Direct conversion of ethanol to 1,3-butadiene over Zn and La grafted on defect-induced zeolite beta

Abstract

Direct bioethanol conversion into renewable 1,3-butadiene (1,3-BD) is an attractive approach toward biorefineries. The dependency on fossil-based chemicals will be minimized by using bioethanol as an alternative source. Here, the Zn-La-De-β catalyst composed of Zn and La grafted into dealuminated zeolite beta is reported for ethanol conversion to 1,3-BD. Zn and La sites were grafted into silanol nests created by the dealumination of beta zeolite to produce Zn-De-β, La-De-β, and Zn-La-De-β. These prepared catalysts were then evaluated for the conversion of bioethanol to 1,3-BD. Zn-De-β was more active for the dehydrogenation of ethanol to acetaldehyde; in contrast, La-De-β was active for 1,3-BD formation. The catalyst Zn-La-De-β, having both active sites, was most active for 1,3-BD formation and resulted in 50% C-mol selectivity for 1,3-BD at an optimized reaction temperature of 325 °C. Various characterization techniques, including XRD, XPS, CO₂-TPD, and Py-IR, realized the location and nature of active centers. This study highlights the role of each metal site in the selective production of renewable 1,3-BD. 1.38 g_1,3-BD g_cat⁻¹ h⁻¹ was the highest productivity of 1,3-BD observed at a temperature of 325 °C and WHSV of 9.7 h⁻¹.