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Currently, the catalytic efficiency and reusability of the solid base catalysts cannot meet the demand of industrial biodiesel production under low temperature. The purpose of this study is to define the kinetics of heterogeneous transesterification process which might be used for the prediction of the biodiesel synthesis at high temperature and pressure. The focus in this study was paid to recently reported data obtained with different catalysts used for biodiesel synthesis in a batch reactor at high temperatures. It was shown that three kinetic models that include: a) irreversible first order reaction; b) reaction with changeable order; and c) resistances of mass transfer and chemical reaction at active sites of the catalyst could be applied for predicting the effect of high temperature of the transesterification. The apparent reaction rate constant of the irreversible first order reaction was determined, as well as the parameters of the other two, more complicated kinetic models. The best agreement was obtained with the more complicated models and the mean relative percent deviation between calculated and experimentally determined triacylglycerols conversion for these kinetic models is between 3 and 10%. [Projekat Ministarstva nauke Republike Srbije, br. 45001]

A heterogeneous cerium–manganese oxide catalyst was synthesized by a co-precipitation method, characterized and tested in soybean oil transesterification with methanol under subcritical condition for methanol. Conversion of triglycerides after 40 min of transesterification in a batch process was over 99% with a fatty acid methyl ester (FAME) yield of 91.6% when 3 wt.% of catalyst based on oil, and 18:1 methanol/oil molar ratio were applied. The same amount of catalyst was used in 12 cycles of transesterification with catalyst regeneration performed only after the 7th cycle. The catalyst exhibited good tolerance toward soybean oil containing below 1.5 wt.% of water or 4 wt.% of free fatty acids. The mechanisms of Ce/Mn catalytic activity and its deactivation were discussed according to the characterization of the fresh and used catalyst according to results of different analytical methods: the Hammett titration, BET surface area, scanning electron microscopy with energy dispersive spectroscopy (SEM–EDS), FTIR, X-ray diffraction (XRD), ICP-AAS and TG-DSC. It was assumed that deactivation of catalyst was mainly a consequence of manganese solubility in methanol and glycerol. [ABSTRACT FROM AUTHOR]

The Strontium doped cinder was prepared using the wet impregnation method and analyzed as catalyst for biodiesel synthesis. Different procedure for cinder impregnation were investigated (temperature and duration of catalyst calcinations, the concentration of SrCl 2 solution) and optimal condition was established: impregnation 20 g of cinder 2–5 mm particles with 0.2 M SrCl 2 solution followed by calcinations at 1000 °C for 4 h. The Sr-cinder activity was tested at 90–200 °C using 1–5% mass of catalyst with different molar ratio of methanol to soybean oil (from 9 to 36). The maximum triglycerides (TG) conversion of 99.0% with the Fatty Acid Methyl Esters (FAME) yield of 97.1% was obtained by using 4% catalyst at 180 °C, for 1 h, and methanol/oil molar ratio 24:1. Influence of free fatty acid (FFA) and water in soybean oil on catalyst activity was analyzed, too. The catalyst could be used for 14 times with TG conversion and FAME yield above 90% and 80% respectively. The Sr-doped cinder catalysts before and after transesterification were characterized using BET surface area, basic strength, X-ray diffraction (XRD), scanning electron microscopy (SEM) and ICP-AAS. Results showed that the formation of SrAl 2 Si 2 O 8 and Sr 5 Al 8 O 17 complexes should be the main reason for the catalytic activity of prepared catalyst. Slow decrease of catalyst activity during its repeated use is result of Sr–Al-glycerolate formation in reaction between Sr–Al complexes and glycerol. [ABSTRACT FROM AUTHOR]

The solid catalyst La/Mn oxide was prepared using co-precipitation method. The catalytic behavior for catalyzing transesterification of soybean oil with methanol under subcritical conditions was investigated in a batch reactor; optimization of several parameters for catalyst preparation and transesterification reaction was also performed. The triglyceride (TG) conversion of above 99% was obtained using La/Mn oxide catalyst prepared with La:Mn molar ratio of 2:1 and calcined at 600 °C for 90 min, under such reaction conditions as 3 wt.% of catalyst, methanol/oil molar ratio of 12:1, reaction temperature and time of 180 °C and 60 min, respectively. The catalyst shows good reusability, and can resist FFA to some extent. However, it is sensitive to water. The mechanisms of catalytic activity and deactivation were discussed according to the characterization of the fresh and used catalysts using basic strength, BET surface area, scanning electron microscopy with energy dispersive spectroscopy (SEM–EDS), and X-ray diffraction (XRD). Results demonstrated that the complex oxide LaMnO 3.15 was the dominant component. The crystalline structure of the catalyst after use changed remarkably and the active sites might be occupied by organics, which led to the deactivation or diminished activity of the catalyst in the repeated use process. [ABSTRACT FROM AUTHOR]

The manganese carbonate catalyst, prepared by precipitation method, was used in transesterification of soybean oil under subcritical condition of methanol. Catalyst samples were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS). The triacylglycerol (TAG) conversion and fatty acid methyl esters (FAME) yield were determined using high performance liquid chromatography (HPLC). The transesterification was realized for 1 h using various working conditions: 0-3 wt.% of catalyst (based on the mass of oil), the mole ratio of methanol to oil from 13:1 to 27:1 and temperature ranging from 393 to 473 K. A maximum TAG conversion of 98.1% could be obtained at the optimal reaction conditions: 2 wt.% of catalyst, methanol/oil mole ratio of 21:1, for 1 h in a batch reactor at 453 K. Kinetic analysis showed that the model based on mass transfer and chemical reaction at the catalyst surface confirmed the experimental data. Using that kinetic expression, the effect of continuous transesterification was proposed and verified by a 360-h long realized experiment in a laboratory packed-bed reactor (PBR). Slow deactivation of the catalyst was caused by leaching of Mn in both biodiesel and glycerol phases and by blocking the active sites of the catalyst with organic compounds. [ABSTRACT FROM AUTHOR]

In this study, comparison and effect of Cinder supported with Lanthanum and Manganese oxide as catalyst for transesterification of triglyceride to methyl ester is proposed. The reaction mechanism along with the effects of methanol to oil molar ratio, amount of catalyst to oil, reaction temperature were also discussed. Moreover reusability of catalyst, catalyst resistance toward Free Fatty Acid and water were also discussed. The results show that yield of biodiesel produced with Mn:La:Cinder catalyst was 99% at ≥150 °C in 6 h. Cinder supported with Mn shows conversion of triglycerides from soybean oil in reaction with methanol after 6 h was over 99% at 150 °C. For both catalyst 3wt% of catalyst based on oil, 24:1 methanol/oil molar ratio was reused for 7 times with regeneration. The catalysts displayed great resistance toward 2.5% water and 1% wt fatty acids. [ABSTRACT FROM AUTHOR]