Preparation of bimodal mesoporous silica containing cerious salt and its application as catalyst for the synthesis of biodiesel by esterification

摘要

A kind of bimodal mesoporous silica catalyst modified with ammonium cerous sulfate (ACS/BMMS) was synthesized and applied in the esterification of free fatty acid and alcohol. The characterization results including XRD, N-2 adsorption and desorption, FTIR, Si-29-NMR and TEM showed that ACS/BMMS has orderly arranged bimodal mesopores, the small mesopore diameter is about 4.0-6.0 nm and the large mesopore diameter is in the range of 7.0-9.0 nm. The chemical interaction existed between silica group Si (OH)(2)(OSi)(2) and the NH4 (+), SO4 (2-) and Ce-O groups of cerious salt. When the loading is not more than 10%, cerious salt dispersed finely on the supports. Oleic acid and methanol were used as the raw material of probe reaction; ACS/BMMS had significantly better activity than the ACS/SBA-15, ACS/SBA-16, ACS/MCM-41, BMMS and bulk ACS. The optimum loading of ACS is 10%, the optimum reaction conditions are reaction temperature 140 A degrees C, reaction time 2 h, mole ratio of methanol to oleic acid 2.0 and the dosage of catalyst 4.0%, in above situation the conversion of oleic acid is about 94.0%, the reusability of ACS/BMMS is much better than bulk ACS. The kinetic study showed that the esterification of oleic acid and methanol on ACS/BMMS match Eley-Rideal model very well.