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n-Heptane hydroconversion over nickel-loaded aluminum- and/or boron-containing BEA zeolites prepared by recrystallization of magadiite varieties

R. Mihályi, Magdolna and Lónyi, Ferenc and Beyer K., Hermann and Szegedi, Ágnes and Kollár, Márton and Pál-Borbély, Gabriella and Valyon, József (2013) n-Heptane hydroconversion over nickel-loaded aluminum- and/or boron-containing BEA zeolites prepared by recrystallization of magadiite varieties. Journal of Molecular Catalysis A: Chemical, 367. pp. 77-88. ISSN 1381-1169

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Abstract

Phase-pure [Al]BEA and [Al,B]BEA zeolites, prepared by solid-state recrystallization of synthetic aluminum-containing magadiites and conventionally synthesized [B]BEA, were tested, after ion exchange with nickel, as bifunctional catalysts for hydroconversion of n-heptane. The reducibility of nickel ions incorporated into BEA zeolites by ion exchange was investigated by temperature-programmed reduction (TPR). The acidity of the samples was characterized with strong (pyridine (Py), ammonia (NH3)) and weak (nitrogen) bases. The adsorbed bases were studied by transmission FT-IR (Py), diffuse reflectance infrared Fourier-transform (DRIFT) spectroscopy (N2), and temperature-programmed ammonia evolution (TPAE, NH3). Over Ni/H-[B]BEA the reactants were completely converted via fast hydrogenolysis, whereas this reaction pathway plays only a negligible role in the hydroconversion over Ni/H-[Al]BEA and Ni/H-[Al,B]BEA zeolites. Boron-containing BEA zeolites were less active catalysts than the boron-free catalyst in the principal unimolecular hydroconversion reactions. However, incorporation of boron into the framework of BEA zeolite results in a considerable selectivity shift towards isomerization. Results suggest that the acid strength of bridged hydroxyls, probed with weak (N2) and strong basis (pyridine), was found to be similar in the boron-free and boron-containing BEA samples. The decrease in the isomerization rate and the increase of the apparent activation energy upon incorporation of boron may be attributed to the decrease in the heat of n-heptane adsorption.

Item Type: Article
Uncontrolled Keywords: [Al,B]BEA-type zeolites; Acidity; Adsorption heat; Bifunctional Ni/H-BEA; n-Heptane hydroconversion
Subjects: Q Science / természettudomány > Q1 Science (General) / természettudomány általában
Q Science / természettudomány > QD Chemistry / kémia
Q Science / természettudomány > QD Chemistry / kémia > QD02 Physical chemistry / fizikai kémia
Depositing User: Dr. Magdolna R. Mihályi
Date Deposited: 22 Mar 2013 10:03
Last Modified: 23 Jul 2013 12:00
URI: http://real.mtak.hu/id/eprint/4443

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