Title of Invention

"AN IMPROVED PROCESS FOR PRODUCTION OF PHENOLS"

Abstract

The present invention provides an improved method for the production of phenols by oxygenating benzene or benzenoid compounds in presence of water and iron powder or mixture of iron powder and cupric chloride . The oxygenation carried out in presence of stabilizer inorganic salt , at temperature ranging 0° - 50°C, for a period in the range of 1 - 16 hour and then all the metals and water used are removed from the reaction mixture, unreacted benzene or benzenoid compounds are also removed by conventional distillation method to get phenolic compound.

Full Text

This invention relates to a process for production of phenols. Phenols prepared by the process of preparation of present invention are phenols, cresols and naphthols. Phenol is an important compound useful in chemical industry. Phenol is commercially prepared by oxygenating cumene at 400-500°C and producing acetone as a by product. Cumene itself is produced for this purpose from benzene and propylene. The other methods of preparation of phenol are toluene-benzoic acid process, benzene sulphonation , phenol via cyclohexene, benzene chlorination , benzene oxychlorination methods, all of which involve multi-step high temperature reaction conditions.(Kirk- Othomer Encyclopedia of Chemical Technology Vol. 18, Fourth Edition, 1996, pp 595-598.). The direct conversion of benzene to phenol is an important field of research because , ' The direct conversion of benzene to phenol, which would decrease the number of synthetic steps and avoid the production of acetone, is a more desirable route'. ( J. P. Hage and D. T. Sawyer, J.Am.Chem.Soc. 777, 5617, 1995). The importance of introduction of molecular oxygen directly into a hydrocarbon rather than use of alternative sources such as iodosobenzene and hydroperoxides is observed by stalwarts (D. H. R.Barton , M. P. Gastiger and W. B. Motherwell; J Chem Soc Chem Comn.,41,1993). The following are some of the references available in literature for direct conversion of benzene to phenol by air/molecular oxygen. 1 .Hydroxylation of aromatics using molecular oxygen as the terminal oxidant without coreductant V. A. Durante, T.P. Wijesekera and S. Karmakar; US Pat. 5,952,532 (1999) In this method hydroxylation of aromatic hydrocarbons such as benzene, naphthalene or substituted aromatic compounds was carried out by molecular oxygen in presence of a catalyst in a range of temperature from 150-280° C and pressure from 100-2000 psig. The catalyst is made of transition metal selected from the group consisting of vanadium, niobium, copper, palladium, nickel and silver or their combinations. The catalyst was also had to contain chelating agents as promoter. Apart from that the catalyst had to be based on a solid support. The drawback of the method is that the reaction has to be carried under drastic conditions and the costly steps of preparation of catalysts are involved. 2.Method for hydroxylating aromatic compounds T.M. Barnhat and A.W. Hughes; US Pat.5,912,391 (1999) In this method aromatic compounds such as benzene, toluene and xylene are hydroxylated by reaction with oxygen and hydroquinone or a substituted hydroquinone in the presence of a pentavalent vanadium oxy-chelate with picolinic acid or a substituted picolinic acid. The drawback of the method is that hydroquinones are required here to generate hydrogen peroxide in situ which produces oxo-vanadium complexes to take part in the reaction. The method requires costly vanadium compounds and chelating agents. Apart from that the reaction temperature has to be maintained in the range of 30- 120°C and the reaction carried out in acetonitrile an environment-polluting organic solvent.. 3.Liquid phase oxidation of benzene with molecular Oxygen catalyzed by Cu-zeolite H. Nagahara, D. Fukuhara,; Jpn. Kokai Tokkyo Kono JP 04,368,348 [ 92,368,348]; CA 120: 33295Z According to the method disclosed in this patent, the liquid-phase direct oxidation of benzene to phenol with oxygen was achieved using heterogenous Cu(II)- ion exchanged zeolite catalysts in the presence of ascorbic acid as reducing agent. The drawback of the method is that ascorbic acid a costly reducing agent is used in the process. 4.Preparation of phenols by oxidation of aromatic compounds. H. Nagahara, D. Fukuhara; Jpn Kokai Tokkyo Koho JP 04,368,348; CA118:149837r In this method benzene is converted to phenol by reacting in acidic aqueous solution in presence of CuCI and ammonium ions at 150°C under a mixture of nitrogen andjtt^y^^or 24 hours to give phenol. The drawback of the method is that the reaction is to be conducted at 150°C and a Cu (I) compound is required which is easily oxidised to Cu(II) compound. 5.Direct oxygenation of benzene and its analogues into phenols catalyzed by oxovanadium complex with combined use of molecular oxygen and aldehyde. E. Hata, T. Takai, T. Yamada, T. Mukaiyama; Chem. Lett., 10, 1849-1852, (1994); CA 122: 9588t In this method benzene is oxygenated to phenol at room temperature by molecular oxygen in presence of a oxovanadium (IV) complex and crotonaldehyde at room temperature. The drawback of the method is that a costly vanadium compound along with a sacrificial aldehyde is required for the reaction. Aldehyde is first converted to the corresponding peracid which oxygenates benzene. 6.Process for producing phenols. M. Hamada, H. Niwa, M. Oguri, T. Miyake; Eur. Pat. Appln. EP 638,536; CA: 122:213769g The process comprises reacting an aromatic compound with oxygen and hydrogen in liquid phase in the presence of a catalyst comprising a noble metal of group VIII, which is supported on a carrier, and in the co-presence of a Vanadium-compound and diketone compound. Pt/zirconia, V(III) acetylacetonate, benzene and benzoquinone were reacted to give phenol. Using Pt-Pd/zirconia and naphthalene a- and b hydroxynaphthalenes were obtained. The drawback of the method is that costly catalysts on support are required here for oxygenation of benzene to phenol. 7.Manufacture of aromatic hydroxy compounds . F. Matsuda, K. Inoe, K. Kato; Jpn KokaiTokkyoKoho JP06,192,150 [94,192,150]; CA 121:230474d. In this method benzene, water, triphenyl phosphine and a mixture of nitrogen and oxygen gas are taken in an autoclave and temperature raised to 180°C to obtain phenol (3.1%). The drawback of the method is that high temperature and costly triphenyl phosphine are to be used. Also, both triphenyl phosphine and its oxide are to separated from phenol produced adding an extra step in the work up. 8.Conjugated oxidation of benzene and iron (II) ion by molecular oxygen in the presence of molybdenum (VI). G.A. Gamidov, M.M. Agaguseinova, U.A. Gassanova; Zh. Obshch. Khim. 66(6), 974-977 (1996); CA 126: 7765g In this method hydroxylation of benzene with oxygen in the presence of complexes of iron(II) and Mo (VI) in aqueous - organic or organic solution at 20-60°C afforded mainly a mixture of phenol, hydroquinone and 1,2-benzene diol. The drawback of the method is that easily oxidisable Fe(II) compound and Mo(VI) have to be used in the reaction. Also, a mixture of oxygenated products are obtained instead of the desired single compound phenol. 9.Preparation of aromatic hydroxy compound by direct oxidation of aromatic compounds. F. Matsuda, K. Inoe, K. Kato; Jpn Kokai Tokkyo Koho JP 0892 ,144 [9692,144]; CA 125 :58094z: In this method a mixture of benzene and iso-propanol was autoclaved with a mixture of O/N at 160° under 40kg/cm2G for 5 hr to give 3.1% phenol with a selectivity of 82.3%. The draw back of the method is that iso-propanol is to be utilised and the reaction can be carried out under drastic conditions only. 10. Preparation of phenol K. Mori, S. Takahashi, Y. Toshima; Jpn Kokai Tokkyo Koho JP 07, 238,042 [ 95, 238, 042]; CA 124 : 32502K In this method phenol is prepared by oxidation of benzene in presence of PdCl2 and VoCl2 loaded on SiO2 by a mixture of CO and O gas in presence of acetic acid at 130°C and high pressure of 30kg/cm2-G. The drawback of the reaction is that the catalysts PdCI2 and VoCI2 are to be loaded on SiO2 prior to the reaction and the reaction can be carried out under drastic reaction conditions only. 11.Heterogenous catalysts for the continues oxidation of benzene to phenol A. Kunai, K. Ishihata, S. Ito and K. Sasak; Chem Lett Pp 1967 - 1970 (1988) In this method oxidation of benzene was achieved by taking it in aqueous H2SO4 acid solution and acetonitrile in presence of Copper (II) sulphate and both air and hydrogen in presence of a Pd(5%) - SiO2 or platinum catalyst at room temperature and pressure. The drawback of the method is that the hydroxylation can not be stopped at the formation of phenol but benzene is converted to a mixture of phenol and hydroquinone. The main objective of the present invention is to provide an improved process for production of phenols which obviates the drawbacks of the present methods. Another objective of the present invention is to provide a method for oxygenation of benzene to phenol under mild conditions or a mixture of without formation of more oxygenated products p-hydroquinone, hydroquinone or catechol. Yet another objective of the present invention is to carry out the reaction at a temperature range of 20-30°C eliminating the requirement of heating of the reaction mixture. Still yet another objective of the present invention is to carry out the reaction in water eliminating the use of solvent to a minimum . Accordingly the present invention provides an improved method for the production of phenols which comprises oxygenating benzene or benzenoid compounds by air in presence of water and iron powder or mixture of iron powder and cupric chloride wherein iron powder or a mixture of cupric chloride and iron powder is in the ratio of 10 : 1.5 to 1:1 preferably in the ratio 1.5 : 1 in a solvent as herein described , in presence of stabilizer inorganic salt as described herein , at temperature ranging 0° - 50°C, for a period in the range of 1 - 16 hour, removing the metals as defined above from the reaction mixture, removing the water from the reaction mixture, removing unreacted benzene or benzenoid compounds by conventional distillation method to get phenolic compound. In an embodiment of the present invention the oxidizing reagent used may be iron powder and a mixture of iron powder and cupric chloride in presence of air and water. In another embodiment the ratio of cupric chloride and iron powder is in the ratio of 10: 1.5 to 1:1 preferably 1.5: 1 In another embodiment of the invention the solvent used may be such as water, 2-propanol acetonitrile-water, more particularly water. In yet another embodiment of the present invention the benzenoid compound used may be benzene, toluene and naphthalene. The inorganic salt used may be selected from sodium chloride, potassium chloride and barium chloride, more particularly sodium chloride. The detail of the method disclosed in this invention have been described in the following examples which are provided to illustrate the invention only and therefore, these should not be construed to limit the scope of the present invention. Example 1 : In a 100 ml stoppered conical flask taken benzene (5ml), deionized water (8ml) , iron powder (90 mg, 1.5 m mol) and cupric chloride (CuCl2. 2H2O,180mg.4,0 mmol), sodium chloride 300 mg (5%) of substrate, acetonitrile (1ml), and stirred with a magnetic stirrer for 14 hrs with occasional opening of the flask for introduction of air. Spot of phenol appeared after 2 hrs (TLC). Then added 0.5 ml cone. HCI and stirred for 1 hr to dissolve both the metals. Then the reaction mixture was filtered and the benzene and aqueous layers were separated in a separating funnel. Alternatively, from the reaction flask the benzene layer was taken out with the help of a pipette (4.5 ml). The benzene layer was dried over anhydrous sodium sulphate and GLC recorded (phenol 0.175mg/ml benzene). Example 2 : In a 100 ml stoppered conical flask taken benzene (5ml), deionized water (8ml) , iron powder ( 2.8 gm., 50 mmol) and stirred with a magnetic stirrer for 14 hrs with occasional opening of the flask for introduction of air. Spot of phenol appeared after 2 hrs (TLC). Then added 0.5 ml cone. HCI and stirred for 1 hr to dissolve the metal . Then the reaction mixture was filtered and the benzene and aqueous layers were separated in a separating runnel. Alternatively, from the reaction flask the benzene layer was taken out with the help of a pipette (4.5 ml). The benzene layer was dried over anhydrous sodium sulphate and GLC recorded (phenol 0.011mg/ml benzene). Example 3: In a 100 ml stoppered conical flask taken benzene (5ml), deionized water (8ml) , iron powder (90 mg, 1.5 m mol) and cupric chloride (CuCl2. 2H2O, 1.70 gm..10 mmol) and stirred with a magnetic stirrer for 14 hrs with occasional opening of the flask for introduction of air. Spot of phenol appeared after 2 hrs (TLC). Then added 0.5 ml cone. HCI and stirred for 1 hr to dissolve both the metals. Then the reaction mixture was filtered and the benzene and aqueous layers were separated in a separating funnel. Alternatively, from the reaction flask the benzene layer was taken out with the help of a pipette (4.5 ml). The benzene layer was dried over anhydrous sodium sulphate and GLC recorded (phenol 0.036 mg/ml benzene). Example 4 : In a 100 ml stoppered conical flask taken benzene (5ml), deionized water (8ml) , cupric chloride (CuCl2. 2H2O,1.70 gm. 10 mmol), and stirred with a magnetic stirrer for 14 hrs with occasional opening of the flask for introduction of air. Spot of phenol did not appear after 14 hrs (TLC). Then added 0.5 ml conc. HCI and stirred for 1 hr to dissolve both the metals. Then the reaction mixture was filtered and the benzene and aqueous layers were separated in a separating funnel. Alternatively, from the reaction flask the benzene layer was taken out with the help of a pipette (4.5 ml). The benzene layer was dried over anhydrous sodium sulphate and GLC recorded ( phenol, nil). Experiment 5: In a 100 ml stoppered conical flask taken benzene (5ml), 2-propanol (8ml), iron powder (2.8 gm 50 mmol) and stirred with a magnetic stirrer for 14 hrs with occasional opening of the flask for introduction of air. Spot of phenol did not appeared after 14 hrs (TLC). Then added cupric chloride ( 0.34 gm. 2 mmol) and stirred for another 10 hours. Formation of phenol was observed on TLC. Experiment 6 : In a 100 ml stoppered conical flask taken naphthalene (150 mg., 1.2 mmol), deionized water (8ml) , iron powder (62 mg, 1.0 mmol) and cupric chloride (CuCl2. 2H2O,170 mg.1.0 mmol), sodium chloride 70 mg ( 1mmol) and stirred with a magnetic stirrer for 14 hrs with occasional opening of the flask for introduction of air. Spot of both a- and b naphthols appeared after 2 hrs (TLC). Then added 0.5 ml cone. HCI and stirred for 1 hr to dissolve both the metals. Then filtered through a filter paper to remove unreacted solid naphthalene and residue washed with 5 ml x 2 water. The unreacted and residue naphthalene was taken in CHC13 , dried over anhydrous sodium sulphate, solvent removed and reduced pressure to obtain unreacted naphthalene (140 mg). The aqueous filtrate was extracted with CHCI3. The chloroform solution was dried over anhydrous sodium sulphate, solvent reduced under reduced pressure to obtain a solid mixture of - and β naphthol (2.5mg.). GLC recorded, :β naphthol ratio (63:37). Experiment 7: In a 100 ml stoppered conical flask taken toluene (5ml), deionized water (8ml) , iron powder (90 mg, 1.5 m mol) and cupric chloride (CuCl2. 2H2O,180mg.l.O mmol), sodium chloride 300 mg (5%) of substrate and acetonitrile and stirred with a magnetic stirrer for 14 hrs with occasional opening of the flask for introduction of air. Spot of cresols appeared after 2 hrs (TLC). Then added 0.5 ml conc. HCI and stirred for 1 hr to dissolve both the metals. Then the reaction mixture was filtered and the benzene and aqueous layers were separated in a separating funnel. Alternatively, from the reaction flask the benzene layer was taken out with the help of a pipette (4.5 ml). The toluene layer was treated with a 10% sodium hydroxide solution (3ml), the alkaline part was separated in a separating funnel treated with 50% HCI to make it acidic. Then it was extracted with CH2CI2 (5ml), the organic layer washed with 1 water (1ml), dried over anhydrous sodium sulphate. The organic solvent was removed under vacuum to obtain the phenolic part and it's GLC recorded. The ratio of cresols, o : m + p = 37:35:28 The main advantages of the present invention are : 1. The method is simple and can be carried out as one- pot reaction at room temperature using air as the source of oxygen. 2. Only one hydroxyl group is introduced to the aromatic substrate unlike reported methods where the reaction does not stop at the formation of mono-hydroxylation stage. 3. The reaction is specific for aromatic hydrocarbons only. 4. The reaction is carried out using water as solvent. 5. The reaction is carried out using a mixture of acetonitrile water (11:89) as solvent keeping the requirement of organic solvent to minimum. 6. The work up procedure is simple. 7. The unreacted substrate can be easily separated from the reaction mixture and recycled. We Claim: 1. An improved method for the production of phenols which comprises oxygenating benzene or benzenoid compounds by air in presence of water and iron powder or mixture of iron powder and cupric chloride wherein iron powder or a mixture of cupric chloride and iron powder is in the ratio of 10 : 1.5 to 1:1 preferably in the ratio 1.5 : 1 in a solvent as herein described , in presence of stabilizer inorganic salt as described herein , at temperature ranging 0° - 50°C, for a period in the range of 1 - 16 hour, removing the metals as defined above from the reaction mixture, removing the water from the reaction mixture, removing unreacted benzene or benzenoid compounds by conventional distillation method to get phenolic compound. 2. An improved process as claimed in claim 1 wherein the benzenoid compound used is selected from benzene, toluene and naphthalene. 3. An improved process as claimed in claims 1 - 2, wherein the solvent used is selected from water, 2-propanol acetonitrile- water, more particularly water. 4. An improved process as claimed in claims 1 to 3 wherein the inorganic salts used to stabilize Cu(l) ions is selected from sodium chloride, potassium chloride and barium chloride, more particularly sodium chloride. 5. An improved process as claimed in claims 1 to 4 wherein the reaction mixture is stirred at a temperature at a range of 0° - 50°C particularly in the range of 20°-30°C for a period of 12-16 hours. 6. An improved process as claimed in claims 1- 5 wherein the metals is removed by adding acid to dissolve the undissolved metals , said acid is selected from hydrochloric, sulphuric, nitric, acetic acid more particularly hydrochloric acid. 7. An improved process for production of phenols from benzene substantially as herein described with reference to examples.

Documents:

222-del-2001-abstract.pdf

222-del-2001-claims.pdf

222-del-2001-correspondence-others.pdf

222-del-2001-correspondence-po.pdf

222-del-2001-description (complete).pdf

222-del-2001-form-1.pdf

222-del-2001-form-19.pdf

222-del-2001-form-2.pdf

222-del-2001-form-3.pdf