Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Patent
1999-04-14
2000-06-13
Geist, Gary
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
568357, 568360, 568376, 568836, C07C 4533
Patent
active
06075169&
DESCRIPTION:
BRIEF SUMMARY
This is the U.S. National Stage application of PCT/EP97/05740 filed Oct. 17, 1997 now WO98/17612 published Apr. 30, 1998.
The present invention relates to a continuous process for preparing oxidation products of cyclohexane by catalytic oxidation with oxygen-containing gases in the liquid phase, where the gases are brought into contact essentially uniformly with liquid cyclohexane in at least one reaction zone.
Processes for oxidizing hydrocarbons using molecular oxygen and in particular the oxidation of cyclohexane to give cyclohexanol and cyclohexanone are known from the prior art. Thus, DE-A-21 36 744 and U.S. Pat. No. 3,957,876 describe a process for preparing solutions containing cyclohexyl hydroperoxide by zonewise oxidation of cyclohexane, in which process a mixture of cyclohexane and a soluble cobalt catalyst is allowed to flow from the top downward through a tray column and an oxygen-containing gas is allowed to flow in countercurrent from the bottom upward through the column. The column has an oxygen consumption zone at the upper end and adjacent thereto in a downward direction oxidation zones, with the latter each being able to be fed separately with different amounts of oxygen. The process is aimed exclusively at the preparation of cyclohexyl hydroperoxide which is obtained in an amount of 15% by weight, based on the total amount of oxidation products.
U.S. Pat No. 4,675,450 describes a process for preparing cyclohexyl hydroperoxide similar to DE-A-21 36 744, with the cyclohexane oxidation being carried out in the presence of a soluble cobalt catalyst and also a phosphoric ester.
DE-A-12 87 575 describes a process for the oxidation of liquid cyclohexane in a plurality of directly successive oxidation stages, with oxygen-containing gas being introduced into each oxidation stage. This introduction is carried out in such a way that the rate at which oxygen is fed into each stage corresponds essentially to the rate at which oxygen is consumed, with inert gas being additionally introduced into the last oxidation stage. This unavoidably results in a nonuniform oxygen feed rate and oxygen distribution in the reaction mixture, which leads to a reduction in yield. The reaction zone is divided into chambers by metal sheets which are bent downward and do not cover the entire cross section. The gas is fed in below these metal sheets into the descending gas phase of the subsequent oxidation stage, which can, in a reaction procedure for using "flooded trays" which is described as suitable, likewise lead to a nonuniform feeding-in of oxygen, to a nonuniform flow of the reaction mixture and, in the most unfavorable case, to formation of oxygen-containing gas spaces under the trays, which increases the danger of an ignitable mixture being formed and of an explosion.
DE-C-25 15 419, corresponding to U.S. Pat. No. 3,987,100, describes a process for preparing cyclohexanone and cyclohexanol by oxidation of cyclohexane in a tray column operated in countercurrent in the presence of a soluble, binary catalyst system containing from 0.1 to 5 ppm of cobalt and from 0.02 to 0.9 ppm of chromium. In this process, the individual trays are configured, for example, as perforated metal sheets through which the oxygen-containing gas can rise and the descending cyclohexane can flow.
Analogously to DE-A-12 87 575, oxygen-containing gas can be additionally introduced onto some or all of the trays (with the exception of an oxygen consumption zone at the top of the column). This introduction is again carried out in such a way that virtually all the oxygen introduced in each stage is also consumed in that stage. Since, in addition, the number and/or the size of the holes in the perforated metal sheets increases from the bottom to the top of the reactor and since no oxygen is fed into the upper trays, a nonuniform feeding-in of oxygen, a nonuniform oxygen distribution in the reactor and a nonuniform flow of the reaction mixture, as already described above for the case of DE-A-12 87 575, occur in this process. Since, in addition, the f
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Gann Martin
Markl Robert
Rehfinger Alwin
Schmitt Rudiger
BASF Aktiengesellshcaft
Geist Gary
Padmanabhan Sreeni
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