Metal-Organic Framework Materials for Desulfurization by Adsorption

Current European regulations limit the sulfur content of gasoline to 10 ppmw. Such deep desulfurization levels can be achieved by catalytic hydrodesulfurization processes, but they are accompanied by excessive H-2 consumption for unwanted side reactions, in particular, for the hydrogenation of olefins. Selective adsorption constitutes an attractive alternative to catalytic desulfurization. The main challenge is to find adsorbents able to remove the sulfur compounds with very high selectivity from a complex mixture of paraffins, naphthenes, olefins, and aromatic compounds. In the present contribution we present the screening of a large number of metal-organic frameworks (MOFs) for this purpose, using batch adsorption experiments. For the two most promising structures (HKUST-1 and CPO-27-Ni, two cus-MOFs, that is, with coordinatively unsaturated sites), the dynamic behavior, the impact of a model nitrogen-containing compound (pyridine) on the adsorption properties, as well as the regenerability were also evaluated by breakthrough experiments. The good results obtained in purification of our model feeds incited us to perform measurements with a real gasoline feed using batch measurements. The feasibility of adsorptive desulfurization of gasoline using MOFs is discussed on the basis of these results.