A PROCESS FOR REMOVING CONTAMINANTS FROM A LIQUID TICL4 PHASE

Abstract: A process for removing one or more contaminants of the formula TiCl₃OR, in which R is an alkyl or aryl group, from a liquid phase comrising TiCl₄, characterized in that the contaminants are reacted with an organic acid halide R'-C Cl, in which R' is an aryl or alkyl group, to precipitate an addition complex of the formula nTiCl₄.R'-C OR, in which n is a number of from 0.3 to 3.0, and the addition complex is separated from the liquid phase.

Description: The present invention is concerned with a process for removing one or more contaminants of the formula TiCl₃OR in which r is an alkyl or aryl group from a liquid phase conprising TiCl₄. Whilst it would in principle be possible to remove these compounds by fractional distillation of the liquid phase, this method is however not adequately energy-efficient and in cases where the contaminants have a boiling point close to that of TiCl₄, this being so for TiCl₃OC₂H₅, the distillation route requires elaborate equipment and is not easy to implement in industrial plants. A simpler method is therefore desirable and the technical problem underlying this invention is to achieve this. The TiCl₄ working-up method of this invention is based on the following principles: 1. The contaminants TiCl₃OR can be converted into TiCl₄ and esters by reacting with an organic acid halide, for example TiCl₃OC₂H₅ (ethoxy titanium trichloride) readily reacts with C₆H₅-COCl (benzoylchloride) to form TiCl₄ and ethylbenzoate. This reaction is known per se. 2. The ester readily react with TiCl₄ to form addition compounds or complexes, this reaction is also known per se. 3. The Applicants have found that the relevant addition complexes have a limited solubility in liquid TiCl₄, particularly at lower temperatures, so that they can be precipitated from the liquid TiCl₄ phase. According, the invention provides a process for removing one or more contaminants of the formulatTiCl₃OR, in which R is an alkyl or aryl group, from a liquid phase comprising TiCl₄, characterized in that the contaminants are reacted with an organic acid halide R'-C O Cl, in which R' is an aryl or alkyl group, to precipitate an addition complex of the formula nTiCl₄.R'-COR, in which n is a number of from 0.3 to 3.0, and the precipitated complex is separated from the liquid phase. Whilst the invention includes the use of a binary liquid phase system comprising TiCl₄ and TiCl₃OR components, it is preferred to employ a liquid phase that in addition contains a liquid halohydrocarbon diluent, provided the presence of this diluent does not bring about a substantial modification of the limited solubility of the envissaged addition complex in the liquid phase. When halohydrocarbons are employed, preferred weight ratios to TiCl₄ vary in the range of from 30:70 to 70:30. Suitable halohydrocarbons are aliphatic halohydrocarbons with up to 12 carbon atoms, e.g. 1,2-dichlorethane, trichloropropane, hexachloroethane, tetrachloromethane, 2-chlorobutane, 1-chloroisooctane, etc. and aromatic halohydrocarbons, e.g. 2,3-dichloronaphthene, 1,2- 1,3- or 1,4-dichlorobenzene, 2-chlorotoluene or monochlorobenzene, the latter being a preferred compound. The organic acid halide can be selected from aromatic and aliphatic acid halides, from the latter group of compounds those in which R' represents an alkyl group with from 1 to 12 carbon atoms, e.g. ethyl, n-propyl, isopropyl, hexyl or cyclohexyl are preferred. Particularly suitable are acid halides in which R' represents substituted or unsubstituted phenyl. Most preferred is benzoychloride. In the complex nTiCl₄.R'-C O OR the preferred values of n are within the range of from 0.75 to 1.30. These values can be produced by adjusting the amount of organic acid halide to be added to the contaminated TiCl₄ comprising a known amount of TiCl₃OR. The concentration of the latter in the liquid phase shall normally be less than 300 g/kg TiCl₄ and more than 15 g/kg TiCl₄. In the most preferred reactions one will employ the acid halide in a stoichiometric amount, thus enabling the reaction: TiCl₃OR + R'-C O Cl → TiCl₄.R-C O OR. Preferred groups OR are alkoxy groups of from 1 to 8 carbon atoms, with ethoxy groups being most preferred. This reaction proceeds rapidly when the temperature of the liquid phase is above 60°C, preferably at least 90°C. At lower temperatures, more time is needed for the required conversion. At the aforesaid elevated temperatures the addition complex is relatively soluble in the liquid phase, however, a rapid precipitation occurs when the liquid phase is cooled to a temperature of less than 15°C. At higher temperatures the precipitation is more slowly and less quantitative. The process of the invention is of particular interest for the preparation of solid catalyst components for the polymerization of 1-alkenes, such as ethylene, propylene, butene-1, octene-1, etc., based upon the halogenation of e.g. magnesiumalkoxy or -aryloxychloride or magnesiumdialkoxide or -diaryloxide with TiCl₄ in the presence of a liquid halohydrocarbon as disclosed in EP-19330. Upon filtering the liquid phase to isolate the solid product of the halogenation reaction one obtains a liquid phase comprising TiCl₄, a halohydrocarbon and a contaminating compound of the formula TiCl₃OR. The process of EP-19330 further prescribes a second step to produce the desired solid catalyst component. This step involves the reaction of the aforesaid solid reaction product with liquid TiCl₄. In that reaction the co-presence of TiCl₃OR contaminants is not desired but when these contaminants are removed with the process of this invention the purified liquid TiCl₄ can very well be used as the reactant for the second step of the process of EP-19330. Accordingly this invention is also concerned with a process for preparing a solid catalyst component for 1-alkene polymerization which comprises: (1) reacting TiCl₄ with a compound of the formula Mg(OR) n Cl₂ -n in which R is an alkyl or aryl group, in the presence of a halohydrocarbon, (2) separating the solid product so obtained from the liquid phase, (3) reacting the liquid phase which is contaminated with a compound of the formula TiCl₃OR with an organic acid halide of the formula R'-CCl, in which R' is an aryl or alkyl group, to preciptate an addition complex of the formula nTiCl₄.R'-COR wherein n is a number of from 0.3 to 3.0, (4) separating the solid addition complex from the liquid phase, (5) slurrying the solid product of step (1) in the liquid phase obtained in step (4) at a temperature of at least 60°C during at least 0.5 hours, followed by (6) separating the solid reaction product from the liquid phase. It is preferred to carry out the first reaction step in the co-presence of an electron donor (Lewis base), preferably an aromatic ester of an aliphatic alcohol, e.g. ethylbenzoate. The liquid phase obtained in step (6) may be recycled into step (1), optionally following purification in line with the method of steps (3) and (4). The latter would be particularly useful if in step (3) an excess of organic acid halide instead of the stoiciometric amount is employed. In polymerizing 1-alkenes, particular propylene or mixtures of propylene and up to 20% mol of ethylene the solid catalyst components may be applied in any manner known per se, preference is given to the method disclosed in EP-19330. The best catalyst systems comprise as co-catalyst a combination of a trialkylaluminium compound and an aromatic ester of an aliphatic alcohol, e.g. one of the compounds referred to in GB-A 1,387,890, preferably p.ethoxyethylbenzoate or p.methoxyethylbenzoate. Instead of using a single trialkylaluminium compound one may also employ such compound in admixture with a dialkylaluminium halide. The invention is illustrated by the following examples: Examples I 135 g of magnesiumethoxychloride and 61 g of ethylbenzoate are stirred in 4.3 kg of a 50:50 vol mixture of TiCl₄ and monochlorobenzene at 100°C during 1.5 hours. 175 g of solid reaction product (A) is removed from the liquid phase to which 183 g of benzoylchloride is added at 95°C. The liquid phase is stirred at 95°C for 10 min, then cooled to 10°C to precipitate 485 g of the solid yellow complex TiCl₄.C₆H₅COOC₂H₅. Subsequent to filtration, the volume ratio of the liquid phase is readjusted to 50:50 by addition of 285 g of TiCl₄ and product A is dispersed in the latter liquid phase. The temperature is increased to 105°C and the dispersion is stirred during 3 hours. Upon filtration 172 g of the solid product (A') are washed with isopentane at 30°C during 1.5 hours. Example II 150 g of magnesiumethoxychloride and 57 g of ethylbenzoat are stirred in 4.5 kg of a 50:50 vol. mixture of TiCl₄ and monochlorobenzene at 105°C during 1.7 hours. 172 g of solid reaction product (B) is removed from the liquid phase to which 370 g of benzoylchloride is added at 90°C. The liquid phase is stirred at 90°C for 20 min., then cooled to 15°C to precipitate 970 g of the solid yellow complex TiCl₄.C₆H₅COOC₂H₅. Subsequent to filtration, the volume ratio of the liquid phase is readjusted to 50:50 by addition of 560 g of TiCl₄ and product B is dispersed in the latter liquid phase. The temperature is increased to 100°C and the dispersion is stirred during 2.7 hours. Upon filtration 169 g of the solid product (B') are washed with isopentane at 25°C during 1.7 hours. Example III Solids A' and B' were tested as solid catalyst components for liquid propylene polymerization using the following standard conditions:

Claims: 1. A process for removing one or more contaminants of the formula TiCl₃OR, in which R is an alkyl or aryl group, from a liquid phase comprising TiCl₄, characterized in that the contaminants are reacted with an organic acid halide R'-CCl, in which R' is an aryl or alkyl group, to precipitate an addition complex of the formula nTiCl₄.R'-COR, in which n is a number of from 0.3 to 3.0, and the addition complex is separated from the liquid phase. 2. A process as claimed in claim 1 in which the liquid phase comprises TiCl₄ and a halohydrocarbon. 3. A process as claimed in claim 2 in which the liquid phase comprises TiCl₄ and halocarbon in a weight ratio of from 30:70 to 70:30. 4. A process as claimed in claim 2 or 3 in which the halohydrocarbon is monochlorobenzene. 5. A process as claimed in any one of claims 1 to 4, in which subsequent to reaction with organic acid halide, the liquid phase is cooled to a temperature of less than 15°C. 6. A process as claimed in any one of claims 1 to 5 in which the group OR represents an alkoxy group of from 1 to 8 carbon atoms. 7. A process as claimed in claim 6 in which the group OR is an enthoxy group. 8. A process as claimed in any one of claims 1 to 7, in which R' is a substituted or unsubstituted phenylgroup. 9. A process for preparing a solid catalyst component for 1-alkene polymerization which comprises: (1) reacting TiCl₄ with a compound of the formula Mg(OR)nCl₂-n in which R is an alkyl or aryl group in the presence of a halohydrocarbon, (2) separating the solid product so obtained from the liquid phase, (3) reacting the liquid phase which is contaminated with a compound of the formula TiCl₃OR with an organic acid halide of the formula R'-CCl, wherein R' is an aryl or alkyl group, to precipitate an addition complex of the formula nTiCl₄.R'-COR, wherein n is a number of from 0.3 to 3.0, (4) separating the solid addition complex from the liquid phase, (5) slurrying the solid product of step (1) in the liquid phase obtained in step (4) at a temperature of at least 60°C during at least 0.5 hours, following by (6) separating the solid reaction product from the liquid phase. 10. A process as claimed in claim 9 in which step (1) is carried out in the presence of an electron donor. 11. A process as claimed in claim 10, in which the electron donor is an aromatic ester of an aliphatic alcohol. 12. A process for polymerizing a 1-alkene in the pressence of a catalyst system comprising (a) the solid catalyst component produced with the process of any one of claims 9 to 11, (b) a trialkylaluminium compound or a mixture of the latter compound and a dialkylaluminiumhalide and (c) an aromatic ester of an aliphatic alcohol.

Inventors: BILHOU, JEAN LOUIS, GOODALL, BRIAN LESLIE
Applicants: SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ B.V.
Application year: 1986
Main classification: C08F4
IPC codes: C08F4, C01G23, C08F10