United States Patent (19) 11) Patent Number: 5,047,582 Brotherton et al. (45) Date of Patent: Sep. 10, 1991 (54) PROCESS FOR THE OXIDATION OF A TETRAHYDROPHTHALIC ACID 75 Inventors: David L. Brotherton; Kwok W. Fung, COOH both of Easley, S.C.

73) Assignee: Ortec, Inc., Easley, S.C. COOH (21) Appl. No.: 415,890 R 22 Filed: Oct. 2, 1989 51) Int. Cl...... CO7C 51/285 wherein R and R' independently are H, alkyl, aryl or 52 U.S. Cl...... 562/508; 560/125; halo, to a glycol of the formula 560/126; 560/190; 562/507; 562/509; 562/525; 562/590 R 58) Field of Search ...... 562/469, 508, 509, 525, HO COOH 562/590, 507; 560/125, 126, 190

(56) References Cited HO COOH U.S. PATENT DOCUMENTS R" 2,203,628 6/1940 Hopff et al...... 562/524 3,284,492 l 1/1966 Fremery et al...... 562/48 3,535,367 10/1970 Inoue et al...... 560/26 comprises treating the tetrahydro compound with hy 3,915,997 0/1975 Ladd ...... 562/523 X drogen peroxide at an elevated temperature in the ab 4,305,824 12/1981 Uemura et al...... 20/500.29 sence of a catalyst. 4,331,608 5/1982 Kawamoto et al...... 260/406 The thus-formed glycol can be further oxidized in a 4,391,945 5/1983 Mashio et al...... 524/6OO butanetetracarboxylic acid of the formula 4,532,079 7/1985 Venturello et al...... 260/413 4,820,307 4/1989 Welch et al...... 8/20 4,833,272 5/1989 Nakazawa et al...... 562/523 RCHCOOH OTHER PUBLICATIONS CHCOOH Venturello et al., J. Org. Chen., vol. 51 (1986), pp. CHCOOH 1599-601. RCHCOOH Franz et al., Chem. and Ind (2/25/61), pp. 250-251. Franz et al., J. Org. Chem., vol. 30 (1965), pp. with hydrogen peroxide in the presence of a catalyst 1488-1491. selected from the group consisting of a manganese salt, Primary Examiner-Jose G. Dees an iron salt, a chromium salt, a cerium salt, a persulfate, Assistant Examiner-Vera C. Clarke a perborate, a silicate, tungstic acid or an ammonium or Attorney, Agent, or Firm-Cort Flint alkali metal salt or heteropolyacid thereof, or molybdic acid or an ammonium or alkali metal Salt or 57 ABSTRACT heteropolyacid thereof. A process for oxidation of a tetrahydro compound of the formula 20 Claims, 4 Drawing Sheets

U.S. Patent Sep. 10, 1991 Sheet 2 of 4 5,047,582 Fig.2 SODIUMTUNGSTATE CATALYZED OXDATION (12 Hours, 25 min.)

CH2COOH HCOOH CHCOOH CH2COOH

PEAK TIME 1.32 2 148 3 2.03 4 3.30 5 3.88 6 6.33

---- 1.32 3.88 6.33 TIME (min) U.S. Patent Sep. 10, 1991 Sheet 3 of 4 5,047,582

Fig.3a Fig. 3b PRIOR ART

EXAMPLE 4 Na2 WO4CATALYST

PEAK TIME PEAKTIME 1 4 1 143 2 2.84 2 2.85 3 337 3 337 4 5.4 4 5.6 5 794 143 537 4, 33754 2.85 5.6 2.84 TIME (min) TIME (min) U.S. Patent Sep. 10, 1991 Sheet 4 of 4 5,047,582

Fig. 4d Fig.4b PRIOR ART

EXAMPLE 5 PHOSPHOTUNGSTIC ACID CATALYST

PEAK TIME 42 2 3.05 3 3.52 PEAK TIME 4 5.8 1 40 5 7.2 2 337 6 9.68 3 5.85

3.05 TIME (min) TIME (min) 5,047,582 1. 2 hydrogen peroxide in the presence of a metal-contain PROCESS FOR THE OXIDATION OF A ing catalyst. Advantages of the process include better TETRAHYDROPHTHALIC ACID control over an exothermic process, than heretofore, and production of a cleaner reaction product. DESCRIPTION DISCLOSURE OF INVENTION 1. Technical Field This invention relates to a process for the non In one aspect, this invention relates to a process for catalytic oxidation of tetrahydrophthalic acids with oxidation of a tetrahydro compound of the formula hydrogen peroxide to 4,5-dihydroxyhexahydrophthalic 10 acids. Further catalytic oxidation of the intermediate R 4,5-dihydroxyhexahydro compounds with hydrogen peroxide yields butane-1,2,3,4-tetracarboxylic acids. COOH Butanetetracarboxylic acids are used in the prepara tion of cellulosic reverse osmosis membranes, as pro COOH posed by Uemura et al. (U.S. Pat. No. 4,305,824); for 15 chelate resins, as proposed by Mashio et al. (U.S. Pat. R" No. 4,391,945) and for durable-press finishing of cotton textiles, as proposed by Welch et al. (U.S. Pat. No. 4,820,307). It is, therefore, apparent that improved R 20 methods for synthesizing butanetetracarboxylic acids COOH are of interest. 2. Background Art Nakazawa et al. (U.S. Pat. No. 4,833,272), herein incorporated by reference, have proposed a process for COOH preparing polycarboxylic acids by subjecting a Diel 25 R" sAlder adduct of maleic anhydride and a diene to oxida tion with hydrogen peroxide in the presence of a cata wherein R and R', are independently H, alkyl, aryl or lyst selected from tungstic acid, molybdic acid or halo, to a glycol of the formula heteropolyacids thereof. Venturello et al. (U.S. Pat. No. 4,543,079) have pro 30 R posed oxidative cleavage of olefins or vicinal dihydroxy compounds by treatment with hydrogen peroxide in a HO COOH biphasic aqueous liquid/organic liquid, in the presence of a catalyst. Catalysts include quaternary HO COOH ammonium, phosphonium, arsonium or stibonium com 35 pounds. A mechanism for the reaction is presented by R Venturello et al., J. Org. Chem., vol. 51 (1986), pages 1599-1601. comprising treating the tetrahydro compound with Fremery et al., in U.S. Pat. No. 3,284,492, have pro hydrogen peroxide at an elevated temperature in the posed preparing carboxylic acids by ozonization of 40 absence of a catalyst. - - - olefinic bonds in an emulsion containing hydrogen per In another aspect, the invention relates to a process . for further oxidation of the thus-formed glycol to a Kawamoto et al. (U.S. Pat. No. 4,331,608) have re butanetetracarboxylic acid of the formula cited a liquid phase catalytic process for co-oxidizing unsaturated compounds, including unsaturated alicyclic 45 RCHCOOH compounds, in which oxygen and an aldehyde are pres ent, along with a ruthenium catalyst. CHCOOH Inoue et al. (U.S. Pat. No. 3,535,367) have recited a CHCOOH process for preparing 4-hydroxycyclohexanecarboxylic R"CHCOOH acids by treating a cyclohexenecarboxylic acid with 50 sulfuric acid and hydrolyzing a resulting intermediate. The oxidation of tetrahydrophthalic acid or anhy with hydrogen peroxide in the presence of a catalyst dride to butanetetracarboxylic acid, with nitric acid, selected from the group consisting of a manganese salt, generally in the presnece of a vanadium catalyst, has an iron salt, a chromium salt, a cerium salt, a perborate, been investigated by: 55 a persulfate, a silicate, tungstic acid or an ammonium or Hopff et al., U.S. Pat. No. 2,203,628 alkali metal salt or heteropolyacid thereof, or molybdic Ladd, U.S. Pat. No. 3,915,997 acid or an ammonium or alkali metal salt or Johnson, GB Patent 510,638 heteropolyacid thereof. Franz et al., Chem. and Ind., (London), Feb. 25, 1961, DETAILED DESCRIPTION pages 250-251 Franz et al., J. Org. Chem., vol. 30 (1965), pages The starting materials used to prepare cyclic vicinal 1488-1491. glycol intermediates of this invention are Diels-Alder It is an object of this invention to provide a two-step adducts of maleic acid, maleic anhydride, or fumaric process for the preparation of butanetetracarboxylic acid and a 1,3-diene. The diene may be unsubstituted or acids, in which a tetrahydrophthalic acid is oxidized 65 may be substituted in the i- and/or 4-positions. The l with aqueous hydrogen peroxide to a corresponding or 4-substituent may be selected from alkyl, aryl or halo 4,5-dihydroxyhexahydrophthalic compound, which is substituents, of which methyl, ethyl, butyl, hexyl, 2 further oxidized to a butanetetracarboxylic acid with ethylhexyl, dodecyl, isostearyl, phenyl, tolyl, chloro 5,047,582 3 4. phenyl, alpha- or beta-naphthyl, chloro-, bromo- and rates, persulfates, silicates, tungstic acid or an ammo iodo- are representative. The substituents represented nium or alkali metal salt or heteropolyacid thereof, or by R and R' are therefore selected from alkyl of 1-18 molybdic acid or an ammonium or alkali metal salt or carbon atoms, mono- or bicyclic-aryl of up to 10 car heteropolyacid thereof. bon atoms or halo. When the desired product from Manganese salts include, but are not limited to the further oxidation of the intermediate glycol is butanetet chloride, bromide, iodide, nitrate, sulfate, acetate, ben racarboxylic acid, the adduct from butadiene-1,3 zoate or oxalate as well as Salts of higher oxidation (R=R's H) will be employed. states, including potassium permanaganate. Preferably It will be understood that maleic acid, maleic anhy the manganese salt is a salt of Mn(II), of which manga dride and fumaric acid include substituted derivatives, 10 nous chloride is particularly preferred. such as methylmaleic acid. Iron salts include, but are not limited to, ferrous or The non-catalytic oxidation of a tetrahydrophthalic ferric chloride, bromide, iodide, nitate, sulfate, oxalate, acid or anhydride is carried out with aqueous hydrogen acetate, etc. Preferably, the iron salt is of Fe(II), of peroxide at an elevated temperature. When a tetrahy which ferrous sulfate is most preferred. drophthalic anhydride is the starting material, it is pre 15 ferred to first hydrolyze the anhydride to a correspond Tungstic acid means “WO3' or "H2WO4'. A pre ing phthalic acid by heating with water at an elevated ferred salt catalyst is , which is repre temperature. Preferably, this hydrolysis will be carried sented by the formula Na2WO4. Usually sodium tung out at a temperature close to boiling, most preferably at state is used in the form of a dihydrate. 80-100° C. Even if a tetrahydrophthalic anhydride is Chromium salts include water soluble species of vari not subjected to hydrolysis prior to oxidation to a vici ous valence states of chromium, of which dichromate nal glycol, it will be appreciated that hydrolysis to a species are preferred. A most preferred chromium salt corresponding diacid would occur under the reaction catalyst is potassium dichromate, represented by the conditions used. formula K2Cr2O7. The oxidation of a tetrahydrophthalic acid/anhy 25 Cerium salts include those having ammonium func dride with hydrogen peroxide is carried out in an aque tions, particularly cerium (IV) ammonium salts, such as ous medium in the absence of an organic solvent. Tem (NH4)2Ce(SO4)3. 2 H2O or (NH4)2Ce(NO3)6.4H2O. peratures above about 50° C. are contemplated for the The sulfate salt is a preferred catalyst. oxidation of a tetrahydrophthalic acid or anhydride to a Perborates include species such as Na2B4O7, Na3. corresponding glycol. In order to achieve a reasonably 30 BO3.H2O and NaBO2.3 H2O. A preferred species for fast reaction, it is preferred to carry out this oxidation at the purposes of this invention is Na2B4O7. 70-100° C., most preferably at 80°-90° C. It has been Persulfates are salts of peroxydisulfuric acid, of found that substantial conversion of tetrahydrophthalic which the disodium and diammonium salts are represen starting material to glycol occurs within 3-4 hours at tative. The disodium salt (Na2S2O3) is preferred, these temperatures. The time required for conversion of 35 Silicates useful as catalysts in the process of this in tetrahydrophthalic compound to glycol can be deter vention include, but are not limited to, potassium meta mined by routine procedures, for example, HPLC. For silicate, potassium tetrasilicate, sodium metasilicate, mation of the intermediate glycol is demonstrated by sodium orthosilicate and sodium tetrasilicate. A pre HPLC. The peak corresponding to the intermediate ferred catalyst is sodium metasilicate (Na2SiO3) or its glycol is, for example, the peak at 3.27 min retention pentahydrate. time on FIG. 1. The product was also identified by its A heteropolyacid of tungsten is a polyacid compound 13C NMR spectrum. obtained from tungstic acid and at least one other oxy The amount of hydrogen peroxide required for the acid. Other hetero-atoms in heteropolyacids of tungsten intermediate conversion is 1-2.6 moles of hydrogen include P, AS, Si, Ti, Co, Fe, B, V, Be, I, Ni, Ga, etc. peroxide per mole of olefinic bond in the tetrahydroph 45 Heteropolyacids of tungsten therefore include thalic starting material. Most preferably, 1.8-2.5 moles H3PW12O40), H3AsW12O40), HsBW12O40), etc., as of hydrogen peroxide are used per mole of tetrahy disclosed Nakazawa et al. 272, supra. A preferred het drophthalic starting material. Although hydrogen per eropoly acid of tungstic acid is phosphotungstic acid. oxide of any concentration can be used, it is preferred to Molybdic acid corresponds to the formula MoO3 or employ a reaction medium containing 5-20% by weight 50 H2MoCl4. Commonly used "molybic acid' is an ammo of hydrogen peroxide. This is accomplished by adding nium salt, which contains 84-86% of MoC)3. Exemplary concentrated hydrogen peroxide, for example, 50% hetero-atoms in heteropolyacids of molybdenum in hydrogen peroxide, to an aqueous medium containing clude P, As, Si, Ge, Ti, Ce, Th, Mn, Ni, Te, I, Co, Cr, the tetrahydrophthalic starting material. The exact Fe, Ga, etc. A particularly preferred molydenum cata combination of aqueous medium and concentrated hy 55 lyst is the class of compounds known as phosphomolyb drogen peroxide can be determined by well-known dic acid, for which the approximate formula is 24 methods. MoO3.P2O5.x H2O. It is preferred to carry out the process in an aqueous Most preferred catalysts for the process are sodium solvent system. In some instances, however, it is feasible tungstate and phosphotungstic acid, which give good to employ a solvent mixture, including an organic co yields of butanetetracarboxylic acids. solvent. Typical cosolvents are , , iso The level of catalyst is generally 0.1-15% by weight propanol, dioxane, tetrahydrofuran, dimethylformam of the total charge of intermediate glycol, etc. More ide or the like. preferably, the catalyst level is 0.4-5% by weight. Oxidation of the intermediate glycol is carried out by The amount of hydrogen peroxide used in the cata adding catalyst to the resulting reaction mixture and 65 lytic oxidation of an intermediate glycol to a butanetet then adding more hydrogen peroxide and heating. racarboxylic acid is 3.0-4.5 moles of hydrogen peroxide Catalysts can be selected from among manganese per mole of glycol. Most preferably, 3.2-3.9 moles are salts, iron salts, chromium salts, cerium salts, perbo used. 5,047,582 5 6 The catalytic oxidation is carried out in the same 30 min. The resulting mixture, which corresponds to a temperature range as the non-catalytic oxidation of solution of tetrahydrophthalic acid, is cooled to 80-83 tetrahydrophthalic starting material to glycol. Accord C., after which 165 g of 50% hydrogen peroxide is ingly, temperatures of 80°-90° C. are most preferred for added over 10-20 min. and the temperature is main the oxidation of an intermediate glycol to a butanetet 5 tained at 80-83 for 3-4 h. racarboxylic acid. The course of the reaction is followed by HPLC It has been found that adding hydrogen peroxide using a Varian Chromatograph (Model 2510), with an incrementally to the aqueous reaction mixture of glycol ultraviolet detector (Model 2550 at 210 nm) and a Mi and catalyst, gives best results. Hydrogen peroxide is cropack NCH-5NCAP column. Phosphoric - acid therefore added in 5-20 equal portions at intervals of 15 O (1.2%) is used as the mobile phase at a flow rate of 1 min-2 h. Hydrogen peroxide can also be added using a mL/min. metering pump or by dropwise addition to a reaction As shown on FIG. 1, after 30 minutes' treatment with mixture. hydrogen peroxide at 80-83 C., the tetrahydroph Formation of a typical product, butanetetracarboxy thalic acid is oxidized to 4,5-dihydroxyhexahydroph lic acid, is shown on FIG. 2, in which butanetetracar 15 thalic acid, corresponding to a peak with a retention boxylic acid corresponds to the peak with a retention time of 3.27 min on FIG. 1. The formation of 4,5-dihy time of 3.88 min. The formation of butanetetracarboxy droxyhexahydrophthalic acid is confirmed by compar lic acid was also demonstrated by comparison of a C ing its retention time with that of a standard. NMR spectrum with that of an authentic sample. The peak at 1.38 min is hydrogen peroxide and that at BRIEF DESCRIPTION OF THE DRAWINGS 20 6.06 min is attributed to an intermediate. The broad In FIG. 1 is shown the HPLC chromatogram for peak about 68 min is unreacted tetrahydrophthalic acid. oxidation of tetrahydrophthalic acid with hydrogen Oxidation of tetrahydrophthalic acid to 4,5-dihydrox peroxide. yhexahydrophthalic acid is complete in 3-4 h. No peak, In FIG. 2 is shown the HPLC chromatogram for the 25 corresponding to butanetetracarboxylic acid is present sodium tungstate-catalyzed oxidation of 4,5-dihydrox in the HPLC chromatogram, run at the end of the reac yhexahydrophthalic acid to butanetetracarboxylic acid. tion as shown in FIG. 1. In FIGS. 3 and 4 are shown comparisons of HPLC The identity of the product is confirmed by obtaining chromatograms for the prior art process and the present a 13C NMR spectrum (in D2O) and comparing it with process, using sodium tungstate and phosphotungstic 30 the spectrum of a known sample. acid catalysts, respectively. EXAMPLE 2 BEST MODE FOR CARRYING OUT THE Sodium Tungstate-catalyzed Oxidation of INVENTION 4,5-Dihydroxyhexahydrophthalic Acid In a most preferred embodiment, the starting material is tetrahydrophthalic acid or anhydride (R=R'= H) 35 Sodium tungstate catalyst (4.1 g in 20 mL of water) is and the product is butane-1,2,3,4-tetracarboxylic acid. added over 15 minto the solution obtained in Example The non-catalytic step is preferably done at 80°-90 1. The reaction mixture is stirred at 80-83 C, while 165 C., using 1.8-2.5 moles of hydrogen peroxide per mole g of 50% hydrogen peroxide is added in ten portions at of tetrahydrophthalic starting material. intervals of 60 min. After all the hydrogen peroxide is Most preferred catalysts for the further oxidation of 40 added, heating at 85°-90° C. and stirring is continued intermediate glycol are sodium tungstate and phospho for 2 h more. tungstic acid. Most preferably, hydrogen peroxide is The course of the reaction is followed by HPLC, under conditions recited in Example 1. A chromato added incrementally or continuously to a reaction mix gram run shortly after addition of the catalyst and first ture containing glycol and catalyst, further oxidation is 45 carried out at 80°-90° C., and 3.2-3.9 moles of hydrogen additional portion of hydrogen peroxide shows a new peroxide are used per mole of intermediate glycol. peak at the retention time corresponding to butanetet Without further elaboration it is believed that one racarboxylic acid. At the end of 9 h, following addition skilled in the art can, using the preceding description, of the seventh portion of hydrogen peroxide, the major utilize the present invention to its fullest extent. The product on the chromatogram is that with the retention following preferred specific embodiments are, there 50 time corresponding to butanetetracarboxylic acid. In fore, to be construed as merely illustrative and not limi FIG. 2 is a chromatogram of the reaction mixture, near tative of the remainder of the disclosure in any way the end of the reaction. The major product (retention whatsoever, time 3.88 min) is butanetetracarboxylic acid. The 13C In the following examples, the temperatures are set NMR spectrum (in D2O) is identical to that of a known forth uncorrected in degrees Celsius. Unless otherwise 55 sample of butanetetracarboxylic acid. indicated, all parts and percentages are by weight. Peaks at 1.32 min, 3.30 min, and 6.33 min in the chro matogram are attributed to hydrogen peroxide, glycol, EXAMPLE 1. and an impurity, respectively. Hydrolysis of Tetrahydrophthalic Anhydride to Butanetetracarboxylic acid is isolated from the reac Tetrahydrophthalic Acid and Oxidation to 60 tion mixture by conventional methods. The product is 4,5-Dihydroxyhexahydrophthalic Acid white. The yield is 82%, mp (capillary) 195-196° C. To a 1000 mL flask equipped with stirrer and reflux EXAMPLE 3 condenser is charged 100 g of water. The contents of the flask are stirred while 182.4 g of tetrahydrophthalic 65 Phosphotungstic Acid-catalyzed Oxidation of anhydride is charged to the flask. Cooling water for the 4,5-Dihydroxyhexahydrophthalic Acid condenser is turned on and the contents of the flask are The reaction is carried out as in Example 2, using as heated to 95-100° C. and held at this temperature for catalyst 3 g of phosphotungstic acid in 20 mL of water. 5,047,582 7 8 White butanetetracarboxylic acid is recovered from the reaction mixture by conventional techniques. The yield EXAMPLE 8 Hydrolysis and Oxidation of is 82%. 3-Methyltetrahydrophthalic Anhydride EXAMPLE 4 The Diels-Alder adduct from phthalic anhydride and Sodium Tungstate-catalyzed Oxidation of piperylene is hydrolyzed and partially oxidized as in 4,5-Dihydroxyhexahydrophthalic Acid Example 1 and further oxidized as in Examples 1 and 2. The oxidation is carried out as in Example 2, using Similar results are obtained. 195g of hydrogen peroxide and sodium tungstate dihy 10 EXAMPLE 9 drate catalyst. Oxidation of 4,5-Dihydroxyhexahydrophthalic Acid A comparative run, using the process of U.S. Pat. No. 4,5-Dihydroxyhexahydrophthalic acid, prepared as 4,833,272 (Example 5), and sodium tungsten dihydrate in Example 1, is oxidized with hydrogen peroxide, using catalyst is made, starting with 182.4 of tetrahydroph 15 the following catalysts: thalic anhydride and 195g of 50% hydrogen peroxide (a) Na2S2O8 and 4.1 g of catalyst. Hydrogen peroxide is added over (b) Na2B4O7 3 h. (c) K2Cr2O7 The peaks at 5.14/5.16 min are attributed to an impu (d) Na2SiO3 rity and the peaks at 1.4 min and 2.8 minto hydrogen 20 (e) (NH4)2Ce(SO4)3.2 H2O peroxide and glycol respectively. The impurity peak is The formation of butanetetracarboxylic acid is con considerably larger in the product from the prior art firmed. process, than in the product from the process of the The preceding examples can be repeated with similar invention as shown in FIG. 3. success by substituting the generically or specifically 25 described reactants and/or operating conditions of this The yield of butanetetracarboxylic acid is 83%. The invention for those used in the preceding examples. yield by the prior art process is 75%. From the foregoing description, one skilled in the art EXAMPLE 5 can easily ascertain the essential characteristics of this invention and, without departing from the spirit and Phosphotungstic Acid-catalyzed Oxidation of 30 scope thereof, can make various changes and modifica 4,5-Dihydroxyhexahydrophthalic Acid tions of the invention to adapt it to various usages and conditions. Oxidation of the glycol intermediate is carried out as We claim: in Example 3, except that 195g of hydrogen peroxide is 1. A process for oxidation of a tetrahydro compound used. 35 of the formula A comparative run is done according to U.S. Pat. No. 4,833,272 (Example 5), adding hydrogen peroxide over 3 h, using 182.4 g of tetrahydrophthalic anhydride, 195 g of 50% hydrogen peroxide and 3 g of phosphotung COOH stic acid (H3PO4.12WO3.xH2O). The peak at 5.81/5.85 min are attributed to an impu COOH rity and the peak at 1.4 min to hydrogen peroxide. The impurity peak is larger in the product from the prior art R process than in the product from the process of the 45 wherein R and R' independently are H, alkyl, aryl or invention as shown in FIG. 4. halo, to a glycol of the formula The yield of butanetetracarboxylic acid is 85%. The yield by the prior art process is 83%. R EXAMPLE 6 HO COOH 50 Manganese Chloride-catalyzed Oxidation of 4,5-Dihydroxyhexahydrophthalic Acid HO COOH Manganese (II) chloride (4 g in 20 mL of water) is used as catalyst for the oxidation of a product of Exam 55 ple 1. The course of the reaction is similar to that of comprising treating the tetrahydro compound with Examples 2 and 3. The butanetetracarboxylic acid prod hydrogen peroxide under reflux conditions at a temper uct, isolated using conventional procedures, is discol ature above about 50 C. to 100° C. in the absence of a ored. The yield is 43%. catalyst. 2. The process of claim 1, wherein R or R' is methyl. EXAMPLE 7 3. The process of claim 1, wherein R and R' are H. 4. The process of claim 1, wherein hydrogen peroxide Ferrous Sulfate-catalyzed Oxidation of is in the form of an aqueous solution. 4,5-Dihydroxyhexahydrophthalic Acid 5. The process of claim 1, wherein oxidation is carried The oxidation is carried out as in Example 4, using as 65 out with 1.8-2.5 moles of hydrogen peroxide per mole catalyst 4 g of ferrous sulfate in 20 mL of water. The Clf tetrahydro compound. product, after isolation by conventional methods, is 6. The process of claim 1, wherein oxidation is carried discolored. The yield is 23%. out at 70°-100° C. 5,047,582 9 10 12. The process of claim 2, wherein the catalyst is 7. The process of claim 1, wherein R and R' are H; phosphotungstic acid. hydrogen peroxide is in the form of an aqueous solution 13. The process of claim 12, wherein the catalyst and oxidation is carried out with 1.8-2.5 moles of hy comprises 0.1-10% by weight of the total charge of drogen peroxide per mole of tetrahydro compound at 5 intermediate glycol. 80°-90° C. 14. The process of claim 2, carried out at a tempera 8. The process of claim 1, wherein the oxidation is ture of 80-90 C. carried out in the presence of 1-2.6 moles of hydrogen 15. The process of claim 2, wherein oxidation of the peroxide per mole of tetrahydro compound. glycol is carried out with 3.2-3.9 moles of hydrogen 9. The process of claim 1, including further oxidation 10 peroxide per mole of glycol. - of the thusformed glycol to a butanetetracarboxylic 16. The process of claim 2, wherein the catalyst is acid of the formula sodium tungstate, further oxidation is carried out at 80°-90° C., hydrogen peroxide is used in an amount of 3.2-3.9 moles per mole of glycol and hydrogen peroxide RCHCOOH 15 is added incrementally or continuously to a reaction CHCOOH mixture of catalyst and glycol. 17. The process of claim 2, wherein the catalyst is CHCOOH phosphotungstic acid, further oxidation is carried out at R"CHCOOH 80°-90° C., hydrogen peroxide is used in an amount of by heating under reflux conditions at a temperature 20 3.2-3.9 moles per mole of glycol and hydrogen peroxide above about 50 C. to 100° C. with hydrogen peroxide is added incrementally or continuously to a reaction in the presence of a catalyst selected from the group mixture of catalyst and glycol. consisting of a manganese salt, an iron salt, a chronium 18. The process of claim 2, wherein the catalyst is salt, a cerium salt, a perborate, a persulfate, a silicate, manganous chloride. 25 19. The process of claim 2, wherein hydrogen perox tungstic acid or an ammonium or alkali metal salt or ide is added incrementally or continuously to a reaction heteropolyacid thereof, or molybdic acid or an ammo mixture containing glycol and catalyst. nium or alkali metal salt or heteropolyacid thereof. 20. The process of claim 19, wherein the catalyst is 10. The process of claim 2, wherein the catalyst is present in an amount of 0.1-10% by weight of the total ferrous sulfate. 30 charge of intermediate glycol, and hydrogen peroxide is 11. The process of claim 2, wherein the catalyst is used at a molar ratio of 3.0-4.5 to intermediate glycol. sodium tungstate. x k k k E

35

45

SO

55

65