The fast deactivation caused by serious formation of coke is a major challenge in catalytic isomerization of endo-tetrahydrodicyclopentadiene (endo-THDCPD) into exo-tetrahydrodicyclopentadiene (exo-THDCPD) over the HY zeolite. In order to suppress the coke formation for the isomerization process, the conventional HY zeolite was modified with Pt at 0.3 wt %. Then, the hydroisomerization of endo-THDCPD into exo-THDCPD was evaluated over a fixed-bed reactor. The catalytic stability of Pt/HY was greatly enhanced in comparison to that of the HY zeolite. The Pt/HY catalyst provided 97% endo-THDCPD conversion and 96% selectivity for exo-THDCPD without deactivation after 100 h. Moreover, the formation mechanism of coke on the HY zeolite during the isomerization process was proposed based on the results of the coke analysis. It was indicated that the coke was generated from the oligomerization and condensation of olefin species, which originated from the β-scission reaction or hydride transfer reaction of intermediates. The lower coke formation over Pt/HY was attributed to the lower amount of coke precursors, which could be hydrogenated by activated H2 over Pt sites. Therefore, Pt on Pt/HY and H2 were two crucial factors in efficiently enhancing the catalytic stability of the HY zeolite for this isomerization reaction.
Nan Jiang,Xiaopo Niu,Danni Liu,Kaige Zhang,Zhen Guo,Yue Qin,Wenli Zhao,Xiangwen Zhang,Qingfa Wang
Designing bifunctional catalysts for efficient hydroisomerization of phenanthrene to alkyl-adamantane is a great challenge for producing high-density fuels. Herein, a bifunctional Pt catalyst was fabricated by developing hierarchical H-MSY-T zeolites with an NOA-co strategy. The influence of different mesopore template agents on the hierarchical structure of H-MSY-T zeolite was investigated. Effective regulation of pore structure and acid distribution of zeolites was achieved by adjusting the templating agents. The block copolymer P123 promoted the formation of mesoporous structures via self-assembly with a large mesopore centered at 8 nm. Large mesoporous structure and suitable distribution of Bronsted acid boosted the hydroisomerization of phenanthrene. The highest alkyl-adamantane yield of 45.9 wt% was achieved on the Pt/MSY-P1 catalyst and a reaction network of hydroisomerization was proposed. This work provides guidance to design highly selective bifunctional catalysts for the one-step hydroconversion of tricyclic aromatic hydrocarbons into high-density fuels.
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