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Abstract: Acid-catalyzed esterification and transesterification reactions, suitable for biodiesel production from high acid value oils, face a problem of long reaction time. In this study, we developed a two-step process for fast acid-catalyzed biodiesel production from high acid value oil in a microstructured reactor, which was assembled with an SIMM-V2 micromixer connected with a 0.6mm i.d. stainless steel capillary. Esterification of oleic acid and transesterification of cottonseed oil with methanol were separately carried out to find suitable reaction conditions. The influences of the residence time, the methanol to acid/oil molar ratio, the catalyst concentration, the water/acid concentration and the reaction temperature were examined. The highest oleic acid conversion was obtained when esterification of oleic acid with methanol was carried out at 100°C with the residence time of 5min, while the highest yield of fatty acid methyl ester (FAME) was achieved when transesterification of cottonseed oil with methanol was conducted at 120°C with the residence time of 20min. Thereafter, a two-step process was developed based on the above reaction conditions with the first and second steps separately conducted under the esterification and transesterification reaction conditions. The results indicated that the acid value of the acid oil was reduced from 160 to 1.1mg KOH/g with a methanol to acid molar ratio of 30, the H2SO4 concentration of 3wt%, a residence time of 7min at 100°C in the first step. The final FAME yield reached 99.5% with a methanol to triglyceride molar ratio of 20, the H2SO4 concentration of 3wt%, a residence time of 5min at 120°C in the second step. Therefore, biodiesel production from high acid value oil can be continuously achieved at high yields by acid-catalyzed transesterification in microstructured reactors with total reaction times of less than 15min. [Copyright &y& Elsevier]

Abstract: Sulfonated carbon–silica composites with surface areas of over 600m2/g and pore sizes of 1.5–2.2nm were prepared by incompletely carbonizing sucrose dispersed on MCM-48 and sulfonating the obtained carbon/MCM-48 composites. The samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, N2 adsorption, energy dispersive X-ray analysis, and X-ray photoelectron spectroscopy. The catalytic activities of these composites were studied in the esterification of acetic acid with n-butyl alcohol. The pore sizes and catalytic activities of the sulfonated carbon–silica composites were adjustable by changing the amount of sucrose loadings, and the composites exhibited enhanced hydrothermal stability and amphiphilic property. When the sucrose loading was close to the monolayer dispersion capacity of sucrose on MCM-48 (1.1g sucrose/g MCM-48), the resulting sulfonated carbon–silica composites exhibited surface areas of 700–724m2/g and n-butyl acetate yields of 90.4–98.7% in the esterification of acetic acid with n-butyl alcohol. They also showed obvious catalytic activities in the esterification of long-chain fatty acids with ethanol. The expensive MCM-48 could be easily recycled by simply calcining the sulfonated carbon–silica composites in air. [Copyright &y& Elsevier]