Development Of Copper-based Catalyst And Its Mechanism For Low-temperature H₂S Catalytic Oxidation

As one of the seven major environmental hazards in the world,odor pollution has become a notorious environmental problem around the public because of its high toxicity and low olfactory threshold,which makes people feel out of sorts easily.Consequently,the high-performance removal of malodorous pollutants has become a research focus at present.Low temperature（<180℃）catalytic oxidation technology has the advantages of high desulfurization accuracy and no secondary pollution,which is especially suitable for efficient removal of malodorous gases.At present,the research core of this technology is the development of green and efficient catalysts.The preparation process of carbon-based materials with good effect is complex and difficult to popularize and apply.Oxidized metal-based catalysts with simple preparation process have the disadvantage of poor catalytic performance.To solve the existing problems,hydrogen sulfide（H₂S）is selected as a typical malodorous pollutant in this paper.Surface modification of oxide materials was carried out to study the H₂S removal performance.In addition,the relationship between environmental conditions,catalyst phase structure and active sites and their desulfurization performance was analyzed,and the mechanism of H₂S removal was revealed.The conclusions are as follows:（1）The catalytic oxidation removal of H₂S by copper-based catalyst(Cat_Cux)at low temperature and the surface phase change before and after reaction were studied.Copper-based catalysts supported on activated alumina were prepared by excessive impregnation method for selective catalytic oxidation removal of H₂S at low temperature.The results show that Cu/Al₂O₃ catalyst has good desulfurization performance and sulfur selectivity（100%）.Its penetration sulfur capacity can reach220.92 mg/g at 50℃and 50%relative humidity,which is higher than that of similar catalysts reported in current literature.（2）Based on Cat_Cu3,Nickel-copper bimetallic catalyst(Cat_{Nix Cuy})was prepared by doping promoter Ni.The influence of environmental factors and Ni loading on the desulfurization performance of the catalyst were analyzed,and the desulfurization mechanism was expounded.The characterization results show that the Cat_{Nix Cuy} has good surface structure of 3D network nanosheets,high surface alkaline sites and hydrophilicity.Cat_Ni2.5Cu3 shows excellent desulfurization performance（304.9 mg/g）and sulfur selectivity（100%）.Based on the experimental and characterization results,the desulfurization mechanism of Cat_{Nix Cuy} catalyst was put forward.The characterization results show that water molecules adsorbed on the surface can be catalyzed and decomposed by oxygen vacancies（VOs）provided by Cu₂O and Cu O to generate hydroxyl radicals（·OH）,and at the same time react with Ni²⁺to generate alkaline environment to accelerate the capture and removal of H₂S.From the foregoing discussion,the desulfurization mechanism of Cat_{Nix Cuy} catalyst was put forward.（3）The effects of different conditions on the removal of H₂S by catalytic oxidation of Cat_{Znx Cuy} catalyst at low temperature were studied,and the desulfurization mechanism was clarified.The experimental results show that temperature,humidity and Zn loading have great influence on the catalytic performance.The addition of Zn O provides more oxygen vacancies on the catalyst surface,and the increase of oxygen vacancy leads to the improvement of H₂S catalytic performance of the copper-based catalyst.Under the conditions of 50℃and 50%relative humidity,the sulfur capacity of Cat_Zn3Cu3 is as high as 353.91 mg/g catalyst,which is 2-3 times higher than the low-temperature catalytic effect of similar catalysts reported at present.The characterization results show that VOs can catalyze and decompose water molecules adsorbed on the surface to form·OH,and provide metal cations to react with H₂S at the same time.Based on this,a·OH-induce desulfurization mechanism was proposed.