| The higher alcohols synthesis from syngas has become an important way to solve environmental problems and achieve sustainable energy development,which is a hot topic in the field of energy catalysis.Since the reaction system is complicated and the reaction products are numerous,designing and developing highly active and highly selective catalysts are the key to improve the reaction efficiency and reduce the industrial cost.In molybdenum-based catalysts,Mo P-based catalysts have higher total alcohol and C2+ oxide selectivity,but their CO conversion is too low;meanwhile,the CO conversion of Cu Co-based catalysts strongly depends on the preparation method of the catalysts.Therefore,in this thesis,by combining the low-temperature plasma characteristics,the Mo P and the Cu Co catalysts were modified and prepared by the different low-temperature plasma technology and the relationship between the structure and activity of the catalysts in the higher alcohols synthesis reaction was studied.The Mo P catalyst(TPR-Mo P)prepared with the traditional method was modified under the different conditions by controlling the generation power of the low-temperature glow cold plasma reaction equipment,and the products were characterized in detail by XRD,TEM,CO-TPD,XPS and Raman,and their catalytic performance for syngas to higher alcohols synthesis was compared.The results show that the different generation power of the plasma has a great influence on the surface structure,chemical composition and catalytic performance of the catalysts.Considering comprehensively,the optimal power of the plasma for this catalyst is 400 W,and the surface of the catalyst has lots of discontinuous lattice defects after repeated treatment many times,which can increase its catalytic activity significantly.The CO conversion can reach 33.0%,the C2+OH selectivity and STY are 54.1% and 177.0 mg/g/h,respectively,at the reaction condition of 330 °C and 8 MPa.At the same time,the etching degree for the Mo P catalysts prepared by pyrolysis(Ar-Mo P)and the citric acid induced method(CA-Mo P)was compared under the optimum generation power of the glow plasma,and the relationship between the catalyst structure and properties and the degree of plasma etching was investigated.The results show that the activity of Ar-Mo P catalyst is almost unchanged after the plasma etching because the catalyst surface was coated by the carbon material and the number of active sites does not increase significantly,but the defects on surface carbon material and part of the active phase of the catalyst caused the selectivity of the total alcohol and C2+OH to increase.However,after the plasma etching of the nano-particle CA-Mo P catalyst,more active sites are exposed,leading to the significant improvement of catalytic activity and slight increase of the selectivity of total alcohols and C2+OH.In order to synthesize highly dispersed nanoparticle catalysts,the copper-cobalt nano-alloy catalysts were in-situ synthesized by low-temperature radio frequency induction thermal plasma technology,and the phase,morphology,the surface chemical state and the catalytic performance of the catalysts were compared with that of the sample prepared by conventional thermal reduction methods.It shows that the catalyst prepared by plasma method exhibited the advantages of strong interaction between copper and cobalt active species,smaller size of the catalyst particle,good dispersion and high catalytic activity.When the reaction temperature and pressure are 330 °C and 5 MPa respectively,the best catalytic performance was obtained with CO conversion of 32.9% and the C2+OH distribution of 69.3% in the total alcohols. |
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