The article describes ethylene polymerization reactions with transition metal catalysts based on complexes of CoCl_(2) and FeCl_(2) with an N,N,N-tridentate ligand 2,6-bis[1-(2,6-dimethylphenylimino)ethyl]pyridine. Th...The article describes ethylene polymerization reactions with transition metal catalysts based on complexes of CoCl_(2) and FeCl_(2) with an N,N,N-tridentate ligand 2,6-bis[1-(2,6-dimethylphenylimino)ethyl]pyridine. The complexes are converted into polymerization catalysts by reacting them either with polymethylalumoxane (MAO) or with a combination of Al(C2H5)2Cl and Mg(C4H9)2 at an [Al]:[Mg] ratio of ~3. Both MAO-activated complexes readily polymerize ethylene at 35 ℃ with the formation of linear, low molecular weight polymers with a narrow molecular weight distribution. The same complexes, when activated with the Al(C2H5)2Cl-Mg(C4H9)2 combination, form multi-center catalysts and generate polyethylenes with a broad molecular weight distribution.展开更多
Soil low-molecular-weight （LMW） organic acids play important roles in the soil-forming process and the cycling of nutrients in Karst regions. In this study, we quantified the contents of LMW organic acids （includin...Soil low-molecular-weight （LMW） organic acids play important roles in the soil-forming process and the cycling of nutrients in Karst regions. In this study, we quantified the contents of LMW organic acids （including lactate, acetate, formate, malate, and oxalate） in soil solution over the Karst region of Guizhou Province, China using ion chromatography. The concentration of total LMW organic acids in topsoil solution ranged from 0.358 to 1.823pmol＇g-1, with an average of 0.912p.mol.gL The mean concentrations of lactate, acetate, formate, malate, and oxalate were 0.2124-0.089, 0.3024-0.228, 0.301-4-0.214, 0.014zk0.018 and 0.086＋0.118 pmol.g-% respectively. There were also significant difference in the contents of these acids among four phases of rocky desertification, and their concentrations decreased with the aggravation of rocky desertification. The concentrations of the LMW organic acids were significantly positive correlated each other. Significant positive correlations were also observed among individual LMW organic acids in soil solution, and between them and soil available P, available K, exchange- able Ca, respectively. Furthermore, the concentrations of LMW organic acids were significantly positively corre- lated with inorganic anions （chlorides, nitrates, and sulfates） in Karst topsoil solution. Therefore, the concen- trations of soil LMW organic acids might be one of driving force in the Karst rock desertification process in Guizhou Province.展开更多
基金carried out according to the program of Fundamental Scientific Research of the Russian Federation
文摘The article describes ethylene polymerization reactions with transition metal catalysts based on complexes of CoCl_(2) and FeCl_(2) with an N,N,N-tridentate ligand 2,6-bis[1-(2,6-dimethylphenylimino)ethyl]pyridine. The complexes are converted into polymerization catalysts by reacting them either with polymethylalumoxane (MAO) or with a combination of Al(C2H5)2Cl and Mg(C4H9)2 at an [Al]:[Mg] ratio of ~3. Both MAO-activated complexes readily polymerize ethylene at 35 ℃ with the formation of linear, low molecular weight polymers with a narrow molecular weight distribution. The same complexes, when activated with the Al(C2H5)2Cl-Mg(C4H9)2 combination, form multi-center catalysts and generate polyethylenes with a broad molecular weight distribution.
文摘Soil low-molecular-weight （LMW） organic acids play important roles in the soil-forming process and the cycling of nutrients in Karst regions. In this study, we quantified the contents of LMW organic acids （including lactate, acetate, formate, malate, and oxalate） in soil solution over the Karst region of Guizhou Province, China using ion chromatography. The concentration of total LMW organic acids in topsoil solution ranged from 0.358 to 1.823pmol＇g-1, with an average of 0.912p.mol.gL The mean concentrations of lactate, acetate, formate, malate, and oxalate were 0.2124-0.089, 0.3024-0.228, 0.301-4-0.214, 0.014zk0.018 and 0.086＋0.118 pmol.g-% respectively. There were also significant difference in the contents of these acids among four phases of rocky desertification, and their concentrations decreased with the aggravation of rocky desertification. The concentrations of the LMW organic acids were significantly positive correlated each other. Significant positive correlations were also observed among individual LMW organic acids in soil solution, and between them and soil available P, available K, exchange- able Ca, respectively. Furthermore, the concentrations of LMW organic acids were significantly positively corre- lated with inorganic anions （chlorides, nitrates, and sulfates） in Karst topsoil solution. Therefore, the concen- trations of soil LMW organic acids might be one of driving force in the Karst rock desertification process in Guizhou Province.
