IL23127A - Process for the oxidation of cyclo-hexanone and cyclohexanol - Google Patents

Description

Patent of cclohexanol a bo particularly tho is known to oxidize cyclohexane at elevated pressure and vated temperature by means of gases containing oxygen and if required in the presence of catalysts so as to give oyclohexanone and for example German Specification 465 and 1 067 429 and German Patent Specification 1 100 Formed as in the process are principally and dicarboxylic arboxylic acids or their lactones and a small amount of In addition to the temperature and catalyst having a decisive effect on the yield of the main produots oyclohexanone and also do the sise of the bubbles of oxidizing gas passed through the cyclohexane see for example Gorman Patent Specification 1 090659 as the oxygen conten of the oxidizing gas and good mixing of the reaction Good mixing not only of importance because concentration conditions of the should be equalized throughout the reaction chambe that a reaction product of the same composition is also always but is also intended to ensure the tion of the optimum reaction for the entire reaction good mixing is indispensable inasmuch as the oxidation of cyclohexane takes for the most part in products of different degrees of oxidation in succession and partly also side by first cyclohexanol and then monocarboxylic hydroxycarbolic formation of oyelohexanol and oyclohexanone from xane takes place during the induction period by way of radicals and Xn continuous operation and with a plurality of reactors connected in the first reactor necessarily shove With email reaction the thorough mixing of the reaction mixture does not cause particular Mechanical stirrers aro sufficient and likewise the utilization of the difference in density betveen that part of the liquid vhioh is charged with gas and that part thereof which not A volume of liquid containing gas bubbles rises the reaction chamber owing to its lover specific gives off the at sur and sinks to the bottom of the reaction vessel vhere the gas is This circulation can result sufficient if the reaction chamber is not too In the case of plants vith a production capacity of 1000 tons or more per month and correspondingly large oxidizing such stirring methods are not The problem has been solved by for example the of gas to the reactors comparison vith For reasons of reaction tics consistant vith a continuous method of it is pensable to connect a plurality of reactors in series if it is desired to obtain high yields for reasonable conversion step of connecting reactors in hovever has the disadvantage that each reactor must have gas fed into vith each reactor there is associated a separate apparatus together vith considerable expenditure for heat compensators and auxiliary it is rather costly to build oxidizing plants of very large for example an output of 3000 tone or more of cyclohexanone per for reasons of vith a reaction pressure of or more atmospheres the cylindrical oxidizing roactors heretofore An ideal solution of this problem bo the use of a single spherical reactor of large cubic this could bo constructed at relatively little cost with a relatively email As apparent from what has been said however this has been prevented by the fact that adequate mixing of the reaction mixture has occasioned difficulty in the case of large reaction It is true that tests have shown that sufficient thorough with the temperature equalization associated with the reaction and thereby an can be achieved if as largo an amount of oxidizin gas as possible passed through in a powerful This method however is not suitable fo continuous since with a throughput of oxidizing gas the pipe lines are gummed up and must be cleaned periodically this causes a lengthy interruption of operation each For the oxidation of an oxidizing gas containing at the most by and preferably even only by of oxygon is With continuous the inert nitrogen put in initially is naturally enriched with oxygen only during the starting period means of the oxidizing the air until desired concentration of oxyge has been howevor the oxidizing which has given up the major part of its oxygen the oxidizing reactor still contains only to by volumo of is the concentration of oxygen now becoming necessary being effected by addition of the calculated amount of In comparison with continuous oxidation with fresh this has the advantage that nitrogen does not have to be added constantly in order to reduce the concentration of The waste oxidising gas leaving tho oxidizing reactor and which is circulated in addition to a of unused also water cyclohexane and 27or reasons of and cyclohexane condensed out a of the recycled or circulated gas in separate devices The recovered cyclohexane is introduced into the oxidizing reactor the again and the is conveyed circulated gas is brought to tho necessary oxygon again by adding air and is into the oxidizing has now been found that a ter the circulated gas has left the oxidissing it not only contains the constituents already but other volatile compounds which resinify and thus result in fouling and blocking of the pipe This affects in particular those soctions of piping which aro between the oxidizing reactor and the compressor connectod in front of it has now been found that the of these which have not been further is already or by the supply of small amounts of the very compression of the circulated gas by the pressor necessarily connected in front of the oxidizing reactor produce the undesirable resinification It has been possible prevent the resinification by limiting the supply of compression Tho compression the compression work of a is all the g the greater tho ratio of final pressor in tho cylinder to intake pressure of tho pressor in An adequate limitation of tho supply of compression can be achieved in the compression of tho circulated oxidizing gas in a ratio of final pressure of the compressor to intake of tho compressor in cylinder is kept smaller that t It has been found that the limitation of pressure ratio to 1 is generally Undor certain for example with a large throughput and forced it prove to be necessary to go down to a ratio of to the process according to the invention for ing and by oxidation of cyclohexane in phase at elevated elevated pressuro and if required in the presence of catalysts by means of circulated dising gas after passing through the oxidizing is brought to an oxygen concentration of by volume at the most by adding air and then compressed by means of a compressor and pumped into the oxidising reactor is characterised in that during the compression of the circulated oxidizing gas by means of a compressor before it ontere the oxidizing reactor the pressure the ratio of output pressure of the compressor to intake pressure of the is smaller than t With the method of operation according to tho present it now possible to carry out the oxidation of in a single oxidizing reactor of any desired size and to the thorough mixing of the reaction mixture which is required for taining an optium yield by means of a powerful stream of It is now also for to employ in ticular a spherical reactor as oxidizing reactor of this The following Example serves the sole purpose of illustrating the process according to the invention more fully and is not intended to restrict the present invention in any mannor temperatures are given degrees to the process described in of open Patent Specification 1 was oxidised tinuously in tho liquid phase at 11 absolute and 15S C with atmospheric oxygen to give cyclohexanol and using three reactors connected in series each having a capacity of 7 cubic By adding to the the oxidizing adjusted to by volume of oxygon in The air compressed and the reaction by being introduced into the by 400 grams used as oxidation catalyst and cyclohexanone as reaction kg of hexane per hour for oxidation in continuous The waste gas issuing at the top of the reactors by volume of by volume of nitrogen and inert by of water vapour and by volume o The major part of this gas was recycled by means of a circulating 2200 of being added this way the result wae obtained that tho flowing into tho reactors constantly had an oxygon content of about by Part of the said waste gas was cooled and The heat content of this gas was utilized partly by heat exchange for preheating the quantity of cyclohexone supplied to the The cyclohexone deposited during the cooling and the water of reaction separated in a vessel and the cyclohexane was returned to tho Tho oxidation mixture was from tho oxidizing apparatus in proportion to the supply of fresh cyclohexane after working up in suitable fashion the cyclohexane recovered unchanged was tho oxidation not in pipes of the especially those of lay between the reacto and connected in front of began in a reduction in of up to 2 proasora internal ratio f 1 of c ratio of s 1 voro in the no ficGtion could be detected after Z The repetition o this experiment with a spherical reactor same insufficientOCRQuality

Claims (4)

1. 23127/2 l Process for preparing cyclohexanone and cyclohexanol bjt oxidation of cyclohexane in liquid phase at elevated temperature, elevated pressure and, if required, in the presence of catalysts by means of circulated oxidising gas which, after passing through the oxidizing reactor, is again brought to an oxygen concentration of, at the most, 10 by volume by adding air and then compressed by means of a compressor and pumped into the oxidising reactor again, characterised in that during the compression of the circulated oxidising gas by means of a compressor before it enters the oxidizing reactor again the pressure ratio, i.e. the ratio of output pressure of the compressor to intake pressure of the compressor, is kept smaller than 1.35«1 ·

2. Process according to Claim 1, characterised in that the pressure ratio is 1.01 to l.lOtl.

3. Process according to Claims 1 and 2, characterised in that it is carried out in a spherical reactor.

4. Process for preparing cyclohexanone and cyclohexanol substantially as hereinbefore described with reference to the Example. For the Applicants Dr. Yitzhak Hess