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Patented Feb. 13, 1945 v ‘2,369,181 UNlTED . , STATES PATENT IOFFlCE 2,369,181 CONTROLLED OXIDATION OF ALICYCLIC HYDROCARBONS AND OF THEIR DERIVA TIVES Frederick F. Rust and William E. Vaughan,‘ Berkeley, Calif., assignors to Shell Development _ Company, San Francisco, Calif., a corporation 6! Delaware No Drawing. Application January so, 1943, Serial No. 474,222 12 Claims. (Cl. t>..‘60----586)v very di?lcult, it not commercially impossible, or at least greatly increase the cost‘ oi’ the ?nal - product or products. It is also freuqently de sirable to obtain predominantly carboxylic acids, organic peroxides, and/or ketones rather than mixtures containing them and large amounts of other oxygenated compounds, e. g. carbon mon oxide, carbon dioxide, aldehydes, alcohols, lac tones, and the like. Furthermore, it is frequent 10v ly important or at least desirable to obtain oxyg genated compounds having at least the same This invention relates to the controlled, non-, . explosive oxidation of alicyclic hydrocarbons and of their halogenated derivatives containing a re placeable hydrogen atom, and more particularly - pertains to the catalytic controlled oxidation of saturated alicyclic hydrocarbons. ‘In one 01' its more speci?c embodiments, the present invention is directed to the treatment of‘saturated alicy clic hydrocarbons which may or may not con tain saturated acyclic side chains attached there to, to produce high yields of predetermined car boxylic acids, organic peroxides and/or ketones ,_ (including diketories) having the same number number of carbon atoms per molecule as the starting organic material. In all such cases the of carbon atoms per molecule as the starting or previously known methods of partial oxidation 15 of hydrocarbons, whether they be catalytic or The oxidation of various hydrocarbons has been non-catalytic, are impractical because of the par e?'ected for a number of years both non-cata tial or complete decomposition of the starting lytically and in the presenceof various catalysts. organic materials to form carbon and compounds As a general rule, most if not all of these oxida containing fewer carbon atoms per molecule, as tions resulted in considerable decomposition of well as due to the above-mentioned formation of the hydrocarbons, i. e. cleavage of carbon-to mixtures of compounds which are oxygenated to carbon bonds of the organic starting material. a greater or lesser degree. Also, the products of reaction of such oxidations It is therefore the main object of the present contained various percentages of hydrocarbons invention to avoid the above and other defects, which have been oxidized to a greater or lesser 25 and to provide a novel process whereby high extent. For instance, the catalytic oxidation of yields of predetermined oxygenated organic com para?lnic, hydrocarbons in accordance with the pounds may be obtained. A further object of. teachings of the prior art, formed mixtures con the invention is to provide a process for the pro--v taining various percentages of carbon monoxide, duction of high yields of carboxylic acids, ke ganic material treated. ' carbon dioxide, ole?ns, water as well as some al dehydes, alcohols, acetals, esters, ketones ‘and other oxygenated compounds. Similarly, the catalytic oxidation of aromatic hydrocarbons, ' e. g. toluene, in accordance with the teachings of 30 tones, alcohols, and/or organic peroxides to the substantial exclusion of other less desirable oxy genated organic compounds. A still further ob ject is to provide a'process whereby predeter mined carboxylic acids, ketones, alcohols, and/or the prior art frequently formed mixtures contain_ 85 organic peroxides having the same number of ing various percentages‘ of saturated and unsat_ carbon atoms per molecule as the starting ma- ' urated hydrocarbons, saturated and unsaturated terial may be produced in economical yields to aliphatic and aromatic aldehydes, ketones, lac the substantial exclusion of other products of tones, alcohols and other oxygenated compounds, oxidation which are normally formed when hy such as carbon dioxide. Furthermore, these var‘ (0 drocarbons are subjected to partial oxidation in ious oxygenated compounds formed during the accordance with the processes of the prior art. oxidation‘ of various hydrocarbons according to Another object is to provide a novel process for the teachings of the prior art usually contained the catalytic oxidation of alicyclic hydrocarbons varied numbers of carbon atoms per molecule due (including those having acyclic substituents) ‘to the carbon-to-carbon bond scission, as well as 45 and/or of their partially halogenated derivatives, to other side reactions such as polymerization, to produce high yields of alicyclic carboxylic condensation, and the like. acids, ketones, alcohols and/or organic peroxides, Although most of the oxygenated'organic com to the substantial exclusion of oxygenated com pounds formed as a result of the partial oxida pounds having a lesser number of carbon atoms tions of hydrocarbons according to the known 60 per molecule than present in the alicyclic comprocesses are generally more valuable than the pound subjected to treatment. Still other ob primary materials subjected to- the oxidation re- I jects of the present invention will become appar action, the subsequent fractionations of the re ent from the following description. The term action mixtures and the separate recovery of the “ketone” as employed herein and in the appended individual compounds therefrom are frequently 55 claims refers to organic compounds'containing 2,869,181 one or more ketonic carbonyl groups, and there fore includes diketones. It has now been discovered that the above and other objects may be attained by effecting the partial and ‘controlled oxidation in the presence of hydrogen bromide employed as a catalyst. taneous combustion or substantial decomposition of the carbon structure occurs. This upper tem perature limit will at least in part depend on the speci?c organic substance treated, as well as on the proportions thereof and of the oxygen and hydrogen bromide present in the vaporous mix ture subjected to the elevated temperatures. Gen More speci?cally stated, the invention resides in erally speaking, this upper temperature limit is the‘ controlled, non-explosive oxidation of alicy in the neighborhood of about 200° C. to 225° C. ciic hydrocarbons, particularly of saturated ali cyclic hydrocarbons, and of vtheir partially halo 10 However, some of the more ‘stable organic com pounds of the de?ned class may be heated to genated derivatives, in the presence of a catalyst gether with oxygen and hydrogen bromide to consisting of or comprising hydrogen bromide, ' or of a compound capable of yielding hydrogen bromide under the operating conditions. In one of its more speci?c embodiments the invention resides in the production of alicyclic carboxylic acids, ketones, alcohols and/or peroxides by the controlled oxidation of alicyclic hydrocarbons, es pecially saturated alicyclic hydrocarbons, or of products of their partial halo-substitution, this oxidation being effected by subjecting. the above higher temperatures, e. g. about 250° C., and ‘higher, particularly in the presence of inert dilu i5 ents, ‘without causing the mixture to decompose with the concurrent formation of high yields of carbon. In this connection it is to be noted that excessively high temperatures, even though they are below the explosive region, should be avoided 20 because of certain undesirable side reactions such ing material, in the presence of hydrogen bro as excessive conversion of hydrogen bromide to organic bromides. This in, itself is not detrimen tal because as stated, the organic bromides them selves may be treated in accordance with the 25 present invention to form bromide-free oxygen mide or a substance capable of yielding hydro ated organic compounds and the corresponding gen bromide under the operating conditions, and at temperatures and pressures which are below those capable of causing spontaneous combustion, portion of the hydrogen bromide is regenerated mentioned and hereinbelow more fully described class of alicyclic compounds to the action of oxy gen or of an oxygen-containing or oxygen-yield hydrogen bromide (so that in e?ect at least a and may be re-used). The excessive formation of and, therefore, resultant decomposition of the 30 organic bromides during the controlled oxidation carbon structure of the startingiorganic mate ofia given alicyclic hydrocarbon (or of its halo rial. genated‘derivative), however, is undesirable be The above-outlined invention is predicated on cause this decreases the catalyst concentration the discovery that the presence of hydrogen bro and may a?ect the yield or output of the desired mide during the oxidation of the de?ned class of 85 oxygenated product or products. As stated, the organic compounds controls the oxidation reac upper temperature limit is generally in the neigh tion so that oxidation occurs on the carbon atom borhood of about 200° C. to 225° C. However, or atoms to which a halogen atom would normally with shorter contact periods this temperature attach itself if the starting organic material were may be raised above the mentioned limit. Some subjected to a halo-substitution reaction. Fur 40 of the more readily oxidizable alicyclic compounds thermore, it has been found that the presence may be economically oxidized according to the of hydrogen bromide, besides retarding the ex present process at lower temperatures, e. g. be plosion or complete combustion of the organic .tween' about 150° C. and about 175° C. With a starting material, has the e?ect of inhiibting de further decrease in the operating temperature, composition of the carbon structure of such or the output of product per unit time will decrease, ganic starting materials, so that the resultant ‘ so that at temperatures of below about 100° C. oxygenated compounds contain the same num the controlled oxidation in the presence of the ber of carbon atoms per molecule as the starting hydrogen bromide, or substances capable of yield organic material. a ing it under the operating conditions, may be The following is a representative list of ali 50 come uneconomical. cyclic hydrocarbons (which term includes the al- - kylated derivatives thereof) which may be oxi dized'in accordance with the process of the pres ent invention: cyclopropane, cyclobutane, cyclo pentane.cyclohexane, methyl cyclopentane, meth yl cyciohexane, 1,2,4-trimethyl cyclohexane, 1,3,5 trimethyl cyclohexane, thujane, sabinene, carane, The reaction may be e?ected in the liquid or Vapor phase, or in a two-phase liquid-vapor sys tem. Since it is dif?cult to maintain a desirable relatively high oxygen concentration when the re action is conducted in the liquid phase, it is gen erally preferable to e?ect the oxidation accord ing to the present process in the vapor phase. Since some of the relatively higher boiling ali pinane, camphane, and the like and their homo logues. Also, the products of partial halo-substi tution of such alicyclic hydrocarbons, whether 60 cyclic hydrocarbons, which may or may not con tain halogenated substituents, cannot be effec such halo-substitution be in the ring or in ‘the tively maintained in the vapor phase and in alkyl chain or chains attached thereto, may be contact with sui?c‘ent concentrations of oxygen employed as the starting material. The process and of hydrogen bromide without causing spon of the present invention, however, is particular ly suitable for the controlled oxidation of the 65 taneous combustion, the oxidation of such com pounds may be readily e?ected in the presence lower homologues, and especially of the lower of inert diluents such as steam, nitrogen, carbon saturated homolo-gues, of these alicyclic com dioxide, and even methane, which latter is rela pounds. Obviously, mixtures of these and like tively stable at temperatures at which other men organic compounds may also be employed as the organic starting material. 70 tioned hydrocarbons, and their corresponding halogenated derivatives, may be oxidized ‘accord It was stated above that the slow (i. e. non ing to the invention. Of the above diluents, the explosive) controlled oxidation of the above-out use of steam is believed to be most advantageous lined class of organic compounds is effected in because the hydrogen bromide may then be re accordance with the present invention at tem peratures which are below those at which spon 75 moved from the reaction mixture as an overhead , r 3 2,869,181 rial subjected to oxidation, at various interme mix fraction in the form of its constant boiling ture of hydrogen bromide and water. Although the volumetric ratios of the organic starting material to the oxygen may vary within diate points along the reaction zone. Such op erationlmay be frequently desirable to control ‘ the operating conditions in the reaction zone. Generally, the contact time may vary within relatively wide limits and is at least in part de pendent on the other operating conditions such as speci?c starting material, the ratios thereof to the oxygen and/or the catalyst, the presence or absence of inert diluents, the operating tem peratures and pressures, etc. In a continuous relatively wide limits, it may be stated that satis- ' factory yields of the 'desired oxygenated prod uct or products can be obtained by using equi volumetric quantities thereof. An increase in the _ ratio of oxygen to the organic material in the treated mixture may increase the yield of the desired alicyclic carboxylic acids, organic per . systemit has'been found that satisfactory yields oxides and/or ketones. However, any undue in crease in this ratio is generally dangerous be of the desired alicyclic carboxylic acids, alcohols, : organic peroxides and/or ketones may be ob other hand, the use of oxygen-to-hydrocarbon 15 tained with contact periodsof between about one ratios which are considerably below equivolumet and about three minutes. ‘Nevertheless, shorter ric will lower the output of the desired product or longer contact times may also be employed. cause of excessive explosion hazards. On the‘ Instead of using pure or substantially pure oxygen per unit of space. This renders the proc-, oxygen for the oxidation in accordance with the ess less economical. Nevertheless, the process is 20 process of , the present invention it is also pos per unit of time because of the presence of less . still operable, and, in fact it must be noted that sible to employ oxygen-containing mixtures such a lowering of the oxygen-to-hydrocarbon or oxy-' gen-to-organic halide ratio may cause a faster consumption of oxygen per unit of time. It was as air, or even substances capable of yielding molecular oxygen under the operating condi tions. Also, although the examples presented stated above that satisfactory yields of the desired 25 hereinbelow are directed speci?cally to the use oxygenated products may be obtained when equi of hydrogen bromide .as the catalyst, the process volumetric mixtures of oxygen and of the speci of the present invention may also be realized ?ed organic starting vmaterial are subjected to by using substances capable of yielding hydrogen . the action of hydrogen bromide at the speci?ed bromide under the operating conditions em operating temperatures. Such mixtures usually 30 present no hazards in so far as explosions are The‘inventlon is illustrated by the following, concerned, the hydrogenbromide apparently act examples which are presented herein for the ing as an explosion retardant?or inhibitor. purpose of clarifying the, process of the present ployed. The amount of hydrogen bromide employed as ' . . ' ,. invention as well as the results and advantages the catalyst may also vary within relatively wide 35 derived therefrom. It is to be understood, how limits, although optimum amounts or percent _ ever, that these examples are merely illustrative ages may be readily determined for each indi- of the invention and should not be considered vidual starting material treated and for the as limiting the invention in any sense. ‘ speci?c operating conditions employed. - Gen Example I erally speaking, the' percentage of oxygen which 49 will react to form the-oxygenated products (other The reactor consisted of a, coil of glass tubing conditions being equal) will vary with the change having an internal diameter of about 15 mm, in the hydrogen bromide concentration in the and a volume of about 450 cc. This coil was im mixture subjected to treatment. When the hy mersed in an oil bath which permitted accurate‘ I drogen bromide concentration is varied from zero control of the reaction temperature. A preheated to about 20 per cent there is a proportional and vaporous mixture of cyclopentane, oxygen, ni noticeablechange in the percentage of. oxygen trogen and hydrogen bromide (which substances which reacts with the organic starting material. were employed in a volumetric ratio of 2:2:2:1, Increases in the volumetric or mol concentration of the hydrogen bromide above about 20%, how ever, do not have such a marked effect on the percentage of oxygenwhich will react. Nev ertheless, very high hydrogen bromide concen- trations will cause ‘excessive dilution and thus decrease the output of the desired product'or products. Such high concentrations should ' respectively) was then conveyed at substantially 5.0 atmospheric pressure through the above coil re ‘actor at such a rate that the residence'time was equal to about 3 minutes. The nitrogen was . employed for the purpose of maintaining the cyclopentane in the vapor state. The tempera 55 ture in the reactor was maintained at about 185° C. The e?luent reaction mixture was conveyed therefore be avoided for economic reasons. into an aqueous sodium bicarbonate solution to The oxidation in accordance with the present neutralize the hydrogen bromide.‘ The liquid process may be effected at atmospheric pressures, reaction product contained a major amount of although higher or lower pressures may also be 60 cyclopentanone, and it was found that between employed. In fact, it is generally preferable to employ super-atmospheric pressures because about 60% and about 70% of the introduced oiwgen reacted to produce oxygenated products. It' was also found that no reaction occurred when cyclopentane and oxygen were subjected, under more of the mixture subjected to treatment may be present in or conveyed through a given unit 65 of reaction space per unit time. the above-mentioned operating conditions, to a The invention may be executed in a batch, temperature of‘ 185° C. in the absence of hy intermittent or continuous manner. When op drogen bromide. ' erating in a continuous system, all of the react Example If ants, as well as the diluents, if diluents are used, A vaporous mixture consisting of 2 parts by and the catalyst may be ?rst mixed together 70 and the mixture may then be conveyed through volume of vcyclohexane, 2 parts by volume of oxygen, 2 parts by volume'of nitrogen and 1 the whole length of the reaction zone. In the part by volume of hydrogen bromide was con alternative, it is possible to introduce at least a portion of the catalyst and/or of one or both of veyed through the same reactor as that used in the reactants, i. e. oxygen and the organic mate 75 Example I. The residence time was equal to 4 2,869,181 about 6 minutes, but the reaction temperature was raised to about 222° C. The e?‘luent product was passed through and collected in water, and the liquid organic product thus produced was found to contain an appreciable amount of cyclohexanone. Also, diketones were found to be present in this reaction product. About 45% of the introduced oxygen reacted. 6. A process for the production of ketones which comprises subjecting a vaporous mixture of cyclohexane and oxygen to the action of hy drogen bromide, at a temperature of between about 100° C. and the temperature at which spontaneous combustion occurs, e?ecting the re action for a period of time su?icient to cause the controlled catalytic oxidation of the cyclo The reason for the relatively high temperature , hexane, and recovering the ‘ketones from the employed in the above run is because cyclo 10 reaction mixture thus formed. ' hexane is quite resistant to oxidation. For in 7. A process for the production of oxygenated ' stance, when the above reaction was repeated organic products which comprises subjecting a at a temperature of about 180° C. and with a mixture of cyclohexane, oxygen and hydrogen residence time of about '3 minutes, substantially bromide to the action of an elevated tempera no oxygen was consumed. In fact, even at a 15 ture of between‘ about 100° C. and the tempera temperature of about 196° C. and a residence time ture at which spontaneous combustion occurs, of about 3 minutes, the reaction was only 25% . and e?ecting the reaction for a period of time complete. On the other hand, at a temperature of about 227° C. there was considerable decom su?icient to cause the controlled catalytic oxida tion of the cyclohexane. ’ position of the carbon structure of the cyclo 20 8. In a process for the controlled oxidation of hexane, and large amounts of carbon dioxide, alicyclic hydrocarbons, the steps of subjecting carbon monoxide and lower hydrocarbons were found in the reaction product. vapors of a saturated alicyclic hydrocarbon to ‘ the action of oxygen in the presence of hydrogen As in the case with cyclopentane, no oxidation bromide and effecting the reaction at a tempera of cyclohexane was noticed when the reaction 25 ture of between about 100° C. and the tempera was attempted in the absence of hydrogen bromide even at temperatures considerably high er than those employed above for the oxidation in the presence of this catalyst. We claim as our invention: _ . ' tu‘re at which spontaneous combustion and the resultant decomposition of the organic com- _ pound will occur. . 9. The process according to claim 8 wherein 30 the saturated alicyclic hydrocarbon and oxygen are employed in substantially equivolumetric‘ 1. A process for the production of cyclopen tanone which comprises subjecting a vaporous proportions. mixture containing cyclopentane and oxygen at 10. In a process for the controlled oxidation substantially atmospheric pressure and at a tem of alicyclic hydrocarbons, the steps of subject perature of above about 100° C. but below the 35 ing vapors of saturated alicyclic hydrocarbon to temperature at which spontaneous combustion occurs, to the action of hydrogen bromide em ployed in an amount in excess of about 20 mol the'action of oxygen in the presence of hydrogen bromide and at a temperature of between about 100° C. and the temperature at which spontane percent, e?ecting the reaction for a period of ous combustion and the resultant decomposition time su?icient to cause the controlled catalytic 40 of the organic compound to carbon will occur. oxidation of the cyclopentane, and recovering and continuing said reaction for a period of time cyclopentanone from the- reaction mixture thus su?‘icient to effect a substantial reaction between formed. said saturated alicyclic hydrocarbon and the 2. The process according to claim 1, wherein oxygen. an inert diluent is employed to maintain the 45 11. In a process for the controlled oxidation cyclopentane in the vaporous state. of organic compounds, the step of subjecting va 3. A process for the production of cyclopen pors of an organic compound selected from the tanone which comprises subjecting a vaporous group consisting of alicyclic hydrocarbons and mixture containing cyclopentane and oxygen to of their products of partial halogenation to the 50 the action of hydrogen bromide at an elevated action of oxygen in the presence of hydrogen temperature which is below the spontaneous . bromide and at a temperature of between about combustion temperature of the mixture, effect 100° C. and the temperature at which spontane ing said reaction for a period of time su?icient ous combustion and the resultant decomposition to cause the controlled catalytic oxidation of the of the organic compound to carbon will occur. cyclopentane, and recovering cyclopentanone 55 12. In a process for the controlled oxidation of from the reaction mixture thus formed. organic compounds, the step of subjecting an 4. A process for the production of cyclohex organic compound selected from the group con ' anone which comprises subjecting a substantially sisting 'of alicyclic hydrocarbons and of their equivolumetric gaseous mixture of cyclohexane products of partial halogenation to the action and oxygen at substantially atmospheric pressure 60 of oxygen and of hydrogen bromide at a temper and at an elevated temperature of below about ature of between about 100° C. and the tempera 200° C. to the action of hydrogen bromide cata ture at which spontaneous combustion and the _ lyst for a period of time su?icient to effect the resultant decomposition of the carbon structure controlled catalytic oxidation of the cyclohexane, of the starting organic compound occurs. and recovering cyclohexanone from the reaction 65 mixture thus formed. FREDERICK F. RUST. 5. The process according to claim 4 wherein WILLIAM E. VAUGHAN. hydrogen bromide is employed in an [amount which is in excess of about 20 mol percent.