Low-temperature selective transformation of diethylbenzene to isobutane and cyclohexanes via the interplay of Pt and acid centres in Pt/H-BEA zeolites

• Published in: Journal of catalysis Vol. 407; pp. 186 - 197
• Main Authors: Kaucký, Dalibor, Pilař, Radim, Kukula, Pavel, Bartáček, Jan, Morávková, Jaroslava, Sazama, Petr
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01.03.2022
• Subjects: Beta zeolite (BEA); Diethylbenzene; Hydrocracking; Hydrogenation; Hydroisomerization; Organotemplate-free Al-rich Beta; Paring reaction; Paring reaction; Hydrocracking; Organotemplate-free Al-rich Beta; Hydroisomerization; Diethylbenzene; Beta zeolite (BEA); Hydrogenation
• ISSN: 0021-9517; 1090-2694
• DOI: 10.1016/j.jcat.2022.01.019

[Display omitted] •The low-temperature hydrotransformation of aromatics over Pt/H-zeolites is presented.•Selectivity is controlled by the susceptibility of the individual CC bonds to cracking.•The CC bonds in the ring and low branched alkyl chains practically do not crack.•The CC bonds most prone to cracking selectively undergo type A β scission.•Minimal consecutive and parallel reactions enable high selectivity at high conversions. The hydrocracking of aromatic hydrocarbons on bifunctional catalysts comprises parallel reactions that provide a wide distribution of products and byproducts. This work demonstrates on diethylbenzene (DEB) hydrotreatment that Pt/H-Al-rich *BEA zeolite catalysts can significantly reduce the hydrocracking temperature so that only the selected reaction mechanisms prevail in the process, providing high selectivity. The interplay of high activity of Pt clusters in hydrogenation/dehydrogenation and Brønsted acid sites in acid-catalysed reactions allows selective hydrocracking of DEB to isobutane and methylcyclopentane by the paring reaction at 200 °C. Low-temperature hydrocracking consists of hydrogenation of DEB to diethylcyclohexane, its rapid skeletal hydroisomerization to C10 branched alkylcycloalkanes followed by their A type β scission providing isobutane and methylcyclopentane with 80% selectivity at 68% DEB conversion, practically without subsequent reactions of the formed products. The reactive CC bond in tribranched alkylcycloalkanes selectively undergoes A type β scission, while more stable CC bonds in less or unbranched hydrocarbon chains or rings do not crack to a substantial extent at low temperatures. The study demonstrates that the low-temperature hydrotreatment of aromatics over highly active catalysts allows controlling the involvement of individual reaction mechanisms in the complex hydrocracking process and provides tailored selectivity.