Design of selective hydrocracking catalysts for BTX production from diesel-boiling-range polycyclic aromatic hydrocarbons

• Published in: Applied catalysis. A, General General, 2017-10, Vol.547, p.12-21
• Main Authors: Shin, Jaeuk, Oh, Youngseok, Choi, Yeseul, Lee, Jihye, Lee, Jung Kyoo
• Format: Article
• Language: English
• Subjects: Alkylbenzenes; Benzene; BTX; Catalysis; Catalysts; Dealkylation; H-Beta; H-ZSM-5; Hybrid zeolite; Hydrocracking; Hydrogenation; Nickel; Polycyclic aromatic hydrocarbons; Sulfide metals; Tetralin hydrocracking; Toluene; Zeolites
• ISSN: 0926-860X; 1873-3875
• DOI: 10.1016/j.apcata.2017.08.019

[Display omitted] •Design of hydrocracking catalysts for Polyaromatics conversion into BTX is studied.•Metallic functions in the hydrocracking catalysts should have a moderate hydrogenation activity.•Zeolitic functions with a high dealkylation activity is preferred for high per-pass yield of BTX.•Hence, sulfide-metals/hybrid zeolites (H-Beta+H-ZSM-5) catalyst show promise for high BTX yield. Various metallic components (Ni, NiSn, NiW-S, CoMo-S and NiMo-S) with different hydrogenation (HYD) activities were supported on H-Beta or hybrid zeolites (BZ(x), where x denotes the weight percentage of H-ZSM-5 in the physical mixture of H-Beta and H-ZSM-5). These bifunctional catalysts were applied to the hydrocracking (HYC) of tetralin in a fixed-bed down-flow reactor at 4MPa as a model reaction for polycyclic aromatic hydrocarbon (PAH) conversion to high-value benzene, toluene, and xylenes (BTX). From the HYC of tetralin over the series of metals/H-Beta catalysts, it was found that CoMo-S/H-Beta and NiMo-S/H-Beta, whose metallic components show moderate activities in the HYD of tetralin, exhibit higher BTX yields than the other catalysts whose metals have excessively high or low HYD activities. However, these catalysts show limited BTX yield (∼47.3wt% at 425°C) owing to the large coproduction of alkylbenzenes other than BTX. When metals with moderate HYD activities are supported on the hybrid zeolites, the BTX yield is significantly enhanced by the effect of H-ZSM-5 in the dealkylation of alkylbenzenes into BTX. NiMo-S/BZ(10) provides a BTX yield of 54.3wt% and a total 1-ring aromatic yield as high as 63.8wt% (corresponding to 94.4% of the theoretical maximum of 67.6wt%) at 425°C. Therefore, the NiMo-S/BZ(10) catalyst, where the metallic and acidic functions and structural properties of the zeolite are well balanced, show promise as an HYC catalyst for the hydroconversion of PAHs into high-value BTX mixtures.