Method of Producing Cyclohexane Derivatives Directly From Aromatic Hydrocarbons

This invention relates to a method for producing cyclohexane derivatives. More specifically this invention relates to a method for producing a cyclohexane derivative represented by following formula (I) directly from an aromatic hydrocarbon: ##STR1##

wherein X is halogen, an OH or CAc group, wherein Ac is an acyl group having 1 to 3 carbon atoms, R is a lower alkyl group having 1 to 3 carbon atoms, and n is an integer from 0 to 2.

The cyclohexane derivatives are very important raw materials in synthetic chemical industries. Cyclohexanol and its ester derivatieves are used as raw materials for making synthetic polymers or solvents.

Heretofore, various methods for producing cyclohexanols have been proposed. Cyclohexanol, for example, can be produced by oxidation of cyclohexane with molecular oxygen in the presence of a boric acid catalyst or a transition metal catalyst such as cobalt naphthenate. Cyclohexanol can also be obtained by hydrogenation of phenol which can be produced by oxidation of cumene, prepared from benzene. All of these methods used for commercial production of cyclohexanol have hydrogenation and oxidation steps. So far as the hydrogenation process step is concerned, the conversion of the starting materials and the selectivity of the products are substantially quantitative. But the oxidation process step for introducing a hydroxyl group onto the benzene nucleus or into the cyclohexane ring is only barely satisfactory, because the process step often includes complex operations or the percentage conversion in the process step should be kept comparatively low in order to obtain products with a high selectivity.

The halogenated derivatives of cyclohexane have usually been produced by halogenation of cyclohexane or by reaction of cyclohexanol with hydrogen halides. In the former method expensive and toxic molecular halogen should be used and a large amount of hydrogen halide is obtained as a byproduct. The latter method inevitably has the same problem as mentioned above in respect of cyclohexanols.

The cyclohexane derivatives of formula (I) can be produced from cyclohexene in comparatively good yield. Therefore, if cyclohexene can be obtained from benzene by selective hydrogenation, this route from benzene to the cyclohexane derivatives is expected to be a good method for producing the cyclohexane derivatives. Thus, some methods of selective hydrogenation of benzene to cyclohexene have been proposed in U.S. Pat. Nos. 3,391,206 and 3,793,383 etc., and in German Application No. 2,221,137.

In these known methods, however, the conversion of benzene should usually be kept at an extremely low level to obtain a high selectivity of cyclohexene, because cyclohexene is hydrogenated more easily then benzene. In some cases a catalyst of complex composition must be used in the selective hydrogenation. Therefore the industrial application of the method is very difficult.

Thus, the object of the present invention is to provide a method for producing cyclohexane derivatives represented by formula (I) directly from benzene and its derivatives, in one step.

We now have found that the cyclohexane derivatives having the general formula (I) can be obtained by allowing the aromatic hydrocarbon to react with a compound HX, wherein X is the same as mentioned above, under hydrogenation conditions in the presence of a strong acid and a hydrogenation catalyst.

The type of aromatic hydrocarbon used as a starting material is not essentially restricted, but from the practical point of view benzene derivatives having a few alkyl substituents having 1 to 3 carbon atoms are preferable. For example benzene, toluene, ethylbenzene, cumene and xylenes are preferably used. Benzene is most preferable. The quality of the aromatic hydrocarbon is also not specifically restricted, so far as it does not contain impurities which cause the activity of the hydrogenation catalyst to deteriorate. An aromatic hydrocarbon which may be fed to a conventional hydrogenation process is preferably used in the present invention.

The amount of the aromatic hydrocarbon may be 0.1 to 40 mol%, preferably 2.0 to 40 mol%, on the basis of the total amount of the aromatic hydrocarbon and the reagent HX.

The reagent HX may be water, a hydrogen halide such as hydrogen chloride, bromide, or iodide, and carboxylic acid. The carboxylic acids having 1 to 3 carbon atoms such as formic, acetic and propionic acids are preferably used. Acetic acid is most preferable among the carboxylic acids.

The strong acid used in the present invention may be a protonic acid having an acidic dissociation constant pKa of less than 4.0, preferably 3.0, or a Lewis acid having an acid-acting property comparable thereto and having stability under reaction conditions in the present invention. The strong acid may be sulfuric acid, hydrogen chloride, hydrogen bromide, hydrogen iodide, phosphoric acid, an acidic sulfate such as potassium bisulfate, ammonium bisulfate, trifluoroacetic acid, trifluoromethanesulfonic acid, an alkanesulfonic acid such as methanesulfonic acid cation exchange resin such as an ion exchange resin having strongly acidic functional groups selected from the group consisting of sulfonic acid, phenylsulfonic acid and phosphonic acid, boron trifluoride, a heteropolyacid such as phosphotungstic acid, silicotungstic acid, phosphomolybdic acid, or silicomolybdic acid, an aromatic sulfonic acid such as benzenesulfonic acid, toluenesulfonic acid, or a solid acid such as alumina, silica alumina, crystalline aluminosilicate, titania or a mixture thereof, etc.

The presence of the strong acid in the reaction mixture is essential to the invention. The amount of the strong acid may preferably be more than 0.01 mol% on the basis of the reagent HX which exists in the reaction mixture. A still more preferable amount is more than 2 mol%.

When the reagent HX is a hydrogen halide, it also can play a role as a strong acid, and it is not necessary to add a strong acid other than that. When the reagent HX is H.sub.2 O or a carboxylic acid, at least one strong acid should be added to the reaction mixture. The cyclohexylester of the strong acid tends to be produced in a relatively large amount, when a strong acid having protonic oxygen is used in a high concentration. For practical purposes, such an ester is hydrolyzed to form a cyclohexane derivative of formula (I), and is thereafter recovered from the reaction mixture. In the present invention the conversion of the aromatic hydrocarbon may preferably be less than 80%. At a conversion of more than 80%, the selectivity of the cyclohexane derivative (I) becomes comparatively low.

The hydrogenation catalyst used in the present invention may usually contain Group VIII metals or its compounds. The Group VIII metals may preferably be noble metals selected from the group consisting of ruthenium, rhodium, palladium, iridium and platinum. Ruthenium, rhodium, and palladium are more preferable. The catalyst may contain at least one noble metal and the combined use of two or more metals may be effective, and may fall within the range of this invention. The noble metal catalyst may be used in an optional form. The usual hydrogenation catalysts for aromatic hydrocarbons may be used in the present invention.

The noble metal catalyst may be in a form of sponge, fine powder, colloid, and supported form. For example, active carbon, alumina, silica, silicaalumina, boria, tungsten trioxide, molybdenum oxide, zeolites, asbestos, other known solid acids and cation exchange resins may be used as carrier. Some acidic carriers may play a role as the strong acid. An alloy of the noble metal with other metals such as copper, silver, and gold may also be used.

The quality of hydrogen gas used in the present invention is not specifically restricted, except that the hydrogen may not contain impurities deteriorating the activity of the hydrogenation catalyst. Hydrogen may contain an inert gas such as nitrogen, helium, argon, carbon dioxide or methane.

The pressure of hydrogen does not essentially influence the reaction of the present invention. The preferable partial pressure of hydrogen is 0.01 to 300 Kg/cm.sup.2, preferably 0.5 to 150 Kg/cm.sup.2. In view of the reaction rate and the pressure restriction of the reaction apparatus, the reaction may preferably be carried out under a pressure of 0.01-500 Kg/cm.sup.2, more preferably 0.5-150 Kg/cm.sup.2. The reaction temperature is 0.degree.-300.degree. C., preferably 20.degree.-300.degree. C.

In the embodiments of the present invention, the reaction may be carried out in an inert solvent such as methanol, dioxane, cyclohexane or m-octane, etc.

The reaction products of the present invention are mainly cyclohexane derivatives of formula (I) and cyclohexane or its alkyl derivatives. In some cases, cyclohexane, phenylcyclohexane, cyclohexanone, or their alkyl derivatives are produced. The amounts of other byproducts are negligible under usual reaction conditions. The recovery of the cyclohexane derivatives (I) from the reaction mixture can be easily carried out according to conventional methods. The reaction of the present invention may be carried out either continuously or batchwise.

The mechanisms of the reaction in this invention have not been clearly understood, but the practical superiority of the present invention may be explained as follows in comparison with the selective hydrogenation of benzene to cyclohexene mentioned above. In the latter reaction, it is very difficult to enhance the conversion of benzene without sacrificing the selectivity of cyclohexene, because cyclohexene is more easily hydrogenated than benzene. On the other hand, in the former reaction which may be referred to as a "hydrogenohydration" process, the products of the formula (I) result from the addition of the reagent HK such as water etc. to an intermediate carbonium ion formed by the protonation of the intermediate cycloolefins which are formed in the hydrogenation step. The products are usually less reducible than benzene, therefore, it is possible to enhance the conversion of benzene to obtain final products of the formula (I) without sacrifice of selectivity.

The following examples will serve to further illustrate the present invention

The terms, conversion, yield, and selectivity, used in the examples are defined as follows. ##EQU1##

In a 100 ml. flask were placed 10 ml. of glacial acetic acid, 4 ml. of benzene, 1 ml. of boron trifluoride-diacetic acid complex, and 0.5 g. of 5% ruthenium on carbon catalyst. Stirring was provided by a bar magnet (sheathed with poly-tetrafluoroethylene) placed inside the flask. The bar magnet was set in motion by an external magnetic stirrer. After the flask was flushed with hydrogen, the contents of the flask were warmed to 70.degree. C. for 10 hours at an atmospheric pressure of hydrogen. Then, the flask was chilled in an ice-water bath, and to the flask, 60 ml. of ether was added. The ether layer separated, was washed with 10% sodium carbonate and with saturated sodium chloride, and was subjected to analysis by means of a gas-liquid chromatograph. This analysis showed that 1.2% of the benzene reacted with hydrogen and acetic acid to produce cyclohexyl acetate with a selectivity of 1% along with cyclohexane.

Hydrogenation catalysts were examined for activity and selectivity in conversion of benzene to cyclohexyl acetate. In each experiment, an appointed volume of glacial acetic acid, an appointed volume of benzene, 1 ml. of boron trifluoride-diacetic acid complex and an appointed amount of hydrogenation catalyst were treated at atmospheric pressure of hydrogen in a manner similar to that set forth in Example 1. The following table shows the reaction conditions and the results obtained.

In a manner similar to that set forth in Example 1, 5 ml. of benzene, 13 ml. of 50% sulfuric acid, and 0.5 g of 5% ruthenium on carbon, were treated under atmospheric pressure of hydrogen, at 70.degree. C. for 12 hours. The analysis of the reaction mixture by means of a gas-liquid chromatograph, showed that 1.1% of the benzene was converted into cylohexanol with a selectivity of 1.8%.

In a high pressure glass bomb with a bar magnet (sheathed with polytetrafluoroethylene) set in motion by an external magnetic stirrer, were placed 10 ml. of glacial acetic acid, 4 g of benzene, 1 ml. of boron trifluoride-diacetic acid complex, and 0.2 g of 5% ruthenium on carbon catalyst. The bomb and the contents thereof were heated at 75.degree. C., pressured with 5 Kg/cm.sup.2 G of hydrogen, for one hour. Then, the bomb was chilled in an ice-water bath, and the reaction mixture was treated in a manner similar to that set forth in Example 1 and subjected to analysis by means of gas-liquid chromatography. This analysis showed that cyclohexyl acetate was produced with a selectivity of 3.4% along with cyclohexane from 5.2% of benzene initially charged.

In each experiment, 1 ml. of acetic acid, 1 g. of benzene, 0.5 ml. of boron trifluoride-diacetic acid complex, and 50 mg. of a hydrogenation catalyst were treated at 75.degree. C. and 5 Kg/cm.sup.2 G of hydrogen in a manner similar to that set forth in Example 6. The following table shows the results obtained.

In a manner similar to that set forth in Example 6, 4 g. of benzene, 8 ml. of 55% sulfuric acid, and 0.2 g. of 5% ruthenium on carbon were treated. After reaction at 70.degree. C. and at an atmospheric pressure of hydrogen, for 45 minutes, the reaction mixture was analyzed by means of a gas-liquid chromatograph. The data showed that 6% of the benzene was converted into cyclohexanol with a selectivity of 1.5%.

A palladium-containing cation exchange resin was prepared from 3.5 g of tetramine palladium (II) dichloride, Pd(NH.sub.3).sub.4 Cl.sub.2, 30 g of Amberlyst 15 (a cation exchange resin supplied from Rohm & Haas Co.) in the sodium form. They were mixed in 300 ml. of distilled water, for 90 min., and filtered. The solid was washed with distilled water, then with ethanol, and dried at 100.degree. C. under reduced pressure. The resin was treated with 300 ml. water and 80 ml. of an 80% aqueous solution of hydrazine, at 80.degree. C. for 40 min., and filtered. The resin was placed on a column and eluted with 5% aqueous hydrochloric acid, and washed with about 2000 ml. water (at that point it was chloride free), then with alcohol and finally with ether. It was dried at 100.degree. C. for 2 hours under reduced pressure. The product was a catalyst comprising an ion exchange resin of sulfonic acid type which includes zero valent palladium in its resin matrix.

The catalyst was used for the hydrogenohydration of benzene. In a manner similar to that set forth in Example 6, 3 ml. of glacial acetic acid, 2 g. of benzene, and 0.2 g of the said catalyst were heated at 110.degree. C. for 20 hours under hydrogen at 5 Kg/cm.sup.2 G. The analysis of the reaction mixture by means of a gas-liquid chromatograph showed that 4.6% of the benzene was converted into cyclohexyl acetate wth a selectivity of 0.3%.

In a manner similar to that set forth in Example 26, the preparation of catalysts and the hydrogenohydration of benzene were carried out. In each case, 3 ml. of glacial acetic acid, 2 g. of benzene, and 0.2 of a catalyst were treated under 5 Kg/cm.sup.2 G of hydrogen at an appointed temperature for an appointed time. The following table shows the results obtained.

In Table III, the following notes are applicable: in Example 27, the same catalyst as that of Example 8 was used. In Example 28, the cataylyst was prepared by using 0.7 g. of Pd(NH.sub.3).sub.4 Cl.sub.2 and 15 g. of Amberlite 200 (a cation-exchange resin from Rohm and Haas Co.). In examples 29 and 30, each catalyst was prepared by using 0.5 g. of rhodium trichloride trihydrate and 5 g. of Amberlyst 15 or Amberlite 200. In Example 31, the catalyst was prepared by using 0.5 g. of ruthenium trichloride monohydrate and 5 g. of Amberlite 200. In Examples 29, 30 and 31, the ruthenium and rhodium compounds were reduced to a zero-valent state by formalin in an aqueous solution of sodium hydroxide instead of hydrazine.

In a manner similar to that set forth in Example 6, 2 g. of benzene, 3 g of glacial acetic acid, 0.1 g. of a hydrogenation catalyst, and 0.1 g of a heteropolyacid catalyst were treated at 95.degree. C. and 5 kg/cm.sup.2 G of hydrogen. The following table shows the results obtained.

In a manner similar that set forth in Example 6, formic acid and benezene were treated in the presence of a hydrogenation catalyst and an acid-acting catalyst. After a reaction time of 24 hours the analysis of the reaction mixture by means of a gas-liquid chromatograph showed that cyclohexyl formate was the sole product. The following table shows the reaction conditions and the results obtained.

In a manner similar to that set forth in Example 6, 2 g. of an aromatic hydrocarbon, 4 ml. of a carboxylic acid, and 0.1 g. of 5% ruthenium on activated carbon catalyst were treated at 75.degree. C. and 5 Kg/cm.sup.2 G of hydrogen. The following table shows the results obtained.

In a manner similar to that set forth in Example 6, 1 g. of benzene, 2 ml. of 50% aqueous solution of sulfuric acid, and 20 mg. of a hydrogenation catalyst were treated at 70.degree. C. and 50 Kg/cm.sup.2 G of hydrogen. The following table shows the results obtained.

In a manner similar to that set forth in Example 6, 1 g. of benzene, 2 ml. of 50% sulfuric acid, 20 mg. of a hydrogenation catalyst and an appointed amount of an organic solvent were treated at 70.degree. C. and 50 Kg/cm.sup.2 G of hydrogen. The following table shows the results obtained.

In a manner similar to that set forth in Example 6, 2 ml. of benzene, 5 ml. of water, 0.2 g. of 2% rhodium on WO.sub.3 catalyst, and an appointed amount of phosphotungstic acid was treated at 95.degree. C. and 10 Kg/cm.sup.2 G of hydrogen for 24 hours. The following table shows the results obtained.

In a manner similar to that set forth in Example 6, 1 g. of benzene, 2 ml. of 50% sulfuric acid, 0.4 ml. of methanol, and 20 mg. of a hydrogenation catalyst were treated at 70.degree. C. The following table shows the results obtained.

In a manner similar to that set forth in Example 6, 1 g. of benzene, 2 ml. of 50% sulfuric acid, 20 mg. of a hydrogenation catalyst, and an appointed amount of a sulfate were treated at 70.degree. C. and 5 Kg/cm.sup.2 G of hydrogen. The following table shows the results obtained.

In a manner similar to that set forth in Example 6, 1 g. of benzene, 2 ml. of 50% sulfuric acid, and 0.1 g. of a hydrogenation catalyst were treated at 5 Kg/cm.sup.2 G of hydrogen. The following table shows the results obtained.

In a manner similar to that set forth in Example 6, 2 g. of benzene, 3 ml. of glacial acetic acid, and 0.2 g. of a catalyst were treated at 95.degree. C. and 5 Kg/cm.sup.2 G of hydrogen. The following table shows the results obtained.

In Table XIII, the following notes are applicable:

In Examples 86 to 88, Neobead MSC is composed of Al.sub.2 O.sub.3, Neobead P of 88% Al.sub.2 O.sub.3, 9% SiO.sub.2, and 3% Na.sub.2 O by weight, and Silbead W of 12% Al.sub.2 O.sub.3 and 88% SiO.sub.2. These were obtained from Mizusawa Industrial Chemicals Ltd.

In Examples 89 to 91, Zeolite Y was obtained from Union Carbide Co.

In Example 92, a binary metal oxide, TiO.sub.2 -Al.sub.2 O.sub.3, was prepared by a conventional co-precipitation method from a mixture of titanium chloride and aluminum nitrate in a 1:9 molar ratio.

A mixture of 5 g. of benzene, 50 ml. of 20% hydrochloric acid, and 300 mg. of 2% rhodium on silica was put into a 40 ml. flask of an atmospheric hydrogenation apparatus, and heated under atmospheric pressure of hydrogen at 60.degree. C. for 23 hours. After seperation from the reaction mixture, the organic layer was dried with 0.5 g. of anhydrous potassium carbonate, and submitted to gas-liquid chromatography. The data indicated that 0.13% of the benzene was hydrogenated, producing cyclohexylchloride and cyclohexane with 47.7% and 52.3% selectivity, respectively.

A charge of 5 ml. of benzene, 15 ml. of 30% hydrobromic acid, and 300 mg. of 2% rhodium on silica was heated under atmospheric pressure of hydrogen at 60.degree. C. for 23 hours as described in Example 93. The gas-liquid chromatogram of the products indicated that cyclohexylbromide with 31.6% selectivity was produced from 0.12% of the benzene of the initial charge.

A mixture of 5 ml. of benzene, 15 ml. of 20% hydrochloric acid, 3 g. of sodium chloride, and 300 mg. of 2% rhodium on silica was heated under the identical conditions as described in Example 93. The gas-liquid chromatogram of the products indicated that 0.13% of the benzene was converted into cyclohexylchloride with 63.8% selectivity.

A charge of 2 ml. of benzene, 5 ml. of 35% hydrochloric acid, and 200 mg. of 5% rhodium on silica was placed in a 20 ml. glass bomb and heated under 20 Kg/cm.sup.2 G pressure of hydrogen at 75.degree. C., for 20 hours. The organic layer was submitted to gas-liquid chromatography and the data indicated that 13.4% of the benzene was converted into cyclohexylchloride and cyclohexane with 34% and 66% selectivity, respectively.

These experiments were carried out in the same manner as described in Example 96 and the data are summarized in Table XIV.

These runs were performed in the same manner as described in Example 96 and the data are summarized in Table XV.

These runs were practiced in the same manner as described in Example 96 and the data were summarized in Table XVI.

A mixture of 1 g. of benzene, 2 ml. of 35% hydrochloric acid, and 50 mg. of 2% rhodium on active carbon was heated under 5.0 Kg/cm.sup.2 G pressure of hydrogen at 70.degree. C. for 24 hours. The gas-liquid chromatogram of the products indicated that 3.5% of the benzene was converted into cyclohexylchloride and cyclohexane with 2% and 98% selectivity, respectively.

These examples were performed in the same manner as described in Example 96 and the data are tabulated in Table XVII.

These runs were carried out in the same manner as described in Example 96 and the data are summarized in Table XVIII.

These examples were practiced in the same manner as described in Example 96, and the data are summarized in Table XIX.

In a glass vessel (ca. 35 ml.) having a coiled capillary vent together with a small bar magnet coated with polytetrafluoroethylene, were charged 2 ml. of benzene and 200 mg. of 10% rhodium on silica. The vessel was placed in a high pressure Hastelloy B bomb (ca. 100 ml.), and swept with dry hydrogen chloride. The bomb was filled with 10 Kg/cm.sup.2 G of hydrogen chloride and 40 Kg/cm.sup.2 G of hydrogen, and heated at 120.degree. C. while magnetically stirring for 16 hours. After the gas was released, the vessel was taken out, then the organic layer was submitted to gas-liquid chromatography. The data obtained indicated that the yields of cyclohexane and chlorocyclohexane were 35.4% and 1.7%, respectively.

These examples are carried out in the same manner as described in Example 129, and the data were tabulated in Table XX.