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Prepaaration Of Metal Oxide Catalysts With Different Morphologies And The Study Of CO Shift Reaction

Posted on:2018-01-07Degree:MasterType:Thesis
Country:ChinaCandidate:F PengFull Text:PDF
GTID:2321330518994208Subject:Chemical Engineering and Technology
Abstract/Summary:PDF Full Text Request
Proton exchange membrane fuel cell?PEMFC?application as the background,for the purpose of exploring shift catalysts of high CO shift rate and hydrogen production efficiency,we systematically studied Cu/CeO2 catalysts to investigate the effect of different morphologies CeO2,different active components and their loading on catalytic performance of CO shift reaction.The role of small molecular gas assisted synthesis of ZrO2 support in Cu/ZrO2 catalysts were investigated preliminarily.First,we successfully prepared octahedron,rod and cube three CeO2 materials with different morphologies.We found that the CO shift reaction activity were low?under experimental condition CO conversion didn't reach 8%?and there was no difference between them.Then copper was loaded and three Cu/CeO2 catalysts with different morphologies were gained.The comparison experiment of 5%Cu/CeO2 catalysts as an example indicated that after loading the maximum CO conversion could reach 91%.When the temperature exceeded 350 ?,the shift reaction was already close to equilibrium on the octahedral and rod catalysts.Among the results,Cu/CeO2 octahedron catalyst had the best shift performance,followed by rod,cube was the worst.The characterization results proved that octahedral CeO2 had the smallest particle size;the interaction between Cu and Ce was strongest in Cu/CeO2 catalyst.CuO dispersed best and small size copper specie was the most.Moreover,octahedral catalysts had more Cu+ specie and surface chemisorbed oxygen.Under the effect of these factors,Cu/CeO2 octahedron catalyst performed best in CO shift reaction.Then,the effect of active components on catalytic performance was explored.We found that 10%copper content was the optimum loading of Cu/CeO2 catalyst.The characterization results showed that CuO was still highly dispersed at 10%loading content.However,as the loading increased continuously,crystal phase CuO appeared in the catalyst.The interaction between Cu and Ce was strongest in 10%Cu/CeO2 catalyst and it had more surface chemisorbed oxygen and oxygen vacancies.In-situ DRIFTS experiments further revealed that mono-dentate and poly-dentate carbonates might be the key species of Cu/CeO2 catalyst at low temperature.And surface formates of the catalyst might be a key specie under high temperature conditions.Besides,after loading Co and Ni,it was found that CO conversion increased,but the methanation side reaction intensified.Among the results,Ni element had an obvious methanation effect.It was not a suitable added component of the CeO2-based shift catalysts.Considering both hydrogen production and CO removal efficiency,bimetallic supported Cu-Co/CeO2 catalyst was the best.The CO conversion was 96%and selectivity of CH4 was 1%Finally,CO and H2 small molecule gases were introduced to oriented synthesized ZrO2 materials under different conditions.Then Cu/ZrO2-None,Cu/ZrO2-CO and Cu/ZrO2-H2 three catalysts were prepared to study their shift reaction performance.The evaluation and characterization results showed that the catalysts performed better after regulating by the small molecule gases.The electron transition energy of the regulating catalysts were lower and the content of small size ?+? phase in CuO were higher.The catalysts also had more Cu+ specie and surface chemisorbed oxygen.Therefore,we can know that small molecule gas-assisted synthesis was an effective way to improve the catalytic performance of ZrO2-based catalysts.
Keywords/Search Tags:CO shift reaction, Morphology control, Cu/CeO2 catalysts, Small molecule gas assist, Cu/ZrO2 catalysts
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