Hydrodesulfurization of 4,6-dimethyldibenzothiophene

This paper describes the catalytic activity of nickel phosphide supported on silica, alumina, and carbon-coated alumina in the hydrodesulfurization of 4,6-dimethyldibenzothiophene. The catalysts are made by the reduction of phosphate precursors. On the silica support the phosphate is reduced easily to form nickel phosphide with hi catalytic activity, but on the alumina support interactions between the phosphate and the alumina hinder the reduction. The addition of a carbon overlayer on alumina decreases the interactions and leads to the formation of an active phosphide phase. 

Farag, H., Sakanishi, K. Mochida, I., and Whitehurst, D.D. Kinetic analyses and inhibition by naphthalene and H2S in hydrodesulfurization of 4,6-dimethyldibenzothiophene (4,6-DMDBT) over CoMo-based carbon catalyst. Energy Fuels, 1999, 13, 449. 

Turaga, U., Wang, G., Ma, X.L., Song, C.S., and Schobert, H.H. Influence of nitrogen on deep hydrodesulfurization of 4,6-dimethyldibenzothiophene American Chemical Society, Division of... 

Isoda, T. Nagao, S. Ma, X. Korai, Y. Mochida, I. Hydrodesulfurization of refractory sulfur species. 1. Selective hydrodesulfurization of 4,6-dimethyldibenzothiophene in the major presence of naphthalene over C0M0/AI2O3 and RU/AI2O3 blend catalysts. Energy Fuels 1996, 10, 482-486. 

Manoli JM, Costa PD, Brun M, Vrinat M, Mauge F, Potvin C (2004) Hydrodesulfurization of 4, 6-dimethyldibenzothiophene over promoted (Ni, P) alumina-supported molybdenum carbide catalysts activity and characterization of active sites. J Catal 221 365-377... 

Isoda, T. Ma, X. and Mochida, . Reactivity of Refractory Sulfur Compounds in Diesel Fuel (Part 2) Inhibition of Hydrodesulfurization Reaction of 4,6-Dimethyldibenzothiophene by Aromatic Compound. J. Japan Petrol. Inst. 1994, 37, 506. Farag, H. Sakanishi, K. Mochida, L Whitehurst, D. D. Kinetic Analyses and Inhibition by Naphthalene and H2S in Hydrodesulfurization of 4,6-Dimethyldibenzothiophene (4,6-DMDBT) over CoMo-Based Carbon Catalyst. Energy Fuels 1999, 13,449. 

Kwak C., Lee J. J., Bae J. S. and Moon S. H., Poisoning effect of nitrogen compounds on the performance of C0M0S/AI2O3 catalyst in the hydrodesulfurization of dibenzothiophene 4-methyldibenzothio phene and 4-6-dimethyldibenzothiophene, Appl. Catal. B Environ. 35 (2001) pp. 59-68. 

Both routes are known to operate in parallel during the hydrodesulfurization of unsubstituted dibenzothiophene and the preponderance of any one of them depends strongly on the catalyst formulation and on the reaction conditions. Alkyl substitution, particularly in the vicinity of the sulfur atom, as in 4-mcthyldibenzothiophene and 4,6-dimethyldibenzothiophene, results in a marked decrease in HDS rates, and in general, this is associated primarily with a decrease in the rate of the direct sulfur extrusion routes, which is known to be disfavored whenever there is steric congestion around the sulfur atom. 

Thiophenic compounds are naturally present in crude oil. Although hydrodesulfurization targets them and converts toward hydrocarbon and hydrogen sulfide [7] still significant quantities are present after this treatment. The reactivities of the 1- to 3-ring compounds decreases in the order thiophenes > benzothiophenes > dibenzothiophenes. In gasoline benzothiophenes are present, in jet fuel - benzothiophenes and dibenzothiophenes whereas in diesel fuel dibenzothiophenes and 4, 6-dimethyldibenzothiophene (4,6-DMDBT) are found. The latter is considered as the most refractory suffur compound towards HDS. The most common refractory sulfur compounds in liquid fuels are presented in Fig. 4. 

The majorify of sulfur compounds (thioles and sulfides) have been successfully removed from liquid fuel using a hydrodesulfurization process where high temperature and high pressure are required [7-9, 159]. As mentioned in section 2.5 some sulfur species are very resistant to hydrodesulfurization and those include thiophenic compounds, especially dibenzothiophene and 4,6 dimethyldibenzothiophene [148]. Various methods based on extraction and adsorption have been proposed to remove these compounds [7, 8, 13,145, 147-149, 151-158]. In the extraction route, sulfiir species are first oxidized and then extracted using organic solvents as, for instance acetonitrille [13, 149]. On the other hand, an adsorption process is usually tailored to enhance either adsorption forces, selectivity, or to impose a chemical reaction. So fer the enhancement in the removal of thiophenic compounds was reported on materials where n-complexation can occur as on Cu-Y zeolites [151, 153], or on alumina with highly dispersed sodium [147]. In the latter case, mono- and disodium thiophene metallates are formed. Another desulfurization methods use formation and subsequent precipitation of S-alkylsulfonium salts [148]. 

Egorova M, Prins R (2004) Hydrodesulfurization of dibenzothiophene and 4,6-dimethyldibenzothiophene over sulfided NiMo/y-Al203, CoMo/y-Al203, and M0/Y-AI2O3 catalysts. J Catal 225 417 27... 

Kabe T, Aoyama Y, Wang D, Ishihara A, Qian W, Hosoya M, Zhang Q (2001) Effects of H2S on hydrodesulfurization of dibenzothiophene and 4,6-dimethyldibenzothiophene on alumina-supported NiMo and NiW catalysts. Appl Catal Gen 209 237-247... 

Wang H, Prins R (2009) Hydrodesulfurization of dibenzothiophene, 4,6-dimethyldibenzothiophene, and their hydrogenated intermediates over Ni-MoS2/ Y-AI2O3. J Catal 264 31 3... 

Kabe, T., Ishihara, A. and Zhang, Q. Deep Desulfurization of Light Oil. 2. Hydrodesulfurization of Dibenzothiophene, 4-Methyldibenzothiophene and 4,6-Dimethyldibenzothiophene. Appl. Catal. A-Gen. 1993, 97, L1-L9. 

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