Combination of modified molybdenum sulfide catalyst and non-thermal plasma for syngas production from H₂S-CO₂ acid gas

The petrochemical, natural gas, and coal chemical industries will produce a large number of hydrogen sulfide (H₂S) and carbon dioxide (CO₂) mixed acid gas, causing serious damage to the environment and human health. At present, the most widely used treatment technology for H₂S-containing mixed acid gas is the Claus process. Nevertheless, the Claus process is unable to achieve the recovery of hydrogen sources and the reduction of CO₂ emissions, resulting in a considerable quantity of CO₂ being discharged directly into the atmosphere, which has a detrimental impact on the global climate. Carbon, hydrogen, sulfur and other elements play an important role in the field of energy. Therefore, it is of great importance to explore new methods for the utilization of H₂S and CO₂ mixed acid gas to save energy, protect the environment and achieve green and low-carbon development. A non-thermal plasma-catalysis method is used to convert H₂S and CO₂ acid gas into syngas in a single step. This method achieves both the clean treatment of waste gas and its resource utilization, making it a novel route for syngas preparation. The non-thermal plasma contains high-energy electrons that can transfer energy to H₂S and CO₂ molecules in the form of inelastic collisions, thereby exciting them into free radicals, ions, excited molecules and atoms. Concurrently, the catalyst filled in the discharge gap can facilitate the chemical reactions of these active species. However, the stable molecular structure of H₂S and CO₂ presents a significant challenge to the improvement of energy efficiency, particularly in the context of high conversions of reactive molecule. The development of efficient catalysts is crucial to improve the H₂S and CO₂ conversion. The existing results demonstrate that electrons, photons and strong electric field generated by non-thermal plasma can be used to excite MoS₂ catalyst to generate highly active electron-hole pairs. These in turn catalyze the conversion of H₂S and CO₂. This study used copper and zinc as promoters to modify the molybdenum sulfide catalyst, and the catalytic performance for the conversion of H₂S-CO₂ to syngas was effectively improved. A detailed comparison was made between the effects of the two promoters on the structure, composition, morphology, valence state, and other physicochemical characteristics of the molybdenum sulfide catalyst using various characterization methods. Furthermore, the influence factors of two types of promoters on the catalytic H₂S-CO₂ conversion was investigated by controlling the discharge conditions. The introduction of copper and zinc promoters was found to result in a reduction in the particle size of the molybdenum sulfide active phase, accompanied by a high degree of dispersion, which in turn led to an increase in the number of active sites. Concurrently, the adsorption strength of H₂S and CO₂ molecules was enhanced, which was conducive to the adsorption and activation of H₂S and CO₂. It revealed the structure-activity relationship between the modified molybdenum sulfide catalyst and plasma synergistic reaction. In addition, the theoretical research has enriched and expanded the theory of non-thermal plasma-catalysis. It has also provided a reference for the synthesis of modified molybdenum sulfide materials.