Abstract: The wax oil as a sulfidation agent carrying oil was firstly used for residue hydro treating catalysts at both high and low temperature presulfidation process in a commercial unit. The method avoids the switching between diesel oil and wax oil in conventional presulfidation process, thus shortening start-up time more than 20 h. The fluid distribution in catalyst bed and the activity of the catalysts presulfided by wax oil were analyzed in terms of temperature changes during catalyst wetting, reactor pressure differential, radial temperature difference, and uneven temperature distribution index of bed and compared with the conventional process using diesel as a presulfidation agent carrying oil. It is concluded that the fluid distribution is even in the wax oil presulfidation process and the presulfiding effect meets the process requirements.

Key words: residue hydrotreating, catalyst, sulfidation, wax oil, uneven temperature distribution index