Gasoline desulfurization

CDHDS is used in combination with CDHyrdro to selectively desulfurize gasoline with minimum octane loss. Bottoms of CDHydro column, containing the reacted mercaptans, are fed to the CDHDS column where the MCN and HCN are catalytically desulfurized in two separate zones. HDS conditions are optimized for each fraction to achieve the desired sulfur reduction with minimal olefin saturation. Olefins are concentrated at the top of the column, where conditions are mild, while sulfur is concentrated at the bottom, where the conditions results in very high levels of HDS.76... 

Yokohama/ Dalkok Hydrogen Stn. (Desulfurized gasoline reforming type)... 

Rich solvent, containing aromatics and sulfur compounds, is routed to the solvent recovery column (SRC) where the hydrocarbons and sulfur species are separated, and lean solvent is recovered in column bottoms. The SRC overhead is hydrotreated by conventional means and either used as desulfurized gasoline or directed to an aromatics plant. Lean solvent from the SRC bottoms is recycled back to the EDC. 

Irvine, R.L. (1998) Process for desulfurizing gasoline and hydrocarbon feedstocks. US patent 5,730,860. 

The methods of producing hydrogen in on-site type stations include steam reforming of hydrocarbon-based materials such as city gas (CNG), naphtha, desulfurized gasoline, and methanol as well as alkaline water electrolysis. 

Xue, M., Chitrakar, R., Sakane, K., Hirotsu, T., Ooi, K., Yoshimura, Y, Toba, M. and Feng, Q. (2006) Preparation of cerium-loaded Y-zeolites for removal of organic compounds from hydro-desulfurized gasoline and diesel oil. J. Colloid Interface Sci., 298, 535-542. 

At most North American refineries, including Suncor-Samia, most of the sulfur in the gasoline pool comes from a catalytic cracking imit. To make low-sulfur gasoline, an Axens Prime-G unit was installed to desulfurize gasoline from the HCC and visbreaker units. Another option would have been to pretreat all of the HCC feed. (Already, hydrocracker bottoms comprise some of the HCC feed, but only a minor fraction. )... 

For example, in the case of light Arabian crude (Table 8.16), the sulfur content of the heavy gasoline, a potential feedstock for a catalytic reforming unit, is of 0.036 weight per cent while the maximum permissible sulfur content for maintaining catalyst service life is 1 ppm. It is therefore necessary to plan for a desulfurization pretreatment unit. Likewise, the sulfur content of the gas oil cut is 1.39% while the finished diesel motor fuel specification has been set for a maximum limit of 0.2% and 0.05% in 1996 (French specifications). 

The elimination of lead, the reduction of aromatics in gasoline, and the desulfurization of diesel fuels are oing to require significant reformulations of these products that will irripiy development of specific additives that allow the refiner to optimize costs while meeting the required specifications. 

Since the original cmde oils contain some sulfur compounds, the resulting products and gasolines also contain sulfur compounds, including hydrogen sulfide, mercaptans, sulfides, disulfides, and thiophenes. The processes used to sweeten, ie, desulfurize, the products depend on the type and amount of the sulfur compounds present and the specifications of the finished gasoline or other stocks. 

The general proportions may be varied from one end of the tower to the other to accommodate changing liquid volumes and physical properties. These towers have been used in diameters ranging from a few inches for laboratory work up to 2.4 m (8 ft) in diameter by 12.2 m (40 ft) tall for purposes of deasphalting petroleum. Other commercial services include furfural extraction of lubricating oils, desulfurization of gasoline, phenol recoveiy from wastewaters, and many others. Columns up to 4.5 m in diameter and up to 50 m in height have been constructed. 

In 1997 a total 1.3 billion gals of ethanol fuel was produced in the United States. Proposed new low sulfur conventional gasoline standards could greatly increase the demand for ethanol since desulfurization may lower gasoline octane. Almost all fuel ethanol is used as gasohol, but some is used to make E-85 (85% ethanol and 15% gasoline). E-85 can be used in flexible-fuel vehicles (FFVs) which can operate on gasoline or ethanol blends of to 85 percent ethanol. 

Desulfurization of FCC feedstocks reduces the sulfur content of FCC products and SOX emissions. In the United States, road diesel sulfur can be 500 ppm (0.05 wt%). In some European countries, for example in Sweden, the sulfur of road diesel is 50 ppm or less. In California, the gasoline sulfur is required to be less than 40 ppm. The EPA s complex model uses sulfur as a controlling parameter to reduce toxic emissions. With hydroprocessed FCC feeds, about 5% of feed sulfur is in the FCC gasoline. For non-hydroprocessed feeds, the FCC gasoline sulfur is typically 10% of the feed sulfur. 

FCC feed hydrotreating Gasoline end point reduction FCC gasoline hydrotreating Catalyst additives Bio-catalytic desulfurization... 

For nonhydrotreated feed, the gasoline sulfur level is about 10% of the feed sulfur level. For hydrotreated feed, it is about 5%. For example, if the sulfur content of a nonhydrotreated feed is 1.0 r (10,000 ppm), the sulfur in FCC gasoline will be 1,000 ppm. Assuming 80% desulfurization, feed to the FCC unit will contain 0.2% (2000 ppm) sulfur, resulting in FCC gasoline containing 100 ppm sulfur. Sulfur compounds that survive the hydrotreater are in the heav fraction and tend to end up in the LCO, decanted oil, and coke. 

Song, C., an Overview of New Approaches to Deep Desulfurization for Ultra-Clean Gasoline, Diesel Fuel and Jet Fuel. Catal. Today, 2003. 86 pp. 211-263. 

IFP, Gasoline desulfurization, ultra-deep., Hydrocarbon Process, 2000. 79 p. 114. 

Baco, F., Debuisschert, Q. Marchal, N., et al., Prime G+ process, desulfurization of FCC gasoline with minimized octane loss, in Fifth International Conference on Refinery Processing, AICHE 2002 Spring National Meeting. 2002. New Orleans, LA, March 11-14. 180-188. 

Shih, S. S. Owens, P. J. Palit, S., and Tryjankowski, D. A., Mobil s OCTGainprocess FCC gasoline desulfurization XE desulfurization reaches a new performance level, in NPRA 1999 Annual Meeting. 1999, March 21-23. AM-99-30. 

A strain N. asteroides KGB1, ATCC 202089 was discovered by EBC during its search for catalysts capable of desulfurizing thiophene and BT [126], The strain was patented and that patent covered the nucleic acid molecules encoding one or more enzymes catalyzing DS of thiophene/BT. The ability of the biocatalyst to desulfurize benzothiophene, makes it a suitable biocatalyst for gasoline treatment. The strain was also capable of converting... 

Improving stability of microbial strains in organic solvents is another challenge for enabling commercialization of desulfurization processes for gasoline and diesel applications. This was a target for a project in Klibanov s group [231], whose approach... 

An important parameter that has to be considered during desulfurization as well as for subsequent biocatalyst separation and recycle is the impact of the oil phase on the biocatalyst activity and half-life. Additionally, the effect of the biocatalyst on forma-tion/breakage of the oil-water emulsions is also important. The latter will be discussed in Section 2.3.3. It becomes important for lower boiling feedstocks such as gasoline, which offers the most toxic solvent environment for the biodesulfurization catalyst. The effect of solvents on biocatalysts has been investigated in very few reports. A study by the Monot group reported effect of two solvents on several Rhodococcus strains [254], The strains contacted with the solvents and their desulfurization activity, growth, and... 

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