||||||||||||||| USOO5122308A United States Patent 19 11) Patent Number: 5,122,308 Dutta et al. 45 Date of Patent: k Jun. 16, 1992

(54) PROCESS FOR THE OXIDATION OF 3,997.578 12/1976 Sheng ...... 260/43 ALCOHOLS TO ACIDS 4,015,060 3/1977 Karayannis et al...... 526/14 4,096, 196 6/1978 Boudakian ...... 260/650 F 75 Inventors: Tamal K. Dutta; Lynn H. Slaugh, 4,207.30 6/1980 Langford ...... 424/150 both of Houston, Tex. 4,225,694 9/1980 Dalton et al...... 56.2/506 73 Assignee: Shell Oil Company, Houston, Tex. 4,996,007 2/1991 Caro et al...... 562/538 * Notice: The portion of the term of this patent Primary Examiner-Jose G. Dees subsequent to Jun. 16, 2009 has been Assistant Examiner-Deborah D. Carr disclaimed. Attorney, Agent, or Firm-Pamela J. McCollough 21 Appl. No.: 552,392 57 ABS CT 22 Filed Jill, 13, 1990 The instant invention relates to a process for the oxida 18: l. 3, tion of primary alcohols to the corresponding acids,

51) int. Cl...... C09F 7/02 which comprises contacting and thereby reacting an 52 U.S. Cl. ... as - a 554/135; 562/512.2; alcohol with a tertiary oxide compound at ele 562/538; 562/540, 554/136; 554/207 vated temperatures in the presence of a homogeneous 58) Field of Search ...... 260/413, 406, 410.9 R; oxidation catalyst comprising a Group VIII metal and a 562/538, 512.8, 540, 560/239 promoter comprising a quaternary ammonium bromide, (56) References Cited and subsequently separating out acids from the reaction mixture product. U.S. PATENT DOCUMENTS 3,818,060 6/1974 Forster et al...... 260/43 15 Claims, No Drawings 5,122,308 1. 2 mercially prepared, for instance, by hydroformylation PROCESS FOR THE OXIDATION OF ALCOHOLS of olefins or by reduction of naturally occurring fatty TO ACIDS esters. Specific examples of commercially available alkanol mixtures in the C9 to Cls range are the NEO FIELD OF THE INVENTION DOL detergent alcohols, trademark of and manufac This invention relates to an improved process for the tured by Shell Chemical Company. e.g., the products oxidation of alcohols to acids using a tertiary amine identified as NEODOL 91 alcohols (predominantly in oxide activator in the presence of a homogene the Co. to C11 range), NEODOL 23 alcohols (predomi ous oxidation catalyst and a promoter. nantly in the C12 to C13 range), NEODOL 25 alcohols 10 (predominantly in the C12 to C15 range) and NEODOL BACKGROUND OF THE INVENTION 45 alcohols (predominantly in the C4 to C15 range) Alcohols, particularly primary alcohols, are readily The oxidant in the process of the instant invention is available in large commercial quantities. Processes to a tertiary amine oxide compound. The tertiary amine convert primary alcohols to acids fill a useful need in oxide oxidant reacts with a primary alcohol at tempera the industrial world. Acids have been used commer 5 tures in the range of from about 40 C. to about 200 C. cially for the manufacture of synthetic lubricants and and converts it to primarily acids, although some aide Soaps. hydes and esters are also formed. The process of the In the past, various processes have been developed instant invention can also be carried out in the presence for the production of acids. It has been proposed to treat of an additional oxidant such as oxygen or air, or in an various alcohols with an oxidizing agent in the presence 20 inert atmosphere. of a catalyst, such as ruthenium and a to pro The tertiary amine oxides suitable for use in the pro duce the corresponding acids. Such processes, how cess of the instant invention are those having the gen ever, have generally produced high yields of eral formula: and rather low yields of acids. Since processes that produce high yields of acids are particularly desired, it is an object of this invention to provide a process for the : conversion of alcohols to the corresponding carboxylic R- -Geo acids having a high selectivity to acids. It has been found that high selectivity to acids can be Rs achieved by a process for oxidizing alcohols to acids 30 wherein R1 and R2 are groups, preferably methyl which comprises reacting an alcohol with a tertiary groups or ethyl groups, which are the same or different, amine oxide oxidant at elevated temperatures in the and R3 is a phenyl group or alkyl substituted phenyl presence of an oxidation catalyst comprising a Group group, a benzyl group or an alkyl substituted benzyl VIII metal and a promoter comprising a quaternary group, a cyclohexyl group or an alkyl substituted cyclo ammonium bromide and thereafter separating out the 35 hexyl group, a cyclohexanemethyl group or an alkyl acids formed from the reaction product mixture. substituted cyclohexanemethyl group; or wherein R1 is SUMMARY OF THE INVENTION an alkyl group, preferably a methyl group or an ethyl The instant invention relates to an improved process group, and N, R2 and R3 together form part of a satu for the oxidation of primary alcohols to acids, which rated or unsaturated heterocyclic group, or where N, comprises contacting and thereby reacting at elevated R, R2 and R3 together form part of a saturated or unsat temperatures an alcohol with a tertiary amine oxide urated heterocyclic group or bridged heterocyclic compounds in the presence of an oxidation catalyst group. comprising a Group VIII metal and a promoter com When N, R2 and R3, or N, R, R2 and R3 form a prising a quaternary ammonium bromide, and subse 45 heterocyclic or bridged heterocyclic group, a second quently separating out acids from the reaction mixture tertiary amine oxide group can also optionally be in product. cluded in the heterocyclic or bridged heterocyclic group. DETAILED DESCRIPTION OF THE Examples of suitable tertiary amine oxides include: INVENTION 50 N,N-dimethyl benzylamine oxide; N,N-diethyl benzyl The instant process comprises reacting a primary amine oxide; N-methyl N-ethyl benzylanine oxide; alcohol with a tertiary amine oxide oxidant at elevated N-oxide; a-picoline N-oxide; (3-picoline N temperatures in the presence of an oxidation catalyst oxide; y-picoline N-oxide; pyrazine N-oxide; pyrazine comprising a Group VIII metal and a promoter com N,N'-dioxide; N-methyl piperidine N-oxide; N-ethyl prising a quaternary ammonium bromide. 55 piperidine N-oxide; N-methyl piperazine N-oxide; Alcohols typically used in the process of the present N,N'-dimethyl piperazine N,N'-dioxide; triethylenedi invention are primary mono-hydric aliphatic alcohols. amine N-oxide; triethylenedianine N,N'-dioxide: N The aliphatic alcohols preferably have from one to methylmorpholine N-oxide; N-ethyl morpholine N about 30 carbon atoms, with C6 to C24 alcohols consid oxide; quinoline N-oxide; N-methyl pyrrole N-oxide; ered more preferred and C8 to C20 alcohols considered N-methyl pyrrolidine N-oxide; N,N-dimethyl cyclohex most preferred. As a general rule, the aliphatic alcohols ylamine N-oxide; N,N-dimethyl cylcohexanemethyla are primarily of straight-chain structure. Specific exam mine N-oxide; and N,N-dimethylaniline N-oxide. In a pies of primary straight-chain monohydric aliphatic preferred embodiment, the tertiary amine oxide oxidant alcohols include ethanol, hexanol, octanol, dodecanol, is N-methylmorpholine N-oxide. pentadecanol and octadecanol. 65 The tertiary amine oxide oxidant should be present in Mixtures of alcohols are also suitable for purposes of an amount sufficient to obtain complete oxidation of the this invention. Mixtures of higher (e.g., Cs to C20) alcohol to an acid. Typically, the tertiary amine oxide is monohydric aliphatic alcohols are known to be com used in an amount sufficient to supply between about 5, 122,308 3 4. 0.4 and about 1.8 mole equivalents of oxygen per mole als, such as alumina raschig rings or berl saddles, in the of alcohol. presence of air or nitrogen and in the presence of the The tertiary amine oxide may be utilized in a one homogeneous catalyst. Other continuous reactor con phase hydrocarbon system or in a two-phase hydrocar figurations will be readily apparent to one skilled in the bon/water system. The of the tertiary amine at. oxide in the aqueous phase will depend on the presence Batch reactors, such as autoclaves, are also suitable. of water solubilizing substituents on the tertiary amine For example, the primary alcohol, an aqueous solution oxide, such as, for example, alkylsulfonates, arylsulfon of the tertiary amine oxide and the homogeneous oxida ates and the like. The use of a two phase system can tion catalyst can be loaded into an autoclave, the auto have certain processing advantages, particularly when O clave sealed and charged with an oxygen-containing the tertiary amine oxide is more soluble in the aqueous gas, heated to a desired reaction temperature and the phase than in the hydrocarbon phase and the alcohol reaction allowed to proceed. and the product acids, aldehydes and esters are more The process in the instant invention is carried out at soluble in the hydrocarbon phase than in the aqueous elevated temperatures. The reaction temperature is phase. In the latter case, the organic phase contains 15 typically in the range of from about 40 C. to 200 C., unreacted alcohol and the major portion of the product preferably from about 50° C. to about 100° C. and more acids, aldehydes and esters and the aqueous phase con preferably, from about 55° C. to about 65° C. While the tains the tertiary amine oxide and a residual amount of reaction will proceed at lower temperatures, tempera product acids, aldehydes and esters, which will allow a tures greater than about 40 C, preferably greater than ready separation of product acids, aldehydes and esters about 50 C., are necessary in order to obtain a high and reactant alcohols from the oxygen activator. Long selectivity to acids. Reaction pressures for the instant chain alcohols are suitably processed with this two process are not critical and will typically range from phase system. about atmospheric to about 150 atmospheres, preferably In addition to the use of water as a solvent as indi from about 35 atmospheres to about 100 atmospheres cated above, other organic can be utilized, such 25 although higher and lower pressures can be utilized. as alkanes, aromatics, such as benzene, toluene and For the two-phase system, after reaction there will be xylene; alkanes, halo-substituted aromatics, amides, a hydrocarbon phase containing unreacted alcohol and , ethers, . ketones, etc.. Solvents se the major portion of the product acids, aldehydes and lected should not react with either the reactant alcohol esters. The hydrocarbon phase may be diluted with an or the product acids. 30 inert organic solvent, such as an alkane. There will also The catalyst utilized in accordance with the present be an aqueous phase containing the oxidized tertiary invention is homogeneous oxidation catalyst compris amine oxide, promoter, a small amount of alcohol and ing a Group VIII metal. With the catalyst being homo product acids, aldehydes and esters, and the homogene geneous, it is preferred that a two phase hydrocarbon/- ous oxidation catalyst. The hydrocarbon phase is pro water system be utilized and that the catalyst be soluble 35 cessed, for example, by distillation, to recover the prod in the aqueous phase in order to facilitate separation of uct acids, aldehydes and esters. The product acids, alde the catalyst from the product acids, aldehydes and es hydes and esters may then be distilled to recover the ters. Preferably, the Group VIII metal is selected from product acids. The aqueous phase may also be pro the group consisting of ruthenium, rhodium, platinun, cessed to remove any residual alcohol or acids/al palladium and mixtures thereof. In a particularly pre dehydes/esters, say by liquid-liquid extraction with an ferred embodiment, the Group VIII metal is ruthenium. organic solvent. The amount of catalyst utilized in the present process is For the single phase hydrocarbon system, after reac generally in amounts the range of from about 0.1 per tion, the hydrocarbon phase is processed by conven cent by weight to about 15 percent by weight, basis tional techniques such as distillation, liquid-liquid ex substrate alcohol and preferably, from about 1 percent 45 traction with water, filtration, etc; in order to separate by weight to about 8 percent by weight. the product acids, aldehydes and esters, the oxidized The process of the instant invention is also carried out tertiary amine oxide, unreacted alcohol and any oxida in the presence of a promoter. A promoter comprising a tion catalyst and promoter. quaternary ammonium bromide is utilized. Preferably, The ranges and limitations provided in the instant the promoter is quaternary alkylammonium bromide 50 specification and claims are those which are believed to wherein the alkyl moieties have carbon numbers rang particularly point out and distinctly claim the instant ing from 1 to about 20, Higher alkylannonium bro invention. It is, however, understood that other ranges mides are preferred. Suitable quaternary alkylam and limitations that perform substantially the same func moniun bromides include didecyldinnethylammonium tion in substantially the same way to obtain the same or bromide, tetrapropylammonium bromide, cetylidine 55 substantially the same result are intended to be within thylethylammonium bromide and cetyltrimethylam the scope of the instant invention as defined by the monium bromide, with didecyldimethylammonium bro instant specification and claims. mide being preferred. The promoter is typically used in The invention will be described by the following amounts ranging between about 1 percent by weight examples which are provided for illustrative purposes and about 100 percent by weight, basis substrate alco and are not to be construed as limiting the invention. hol, preferably, between about 10 percent by weight and about 80 percent by weight, and more preferably, EXPERMENTAL PROCEOURE between about 50 percent by weight and about 60 per In a typical experiment a round bottom flask (50 ml cent by weight. capacity), equipped with a stir bar and a nitrogen (l The alcohol oxidation reaction may be carried out in 65 atmosphere) line capping the neck, was charged in a dry a batch reactor or in a continuous flow reactor. For box (pre-purified nitrogen-gas purged) with 10.0 grams example, the alcohol and the tertiary amine oxide oxi of solvent (for example, acetone); 1.56 grams (8.37 dant may be trickled over a bed of inert support materi mmois) of alcohol substrate (for example, 1-dodecanol); 5,122,308 5 6 0.50 grams of dodecane; 0.98 grams (8.37 mmols) of 1. A process for the oxidation of primary alcohols to tertiary amine oxide (for example, N-methyl morpho the corresponding acids, which comprises contacting line-N-oxide); and 0.13 grams of RuOl3XH2O catalyst. and thereby reacting an alcohol with a tertiary amine In the experiments containing a promoter, 0.94 grams (2 oxide compound at elevated temperatures in the pres mnols) of quaternary annonium bromide (for example, ence of a homogeneous oxidation catalyst comprising a didecyldimethylammonium bromide) was added. Group VIII metal and a promoter comprising a quater The round botton flask was then removed from the nary ammonium bromide, and subsequently separating dry box and magnetically stirred and charged with a out acids from the reaction mixture product. continuous flow of l atmosphere of nitrogen. The flask 2. The process of claim 1 wherein the oxidation is O carried out at a temperature ranging from about 40 C. was then heated to 65 C. (internal temperature) while to about 200 C. maintaining rapid mechanical for a period of about 2 3. The process of claim 2 wherein the oxidation is hours until no further pressure drop occurred. The hot carried out at a temperature ranging from about 50 C. flask was then allowed to cool down to room tempera to about 100 C. tle. 15 4. The process of claim 1 wherein said alcohol is a The solution of the crude reaction product mixture primary mono-hydric aliphatic alcohols. was filtered through glass wool and then analyzed by 5. The process of claim 4 wherein said alcohol con gas liquid chromatography (GLC) using a Hewlett-Pac tains from one to about 30 carbon atoms. kard 5890A gas chromatograph fitted with a hydrogen 6. The process of claim 5 wherein said alcohol con flane ionization detector and a data processor. The 20 tains from about 8 about 20 carbon atoms. peaks of the chromatograms were identified qualita 7. The process of claim 1 wherein said Group VIII tively by comparison of their retention times with those metal is selected from the group consisting of ruthe of standards and by GC/MS technique. The quantita nium, rhodium, platinum, palladium and mixtures tive estimation of the percent composition of the reac thereof. tion mixture was obtained from the integration of the 25 8. The process of claim 7 wherein said Group VIII areas of the peaks in the chromatograms. metal is ruthenium. 9. The process of claim 8 wherein said catalyst is ILLUSTRATIVE EMBODIMENT I ruthenium chloride. Following the experimental procedure described 10. The process of claim 1 wherein the promoter is a above experiments were carried out in the presence and 30 quaternary alkylamnonium bromide. the absence of a promoter. The experimental conditions 11. The process of claim 10 wherein the quaternary and the results are shown in Table 1 below. alkyl ammonium bromide is didecyldimethylammonium bromide. TABLE 1 12. The process of claim wherein the tertiary amine Oxidation of Alcohol:Effect of Promoter 35 oxide compound is N-methylmorpholine N-oxide. Pro- Conver- Selectivity. % 13. A process for the oxidation of primary alcohols to Substrate noter sion, % C12-Acid 12- C24-Ester the corresponding acids, which comprises contacting DC. ODAB 5.88 57.72 19.0 O.O and thereby reacting an alcohol with a tertiary amine decanol oxide compound at a temperature in the range of from -Do- None 3.65 O.O. OO.O 0.0 40 about 50° C. to about 100° C. in the presence of a homo decanol geneous oxidation catalyst comprising ruthenium and a Conditions promoter comprising a quaternary alkylammonium Solvent Acetone, 10.0 grams bromide, and subsequently separating out acids from Promoter DDAB is Didecyldimethylammonium bromide, 0.94 g (2 minols) the reaction mixture product. Catalyst RuCls > HO. O. 13 g (0.63 mmols) 45 14. The process of claim 13 wherein the quaternary Oxidant N-methylnorpholine-N-oxide (0.98 g. alkylammonium bromide is didecyldimethylammonium 8.37 nmols) bromide. Oxidation Temp. 65 C. 15. The process of claim 13 wherein the tertiary Oxidation Reaction Tine 2 hrs. amine oxide compound is N-methylmorpholine N 50 oxide. What is claimed is: Six k

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