Preparation Of Sorbents Modified By Metallic Ion And Their Performance Of Removing Thiophene In Coking Benzene

Benzene is an important chemical raw material and comes mainly from petroleum and coking industry. Along with the rapid development of chemical industry in recent years, styrene, phenol and other downstream products expand gradually, resulting in continued growth of the demand for pure benzene. Currently, the oil resources become more and more scarce, while the coal resources is relatively rich in China. The abundant coking benzene is generated with the rapid development of coking industry. But the existence of thiophenic sulfides in coking benzene, which can corrode metal equipment, poison catalysts during the following application, cause environmental pollution, and so on. This will seriously limit its utilization range. So the national standard of the sulfur content in coking benzene becomes more and more rigid.Adsorption removal of thiophenic sulfides has developed in recent years as a desulfurization method, which has the advantages of milder reaction conditions, smaller equipment corrosion, lower operating costs, recyclability of thiophene, less environmental pollution, and so on. From the point of energy saving and full utilization of resources, this method is very promising. However, and so on. So the research and development of highly efficient sorbents is the key to achieve industrial applications of this method.1) Sorbent ofγ-Al2O3 modified by supporting metallic ionγ-Al2O3 is a good sorbent carrier, with the features of high surface area, good thermal stability, simple structure, low expense, easy acquirement, and so on. It was selected as the sorbent carrier and was modified by incipient-wetness impregnation method in the different metallic nitrate solution. According the adsorption behavior in thiophene-benzene solution, it is found that the sorbent modified in silver nitrate solution has the best desulfurization ability.The amount of active component loaded onγ-Al2O3 can be accurately controlled by incipient-wetness impregnation method, but there is the problem of uneven dispersion of active component. The ultrasound can improve the rate of mass transfer between phases, change the equilibrium between adsorption phases. In view of this, the sorbent was prepared by the ultrasound-assisted impregnation method to improve impregnation performance. Experimental results show that the assistant ultrasound during sorbent preparation can not only shorten the preparing time, but also enrich the pore structure of sorbent and improve the size and distribution of the Ag particles, which is favorable to the removal of thiophene from benzene.The desulfurization capacity of sorbent changes with the content of Ag loaded inγ-Al2O3. The sorbent with 15% quality content of Ag prepared by ultrasound-assisted impregnation method has the highest desulfurization efficiency. It could reduce the thiophene concentration to 1.7 mg/L from 500 mg/L at room temperature and ambient pressure, with the desulfurization mg/L at room temperature and ambient pressure, with the desulfurization efficiency of more than 99%, when the ratio of sorbent to solution was 1:4 (g/mL).Comparing the desulfurization results in thiophene-cyclohexane, thiophene-benzene, tetrahydrothiophene-benzene, tetrahydrothiophene-cyclohexane solutions, it is found that there exist two kinds of connection between thiophene and sorbent modified in silver nitrate solution, theπ-complexation and the S-Ag bond.2) Sorbent of Y-type zeolite modified by metallic ion-exchangeY-type zeolite is a crystalline aluminosilicate with uniform pore structure and crystal cave, large surface area, good thermal stability, strong adsorption selectivity, which can be used to separate different types of molecules. So it was chosen as the sorbent carrier, and modified by liquid ion exchange method with different nitrate solutions. It is found that the desulfurization efficiency of the modified sorbents are all significantly improved, among which the sorbent modified in cerium nitrate solution has the best desulfurization ability. The optimum preparation conditions are that NaY zeolite is ion-exchanged in 0.1 mol/L Ce(NO3)3 solution at 100℃for 4 h, calcined at 700℃for 2 h, and repeated the above steps for two times. The sorbent prepared under the optimum conditions could remove entirely the thiophene in thiophene-benzene solution with 500 mg/L thiophene concentration, at room temperature and ambient pressure, when the ratio of sorbent to solution is 1:4 (g/mL). When the ratio of sorbent to solution was 1:14 (g/mL), its adsorptive capacity tends to saturation with the balance sulfur capacity of 5.74 mg/g.The fixed bed equipment was set up to study the adsorption ability of the optimal sorbent in the flow state. The results show that the smaller the sorbent the resistance of mass transfer and the energy consumption if the particle size was too small. The 0.2 mL/min flow rate of the solution presents the good desulfurization capacity. If it is too large or too small, the breakthrough time would be shortened. Room temperature is fine for the adsorption of thiophene because the interaction between sorbent and thiophene may be weakened and the adsorption ability is decreased at high temperature. Adsorption method is more suitable for the removal of thiophene with low concentration. When the thiophene concentration is 200 mg/L, the sulfur capacity of the sorbent is 4.18mg/g and the processing capability is 20.91 mL/g.