Hydrogenolysis of methyl heptanoate over Co based catalysts: Mediation of support property on activity and product distribution

Co/MgO, Co/SiO 2 and Co/Hβ catalysts were prepared by incipient wetness impregnation. The formation of MgO-CoO solid solution and MgCo 2 O 4 spinel in Co/MgO resulted in high dispersions of Co on MgO even at the low calcined temperatures and the high Co loadings. The second impregnation of Co on Co/MgO enhanced Co cations in surface/subsurface of catalysts, which led to the enlarged metallic Co particle sizes by H 2 reduction. Comparatively, the highly dispersion of Co was only observed on SiO 2 and Hβ at the low Co loadings owing to the Co δ + species of strong interactions with these supports. The solid solution/spinel and the strongly interacted Co δ + species induced the Co cations reduced at higher temperatures with obtaining the small Co particle sizes. These cases also significantly decreased the basicities of Co/MgO depending on calcined temperature and Co loadings, and increased the acidic sites of Co/SiO 2 and Co/Hβ with obtaining enhanced acidities, respectively. During hydrogenolysis processing, the basic sites of Co/MgO triggers the splitting of acyl C O bond of methyl heptanoate to form heptanal and methanol, followed by further hydrogenation of heptanal to 1-heptanol. While the acidic Co/SiO 2 and Co/Hβ induce the cracking of ether C O bond to heptanoic acid and CH 4 . Heptanoic acid intermediate is then converted into C 6 and C 7 alkanes by the parallel decarbonylation and HDO pathways, respectively. The activity and product distribution could be facilely mediated by the synergistic catalysis of metal and acid/base. Under optimal conditions, the maximal 1-heptanol and summed C 6 /C 7 alkanes yields of 55% and 89% were observed over Co/MgO and Co/SiO 2 with desire Co loadings, respectively, indicating the promising applications of these catalysts in hydrogenolysis of vegetable oils.