Genesis of Strong Brønsted Acid Sites in WZr-KIT-6 Catalysts and Enhancement of Ethanol Dehydration Activity

Abstract

Using a one-pot synthesis technique, tungsten and zirconium were simultaneously incorporated into an ordered mesoporous KIT-6 framework. A series of such materials, denoted WZr-KIT-6, were synthesized with W and Zr loadings ranging from 0 to 10 mol % each. At sufficiently high Zr loadings, ssNMR spectra of neat as well as pyridine-adsorbed catalyst confirm that the fresh WZr-KIT-6 materials exhibit both Lewis and Bronsted acid sites of high strength, resulting in correspondingly high ethylene yields during ethanol dehydration. Such yields surpass those observed on Wx-KIT-6 and Zry-KIT-6 materials with W and Zr loadings identical with those of WxZry-KIT-6. Interestingly, air regeneration of the spent WZr-KIT-6 catalyst further enhances ethanol dehydration activity, with ethylene yields approaching those reported with HZSM-5 and SAPO-34 catalysts under similar operating conditions. This enhancement correlates with ssNMR evidence of the formation of additional strong Bronsted acid sites following the regener...