Dealumination of Zeolite Beta Catalyst Under Controlled Conditions for Enhancing its Activity in Acylation and Esterification

Abstract

This work deals with the dealumination of zeolite beta (HBEA) under different conditions to optimize its catalytic performance. The dealumination was carried out either using oxalic or tartaric acid solution of different pH values or steaming up to 500˚C. The dealuminated zeolite samples were characterized using X-ray diffraction (XRD), N 2 -physisorption, ICP, 27 Al NMR and NH 3 -TPD. Their catalytic activities were studied for acylation reaction of 2-methoxy naphthalene or naphthalene with acetic anhydride and esterification of benzyl alcohol with hexanoic acid. Among the dealuminated samples examined, those treated with oxalic acid or tartaric acid at pH 2 showed high activity. The high activity can be correlated with the relative increase in the amount of strong acid sites and with the enhanced accessibility of the reactants to the active sites, which are caused by removal of extra-framework Al species on the acid treatments.

Assessment of the Catalytic Activities of Novel Brönsted Acidic Ionic Liquid Catalysts

“…A large difference in total conversion was observed when the molar ratio was changed from 1:1 to 1:2 but only a marginal increase in conversion was observed on further change of molar ratio up to 1:5. 1,2-dichloroethane was found to be the best solvent for this reaction [18]. After 2 h at 333 K, only 12.5% conversion of 2-MON and 99.3% selectivity for 1-Ac,2-MON was observed.…”

“…For comparative study, solid acid catalysts such as H-ZSM-5, H-BEA and Al-SBA-15 were prepared. Recently, it has been reported that the catalytic activity of zeolite beta can be significantly improved if it is dealuminated using oxalic acid at pH 2 [18]. Hence, in this study, H-BEA was dealuminated with oxalic acid at pH 2 (sample designated as H-BEA-pH2) and investigated in catalytic reactions.…”

“…The catalytic activities of BILs were compared with several solid acid catalysts such as ZSM-5, beta, dealuminated beta, and Al-SBA-15. H-ZSM-5 [9], H-BEA, H-BEA-pH2 [18] and Al-SBA-15 [19] were prepared as per the reported procedures.…”

Enhanced Concentration of Medium Strength Brönsted Acid Sites in Aluminium-Modified β Zeolite

“…For example, the dealuminated samples exhibited an increased activity in the acylation of naphthalene and 2-methoxynaphthalene with acetic anhydride and in the esterification of benzyl alcohol with hexanoic acid due to the relative increase in the amount of strong acid sites and the enhanced accessibility of the reactants to the active sites, which is caused by removal of extra-framework Al species during the acid treatments [3]. However, these treatments also decreased the population of acid sites of weak and particularly of medium strength and as a consequence decreased the catalytic activity in the hydroisomerization of light paraffins for some Pt supported samples [4].…”

Aplicación de la resonancia magnética nuclear (RMN) al estudio de procesos catalíticos sostenibles: transposición de Beckmann y acilación de sustratos aromáticos

“…51 Contrariamente, en la acilación de tolueno con anhídrido acético en zeolita Beta la actividad catalítica disminuye al aumentar la relación Si/Al del catalizador, lo que sugiere que ni una mayor hidrofobicidad ni una mayor acidez producen una mejora en la actividad catalítica para esta reacción. 52 Las zeolitas desaluminizadas por tratamiento con vapor o lavado con ácido son más activas en la reacción de acilación, [53][54][55][56][57] lo que se atribuye al mayor número de centros accesibles por la eliminación de Al extrarred en los tratamientos [54][55][56] o bien a la generación de mesoporos durante la desaluminización, lo que facilitaría la difusión de reactivos y productos. 57 Así pues, no existe una conclusión definitiva acerca de la influencia de la relación Si/Al en la reacción de acilación de hidrocarburos aromáticos, aunque los resultados obtenidos sugieren que zeolitas más hidrófobas son más adecuadas para llevar a cabo la reacción, al favorecer la difusión y adsorción de reactivos y la desorción de productos.…”