Influence of the phosphorus addition ways on properties of CoMo-catalysts of hydrotreating

CoMo-hydrotreating catalysts differed in the way of P addition were studied. The phosphorus was added in catalysts as follows: into the kneading paste of an alumina support, by impregnation of an alumina support before impregnation by active metals and into impregnation solution jointly with active metals. Impregnating solutions, supports and catalysts were studied by the nitrogen adsorption-desorption, UV-vis spectroscopy, RAMAN and ATR-FTIR spectroscopies, HRTEM, EDX, XPS. Catalysts were tested in hydrotreating of model feed. It was established that adding of P into the kneading paste or by impregnating of a support influenced negatively catalytic activity. Negative effect was caused by the formation of CoAl2O4 compounds and reduced portion of cobalt in the content of active phase. The addition of phosphorus into impregnation solution results in a significant increase in catalytic activity in the hydrodesulfurization of dibenzothiophene. In this case, phosphorous results in the change in the structure of active component precursors, the increase in the stacking number of the active component particles, the decrease in the interaction between active metals and a support. It was shown that the most efficient way to improve catalysts by P is to add its precursor into impregnating solution.