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, 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 ofsolvent-free IZT, which not only transforms the original zeolite framework (FAU) into other zeolites (BEA) but also simultaneously redisperses 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 BEA-IZT with a size of ∼2.43 nm, eventually facilitating the formation of uniform metallic Cu, as 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, achieving ethanol conversion, acetaldehyde selectivity, and yield of approximately 90, 70, and 60%, respectively. This first example opens up the perspective of material design through the solvent-free IZT process for redispersing sintered metal particles to produce a highly reactive catalyst for sustainable ethanol dehydrogenation.