Abstract: After the original adsorbent in the 600 kt/ap-xylene adsorption and separation unit was replaced with adsorbent RAX-4000, the purity of p-xylene product couldnot reach 99.8%, the impurity contentof m-xylene and o-xylene was high,and the single-pass yield was only about 96%, which did not meet the expected goal. Compared with the initial process parameters of the original adsorbent,the operation of the adsorption column was analyzed by using the pump-fed semi-logarithmic coordinate spectrum,and the reasons of high impurity contentof m-xylene and o-xylene in adsorbent performance, adsorbent raw material impurity content, adsorbent water injection volume, and the adsorption column system, etc.were judged tobe the leakage of the rotary valve. After taking optimization measures, the yield of para-xylene increased from 96% to 96.63%, an increase of 0.63 percentage point, which effectively improved the operation level of the plant.

Key words: p-xylene, RAX-4000, rotary valve, adsorbent