The promoting effect of La2O3 on Ni/γ-Al2O3 methanation catalyst was investigated by XPS, TPR and TPD methods. Results indicated that La2O3 can be partially reduced to LaOx (x＜3/2) during H2 reduction of the Ni cata...The promoting effect of La2O3 on Ni/γ-Al2O3 methanation catalyst was investigated by XPS, TPR and TPD methods. Results indicated that La2O3 can be partially reduced to LaOx (x＜3/2) during H2 reduction of the Ni catalysts with La2O3.The excess charge associated with the LaOx can be transfered to Ni. It weakened C-O bond strength, accelerated CO dissociation, proportionation and methanation reaction.The interaction between NiO and Al2O3 can be suppressed and the formation of NiAl2O4-like species can be reduced by adding La2O3. With the increase of La2O3 con tents the fraction of NiO which is easier to be reduced becomes larger.The fact that there was more residual H2 on the catalyst with La2O3 means that it is able to retain some H2. Besides, the distribution of CO adsorption sites of the Ni catalyst was shifted by adding La2O3.展开更多
High pressure steam gas tube is studied by the SEM after the high temperature running. The material of the high pressure steam gas tube is 12Cr1MoV. Meanwhile, the new tube of the same material was tested respectively...High pressure steam gas tube is studied by the SEM after the high temperature running. The material of the high pressure steam gas tube is 12Cr1MoV. Meanwhile, the new tube of the same material was tested respectively. The analysis included mechanic capability, metal phase, chemical electrolysis and X ray diffraction analysis. In this paper, the failure regularity was further discussed. The annual oxidation rate at the surface of 12Cr1MoV high pressure steam gas tube was about 10μm during its service. The surface oxidation was more harmful to the small caliber tube than to the big caliber tube. It was noticed that the carbide in the pearlite could be gradually decomposed during the high temperature running, which results in more carbon and chromium diffused to the crystal interface and formation of the uneven distributed carbide of chromium. It could further increased the recrystal temperature of the matrix, thus the structure had the enough stability and high persistent strength. The calculation of the persistent strength and accepted stress of the high pressure steam gas tube showed that, the verdict standard of 117MPa or the big caliber tube was conservative and could not fully use the tube, now the big caliber tube is at its old age of service.展开更多
文摘The promoting effect of La2O3 on Ni/γ-Al2O3 methanation catalyst was investigated by XPS, TPR and TPD methods. Results indicated that La2O3 can be partially reduced to LaOx (x＜3/2) during H2 reduction of the Ni catalysts with La2O3.The excess charge associated with the LaOx can be transfered to Ni. It weakened C-O bond strength, accelerated CO dissociation, proportionation and methanation reaction.The interaction between NiO and Al2O3 can be suppressed and the formation of NiAl2O4-like species can be reduced by adding La2O3. With the increase of La2O3 con tents the fraction of NiO which is easier to be reduced becomes larger.The fact that there was more residual H2 on the catalyst with La2O3 means that it is able to retain some H2. Besides, the distribution of CO adsorption sites of the Ni catalyst was shifted by adding La2O3.
文摘High pressure steam gas tube is studied by the SEM after the high temperature running. The material of the high pressure steam gas tube is 12Cr1MoV. Meanwhile, the new tube of the same material was tested respectively. The analysis included mechanic capability, metal phase, chemical electrolysis and X ray diffraction analysis. In this paper, the failure regularity was further discussed. The annual oxidation rate at the surface of 12Cr1MoV high pressure steam gas tube was about 10μm during its service. The surface oxidation was more harmful to the small caliber tube than to the big caliber tube. It was noticed that the carbide in the pearlite could be gradually decomposed during the high temperature running, which results in more carbon and chromium diffused to the crystal interface and formation of the uneven distributed carbide of chromium. It could further increased the recrystal temperature of the matrix, thus the structure had the enough stability and high persistent strength. The calculation of the persistent strength and accepted stress of the high pressure steam gas tube showed that, the verdict standard of 117MPa or the big caliber tube was conservative and could not fully use the tube, now the big caliber tube is at its old age of service.
