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Commercial transesterification of vegetable oil to biodiesel using alkaline hydroxides requires expensive refined vegetable oil and anhydrous alcohols to avoid saponification. These issues are not present in the acid-catalyzed process; however, the challenge still lies in developing stable and active solid acid catalysts. Herein, Amberlyst 45, a resin for high-temperature application, was efficiently used for biodiesel production by the methanolysis or ethanolysis of vegetable oil. Yields of up to 80 and 84% were obtained for the fatty acid methyl ester and the fatty acid ethyl ester, respectively. Two processes are proposed and showed to be efficient: (i) incremental addition of alcohol along with the reaction for both methanolysis and ethanolysis; or (ii) one-pot reaction for ethanolysis using oil/ethanol molar ratio of 1/18. The catalytic system used also showed to be compatible with used oil (2.48 ± 0.03 mg NaOH g oil −1) and to the presence of water (10-20 wt. % based on the alcohol), allowing the use of waste oil and hydrated alcohol.

Herein, we propose methodologies for the direct syntheses of Sn-containing MCM-41, SBA-16, MCM-48 with tin loadings between 1.5 and 4.5%. The catalysts were active in the isomerization of glucose to fructose, and the sample containing 3.0% of Sn showed the highest selectivity. Compared to the other structures, Sn-MCM-48 displayed a lower selectivity to fructose and a higher one to mannose, which is due to the presence of K+ remaining from the synthesis gel. Interestingly, the TOFFru is similar for Sn-MCM-41(3.0%) and K+/Sn-MCM-48­(3.0). For K+/Sn-MCM-48­(3.0%), the TOFMan and TOFFru were comparable. The presence does not affect the rate of fructose formation, but it promotes side reactions that involve glucose epimerization to mannose and, more importantly, the decomposition of glucose to unidentified products. Indeed, the ratio (TOFFru+TOFMan)/TOFGlu was 0.79, 0.37, and 0.81 for Sn-MCM-41, K+/Sn-MCM-48, and Sn-SBA-16(3.0%). The lowest TOF for fructose formation was observed for Sn-SBA-16(3.0%), which can be attributed to the high contribution of Sn in high coordination and extra framework tin oxide. For the direct conversion of glucose to HMF, Sn-MCM-41(3.0%), K+/Sn-MCM-48­(3.0%), and Sn-SBA-16(3.0%) were combined with HCl, reaching selectivities of 77, 73, and 67%, respectively. These results are comparable or superior to those previously reported.

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