Hydrotreating reactions desulfurization

The main hydrotreating reaction is that of desulfurization, but many others take place simultaneously to various degrees, such as denitrogenation, various hydrogenations and hydrocracking (in some cases deoxidation and dehalogenation) (see Table 1). 

Naphtha desulfurization is conducted in the vapor phase as described for natural gas. Raw naphtha is preheated and vaporized in a separate furnace. If the sulfur content of the naphtha is very high, after Co—Mo hydrotreating, the naphtha is condensed, H2S is stripped out, and the residual H2S is adsorbed on ZnO. The primary reformer operates at conditions similar to those used with natural gas feed. The nickel catalyst, however, requires a promoter such as potassium in order to avoid carbon deposition at the practical levels of steam-to-carbon ratios of 3.5—5.0. Deposition of carbon from hydrocarbons cracking on the particles of the catalyst reduces the activity of the catalyst for the reforming and results in local uneven heating of the reformer tubes because the firing heat is not removed by the reforming reaction. 

The primary reactions occurring during hydrotreating are (43) desulfurization of sulfides, polysulftdes, mercaptans, and thiophene as exemplified by... 

Effect of HjS, Carbon Oxides, Etc. Hydrogen sulfide in the treat gas has an inhibiting effect on the kinetics of hydrotreating. Being a product of the desulfurization reactions, HjS must diffuse from the catalyst surface into the bulk gas stream. Any HjS present beyond that formed, further slows down the rate of diffusion with a consequent decrease in the amount of desulfurization for a given amount of catalyst. Therefore, additional catalyst would be required. 

The proposed NSPS can be met by hydrotreating the coal liquids obtained by filtering the product from the coal dissolution stage. The desulfurization kinetics can be presented by two parallel first-order rate expression, and hydrogen consumption kinetics can be presented by a first-order rate expression. A linear relationship exists between total sulfur content and SRC sulfur content of the hydrotreated product. For the Western Kentucky bituminous 9/14 coal studied here, the maximum selectivity and lowest SRC conversion to oil for a fixed SRC sulfur content are obtained using the highest reaction temperature (435°C) and the shortest reaction time 7 min.). ... 

Hydrotreating A catalytic reaction of distillate fractions with hydrogen at elevated pressures that is primarily used to desulfurize the feed. The products/are hydrogen sulfide and hydrocarbon organic nitrogen compounds react to form ammonia and hydrocarbon, while some hydrogen cyanide may be made from heavier fractions. 

Properties of Feedstock and Desulfurization Reactivity. Various feedstocks were hydrotreated through the pilot reactor under the constant desulfurization conditions to determine the reaction temperature required for 0.27 wt% sulfur product. The relationship between the contents of various impurities in the feedstock and the relative reaction temperature are illustrated in Figure 3 to 6. The feedstocks to be tested are atmospheric residue (AR) of AM, AH, Upper... 

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