Hydrodesulfurization, petroleum

Thermal Cracking. In addition to the gases obtained by distillation of cmde petroleum, further highly volatile products result from the subsequent processing of naphtha and middle distillate to produce gasoline, as well as from hydrodesulfurization processes involving treatment of naphthas, distillates, and residual fuels (5,61), and from the coking or similar thermal treatment of vacuum gas oils and residual fuel oils (5). 

Fig. 14. ICI—LCA process flow sheet PAC, purified air compressor HDS, hydrodesulfurization IP, iatermediate pressure LP, Hquefied petroleum BFW,...

The breadth of reactions catalyzed by cobalt compounds is large. Some types of reactions are hydrotreating petroleum (qv), hydrogenation, dehydrogenation, hydrodenitrification, hydrodesulfurization, selective oxidations, ammonoxidations, complete oxidations, hydroformylations, polymerizations, selective decompositions, ammonia (qv) synthesis, and fluorocarbon synthesis (see Fluorine compounds, organic). 

Trickle Bed Hydrodesulfurization The first large-scale apph-cation of trickle bed reactors was to the hydrodesulfurization of petroleum oils in 1955. The temperature is elevated to enhance the specific-rate and the pressure is elevated to improve the solubihty of the... 

In most applieations, the reaetion oeeurs between a dissolved gas and a liquid-phase reaetant in the presenee of a solid eatalyst. In some eases, the liquid is an inert medium and the reaetion takes plaee between the dissolved gases at the solid surfaee. These reaetors have many diverse applieations in eatalytie proeesses and are used extensively in the ehemieal industry. Triekle-bed reaetors have been developed by the petroleum industry for hydrodesulfurization, hydroeraeking, and hydrotreating of various petroleum fraetions of relatively high boiling point. Under reaetion eonditions, the hydroearbon feed is frequently a vapor-liquid mixture that reaets at liquid hourly spaee veloeities (LHSV in volume of fresh feed, as liquid/volume of bed, hr) in the... 

Thiophenes continue to play a major role in commercial applications as well as basic research. In addition to its aromatic properties that make it a useful replacement for benzene in small molecule syntheses, thiophene is a key element in superconductors, photochemical switches and polymers. The presence of sulfur-containing components (especially thiophene and benzothiophene) in crude petroleum requires development of new catalysts to promote their removal (hydrodesulfurization, HDS) at refineries. Interspersed with these commercial applications, basic research on thiophene has continued to study its role in electrocyclic reactions, newer routes for its formation and substitution and new derivatives of therapeutic potential. New reports of selenophenes and tellurophenes continue to be modest in number. 

Research into cluster catalysis has been driven by both intrinsic interest and utilitarian potential. Catalysis involving "very mixed -metal clusters is of particular interest as many established heterogeneously catalyzed processes couple mid and late transition metals (e.g., hydrodesulfurization and petroleum reforming). Attempts to model catalytic transformations arc summarized in Section II.F.I., while the use of "very mixed -metal clusters as homogeneous and heterogeneous catalysis precursors are discussed in Sections I1.F.2. and I1.F.3., respectively. The general area of mixed-metal cluster catalysis has been summarized in excellent reviews by Braunstein and Rose while the tabulated results are intended to be comprehensive in scope, the discussion below focuses on the more recent results. 

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 DS7 strain is characterized for its activity on the representative sulfur groups of the molecules present in fuel producing cuts, both gasoline and diesel. Examples given include straight-run gas oils, gas oils from hydrodesulfurization and the main streams coming from the atmospheric distillation of petroleum (cuts 70-160°C, 160-230°C and 230-350°C.),... 

Autofining A fixed-bed catalytic process for removing sulfur compounds from petroleum distillates. This process uses a conventional cobalt/molybdenum hydrodesulfurization catalyst but does not require additional hydrogen. Developed by The Anglo-Iranian Oil Company in 1948. 

Cycloversion A petroleum treatment process which combined catalytic reforming with hydrodesulfurization. The catalyst was bauxite. The process differed from the Houdry process in that the catalyst bed temperature was controlled by injecting an inert gas. Developed by the Phillips Petroleum Company and used in the United States in the 1940s. Pet. Refin., 1960, 39(9), 205. 

DHDS [Diesel deep hydrodesulfurization] A petroleum refining process developed by the Instituto Mexicano del Petroleo (IMP) with plans for it to be in operation at the Pemex refinery at Cadereyka, Mexico, in 1999. 

Gulf HDS A process for hydrorefining and hydrocracking petroleum residues in order to make fuels and feeds for catalytic cracking. Developed by the Gulf Research Development Company. See also hydrodesulfurization. 

RDS Isomax [Residuum desulphurization] A hydrodesulfurization process for removing sulfur compounds from petroleum residues, while converting the residues to fuel oil. Developed by Chevron Research Company in the early 1970s. Ten units were operating in 1988. See also VGO Isomax, VRDS Isomax. 

RESID-fining [Residuum refining] A hydrodesulfurization process adapted for petroleum residues. Developed by Esso Research Engineering Company and licensed by them... 

Trickle Hydrodesulfurization A process for removing sulfur-, nitrogen-, and heavy-metal-compounds from petroleum distillates before catalytic cracking. The preheated feed is hydrogenated, without a catalyst, in an adiabatic reactor at 315 to 430°C. Developed by Shell Development Company. As of 1978, 91 units had been installed. 

Ultrafining Two hydrodesulfurization processes developed by Standard Oil of Indiana, one for petroleum residua and one for vacuum gas oil. 

VGO Isomax [Vacuum gas oil] A hydrodesulfurization process adapted for treating vacuum gas oil, a petroleum fraction. Developed by Chevron Research Company in the early 1970s. In 1972, five plants were in operation and six were under construction. See also RDS Isomax and VRDS Isomax. 

VRDS Isomax [Vacuum residua desulphurization] A hydrodesulfurization process adapted for processing the residues from the vacuum distillation of the least volatile fraction of petroleum. An extension of the RDS Isomax process, developed and piloted by Chevron Research Company in the early 1970s. In 1988, one unit was under construction and one was being engineered. 

Trickle-bed reactors are used in catalytic hydrotreating (reaction with H2) of petroleum fractions to remove sulfur (hydrodesulfurization), nitrogen (hydrodenitrogena-tion), and metals (hydrodemetallization), as well as in catalytic hydrocracking of petroleum fractions, and other catalytic hydrogenation and oxidation processes. An example of the first is the reaction in which a sulfur compound is represented by diben-zothiophene (Ring and Missen, 1989), and a molybdate catalyst, based, for example, on cobalt molybdate, is used ... 

This compound is notorious as a hard sulfide that cannot be removed from petroleum by current hydrodesulfurization processing. Oxidation by tert-butyl hydroperoxide occurs readily when 1 is used as the catalyst. After trying several combinations, this was the most effective 0.5 mmol of DMDBT, 1.75 mmol B OOH, and 0.05 mol% of 1 were placed in refluxing toluene (384 K). A quantitative yield of the dioxide was obtained in 2h. The oxidation product is insoluble in toluene and can readily be removed by filtration (42). 

One of the major challenges in the petroleum industry today is the removal of sulfur compounds, especially refractive ones such as 4,6-dimethyldibenzo-thiophene (DMDBT), from petroleum fractions such as diesel to concentrations <5-10 ppm from the current values of 50-500 ppm. The current technology is hydrodesulfurization catalyzed by cobalt-nickel-molybdenum sulfides at high pressures. Reducing sulfur concentratios in diesel fuels below 5-10 ppm... 

Liberated gasses are drawn off at the top of the tower with the naptha. The gas is recovered to manufacture refrigerated liquefied petroleum gas (LPG). The naptha is condensed at a temperature of about 52 °C (125 °F). Part of the condensed naptha is normally returned to the top of the tower. The naptha product stream is split into light naptha for gasoline blending and heavy naptha for further reforming. Inside the tower, kerosene is withdrawn at a temperature of about 149 °C (300 °F). Diesel is withdrawn at a temperature of 260 °C (500 °F). These middle distillates are usually brought up to specification with respect to sulfur content with hydrodesulfurization. The heavy oil... 

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