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.

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Fuel technology Fuel technology V 0400Desulfurization of Transportation Fuels with Zeolites under Ambient Conditions.-Cu + and Ag + zeolite Y, prepared by ion exchange of NaY zeolite with Ag + or Cu 2+ , adsorb sulfur compounds from commercial fuels (gasoline, diesel, and jet fuels) selectively and with high sulfur capacities at ambient temperature and pressure. The sulfur content in a commercial diesel is reduced from 430 to <0.2 ppm (by weight) at a sorbent capacity of 34 cm 3 of clean diesel produced per gram of sorbent. This sulfur selectivity and capacity are orders of magnitude higher than those obtained by previously known

Desulfurization of a commercial diesel fuel by different adsorbents was studied in a fixed-bed adsorber operated at ambient temperature and pressure. In general, the adsorbents tested for total sulfur adsorption capacity at breakthrough followed the order: AC/Cu(I)-Y Ͼ Cu(I)-Y Ͼ Selexsorb CDX (alumina) Ͼ CuCl/␥-Al 2 O 3 Ͼ activated carbon Ͼ Cu(I)-ZSM-5. The best adsorbent, AC/Cu(I)-Y (layered bed of 15 wt % activated carbon followed by Cu(I)Y), is capable of producing 30 cm 3 of diesel fuel per gram of adsorbent with a weighted average content of 0.15 ppmw-S, and about 20 cm 3 of diesel fuel per gram of adsorbent with a weighted average content of 0.06 ppmw-S. These low-sulfur fuels are suitable for fuel cell applications. The added layer of carbon not only delayed the sulfur breakthrough significantly but also sharpened the sulfur wavefronts. GC-FPD results showed that the -complexation sorbents selectively adsorbed highly substituted thiophenes, benzothiophenes, and dibenzothiophenes from diesel, which is not possible with conventional hydrodesulfurization (HDS) reactors. The high sulfur selectivity and high sulfur capacity of Cu(I)Y were because of -complexation. © 2004 AmericanInstitute of Chemical Engineers AIChE J, 50: [791][792][793][794][795][796][797][798][799][800][801] 2004 Keywords: desulfurization of liquid fuels, -complexation sorbent, desulfurization by adsorption, desulfurization of diesel, 4-methyl-dibenzothiophene adsorption, 4, 6-dimethyl- dibenzothiophene adsorption IntroductionThe federal government mandates a reduction in gasoline and diesel sulfur levels to 30 and 15 ppm, respectively, from the current levels of 300 -500 ppmw, to be implemented by 2006(Krause, 2000. This makes refiners consider eliminating production of onboard transportation fuels because of the high costs that will arise from compliance with such regulations (Parkinson, 2001). For fuel cell applications with gasoline as the feed, the sulfur content should be below 1 ppmw. For automotive fuel cells, liquid hydrocarbons are ideal fuels because of their higher energy density, availability, and safety for transportation and storage. However, the water-gas shift catalysts as well as fuel-cell electrode catalysts are poisoned by sulfur, and the sulfur content in the liquid fuel needs to be preferably less than 0.1 ppmw.Hydrodesulfurization (HDS) is very effective in removing thiols and sulfides, but it is not effective for the removal of thiophenic compounds. For example, the H 2 S produced during reaction of some thiophene derivatives is one of the main inhibitors for deep HDS of unreactive species (Ma et al., 1994;Knudsen et al., 1999). Among the unreacted refractory species are 4-methyl-dibenzothiophene (4-MDBT) and 4,6-dimethyldibenzothiophene (4, 6-DMDBT). These molecules are common in diesel fuels. The methyl groups in these species create a steric effect that hinders the capacity of HDS catalysts to chemisorb the sulfur atoms as depicted in Figure 1a. Such steric hindrance is not present for adsorption by -complexatio...