Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C29/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring
  • C07C29/48—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by oxidation reactions with formation of hydroxy groups
  • C07C29/50—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by oxidation reactions with formation of hydroxy groups with molecular oxygen only
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C35/00—Compounds having at least one hydroxy or O-metal group bound to a carbon atom of a ring other than a six-membered aromatic ring
  • C07C35/02—Compounds having at least one hydroxy or O-metal group bound to a carbon atom of a ring other than a six-membered aromatic ring monocyclic
  • C07C35/08—Compounds having at least one hydroxy or O-metal group bound to a carbon atom of a ring other than a six-membered aromatic ring monocyclic containing a six-membered rings
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C45/00—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds
  • C07C45/27—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by oxidation
  • C07C45/32—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by oxidation with molecular oxygen
  • C07C45/33—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by oxidation with molecular oxygen of CHx-moieties
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C49/00—Ketones; Ketenes; Dimeric ketenes; Ketonic chelates
  • C07C49/385—Saturated compounds containing a keto group being part of a ring
  • C07C49/403—Saturated compounds containing a keto group being part of a ring of a six-membered ring
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C2601/00—Systems containing only non-condensed rings
  • C07C2601/12—Systems containing only non-condensed rings with a six-membered ring
  • C07C2601/14—The ring being saturated

Definitions

• the invention is directed to a method for preparing a mixture comprising cyclohexanol and cyclohexanone.
• Cyclohexanol and cyclohexanone can be commercially produced from cyclohexane.
• the first step in such a process is oxidation of the cyclohexane by an oxygen-containing gas to produce cyclohexanol, cyclohexanone and cyclohexylhydroperoxide.
• the mixture of cyclohexanol (A) and cyclohexanone (K) is commonly referred to as "KA".
• cylcohexane is oxidised in the liquid phase with air.
• This oxidation is normally conducted on industrial scale, either uncatalysed or with a soluble cobalt catalyst, in one or more reactors at temperatures in the range of 130-200 0 C.
• the vaporised cyclohexane and other products in the gaseous effluent are condensed and recovered, and the off-gases leave the system.
• the KA product is recovered from the liquid effluent from the reactor or reactors, and the unreacted cyclohexane is recycled (Kirk-Othmer, Encyclopedia of Chemical Technology, John-Wiley & Sons, New York, 1979, 3 rd Edition, Vol. 7, pp. 410-416 and Ullmanns, Encyklopadie der ischen Chemie, Verlag Chemie, Weinheim, 1975, 4 th Edition, Vol. 9, pp. 689-698).
• a process of oxidising cyclohexane to produce a product essentially consisting of cyclohexanone and cyclohexanol in the presence of a binary catalyst system of cobalt and chromium is known from US-A-3 987 100.
• the only cobalt to chromium ratios disclosed for the step wherein cyclohexane is oxidised are in the preferred embodiment (Examples, Table 2), mentioning a cobalt concentration of 0.1 ppm and a chromium concentration of 0.04 ppm, which corresponds to an atomic ratio of cobalt to chromium of 2.2.
• a cobalt concentration of 0.1 ppm and a chromium concentration of 0.04 ppm which corresponds to an atomic ratio of cobalt to chromium of 2.2.
• the ratio of cobalt to chromium has an effect on the oxidation process.
• US-A-3 598 869 describes a process wherein cyclohexane is oxidised to obtain a mixture of (a) cyclohexanol and cyclohexanone (KA) and (b) a mixture of carboxylic acid derivatives of cyclohexane (COP acids) in a particularly suitable ratio (Ae. of about 1 :1 ) of COP acids to KA for further conversion to nylon salts in the presence of at least one catalyst of the group of cobalt and chromium.
• Catalyst concentrations can be between 1 ppm and 200 ppm, calculated as the metal, or higher.
• chromium is used and no cobalt.
• this document discloses high cyclohexane conversions such as in between about 14 mol% and 30 mol%.
• EP-A-O 063 931 relates to a process for the catalytic oxidation of a liquid cycloparaffin to partial oxidation products thereof, which comprises introducing amolecular oxygen-containing gas into a cycloparaffin of from 5 to 12 carbon atoms in the presence of an oxidation catalyst comprising a combination of a cobalt compound and a chromium compound, said oxidation catalyst being soluble in the cycloparaffin, said cobalt compound having ligands selected from the group consisting of dialkyl phosphate, dicycloalkylphosphate and alkylcycloalkylphosphate, and mixtures thereof, the ratio of cobalt compound to chromium compound being greater than 1 :1 on an atomic basis. This means that there is more cobalt than chromium.
• SU-A-929 213 describes a catalyst for the oxidation of pure cyclohexane.
• two experiments are shown with different cobalt to chromium ratios (respectively of 38 vs. 62 %; and of 23 vs. 77 % of the naphthenates), both experiments show substantially the same selectivity.
• the concentration of the sum of cobalt and chromium in the reaction medium is 1 ppm by weight in each of these experiments, and the cyclohexane conversion is higher than 5 mol%.
• the highest K/A ratio is 1.05.
• K/A ratio molar cyclohexanone/cyclohexanol ratio
• the invention is directed to a method for preparing, at high selectivity towards desired products, a mixture comprising cyclohexanol and cyclohexanone in a molar cyclohexanone/cyclohexanol ratio of at least 1.2 and with a cyclohexane conversion below 5 mol%, comprising oxidising cyclohexane in a liquid phase, said oxidising being catalysed by a cobalt compound and a chromium compound, the atomic cobalt to chromium ratio being in the range of 0.05 to 0.8, wherein the sum of the concentrations of cobalt and chromium is 0.05-0.9 ppm by weight based on the total weight of the reaction mixture, and wherein the cobalt compound and chromium compound are dissolved in the liquid phase.
• the process of the invention wherein a specific cobalt chromium catalyst is utilised at a cyclohexane conversion below 5 mol%, advantageously allows achieving, at a specific conversion level (e.g. of 3 or 4 mol%), both a high value of K/A and a higher selectivity than is achieved with prior art processes.
• Selectivity in this regard is defined as the sum of desired products (cyclohexanol, cyclohexanone, and cyclohexylhydroperoxide) divided by the total amount of cyclohexane that has been converted on a molar basis.
• the process of the invention at the same time yields an advantageously high K/A ratio (such as a molar K/A ratio of 1.2 or more, or even a molar K/A ratio of 1.4 or more).
• a high K/A ratio is desirable, because it minimises subsequent conversion of remaining cyclohexanol to the final product cyclohexanone.
• the K/A ratio can for instance be as high as 1.6.
• the catalyst used in the process of the invention is a combination of a cobalt compound and a chromium compound.
• the term "compound” as used in this context includes complexes, salts, and the like.
• the cobalt can be present either as Co" or as Co'". In terms of solubility, compounds wherein the cobalt is present as Co" are preferred.
• the chromium compound can be present as Cr'" or even higher oxidation states. In practice, the chromium will usually be present as Cr'" in the chromium compound.
• the cobalt compound and/or chromium compound can comprise one or more ligands selected from porphyrins, phthalocyanines,
• carboxylates such as acetates, propanoates, butyrates, octanoates, benzoates, naphthenates, and
• the cobalt compound and/or chromium compound can comprise one or more ligands selected from the group consisting of acetylacetonates, octanoates, naphthenates, bipyridines, porphyrinates, and phthalocyanates.
• the cobalt compound and/or chromium compound comprise one or more ligands
• the one or more ligands can be present in excess.
• the atomic ratio of cobalt to chromium in the oxidation catalyst of cyclohexane is in the range of 0.05-0.8.
• the ratio of cobalt to chromium can be in the range of 0.1-0.5, more in particular in the range of 0.15-0.35.
• the atomic ratio of cobalt to chromium in the catalyst is of particular importance in obtaining a product having a high K/A ratio, along with a high selectivity. It was found that either the K/A ratio or the selectivity considerably decreases if the atomic cobalt to chromium ratio is higher than 0.8 and/or if the total metal concentration is higher than 0.9 ppm.
• the K/A ratio remains high but the selectivity drops to too low values (e.g. to less than 86% at 3 mol% conversion; respectively less than 84% at 4 mol% conversion).
• the cobalt compound and the chromium compound are dissolved in the liquid phase.
• the cobalt/chromium catalyst is a homogeneous catalyst.
• the cyclohexane oxidation process of the invention is a homogeneous catalysis process.
• the selectivity and/or the K/A ratio were found to increase, generally at decreasing values for the sum of the concentrations of cobalt and chromium, at an atomic ratio of cobalt to chromium in the range of from 0.05 to 0.8, and at conversions in the range of from 3 mol% to just below 5 mol%.
• the optimum of the total concentration of cobalt and chromium is in the range of from 0.05 to 0.9 ppm.
• the sum of the concentrations cobalt and chromium is 0.05-0.9 by weight based on the total weight of the reaction mixture, in particular 0.1-0.7 ppm by weight, more in particular 0.2-0.6 ppm by weight, especially at about 0.5 ppm.
• the cobalt concentration during the oxidation reaction can suitably be
• 0.01-0.4 ppm by weight of the total reaction mixture in particular 0.05-0.2 ppm by weight.
• the chromium concentration during the oxidation reaction can suitably be 0.04-0.8 ppm by weight of the total reaction mixture, in particular 0.1-0.5 ppm by weight.
• Such low amounts of cobalt and chromium are advantageous in view of environmental aspects, as well as in reducing fouling problems. Moreover, it was found that these relatively low amounts of catalyst still yield satisfactorily high conversion (such as 2-just below 5 mol%) with acceptable residence times.
• the process of the invention has a cyclohexane conversion of below 5 mol%, in particular of 2.5-4.5 mol%, more in particular 3-4 mol%.
• the conversion can largely be influenced by the residence time of the reaction products in the oxidising reactor(s).
• a cyclohexane conversion of below 5 mol% is advantageous, because the selectivity decreases quickly at or above a conversion of 5 mol%.
• the amount of cyclohexane to be evaporated becomes rather high.
• the cyclohexane oxidation of the invention can suitably be conducted in a reactor system, comprising one or more oxidation reactors (such as 3-8), which system preferably has plug flow characteristics, such as multiple reactors in series, for instance multiple CSTRs (Continuous Stirred Tank Reactors) in series or multiple bubble columns in series.
• the reaction temperature will normally be at least 130 0 C, in particular at least 140 0 C. It is not preferred that the reaction temperature exceeds 180 0 C, in particular 170 0 C, because at higher temperatures there is so much decomposition of cyclohexylhydroperoxide that the selectivity goes down.
• the residence time is usually in the range of 1-120 minutes, such as 5-90 minutes, in particular 10-60 minutes.
• the cyclohexanone/cyclohexanol mixture can be used for the preparation of adipic acid. Furthermore, after appropriate isolation of cyclohexanone from the obtained mixture, the isolated cyclohexanone can be used for the preparation of cyclohexanone oxime, caprolactam and nylon.
• CH x feed a cyclohexane feed as used in a cyclohexane oxidation plant
• CH x feed 1.0326 g of biphenyl (internal standard)
• 0.1673 g of a solution of Cr(acac) 3 in cyclohexane (249.9 ppm Cr) was placed in a Hastelloy fed-batch reactor.
• chromium was used with a concentration of 0.43 ppm in the CH x feed.
• the system was pressurised with N 2 up to 10-1 1 bar and heated up to 156 0 C under a 30 NL/h nitrogen flow while stirring at a rate of 1300 rpm. At reaction temperature, the nitrogen flow was changed for a 30 NL/h flow of 14 % O 2 in N 2 . Samples were taken at regular intervals and analysed by gas chromatography. During reaction, CO and CO 2 were continuously monitored in the off-gas.
• Comparative Example B A mixture of 97.80 g of CH x feed, 1.0090 g of biphenyl (internal standard), and 0.3364 g of a solution of Cr(acac) 3 in cyclohexane (249.9 ppm Cr) was placed in the same reactor as comparative example A. In the present comparative example only chromium was used with a concentration of 0.86 ppm in the CH x feed. The reaction was carried out using the same conditions and in the same way as in Comparative Example A.
• Comparative Example F A mixture of 98.85 g of CH x feed, 1.0074 g of biphenyl (internal standard), 0.33 g of a solution of Co(EH) 2 in cyclohexane (149 ppm Co) was placed in the same reactor as comparative example A. In the present comparative example only cobalt was used with a concentration of 0.50 ppm in the CH x feed. The reaction was carried out using the same conditions and in the same way as in Comparative Example A.
• Example 2 A mixture of 96.02 g of CH x feed, 1.0041 g of biphenyl (internal standard), 0.6913 g of a solution of Cr(acac) 3 in cyclohexane (60.52 ppm Cr) and 0.16721 g of a solution of Co(EH) 2 in cyclohexane (149 ppm Co) was placed in the same reactor as comparative example A.
• the chromium and cobalt concentrations used were 0.44 ppm and 0.26 ppm in the CH x feed, respectively, giving a molar ratio of 0.52.
• the reaction was carried out using the same conditions and in the same way as in Comparative Example A.
• a mixture of 96.00 g of CH x feed, 1.0330 g of biphenyl (internal standard), 1.0675 g of a solution of Cr(acac) 3 in cyclohexane (60.52 ppm Cr) and 0.06899 g of a solution of Co(EH) 2 in cyclohexane (149 ppm Co) was placed in the same reactor as comparative example A.
• the chromium and cobalt concentrations used were 0.67 ppm and 0.10 ppm in the CH x feed, respectively, giving a molar ratio of 0.13.
• the reaction was carried out using the same conditions and in the same way as in Comparative Example A.
• Example 6 A mixture of 93.70 g of CH x feed, 1.0192 g of biphenyl (internal standard), 0.7500 g of a solution of Cr(acac) 3 in cyclohexane (60.52 ppm Cr) and 0.01931 g of a solution Of Co(EH) 2 in cyclohexane (149 ppm Co) was placed in the same reactor as comparative example A.
• the chromium and cobalt concentrations used were 0.48 ppm and 0.03 ppm in the CH x feed, respectively, giving a molar ratio of 0.06.
• the reaction was carried out using the same conditions and in the same way as in Comparative Example A.

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• 2009
  • 2009-12-11 CN CN2009801512038A patent/CN102256921A/zh active Pending
  • 2009-12-11 KR KR1020117016208A patent/KR20110098818A/ko not_active Withdrawn
  • 2009-12-11 BR BRPI0923002A patent/BRPI0923002A2/pt not_active Application Discontinuation
  • 2009-12-11 EP EP09799082A patent/EP2365953A1/de not_active Withdrawn
  • 2009-12-11 WO PCT/EP2009/066919 patent/WO2010069870A1/en not_active Ceased
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