Study On Highly Effective Decomposition Of H₂S Into H₂ And S Over Core-shell Microwave Catalysts And Its Microwave Catalytic Effects

Due to its high toxicity,the resource value of hydrogen sulfide itself has not been fully recognized.At present,the Claus method is often used to treat H₂S exhaust gas.Although the sulfur resource is recovered by this method,the precious hydrogen is converted into water,resulting in a great waste of hydrogen resources.If H₂ needed for petroleum refining can be further obtained from the H₂S exhaust gas produced,the problem of H₂S exhaust gas pollution generated in the petroleum and natural gas industry can be solved,the high value conversion of H₂S resources can be realized,and the fossil resource consumption and CO₂ emission caused by traditional hydrogen reforming can be reduced.Therefore,the direct decomposition of H₂S to produce hydrogen and sulfur,to replace the Claus process,is an ideal route that can not only treat H₂S waste gas but also recover H₂,which has huge social,economic and ecological environmental benefits.However,the direct decomposition reaction of H₂S is limited by thermodynamic equilibrium,and its equilibrium conversion rate is very low even at high temperature（e.g.,only 20%at 1130°C）.On the other hand,due to the high apparent activation energy（Ea’）to 495.62 k J/mol,it is also difficult to proceed kinetically.In this paper,a new method of high efficiency decomposition of H₂S at low temperature by microwave catalysis was proposed.A series of new core-shell catalysts with high activity were developed.At the same time,the absorption and catalytic properties of the catalyst were systematically studied,and characterized by XRD,TEM,XPS,FT-IR,BET,etc.Specific research contents are as follows:（1）The MoO₂ nanoparticles containing carbon were prepared by solvothermal method,and then TiO₂ coated them in situ to form a new core-shell structured MoC@TiO₂ microwave catalyst.Under microwave irradiation,the H₂S conversion of MoC@TiO₂ catalyst reached 94.2%at 650°C,which was much higher than the H₂S equilibrium conversion under the corresponding traditional thermal reaction conditions.（2）The MoO₂ nanoparticles containing carbon were prepared by solvothermal method,and then BN coated them in situ to form a new core-shell microwave catalyst Mo₂C@BN.Under microwave irradiation,the H₂S conversion of Mo₂C@BN catalyst reached 99.9%at 650°C,and almost complete decomposition.Surprisingly,the H₂S conversion of the catalyst was much higher than the H₂S equilibrium conversion under the traditional thermal reaction conditions.（3）The MoO₂ nanoparticles containing carbon were prepared by solvothermal method,and then coated with chemically inert Zr O₂ to form new core-shell microwave catalyst MoC-Mo₂C@Zr O₂ in situ.Under microwave irradiation,the H₂S conversion of MoC-Mo₂C@Zr O₂ catalyst reached 99.9%at 650°C,which was much higher than the H₂S equilibrium conversion.（4）It is found that microwave selective catalysis can break the limit of chemical equilibrium in the direct decomposition of H₂S by microwave catalysis.The interaction between microwave electromagnetic field and H₂S polar molecules is more conducive to promoting its activation,while H₂ and S are non-polar molecules,which cannot be activated by microwave.Therefore,microwave selective catalysis selectively accelerates the forward reaction of the reversible reaction of H₂S decomposition.The direct microwave catalytic effect was found.Under microwave irradiation,the Ea’of MoC@TiO₂,Mo₂C@BN and MoC-Mo₂C@Zr O₂ microwave catalysts for the direct decomposition of H₂S decreased to 23.16,14.69 and 14.46k J/mol,respectively.