Effect Of Acid And Metal Modification On Desulfurization Performance Of Zeolite Y

As one of the important industrial chemicals, benzene is mainly derived from petroleum benzene and coking benzene. Coking benzene with relatively rich resources has received increasing emphasis in the situation of insufficient petroleum resource and increasing benzene demand. Because of high content of impurities in coking benzene, purification is necessary. Of all the impurities, thiophene represents a particular challenge as it is physically and chemically similar to benzene. But the existence of traces of thiophene is severely harmful to the subsequence utilization of benzene. Therefor, deep removal and effective collection of thiophene are quite significant. Because of the limitation of chemical reaction equilibrium, it is very difficult to deeply remove thiophene from benzene through washing with sulfuric acid and catalytic hydrogenation. Other methods are needed. Selective adsorption is one of the most promising ultra deep desulfurization methods because of being accomplished at ambient temperature and pressure. However, the success in this technich would depend on the development of sorbents with high selectivity to thiophene. The physic-chemical properties on the surface of zeolites are important factors that influence the desulfurization performance of sorbents. So surface and metal modification of sorbents that based on desulfurization mechanism are designed to deeply remove thiophene from benzene to the demand of ppb level.Firstly, a series of Y zeolites in the H form with different acid amounts, acid strength and acid type were prepared with different concentrations of ammonium nitrate solution. Combining the NH3-TPD and Py-FTIR characterizing results of HY sorbent with its desulfurization property, the relationship between the surface acidity of sorbent and its desulfurization performance was researched. Both total acid amount and mediate strong acid amount of the HY zeolite increased in the order of HY005A, HY01A, HY03A, HY05A, HY07A, FY10A.With the maximum content of mediate strong B acid sites, zeolite HY10A performs best in the desulfurization of thiophene from benzene. In the preparation process of zeolite HY10A, when the calcination temperature rised from300℃to750℃, the desulfurization efficiency of sorbents HY10AC300, HY10AC620,HY10AC750gradually reduced because of the transformation of B acid sites to L acid sites. Based on the above results, cooperative effects of acid modification and metal modification are investigated with the comparation of desulfurization performance of zeolite modified respectively with acid, metal, acid and metal step by step. TG/DTG and FTIR analysis results of sorbents adsorbed with thiophene indicates that zeolite modified with acid and Cu+step by step has the best desulfurization performance. When the ratio of sorbent to thiophene-benzene with concentration of500mg/L is1:14g/mL, desulfurization efficiency of CuHY reached61%.