Hydrodesulphurization catalyst

Partially Crystalline Transition Metal Sulphide Catalysts. Chiannelli and coworkers (6, 7, 8) have shown how, by precipitation of metal thio-molybdates from solution and subsequent mild heat-treatment many selective and active hydrodesulphurization catalysts may be produced. We have shown (18) recently that molybdenum sulphide formed in this way is both structurally and compositionally heterogeneous. XRES, which yields directly the variation in Mo/S ratio shows up the compositional nonuniformity of typical preparations and HREM images coupled to SAED (see Figure 2) exhibit considerable spatial variation, there being amorphous regions at one extreme and highly crystalline (18, 19) MoS at the other. 

Mitchell, P. C. H., The Chemistry of Some Hydrodesulphurization Catalysts Containing Molybdenum. Climax Molybdenum Co., London, 1967. 

The best way to remove sulphur compounds is to convert the organic sulphur species to H2S over a hydrodesulphurization catalyst. The next step is sulphur removal with an absorbent. The same catalyst can usually convert any organo-chloride species to give HC1 and also act as an absorbent for most problematic metal species. A second absorbent is used for chloride removal70. 

Fig. 10.14. Infrared spectra of NO probe molecules on sulphided Mo, Co, and Co-Mo hydrodesulphurization catalysts allow for titration of Co and Mo sites in the Co-Mo catalyst...

Although relatively little used in catalysis, Mossbauer spectroscopy has given important information on the state of iron and cobalt in Fischer-Tropsch and hydrodesulphurization catalysts. Mossbauer spectroscopy provides the oxidation state, the magnetic field and the lattice symmetry of a number of elements such as iron, tin, iridium, and cobalt, and can be applied in situ. We will first describe the theory behind the Mossbauer effect and explain how a nuclear technique gives information on the state of atoms. 

Sulphur compounds in the fuel (0.05-0.01 %) must be removed because they would poison the reformer catalyst. Sulphur compounds are removed by using a hydrodesulphurization catalyst (HDS), typically noble metals on alumina, to convert the organic sulphur to hydrogen sulphide. Then a zinc oxide adsorbent bed is used to trap the hydrogen sulphide ... 

F.P, Daly, J S Brinen, and J L. Schmitt, A wide pore carbon supported hydrodesulphurization catalyst, Appi. Catal 11 (1984) 161-164 ... 

Hydrodesulphurization Catalysts Based on Mo or W. - In this Section structural studies of Mo- and W-containing catalysts (unsupported and supported, without and with promoters) and relations between catalyst composition and structure and catalytic properties are reported. Work on sulphides of other metals and on the kinetics and mechanism of hds is reported in the following two Sections. 

Other Metal Sulphides as Hydrodesulphurization Catalysts. - Titanium. TiS2, precipitated by adding Li2S to TiCU in tetrahydrofuran, was effective, after heating in H2/H2S, in hds of benzothiophen (673 K, 32 atm). ... 

A Mossbauer spectrometer consists of a radioactive Co source on a transducer that continuously scans the desired velocity range, an absorber consisting of the catalyst and a detector to measure the intensity of the gamma radiation transmitted by the absorber as a function of the source velocity. This is the common mode of operation, called Mossbauer absorption spectroscopy, sometimes abbreviated as MAS. It is also possible to fix the Co containing source and move a single-line Fe absorber, in order to investigate Co-containing catalysts. This technique, called Mossbauer emission spectroscopy (MES), has successfully been applied to study Co-Mo hydrodesulphurization catalysts [42]. 

We discuss now how the activity and selectivity depend on the composition of the catalyst with reference to om results and literature data [10]. (jenerally the effect of composition has been discussed in terms of excess of M0O3. However, since M0O3 is in excess it would seem logical to express the variation of catalyst composition in terms of iron added (or not) to molybdenum, i.e. the Fe/Mo ratio or the Fe/(Fe+Mo) mole fraction as for other two-component catalysts, for example, the cobalt-promoted molybdenum disulfide based hydrodesulphurization catalyst. 

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