Metal Modified NaY Zeolite as Sorbent for the Ultra-Deep Removal of Thiophene in Simulated Coke Oven Gas

The ultra-deep removal of thiophene is essential for the conversion of coke oven gas to methane and metal modified Y zeolite has excellent thiophene adsorption capacity. The effects of temperature on chemisorption between metal modified Y zeolite and thiophene and the reductive gases in coke oven gas on the thiophene adsorption performance still remains ambiguous. To address the aforementioned aims, series of NaMY (M = Ce, Ni, Zn and Ag) were prepared via ion-exchanged with Na+ of NaY, and two comparable sets of thiophene adsorption evaluation were conducted in a fixed bed reactor: (1) NaY and NaMY were evaluated at different temperatures in simulated coke oven gas, and (2) NaCeY was evaluated in N-2 and different reductive atmospheres. The results show that NaNiY, NaZnY and NaAgY could adsorb thiophene via pi-complexation, however, NaCeY mainly through S-Ce bond. pi complexation becomes weak above 150 degrees C, and the strength of S-Ce bond varies little when the temperature rises to 250 degrees C. Compared with that of other sorbents, the breakthrough adsorption capacity for thiophene (Q(b-thiophene)) of NaAgY reaches the highest 144 mg/g at 100 degrees C, but decreases sharply when temperature rises to 200 degrees C. NaCeY has relatively low variation in Q(b-thiophene) from 100 degrees C to 200 degrees C. Moreover, Ce(IV) in NaCeY is more favorable for thiophene adsorption than Ce(III) in coke oven gas and the presence of H-2 and CO would reduce the desulfurization activity of NaCeY. For the industrial utilization of thiophene ultra-deep removal, NaAgY has an excellent potential below 150 degrees C, while NaCeY with more Ce(IV) has a good prospect at 150-250 degrees C.