Abstract: Using benzene and ethanol as solvents, Soxhlet extraction was used to pretreat the spent catalyst for FCC gasoline hydrodesulfurization. Physical adsorption analyzer, carbon and sulfur analyzer, thermogravimetric analyzer, TPO-MS, SEM-EDS were used to characterize the deactivation catalysts from different bed layers, in order to determine the best regeneration conditions and replacement plan. The results showed that the main reasons for deactivation of the catalysts were arsenic poisoning and carbon deposition, the carbon deposition was the most serious in the middle and lower of the reactor along with the direction of stream, the amount of carbon deposited on the top and bottom of the reactor is equal. It is necessary to eliminate the serious arsenic poisoning catalyst at the top and to be replaced by fresh catalyst in the replacement plan, and to prolong the calcination time at low temperature less than 200 ℃ when the spent catalyst is regenerated, and finally to control the regenerating temperature between 400 ℃ and 450 ℃. The results showed that the overall performance of the catalyst regenerated at 450 ℃ was the best, the desulfurization rate was 92.6% , the selectivity was 76.5% , and the activity was restored to 98% of the fresh catalyst.

Key words: hydrodesulfurization, deactivated catalyst, coke deposition, arsenic poison, regeneration