Studies on esterification reaction over aluminophosphate and silicoaluminophosphate molecular sieves

Abstract

Di-(2-ethylhexyl) phthalate (DEP) has been synthesized using a novel silicoaluminophosphate molecular sieve CHSAPO-1 as catalyst for the esterification reaction of phthalic anhydride with 2-ethylhexanol. The effect of some factors such as reaction temperature, the molar ratio of 2-ethylhexanol/phthalic anhydride, the amount of catalyst used, the amount of cyclohexane used and reaction time on the reaction has been investigated. The yield of di-(2-ethylhexyl) phthalate obtained was over 95% when the reaction conditions used were as follows: the molar ratio of 2-ethylhexanol/phthalic anhydride=2.8:1, the amount of cyclohexane used=25 ml/mol phthalic anhydride, the amount of catalyst used=1.1 g/mol phthalic anhydride, reaction temperature=200–220°C, and reaction time=2 h. H-CHSAPO-1 catalyst also possesses high selectivity and good activity stability for the reaction. The physical properties of the esterified product synthesized are in accordance with the literature values. For comparison, some zeolites were also tested in the esterification reactions. Butyl pentanoate has also been synthesized by the esterification reaction of pentanoic acid with n-butanol over novel aluminophosphate and silicoaluminophosphate molecular sieves. The effect of the procedures of synthesizing the molecular sieves and preparing the catalysts, and reaction conditions on the yield of the ester has been systematically investigated. The yield of the ester obtained when using aluminophosphate molecular sieves as catalysts depends upon synthesis methods of the molecular sieves (mainly template and synthesis system). The aluminophosphate and silicoaluminophosphate molecular sieves modified with Sn possess higher catalytic activity than those not modified.