Research On Spherical Ziegler-natta Catalyst For Propylene Polymerization

The development of polyolefin industry is one of the important indicators to measure the development of a national petrochemical industry,but the key of polyolefin technology is the catalyst.The improvement of the polyolefin resin's performance is very closely related to the optimization of the catalyst.Z-N catalyst has been continuously improved since it appeared,and it has the advantages of simple preparation method,low sensitivity to impurities and low cost.Therefore,Z-N catalyst has been widely used in industrial production.In this paper,the system is alkoxymagnesium and isooctanol,adding acid chloride,adding TiCl4 after generating the internal electron donor,adding a certain amount of surfactant to prepare spherical polypropylene Z-N catalyst.In the process of synthesizing spherical catalyst,the effects of magnesium species,fatty alcohol species and acid chloride species on the morphology and particle size distribution of the catalyst and the effects of different isooctanol dosage on the content of catalyst and the content of ester have been studied.The optimum condition for the preparation of spherical Z-N catalyst has been established.Under the adjustment of the particle size distribution of the catalyst,the content of the catalyst and the content of the ester while maintaining the spherical degree,the spherical polypropylene Z-N catalyst has been prepared.Under the condition of MgCl2 as raw material to prepare traditional polypropylene catalyst,synthesis structure of catalyst and the main reaction equation are further understood through the mechanism analysis of titanium loading of catalyst.It is mainly a complex formation of TiCl4,MgCl2 and internal electron donor complex structure,and the structure of the catalyst was preliminarily deduced by infrared spectroscopy and literature reference.In the preparation of traditional catalyst,it was proved that n-decane only acts as an inert diluent.The addition of n-decane is mainly to reduce the viscosity of alkoxymagnesium/isooctanol system and realize the recovery of n-decane and reduce the cost of the catalyst to achieve energy-saving emission reduction.After confirming the optimum synthesis conditions of the catalyst,the amplification experiment was carried out to determine the repeatability and stability of the synthesized catalyst.The EC catalyst has a better sphericity and distribution of particle size compared with the traditional catalyst.The polypropylene powder prepared by the two catalysts has sieved,the polypropylene powder particle size of EC catalyst prepared is more concentrated.EC catalyst catalyzes the polymerization of propylene with higher activity than traditional catalyst,and has more sensitive hydrogen performance.At different polymerization temperature,H2 dosage,Al/Ti molar,the polymer isometric index is the same.The polymer isotactic index of the two catalysts is basically the same,and the change trend of the melting point of the polymer is the same when the polymerization temperature,H2 dosage and Al/Ti molar ratio are changed.By contrast,the polymerization performance of self-made EC catalyst in the polymerization of propylene polymerization process is better than the traditional catalyst.