Hierarchical leaf-like alumina-carbon nanosheets with ammonia water modification for ethanol dehydration to ethylene

Abstract

A hierarchical leaf-like alumina-carbon nanosheet catalyst was prepared by a chelate-assisted co-assembly method to improve the catalytic behavior of ethanol dehydration reaction, based on the chemical etching effect of ammonia water. The uniformly dispersed leaf-like nanosheet structure possessed a relatively large specific surface area and exposed more active sites, which could promote the ethanol dehydration reaction. This catalyst was promising to obtain a higher catalytic behavior (conversion of 98.3 % and ethylene selectivity of 97.0 %) than the sample without ammonia water modification (conversion of 63.2 % and ethylene selectivity of 46.7 %) at 450 ℃. The addition of ammonia water played an essential role in influencing the formation of the leaf-like nanosheet structure and the generation of Brönsted acid active sites, which remarkably promoted the proceed of ethanol dehydration. Importantly, a direct relationship was observed between the nanosheet thickness and the alumina content. The best catalytic activity with TOF of 361.8 h−1 was obtained when the Al loading of 13.9 wt%, attributed to the suitably balanced weak/moderate acidic active sites ratio of ∼ 4.37. In-situ FTIR spectra of ethanol dehydration reaction clearly confirmed that ethanol was first converted to the intermediate product diethyl ether and then subsequently decomposed to ethylene at a higher temperature. The catalyst also maintained a good recyclability upon time on stream of 144 h at 450 ℃. This work provides an alternative way of developing non-noble metal catalyzing ethanol dehydration to ethylene.