Hydrogenation and Hydrodesulfurization

The slurry in their case was treated as a homogeneous phase and the solid distribution was not taken into account. The model parameters were estimated from the correlations proposed for the case of no solid suspension (two-phase system). The coal dissolution, hydrogenation and hydrodesulfurization were considered as the key reactions, in the model. Also, the effect of mass transfer on the liquefaction process has been investigated. The model predictions were found to be in good agreement with the experimental... 

The use of such prepared catalysts has already been investigated for various reactions, including hydrogenation and hydrodesulfurization (HDS), polymerization of ethylene, synthesis and application of synthesis gas (syngas), and some other reactions, as briefly reviewed next. 

Sapre, A. V. (1980), "Hydrogenation and Hydrodesulfurization of Model Compounds in Coal Liquification", PhD Thesis, University of Delaware, Department of Chemical Engineering. 

Reduction and Hydrodesulfurization. Reduction of thiophene to 2,3- and 2,5-dihydrothiophene and ultimately tetrahydrothiophene can be achieved by treatment with sodium metal—alcohol or ammonia. Hydrogen with Pd, Co, Mo, and Rh catalysts also reduces thiophene to tetrahydrothiophene [110-01-0] a malodorous material used as a gas odorant. 

A hst of 74 GLS reacdions with hterature references has been compiled by Shah Gas-Liquid-Solid Reactions, McGraw-HiU, 1979), classified into groups where the solid is a reactant, or a catalyst, or inert. A hst of 75 reactions made by Ramachandran and Chaudhari (Three-Phase Chemical Reactors, Gordon and Breach, 1983) identifies reactor types, catalysts, temperature, and pressure. They classify the processes according to hydrogenation of fatty oils, hydrodesulfurization, Fischer-Tropsch reactions, and miscellaneous hydrogenations and oxidations. 

Figure 7.16. Dependence of the rate of thiophene hydrodesulfurization on the partial pressures of the reactants thiophene and hydrogen and of the product hydrogen sulfide,...

Flow diagram of the process for hydrogen and distillate fuel production from residual oil using iron oxides and steam. 1 = Cracking reactor, 2 = distillation column, 3 = hydrogen generator, and 4 = hydrodesulfurization reactor. 

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 ... 

Trickle-bed reactors usually consist of a fixed bed of catalyst particles, contacted by a gas liquid two-phase flow, with co-current downflow as the most common mode of operation. Such reactors are particularly important in the petroleum industry, where they are used primarily for hydrocracking, hydrodesulfurization, and hydrodenitrogenation other commercial applications are found in the petrochemical industry, involving mainly hydrogenation and oxidation of organic compounds. Two important quantities used to characterize a trickle-bed reactor are... 

Light oils are invariably hydroprocessed in gas-liquid-solid catalyst trickle-bed reactors (TBR). In these reactors, both the hydrogen and hydrocarbon streams flow down through one or more catalyst beds. A typical schematic diagram is shown in Figure 5.2—41 as an example of hydrodesulfurization process [60, 61]. 

The basic reactions of the MRG process consist of three stages (1) hydrodesulfurization of sulfur compounds in the hydrocarbon feedstock (2) low-temperature steam reforming (gasification) of desulfurized hydrocarbons and (3) methanation reaction between hydrogen and carbon dioxide in methane gas available by gassification. 

The foregoing reactions are highly exothermic and significantly raise reaction temperatures. The MRG process, however, docs not involve such adverse side reactions with use of a special, selective hydiodesulfuriziiig catalyst (developed by Japan Gasoline Co. and Nikki Chemical). The MRG process uses part of product gas for hydrodesulfunzation, and even if it contains only 20-25% hydrogen and as high as 20-23% carbon oxides, only the proper hydro desulfurization reactions take place, The MRG process features a recycle use of product gas for hydrodesulfurization purposes without any special treatment. 

The olefin (369) is thought to arise by reaction of the intermediate diradical (368) with hydrogen before subsequent hydrogenation of 369 to 370.767-769 When benzo[6]thiopheno[3,2-6]benzo[6]thiophene (154) is hydrodesulfurized, bibenzyl, (rans-stilbene, and 2-phenyl-benzo[6]thiophene are obtained in amounts determined by the catalyst and reaction conditions.768 This result lends support to the view that removal of sulfur precedes hydrogenation in hydrodesulfurization reactions. 

The rates of hydrodesulfurization of benzo[6]thiophene 770,771 and its 3-methyl derivative 772 have been compared with those of other sulfur compounds using hydrogen and a C0O3-M0O3-AI2O3 catalyst. 

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