Transalkylation of C10 Aromatics with 2-Methylnaphthalene for 2,6-Dimethylnaphthalene Synthesis over a Shape-Selective SiO2–Ni–H-Mordenite with Nanosheet Crystal

A reasonable control of the reaction pathways in the reaction system of the transalkylation of C10 aromatics with 2-methylnaphthalene was achieved over a shape-selective SiO2(II)–3.0%Ni–H-mordenite (HMOR) with nanosheet crystals in a H2 atmosphere. First, significantly improved reactivity was obtained depending on the synergistic catalysis from acid sites and metal Ni sites only on the internal surface, maybe due to a process where spillover hydrogen was converted into active hydrogen species and the latter greatly enhanced the proton-transfer efficiency in this surface catalysis. Second, based on the external surface passivation with little influence on the intrinsic excellent pore diffusibility of lamellar crystals, the side reactions of naphthalene nucleus ring opening and methylnaphthalene polyalkylation involved in large-molecule intermediates were significantly suppressed by the shape-selectivity restriction inside channels, meanwhile with remarkably enhanced dimethylnaphthalene selectivity. Both porous shape selectivity and a reasonably decreased acid strength also weakened the secondary conversion of β,β-dimethylnaphthalenes into other isomers. Therefore, an obviously improved selectivity of 2,6-dimethylnaphthalene was gained. Also, a reasonable hydrogenation catalyzed by metal Ni sites strongly resisted coke deposition, and this created a good catalytic stability of this catalyst with an impressive capability of accommodating coke. As a result, a 2-methylnaphthalene conversion of above 67.1% and a 2,6-dimethylnaphthalene yield of above 10.7% were obtained during a 100 h on stream reaction.