Dissolved organic matter （DOM） transforma- tion in sequence batch reactor （SBR） fed with carbon sources of different biodegradability was investigated. During the biologic degradation process, the low mole- cular ...Dissolved organic matter （DOM） transforma- tion in sequence batch reactor （SBR） fed with carbon sources of different biodegradability was investigated. During the biologic degradation process, the low mole- cular weight （MW） fraction （〈 1 kDa） gradually decreased, while the refractory compounds with higher aromaticity were aggregated. Size exclusion chromatogra- phy （SEC） and fluorescence of excitation emission matrices （EEM） demonstrated that more biopolymers （polysaccharides or proteins） and humic-like substances were presented in the extracellular polymeric substance （EPS） extracted from the SBR fed with sodium acetate or glucose, while the EPS from SBR fed with slowly biodegradable dissolved organic carbon （DOC） substrate- starch had relatively less biopolymers. Comparing the EfOM in sewage effluent of three SBRs, the effluent from SBR fed with starch is more aromatic. Organic carbon with MW 〉 1 kDa as well as the hydrophobic fraction in DOM gradually increased with the carbon sources changing from sodium acetate to glucose and starch. The DOC fractiona- tion and the EEM all demonstrated that EfOM from the effluent of the SBR fed with starch contained more fulvic acid-like substances comparing with the SBR fed with sodium acetate and glucose.展开更多
The effect of chemical composition of highly active supported Ziegler-Natta catalysts with controlled morphology on the MWD of PE has been studied.It was shown the variation of transition metal compound in the MgCl_2-...The effect of chemical composition of highly active supported Ziegler-Natta catalysts with controlled morphology on the MWD of PE has been studied.It was shown the variation of transition metal compound in the MgCl_2-supported catalyst affect of MWD of PE produced in broad range:Vanadium-magnesium catalyst(VMC)produce PE with broad and bimodal MWD(M_w/M_n=14-21).MWD of PE,produced over titanium-magnesium catalyst(TMC)is narrow or medium depending on Ti content in the catalyst(M_w/M_n=3.1-4.8).The oxidation ...展开更多
In this work, homopolymerization of propylene for synthesis of different molecular weights polypropylene was done using an isospecific metallocene catalyst by changing the polymerization conditions such as Al/Zr (Alum...In this work, homopolymerization of propylene for synthesis of different molecular weights polypropylene was done using an isospecific metallocene catalyst by changing the polymerization conditions such as Al/Zr (Aluminium/Zirconium) ratio, temperature, pressure and polymerization time. The effects of the polymerization conditions on the molecular weight and other polymer properties have been discussed according to the results obtained. The results indicate that the activity of polymerization increased with increasing the Al/Zr mole ratio and reached a maximum value at a ratio of 2000. In relation to the mole ratio, the molecular weight also followed the same trend. The activity was also seen to increase with increase in temperature. The molecular weight increased with increasing the polymerization time at both 0°C and 25°C, but reduced with increase in time at 40°C. The increase of pressure also increased activity but lowered the molecular weight, indicating β-H elimination to the monomer.展开更多
文摘Dissolved organic matter （DOM） transforma- tion in sequence batch reactor （SBR） fed with carbon sources of different biodegradability was investigated. During the biologic degradation process, the low mole- cular weight （MW） fraction （〈 1 kDa） gradually decreased, while the refractory compounds with higher aromaticity were aggregated. Size exclusion chromatogra- phy （SEC） and fluorescence of excitation emission matrices （EEM） demonstrated that more biopolymers （polysaccharides or proteins） and humic-like substances were presented in the extracellular polymeric substance （EPS） extracted from the SBR fed with sodium acetate or glucose, while the EPS from SBR fed with slowly biodegradable dissolved organic carbon （DOC） substrate- starch had relatively less biopolymers. Comparing the EfOM in sewage effluent of three SBRs, the effluent from SBR fed with starch is more aromatic. Organic carbon with MW 〉 1 kDa as well as the hydrophobic fraction in DOM gradually increased with the carbon sources changing from sodium acetate to glucose and starch. The DOC fractiona- tion and the EEM all demonstrated that EfOM from the effluent of the SBR fed with starch contained more fulvic acid-like substances comparing with the SBR fed with sodium acetate and glucose.
文摘The effect of chemical composition of highly active supported Ziegler-Natta catalysts with controlled morphology on the MWD of PE has been studied.It was shown the variation of transition metal compound in the MgCl_2-supported catalyst affect of MWD of PE produced in broad range:Vanadium-magnesium catalyst(VMC)produce PE with broad and bimodal MWD(M_w/M_n=14-21).MWD of PE,produced over titanium-magnesium catalyst(TMC)is narrow or medium depending on Ti content in the catalyst(M_w/M_n=3.1-4.8).The oxidation ...
文摘In this work, homopolymerization of propylene for synthesis of different molecular weights polypropylene was done using an isospecific metallocene catalyst by changing the polymerization conditions such as Al/Zr (Aluminium/Zirconium) ratio, temperature, pressure and polymerization time. The effects of the polymerization conditions on the molecular weight and other polymer properties have been discussed according to the results obtained. The results indicate that the activity of polymerization increased with increasing the Al/Zr mole ratio and reached a maximum value at a ratio of 2000. In relation to the mole ratio, the molecular weight also followed the same trend. The activity was also seen to increase with increase in temperature. The molecular weight increased with increasing the polymerization time at both 0°C and 25°C, but reduced with increase in time at 40°C. The increase of pressure also increased activity but lowered the molecular weight, indicating β-H elimination to the monomer.
