# Direct Selective Oxidation of Hydrogen Sulfide: Laboratory, Pilot and Industrial Tests
## 19 Description of Modern Industrial Methods Based on the Process of Direct H\({}_{2}\)S Oxidation
in Germany in 1983 and 1987 and two SUPERCLAUS(r) installations in 1988 in Germany and 1989 in Holland [132; 133; 134]. The advantage of the processes described above is the possibility to supply air for the oxidation of hydrogen sulfide in a small excess compared to stoichiometry, which simplifies the control of the process in the conditions of variation of the composition and flow rate of the reaction mixture. However, the use of direct heterogeneous catalytic oxidation of hydrogen sulfide is significantly limited because of intense heating of a fixed catalyst bed due to high heat generation. At the Boreskov Institute of Catalysis SB RAS, the technology of direct oxidation of hydrogen sulfide in a reactor with a fluidized catalyst bed was developed, which is largely free of these shortcomings. A research program was implemented under which the effects of temperature and concentration of components on the kinetic parameters of the direct hydrogen sulfide oxidation process were studied. The oxidation of hydrogen sulfide in the composition of hydrocarbon-containing mixtures, the kinetic parameters of the hydrogen sulfide process for various catalytic systems, and the elementary stages of the process were investigated, and the activities of a wide range of supported oxide catalysts in the target reaction were measured. The main results of the research are the following:  
A wide range of supported catalysts meeting the requirements for catalytic systems operating in the reactor with a fluidized bed by their structural and mechanical characteristics (i.e., high mechanical strength and thermal stability) were synthesized and characterized [113; 135; 136]. Honeycomb catalysts have also been developed for the H\({}_{2}\)S oxidation process [137; 138; 139]. When studying the regularities of the reaction on the magnesium-chromium oxide catalyst, it was found that the following equation could describe by reaction kinetics [Equation (24)][140]:  
\[W=\kappa\cdot\left(C_{\mathrm{H_{2}S}}\right)^{m}\cdot\left(C_{\mathrm{O_{2}} }\right)^{n} \tag{24}\]  
The orders of \(m\) and \(n\) have similar values close to 0.5. This value of the observed order of the hydrogen sulfide oxidation reaction indirectly indicates that the first elementary stage of the process is the dissociative adsorption of hydrogen sulfide on the catalyst's surface. The activation energy is significantly lower than the value found for alumina, and it is about 8.1 kcal/mol [140]. The effect of hydrocarbons in the composition of the gas mixture on the parameters of the reaction of the direct oxidation of hydrogen sulfide was studied, which is a fundamental issue in developing the scientific foundations for the purification of hydrogen sulfide containing fossil fuels. As can be seen from the results presented in Figure 9, the temperature areas of the effective action of catalysts for the selected reactions are sufficiently separated, that is, in the temperature range of 220-260 \({}^{\circ}\)C, where the sulfur yield achieved is close to 100% propane oxidation reaction proceeds at a low rate [141]. Since kinetic data is quite formal and does not give unequivocal information about the mechanisms involved in the process, attempts have been made to study the elementary reaction stages using spectral methods [142; 143; 144]. To this end, three systems were selected:  
* Baseline magnesium-chromium oxide catalyst MgCr\({}_{2}\)O\({}_{4}\)/\(\gamma\)-Al\({}_{2}\)O\({}_{3}\)
* Iron oxide catalyst Fe\({}_{2}\)O\({}_{3}\)/\(\gamma\)-Al\({}_{2}\)O\({}_{3}\)
* \(\gamma\)-alumina \(\gamma\)-Al\({}_{2}\)O\({}_{3}\). FTIR spectroscopy of the adsorbed CO revealed that all the catalysts had both Lewis and Broensted acid sites on the surface (Figure 10). However, the nature, strength, and number of sites varied according to the type of catalyst. H\({}_{2}\)S adsorption and the formation of intermediates occurred on Lewis acid sites, as confirmed by the disappearance of LAS bands after H\({}_{2}\)S adsorption.