综合报道了新型乙烯气相聚合MG型催化剂的制备及其聚合反应性能。研究了采用浸渍反应法制备含TiCl_4/MgCl_2/ZnCl_2/SiO_2/醇/Al(i-Bu)_3的MG-4型高效催化剂。在压力1.0MPa下,乙烯聚合催化效率高达445～884 kg PE/g Ti,制得了表观密度≥...综合报道了新型乙烯气相聚合MG型催化剂的制备及其聚合反应性能。研究了采用浸渍反应法制备含TiCl_4/MgCl_2/ZnCl_2/SiO_2/醇/Al(i-Bu)_3的MG-4型高效催化剂。在压力1.0MPa下,乙烯聚合催化效率高达445～884 kg PE/g Ti,制得了表观密度≥0.37 g/cm^3、重均颗粒分布(20～200目)≥97.7％、颗粒状态良好的聚乙烯。用DSC、SEM、WAXD对聚合产物进行了表征。发现制得了双峰分布的聚乙烯。这可归因于催化剂中锌化合物存在而生成多种活性中心。展开更多
Obvious resonance peak will be generated when parallel photovoltaic grid-connected inverters are connected to the weak grid with high grid impedance, which seriously affects the stability of grid-connected operation o...Obvious resonance peak will be generated when parallel photovoltaic grid-connected inverters are connected to the weak grid with high grid impedance, which seriously affects the stability of grid-connected operation of the photovoltaic system. To overcome the problems mentioned above, the mathematical model of the parallel photovoltaic inverters is established. Several factors including the impact of the reference current of the grid-connected inverter, the grid voltage interference and the current disturbance between the photovoltaic inverters in parallel with the grid-connected inverters are analyzed. The grid impedance and the LCL filter of the photovoltaic inverter system are found to be the key elements which lead to existence of resonance peak. This paper presents the branch voltage and current double feedback suppression method under the premise of not changing the topological structure of the photovoltaic inverter, which effectively handles the resonance peak, weakens the harmonic content of the grid current of the photovoltaic grid-connected inverter and the voltage at the point of common coupling, and improves the stability of the parallel operation of the photovoltaic grid-connected inverters in weak grid. At last, the simulation model is established to verify the reliability of this suppression method.展开更多
文摘综合报道了新型乙烯气相聚合MG型催化剂的制备及其聚合反应性能。研究了采用浸渍反应法制备含TiCl_4/MgCl_2/ZnCl_2/SiO_2/醇/Al(i-Bu)_3的MG-4型高效催化剂。在压力1.0MPa下,乙烯聚合催化效率高达445～884 kg PE/g Ti,制得了表观密度≥0.37 g/cm^3、重均颗粒分布(20～200目)≥97.7％、颗粒状态良好的聚乙烯。用DSC、SEM、WAXD对聚合产物进行了表征。发现制得了双峰分布的聚乙烯。这可归因于催化剂中锌化合物存在而生成多种活性中心。
基金supported by National Natural Science Foundation of China (No. 61573303)Natural Science Foundation of Hebei Province (No. E2016203092)
文摘Obvious resonance peak will be generated when parallel photovoltaic grid-connected inverters are connected to the weak grid with high grid impedance, which seriously affects the stability of grid-connected operation of the photovoltaic system. To overcome the problems mentioned above, the mathematical model of the parallel photovoltaic inverters is established. Several factors including the impact of the reference current of the grid-connected inverter, the grid voltage interference and the current disturbance between the photovoltaic inverters in parallel with the grid-connected inverters are analyzed. The grid impedance and the LCL filter of the photovoltaic inverter system are found to be the key elements which lead to existence of resonance peak. This paper presents the branch voltage and current double feedback suppression method under the premise of not changing the topological structure of the photovoltaic inverter, which effectively handles the resonance peak, weakens the harmonic content of the grid current of the photovoltaic grid-connected inverter and the voltage at the point of common coupling, and improves the stability of the parallel operation of the photovoltaic grid-connected inverters in weak grid. At last, the simulation model is established to verify the reliability of this suppression method.
