Localization Of Silica Support For Novel And Highly Efficient Titania-modified Phillips Chromium-based Catalysts

Polyolefin materials are widely used in agriculture, industry and people's daily life due to its excellent properties and performance. As it is known, the key for the development of olefin polymerization industry is catalyst technology. However, Phillips chromium-based catalyst, as one of the most important catalysts for the industrial polyolefin production, is completely dependent on imports from overseas, which severely limits the further development of China's polyolefin industry. The technical bottleneck of the Phillips catalyst is the localization of silica support and its surface modification technology. Currently, a domestic home-made silica gel (patent No.01131135.5) is prepared by PetroChina Research Institute of Petrol Chemical Industry and successfully applied to Ziegler-Natta titanium-based polyethylene catalyst. This is the first investigation of the domestic home-made silica and its titania modification for preparation of Phillips catalyst and its application in ethylene polymerization. Compared with catalysts prepared by Davison 955 silica from Grace, the influences of domestic silica gel support and its titania modification on the catalyst structure and morphology, properties and products of ethylene polymerization are investigated to provide a theoretical basis for the realization of localization of Phillips Cr-based polyethylene catalyst. The results showed that the pore diameter of Phillips catalyst prepared by domestic silica was smaller than that of 955 silica gel catalyst, fragments were uneven and activity was lower, but when actived at 700℃, catalysts made from domestic and 955 silica showed similar catalytic polymerization activity. After surface modification by titania, the activity of catalysts made from domestic silica and 955 silica supports both increased, but the increase extent of the former is lower than that of the latter, and the sol-gel method was found to be not suitable for domestic silica titania modification. Meanwhile, compared with polyethylene produced by 955 silica catalyst, molecular weight distribution of polyethylene produced by domestic silica catalyst was narrower.