Zr-Incorporating SBA-15 for conversion of the ethanol–acetaldehyde mixture to butadiene

Abstract

Upgrading bio-ethanol into high value chemicals is an important issue in biomass conversion, and conversion of ethanol into butadiene is one of the most feasible methods. Here Zr-incorporating mesoporous SBA-15 (Zr–SBA-15) materials with different Si/Zr ratios were successfully synthesized by a one-pot method and were employed as catalysts for the conversion of the ethanol (EtOH)–acetaldehyde (AcH) mixture to butadiene. The textural structure and acidity of Zr–SBA-15 were investigated by using XRD, N₂ adsorption, TEM, FT-IR, UV-vis, XPS, NH₃-TPD and Py-IR, and the results of these characterizations indicated the mesoporosity of Zr–SBA-15 and confirmed the incorporation of Zr into the framework. Zr–O–Si bonds were formed by the incorporation and exhibited Lewis acidity predominantly. The influence of the Si/Zr ratio and reaction conditions (temperature, EtOH/AcH ratio and WHSV) showed that a suitable Si/Zr ratio was needed to balance the butadiene selectivity, by-product selectivity and total conversion. Amongst the prepared catalysts, Zr–SBA-15-20 achieved the best butadiene selectivity of 74.0% at a relatively low temperature (275 °C). The good catalytic performance could be attributed to the homogeneous dispersion of Zr species and Zr–O–Si bond generated by Zr incorporation. Furthermore, EtOH-TPD and AcH-TPD experiments proved the essential role of acetaldehyde addition and the well-accepted reaction pathway.