PL176036B1 - Platinum catalyst and method of obtaining same - Google Patents

Abstract

1. Platinum catalyst in the form of hexachloroplatinic acid dissolved in cyclohexanone followed by a silane-modified modifier is a trialkoxysilane of the general formula (RO) 3SiH in which R is a methyl group or ethyl, while the catalyst contains 2.5x10.5 moles of platinum per 1 cm3 of cyclohexanone mixture and trialkoxysilane. 2. A method for producing a platinum catalyst in which hexachloroplatinic acid it is taken up in cyclohexanone and then modified with a silane characterized in that a trialkoxysilane of the general formula (ROfSiH, where R is a methyl or ethyl group, and the process is carried out at 293 ° C 393 K, in air, under normal pressure.

Description

The subject of the invention is a new platinum catalyst and a method of its preparation. The catalyst is used in the hydrosilylation reaction of the carbon-carbon double bond in organic bonds.

Hexachloroplatinic acid is the most widely used catalyst for the hydrosilylation reaction ["Comprehensive Handbook on Hydrosilylation" (B. Marciniec, ed.), Pergamon Press, Oxford, 1992]. Most often it is used after reconstitution in isopropanol or in higher aliphatic and aromatic alcohols (JL Speier, Adv. Organomet. Chem. 17. 407, 1979), in compounds containing carbonyl linkages, e.g. in cyclohexanone (French Patent No. 1385096), in tetrahydrofuran (European Patent No. 260103) and a number of other organic derivatives.

For a number of reaction systems, hexachloroplatinic acid, dissolved in an organic solvent, shows too low selectivity and catalytic efficiency. Hence, extensive catalytic research is conducted to increase the efficiency of catalysts based on hexachloroplatinic acid. These studies usually consist of searching for new solvents and activators of this acid [V. Vybiral, P. Svoboda,

J. Hetflejs, Coll. Czech. Chem. Comm. 44,866 (1979), Polish patent specification No. 143118]. From Polish patent specification No. 145,670, in which hexachloroplatinic acid, after being dissolved in cyclohexanone, is dissolved in vinyltrialkoxy silane, which enhances the stabilization of the formed platinum (O) complex and protects against loss of inactive platinum.

The present invention is a platinum catalyst in the form of hexachloroplatinic acid solubilized in cyclohexanone, and then modified in accordance with the invention, a trialkoxysilane of the general formula (RO ^ SiH, wherein R is methyl or ethyl containing 2.5 x 10 ^-5 mol of platinum in 1 cm3 mixtures of cyclohexanone and trialkoxysilane.

The method of obtaining the catalyst consists in reacting hydrated hexachloroplatinic acid by dissolving it in an excess of cyclohexanone and then reacting the platinum complex thus obtained, dissolved in cyclohexanone, according to the invention, by dissolving it in excess of a trialkoxysilane of the general formula (RO ^ SiH, wherein R is as defined above The entire catalyst preparation process is carried out at a temperature of 293 to 393 K, in an air atmosphere, under normal pressure.

A trialkoxysilane of the general formula (RO) _; SiH, in which R is as defined above, used in the catalyst preparation process significantly modifies the platinum complex obtained by dissolving hexachloroplatinic acid in cyclohexanone. The process of dechlorination of the starting platinum compound is accompanied by its reduction to platinum complexes of low oxidation states, stabilized by cyclohexanone condensation products. Trialkoxysilane in the H ₂ PtCl _{6 system} - cyclohexanone forms a catalytically active platinum colloid. Colloidal platinum is a real, very effective catalytic agent in the presented catalytic system. Thus obtained in the present invention a new catalyst system allows taking a much lower platinum content in the system (2.5 x 10 ^-5 mol / '1 cm ^{3 of} a mixture of cyclohexanone and trialkoxysilane) for obtaining the reaction product wydajnościąi catalyst with high selectivity. This effect is particularly important for both technical and economic reasons, because it allows the use of smaller amounts of catalyst to produce larger amounts of product, and the separation of platinum from the deactivated catalyst based on hexachloroplatinic acid is extremely onerous and often unprofitable.

The new platinum catalyst obtained by the method according to the invention significantly exceeds its efficiency, for example in the hydrosilylation reaction with a trialkoxysilane or trichlorosilane of the carbon-carbon double bond, catalysts in the form of hexachloroplatinic acid dissolved in cyclohexanone or additionally in vinyltrialkoxysilane.

The efficiency of the hydrosilylation reaction of the carbon-carbon double bond with trialkoxysilanes obtained thanks to its use also often exceeds the yields obtained with the use of other platinum catalysts.

The following are examples of the preparation of the catalyst according to the invention as well as an example of its use in the hydrosilylation reaction.

Example 1 1.167 cm 3 of hydrated hexachloroplatinic acid (containing 100 mg Pt) and 10 cm 3 of cyclohexanone were heated at 373 K in an oil bath for 1.5 hours at atmospheric pressure. After cooling, the mixture was dried over anhydrous sodium sulfate for 24 hours. The liquid was decanted, the precipitate was washed with cyclohexanone, combined and made up with cyclohexanone to a volume of 10 cm3. A platinum-cyclohexanone complex dissolved in cyclohexanone at a concentration of 10 mg Pt (5 · 10 * 5 mol) in 1 cm3 of the solution was obtained. Then, in a flask of 100 cm3 equipped with a reflux condenser, placed 10 cm ^{3 of} the thus obtained complex and 4 cm 3 (0.02 mole) of triethoxysilane. The contents of the flask were stirred with a magnetic stirrer at the temperature of 293 K for 24 hours and then made up with cyclohexanone to the volume of 20 cm ³ . A platinum catalyst with a concentration of 5 mg Pt (2.5 × 10.5 mol) in 1 cm3 of the solvent mixture was obtained.

Example II. Proceeding as in Example 1, 0.02 mol of trimethoxysilane was used in place of the triethoxysilane. A platinum catalyst with a concentration of 5 mg Pt (2.5 · 10-mol) in 1 cm ^{3 of} the solvent mixture was obtained.

Example III. The procedure was analogous to that in Example 1, except that the dissolution of the platinum complex in triethoxysilane was carried out at the temperature of 363 K for 2 hours. The platinum catalyst was obtained with a concentration of 5 mg Pt (2.5 × 10.5 mol) in 1 cm ^{3 of} the solvent mixture.

Example IV. In a steel autoclave with a capacity of 100 cm ^{3 of} 53 cm3 provided a mixture containing 38 cm3 triethoxysilane (33 g, 0.2 mol), 15 cm3 of allylamine (11.4 g, 0.2 mol) and 4 cm ³ (10 ^"4 mole Pt ) of the catalyst prepared as in Example I. The mixture was heated to 373 K and kept at this temperature for 6 hours. The product was obtained in a yield of 74%, determined by chromatography, with a ratio of 3-aminopropyltriethoxysilane to 2-aminopropyltriethoxysilane of 5.0.

ExampleV. Katalizatorjak prepared in Example I. Next, three-necked flask with a capacity of 250 cm3, provided with a reflux condenser, a thermometer and a dropping funnel, was placed 0.4 cm ^{3 of} catalyst solution (2 mg Pt / LO mol) and added dropwise an equimolar mixture of trichlorosilane ( 133.5 g / L mol) and allyl chloride (76.4 g / L mol). The reaction mixture was kept at room temperature for a period of 4 hours. The 3-chloropropyltrichlorosilane was obtained with a yield of 76% determined by chromatography.

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Claims (2)

Patent claims 1. A platinum catalyst in the form of hexachloroplatinic acid dissolved in cyclohexanone and then modified with silane, characterized in that the modifier is a trialkoxysilane of the general formula (RO) ₃ SiH, in which R is a methyl or ethyl group, the catalyst containing 2.5 x 10 ' ⁵ moles of platinum per 1 cm ^{3 of a} mixture of cyclohexanone and trialkoxysilane. 2. A process for the preparation of a platinum catalyst in which hexachloroplatinic acid is taken up in cyclohexanone and then modified with a silane, characterized in that a trialkoxysilane of general formula (RO) ₃ SiH is used as the modifier, in which R is a methyl or ethyl group, where the process is carried out at a temperature of 293 to 393 K, in an atmosphere of air, under normal pressure.