Catalysts for the non-oxidative dehydrogenation of ethanol supported by WO3-based micro-mesoporous composites

Abstract

Much work has been done on synthesizing materials that enhance the conversion and selectivity of catalysts in industries by combining the stability and acidity benefits of zeolites with those of mesoporous materials. As an alternative to conventional copper oxide-supported catalysts, this study describes the synthesis of novel WO₃-supported micro-mesoporous composites made of AlSBA-15 (Si/Al = 5) and various zeolites types, either HZSM-5 (MFI) or HY (FAU), using a simple deposition technique. These composites are effective catalysts for the non-oxidative dehydrogenation of ethanol to acetaldehyde. Several spectroscopic techniques were used to determine the impact of employing different zeolite types on the physicochemical characteristics of the produced micro-mesoporous composites. Additionally, their catalytic performances were evaluated when compared to the non-oxidative dehydrogenation of ethanol, utilizing a flow system to produce more valuable products. Several spectroscopic methods demonstrated that this simple synthesis approach successfully included the used zeolite-type seeds into the matrix bulk of the AlSBA-15(5). In contrast to their constituent components, the synthesized WO₃-supported micro-mesoporous catalysts exhibit finer dispersion, basicity, a newly formed peak in the XPS O1S spectra due to W–O–W bridging oxygens, and comparatively higher amounts of isolated tetrahedrally monomeric WO₄²⁻ (WO) species to oligomeric ones. The type of zeolite used in the micro-mesoporous composite's synthesis has a significant impact on composites' catalytic performance. With a selectivity of around 96 %, the WO₃-supported micro-mesoporous composite catalyst using HZSM-5 as the zeolite component demonstrates exceptional selectivity for the non-oxidative dehydrogenation of ethanol only to acetaldehyde. On the other hand, with an ethanol conversion of about 85 % at 450 °C, the WO₃-supported micro-mesoporous composite catalyst used in the HY zeolite type exhibits the highest catalytic activity in terms of conversion. The catalyst's basicity, the presence of W–O–W bridges, and the comparatively higher amounts of isolated tetrahedral monomeric to oligomeric WO₄²⁻ species all had a significant impact on the ethanol conversion and product selectivities during the non-oxidative dehydrogenation of ethanol.