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Fig. S5. XRD pattern of varying metal to zirconia atomic ratio ( = SrZrO 3 , = SrO, = m- ZrO 2 , o = CaZrO 3 , * = CaO, = MgO, = BaZrO 3 ).
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Mixed oxide of Sr and Zr has been prepared by co-precipitation method and examined as heterogeneous catalyst for one pot esterification and transesterification of waste cooking oil with ethanol for the production of fatty acid ethyl esters (FAEE). Mixed oxide of Sr:Zr with 2:1 atomic ratio and calcined at 650 ºC showed the optimum activity among th...
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Cheap raw materials and optimum process conditions of a transesterification reaction continued to be the most essential factors in determining the production of the biodiesel in commercial quantity to meet up the current global demand. In this study the crude cottonseed oil was used as an economical feedstock for biodiesel production since its dema...
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... It can be seen from Table 4 that enthalpy change (ΔH) value for both irreversible pseudo 1st and 2nd order models for CSO transesterification are 13.89 kJ/mol and 35.93 kJ/mol, respectively. Positive values of ΔH for CSO are an indication that an energy (heat) input from an external source is required to raise the energy level and transform the reactants to their transition state and show that the process is endothermic in nature [96,97]. These ΔH values for the transesterification of CSO (13.89 kJ/mol and 35.93 kJ/mol) in this study were similar with 16.35 kJ/mol gotten by Nautiyal et al. [98] for the transesterification of Spirulina platensis algea biomass for pseudo first order model. ...
... Entropy value (ΔS) for irreversible pseudo 1st and 2nd order models for CSO transesterification was − 0.158 kJ/mol and − 165 kJ/mol, respectively. The negative value obtained suggests an associative mechanism whereby the reactant species have combined together to form a more ordered transition state [96]. This value were within the range reported by Kaur and Ali [96] (− 0.121 kJ/mol) and Wu et al. [97] (− 0.18 kJ/mol), for transesterification of waste cooking and soybean oils, respectively. ...
... The negative value obtained suggests an associative mechanism whereby the reactant species have combined together to form a more ordered transition state [96]. This value were within the range reported by Kaur and Ali [96] (− 0.121 kJ/mol) and Wu et al. [97] (− 0.18 kJ/mol), for transesterification of waste cooking and soybean oils, respectively. Values of Gibbs free energy (ΔG) for irreversible pseudo 1st and 2nd order models for CSO transesterification ranges from 20.43 -23.59 kJ/mol and 85.21 -88.31 kJ/mol, respectively. ...
... Reaction of Lewis acid and oxygen containing molecule results in active catalyst having basic nature. Several advantages are associated with this large surface area including cost effectiveness and excessive chemical stability [120][121][122]. Carbon supported metal oxide catalyst efficiently perform transesterification, hamper soap formation, and enable catalyst recycling [123]. ...
Disappointingly, tremendous increase in water pollution due to different contaminants including inorganic contaminants, novel human-induced contaminants as well as emerging organic contaminants is becoming a serious challenge. The term 'emerging organic contaminants' covers newly synthesized compounds as well as the compounds, which are found as new contaminants in the environment. Alongside human-induced contamination , unpredictable weather conditions and rising temperature are likely to influence water dissemination and accessibility. So, it is very important to develop efficient wastewater treatment methods to make wastewater a useful resource and ensure its reusability. Amongst the various novel methods/technologies regarded for wastewater treatment, metallic nanoparticles have been studied intensively owing to their promising properties such as large surface area, easily modified and stability in water. Strontium (Sr), which belongs to group II of metallic elements, has worth exploring properties because of its resemblance to magnesium and calcium. This resemblance makes it very appropriate for wastewater treatment as well as medical applications. In this review article, advances in the use of Sr-based nanomaterials in the removal of different classes of contaminants (heavy metals, inorganic ions, dyes, and antibiotics) via degradation or/and adsorption has been highlighted. Different types of Sr-based nanomaterials are described, followed by discussion on synthesis of Sr-based nanomaterials using several methods, among which hydrothermal and co-precipitation are most used ones owing to their simplicity, less toxicity, and reliability. Furthermore, their corresponding usage in medical applications is summarized as well as future perspectives are discussed.
... Supercritical fluids have been developed for improved biodiesel production, resulting in short reaction times [25]; however, it requires extremely high pressure and temperature, which raises safety concerns and requires expensive equipment [25]. Recently, several studies have reported the use of binary acid-base catalysts (such as ZC-450 [26], CaO-ZSM-5 zeolite/Fe 3 O 4 [27], CaO-La 2 O 3 [28,29], mixed oxide of Sr:Zr [30], KOH/corncobs activated carbon [31], Sn-CaO [32], and synergistic catalysis of mesoporous polymeric acid and base catalysts [33]), which possess acidity and basicity, for one-pot esterification-transesterification. However, these heterogeneous catalysts exhibit low catalytic activity due to mass transfer limitations [10]. ...
... Those catalysts exhibit both acid and alkali properties, thus simultaneously catalyzing esterification and transesterification reactions. Several binary acid-base catalysts, such as CaO-La 2 O 3 [29], CaO-La 2 O 3 /C nanorod [29], mixed oxide of Sr:Zr [30], and Sn-CaO [32], have been proposed for one-pot reactions. Those catalysts can produce biodiesel with high yield but still require long reaction times (4-7 h). ...
Biodiesel is a promising alternative to petrodiesel, but its production from acid oils retains several technical challenges. Therefore, this study developed a new approach involving 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU)-catalyzed one-pot reaction (simultaneous esterification-transesterification) to produce biodiesel with enhanced reaction efficiency. The reaction was performed under water removal conditions and optimized using response surface methodology to maximize the biodiesel yield. The optimal conditions for the one-pot reaction had a reaction time of 2.73 h, temperature of 143°C, methanol:oil molar ratio of 24.3 : 1, and DBU loading of 30.1%. Under the optimal conditions, maximum total biodiesel of 97.1% was obtained. DBU could be repeatedly used for at least 5 cycles to yield over 91% biodiesel. This study suggests that DBU efficiently catalyzed esterification and transesterification simultaneously and the DBU-catalyzed one-pot reaction is an efficient method for biodiesel production from high-free-fatty acid oils.
... Where, the integrated peak areas of methoxy and α-methylene protons are I (methoxy) and I (α-methylene), respectively. Using equation (2) and the technique described in the reported work [23], the turnover frequency (TOF) of the catalyst is calculated. ...
... It controls the rate of the overall transesterification reaction. In published work, the activation energies of KOH/ZSM-5-Fe 3 O 4 [55], CaO [56], 20-CeO 2 /-Li/SBA-15 [52], and Sr:Zr mixed oxide [23] catalysts were found to be 122.7 kJ/mol, 78.4 kJ/mol, 57.7 kJ/mol, and 48.2 kJ/mol, respectively. The forward reactions of D→M are more likely to happen because their Table 3 Step-by-step transesterification reactions and their activation energies and thermodynamic parameters. ...
(TPA) was supported over graphene oxide (GO) and used as a heterogeneous catalyst. The structure of the catalyst was evaluated by a powder X-ray diffraction (XRD) study. The elemental oxidation state and catalyst composition was confirmed by X-ray Photoelectron Spectroscopy (XPS) analysis. The temperature-programmed desorption (TPD) technique supported the existence of acidic and basic sites on the surface of the catalyst. Being acidic, TPA probably catalyzes the esterification while K+ transesterification activity to the catalyst. Beneath the optimized reaction conditions, i.e. loading of catalyst 10 wt% (concerning oil), methanol: oil molar ratio of 9:1with reaction temperature of 65 ◦C, >98.5% (±0.34) biodiesel was produced within 1.5 h of reaction period. By using centrifugation, the catalyst was extracted from the reaction mixture and recycled six times. The metal level in the reaction mixture was determined to be less than 2 ppm, supporting the stability of the catalyst. Addi-tionally, the catalyst was found to be active even in the existence of free fatty acid (up to 8.76 wt%) and moisture(up to 4.0 wt%) contents. The positive values of enthalpy of activation (ΔH‡) and free energy of reaction (ΔG‡)highlighted the endothermic and non-spontaneous nature of the reaction. The kinetic modeling study, using MATLAB software (version R2021b), suggests that the reaction of WO with the synthesized catalyst was found to follow a (pseudo) first-order kinetic equation. A negative value of entropy of activation (ΔS‡) indicates that the reaction of triglyceride (T) to diglyceride (D) follows the associative pathway. In contrast, the diglyceride to monoglyceride (M) and monoglyceride to glycerol (G) conversion progressed via dissociative route
... In another approach, second-generation feedstock could be utilized for BD production in a two-step process involving (i) acid-catalysed FFA esterification which follows the (ii) base-catalysed triglyceride transesterification. 50,51 At an industrial scale, Shirke Energy utilizes second-generation feedstock (jatropha oil and animal tallow) while employing conventional NaOH and KOH catalysts for methanolysis. 52 In another approach, solid acid catalysts, Ce/ ZrO 2 -TiO 2 / SO 4 2-, were employed 50 for the esterification of fatty acids present in second-generation feedstock followed by alkali-catalysed transesterification of the Vos, as shown in Figure 3.4. ...
... Studies proved that SrO NPs loaded on porous oxides, such as Al 2 O 3 , SiO 2 , and TiO 2 , exhibit a better product yield in biomass conversion. 89,133,140 Activated carbons were also used as a catalyst support. The highsurface-area material possesses many advantageous, including high chemical stability and cost effectiveness. ...
Biodiesel is a renewable and environmentally friendly alternative to fossil fuels. Despite nearly 3 decades of research in the field of biodiesel, there remains major obstacles for large-scale production. In the search for an active, selective, and reusable solid base catalyst, strontium oxide (SrO) is emerging out as a preferred choice for the transesterification reaction under various methods of activation. SrO exhibits the highest activity among processable alkaline earth metal oxides as a result of its strong basicity. SrO nanoparticles (NPs) and hybrids showed improved performance. Recent progress achieved in the development of synthetic methods of SrO NPs is reviewed. Advantages of SrO-based nanocomposites for biodiesel production are discussed. Finally, potential support materials for enhancing the catalytic performance of SrO NPs with commercial implications are elaborated.
... The catalyst deactivation at higher FFA and moisture concentration may be due to the robust contact between catalyst active sites and polar carboxylic acid group of FFA and/or -O-H of water molecule. 22 ...
To prepare the heterogeneous catalyst for the simultaneous transesterification and esterification of waste cooking oil (WO), 12‐tungustophosphoric acid (TPA) and K+ were loaded over alumina. The catalyst structure was confirmed by powder X‐ray diffraction analysis while the catalyst composition and the elemental oxidation state by X‐ray photoelectron spectroscopic study. The surface morphology of the catalyst was established by high‐resolution transmission electron microscopy. The temperature‐programmed desorption study supports the existence of basic and acidic sites over the catalyst surface owing to the presence of potassium oxide and TPA, respectively. Underneath the optimized conditions for reaction, that is, 10 wt% of catalyst with respect to oil, 9:1 methanol to oil molar ratio and 65°C reaction temperature, 97% fatty acid methyl ester (FAME) yield was obtained within 1.25 h of reaction time. The catalyst was recovered from the reaction mixture via centrifugation and reused in four consecutive runs. Moreover, the presence of high moisture (4 wt%) and free fatty acid (7.8 wt%) contents was not found to have any adverse effect on the catalyst activity. To demonstrate the catalyst stability, the metal content in the reaction mixture was analyzed, and total metal content was found to be less than 2 ppm to hold the catalyst stability. The kinetic study suggests that the reaction follows (pseudo) first‐order kinetic equation with the prepared catalyst.
... Fig. 5-B illustrates the plot of ln k vs. 1/T where E a and A correspond to 63.07 kJ mol −1 and 11.4E10 5 , respectively. An activation energy value greater than 25 kJ mol −1 indicates that PRsulf catalytic activity did not limit the mass transfer during transesterification of Pequi bio-oil (Kaur and Ali, 2014). Studies of Tan 3.6. ...
The transesterification of Pequi (Caryocar brasiliensis Camb.) bio-oil was conduct with a heterogeneous acid catalyst prepared with the fruit’s carbonized rinds. The newly-developed catalyst was characterized by TGA/DSC, XRD diffraction, and FTIR analysis. Experiments for process optimization of biodiesel production and catalyst reusability were carried out, also investigating the kinetics involved in bio-oil mass conversion. Crude FAME content was analyzed with GC-FID gas chromatographer and its fuel properties compared to worldwide standards. Main finds were a crude FAME majorly composed by methyl esters of palmitic acid, linoleic acid, and stearic acid, representing about 49.93, 13.24, and 10.16 wt.%, respectively. Optimized conditions for maximum FAME synthesis from Pequi bio-oil (99.4 ± 0.33%) were 18:1 M ratio of methanol to bio-oil, 60 °C of temperature, 100 min of reaction, catalyst load of 2.5 wt.%, and stirring speed of 600 rpm. Kinetics of the bio-oil mass conversion through transesterification presented reaction rates varying from 0.016 to 0.091 min−1, 63.07 kJ kg−1 of activation energy (Ea), and pre-exponential value (A) of 11.4E10^5. Catalyst efficiency decreased to 34.9% after 10 reuse cycles. Fuel properties of the crude FAME met worldwide standards of biodiesel quality, thus indicate that Pequi bio-oil is a viable, sustainable, and widely available feedstock option in Brazil.
... Hence, the present catalyst was found to be suitable for transesterification of the feedstock with very less FFA contents. The deactivation of catalyst in response to higher FFA content can be explained through the neutralisation or partial blockage of active basic sites of catalyst by the interaction with polar carboxyl group of FFA to explain the decline in the catalyst action in the presence of higher FFA content [61]. ...
5-Na/ZnO loaded SBA-15 has been prepared by one-pot method in atmospheric conditions (without employing hydrothermal treatment) and following wet impregnation method. The prepared catalyst was characterised by using several techniques viz., BET method for determination of surface area, FE-SEM for morphology of catalyst, XPS study to determine the oxidation state of constituent elements. The catalyst was utilised for transesterification from virgin cotton seed oil and the catalyst activity was dependant on its basic strength. Under optimal reaction conditions of catalyst amount 12 wt%, methanol to oil molar ratio of 24:1 at reaction temperature of 65 °C, the prepared catalyst yielded > 98% fatty acid methyl ester in 4 h of reaction duration. The catalyst was able to yield conversion level as good as ∼74% even in 5th cycle after regeneration. Leaching of < 5 ppm metal content was observed, in 4th and 5th cycle, which was within the ASTM specified limitations. The thermodynamic parameters for the reaction, viz., activation energy Ea, ΔH‡, ΔS‡, ΔG‡ were calculated as 77.3 kJ mol⁻¹, 74.2 kJ mol⁻¹, -0.064 kJ mol⁻¹ and, + 93.2 kJ mol⁻¹ respectively.
... It is worth noting that, for this reaction system, a temperature of 100°C was found to be the optimum reaction temperature ( Lucena et al, 2008;Lucena et al, 2011). Although this work will investigate a homogenously catalyzed reaction for the conversion of FFA, it is important to mention that several studies were able to efficiently achieve that purpose using different heterogeneous catalysts ( Kumar and Ali, 2015;Kaur and Ali, 2015;Kaur and Ali, 2014). The aim of this work is to evaluate the performance of a promising novel protocol for the pretreatment of high FFA waste oil before its complete transesterification into biodiesel. ...
The present work investigates the energy consumption and yield of the esterification reaction of free fatty acids (waste oil pretreatment) under a simultaneous water removal by adsorption. The reaction was performed under methanol, ethanol, and 1-propanol at the optimum reaction temperature of 100°C. The higher boiling point temperature of 1-propanol reduced the energy requirement of the reaction by 36.3 and 34.4% compared to methanol and ethanol, respectively. Moreover, despite the higher reactivity associated with alcohols having lower carbon chains, the reaction yield was approximately 16.4% higher under 1-propanol than the other two alcohols. This can be ascribed to the ability to use higher amounts of 1-propanol while maintaining lower energy consumption. The results also indicated that the reaction at 100°C under methanol and ethanol had a similar energy consumption and yield, favoring the use of the renewable ethanol over the widely used nonrenewable methanol. Finally, these findings highlight the importance of investigating the energy consumption of novel oil pretreatment processes and not solely focus on their ability to convert free fatty acids to biofuel.
