In situ synthesis of Co modified SAPO-5 molecular sieves and the application in quinoline hydrodenitrogenation of their NiWS supported catalysts

To improve the hydrodenitrogenation (HDN) ability of conventional Al2O3-based catalysts, SAPO-5 molecular sieves with different cobalt (Co) contents were synthesized by one-pot hydrothermal method and doped as catalyst supports. The characterization results show that the Co atoms can be effectively introduced into the skeleton of SAPO-5 molecular sieve, which improved the amount of Brønsted acid site and modulated interaction between the active metals and the support (MSI). Moreover, the introduction of Co atoms also promoted the dispersion and sulfidation of the NiW active metals, resulting in more NiWS edge active sites, which contributed to the accessibility of nitrogen-containing compounds to the active center and the hydrogenation conversion performance. Together with the synergistic effect of C-N bond breaking by matching Brønsted acid between Co-modified SAPO-5 molecular sieve and the NiWS active phase, the hydrodenitrogenation activity of the catalyst was substantially improved. Hence, the catalysts containing Co modified SAPO-5 molecular sieves exhibited higher HDN activity compared with that of containing unmodified SAPO-5 molecular sieve. Among all the catalysts investigated, the NiW/CSA-3 was found to show the highest HDN performance due to the highest number of Brønsted acid sites in the Co modified SAPO-5 molecular sieve and the maximum sulfidation degree of the active phase.