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Study on Hybrid Ziegler-Natta Catalyst for Ethylene Polymerization

Author: FanLiNa
Tutor: YangYongRong；JiangBinBo
School: Zhejiang University
Course: Chemical Engineering
Keywords: Phase inversion Core-shell structure Composite catalyst Ethylene polymerization Broad molecular weight distribution
CLC: TQ325.12
Type: Master's thesis
Year: 2010
Downloads: 39
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Abstract

Supported Ziegler-Natta olefin polymerization catalyst carrier ships to the inorganic material-based, such as SiO, MgCl2 and zeolite. Compared with inorganic carrier, organic matter carrier can significantly reduce the olefin polymerization product of the inorganic ash content, improve the performance of the polyolefin product, the functional group can also be more easily introduced to effectively control the distribution of the catalytically active center on the carrier, and thus more good regulation of the olefin polymerization process and polymerization of the product morphology. Therefore, inorganic / organic carrier complex catalyst was prepared to become an important direction of the new polyolefin catalysts. Preparation of inorganic / organic composite emulsion polymerization, suspension polymerization and layers of assembly method, but these methods preparation process is cumbersome, it also brings some other polar substances, does not apply to olefin polymerization catalyst Preparation process. The phase inversion membrane materials commonly used in the art is a simple film forming method. This article first examines the basic experimental conditions, then the method introduced composite Ziegler-Natta catalysts prepared with PSA-coated silica gel as a carrier phase inversion prepared silica gel / poly (styrene-co-acrylic acid) (PSA) composite carrier TiCl3 catalyst (SLC-S catalyst), and then to obtain the catalyst composite of the core-shell structure to load MgCl2/TiCl4 complex system, after the polymerization reaction by a broad molecular weight distribution polyethylene products, the results for a single reactor prepared width / bimodal polyethylene has important significance. Thesis was the study of the following aspects: (1) based on phase inversion method formation mechanism preparative silica gel / poly (styrene-co-acrylic acid) (PSA) core-shell microspheres and determine the preparation of composite microspheres experimental conditions; (2) based on the film formation conditions determined by the phase inversion method preparing the composite catalyst of Ziegler-Natta, and ethylene gas phase polymerization and slurry polymerization of of ScS hydrogen content and the thickness of the organic film on the polymerization activity of the catalyst and its polyethylene performance; (3) the catalyst of the catalyst composite shell portion has been improved, and investigated the performance of the catalyst. The specific results of the work are as follows: 1. Proposed Phase Inversion with good dispersion of inorganic / organic composite carrier particles and the effects of the non-solvent evaporation rate, the concentration of the polymer, silica gel particle size and poly (styrene-co - acrylic acid) type and other factors on the surface morphology and particle size of the composite carrier. Non-evaporation of the solvent, the slower the speed, the better the dispersibility of the composite carrier, but the balance between production efficiency and coating effect, the evaporation rate of 1 ml / min; the greater the concentration of the polymer, the rougher the surface of the composite carrier; particle size of the silica gel The larger the surface of the composite carrier fluffy; molecular weight poly (styrene-co-acrylic acid) and functional group content does not influence the morphology and particle size distribution of the composite carrier. In addition, the PSA film coated on the surface of the composite carrier is relatively dense, and compared to Solo silica carrier, its specific surface area, pore volume and the pore size was significantly reduced the use of phase transformation Preparation of a compound that contains both an inorganic carrier and an organic carrier Ziegler -Natta catalyst, the polymerization activity of the catalyst to ethylene gas phase polymerization reaction and the polymerization product performance. The composite catalyst having a higher activity, the activity of up to 3000 g of polyethylene / g of catalyst polymerization pressure (9.0 bar), and the kinetics of the composite catalyst is adjustable. The composite catalyst polymerization activity is higher than the nucleation layer a thickness of 3 microns SLC-S catalyst and having the the belt smooth kinetic curves of the induction period, and a thickness of 1.5 microns, the composite catalyst activity is close to SLC-S catalyst, and having a similar attenuation kinetics curves. Meanwhile, the type of film thickness can be adjusted to a hydrogen transfer performance of the composite catalyst and the resultant molecular weight distribution of the polyethylene to obtain a broad molecular weight distribution polyethylene. Composite catalyst of the Ziegler-Natta polymerization of ethylene slurry effects of different film thickness of catalyst activity and polymerization of ethylene slurry polymerization product performance. The study found that the the composite catalyst slurry polymerization activity was significantly higher than the gas phase polymerization. The kinetic curves of the SLC-S catalyst, and HC-5 catalyst by the fast decay changes in the gas phase polymerization in slurry polymerization smooth curve type HC-20 catalyst smooth kinetic curves becomes slurry slowly decaying plasma polymerization type. Mn and Mw with increasing thickness of the slurry polymerization gradually increases sequentially, and its vapor phase polymerization of the same law, but MWD is gradually narrowed. At the same time, the catalyst slurry polymerization, a bulk density of the polyethylene obtained is slightly lower than the gas phase polymerization. 4 in order to improve the performance of the catalyst, the use of BuMgCl instead of MgCl2 reacting got the series vectors compound catalyst, the main impact of the TiCl4 added in an amount of shell polymerization activity of the catalyst and the molecular weight distribution of the polyethylene. With the the TiCl4 addition amount increases, the activity of the catalyst is increased gradually and almost linearly increasing trend. At the same time, the type of polymerization kinetics gradual transition from the fast decay type slowly decaying type, MWD gradually reduced, bulk density polyethylene polymerization reaction proceeds gradually increased.

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CLC: > Industrial Technology > Chemical Industry > Synthetic resins and plastics industry > Polymer resin and plastic > Polyolefin plastic > Polyethylene
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