采用氢化脱氢(hydrogenation-dehydrogenation,HDH)工艺制备不规则形状Nb521合金粉末,结合流化技术将氢化脱氢粉末进行改性处理,改善粉末球形度及流动性,所制流化Nb521合金粉末基本满足3D打印的工艺要求。通过X射线衍射(X-ray diffracti...采用氢化脱氢(hydrogenation-dehydrogenation,HDH)工艺制备不规则形状Nb521合金粉末,结合流化技术将氢化脱氢粉末进行改性处理,改善粉末球形度及流动性,所制流化Nb521合金粉末基本满足3D打印的工艺要求。通过X射线衍射(X-ray diffraction,XRD)分析、扫描电子显微镜(scanning electron microscope,SEM)观察、粒度分析、化学分析等手段,对粉末形貌、粒度分布、间隙元素含量、球形率以及流动性等特性进行表征。结果表明,经流化处理后,不规则形状的氢化脱氢Nb521合金粉末粒度分布变窄,球形率和流动性均得到显著提高,杂质元素含量得到有效控制,3D打印过程中的铺粉效果良好。展开更多
Producing methanol from coke oven gas(COG) is one of the important applications of COG. Removal of sulfur from COG is a key step of this process. Conversion and reaction kinetics over a commercial Fe-Mo/Al2O3 catalyst...Producing methanol from coke oven gas(COG) is one of the important applications of COG. Removal of sulfur from COG is a key step of this process. Conversion and reaction kinetics over a commercial Fe-Mo/Al2O3 catalyst(T-202) were studied in a continuous flow fixed bed reactor under pressures of 1.6-2.8 MPa, space time of 1.32-3.55 s and temperatures of 240-360 °C. Though the COG contains about 0.6 mol/mol H2, hydrogenation of CO and CO2 is not significant on this catalyst. The conversions of unsaturated hydrocarbons depend on their molecular structures. Diolefins and alkynes can be completely hydrogenated even at relatively low temperature and pressure. Olefins, in contrast, can only be progressively hydrogenated with increasing temperature and pressure. The hydrodesulfurization(HDS) of CS2 on this catalyst is easy. Complete conversion of CS2 was observed in the whole range of the conditions used in this work. The original COS in the COG can also be easily converted to a low level. However, its complete HDS is difficult due to the relatively high concentration of CO in the COG and due to the limitation of thermodynamics. H2 S can react with unsaturated hydrocarbons to form ethyl mercaptan and thiophene, which are then progressively hydrodesulfurized with increasing temperature and pressure. Based on the experimental observations, reaction kinetic models for the conversion of ethylene and sulfur-containing compounds were proposed; the values of the parameters in the models were obtained by regression of the experimental data.展开更多
To evaluate the influence of various Cr(Ⅵ) concentrations (0.05, 0.25, 0.50, 1.00 and 2.00 g/kg) on the activity of soil enzymes, the activities of catalase, polyphenol oxidase, dehydrogenase, alkaline phosphatase in...To evaluate the influence of various Cr(Ⅵ) concentrations (0.05, 0.25, 0.50, 1.00 and 2.00 g/kg) on the activity of soil enzymes, the activities of catalase, polyphenol oxidase, dehydrogenase, alkaline phosphatase in soils were investigated in the incubation experiment with a period of 35 d. The results indicate that all the tested Cr(Ⅵ) concentrations significantly inhibit dehydrogenase activity by over 70% after 35 d. The activity of alkaline phosphatase is slightly inhibited during the whole experiment except for on the day 7. Cr(Ⅵ) has no obvious effect on the activity of catalase in soil. On the contrary, Cr(Ⅵ) stimulates the activity of polyphenol oxidase. The results suggest that dehydrogenase activity can be used as an indicator for assessing the severity of chromium pollution.展开更多
文摘采用氢化脱氢(hydrogenation-dehydrogenation,HDH)工艺制备不规则形状Nb521合金粉末,结合流化技术将氢化脱氢粉末进行改性处理,改善粉末球形度及流动性,所制流化Nb521合金粉末基本满足3D打印的工艺要求。通过X射线衍射(X-ray diffraction,XRD)分析、扫描电子显微镜(scanning electron microscope,SEM)观察、粒度分析、化学分析等手段,对粉末形貌、粒度分布、间隙元素含量、球形率以及流动性等特性进行表征。结果表明,经流化处理后,不规则形状的氢化脱氢Nb521合金粉末粒度分布变窄,球形率和流动性均得到显著提高,杂质元素含量得到有效控制,3D打印过程中的铺粉效果良好。
文摘Producing methanol from coke oven gas(COG) is one of the important applications of COG. Removal of sulfur from COG is a key step of this process. Conversion and reaction kinetics over a commercial Fe-Mo/Al2O3 catalyst(T-202) were studied in a continuous flow fixed bed reactor under pressures of 1.6-2.8 MPa, space time of 1.32-3.55 s and temperatures of 240-360 °C. Though the COG contains about 0.6 mol/mol H2, hydrogenation of CO and CO2 is not significant on this catalyst. The conversions of unsaturated hydrocarbons depend on their molecular structures. Diolefins and alkynes can be completely hydrogenated even at relatively low temperature and pressure. Olefins, in contrast, can only be progressively hydrogenated with increasing temperature and pressure. The hydrodesulfurization(HDS) of CS2 on this catalyst is easy. Complete conversion of CS2 was observed in the whole range of the conditions used in this work. The original COS in the COG can also be easily converted to a low level. However, its complete HDS is difficult due to the relatively high concentration of CO in the COG and due to the limitation of thermodynamics. H2 S can react with unsaturated hydrocarbons to form ethyl mercaptan and thiophene, which are then progressively hydrodesulfurized with increasing temperature and pressure. Based on the experimental observations, reaction kinetic models for the conversion of ethylene and sulfur-containing compounds were proposed; the values of the parameters in the models were obtained by regression of the experimental data.
基金Projects(2006AA06Z374, 2007AA021304) supported by the National High-Tech Research and Development Program of ChinaProject(2008SK2007) supported by the Key Program of Science and Technology of Hunan Province, China
文摘To evaluate the influence of various Cr(Ⅵ) concentrations (0.05, 0.25, 0.50, 1.00 and 2.00 g/kg) on the activity of soil enzymes, the activities of catalase, polyphenol oxidase, dehydrogenase, alkaline phosphatase in soils were investigated in the incubation experiment with a period of 35 d. The results indicate that all the tested Cr(Ⅵ) concentrations significantly inhibit dehydrogenase activity by over 70% after 35 d. The activity of alkaline phosphatase is slightly inhibited during the whole experiment except for on the day 7. Cr(Ⅵ) has no obvious effect on the activity of catalase in soil. On the contrary, Cr(Ⅵ) stimulates the activity of polyphenol oxidase. The results suggest that dehydrogenase activity can be used as an indicator for assessing the severity of chromium pollution.
