PROCESS FOR PREPARING A CATALYST USEFUL IN THE DIMERIZATION OF BUTADIENE

Abstract: Catalysts suitable or the dimerization of a diolefin, e.g. butadiene to 4-vinylcyclohexene, are prepared by reacting (1) iron chloride and sodium nitrite or alternatively (2) iron nitrosyl chloride with (3) carbon monoxide in an organic solvent in the presence of a readily oxidizable metal, e.g. tin. The catalyst solution is filtered prior to use to remove particulate matter such as unreacted tin. While the reaction employing iron chloride and sodium nitrite is preferred, the catalyst produced by either method contains a minimum of reducing agent and by-products. It can be isolated and stored in the absence of the butadiene monomer while retaining its stability and activity.

Description: The complex, iron nitrosyl carbonyl [Fe(NO)₂(CO)₂], is known to dimerize butadiene to produce vinyl cyclohexene (VCH). It is believed that the catalytic activity is due to the Fe(NO)₂ fragment. The methods known to prepare this complex require the reduction of [Fe(NO)₂Cl]₂ or the reaction of nitric oxide (NO) on a mixture of iron and FeCl₃ in an electrolytic cell and in the presence of butadiene. The iron nitrosyl catalyst is believed to be produced in situ and used therein to obtain the dimerization. Reference to these methods is found in U. S. Patent 4,238,301. Another patent, U. S. 4,234,454, discloses the preparation of various metal nitrosyl catalytic solutions by employing the combination of manganese, zinc or tin together with iron, cobalt or nickel nitrosyl halides to produce the respective metal nitrosyls in a system for dimerizing various conjugated dienes. An earlier patent, U. S. 3,510,533, discloses the dimerization of conjugated dienes with π-allyldinitrosyliron complexes and a method for their preparation. Several methods are given involving the reduction of a µ,µ′ -dihalotetranitrosyldiiron. The methods of reduction of metal nitrosyl compounds known to the art have numerous disadvantages. Some of these are: (1) the reduction of the metal nitrosyl compound is required to be in the presence of the butadiene, (2) many of the reducing agents themselves will polymerize the butadiene, (3) contaminants are introduced by the reducing agents and (4) catalyst solutions cannot be stored and expected to retain their activity. The dimerized products of the process of the invention may be useful in themselves or as intermediates to other products. Thus, for example, 4-VCH can be (1) chlorinated to make an insecticide, (2) oxidized to make benzoic acid, (3) reacted with hydrogen sulfide in the presence of acid-type catalysts to make sulfur-containing resins and (4) reacted with hydrogen sulfide in the presence of ultraviolet light to make a β-mercaptoethyl cyclohexane. A catalyst suitable for the dimerization of a diolefin, e.g. butadiene to 4-VCH, is prepared by reducing iron nitrosyl chloride with a readily oxidizable metal, selected from tin, zinc, manganese and magnesium, or in the presence of an electrolytic cell, in an organic solvent in the presence of carbon monoxide. The catalyst is believed to be an iron nitrosyl carbonyl. The catalyst performs equally well as other iron nitrosyl catalyst systems. Analogous cobalt and nickel compounds will produce the analogous catalysts, but are not as active as the iron species. Alternatively and preferably, the catalyst is prepared by reacting FeCl₂ and NaNO₂ with carbon monoxide in a solvent in the presence of a readily oxidizable metal selected from tin, zinc, manganese and magnesium, or in the presence of an electrolytic cell. The catalyst contains a minimum of reducing agent and by-products. The catalyst thus produced can be isolated and stored in the absence of the butadiene monomer while retaining stability and activity. In general, the catalysts of this invention are suitable for dimerizing to cyclic products the class of conjugated diolefins. While butadiene is exemplified to make 4-VCH, other conjugated dienes can be cyclized similarly. Thus, isoprene and other conjugated diolefins can be dimerized to cyclic compounds. While ferrous chloride is the preferred compound to be employed in forming the complex used in the catalyst of the invention, other compouds are useful in preparing the catalysts. Thus, for example, [Fe(NO)₂Cl]₂ and FeCl₃ are useful for the preparation. Analogous compounds of cobalt and nickel are useful in preparing the analogous catalysts, but such catalysts are not as active as the iron catalysts. Organic solvents which may be used include, for example, ethers, such as diethyl and dibutyl ethers, tetrahydro-furan (THF), diethyleneglycol methyl ether (diglyme), ethyleneglycol methyl ether (monoglyme) ; organic esters such as propylene carbonate, ethylene carbonate and ethyl acetate; and nitriles such as acetonitrile and benzonitrile. Pressures employed for the reaction are those sufficient to maintain carbon monoxide in the organic solution, e.g. from atmospheric (101 kPa) to 1,000 psig (6,900 kPa gauge). Temperatures which can be used are those within the range of from ambient to 250°C, preferably from 25° to 100°C. The time of reaction will vary with the amounts of material present and with the pressure and temperature. Generally a time of from one to 48 hours is operable, but a time of no longer than 24 hours is usually sufficient to complete the reaction. The conditions for the dimerization of butadiene are well known to the art and operable with the catalysts of the present invention. The temperature range is from 20° to 175°C; the pressure range is from atmospheric to 1,000 psig (6,900 kPa gauge) and the reaction is conducted for a period of time of from 10 minutes to 24 hours. The following examples are representative of the catalyst preparation and its use: Example 1 Catalyst Preparation Into a 20 ml autoclave was placed 15.00 g of a 5% solution of [Fe(NO)₂Cl]₂ in tetrahydrofuran (THF) and 1.12 g of tin powder. The reactor was then flushed with CO (to remove air) and pressurized to 75 psig (518 kPa gauge) while the contents was stirred. The reactor was maintained at about 25°C with stirring for about five hours, after which time the reactor was vented and the solution filtered to remove insoluble matter, e.g. tin or tin compounds. Example A (comparative) The procedure of Example 1 was repeated except that nitrogen was substituted for CO gas, all other parameters remaining the same. Example B (comparative) Into a 300 ml autoclave was placed 10.12 g of 5% solution of [Fe(NO)₂Cl]₂ in THF, 45.94 g THF and 1.28 g n-octane . Tin powder was omitted in this experiment. The reactor was then flushed with CO and pressurized to 50 psig (345 kPa gauge), heated to 70°C and allowed to react for about 5½ hours while stirring. The reactor was then vented. Example 2 In the reactor of Example 1, 1.03 g tin powder was added to 10.0 g of a 5.0 percent solution of [Fe(NO)₂Cl]₂ in diglyme (diethylene glycol monomethyl ether). The reactor was then flushed with CO gas and pressurized to 90 psig (620 kPa gauge) while stirring its contents. The temperature was maintained at 25°C while stirring was continued for 48 hours, after which the reactor was vented and the solution filtered. Example 3 In the same reactor used in Examples 1 and 2 was placed 0.36 g FeCl₂, 0.19 g NaNO₂, 0.38 g Sn powder and 18.75 g diglyme as solvent. The reactor was then flushed with CO gas and pressurized with CO to 75 psig (518 kPa gauge) while stirring its contents. The temperature was maintained at 120°C with continued stirring for 20 hours, after which the reactor was vented and the solution filtered. Example 4 In another experiment propylene carbonate was employed as the solvent using the same reactor as in Examples 1 and 2. The reactant quantities were as follows: 0.37 g FeCl₂, 0.20 g NaNO₂, 1.19 g Sn powder and 18.0 g propylene carbonate as solvent. The procedure was the same as in Example 3 with the pressure being 90 psig (620 kPa gauge), the temperature 120°C and the reaction time 14 hours. The following examples show the use of the catalyst: Example 5 The Dimerization Reaction The catalyst solution prepared in Example 1 was placed in a 300 mL autoclave to which was added 180 g of butadiene and the reactor was pressurized to 300 psi (2070 kPa) with nitrogen. The reactor was stirred continually and the reaction allowed to continue for a sufficient time to complete the conversion of butadiene, this being determined by sampling at intervals during the reaction. Reaction time for this example was about 14 hours. Examples 6, 7 and 8 In the manner of Example 5, the dimerization was carried out using the catalysts prepared in Examples 2, 3 and 4, respectively. Results obtained using the above catalyst preparations are shown in the following Table:

Claims: A method for making a catalyst suitable for the dimerization of conjugated diolefins which comprises reacting (a) iron, cobalt or nickel chlorides and an alkali metal nitrite or (b) iron, cobalt or nickel nitrosyl chlorides with (c) carbon monoxide in a solvent therefor and in the presence of a readily oxidizable metal selected from tin, zinc, manganese and magnesium, or in the presence of an electrolytic cell. A method as claimed in claim 1 wherein the solvent for the reaction is an organic solvent and the conjugated diolefin is butadiene. A method as claimed in claim 2 wherein the organic solvent is an organic ether, ester or nitrile. A method as claimed in claim 3 wherein the organic ether is a cyclic ether or a glycol ether; the organic ester is an alkylene carbonate and the organic nitrile is acetonitrile. A method as claimed in claim 4 wherein the glycol ether is an alkyl ether of ethylene or diethylene glycol and the cyclic ether is tetrahydrofuran. A method as claimed in any one of the preceding claims wherein the reaction is conducted at a pressure of from atmospheric (101 kPa) to 1,000 psig (6,900 kPa gauge) and at a temperature of from ambient to 175°C. A method as claimed in claim 1 which comprises reacting iron chloride and sodium nitrite with carbon monoxide in an organic solvent in the presence of tin metal. A catalyst composition made according to the method of any one of the preceding claims. The use of the catalyst according to claim 8 for dimerizing butadiene.

Inventors: HEATON, DUANE H.
Applicants: THE DOW CHEMICAL COMPANY
Application year: 1990
Main classification: B01J31
IPC codes: C07B61, C07C13, B01J31, C07C2