Catalyst component for ethylene polymerization, catalyst and preparation method thereof

Abstract

The invention discloses a catalyst component for ethylene polymerization, a preparation method of the catalyst component and a catalyst thereof. The catalyst component is obtained by treating a magnesium / titanium containing solid with at least one silicon compound, wherein the magnesium / titanium containing solid is prepared by dissolving the magnesium compound in an organic epoxy compound containing In the solvent system of the organic phosphorus compound, after forming a homogeneous solution, it co-precipitates with the titanium compound and one or several organic ester compounds in the presence of a composite precipitation aid to obtain a magnesium / titanium-containing solid. This kind of catalyst component has relatively narrow particle distribution and small average particle size. The catalyst has high activity, high sensitivity to hydrogen adjustment and can obtain polymer with low fine powder content. It is suitable for slurry polymerization or gas phase of ethylene Polymerization, especially suitable for gas phase fluidized bed polymerization process of ethylene with catalyst fed in slurry form.

Description

technical field [0001] The invention belongs to the field of olefin polymerization, and in particular relates to a catalyst component for ethylene homopolymerization and copolymerization, a preparation method of the catalyst component, a corresponding catalyst and its application in ethylene polymerization. Background technique [0002] In the polymerization of olefins, especially in the polymerization of ethylene or the copolymerization of ethylene and α-olefins, catalyst components based on magnesium, titanium, halogen and electron donors are mostly used. When this type of catalyst is used in a gas-phase fluidized bed polymerization process, in order to ensure that the shape and particle size distribution of the catalyst particles are more suitable for fluidized state operation, the above-mentioned catalyst components are usually supported on a carrier such as silica gel. For example: the catalyst disclosed in US4,302,565, US4,379,759 and CN1064870A for gas-phase fluidized...

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Problems solved by technology

[0003] In the above-mentioned published patents, in order to make the catalyst applicable to the gas-phase fluidized bed polymerization process, there are relatively strict requirements on the average particle size, surface area, and pore size of the carrier silica used, and the price of this carrier material It is more expensive, and at the same time, the silica carrier needs to be strictly activated before use, all of which lead to an increase in the production cost of the catalyst; and the active components of the catalyst are loaded on the carrier by impregnation and other methods, due to the limitation of the amount of titanium and other reasons, the catalyst efficiency is not satisfactory

In addition, the amount of fine powder in the polyethylene powder produced by using this catalyst is relatively large, usually the particles below 150 microns account for about 15wt% of the total powder, which is very undesirable in industrial production

[0004] The catalyst production method mentioned in Chinese patent CN1085915A, although overcomes some shortcomings mentioned above, but needs to use metal magnesium as reducing agent in the production process, and still needs to use a large amount of silica carrier materials, finally will get Catalyst particle products also need to be spray-dried, which requires large equipment investment and complicated operation, so that the overall production cost is still relatively high

[0005] Chinese patent CN85100997 discloses a catalyst for olefin polymerization, which is formed by dissolving magnesium halide in organic epoxy compounds and organic phosphorus compounds to form a uniform solution, and then with at least one precipitation aid and a polycarboxylic acid ester electron donor and transition metal titanium halides and their derivatives. When the catalyst is used for propylene polymerization, it shows high polymerization activity and good stereospecificity, but when it is used for ethylene polymerization, the activity is low, and The particle size distribution of the polymer is broad and the hydrogen tuning sensitivity of the catalyst is not good

However, the particle size of the catalyst prepared by this process is generally small, and the fine powder content in the polymer obtained by ethylene polymerization using this catalyst is relatively high, but this catalyst is not suitable for the ethylene polymerization of the gas phase fluidized bed polymerization process.

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