Sulphide composition

Influence of catalyst preparation, composition, and structure on activity and selectivity. There is an extensive literature some of which has been covered incidentally already. An excellent review has been published by Ripperger and Saum. Much of the work relates to the catalysts as oxides and so will not be covered in detail in this Report. Variables that influence catalytic properties include preparation e.g., method and order of addition of active components), pretreatment (drying and calcination,pre-reduction sulphiding,composition (e.g., concentration and ratio of active components and the type of support), distribution of active components in catalyst particles,particle size, " and surface area and pore size distribution. 

Figure 7,27 Schematic representation of 5 S values in a modern mid KJcean ridge hydrothermal vent system. Most values are taken from Kerridge cr al. (1983) but with additions, from Btuth and Ohmoto (1988) and Woodruff and Shanks (1988). The enlargement of the chimney wall shows changing 5 S values and sulphide composition from inner to outer wall.

Composition - which describes the proportion of hydrocarbon components (C, - Cj+) (which determine the fluid properties), and how many non-hydrocarbon substances (e.g. nitrogen, carbon dioxide and hydrogen sulphide) are present. 

In the blast furnace reduction slag-making materials are also added together with a small amount of iron, the function of which is to reduce any sulphide which remains, to the product of the roasting operation to produce a sinter. The sinter is then reduced with coke in a vertical shaft blast furnace in which air is blown tluough tuyeres at the bottom of tire shaft. The temperature in the heartlr where metal is produced must be controlled to avoid the vaporization of any zinc oxide in the sinter. The products of tlris process are normally quite complex, and can be separated into four phases. Typical compositions of these are shown in Table 13.1. 

The sulphur pressure of tire sulphides is a sensitive function of die tnetal/sulphur ratio around the stoichiometric composition, rising sharply when the sulphur content exceeds this limit. It follows from die Gibbs-Duhem equation... 

Vernon claims that in outdoor atmospheres the corrosion product consists largely of zinc oxide, hydroxide and combined water, but also contains zinc sulphide, zinc sulphate and carbonate. The following table gives the composition of typical films formed in an industrial atmosphere. 

Mrowec et examined the resistance to high-temperature corrosion of Fe alloys with Cr contents between 0.35 and 74 at% Cr in 101 kPa S vapour. They found that the corrosion was parabolic, irrespective of the temperature or alloy composition, and noted that sulphidation takes place at a rate five orders of magnitude greater than oxidation at equivalent temperatures. At less than 2% Cr, the alloys formed Fe, j.,S growing by outward diffusion of Fe ions, with traces of FeCr2S4 near the metal core. 

Fig. 7.71 An activity diagram showing the competing formation of sulphides and oxides on chromium. The XPS data (lower) show how sulphide replaced oxide as the surface anion when oxide samples were heated in the gas composition marked on the O-S diagram, implying that the boundary should be moved. (Reprinted with permission from Pergamon Press after...

Marine fouling leading to the local production of HjS increases crack growth rate, but what the effect is when combined with CP is uncertain. Some of the factors mentioned earlier in connection with other steel corrosion problems are important to sulphide stress-corrosion cracking, (SSCC), eg. compositions, particularly C which usefully can be reduced to below 0.05%, S, microstructure and segregation . Compositional homogenisation by heat treatment can be beneficial ", whilst the presence of Cu in the... 

Composition of the liquid environment The ionic composition, arising from dissolved salts and gases, has a considerable influence on the performance of inhibitors. In near-neutral aqueous systems the presence of certain ions tends to oppose the action of inhibitors. Chlorides and sulphates are the most common examples of these aggressive ions, but other ions, e.g. halides, sulphides, nitrates, etc. exert similar effects. The concentration of inhibitor required for protection will depend on the concentrations of these aggressive ions. Laboratory tests " have given some quantitative relationships... 

Hopper, Study Explosive Properties of Nitrogen Sulphide and Compositions Containing It , PATR 919 (1938) 14) Ibid, PATR 978... 

E. Davidson. Method and composition for scavenging sulphide in drilling fluids. Patent WO 0109039A, 2001. 

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. 

Metallic compositions serving as siccatives catalyze the well-known oxidation and polymerization of oil in paints and other finishes. Likewise, ferrous and other metallic objects boost self-heating in piles of lignocellulosics. Among the known catalyzing substances are iron sulphides and iron oxides from combustion gases of... 

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