Methyl esters(biodiesel)were produced by the transesterification of cottonseed oil with methanol in the presence of solid acids as heterogeneous catalysts.The solid acids were prepared by mounting H_(2)SO_(4) on TiO_(2)·nH_(2)O and Zr(OH)4,respectively,followed by calcining at 823K.TiO_(2)-SO_(4)^(2-)and ZrO_(2)-SO_(4)^(2-)showed high activity for the transester-ification.The yield of methyl esters was over 90%under the conditions of 230℃,methanol/oil mole ratio of 12:1,reac-tion time 8 h and catalyst amount(catalyst/oil)of 2%(w).The solid acid catalysts showed more better adaptability than solid base catalysts when the oil has high acidity.IR spectral analysis of absorbed pyridine on the samples showed that there were Lewis and Brønsted acid sites on the catalysts.
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