Study On Nitrogen And Chlorine Removal Process By Adsorption From Naphtha

The low nitrogen and chlorine compounds content in naphtha are the requirement of long-term operation and work safety in catalytic reforming and ethylene unit. In this paper, the adsorbent of denitrogenation and the one of dechlotination was prepared by impregnation and coprecipitation, respectively. The nitrogen and chlorine removal capacity of the two adsorbents in naphtha was studied, and the reaction conditions were optimized.13X molecular sieve was impregnated in a concentration of 1 mol/L phosphoric acid with 1:4 ratio for 24h, then the nitrogen removal rate could reach to 94.6%, and the average nitrogen content in refined oil less than 0.27μg/g. The optimized condition for the denitrogenation process is at room temperature, naphtha space velocity of 6h-1. The nitrogen content in refined oil could be less than 2.5μg/g in 25h. The effective Oil/Agent ratio of 13X molecular sieve is 190.3. By purging nitrogen in 100℃can realize the cycle of adsorption/desorption. The long-term operation would come true by regeneration treatment.When the mole ration of Al:Mg is 4:9, the aluminum magnesium silicate has good chlorine removal capacity. The chlorine removal rate of it could reach to 88.9%, and the chlorine content in refined oil is 0.72μg/g. The optimized condition for the dechlorination process is at room temperature, and naphtha space velocity of 6h-1.The effective Oil/Agent of aluminum magnesium silicate is 186.7. By purging nitrogen in 100℃, it can realize the cycle of adsorption/desorption. The long-term operation would come true by regeneration treatment.Based on the research of denitrogenation and dechlorination process, the composite adsorbent bed of naphtha was studied. Under the condition that room temperature and naphtha space velocity of 6h-1, nitrogen and chlorine in naphtha could be reduced to less than 2.5μg/g, 3.0μg/g, respectively. The analysis of naphtha before and after adsorption showed that denitrogenation and dechlorination did not affect other properties of naphtha. The nitrogen and chlorine in desorption oil was analyzed by peak height method, and the composition of nitrogen and chlorine was identified. The corresponding adsorption isotherms were fitted by Freundlich equation, and the correlation coefficient were more than 0.99.