Research on Additives Assisted Catalytic Cyclo-Dehydration of 1, 4-Butanediol to Tetrahydrofuran in Near-Critical Water

Abstract

We herein report the cyclo-dehydration of 1,4-butanediol (BD) assisted with additives to form tetrahydrofuran (THF) in near-critical water (NCW).Three additives including Fe2(SO4)3,ZnSO4 and NaHSO4 were screened. Effects of various experimental parameters such as temperature (260-340°C), time (60-180min), reactant/water ratio (r/w, 1:10-1:40) and pressure (15-25MPa) on the yield of THF were examined. Without the presence of additives, the results showed that increasing temperature favored the cyclo-dehydration of BD to form THF. The maximum yield (52.61 wt. %) was obtained at temperature of 340°C and time of 180 min. With the presence of additives, at temperature range of 260~300°C and time range of 60~130min, all the additives selected can promote the cyclo-dehydration of BD to yield THF. However, with further increasing temperature and time, the additives would suppress the formation of THF. The catalytic activity toward the production of THF in the order of Fe2(SO4)3> ZnSO4> NaHSO4. The maximum yield of THF assisted with Fe2(SO4)3 could reach as high as 59.85 wt. % at 320°C, 120 min. Large reactant/water ratio would not benefit the yield of THF because of the dilution of additive. Increasing the pressure will slightly increase the yield of THF. Base on experimental results, a possible reaction mechanism and pathway of dehydration of BD was proposed in NCW.