Heterogeneous catalysis for sustainable biodiesel production via esterification and transesterification

Concern over the economics of accessing fossil fuel reserves, and widespread acceptance of the anthropogenic origin of rising CO2 emissions and associated climate change from combusting such carbon sources, is driving academic and commercial research into new routes to sustainable fuels to meet the demands of a rapidly rising global population. Here we discuss catalytic esterification and transesterification solutions to the clean synthesis of biodiesel, the most readily implemented and low cost, alternative source of transportation fuels to meet future societal demands

Kinetic study on catalytic conversion of glycerol to renewable acrolein

Biodiesel is a suitable alternative to gasoline and diesel since it emits less carbon emission. There has been a surplus of glycerol in the market due to biodiesel production. Glycerol may be a good source of bio-based feed since it is from a renewable source. The kinetic study of gas-phase glycerol dehydration reaction using a supported γ-Al2O3 nanoparticle based solid heteropoly acid catalyst (SiW20-Al/Zr10) has been investigated. A kinetic model was established, based on the reaction mechanism, taking into account two parallel reactions of glycerol degradation into acrolein or acetol. All the reaction rate constants and activation energies were determined at various reaction temperatures (280 - 340 °C). The first-order kinetic model and the experimental data fitted-well. Results revealed that all the rate constants increased with temperature, and the activation energies of glycerol dehydration to acrolein and acetol were 46.0 and 53.3 kJ/mol. The results from this study are useful for simulation and process modelling of a bio-refinery for sustainable production of biobased chemicals

Coke-tolerant SiW20-Al/Zr10 catalyst for glycerol dehydration to acrolein

Glycerol dehydration to acrolein over a series of supported silicotungstic acid catalysts (SiWx-Al/Zry) was investigated. Characterization results showed that the final catalyst had high thermal stability, a large pore diameter, strong Lewis acidic sites, and a large specific surface area. X-ray photoelectron survey spectra clearly showed peaks attributable to W (W 4f = 35.8 eV), Al2O3 (Al 2p = 74.9 eV), and ZrO2 (Zr 3d = 182.8 eV). The highest acrolein selectivity achieved was 87.3% at 97% glycerol conversion over the SiW20-Al/Zr10 catalyst. The prepared catalysts were highly active and selective for acrolein formation even after 40 h because of the presence of high concentrations of Lewis acidic sites, which significantly reduced the amount of coke on the catalyst surface. Response surface methodology optimization showed that 87.7% acrolein selectivity at 97.0% glycerol conversion could be obtained under the following optimal reaction conditions: 0.5 wt% catalyst, reaction temperature 300 °C, and feed glycerol concentration 10 wt%. Evaluation of a mass-transfer-limited regime showed the absence of internal and external diffusions over pellets of diameter dP < 20 μm. These results show that glycerol dehydration over a strong Lewis acid catalyst is a promising method for acrolein production

Gas phase glycerol dehydration to acrolein using supported silicotungstic acid catalyst

The gas phase dehydration of glycerol to acrolein over a series of supported silicotungstic acid (HSiW) on γ-Al2O3 nanoparticle (W10-Al, W20-Al, W30-Al and W40-Al) has been investigated. The catalysts were characterized by temperature programmed desorption, nitrogen adsorption–desorption, thermogravimetric analysis, X-ray diffraction, field-emission scanning electron microscopy and energy dispersive X-ray techniques. The large pore diameters (>21 nm) of the prepared catalysts alleviated the coke deposition effect. The acidity of the samples increased from 2 to 2.6 mmol/g.cat by varying HSiW loadings from 10 to 40 wt.% on γ-Al2O3 nanoparticle. The highest acrolein yield achieved was 74.1% at 94% glycerol conversion over W20-Al catalyst for 10 wt% glycerol feed concentration and 300 ˚C reaction temperature in 3 hours. The combined physicochemical characteristics of W20-Al made it more superior compared with other samples in the current study

Thermo-kinetic and diffusion studies of glycerol dehydration to acrolein using HSiW-Γ-Al2O3 supported ZrO2 solid acid catalyst

The thermo-kinetic study of gas-phase glycerol dehydration reaction using a supported γ-Al2O3 nanoparticle based solid catalyst (SiW20-Al/Zr10) has been investigated. The kinetic model was established based on the reaction mechanism, taking into account two parallel reactions of glycerol degradation into acrolein or acetol. Reaction rate constants and activation energies for all the products in the glycerol dehydration reaction were determined at various reaction temperatures (280–340 °C). The first-order kinetic model and the experimental data fitted-well. Also, based on thermodynamic analysis the values of ΔH‡, ΔS‡, and ΔG‡ for all the endothermic reactions were determined by Eyring equation. Finally, the absence of internal and external diffusions were confirmed by Weisz-Prate Criterion (CWP <1) and Mear's Criterion (CM < 0.15), respectively for pellet diameters less than dP < 5 μm. The results from this study are useful for future reactor modeling and simulation work

Gas phase selective conversion of glycerol to acrolein over supported silicotungstic acid catalyst

Gas phase dehydration of glycerol to acrolein over a series of supported HSiW on ZrO2 and nano-sized γ-Al2O3 catalyst has been investigated. The characterization results revealed that impregnation of γ-Al2O3 nanoparticles increased the specific surface area, pore diameter, and thermal stability of the supported catalysts. The highest acrolein selectivity of 88.5% at 97.0% glycerol conversion was achieved over 0.5g 30HZ-20A catalyst in 3h at glycerol feed concentration of 10wt%, temperature=300 ?C and TOF=136 h-1. The coke deposition has no significant effect on the activity of 30HZ-20A catalyst. Indeed, the catalyst was stable even after 40h

Hydrogen production from catalytic steam reforming of glycerol over various supported nickel catalysts

Supported Ni catalysts have been investigated for hydrogen production from steam reforming of glycerol. Ni loaded on Al2O3, La2O3, ZrO2, SiO2 and MgO were prepared by the wet-impregnation method. The catalysts were characterized by nitrogen adsorption–desorption, X-ray diffraction and scanning electron microscopy. The characterization results revealed that large surface area, high dispersion of active phase on support, and small crystalline sizes are attributes of active catalyst in steam reforming of glycerol to hydrogen. Also, higher basicity of catalyst can limit the carbon deposition and enhance the catalyst stability. Consequently, Ni/Al2O3 exhibited the highest H2 selectivity (71.8%) due to small Al2O3 crystallites and large surface area. Response Surface Methodology (RSM) could accurately predict the experimental results with R-square = 0.868 with only 4.5% error. The highest H2 selectivity of 86.0% was achieved at optimum conditions: temperature = 692 °C, feed flow rate = 1 ml/min, and water glycerol molar ratio (WGMR) 9.5:1. Also, the optimization results revealed WGMR imparted the greatest effect on H2 selectivity among the reaction parameters

Lipase@zeolitic imidazolate framework ZIF-90: A highly stable and recyclable biocatalyst for the synthesis of fruity banana flavour

A zeolitic imidazolate framework (ZIF-90) has been synthesized through solvothermal method. The structure was characterized by means of FT-IR spectroscopy, X-ray diffraction, thermogravimetric analysis (TGA), and scanning electron microscopy (SEM)/energy dispersive X-ray spectroscopy (EDS). The synthesized ZIF-90 was applied as a support for immobilization of porcine pancreatic lipase (PPL). The immobilized enzyme (PPL@ZIF-90) exhibited immobilization yield and efficiency of 66 ± 1.8 and 89 ± 1.4, respectively. The pH and thermal stability of PPL was improved after immobilization and the initial activity was retained at about 57 after 20 days of storage at 4 °C for PPL@ZIF-90. Moreover, about 57 of the original activity was remained following 10 cycles of application. In Michaelis-Menten kinetic studies, Km value for PPL@ZIF-90 was lower, while, the Vmax was higher than free PPL. Moreover, optimized conditions to produce fruity banana flavour upon esterification of butyric acid were investigated. The optimum esterification yield was 73.79 ± 1.31 in the presence of 245 mg PPL@ZIF-90, alcohol/acid ratio of 2.78 and 39 h reaction time. PPL@ZIF-90 showed 39 relative esterification yield after six cycles of reuse. The results suggested that PPL@ZIF-90 can be used as a potential effective biocatalyst for synthesis of isoamyl butyrate. © 202

Bio-removal of phenol by the immobilized laccase on the fabricated parent and hierarchical NaY and ZSM-5 zeolites

This study was performed to synthesize and characterize NaY and ZSM-5 zeolites and their hierarchical forms (HR-Y and HR-Z) through dealumination and soft templating procedure. The Brunauer-Emmett-Teller (BET) analysis showed significant increase in the average pore diameter (DP) size for HR-Y (2.43 nm) and HR-Z (5.07 nm) compared to those of the parent types (NaY and ZSM-5: 1.85 and 2.01 nm, respectively). The mesoporous pore volumes (Vmeso) exhibited notable enhancement for HR-Y (114) and HR-Z (566) compared to their parent forms. Laccase (Lac) was subsequently immobilized on NaY and ZSM-5 zeolites, and their hierarchical forms by immobilization efficiency of 74.4 ± 1.4, 71.6 ± 1.0, 98±2.9, and 94±1.8 for Lac@NaY, Lac@ZSM-5, Lac@HR-Y, and Lac@HR-Z, respectively. Thermal and pH stability of the immobilized laccases were enhanced compared with the free enzyme. The relative activity for the immobilized laccases was kept over 50 of its original activity after about 3 weeks of storage at 4 °C. Moreover, reusability of Lac@HR-Z and Lac@HR-Y was considerably higher (68 and 92, respectively) than those of Lac@ZSM-5 and Lac@NaY (6 and 5.6, respectively) after 10 cycles of reuse. Lac@HR-Z and Lac@HR-Y exhibited higher efficiency (80.5 and 89.3, respectively) in phenol bio-removal compared with those of ZSM-5 (67.5) and NaY (76.5). Besides, 90.4 ± 1.3 of phenol was practically removed under optimal conditions including 12 U/mg of Lac@HR-Y, 2.6 mM of phenol, and 70 min of the reaction time. Lac@HR-Y also exhibited 56 efficiency after 10 cycles of phenol removal. Furthermore, three phenolic compounds were detected by GC-mass analysis due to phenol bio-removal in the optimal conditions after removing the dark brown precipitate of polymerized metabolites. Therefore, Lac@HR-Y could be suggested for the elimination of phenol-containing pollutants that merits further investigations. © 2021 Taiwan Institute of Chemical Engineer