Bacterial Cellulose Supported Alumina Catalyst for Ethanol Dehydration

Abstract

An ultrafine three-dimensional nanofiber network structure of a very high porosity endows bacterial cellulose (BC) to function as support for heterogeneous catalysis. A novel catalyst of BC supported alumina (Al2O3) was developed by soaking purified BC hydrogel in aluminum nitrate (Al(NO3)3) aqueous solution, dehydration (hot air drying and freeze-drying) and calcination. The Al/BC catalysts reveal interior meso–macro porous structures with average pore diameters in the range of 17–34 nm. The catalytic activities were examined through an ethanol dehydration reaction in the gas phase at atmospheric pressure in the range of 200–400 °C. The effects of acidic metal loading and dehydration methods were investigated. Increasing Al loading from 12 to 50% resulted in a decreased surface area but an increase in pore size. At the same Al loading, the catalysts with a dehydration process by hot air drying presented higher Al concentrations on the outer surface compared with those by freeze-drying. At high temperature of 400 °C, Al/BC catalysts with 25 wt% Al loading and dehydrated by freeze drying (25Al/BC FD) and 50 wt% Al loading, dehydrated by hot air drying (50Al/BC TD) exhibited the highest ethanol conversions of 65.7–66.4% and ethylene yields of 43.26–44.24%, respectively, whereas at low temperature of 200 °C, Al/BC catalysts with 25 wt% Al loading with either dehydration method exhibited the highest diethyl ether yields of 40.02–41.60%.