CoP and Co2P were prepared by temperature-programmed reduction of the mixtures of Co(OH)(2) and H3PO3 with stoichiometric P/Co ratios, but their surfaces were still enriched in phosphorus. Based on the product distributions of the hydrodesulfurization (HDS) of dibenzothiophene (DBT), 1,2,3,4-tetrahy dro-dibenzothiophene (TH-DBT), and 1,2,3,4,4a,9b-hexahydro-dibenzothiophene (HH-DBT), a reaction network of DBT HDS was proposed and the mechanisms of the cleavage of different CAS bonds in DBT and its hydrogenated intermediates were discussed. CoP was much more active and more nitrogen tolerant than Co2P, which make it a promising HDS catalyst. The HDS reactions over CoP and Co2P followed a pseudo-first-order kinetics and a pseudo-zero-order kinetics, respectively. Piperidine strongly inhibited the hydrogenation/dehydrogenation reactions and the direct desulfurization of DBT, but its inhibition on the desulfurization of TH-DBT and HH-DBT were less pronounced. The active surfaces of CoP and Co2P in HDS reactions can be cobalt phosphosulfide phases. (c) 2020 Elsevier Inc. All rights reserved.