Desulfurization of liquid fuels

Yang, R.T. Takahashi, A. Yang, F.H. Hemandez-Maldonado, A. Selective Sorbents for Desulfurization of Liquid Fuels. U.S. and foreign Patent applications filed, 2002. 

Hernandez-Maldonado, A.J. and Yang, R.T. Desulfurization of liquid fuel by adsorption via pi complexation with Cu(I)-Y and Ag-Y zeolites. Industrial Engineering Chemistry Research, 2003. 42, 123. 

Recently great interest has been shown all over the world in the study of desulfurization of liquid fuels on various adsorbents [7, 8, 13, 145-158], It is driven by the fact that US federal regulations mandate the reduction in sulfur level for gasoline and diesel fuel to 30 and 15 ppm, respectively. The current levels are 300-500 ppmw. The new requirements will be implemented in 2006 [6]. Tire reason for lowering sulfur level, besides detrimental environmental effects is in the fact that sulfur compounds poison both automobile and fuel cell reformer catalysts. 

Another alternative for the desulfurization of liquid fuels involves biotechnological and biocatalytic processes. These processes are based on bacterial strains, the metabolism of which can convert carbon-rich sulfur compounds. Through a series of enzyme catalytic reactions, the strains remove the sulfur from the hydrocarbon compounds without altering the carbon skeleton [74] (see Figure 34.8). 

The desulfurization of liquid fuels using pervaporation has been increasingly investigated over the last few years [84]. As middle distillates contain mainly aromatic sulfur compounds, desulfurization membranes tend to make use of developments in aromatic-aliphatic separation. The most frequently used membrane materials investigated for the desulfurization of liquid hydrocarbon mixtures are polyurea-polyurethane, polysiloxane. Nation, cellulose triacetate, and poly-imide [84]. In addition to a range of processes for the desulfurization of naphtha fractions patented by ExxonMobil, Transionics, and Marathon Oil, only the S-Brane process developed by W. R. Grace and Sulzer has been tested beyond the laboratory scale [84]. 

Jayaraman A, Yang FH, Yang RT (2006) Effects of nitrogen compounds and polyaromatic hydrocarbons on desulfurization of liquid fuels by adsorption via jt-complexation with Cu(l)Y Zeolite. Energy Euels 20 909-914... 

Campos-Martin J., Capel-Sanchez M., Perez-Presas R, et al. (2010). Oxidative Processes of Desulfurization of Liquid Fuels, J. Chem. TechnoL Biot., 85, pp. 879-890. 

As one more common example of liquid fuels present reference may be drawn to liquified petroleum gas (LPG) or bottled gas or refinery gas. This fuel is obtained as a by-product during the cracking of heavy oils or from natural gas. It is dehydrated, desulfurized and traces of odours organic sulfides (mercaptans) are added in order to identify whether a gas leak has occurred. Supply of LPG is carried out under pressure in containers under different trade names. It consists of hydrocarbons of great volatility such that they can occur in the gaseous state under atmospheric pressure, but are readily liquifiable under high pressures. The principal constituents of LPG are n-butane, iso-butane, butylene and propane,... 

Bosmann, A., Datsevich, L., Jess, A., Lauter, A., Schmitz, C., Wasserscheid, P, Deep desulfurization of diesel fuel by extraction with ionic liquids, Chem. Commun., 2494-2495, 2001. 

With all of the scenarios in place, there is no doubt that petroleum and its relatives residua, heavy oil, and extra heavy oil (bitumen) will be required to produce a considerable proportion of liquid fuels into the foreseeable future. Desulfurization processes will be necessary to remove sulfur in an environmentally acceptable manner to produce environmentally acceptable products. Refining strategies will focus on upgrading the heavy oils and residua and will emphasize the differences between the properties of the heavy crude feedstocks. This will dictate the choice of methods or combinations thereof for conversion of these materials to products (Schuetze and Hofmann, 1984). 

A wide choice of commercial processes is available for the catalytic hydrodesulfurization of heavy oils and residua (Chapter 9). The suitability of any particular process depends not only upon the nature of the feedstock but also on the degree of desulfurization that is required. There is also a dependence on the relative amounts of the lower-boiling products that are to be produced as feedstocks for further refining and generation of liquid fuels. 

Dibenzothiophenes. Because of its commercial availability, dibenzothiophene is the most extensively used compound in studies of organosulfur metabolism. It has been used as a model compound in the studies of petroleum and coal biodesulfurization. These topics have been reviewed by Foght, J.M. Fedorak, P.M. Gray, M.R. Westlake, D.W.S. (Microbial desulfurization of liquid fossil fuels. In Microbial Mineral Recovery, in press) and Monticello and Finnertv (501. 

First results on n-complexation sorbents for desulfurization with Ag-Y and Cu(I)-Y zeolites have been reported recently [3,4]. In this work, we included the known commercial sorbents such as Na-Y, Na-ZSMS, H-USY, activated carbon and activated alumina (Alcoa Selexsorb) and made a direct comparison with Cu(l)-Y and Ag-Y which were the sorbents with n-complexation capability. Thiophene and benzene vapors were used as the model system for desulfurization. Although most of these studies can be applied directly to liquid phase problems, Cu-Y (auto-reduced) and Ag-Y zeolites were also used to separate liquid mixtures of thiophene/benzene, thiophene/n-octane, and thiophene/benzene/n-octane at room temperature and atmospheric pressure using fixed-bed adsorption/breakthrough techniques. These mixtures were chosen to understand the adsorption behavior of sulfur compounds present in hydrocarbon liquid mixtures and to study the performance of the adsorbents in the desulfurization of transportation fuels. Moreover, a technique for regeneration of the adsorbents was developed in this study [4]. 

Considering deep desulfurization of liquid hydrocarbon fuels for fuel cell applications, the removal of sulfur from a commercial diesel is more difficult than the... 

AC materials as porous materials with very high surface areas and large pore volume have been widely used in deodorization, decolorization, purification of drinking water, treatment of wastewater, and adsorption and separation of various organic and inorganic chemicals. Recently, some carbon materials have been reported for adsorptive desulfurization of liquid hydrocarbon fuels. 

Ania and Bandosz168 evaluated the performance of various ACs obtained from different carbon precursors as adsorbents for the desulfurization of liquid hydrocarbon fuels. According to their results, they concluded that the volume of micropores governs the amount physisorbed and mesopores control the kinetics of the process. They also found that introduction of surface functional groups enhances the performance of the ACs as a result of specific interactions between the acidic centers of the carbon and the basic structure of DBT molecule. 

Current progress in HDS via improvement of conventional catalysts, reactors, and processes or development of new catalysts, reactors, and processes has allowed the refining industry to be able to produce the low-sulfur fuels to meet the new EPA regulation. However, the current HDS technology is still difficult or costly to produce the ultraclean liquid hydrocarbon fuels for fuel cell applications. Adsorptive desulfurization and ODS are two promising alterable technologies for ultradeep desulfurization of hydrocarbons fuels for fuel cell applications. 

The selective ODS has shown many potential advantages for deep desulfurization of the fuels for fuel cell applications, because the process usually has higher desulfurization capacity than the adsorption desulfurizaton, and also can run at mild operating conditions without the use of H2. For ODS of liquid hydrocarbons fuels, direct use of oil-soluble peroxides or 02 as oxidants in an ODS process is greatly attractive, as the process does not involve a complicated biphasic oil-aqueous solution system. The key in ODS is how to increase the oxidation selectivity for the sulfur compounds. 

Song, C.S. and Ma, X.L., Ultra-deep desulfurization of liquid hydrocarbon fuels Chemistry and process. International Journal of Green Energy, 2004, 1, 167. 

Two different approaches are being considered for on-board sulfur removal. The first approach involves liquid-phase desulfurization of the fuel prior to reforming using a nickel-based adsorbent to remove organosulfur compounds (Bonville et al. 

So fer adsorption of dibezothiophenic compounds on activated carbon has not been explored extensively. This is likely owing to the feet that for efficient adsorbents, besides high adsorption capacity, a selectivity is required. On carbons, owing to their hydrophobic surface, the other aromatic components of liquid fuels are expected to be adsorbed in significant amounts. Nevertheless, some applications of activated carbons for deep desulfurization have been described in the literature [7, 8, 154-162]. 

Ma, X. Sprague, M. Sun, L. Song, C. Deep Desulfurization of Liquid Hydrocarbons by Selective Adsorptim for Fuel Cell implications. Am. Chem. Soc. Div. Pet. Chem. Prepr. 2002,47,48. 

Ma, X., Sprague, M., Sun, L., Song, C. (2002). Deep desulfurization of liquid hydrocarbons by selective adsorption for fuel cell apphcations. American Chemical Society, Divison of Petroleum Chemistry Preprints, 47, 48. 

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