Catalytic dehydration of 1,2-butanediol to 1,3-butadiene over CsH2PO4/SiO2

Silica-supported alkali metal phosphate catalysts were investigated for the vapor-phase dehydration of 1,2-butanediol (1,2-BDO) to produce 1,3-butadiene (BD). Among the alkali metal phosphates explored, a silica-supported CsH2PO4 (CsH2PO4/SiO2) was found to be the most efficient catalyst. Several parameters, such as the Cs/P ratio, reaction temperature, and contact time, significantly affected the BD formation. The highest BD yield of 59.6% was achieved over 10CsH2PO4/SiO2 at 411 °C, with butanal and butanone as the main side products. Based on the conversion-selectivity plots at 411 °C, a possible reaction pathway for BD formation was proposed. In addition, the dehydrations of 1,2-epoxybutane and 2-buten-1-ol were also performed to verify the reaction sequence. The epoxidation of 1,2-BDO to 1,2-epoxybutane, which is one of the initial steps of the stepwise formation of BD, proceeded via an acid-base concerted mechanism. This work is the first report on the dehydration of 1,2-BDO to produce BD efficiently.