Different Routes for the Hierarchization of *BEA Zeolite, Followed by Impregnation with Niobium and Application in Ethanol and 1-Propanol Dehydration

• DOI: 10.3390/catal15040340
• Publication Date: 2025-04-01T12:21:41Z
• Authors: Deborah da Silva ...; Willian Henrique ...; Ana Lívia Fernand...; Guilherme de Fran...; Matheus Ramos Silva; Pablo Teles Aragã...; José Alves Dias; Sílvia Cláudia Lo...

This study examined the hierarchical structuring of *BEA zeolite using two distinct approaches: double aluminum removal with solid ammonium hexafluorosilicate (2x-AHFS) and a solution of 0.2 M sodium hydroxide followed by 0.5 M hydrochloric acid (T-NaOH). Additionally, niobium pentoxide (Nb2O5) was impregnated at different loadings (5, 10, 15, and 20 wt.%) onto the hierarchized materials. Both treatments increased the SiO2/Al2O3 ratio and produced crystals with domains of about the same size. The hierarchization methods generated secondary mesopores and reduced the micropores in the treated HB zeolite. The solid-state NMR analysis by 27Al and 29Si indicated that the 2x-AHFS treatment increased the hydrophobic character of the zeolite, while the treatment with NaOH/HCl resulted in a less hydrophobic material. A balanced quantity of Brønsted and Lewis sites was observed for all treated zeolites. Thus, these combined physicochemical characteristics of the new catalysts may explain their superior performance in the dehydration reactions. In the case of ethanol dehydration at 230 °C, the 20 wt.% Nb2O5 supported on the T-NaOH catalyst produced an 84% conversion and 86% selectivity for ethylene (EE), with 14% diethyl ether (DEE) as the only products. Conversely, in the 1-propanol dehydration reaction, the 20 wt.% Nb2O5 supported on 2x-AHFS achieved 99% conversion, producing 99% propene.