Selective synthesis of 1,3-butadiene by vapor-phase dehydration of 1,4-butanediol over cerium oxide catalyst

Dehydration of biomass-derived 1,4-butanediol (1,4-BDO) is an attractive approach to synthesizing 1,3-butadiene (BD), which is a useful monomer for various polymers and currently produced via naphtha cracking. Cerium oxide (CeO2) with weak acid-base bifunctionality promoted the dehydration of 1,4-BDO to BD in 66% yield with 80% selectivity under the optimized conditions. The selectivity given by the CeO2 catalyst was influenced by the calcination temperatures, since the acid-base bifunctionality and reducibility of CeO2, which were examined temperature-programmed analyses, were altered. In stark contrast, the catalysts with strong acid sites exemplified by SiO2-Al2O3 and H-type mordenite (H-MOR) were inappropriate for this reaction since they produced tetrahydrofuran as a major product. The control experiments using a set of substrates suggested that 3-butene-1-ol was the main intermediate in the 1,4-BDO-to-BD dehydration, and its isomer of 2-butene-1-ol was also involved in the reaction but rather triggered the undesired side reactions to form butyraldehyde and ketones.