Engineering ultrafine Cu nanoparticles supported on zeolites via solvent-free inter-zeolite transformation for bioethanol dehydrogenation

Abstract

Although Cu nanoparticles (Cu-NPs) supported on zeolites have been widely used in sustainable catalysis, they still suffer from accelerated deactivation due to metal sintering. To overcome this problem, the inter-zeolite transformation (IZT) under solvent-free conditions offers advantages in the redispersion of Cu confined inside zeolite structures, ultimately resulting in enhanced catalytic activity. Herein, we report the benefits of the solvent-free IZT, which functions not only in transforming the original zeolite framework (FAU) to the other zeolites (BEA) but also redispersing simultaneously the aggregated Cu-NPs on FAU surfaces into highly dispersed Cu-NPs on the transformed BEA (BEA-IZT) structure. The PXRD patterns illustrate that FAU has been completely transformed into BEA. The Cu clusters are redispersed on the BEA-IZT with their size of ~2.43 nm, eventually facilitating the formation of uniform metallic Cu, confirmed by time-resolved X-ray absorption near edge spectroscopy (TR-XANES). Interestingly, the highly dispersed Cu-NPs deposited on the transformed BEA zeolite promote superior catalytic dehydrogenation of renewable feedstock, bioethanol, to acetaldehyde, providing ethanol conversion, acetaldehyde selectivity, and yield up to approximately 90, 70, and 60%, respectively. This first example opens up the perspective of material design by the solvent-free IZT process for redispersing sintered metal particles to produce the highly reactive catalyst for sustainable ethanol dehydrogenation.