Deep desulfurization of transportation fuels (gasoline, diesel, and jet fuels) is being mandated by U.S. and foreign governments and is also needed for future fuel cell applications. However, it is extremely difficult and costly to achieve with current technology, which requires catalytic reactors operated at high pressure and temperature. We show that Cu+ and Ag+ zeolite Y can adsorb sulfur compounds from commercial fuels selectively and with high sulfur capacities (by pi complexation) at ambient temperature and pressure. Thus, the sulfur content was reduced from 430 to <0.2 parts per million by weight in a commercial diesel at a sorbent capacity of 34 cubic centimeters of clean diesel produced per gram of sorbent. This sulfur selectivity and capacity are orders of magnitude higher than those obtained by previously known sorbents.

Desulfurization of a commercial diesel fuel by vapor-phase ion exchange (VPIE) copper(I) faujasite zeolites was studied in a fixed-bed adsorber operated at ambient temperature and pressure. The zeolite adsorbed approximately five thiophenic molecules per unit cell. After treating 18 cm3 of fuel, the cumulative average sulfur concentration detected was 0.032 ppmw-S. GC-FPD results showed that the pi-complexation sorbents selectively adsorbed highly substituted thiophenes, benzothiophenes, and dibenzothiophenes from diesel, which is not possible by using conventional hydrodesulfurization (HDS) reactors. The high sulfur selectivity and high sulfur capacity of the VPIE Cu(II)-zeolites were due to pi-complexation.

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Desulfurization of commercial gasoline and diesel by a π-complexation adsorbent, Cu(I)−Y zeolite, was studied in a fixed-bed adsorber operated at ambient temperature and pressure. The sulfur contents in the effluents were below (or well below) the detection limit using flame photometric detection (FPD), i.e., below 0.28 ppmw sulfur. Thus, these “sulfur-free” fuels are well suited for fuel cell applications. Furthermore, it is demonstrated that using a thin layer of a guard bed (e.g., activated carbon, AC) could significantly increase the sulfur capacities of the π-complexation sorbent. For a feed gasoline containing 335 ppmw sulfur, Cu(I)−Y produced 14.7 cm3 of sulfur-free gasoline/g of sorbent. When using AC as a guard bed, 19.6 cm3 of sulfur-free gasoline/g of combined sorbent was produced. For the case of diesel fuel, 34.3 cm3 of “sulfur-free” diesel was produced per 1 g of combined sorbent. The π-complexation sorbents have proven to be by far the most sulfur-selective as well as having the highest sulfur capacities. Gas chromatography−FPD results showed that the π-complexation sorbents selectively adsorbed highly substituted thiophenes, benzothiophenes, and dibenzothiophenes from gasoline and diesel, which is not possible by using conventional hydrodesulfurization reactors.