Continuous dehydration of ethanol to diethyl ether over aluminum phosphate–hydroxyapatite catalyst under sub and supercritical condition

The activity of non-stoichiometric aluminum phosphate–hydroxyapatite for continuous dehydration of ethanol to diethyl ether (DEE) under sub and supercritical condition was investigated. The catalysts were characterized, using different methods viz., XRD, FT-IR, BET, TGA, EDX, Hammett indicators and amine titration. A face-centered composite design was used to investigate the effect of temperature, pressure, and ethanol flow rate on the catalyzed ethanol dehydration. Response surface methodology was used for optimization. Under the optimum conditions of ethanol flow rate of 0.17 mL min−1 (WHSV = 1.01 h−1), 340 °C, and 200 bar, the DEE yield, selectivity, ethanol conversion, and liquid selectivity reached above 75%, 96%, 78%, and 97%, respectively. The time-on-stream of the catalyst for DEE synthesis showed that the catalyst remained stable and active without any appreciable loss in activity and selectivity for the time duration of 41 h.