PREPARATION AND APPLICATION OF Zn-Al COMPLEXS OXIDE CATALYST IN THE TRANSESTERIFICATION REACTINO FOR BIODIESEL PRODUCTION UNDER SUB-CRITIC CONDTIONS

摘要

Zn/Al complex oxides prepared from Zn/Al hydrotalcite-like compound precursor were used as solid base catalyst for the transesterification reaction of rapeseed oil with methanol under sub-critical conditions. Analysis of XRD, FI-IF, TG-DTA, BET and alkalinity test by Hammett titration showed that the unique structure of precursor endowed the corresponding calcined complex oxide uniform metal ion dispersion and high alkalinity. The preparation method of this catalyst was optimized, and furthermore, the reaction parameters were investigated. Zn/Al atom ratio play a key role on the activity of the catalyst and an optimal proportion is 3.74:1 that was obtained by controlling the atom proportion in raw material. Its alcination temperature was 450°C. Using the catalyst under the optimal sub-critical reaction condition: 200 °C, 2.5MPa, 1.4%(wt) catalyst dosage, 24:1 methanol-oil-ratio and 400rpm, the conversion reached 84.25% after 90 minutes, which was better than Mg/Al complex oxides.