# Direct Selective Oxidation of Hydrogen Sulfide: Laboratory, Pilot and Industrial Tests
###### Abstract  
This article is devoted to scientific and technical aspects of the direct catalytic oxidation of hydrogen sulfide for the production of elemental sulfur. It includes a detailed description of the Claus process as the main reference technology for hydrogen sulfide processing methods. An overview of modern catalytic systems for direct catalytic oxidation technology and known processes is presented. Descriptions of the scientific results of the Institute of Catalysis of the SB RAS in a study of the physical and chemical foundations of the process and the creation of a catalyst for it are included. The Boreskov Institute of Catalysis SB RAS technologies based on fundamental studies and their pilot and industrial testing results are described.  
gas purification; hydrogen sulfide; direct catalytic oxidation; fluidized catalyst bed; hydrogen sulfide removal facilities +
Footnote †: journal: _catallysts_  
0000-0002-219-7201-0101]M.S.  
The ecological effects of burning are significantly worsened due to the flare disposal of hydrogen sulfide-containing oil-associated gases (OAG). The burning of one billion nm\({}^{3}\) of OAG results in atmospheric emissions of up to 60,000 tons of highly toxic H\({}_{2}\)S, SO\({}_{2}\) and SO\({}_{3}\), soot, carbon monoxide, and up to 3 million tons of carbon dioxide, as well as, which is no less important, the loss of hundreds of millions of cubic meters of hydrocarbons, raw materials for oil and gas chemistry. For example, the qualified processing of 1000 m\({}^{3}\) of associated gas produces 820 m\({}^{3}\) of dry gas, 200 kg of a wide fraction of light hydrocarbons, and up to 61 kg of stable gasoline [8].  
Given the global relevance of these problems, a wide range technologies which make use of sulfurous compounds have been implemented; however, the strengthening of environmental protection requirements dictates the need to create new technologies. These technologies must be highly efficient with a wide range of purified gases, and must minimize environmental damage while maximizing the yield valuable products. Such technologies should also meet the requirements of compactness and ease of process control.  
To this end, catalytic methods are the most attractive, as they allow the conversion of highly hazardous hydrogen sulfide into a nontoxic, marketable product, i.e., elementary sulfur. Basic processes for hydrogen sulfide-to-sulfur conversion are the direct oxidation of H\({}_{2}\)S into elementary sulfur and the low-temperature reduction of sulfur dioxide.  
Due to the relevance of the aforementioned problems, this paper describes attempts to develop and improve the processes of purification and processing of hydrogen sulfide-containing gases. At present, three main categories of methods for cleaning gases from hydrogen sulfide can be distinguished:  
* adsorption methods
* catalytic methods  
The general feature of the first two methods is that they are essentially ways to concentrate hydrogen sulfide from a purified gas, and must operate jointly with sulfur production plants using the Claus method. This process is currently the only large-tonnage method which is able to obtain sulfur from highly concentrated hydrogen sulfide-containing gas streams. It is characterized by:  
* multistage operation
* insufficient environmental safety, due to the presence of a high-temperature furnace in the technological chain, which is a source of toxic byproducts
* a limited range of applications (thus, it is impossible to treat gases with hydrogen sulfide contents below 20 vol.% or gas streams with flow rates below 1000 Nm\({}^{3}\)/h).  
Therefore, as a supplement or alternative to the Claus process, direct selective catalytic oxidation of hydrogen sulfide to elemental sulfur is currently being explored.