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Vapor-phase catalytic dehydration of 1,4-butanediol (1,4-BDO) was investigated over rare earth metal oxide (RE2O3) catalysts to produce 1,3-butadiene (BD). Among eight RE2O3, Yb2O3 showed the highest catalytic activity to produce BD via an intermediate 3-buten-1-ol (3B1OL). Hydrothermal (HT) aging of precursor precipitate of Yb2O3 greatly enhanced the catalytic activity and the selectivity to 3B1OL of the resulting Yb2O3 catalyst. It was confirmed that the morphology of Yb2O3 and the catalytic activity varied with the HT conditions. Hydrothermally aged Yb2O3 reduced the formation of propylene, a decomposed product of 3B1OL, even at high temperatures above 400 °C. HT-aged Yb2O3 followed by calcination at 700 °C showed excellent catalytic activity in the dehydration of 1,4-BDO with the highest BD productivity of 34.6 mol kgcat−1 h−1 and a high BD yield of 97.4% at 450 °C.

The vapor-phase dehydration of 1,3-butanediol (1,3-BDO) to produce 1,3-butadiene (BD) was investigated over yttrium zirconate, Y2Zr2O7, which was prepared through a hydrothermal aging process. 1,3-BDO was initially dehydrated to three unsaturated alcohols, namely 3-buten-2-ol, 3-buten-1-ol, and 2-buten-1-ol, followed by the further dehydration to BD. The catalytic activity of Y2Zr2O7 was strongly dependent on the calcination temperature. Furthermore, the reaction temperature was one of the important factors to produce BD efficiently: the selectivity to BD was increased with increasing reaction temperature up to 375 °C, while coke formation led to catalyst deactivation together with by-product formation at higher temperatures. Y2Zr2O7 catalyst calcined at 900 °C showed a high BD yield of 95% at 375 °C and a time on stream of 10 h.

The aim of this work is to develop an effective catalyst for the conversion of butanediols, which is derivable from biomass, to valuable chemicals such as unsaturated alcohols. The dehydration of 1,4-, 1,3-, and 2,3-butanediol to form unsaturated alcohols such as 3-buten-1-ol, 2-buten-1-ol, and 3-buten-2-ol was studied in a vapor-phase flow reactor over sixteen rare earth zirconate catalysts at 325 °C. Rare earth zirconates with high crystallinity and high specific surface area were prepared in a hydrothermal treatment of co-precipitated hydroxide. Zirconates with heavy rare earth metals, especially Y2Zr2O7 with an oxygen-defected fluorite structure, showed high catalytic performance of selective dehydration of 1,4-butanediol to 3-buten-1-ol and also of 1,3-butanediol to form 3-buten-2-ol and 2-buten-1-ol, while the zirconate catalysts were less active in the dehydration of 2,3-butanediol. The calcination of Y2Zr2O7 significantly affected the catalytic activity of the dehydration of 1,4-butanediol: a calcination temperature of Y2Zr2O7 at 900 °C or higher was efficient for selective formation of unsaturated alcohols. Y2Zr2O7 with high crystallinity exhibits the highest productivity of 3-buten-1-ol from 1,4-butanediol at 325 °C.

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