Modification Of SBA-15 And Its Study On Hydrogen Production By Ethanol Steam Reforming

In recent years,the rapid development of fuel cell technology has an inseparable relationship on the reason why hydrogen can get more and more widespread attention.However,fossil fuels,which are the main source of hydrogen,are not sustainable sources of energy.In order to make full use of hydrogen energy as the main energy carrier in the future,we need new technologies for producing hydrogen from renewable energy.At present,one very promising route for the production of hydrogen is steam reforming of ethanol.Mesoporous silica molecular sieve was extensively researched by researchers in recent years,because of its thick wall and better hydrothermal stability.However,the research on the modification of molecular sieve has been more and more popular now.For example,the incorporation of metals into the framework of the molecular sieve has a good effect in improving the stability and reactivity for use as a catalyst support for the reaction.In this paper,in the hydrothermal synthesis of SBA-15,we add a certain amount of cobalt nitrate and adjust the pH of the mixed solution to prepare Co-SBA-15.By XRD,Nitrogen adsorption and desorption,H₂-TPR,FT-IR and UV-visible diffuse reflectance,the results show that SBA-15 after the introduction of Co still retains a good mesoporous structure.The Co is highly dispersed in the mesoporous molecular sieve,and the Co entering the skeleton is mainly in the isolated Co?II?state and in the form of tetracoordinate.In order to explore the influence of the introduction of metallic cobalt in the SBA-15 framework on the steam reforming reaction of ethanol,SBA-15 and Co-SBA-15?designated as S1?were used as carriers,and cobalt nitrate was used as a cobalt source to prepare Co/SBA-15 and Co/S1 catalysts with 10wt%of cobalt.S1,Co/SBA-15 and Co/S1 catalysts were used to investigate the catalytic effect on the reaction at different temperatures.The XRD patterns of the above three catalysts showed that the Co₃O₄ phase existed on the surface of Co/SBA-15 and Co/S1 catalysts.After reduction at 400?in a hydrogen atmosphere,the phases of the metal Co and CoO are present on both catalyst surfaces.No characteristic diffraction peak of Co was observed before and after the S1 catalyst was reduced.The catalytic effects of the three catalysts are significantly different under different reaction conditions.The S1 catalyst has almost no catalytic activity below 450?,which is due to the lack of active component on the surface.Below 500?,the hydrogen selectivity of the Co/S1catalyst is much higher than that of the Co/SBA-15 catalyst,and the selectivity to acetaldehyde is 15%-20%lower than that of the Co/SBA-15 catalyst.Based on this,it can be inferred that after the introduction of cobalt metal in the molecular sieve,the C-C bond-breaking ability of the catalyst is enhanced under low temperature conditions.Four kinds of catalysts with different loadings?5,10,15 and 20wt%?supported on Co-SBA-15 were prepared using cobalt nitrate as cobalt source.The results show that only Co₃O₄ phases are formed on the surface of the catalysts after calcination.However,after reaction at different temperatures,it was found that the catalytic activity of the catalysts does not always increase with the increase of the load.When the load is too large,it will have a negative impact on the reaction.The results showed that when the loading was 10%and the reaction temperature was 500?,the catalytic effect was optimal.