In hydrotreating

Effect of Catalyst The catalysts used in hydrotreating are molybdena on alumina, cobalt molybdate on alumina, nickel molybdate on alumina or nickel tungstate. Which catalyst is used depends on the particular application. Cobalt molybdate catalyst is generally used when sulfur removal is the primary interest. The nickel catalysts find application in the treating of cracked stocks for olefin or aromatic saturation. One preferred application for molybdena catalyst is sweetening, (removal of mercaptans). The molybdena on alumina catalyst is also preferred for reducing the carbon residue of heating oils. 

Sulfided Mo and Co-Mo catalysts, used in hydrotreating reactions, contain Mo as M0S2. This compound has a layer structure consisting of sandwiches, each of a Mo layer between two S layers. The chemical activity of M0S2 is associated with the edges of the sandwich where the Mo is exposed to the gas phase the basal plane of the anions is... 

Sulfides play an important role in hydrotreating catalysis. Whereas oxides are ionic structures, in which cations and anions preferably surround each other to minimize the repulsion between ions of the same charge, sulfides have largely covalent bonds as a consequence there is no repulsion which prevents sulfur atoms forming mutual bonds and hence the crystal structures of sulfides differ, in general, greatly from those of oxides. 

Marchal, N. Kasztelan, S., and Mignard, S., A comparative study of catalysts for the deep aromatic reduction in hydrotreated gas oil. In Catalytic Hydroprocessing of Petroleum and Distillates, M.C. oballa, S.S.S. editor. 1994, Marcel Dekker New York. pp. 315-327. 

Jokuty, P., and Gray, M. R., Resistant Nitrogen Compounds in Hydrotreated Gas Oil From Athabasca, bitumen,. Energy Fuels, 1991. 5 pp. 791-795. 

Before the molybdenum catalysts can be used in hydrotreating reactions, they have to be sulfided. Raman spectroscopy sensitively reveals this transition. The characteristic Mo-S frequencies of MoS2 are at 389 and 411 cm-1 [45,46], much lower... 

We begin with the structure of a noble metal catalyst. The emphasis is on the preparation of rhodium on aluminum oxide and the nature of the metal-support interaction. Next we focus on a promoted surface in a review of potassium on noble metals. This section illustrates how single crystal techniques have been applied to investigate to what extent promoters perturb the surface of a catalyst. The third study deals with the sulfidic cobalt-molybdenum catalysts used in hydrotreating reactions. Here we are concerned with the composition and structure of the catalytically active... 

Hydrotreating generates sour wastewater from fractionators used for product separation. Like most separation processes in a refinery, the process water used in fractionators often comes in direct contact with oil and thus can be highly contaminated. It also contains hydrogen sulfide and ammonia and must be treated along with other refinery sour waters. In hydrotreating, sour wastewater from fractionators is produced at the rate of about I.O gallon per barrel of feed. 

Table 12.19 Zeolites used in hydrotreating or hydrocracking processes. 

D.6. Metallic Brim States as Active Sites in Hydrotreating Catalysts... 

A major deficiency in the asphaltene diffusion studies results from the limitations of the experimental conditions employed. Measurements at room temperature and in clean solvents can potentially alter the effective size of the diffusing species relative to that in hydrotreating catalysts at reaction conditions. 

Product yields (Table 8-1) indicate that there is no coke. The distillates produced by this process are generally lower in the content of olefin hydrocarbons than the other thermal cracking process, comparatively easy to desulfurize in hydrotreating units, and compatible with straight run distillates. 

Dautzenberg FM. Novel reactor concepts in hydrotreating. Cattech 1999 3 54—63. 

Analysis of the Liquid Product Used in Hydrotreating Stage... 

Reaction Parameter Studies. Experiments were carried out with conventional shale oil [direct retorted Paraho shale oil) for the purpose of studying the effects of reaction parameters in hydrotreating under supercritical conditions. In one group of experiments, the space velocity was varied (1.6, 3.2, and 5)... 

Before the molybdenum catalysts can be used in hydrotreating reactions, they must be sulfided, and Raman spectroscopy sensitively reveals this transition. The characteristic Mo-S frequencies of M0S2 are at 389 and 411 cm-1 [51], much lower than the Mo-O bands. This occurs because, first, sulfur is twice as heavy as oxygen and, second, the Mo-S bond is weaker than the Mo-O bond [see Eq. (8-3)]. The Raman spectra of a sulfided M0O3/AI2O3 also show a band at 529 cm-1, due to the (S-S)2 disulfide species, which is probably located at the edges of the... 

Section III is a discussion of HDN by catalysts different from metal sulfides, such as metals, metal carbides, and metal nitrides. The latter two classes of compounds have drawn much attention in the preceding decade in several fields of catalysis. Their possible role in hydrotreating is analyzed critically. 

Fluorine is also used commercially as an additive in hydrotreating catalysts. Fluorine is added especially to hydrocracking catalysts because it increases the acidity of the catalyst and thus promotes acid-catalyzed cracking of hydrocarbons. Test reactions, such as the cracking of cumene to give benzene and propene, have demonstrated clearly that fluorine rather than... 

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