# Direct Selective Oxidation of Hydrogen Sulfide: Laboratory, Pilot and Industrial Tests
## 18 Transition Metal Oxides
By the use of \(\alpha\)-alumina, it is possible to synthesize the catalyst in which the active component evenly covers the support surface and prevents the diffusion of reagents to the surface of alumina, which has been shown to actively catalyze the reverse Claus reaction-the interaction of sulfur and water vapor to form hydrogen sulfide and sulfur dioxide. This iron catalyst was specially designed for the created SUPERCLAUS@process. The same authors undertook interesting attempts [121] to create effective catalytic systems based on various composite systems and, in particular, alloys of type Hastelloy-X and Inconel with fillers-SUPERCLAUS@commercial catalysts (the amount of additive did not exceed 2 wt.%). The simultaneous use of such materials as catalysts and reactor construction materials was proposed, that is, the effective combination of construction and catalytic properties. It was shown that such systems in the future could make a serious competition to classic reactors with bulk catalysts. Particular emphasis was bestowed on the possibility of using such structures (combined reactor-catalyst) to carry out the hydrogen sulfide oxidation process at a high H\({}_{2}\)S content, given the high heat engineering characteristics of the developed materials. However, it was indicated that the upper limit of the content of hydrogen sulfide for the effective operation of these systems should not exceed 10 vol.%. New possibilities extending the range of the application of the technology of direct H\({}_{2}\)S oxidation are provided by monolithic honeycomb catalysts, which possess several  
Figure 7: The dependence of the selectivity of the process of direct H\({}_{2}\)S oxidation on the ratio O\({}_{2}\)/H\({}_{2}\)S in the initial mixture (adapted from [118]). technological advantages over granulated catalysts (most important of them low pressure drop), especially for the gases with low excessive pressure and for purposes when the pressure loss is unacceptable. For the first time, such studies were undertaken by the research team under the guidance of Professor [PERSON]. Successful pilot and experimental-industrial tests of the direct oxidation process in reactors with monolithic catalysts of the honeycomb structure to purify the tail gases of the Claus process and geothermal steam are reported [122; 123; 124]. Laboratory studies of the catalysts for direct oxidation of hydrogen sulfide in the form of monolithic catalysts of the honeycomb structure were also reported by Italian scientists [125]. Monoliths from corderite (9 channels) from 10 to 50 mm long, 6 mm wide, and 6 mm high with 226 channels per square inch (CPSI) were used as a substrate for coating. The commercial ceria-zirconia composition (EooCat) having the initial solids content of 40 wt.% was deposited on corderite. The active phase (V\({}_{2}\)O\({}_{5}\)) deposition was carried out from an aqueous solution of ammonium metavanadate (NH\({}_{4}\)VO\({}_{3}\)). The authors reported that at a temperature of 200 \({}^{\circ}\)C, contact time \(>\)200 ms and initial H\({}_{2}\)S content 500 ppmv, high conversion of H\({}_{2}\)S (90%) and a very low selectivity toward SO\({}_{2}\) (3%) were obtained. Similar data are given by [PERSON] and co-authors [126], where the results of studies on the use of selective catalytic oxidation to remove hydrogen sulfide from landfill gas using monolithic catalysts of the honeycomb structure are described. The efficiency of removing H\({}_{2}\)S at a temperature of 200 \({}^{\circ}\)C was the highest for the V/TiO\({}_{2}\) catalyst obtained by incipient wetness impregnation. The optimal content of vanadium is 10% by weight. In addition, it was shown that the selectivity to sulfur and minimization of the formation of SO\({}_{2}\) substantially depends on the O\({}_{2}\)/H\({}_{2}\)S ratio. It is shown that with increasing the number of CPSI, the honeycomb catalyst productivity can be significantly increased. The efficiency of H\({}_{2}\)S removal also increases with an increase of the specific surface (m\({}^{2}\)/m\({}^{3}\)).