||||||||||||||| 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 amine 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 oxygen 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 solvent 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 aldehydes 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 alkyl 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 pyridine 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 solubility 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.