SELECTIVE PREPARATION OF CIS-PERHYDROACENAPHTHENE

Abstract: A cis-isomer of perhydroacenaphthene is selectively prepared through hydrogenation of acenaphthene by effecting hydrogenation at 80 to 200°C in the presence of a Ru and/or Rh based catalyst. A cis-isomer having the highest boiling point is obtained as a major product.

Description: This invention relates to the preparation of perhydro­ acenaphthene useful as a high boiling oil by hydrogenating acenaphthene. More particularly, it relates to a process for selectively preparing cis-perhydroacenaphthene in pure form rather than as a mixture of isomers, which can be subsequently used as an intermediate for such chemical reaction as synthesis of adamantanes without incurring any difference in reaction route, activation energy, and reaction yield. It is well known in the art to hydrogenate a polycyclic aromatic compound in an atmosphere of pressurized hydrogen in the presence of a noble metal-based catalyst such as Pt and Pd catalysts or a nickel-based catalyst such as Raney nickel and nickel/kieselguhr catalysts to eventually produce a corresponding perhydro compound. For acenaphthene, it is well known that by hydrogenat­ ing acenaphthene in the presence of a Raney nickel catalyst, perhydroacenaphthene is produced by way of tetrahydroace­ naphthene. US-A-3,349,140 discloses the preparation of increased amounts of saturated cis-isomers of bicyclic and tricyclic aromatic hydrocarbons using novel metal catalysts. EP-A-0 164 038 discloses a hydrogenation method for the preparation of a cis-isomer rich fluid consisting of a decahydronaphthyl- and cyclohexyl-substituted alkane compound using a catalyst of the platinum group metals selected from the group consisting of ruthenium, platinum, rhodium and iridium. As described in the literature (see J. Am. Chem. Soc., June 2, 1971, 2798), four stereoisomers are known for perhydroacenaphthene. The detail of these four isomers has not been generally investigated and no attempt has been made to selectively synthesize a particular isomer. Consequently, perhydroacenaphthene is usually available as a mixture of four isomers. It has never been attempted to selectively synthesize a particular isomer or a particular group of isomers. No problem is encountered with an isomer mixture when perhydroacenaphthene is merely used as a high-boiling oil. It is, however, desirable to selectively synthesize a particular isomer or a particular group of isomers in using perhydroacenaphthene as an intermediate for chemical reaction to a final product because the reaction route and the activation energy involved in the reaction vary with isomers, resulting in varying reaction yields. As long as the literature and patent publications are concerned, no such concept about perhydroacenaphthene has been reported. The Raney nickel used for hydrogenation requires a solvent for certain starting materials and is inconvenient because of short life and careful handling. SUMMARY OF THE INVENTION An object of the present invention is to provide a novel process for selectively preparing perhydroacenaphthene in high yields. Another object of the present invention is to provide a novel process for selectively preparing a particular isomer of perhydroacenaphthene, especially a cis-isomer having the highest boiling point as a main product. Perhydroacenaphthene is useful as an intermediate for the synthesis of medical compounds. We have discovered that in producing perhydroacenaphthene for such destination by hydrogenating acenaphthene in the presence of various hydrogenating catalysts, the ratio of the four isomers of perhydroacenaphthene produced can be controlled to a significant extent by a choice of the catalyst and reaction conditions. According to the present invention, there is provided a process for selectively preparing cis-perhydroacenaphthene which contains the highest boiling point cis-isomer as the main product by hydrogenating acenaphthene, which is characterized by effecting the hydrogenation reaction at a temperature of 80 to 200°C in the presence of a Rh based catalyst. BRIEF DESCRIPTION OF THE DRAWING The invention will be more fully understood by reading the following detailed description taken in conjunction with the accompanying drawing, in which: the only figure, FIG. 1 is a gas chromatogram of a mixture of four isomers of perhydroacenaphthene. DETAILED DESCRIPTION OF THE INVENTION Hydrogenation reaction of acenaphthene proceeds as follows. Four isomers are involved in perhydroacenaphthene. The isomers can be identified by, for example, the analysis chart obtained by gas chromatography using a packing material of the nature allowing materials to elute in the order of their boiling point. Based on a series of analysis results, it is supposed that peak Nos.1 and 3 in FIG. 1 are attributable to trans-isomers and peak Nos. 2 and 4 are cis-­ isomers. The conditions used in determining the gas chromatogram of FIG. 1 are shown below. Column: silicon OV-17, 2 m (dual) Detector: FID detector Initial temperature: 70°C, 4 minutes hold Heating rate: 6°C/min. Final temperature: 250°C, 16 minutes hold The process of the present invention is to selectively prepare a perhydroacenaphthene isomer corresponding to No. 4 peak in FIG. 1, that is, a cis-isomer having the highest boiling point. Typical prior art methods for preparing a mixture of four isomers of perhydroacenaphthene are by subjecting acenaphthene to hydrogenation reaction in the presence of a catalyst under a hydrogen pressure of about 1.013 to 2.026 × 10⁷ Pa (100 to 200 kg/cm²) at a temperature of about 100 to 300°C for several hours. Useful are catalysts comprising a carrier such as carbon and alumina having a noble metal such as Pd and Pt carried thereon and/or nickel-based catalysts such as Raney nickel. Making a further study on the preparation of perhydro­ acenaphthene from acenaphthene with the aid of various hydrogenating catalysts, we have discovered that a particular perhydroacenaphthene can be produced in a high yield and a high selectivity by carrying out the hydrogenation reaction under certain conditions using a specific catalyst. In order to preferentially produce a perhydro­ acenaphthene isomer corresponding to No. 4 peak in the gas chromatogram of FIG. 1, that is, the high boiling cis­ isomer, it is recommended to hydrogenate acenaphthene under a hydrogen pressure of 1.013 to 2.026 × 10⁷ Pa (100 to 200 kg/cm²) gauge at a temperature of 80 to 200°C, more preferably 100 to 180°C using a Rh based catalyst. The reaction can proceed at temperatures of lower than 80°C, but at a very low rate. At reaction temperatures of higher than 200°C, other isomers are produced in larger amounts, resulting in a reduced selectivity. Any Rh based catalysts may be used. Typical are carbon carried catalysts such as Rh/C catalysts having rhodium on a carbon carrier. The amount of the catalyst charged may be such that at least 0.025% by weight of metallic Rh is present based on the weight of acenaphthene. Catalyst amounts of 0.025 to 0.10% of Rh based on the weight of acenaphthene are preferred because the reaction rate is proportional to the catalyst charge. Metallic Rh leadings of 0.025 to 0.10% by weight correspond to catalyst charges of 0.5 to 2% when the catalyst contains 5% of Rh as is usually the case. With more than 2% by weight of the 5% Rh catalyst, a rapid reaction will take place to undesirably bring a quick rise of reaction temperature. The reaction time generally ranges from about 20 minutes to about 4 hours although it varies with the catalyst charge and the reaction temperature. A reaction time within 2 hours is sufficient for reaction at a temperature of about 200°C. The reaction time corresponds to the minimum time taken for the necessary hydrogen consumption since 5 moles of hydrogen must be consumed per mole of acenaphthene in order that acenaphthene reacts with hydrogen to form perhydroacenaphthene. EXAMPLES Examples of the present invention are presented below by way of illustration and not by way of limitation. All percents are by weight unless otherwise stated. Nos. 1 to 4 isomers are identified in the gas chromatogram of FIG. 1. Example 1 A shaking autoclave having an internal volume of about 60 ml was charged with 5 grams of acenaphthene and 0.1 gram of a 5% Rh/C catalyst and with hydrogen at an initial pressure of 1.357 × 10⁷ Pa (134 Kg/cm²) gauge. Reaction was effected at 150°C for 30 minutes. Perhydroacenaphthene was produced in a yield of 100%, containing 1.1% of No. 1 isomer, 3.6% of No. 2 isomer, and 4.4% of No. 3 isomer, indicating a selectivity of No. 4 isomer of 90.9%. Example 2 Acenaphthene was hydrogenated by the same procedure as in Example 1 except that the catalyst was replaced by a 0.5% Rh/Al₂O₃ catalyst and reaction was effected at 125°C for 40 minutes. Perhydroacenaphthene was produced in a yield of 100%, containing 3.4% of No. 1 isomer, 4.7% of No. 2 isomer, and 4.1% of No. 3 isomer, indicating a selectivity of No. 4 isomer of 89.7%. Comparative Example Acenaphthene was hydrogenated by the same procedure as in Example 1 except that the catalyst was replaced by a 5% Pd/C catalyst and reaction was effected at 160°C for 6 hours. No substantial change was observed in the distribution of reaction products at the end of 4 hour reaction. Perhydroacenaphthene was finally obtained in a yield of 99.6%. The yields of Nos. 1 to 4 isomers were 33.5%, 11.8%, 24.5%, and 29.7%, respectively. In producing perhydroacenaphthene by hydrogenating acenaphthene, the process of the present invention can successfully produce perhydroacenaphthene in high yields and selectively obtain a cis-isomer having the highest boiling point by employing a proper catalyst and reaction conditions. Perhydroacenaphthene is used not only as high boiling oil and traction drive oil, but also as an intermediate for the production of adamantanes. In the latter case, the possible selective preparation of a particular isomer in high yields according to the present invention offers a very useful reaction intermediate which ensures efficient synthesis of the destined product without incurring any variation in reaction route, activation energy and reaction yield.

Claims: 1. A process for selectively preparing cis-perhydro­ acenaphthene which contains the highest boiling point cis-isomer as the main product by hydrogenating acenaphthene, characterized by effecting the hydrogenation reaction at a temperature of 80 to 200°C in the presence of a Rh based catalyst. 2. The process of claim 1 wherein the reaction temperature ranges from 100 to 180°C. 3. The process of claim 1 and/or 2 wherein the reaction is effected under a hydrogen pressure of 1.013 to 2.026 × 10⁷ Pa (100 to 200 kg/cm²). 4. The process of any of claims 1 to 3 wherein the reaction is continued for 20 minutes to 4 hours. 5. The process of any of claims 1 to 4 wherein the catalyst is present in an amount to provide 0.025 to 0.10% of Rh metal based on the weight of acenaphthene. 6. The process of any of claims 1 to 5 wherein the catalyst has rhodium on a carbon carrier. 7. The process of any of claims 1 to 5 wherein the catalyst has rhodium on an alumina carrier.

Inventors: NARUSE, YOSHIHIRO, SUZUKI, TOSHIHIDE
Applicants: KAWASAKI STEEL CORPORATION
Application year: 1987
Main classification: C07C5
IPC codes: B01J23, C07C13, C07B61, C07C1, C07C67, C07C5