Probing the synergistic effect of Mo on Ni-based catalyst in the hydrogenation of dicyclopentadiene

Mo promoted Ni/γ-Al₂O₃ catalysts were synthesized by an incipient wetness co-impregnation method. The micro-structure, surface composition and adsorption characteristics of these catalysts were investigated by N₂ adsorption-desorption isotherms, XRD, HRTEM, XPS, TPR and dicyclopentadiene-TPD. The hydrogenation of dicyclopentadiene (DCPD) to endo-tetrahydrodicyclopentadiene (endo-THDCPD) was selected to evaluate the catalytic performance. The results showed Mo species improved dispersity of nickel oxide on the support surface and inhibit formation of spinel NiAl₂O₄. The nickel oxide could be reduced to Ni nanoparticles at relatively lower temperature because of its excellent dispersity and weakened interaction with the support. Meanwhile, the aggregation of metallic Ni on catalysts were markedly inhibited with the increasing of Mo content. Mo species also changed the adsorption mode of DCPD on Ni-based catalysts, and hence improved DCPD adsorption strength and capacity on catalysts and further changed hydrogenation mechanism of DCPD. The catalytic properties of NiMo_X/γ-Al₂O₃ catalysts showed that the hydrogenation activity was increased by adding Mo to Ni-based catalyst within limits. When the ratio of Mo to Ni was 0.2, the NiMo_0.2/γ-Al₂O₃ catalyst displayed the highest activity (TOF = 134.2 h⁻¹) and the best selectivity (99.7%). Compared with Ni/γ-Al₂O₃ catalyst, the hydrogenation time reduced from 6 h to 3 h and the amount of by-product C₅ fraction significantly decreased from 2.4% to 0.3%.