Kinetics and mechanism of acetalisation of furfural to furfural diethyl acetal with Ni-Al layered double hydroxides containing Lewis acid sites

Abstract

The nitrate form of Ni-Al layered double hydroxide (denoted as Ni-Al-NO3-LDH) and the corresponding carbonate form (denoted as Ni-Al-CO3-LDH) were tunably fabricated by the hexamethylenetetramine hydrolysis method. A catalytic behaviour investigation proved Ni-Al-CO3-LDH to be an ineffective catalyst, while for Ni-Al-NO3-LDH excellent catalytic activity and reusability were obtained, in the acetalisation of furfural to furfural diethyl acetal. Characterisation and analysis revealed that the appearance of Lewis acid sites in Ni-Al-NO3-LDH was responsible for its excellent catalytic performance. The acquired kinetic parameters confirmed that this reaction was a first-order process and the apparent activation energy was 36.28 kJ mol-1, which is in reasonable agreement with the theoretical result of 38.57 kJ mol-1. Additionally, apart from the typical Brønsted acid catalytic mechanism, a possible Lewis acid catalytic mechanism was probed theoretically.