The nonmetallocene catalyst, also called as the post-metallocene catalyst, was discovered in middle and late 1990's, whose central atom involves nearly all of the transition metal elements. The nonmetallocene catalyst is comparative to, or exceeds, the metallocene catalyst in some aspects of the performance, and has been classified as the fourth generation catalyst for olefin polymerization, following the Ziegler catalyst, the Ziegler-Natta catalyst and the metallocene catalyst. Polyolefin products produced with such catalysts exhibit favorable properties and boast low production cost. The coordination atom of the nonmetallocene catalyst comprises oxygen, nitrogen, sulfur and phosphor, without containing a cyclopentadiene group or a derivative thereof (for example, an indene group or a fluorene group). The nonmetallocene catalyst is characterized in that its central atom shows comparatively strong electrophilicity and has a cis alkyl metal type or a metal halide type central structure, which facilitates olefin insertion and σ-bond transfer. Therefore, the central atom is easily subject to alkylation, and therefore facilitates formation of a cationic active center. The thus formed complex has a restricted geometrical configuration, and is stereoselective, electronegative and chiral adjustable. Further, the formed metal-carbon bond is easy to be polarized, which further facilitates homopolymerization and copolymerization of an olefin. For these reasons, it is possible to obtain an olefin polymer having a comparatively high molecular weight, even under a comparatively high polymerization temperature.
However, it is known that in the olefin polymerization, the homogeneous phase catalyst suffers from such problems as short service life, fouling, high consumption of methyl aluminoxane, and undesirably low or high molecular weight in the polymer product, and thus only finds limited use in the solution polymerization process or the high-pressure polymerization process, which hinders its wider application in industry.
Chinese patent Nos. 01126323.7, 02151294.9 and 02110844.7, and WO03/010207 disclose a catalyst or catalyst system finding a broad application in olefin polymerization. However, the catalyst or catalyst system should be accompanied by a comparatively high amount of co-catalysts, to achieve an acceptable olefin polymerization activity. Further, the catalyst or catalyst system suffers from such problems as short service life and fouling.
It is normal to support the nonmetallocene catalyst by a certain process, so as to improve the performance of the catalyst in the polymerization and the particle morphology of the polymer products. This is reflected by, moderate reduction of the initial activity of the catalyst, elongation of the serve life of the catalyst, alleviation or elimination of caking or flash reaction during the polymerization, improvement of the polymer morphology, and increase of the apparent density of the polymer, thus extending its use to other polymerization processes, for example, the gas phase polymerization or the slurry polymerization.
Aiming at the catalysts of the Chinese patent Nos. 01126323.7, 02151294.9 and 02110844.7, and WO03/010207, Chinese patent application Laid-Open Nos. CN1539855A, CN1539856A, CN1789291A, CN1789292A and CN1789290A, and WO2006/063501, and Chinese application patent No. 200510119401.x provide several ways to support same catalyst on a carrier so as to obtain a supported nonmetallocene catalyst. However, each of these applications relates to the technology of supporting a transition metal-containing nonmetallocene organic metallic compound on a treated carrier. Further, the bonding between the nonmetallocene catalyst and the porous carrier by reaction is subjected to some restriction, and in the result supported nonmetallocene catalyst, the nonmetallocene organic compound exists mainly in a physical adsorption state, which is unfavorable for control of the polymer particle morphology and performance of the nonmetallocene catalyst.
Most of the prior art olefin polymerization catalysts are metallocene catalyst-based, for example, those according to U.S. Pat. No. 4,808,561 and U.S. Pat. No. 5,240,894, Chinese patent application Laid-Open Nos. CN1344749A, CN1126480A, CN1307594A, CN1103069A, and CN1363537A, and U.S. Pat. No. 6,444,604, EP 0685494, U.S. Pat. No. 4,871,705 and EP0206794, and Chinese patent No. 94101358.8. Again, all of these applications relate to the technology of supporting a transition metal-containing metallocene catalyst on a treated carrier.
EP708116 discloses a process comprising contacting gasified ZrCl4 with a carrier at a temperature ranging from 160° C. to 450° C. to support thereon, then reacting the supported ZrCl4 with the Li-salt of a ligand to obtain a supported metallocene catalyst, which is finally used for olefin polymerization in combination with a co-catalyst. The process is rather undesirable for industrial production since the supporting procedure should be conducted at a high reaction temperature and under a high vacuum.
Chinese application patent No. ZL01131136.3 discloses a process for producing a supported metallocene catalyst, which comprises mixing a carrier with a Group IVB transition metal halide in a solvent under the normal pressure, then directly reacting with the cation ion of a ligand, so as to integrate synthesis and supporting of the metallocene catalyst in one step. However, according to this process, the transition metal and the ligand is used at a molar ratio of 1:1, and a proton acceptor (for example, butyl lithium) is required. Further, the ligand to be used is a bridged or non-bridged metallocene ligand containing a cyclopentadiene group.
Chinese patent No. ZL200510080210.7 discloses a process for in-situ producing a supported vanadium-based nonmetallocene catalyst for olefin polymerization and use thereof, which comprises reacting dialkyl magnesium with acyl naphthol or a β-dione to form magnesium acyl naphthol or magnesium β-dione compound, then reacting with a chloride of vanadium (IV), so as to form the carrier and the active catalytic component simultaneously.
Chinese patent Nos. 200710162667.1 and 200710162676.0 and PCT/CN2008/001739 disclose a supported nonmetallocene catalyst and preparation thereof, wherein a magnesium compound (for example magnesium halide, alkyl magnesium, alkoxyl magnesium, alkyl alkoxyl magnesium), a modified magnesium compound by chemically treating (by for example alkyl aluminum, alkoxy aluminum) the magnesium compound, or a modified magnesium compound by precipitating a magnesium compound-tetrahydrofuran-alcohol system is used as the carrier, and contacts with a nonmetallocene ligand and an active metal compound in different orders one after another to perform an in-situ supporting process. As the solid starting material, the magnesium compound as the carrier herein has not been subjected to the step of forming a magnesium compound solution, i.e. re-crystallization. For this reason, the magnesium compound is significantly subject to the starting material and its influence to the resultant nonmetallocene catalyst is unpredictable.
The catalyst prepared using anhydrous magnesium chloride as a carrier exhibits a high catalytic activity in the olefin polymerization, but this kind of catalyst is very brittle, prone to crush in the polymerization reactor, resulting in a poor polymer morphology. The catalyst supported on silica has an excellent flowability, useful to a fluidized-bed gas-phase polymerization, but the silica-supported metallocene and nonmetallocene catalyst shows a lowered catalytic activity. If magnesium chloride could be appropriately combined with silica, a catalyst with high catalytic activity, controllable granule size and good abrasion resistance may be obtained.
Chinese patent No. 200610026765.8 discloses a single site Zeigler-Natta catalyst for olefin polymerization. In this catalyst, a coordination group-containing salicylaldehyde or substituted salicylaldehyde derivative is used as the electron donor. The catalyst is produced by introducing a pre-treated carrier (for example, silica), a metallic compound (for example, TiCl4) and the electron donor into a magnesium compound (for example, MgCl2)/tetrahydrofuran solution and then post-treating the resultant.
Chinese patent No. 200610026766.2 is similar to this patent, and relates to an organic compound containing a hetero atom and use thereof for producing a Zeigler-Natta catalyst.
Chinese patent Nos. 200710162677.5, 200710162672.2 and 200710162675.6 and PCT/CN2008/001738 disclose a supported nonmetallocene catalyst and preparation thereof, wherein a nonmetallocene ligand is supported onto a composite carrier by an in-situ process comprising preparing the composite carrier in different manners and contacting same with a nonmetallocene ligand and an active metal compound in different orders one after another so as to conduct the in-situ process.
As can be seen from aforesaid, the prior art supported nonmetallocene catalyst suffers from such problems as a complicate supporting process, which necessitates multiple steps to treat the carrier, the carrier either being subject to the treatment by a compound containing a catalytically active metal and then supporting a nonmetallocene ligand, or supporting a nonmetallocene ligand and then being subject to the treatment by the compound containing a catalytically active metal. Further, the nonmetallocene ligand is formed and supported onto the treated carrier in separate steps and therefore it is difficult to adjust the catalyst components and the contents thereof, and deviation between different batches in product quality occurs.
Further, the prior art supported nonmetallocene catalyst generally suffers from other problems as, if silica or a composite containing silica is used as the carrier for a nonmetallocene catalyst, this will be beneficial to the particle morphology of the resultant polymer, but silica suitable for this supporting purpose is rather expensive in cost, and has to be thermally activated or chemically activated before use, which necessitates complicate processing. The magnesium compound is characterized by a low cost if used as the carrier for a catalyst. Further, there is strong inter-reaction between the magnesium compound and the active metals in a nonmetallocene ligand and may easily lead to a supported nonmetallocene catalyst having a higher activity.
Therefore, there still exists a need for a supported nonmetallocene catalyst, which can be produced in a simple way and in an industrial scale, free of the problems associated with the prior art supported nonmetallocene catalyst.