Catalyst used for olefin polymerization and preparation method thereof

Abstract

The invention relates to a catalyst used for olefin polymerization and a preparation method thereof. The preparation method is as follows: in a reactor, under the protection of nitrogen, adding an organic solvent and a titanium compound, cooling to-30 to-10 DEG C, adding a carrier, maintaining at-30 to-10 DEG C, and stirring for 30-40min; slowly heating to 100 to 120 DEG C, in the heating process, adding an electron donor compound, reacting at 100-120 DEG C for 30-40min, filtering a liquid, again adding the titanium compound, heating to 110 to 130 DEG C, maintaining at 110 to 130 DEG C for 30-40min, filtering the liquid, washing an obtained solid, and drying under vacuum to obtain a target product. In a magnesium halide alcohol adduct formation process, a forming agent and a particle form control agent are added, the particle size distribution of the obtained carrier is more concentrated, the carrier is used for preparing the catalyst, activity and hydrogen sensitivity of the catalyst can be improved when the carrier is used for olefin polymerization especially for propylene polymerization, the bulk density of an obtained polymerization product is moderate, and the polymerization product is basically free of abnormity materials.

Description

technical field [0001] The invention belongs to the field of catalysts, in particular to a catalyst for olefin polymerization and a preparation method thereof. Background technique [0002] At present, Ziegler-Natta catalysts for olefin polymerization are basically prepared by loading titanium halides on supports. The carrier commonly used in the preparation of Ziegler-Natta catalysts is magnesium chloride alcoholate, and its overall performance is superior to catalysts prepared by other carriers. The preparation of carrier magnesium chloride alcoholate generally adopts methods such as spray drying, spray cooling, high-pressure extrusion, high-speed stirring, emulsification molding, and high-gravity rotating bed. However, in the process of catalyzing the polymerization of olefins, the catalyst prepared by the carrier obtained by this method is prone to breakage of polymer particles, resulting in excessive fine powder. Although people try to add an electron donor compound i...

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Problems solved by technology

However, the composite spherical carrier is easy to stick during the preparation process, and it is difficult to form spherical particles with suitable particle size.

[0003] In the prior art, the methods for preparing catalysts for olefin polymerization mainly include: ① first prepare the carrier by reacting the magnesium halide alcoholate with ethylene oxide compounds, and then directly add the magnesium halide alcoholate to the In the reactor of ethylene oxide compounds, the catalyst carrier prepared by this method has the disadvantages of unstable preparation process, easy carrier adhesion, and poor carrier molding effect.

② Use epoxide and tributyl phosphate compounds to dissolve magnesium chloride to form a uniform solution, and then use titanium tetrachloride to precipitate the carrier and carry out titanium loading. The reaction products are very complicated, and the by-products produced are difficult to handle. In the process of titanium oxide precipitation, some precipitation aids are also used, which makes the reaction by-products more complicated.

However, the preparation of the carrier needs to prepare the corresponding magnesium halide adduct first, and then contact the alkylene oxide compound to obtain it. The steps are cumbersome and the reaction controllability is poor.

④ It is also reported that alkoxymagnesium carrier is used to support titanium metal compound for catalyst preparation. The alkoxymagnesium carrier is prepared by reacting metal magnesium and ethanol, but there are disadvantages such as low bulk density of the obtained polymer.

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