Heterogeneous CaO-ZrO2 acid–base bifunctional catalysts for vapor-phase selective dehydration of 1,4-butanediol to 3-buten-1-ol

• High 1,4-butanediol conversation and 3-buten-1-ol selectivity were obtained over CaO-ZrO2 acid–base bifunctional catalysts.
• Ca2+ entered the ZrO2 crystal lattice and formed Ca–O–Zr hetero-linkages.
• The new acidic sites and basic sites were generated by introducing appropriate CaO.
• Catalytic performance is influenced by acid and base density.

A series of acid–base bifunctional CaO-ZrO2 catalysts was prepared simply by the impregnation method and evaluated for the vapour-phase dehydration of 1,4-butanediol (BDO). The effects of CaO content and calcination temperature on the catalytic properties of the CaO-ZrO2 catalysts were investigated. It was found that the catalyst with 12.5 wt% CaO and at a calcination temperature of 650 °C exhibited favorable catalytic performance and good stability for the selective dehydration of BDO to 3-buten-1-ol (BTO). The maximum BTO selectivity and BDO conversion reached 68.9% and 94.6%, respectively. The formation of by-product, THF, was markedly suppressed. These catalysts were characterized by N2 physisorption, XRD, FT-IR spectra, NH3-TPD and CO2-TPD. The results indicated that the CaO-ZrO2 catalysts showed higher basicity density and similar acidity density compared to unmodified ZrO2 due to the formation of Ca–O–Zr Hetero-linkage by CaO introduction. The catalytic performance depended on the coexistence of acidic and basic sites on the surface of catalysts.

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