Study On Medium Temperature Natural Gas Steam Reforming Catalyst And Palladium Membrane Of Hydrogen Separation

Hydrogen energy is one of the most promising clean energy sources in the 21st century,and it is of great significance to achieving carbon neutrality.Steam methane reforming is one of the main ways to produce large-scale hydrogen in industry.In view of the harsh reaction conditions of steam methane reforming and the problems of small-scale hydrogen production that is not suitable for distributed energy resources,this thesus couples steam methane reforming technology with a palladium membrane reactor,and breaks the thermodynamic balance of steam reforming by separating the generated hydrogen in real time to achieve small-scale in situ hydrogen production at medium temperature（500-600°C）.For the medium temperature steam methane reforming reaction,this thesis firstly uses Aspen Plus to simulate and analyze the reaction conditions.Then the influence factors such as supports,calcined temperature,Ni O loadings,additives and preparation methods that are suitable for the medium temperature reforming catalyst are investigated.The optimized catalyst is combined with palladium membrane the reactor,an integrated evaluation study of reaction and separation was carried out,and the following conclusions are summarized:The thermodynamic simulation results show that increasing temperature,decreasing pressure and increasing H₂O/CH₄ are beneficial to the conversion of methane;the increase of temperature,pressure and H₂O/CH₄ are beneficial to reduce carbon deposition,of which pressure has the greatest effect.The optimized reforming catalyst is MNA2-60 prepared by a step-by-step impregnation method with magnesium-aluminum composite oxide A2 as the support.For example,when the pressure is 1.0MPa,the temperature is 600℃,H₂O/CH₄is 3,and GHSV（CH₄）is 12000 h^-1 in a fixed-bed reactor,the methane conversion is 31.90%,and the hydrogen content in the product dry gas is 46.08%.The selectivity test results of Pd/Au alloy membrane show that reducing the temperature and transmembrane pressure and increasing the flow of the separated gas is beneficial to improve the H₂/N₂ selectivity;adding H₂O to the mixture of CO₂ and H₂ is beneficial to improve the purity of hydrogen;non-permeable gases such as CH₄,CO and CO₂ in the steam reforming product gas has an inhibitory effect on the separation of hydrogen.The research results of combining steam reforming and palladium membrane reactor to realize the integrated reaction and separation of hydrogen production show that the methane conversion can be improved by increasing the reaction temperature,transmembrane pressure and H₂O/CH₄,and reducing GHSV（CH₄）.When the temperature is 600℃,the transmembrane pressure is 0.9 MPa（the permeate side is 0.1MPa）,H₂O/CH₄ is 3,and GHSV（CH₄）is 100 h^-1,the methane conversion is 96.22%,the H₂ yield is 90.81%,and the purity is 99.27%.By increasing GHSV（CH₄）to 1000 h^-1,the methane conversion is 78.78%in the palladium membrane reactor,which is 41.46%higher than that in the fixed bed reactor.while the H₂ purity is 99.83%and the H₂ yield is 72.41%,which realizing the hydrogen production integrating medium temperature steam reforming reaction and separation.