The promotional effects of Zr on the structure, reduction, carburization and catalytic behavior of precipitated iron-based Fischer-Tropsch synthesis （FTS） catalysts were investigated. The catalysts were characterize...The promotional effects of Zr on the structure, reduction, carburization and catalytic behavior of precipitated iron-based Fischer-Tropsch synthesis （FTS） catalysts were investigated. The catalysts were characterized by N2 physisorption, temperature-programmed reduction （TPR）, and M6ssbauer effect spectroscopy （MES） techniques. As revealed by N2 physisorption, Zr decreased the BET surface area and pore volume of the catalyst. The results of TPR and MES show that Zr suppresses the reduction and carburization of Fe catalysts because of the interaction between Fe and Zr. The FTS reaction results indicate that Zr decreases the FTS activity of Fe catalysts but improves the catalysts＇ stability. In addition, Zr promoter restraines the formation of light hydrocarbons （methane and C2-C4） and shifts the production distribution to the heavy hydrocarbons.展开更多
Catch crops that are cultivated for green manure play an important role in improving soil properties. A 3-year field experi- ment was conducted to investigate the effect of catch crop （pea, Pisum sativum L.） managem...Catch crops that are cultivated for green manure play an important role in improving soil properties. A 3-year field experi- ment was conducted to investigate the effect of catch crop （pea, Pisum sativum L.） management, i.e., incorporation of catch crop in October/November （autumn） and March （spring）, and without catch crop （control）, on soil organic carbon （SOC）, microbial biomass carbon （MBC） and the activities of carbon （C）-cycle enzymes, including cellulase （Cel）, β-glucosidase （Glu） and invertase （Inv）. Additionally, soil total nitrogen （TN） and pHKcl were investigated. The catch crop was cultivated from August to October each year during 2008-2010. Soil samples were collected from the field of spring barley （Hordeum vulgate L.） that had been grown after the catch crop. Soil samples for microbial activity determination were taken in March, May, June and August in 2009, 2010 and 2011, while SOC and TN contents as well as pHKc1 were determined in March and August. The chemical properties studied did not show significant changes as influenced by the experimental factors. The use of catch crop significantly increased the MBC content and the activities of C-cycle enzymes compared to the control. When the catch crop was incorporated in spring, a significantly higher MBC content was noted in March and May compared to autumn incorporation. Moreover, the spring incorporation of the catch crop significantly increased the Glu activity （except March）, while the activities of Cel and Inv as well as the rate of soil basal respiration were usually unaffected by the time of catch crop incorporation. Greater microbial biomass and higher enzyme activities in the catch crop-treated soil, compared to the control, indicated that the application of the catch crop as a green manure could be recommended as a promising technique to increase the biological activity of the soil. Since there was no significant effect or no consistent results were obtained related to the time of catch crop incorporation, both spring and autumn applications can be recommended as a management tool to improve the status of soil properties during the growth of a subsequent crop.展开更多
文摘The promotional effects of Zr on the structure, reduction, carburization and catalytic behavior of precipitated iron-based Fischer-Tropsch synthesis （FTS） catalysts were investigated. The catalysts were characterized by N2 physisorption, temperature-programmed reduction （TPR）, and M6ssbauer effect spectroscopy （MES） techniques. As revealed by N2 physisorption, Zr decreased the BET surface area and pore volume of the catalyst. The results of TPR and MES show that Zr suppresses the reduction and carburization of Fe catalysts because of the interaction between Fe and Zr. The FTS reaction results indicate that Zr decreases the FTS activity of Fe catalysts but improves the catalysts＇ stability. In addition, Zr promoter restraines the formation of light hydrocarbons （methane and C2-C4） and shifts the production distribution to the heavy hydrocarbons.
文摘Catch crops that are cultivated for green manure play an important role in improving soil properties. A 3-year field experi- ment was conducted to investigate the effect of catch crop （pea, Pisum sativum L.） management, i.e., incorporation of catch crop in October/November （autumn） and March （spring）, and without catch crop （control）, on soil organic carbon （SOC）, microbial biomass carbon （MBC） and the activities of carbon （C）-cycle enzymes, including cellulase （Cel）, β-glucosidase （Glu） and invertase （Inv）. Additionally, soil total nitrogen （TN） and pHKcl were investigated. The catch crop was cultivated from August to October each year during 2008-2010. Soil samples were collected from the field of spring barley （Hordeum vulgate L.） that had been grown after the catch crop. Soil samples for microbial activity determination were taken in March, May, June and August in 2009, 2010 and 2011, while SOC and TN contents as well as pHKc1 were determined in March and August. The chemical properties studied did not show significant changes as influenced by the experimental factors. The use of catch crop significantly increased the MBC content and the activities of C-cycle enzymes compared to the control. When the catch crop was incorporated in spring, a significantly higher MBC content was noted in March and May compared to autumn incorporation. Moreover, the spring incorporation of the catch crop significantly increased the Glu activity （except March）, while the activities of Cel and Inv as well as the rate of soil basal respiration were usually unaffected by the time of catch crop incorporation. Greater microbial biomass and higher enzyme activities in the catch crop-treated soil, compared to the control, indicated that the application of the catch crop as a green manure could be recommended as a promising technique to increase the biological activity of the soil. Since there was no significant effect or no consistent results were obtained related to the time of catch crop incorporation, both spring and autumn applications can be recommended as a management tool to improve the status of soil properties during the growth of a subsequent crop.
