Deep desulfurization of diesel by adsorption over Ni/ZSM-5

Introduction Environmental restriction regarding the quality of transportation fuels and the emissions from them are the most important issues. Because of more stringent regulations and fuel specifications regarding development of better method for deep-desulfurization of fuels are important. There has been recent interest in developing adsorbents for selective desulfurisation by adsorption. Mercaptans, thiophenes, sulfides that are present in diesel are linear compounds and hence easy to remove by adsorptive desulfurisation process but benzothiophenes, dibenzothiophene, 4MDBT, 4,6-DMDBT are cyclic compounds, are difficult to remove due to very high sterric hinderence. [1-5] Desulfurization by adsorption is based on the ability of a solid sorbent to selectively adsorb organosulfur compounds from refinery streams. The pi complexation bonds are stronger than those formed by Vander Waals interactions, but they are also weak enough as to be broken by traditional engineering means, such as increasing temperature and/or decreasing pressure. Therefore, this provides opportunities for tailoring and developing new adsorbents for processes where selective adsorption is needed, such as in the case of sulfur removal from fuels. [6-7] Although research has been carried out using various sorbents, there is not a single sorbent identified for the removal of sulfur compounds. It was reported in literature that Cu, Ni, Mo and Ag based sorbents have given satisfactory results for desulfurization. Howover details of sorbent preparation and characterization are not revealed. There is also a need to understand the mechanism of adsorption of various compounds of sulfur on the surface. Experimental The adsorbents prepared in this work were based on Nickel over ZSM-5 support. Incorporation of Ni into the zeolite framework was done using liquid-phase ion-exchange method at room temperature. Different amount of Nickel was loaded on to the support. Ni(I)-ZSM-5 adsorbent was prepared by ion-exchanging ZSM-5[(Si/Al)=20] with Ni(NO3)2 aq. solution for 24hours.This solution is heated in oven for 18 hours at 110 °C and then calcined at 550 °C for 4 hrs.