Desulfurization approaches

Ultradeep desulfurization approaches include 1) improving catalytic activity by new catalyst formulation for HDS of 4,6-DMDBT 2) tailoring reaction and process conditions 3) designing new reactor configurations and 4) developing new processes. One or more approaches may be employed by a refinery to meet the challenges of producing ultraclean fuels at an affordable cost. 

K.N. Patel, N.C. Jadhav, P.B. Jagadhane, V.N. Telvekar, A novel strategy for the construction of azole heterocycles via an oxidative desulfurization approach using iodobenzene and oxone , Synlett 23 (2012) 1970-1972. 

The preparation of enamines by reduction of aromatic heterocyclic bases and their quaternary salts or of lactams is not the most useful approach (97). The lithium aluminum hydride reduction of N-acyl enamines has been used with both fruitful and unsuccessful results. A series of 3-N-acetyl -d -cholestenes (104) has been prepared by desulfurization of the appropriate thiazolidine (105) (98,99). Lithium aluminum hydride reduction of the... 

Tlie desulfurization of thiono compounds is another frequently used synthetic approach for the formation of double bonds via carbenoid intermediates. By this methodology, some indigoid 1,3,5,7-tetraazafulvalenes 88 and 90 were synthesized (83BSB781 90JPR949).Tliis dimerization starting from 2,4,5-tris(dimethylamino)imidazolium chloride via the appropriate thione 87 has been realized in the presence of phosphanes or phosphites to... 

There are three common methods for SO abatement. These are tine gas scrubbing, feedstock desulfurization, and SO additive. The SOj, additive is often the least costly alternative, which is the approach practiced by many refiners. 

Oxathiins derived from the cyclic diacylthione (60) and glycals by a cycloaddition reaction yield glycosides on desulfurization, offering an alternative approach to glycosyl transfer <96AG(E)777>. 

A similar approach via desulfurization of the thiosemicarbazide-substituted pyrimidone 290 using 4-nitrobenzyl bromide leads to efficient formation of the tricyclic system 291 in excellent yield (Equation 79) <2000RJ0430>. 

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. 

Song, C., and Ma, X., New design approaches to ultra-clean diesel fuels by deep desulfurization and deep dearomatization. 

Another report describing an approach to achieve alleviation of sulfur repression came from the Matsui research group. The dsz genes were cloned into a strain Rhodococcus sp. strain T09 under the promoter rrn of the strain T09 using a Rhodococcus-E. coli shuttle vector [214,215], This resulted in a strain which desulfurized DBT to 2-HBP in presence of sulfate, cysteine, or methionine. Similar approach was also used by Kurane to construct a gene expressing dszA-D enzymes, which eliminate the sulfate inhibition effects [216],... 

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... 

During the early 1990s IGT collaborated with EBC to develop the BDS process. The combined results from the two companies produced a series of patents describing the process for desulfurization of fossil fuels [237-240], Compared with the patent described in the earlier paragraph [235], these later patents propose a more realistic approach to desulfurization. The basis of these patents is the fact that some of the organosulfur compounds in petroleum are not desulfurized during hydrodesulfurization (HDS), but may be susceptible to BDS. 

The desulfurization process reported by the authors was a hybrid process, with a biooxidation step followed by a FCC step. The desulfurization apparently occurs in the second step. Thus, the process seems of no value, since it does not remove sulfur prior to the FCC step, but only oxidizes it to sulfoxides, sulfones, or sulfonic acids. The benefit of such an approach is not clearly outlined. The benefit of sulfur conversion can be realized only after its removal, and not via a partial oxidation. Most of the hydrotreatment is carried out prior to the FCC units, partially due to the detrimental effect that sulfur compounds exert on the cracking catalyst. It is widely accepted that the presence of sulfur, during the regeneration stage of the FCC units, causes catalyst deactivation associated with zeolite decay. In general terms, the subject matter of this document has apparent drawbacks. 

In addition to these studies, the Harmata group also successfully achieved the total synthesis (+)-curcumene 208 and curcuphenol 209 utilizing the 2,1-benzothiazine chemistry <03TL7261>. The synthesis of (+)-curcuphenol was accomplished by reduction of benzothiazine 94, followed by protection, desulfurization, reductive deamination and deprotection to give diol 223 in good yield. The latter was then converted into (+)-curcuphenol 209 (Scheme 63). The total synthesis of (+)-curcumene involved a similar approach to that of (+)-cucurphenol. 

As will be seen through the specific examples discussed later, the yields in Raney nickel desulfurization are quite variable, rarely approaching quantitative doubtless some of the reported yields would have been higher had the spent nickel, which tends to adsorb the products, been extracted more exhaustively. 

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