Catalytic dehydration of ethanol to ethylene and diethyl ether over alumina catalysts containing different phases with boron modification

The catalytic ethanol dehydration of ethanol over the solvothermal-derived alumina catalysts was investigated in this study. First, alumina catalysts were synthesized by the solvothermal methods to obtain three different phase composition of alumina catalysts including -phase (G-Al), -phase (C-Al) and equally mixed - phases (M-Al). Then, all catalysts were modified with boron (G-Al-B, C-Al-B and M-Al-B). It was found that the boron modification increased the amounts of total acid sites and the ratio of weak to strong acid sites (WSR). The catalytic activity and product selectivity of six catalysts via catalytic ethanol dehydration at 200, 300, and 400 degrees C were measured. For all catalysts, it revealed that ethanol conversion increased with increased temperatures from 200 to 400 degrees C. At 200-300 degrees C, the unmodified catalysts tended to exhibit the higher catalytic activity than the boron-modified catalysts. However, at high temperature (400 degrees C), the boron modification tended to increase the catalytic activity, especially for the M-Al-B catalyst (complete ethanol conversion at 400 degrees C). Considering ethylene production, the M-Al-B exhibited the highest ethylene yield among other catalysts with 92% at 400 degrees C. For diethyl ether, it was observed that the M-Al catalyst gave the highest diethyl ether yield of 57% at 300 degrees C. This is because the boron modification increased the amounts of total acid sites, which can promote the production of ethylene, while this is not preferable for diethyl ether production, which is favored by weak acid sites.