Promotional effect of Co and Ni on MoO3 catalysts for hydrogenolysis of dibenzofuran to biphenyl under atmospheric hydrogen pressure

Co(Ni)/MoO3 catalysts were prepared, characterized and evaluated for the hydrogenolysis of bio-derived dibenzofuran (DBF), aiming at the understanding of the promoting effect of Co/Ni on MoO3 for high-yield production of aromatic products. All Co(Ni)/MoO3 catalysts selectively cleaved C-O bond, thus effectively transformed DBF to biphenyl (BP) at relatively moderate conditions. The experimental results from varying Mo species by adjusting the reduction temperature of MoO3 together with XPS and in-situ XRD characteristic were evident that Mo5+ species was responsible as the major active specie for the reaction. Promotional effect between Co(Ni) and Mo in Co(Ni)/MoO3 catalysts was observed, resulted from the presence of acidic Co(Ni)MoO4 species and a large number of Mo5+ species both of which were created local to the Co(Ni)-O-Mo interface, as can be characterized by in-situ XRD, XPS, H-2-TPR, NH3 -TPD, insitu FT-IR, Raman and TEM. The trend of the initial reaction rate follows: MoO3 (0.18 mu mol.g(cat)(-1).s(-1)) < Ni/MoO3 (0.26 mu mol-g(cat)(-1).s(-1)) < Co/MoO3 (0.29 mu mol.g(cat)(-1).s(-1)), corresponding to the decreasing activation barrier. And the best catalytic activity was observed for the 100% yield of BP over Co/MoO3. A possible mechanism, including Co(Ni) facilitated reduction of Mo6+ to Mo5+ and Co (Ni) enhanced formation of acidic sites, is proposed to be responsible for the high activity in Co(Ni)/ MoO3 catalysts. (C) 2020 Elsevier Inc. All rights reserved.