained. These results show promise to directly produce standard diesel components from biodiesel.
The direct catalytic conversion of vegetable oils into hydrocarbons that can be used as components for diesel fuel blending was studied. Complete conversion of rapeseed oil was obtained over both types of catalysts (hydrogenation and hydrotreating catalysts) at over 300°C. The main liquid- phase products were long-chain hydrocarbons (C15-C18) and water. Saturated fatty acids and saturated triglycerides were the reaction intermediates that were converted into hydrocarbons at over 300°C. The gas-phase products consisted mainly of methane, CO, CO2 and propane. Analysis of the NiMo catalyst revealed that the extent of the identified reaction pathways and, consequently, the product distribution were affected by the catalyst choice and by reaction conditions. HDO was favored by NiMo catalyst, lower reaction temperature and higher hydrogen pressure. On the other hand, the extent of HDCO increased with increasing reaction temperature and decreasing hydrogen pressure.
A new field of the catalytic application of Pt/HZSM-22/Al2O3 catalysts for the isomerization of pre-hydrogenated sunflower oils (PHSO) aiming the production of diesel fuel is presented. High cetane number blending components that are practically free of sulfur (<1 ppm) and of aromatic compounds are required for satisfying environmental and human health regulations as well as specifications of diesel fuels in the European Union (cetane number: min 51; CFPP: max −20 °C depending on the climate of the country). Experiments were carried out over catalysts containing 0.25–1.1% platinum on HZSM-22 at temperatures of 280–370 °C, total pressures of 35–80 bar; liquid hourly space velocities (LHSV) of 1.0–4.0 h−1, H2 to hydrocarbon ratios of 250–400 Nm3/m3. Results indicated that the yield of liquid products obtained under favorable process conditions was >90%, the ratio of i-/n-paraffins was in the range of 3.7:1–4.7:1, cetane numbers were 81–84 units and CFPP values were between −18 and −14 °C. These are excellent blend stocks of diesel fuels.
This chapter describes the quasi-homogeneous surfaces, flow method kinetics, experimental result on dehydrogenation, and discussion of results and the multiplet theory. The kinetics of dehydrogenation depends upon the nature of the catalyst. The catalysts used, divide sharply into two groups-metals and oxides. Experimental evidence shows that, in dehydrogenation the calculated ΔH° is practically independent of the temperature over the range of 50 or 100°. The geometry and energy aspects of the multiplet theory are useful in interpreting the kinetics of catalytic dehydrogenation and in throwing light on the nature of the active centers. The possibility was shown of the experimental determination of change in free energy, enthalpy, and entropy of adsorption on the active centers and of the bond energies between the reacting atoms of the molecule and the atoms of the active centers of the catalyst.
The deoxygenation of triolein and soybean oil under nitrogen atmosphere was investigated over Ni-Al, Ni-Mg-Al and Mg-Al layered double hydroxides, as well as 20 wt.% Ni/Al2O3. Deoxygenation was found to proceed via removal of the carboxyl group in the fatty acid structure as CO2 and CO, while additional cracking of the fatty acid chains resulted in the formation of mainly liquid (C5–C17) hydrocarbons. In comparison with triolein, the greater unsaturation of soybean oil resulted in increased cracking, leading to the formation of lighter hydrocarbons and higher amounts of coke deposits. According to 13C NMR measurements, one of the pathways for hydrocarbon formation involves a β-hydrogen elimination in the triglyceride to produce a fatty acid, the decarboxylation of which yields a linear hydrocarbon. The formation of coke was consistently observed in these reactions and was found to limit catalyst activity.
The production possibilities of gas oil boiling-range mixtures of paraffins were investigated over different catalysts as a function of the process parameters using different natural triglycerides. Under favorable operational parameters (T: 360–380 °C; p: 60–80 bar; liquid hourly space velocity (LHSV): 1.0–2.0 cm3 of feedstock/(h∙cm3 of catalyst)), the yield of paraffin mixtures increased in the order NiW/Al2O3 < NiMo/Al2O3 << CoMo/Al2O3. In the best cases, the yields of paraffins reached 75–85% of the theoretical values. These compounds are excellent, environmentally sound fuels for diesel engines (cetane number: 89–92) and could be used either as pure fuels or as blending components.
Water formed during hydrotreating of oxygen-containing feeds has been found to affect the performance of sulphided catalysts in different ways. The effect of water on the activity of sulphided NiMo/γ-Al2O3 and CoMo/γ-Al2O3 catalysts in hydrodeoxygenation (HDO) of aliphatic esters was investigated in a tubular reactor by varying the amount of water in the feed. In additional experiments, H2S was added to the feed, alone and simultaneously with water.Under the same conditions, the NiMo catalyst exhibited a higher activity than the CoMo catalyst. The ester conversions decreased with increase in the amount of added water. When H2S and water were added simultaneously, the conversion increased to the same level as without water addition on the NiMo catalyst and reached a higher value on the CoMo catalyst. The conversions were highest, however, when only H2S was added. Unfortunately, the conversions decreased with time under all conditions. On both catalysts, the total yield of the C7 and C6 hydrocarbons decreased with the amount of added water, while the concentrations of the oxygen-containing intermediates increased. The presence of H2S improved the total hydrocarbon yield and shifted the main products towards the C6 hydrocarbons. Thus, the addition of H2S effectively compensated the inhibition by water.
Promoted (CoMo/Al2O3 and NiMo/Al2O3) and unpromoted (Mo/Al2O3) catalysts were tested in the hydrodeoxygenation of 2-ethylphenol as a model compound of bio-crude under various partial pressures of H2S and CO. The catalytic tests were carried out at 340 °C under 7 MPa of total pressure in a fixed-bed microreactor. H2S, needed to maintain the sulfidation level of the catalysts, showed promoting or inhibiting effects depending on the catalyst tested and the deoxygenation pathway considered. Over the three catalysts, H2S was found to slightly promote the HYD pathway, which first involves the hydrogenation of the aromatic ring, whereas it strongly inhibited the DDO pathway, which consists of a direct C–O bond scission, particularly on the CoMo/Al2O3catalyst. In addition, a strong though reversible inhibition by CO was found over CoMo/Al2O3 for both deoxygenation pathways, while a limited effect was observed over NiMo/Al2O3. Differences in inhibition induced by H2S and CO observed over both promoted catalysts suggested that different active sites are involved in the hydrodeoxygenation of 2-ethylphenol, depending on the nature and the localisation of promoters and on the transformation pathway.
This chapter reviews the modern state of the multiplet theory of heterogeneous catalysis. The multiplet theory deals with numerical values of bond lengths and bond energies, as well as with the geometrical form of reacting molecules and the crystal lattices of catalysts. This allows definite results to be obtained for many reactions on an atomic level. This is how the multiplet theory differs from a number of other theories on catalysis. The theory of the structure of matter is based on both electronic theory and quantum mechanics—the basis for the multiplet theory. Bond lengths and energies represent a stable complex of electronic properties essential for catalysis. The multiplet theory proceeds from the premise that catalysis is a chemical phenomenon and that covalent bonds require catalytic activation.
Deoxygenation of vegetable oils has a potential to become an important process for production of biofuels. The present work focuses on investigation of Ni, Mo, and NiMo sulfided catalysts prepared by impregnation in deoxygenation of rapeseed oil at 260–280°C, 3.5MPa and 0.25–4h−1 in a fixed-bed reactor. The activity of the catalysts decreased in the order NiMo/Al2O3>Mo/Al2O3>Ni/Al2O3. The catalysts exhibited significantly different product distributions. The bimetallic NiMo catalysts showed higher yields of hydrocarbons than the monometallic catalysts at a given conversion. Apart from the various oxygenated product intermediates, NiMo/Al2O3 yielded a mixture of decarboxylation and hydrodeoxygenation hydrocarbon products while Ni/Al2O3 yielded only decarboxylation hydrocarbon products and Mo/Al2O3 yielded almost exclusively hydrodeoxygenation hydrocarbon products. The effect of Ni/(Ni+Mo) atomic ratio in the range 0.2–0.4 on the activity and selectivity was not significant.
Nitrides of molybdenum, tungsten and vanadium supported on γ-Al2O3 were prepared by temperature-programmed reaction with NH3 and tested as catalysts for hydrodeoxygenation of oleic acid and canola oil at 380–410°C and 7.15MPa H2. The molybdenum nitride catalyst was found superior to the vanadium and tungsten nitrides for catalytic hydrotreating of oleic acid in terms of fatty acid conversion, oxygen removal and production of normal alkanes (diesel fuel cetane enhancers). The supported molybdenum nitride favoured the hydrodeoxygenation of oleic acid to n-C18H38 three times out of four compared to decarbonylation and decarboxylation. A 450-h long hydrotreating test performed at 400°C and 8.35MPa H2 with Mo2N/Al2O3 and canola oil, indicated that oxygen removal exceeded 90% over the duration of the experiment and that the yield of middle distillate hydrocarbons (diesel fuel) ranged between 38 and 48wt% (based on liquid feed).
Renewable liquid alkanes can be produced by hydrotreating of vegetable oils and vegetable oil–heavy vacuum oil (HVO) mixtures at standard hydrotreating conditions (i.e. 300–450°C) with conventional hydrotreating catalysts (sulfided NiMo/Al2O3). The reaction pathway involves hydrogenation of the CC bonds of the vegetable oils followed by alkane production by three different pathways: decarbonylation, decarboxylation and hydrodeoxygenation. The straight chain alkanes can undergo isomerization and cracking to produce lighter and isomerized alkanes. The carbon molar yield of straight chain C15–C18 alkanes was 71% on a carbon basis (the maximum theoretical yield for these products is 95%) for hydrotreating of pure vegetable oil under optimal reaction conditions. The rate of alkane production from pure sunflower oil is greater than the rate of hydrodesulfurization of a HVO with a 1.48wt% sulfur content (e.g. 100% conversion of sunflower oil at 350°C compared to 41% conversion of sulfur). The yield of straight chain alkanes increases when sunflower oil is mixed with HVO, illustrating that dilution of HVO can improve the reaction chemistry. For example, with a 5wt% sunflower oil–95wt% HVO feed the maximum theoretical straight chain C15–C18 yield from the sunflower oil was higher (87%) than it was with the pure sunflower oil (75%). Mixing the sunflower oil with HVO does not decrease the rate of desulfurization indicating that sunflower oil does not inhibit the hydrotreating of HVO.
This paper deals with the hydroprocessing of rapeseed oil representing a perspective technological way for production of biocomponents in diesel fuel range. Rapeseed oil was hydroprocessed at various temperatures (260–340°C) under a pressure of 7MPa in a laboratory flow reactor. Three Ni–Mo/alumina hydrorefining catalysts were used. Reaction products were analyzed using several gas-chromatographic methods. Reaction products contained water, hydrogen-rich gas and organic liquid product (OLP). The main components of OLP were identified as C17 and C18n-alkanes and i-alkanes. At a low reaction temperature, OLP contained also free fatty acids and triglycerides. At reaction temperatures higher than 310°C, OLP contained only hydrocarbons of the same nature as hydrocarbons present in diesel fuel. Influence of reaction temperature and catalyst on the composition of reaction products is discussed.
The general case of a first-order catalytic reaction occurring during elution of a reactant through a chromatographic column is discussed. Under conditions of low reactant partial pressure and rapid adsorption relative to the rate of the surface reaction, the fractional conversion of a pulse of reactant passed through a chromatographic column is given by an equation analogous to that for the conversion under similar conditions in a steady-state flow reactor. A major advantage of the chromatographic technique is that it permits a determination of the extent of adsorption under reaction conditions, and thus of the rate constant for the reaction on the catalyst surface. The method is illustrated by a gas chromatographic study of the catalytic isomerization of cyclopropane on Linde Molecular Sieve 13X. The rate constant of the surface reaction was found to be k = 1.3 × 1010 exp(-30,000/RT) sec.-1. The heat of adsorption of cyclopropane under reaction conditions was 11.0 kcal. mole-1.
Through a combined experimental and density functional study, we investigate the deoxygenation of ethyl heptanoate catalyzed by three relevant unsupported (bulk) transition metal sulfide catalysts: MoS2, Ni3S2 and Ni-promoted MoS2 (with various Ni/Mo ratio). Two pathways compete for this reaction: hydrodeoxygenation (HDO) and decarboxylation/decarbonylation (DCO). It is shown experimentally that the presence of Ni either in the NiMoS mixed phase or in the Ni monosulfide phase may change the selectivity between the HDO and DCO pathway. To understand the origin of this selectivity, we study the deoxygenation pathways of two relevant intermediates: carboxylic acid and aldehyde. In particular, DFT calculations highlight that the aldehyde decarbonylation occurs via the formation of the alkanoyl and/or ketene intermediates obtained from the aldehyde dehydrogenation on the Ni3S2 (111) surface proposed to be the precursor steps for the DCO pathway. These reaction are found to be more favorable on Ni3S2 than on MoS2 based catalysts. This trend is explained by the presence of Ni3 triangular facets enhancing the formation of the unsaturated alkanoyl and/or ketene intermediates as well as the CO product. We finally propose a detailed analysis of the promoting effect of Ni on MoS2, when present in the NiMoS structure.
Non-edible oil contains several unsaponifiable and toxic components, which make them unsuitable for human consumption. Karanja (Pongamia pinnata) is an underutilized plant which is grown in many parts of India. Sometimes the oil is contaminated with high free fatty acids (FFAs) depending upon the moisture content in the seed during collection as well as oil expression. The present study deals with production of biodiesel from high FFA Karanja oil because the conventional alkali-catalyzed route is not the feasible route. This paper discusses the mechanism of a dual process adopted for the production of biodiesel from Karanja oil containing FFA up to 20%. The first step is acid-catalyzed esterification by using 0.5% H2SO4, alcohol 6:1molar ratio with respect to the high FFA Karanja oil to produce methyl ester by lowering the acid value, and the next step is alkali-catalyzed transesterification. The yield of biodiesel from high FFA Karanja oil by dual step process has been observed to be 96.6–97%.
Methylcyclopentane was caused to react over Pt-black, Pt-SiO2 (EUROPT-1) 0.2% and 10% Pt-Al2O3 and the mechanical mixtures of the first two catalysts with AI (to give Al2O3 upon oxidation) and TiO2. Product distributions and activation energies for hydrogenolysis, ring opening products and methylcyclopent-1-ene as well as the ratios of the ring opening products were determined. Three mechanisms of ring opening have been proposed, two of them occurring on metal sites, the third on the metal-support phase boundary (adlineation mechanism). All these have different ring opening selectivity. The adlineation mechanism is supported by changing this selectivity upon creating new phase boundaries in mechanical mixtures.
A flow recirculation, isotopic tracer method was employed to determine sulfur uptake and sulfur exchange for a number of catalysts consisting of combinations of Mo, W, Ni, Co, Pd, and Pt, supported on alumina. By considering adsorption and exchange equilibria, basic equations were derived for calculation of extent of sulfur heteroexchange and fraction of exchangeable sulfur in the sulfided catalysts. Exchange equilibrium was experimentally established by approaching exchange from opposite directions. Variations in sulfur uptake and extent of exchange were obtained for the different catalysts. In all cases, the exchangeable sulfur was less than the total sulfur content. It is proposed that the fraction exchangeable sulfur is related to the edge S to total S ratio of the basic MoS2 particles. On this basis, average MoS2 slab sizes were estimated by application of slab models. The amount of exchangeable sulfur correlated reasonably well with thiophene hydrodesulfurization activity of the catalysts.
Catalytic deoxygenation of palmitic and stearic acids mixture was studied over four synthesized Pd catalysts supported on synthetic carbon (Sibunit) in a semibatch reactor and dodecane as a solvent at 260–300 8C. The catalysts were prepared by precipitation deposition method using Pd chlorides as metal precursors. All catalysts contained 1 wt.% Pd, however, the metal dispersion was systematically varied. An optimum metal dispersion giving the highest reaction rate was observed. The main liquid phase products were n-heptadecane and n-pentadecane, which were formed in parallel. In addition to the
particle size effect the impact of mass transfer was elucidated and a detail discussion on temperature programmed desorption of CO from the fresh and spent samples was provided.
A novel method for production of diesel-like hydrocarbons via catalytic deoxygenation of fatty acid is discussed. The model compound stearic acid is deoxygenated to heptadecane, originating from the stearic acid alkyl chain. The deoxygenation reaction is carried out in a semibatch reactor under constant temperature and pressure, 300 °C and 6 bar, respectively. A thorough catalyst screening was performed to obtain the most promising metal and support combination. The catalysts were characterized by N2-physisorption, CO-chemisorption, and temperature-programmed desorption of hydrogen. A highly active and selective in the deoxygenation reaction of stearic acid carbon supported palladium catalyst converted stearic acid completely with >98% selectivity toward deoxygenated C17 products.
Vegetable oil hydrocracking was studied in a batch reactor under high hydrogen partial pressure (10–200 bars) at 623–673 K, catalyzed by either reduced Ni/SiO2 or sulphided Ni-Mo/γ-Al2O3. We have established the sequence of reactions which transform a vegetable oil into a diesel-type fuel. We have demonstrated the role of the catalyst in each of these reactions, and the occurrence of thermodynamic equilibria restricting the completion of the transformation. The displacement of these equilibria was achieved by an increase in hydrogen pressure, where molar yields close to 100% were attained. The corresponding product is a mixture of hydrocarbons (essentially normal alkanes in the diesel fraction).
Deoxygenation reaction of vegetable oils over a carbon-supported metal catalyst was studied as a suitable reaction for production of diesel-fuel-like hydrocarbons. Stearic acid, ethyl stearate, and tristearine have been used as model compounds. Catalytic treatment of all the three reactants resulted in production of n-heptadecane as the main product with high selectivity.
To produce diesel fuel from renewable organic material such as vegetable oils, it has for a number of years been known that
triglycerides can be hydrogenated into linear alkanes in a refinery hydrotreating unit over conventional sulfided hydrodesulfurization
catalysts. A number of new reactions occur in the hydrotreater, when a biological component is introduced, and experiments
were conducted to obtain a more detailed understanding of these mechanisms. The reaction pathways were studied both in model
compound tests and in real feed tests with mixtures of straight-run gas oil and rapeseed oil. In both sets of experiments,
the hydrogenation of the oxygen containing compounds was observed to proceed either via a hydrodeoxygenation (HDO) route or
via a decarboxylation route. The detailed pathway of the HDO route was further illuminated by studying the hydroprocessing
of methyl laurate into n-dodecane. The observed reaction intermediates did not support a simple stepwise hydrogenation of the aldehyde formed after
hydrogenation of the connecting oxygen in the ester. Instead, it is proposed that the aldehyde formed is enolized before further
hydrogenation. The existence of an enol intermediate was further corroborated by the observation that a ketone lacking α-hydrogen
(that cannot be directly enolized) had a much lower reactivity than a corresponding ketone with α-hydrogen. In real feed tests,
the complete conversion of rapeseed oil into linear alkanes at mild hydrotreating conditions was demonstrated. From the gas
and liquid yields, the relative rates of HDO and decarboxylation were calculated in good agreement with the observed distribution
of the n-C17/n-C18 and n-C21/n-C22 formed. The hydrogen consumption associated with each route is deduced, and it was shown that hydrogen consumed in the water-gas-shift
and methanization reactions may add significant hydrogen consumption to the decarboxylation route. The products formed exhibited
high cetane values and low densities. The challenges of introducing triglycerides in conventional hydrotreating units are
discussed. It is concluded that hydrotreating offers a robust and flexible process for converting a wide variety of alternative
feedstocks into a green diesel fuel that is directly compatible with existing fuel infrastructure and engine technology.
The Saskatchewan Research Council (SRC), in cooperation with Natural Resources Canada and Agriculture and Agri-Food Canada, investigated the use of conventional refinery technology to convert vegetable oils into a product resembling diesel fuel. SRC found that the use of a medium severity refinery hydroprocess yielded a product (‘super cetane’) in the diesel boiling range with a high cetane value (55–90). Preliminary engine testing by ORTECH has shown that the impact of the ‘super cetane’/diesel mixture (‘green diesel’) on engine emissions is similar to the impact cetane enhancement via a nitrate additive has when added to conventional diesel fuel. Advantages of hydroprocessing over esterification in the Canadian context include lower processing cost, compatibility with infrastructure, engines and fuel standards, and feed stock flexibility. Further research in the areas of process optimization, alternative feed stock selection, cold flow properties, and multi-cylinder emission testing is planned. In cooperation with a commercialization partner, Arbokem Inc., pilot testing of the hydroprocess was done and was proven successful. A fleet demonstration and evaluation is currently underway.
The liquid-phase deoxygenation reaction of unsaturated renewables has been investigated in a semi-batch reactor. The reactants examined were the monounsaturated fatty acid, oleic acid, the diunsaturated fatty acid, linoleic acid and the monounsaturated fatty acid ester, methyl oleate. The reactions were carried out over a Pd/C catalyst under constant pressure and temperature in the following domain, 15–27 bar and 300–360 °C, respectively. The influence of carrier gas was additionally investigated. The impact as solvent (mesitylene) was studied as well and reaction pathways were proposed. Furthermore, continuous deoxygenation experiments were conducted, facilitating understanding of the catalyst stability and catalyst deactivation. The deoxygenation catalyst was characterized by physisorption, temperature programmed desorption (TPD), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM).
A novel field of the catalytic application of Pt/SAPO-11 catalysts for the isomerization of pre-hydrogenatedsunflower oils aiming the production of diesel fuel components is presented. Experiments were carried out over 0.2–1.0%Pt/ SAPO-1 1 catalysts at 280–380°C, 30–80 bar; LHSVs of 1.0–4.0 h1, H2/feed of 250–400 Nm3/m3. Results indicated that the yield of biogasoils obtained under favorable process conditions was >88%, the ratio of i-/n-paraffins was 3.2–6.8, the cetane numbers were 79–85 units and the cold filter plugging point (CFPP) values were between 19– 16°C. These are excellent blend stocks of diesel fuels.
The importance of the economical production and usage of new generation biofuels, the so-called bio gas oil (paraffins from triglycerides) and the results of the investigation for their productability on the CoMo/Al(2)O(3) catalyst, which was activated by reduction, are presented. The conversion of triglycerides, the yield of total organic fractions and the target product, furthermore the type and ratio of deoxygenation reactions were determined as a function of process parameters. The advantageous process parameters were found (380 degrees C, 40-60 bar, 500-600 Nm(3)/m(3) H(2)/sunflower oil ratio, 1.0 h(-1)), where the conversion of triglycerides was 100% and the yield of the target fraction [high paraffin containing (>99%) gas oil boiling range product] was relatively high (73.7-73.9%). The deoxygenation of triglycerides the reduction as well as the decarboxylation/decarbonylation reactions took place. The yield of the target fractions did not achieve the theoretical values (81.4-86.5%). That is why it is necessary to separate the target fraction and recirculate the heavy fraction.
Adsorption of reaction intermediates appearing during CO hydrogenation at the sulfur covered MoS2(1 0−1 0) surfaces, Mo-termination with 42% S coverage and S-termination with 50% S coverage, are investigated systematically using periodic density functional theory methods. Computed vibrational frequencies of all intermediates are compared with observed data from infrared (IR) spectroscopy allowing a detailed interpretation and assignment of the different features in the experimental spectra. The pathway for CO hydrogenation on both terminations has been studied in detail where the most likely reaction path involves C1 type surface species in the sequence CO→CHO→CH2O→CH2OH→CH2→CH3→CH4 in agreement with the experiment.
Hydrocracking of used cooking oil is studied as a potential process for biofuels production. In this work several parameters are considered for evaluating the effectiveness of this technology, including hydrocracking temperature, liquid hourly space velocity (LHSV) and days on stream (DOS). Conversion and total biofuels production is favored by increasing temperature and decreasing LHSV. However moderate reaction temperatures and LHSVs are more attractive for diesel production, whereas higher temperatures and smaller LHSVs are more suitable for gasoline production. Furthermore heteroatom (S, N and O) removal increases as hydrocracking temperature increases, with de-oxygenation being particularly favorable. Saturation, however, is not favored with temperature indicating the necessity of a pre-treatment step prior to hydrocracking to enable saturation of the double bonds and heteroatom removal. Finally the impact of extended operation (catalyst life) on product yields and qualities indicates that all reactions are affected yet at different rates.
A technique to produce biodiesel from crude Jatropha curcas seed oil (CJCO) having high free fatty acids (15%FFA) has been developed. The high FFA level of JCJO was reduced to less than 1% by a two-step pretreatment process. The first step was carried out with 0.60 w/w methanol-to-oil ratio in the presence of 1% w/w H(2)SO(4) as an acid catalyst in 1-h reaction at 50 degrees C. After the reaction, the mixture was allowed to settle for 2h and the methanol-water mixture separated at the top layer was removed. The second step was transesterified using 0.24 w/w methanol to oil and 1.4% w/w NaOH to oil as alkaline catalyst to produce biodiesel at 65 degrees C. The final yield for methyl esters of fatty acids was achieved ca. 90% in 2 h.
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