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an II/EC Unit Processes Review
Oxidation-Liquid Phase by W. G. Toland and S. J. Lapporte, California Research Corp., Richmond, Calif
Growth potential of petrochemicals is paced by oxidation of hydrocarbons
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Direct liquid phase oxidation of ethylene shows promise as a route to acetaldehyde o-Phthalic and terephthalic acids are made from inexpensive toluene by chloromethylation and "03 oxidation
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F THE BULK of today's research activity is a valid indication of tomorrow's products and processes, then the future of liquid phase oxidation looks very bright. I n the period covered by this review, the more significant disclosures taken from the literature and patents issued reveal increased production of aromatic acids, methacrylic acid, phenol, acetaldehyde, and primary alcoholsall by liquid phase oxidation. Research activity shows heightened interest in air oxidation of paraffins and organometallics and the mechanism of chemical oxidations of hydrocarbons. This review covers the period April 1960 through March 1961.
General Production of phenol by oxidation of aromatics continues to expand. A 50 to 75 million pound per year cumene oxidation plant is planned by Monsanto. A total of three plants are planned and may be in operation this year using the California Research Gorp.-Dow process of oxidizing toluene to phenol. The intermediate benzoic acid is oxidized to phenol by an oxygencontaining gas and a copper catalyst. This reaction is characterized by the placement of a hydroxyl group in a position ortho to the original carboxyl group. (Some details of a toluene to phenol process are given in this issue, page 805.) More details of the Wacker-Hoechst acetaldehyde from ethylene process show this to be a versatile new reaction. The aqueous catalyst solution contains copper and palladium compounds, among others, and can accommodate air or oxygen and a range of olefins. Olefins higher than ethylene normally give ketones, although aldehydes may be formed under certain conditions (47). New disclosures describe catalyst solution composition (46), reduction of
corrosion (49), and operating conditions (50, 57). The ease of olefin oxidation has been correlated with the stability of the divalent palladium-olefin complex (90). I t is of interest that Dow has recently described a similar process using an acidic vanadium solution as catalyst (80). A sizable Russian literature on air oxidation of paraffins, alicyclics, and aromatics indicates considerable interest in this field; however, there appears to be a 10- to 20-year lag behind similar information published in Germany and the U . S. Much of the Soviet effort seems directed toward the production of fatty alcohols ( 7 78) and nonedible fatty acids by oxidation of paraffins. In China, this area is also being re-explored (79). The use of H3B03 to favor alcohol formation in n-paraffin oxidation, long known in this country and recently improved upon in Russia, has been reported by Chinese workers to give an alcohol fraction which was 60% primary alcohol, a most surprising and possibly questionable result (83, 732). Increased activity in the study of the mechanism of drying of unsaturated fatty acid derivatives is apparent. Such studies are relevant to the problems of food rancidity and the drying of paints.
Increased attention is also being given to the oxidation of high molecular weight olefins, particularly as it affects their stability. The mechanism of autoxidation of olefins has also been investigated. Kinetically, co-oxidation of olefins, such as methyl linoleate and dimethylbutadiene, has been treated much the same as copolymerization of olefins (73). Unlike the oxidation of saturated hydrocarbons, the rate of metal-salt catalyzed oxidation of methacrolein is oxygen dependent, suggesting the rate-determining nature of the reaction of an unsaturated acyl radical with oxygen (20). Conoco's Alfol process for making primary alcohols, due to go on stream this year, utilizes the oxidation of aluminum alkyls (29). The autoxidation of organoboron (32), organozinc ( I ) , and possibly other organometallic compounds involves attack of molecular oxygen on the metal atom followed by a 1,3-rearrangement of the alkyl group to the positive oxygen, leading to an alkylperoxy salt. Air oxidation of resonance stabilized carbanions, however, forms free alkyl radicals which may be isolated as dimeric products (99). I n the field of inorganic chemistry, the oxidation of sulfur by oxygen in
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AVAILABLE FOR ONE DOLLAR The complete annotated bibliography of the 1960 Unit Processes Review of Oxidation-Liquid Phase by Toland. After one year this material can be obtained from the AD1 Auxiliary Publications Project, Library of Congress, Washington 25, D. C., as Document No. 6837. The price will then be $2.25 for microfilm and $5.00 for photostat copies.
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Table I. Product
Starting Material
Phthalate esters Benzoic acid
Dialkylbenzenes Acetophenone
Naphthoic acid p-Toluic acid
Alliylnaphthalenes Ditolylmethane
Isonicotinic acid
4-Alkylpyridine
Cumene hydroperoxide Acetylphenol Nitroacetophenone
Cumene Acetylcumene Nitrocumene
Cyclohexanone a-Methylstyrene oxide Diphenyl diacetylene Triphenylbismuth
Phenylcyclohexane a-Methylstyrene Phenylacetylene Phenylhydrazine
Hydroxyethyl sulfoxides
Phenylmercaptan a n d styrene
Naphthoic acids
Dimethylnaphthalenes Triisopropylbenzenes p-Cymene Xylenes Toluene
Trihydroperoxide p-Isopropylbenzoic acid Phthalic acid Phenol
and a book on catalysis including oxidation edited by Emmett (42). Mayo has predicted the likely improvement i n surface coatings, rubber, gasoline, and antioxidants to be gained from continued study of the oxidation of unsaturated compounds (87).
Air O x i d a t i o n of Aromatic Compounds Romarks
In alcohol solvent; esters one step M n catalyst, AcOR solvent, "01 promoter Co catalyst, 15Oo-18O0 C. Via K O H cleavage of dimethylbenzophenone Metallic catalyst, acid solvent, 500' F. Metal phthalocyanine catalyst Via hydroperoxide, acid cleavage Via hydroperoxide, metal salt cleavage Via hydroperoxide, acid cleavage Base present, 6Oo-13O0 C. CuCl catalyst in pyridine Presence of aqueous CuC12, FeCI1, a n d BiCla Via S-containing hydroperoxides a t Oo C. and room temperature; rearrangement Cu, VZOS, P t catalysts
Air Oxidation of Aromatics
From 1,3,5-isomer; base present Microbiological oxidation Ozone initiation Via benzoic acid: Cu-catalyzed air oxidation
The conversion of xylenes and other dialkylbenzenes to phthalic acids and esters continues to represent an appreciable proportion of the industrial activity in the field of catalytic air oxidation. Montecatini, in Italy, has announced plans to build a dimethyl terephthalate (DMT) plant. I t has licensed the route from p-xylene, which proceeds via methyl p-toluate (24). The number of patents being issued on modifications of this process suggests that a number of companies have been considering this route. Several of these have attemDted to simdifv the urocess bv oxidizine xvlenes to Dhthalate esters directly in an alcohol solvent (7, 43). The widespread utility of metal bromides as catalysts for oxidations of a variety of alkylbenzenes to aromatic acids is evident, the patent references being too voluminous to include here. An early position in bromide catalysis was established by Amoco and Scientific Design Co. ; since then, considerable effort has been spent to improve existing processes and control certain fine points of the oxidation. Patents have been issued describing catalyst recovery and recycle (23),removal of formic acid from acetic acid solvent systems (70), minimizing oxidation of aliphatic acid solvents by low oxygen concentration ( 8 9 ) , or by the addition of specific alkali metal or alkaline earth metal compounds (730), maintaining the oxidation rate by keeping the soluble iron concentration low (77), and improving yields through the use of high purity xylenes (27). The interest of Cowles Chemical Co. in a catalytic liquid phase oxidation process for the phthalic acids has gelled into an exclusive license to Catalytic Construction Co. which claims to be ready to offer the route to phthalic anhydride from o-xylene. The process is rumored to be a two-stage oxidation involving air and "03. T h e air oxidation of aromatics, particularly cumene, has also been considered mechanistically. The rate-accelerating effect of cobalt salts in low concentration has been attributed to a decrease in the reactivity of cumylperoxy radicals toward chain termination rather than any enhancement of initiation rate (77). Further, the transition state for termination by cumylperoxy radicals has been described as a "headI
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liquid NH3 under pressure at room temperature leads to compounds whose empirical formula is 6 0 2 . 5 X H 3 ; moreover, these compounds are different from those formed by reaction of S O 2 or S O 3 withNH3 (723). The oxidation of SO2 to (NHd)zSO* without the intermediate formation of HzS04 is the basis for a new industrial process. Sulfur dioxide-containing gases, as from smelters, are absorbed in a basic organic solvent, such as coal tar bases, and oxidized with air. Ammonium sulfate is liberated from the organic base by treatment with "3. On the other hand, "3 itself can be oxidized in CCl4 solution if catalytic amounts of lower oxides of certain metals, particularly CuzO or Cu&, are present (93, 94). More information is available about the Zimmerman process of wet oxidation of sewage sludge. At 150' to 370' F.
and high pressures, air rapidly oxidizes dilute organic waste, more or less completely, with a net production of heat (734). The operation of a small pilot plant has been described (68). A new approach to H202 production has been reported. A stream of oxygensaturated water. passed through a hydroquinone-formaldehyde redox resin, converts 80 to 100% of the oxygen into H 2 0 2 . The peroxide concentration can be increased by recycle ; however, the resin itself slowly decomposes the HZOz. Other quinones can be used to impart greater stability to the resins (86). Several valuable reviews have appeared this year, including the primary processes in photo-oxidation (63), industrial organic oxidizing reactions (700), petrochemicals by liquid phase oxidation of hydrocarbons (88, 107), reaction mechanisms involving peroxides (777),
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a to-head" reaction, such that each peroxy radical contributes one oxygen atom to the evolved oxygen molecule (722). A new method was found for preparing aromatic bismuth compounds by the CuCl2-catalyzed air oxidation of an arylhydrazine-BiC18 mixture (22). Similar reactions are known for the arsenic and antimony derivatives. When air is introduced into mixtures of aromatic mercaptans and reactive olefins, such as styrene or indene in hydrocarbon solvents at 0' C., a new class of sulfur-containing hydroperoxides, A r S C H 2CH ( A r ) 0 O H , is formed. These rearrange at room temperature to the corresponding hydroxyethylsulfoxides, ArSOCH2CH(Ar)OH (92). Such co-oxidations of mercaptans and olefins may be responsible for some of the color, gum, and sediment formation in untreated petroleum distillates. Further notable examples of air oxidations of aromatics, as well as air oxidations of some aliphatic and alicyclic compounds, are presented in Tables I, 11, and 111.
Chemical Oxidants Several results are worth noting. The " 0 3 oxidation of tri-p-tolyltriazine gives triphenyl triazine-$,$ ',p 'I-tricarboxylic acid, indicating the resistance of the triazine ring to oxidation (38). Perfluorocarboxylic acids can be prepared in good yields by permanganate oxidation of perfluoroolefins, a technique used not only in the U. S. (18) but recently patented in Russia as applied to perfluorodiolefins for a,w-perfluorodicarboxylic acids (75). Publications from both countries point out the value of hypochlorite as a n oxidizing agent, not only of acetyl groups attached to aromatics but of alkyl groups activated by acetyl groups as well (78, 97). By this reaction, p-ethylacetophenone may be oxidized to terephthalic acid. Chloroform is also produced, suggesting that the haloform reaction is one of the steps in the reaction sequence. Widening interest in the use of oxides of nitrogen and " 0 3 as oxidizing agents is evident. For example, the oxidation of isobutene by nitrogen oxides yields a-hydroxyisobutyric acid (4, 56, 707). Escambia Chemical Co. has announced plans to use this route to methacrylic acid. The related " 0 3 oxidation of olefins in general is believed to involve addition of nitrosonium nitrate to the double bond, followed by isomerization and hydrolysis to a hydroxycarbonyl compound. Further oxidation leads to the product acids (55). Chloromethylation of toluene followed by a two-step HNO, oxidation,
Table II.
Paraffins n-Paraffins
Alcohols
Olefins
Alcohols
AI trialkyls
Alcohols Peroxides
Alkylaluminum compounds Alcohols
Aldehydes
Olefins
Epoxides, aldehydes Isoprene
Olefins Isopentene
Hydroxysulfoxides Alcohols Hydroperoxides Methylpentadienes
Mercaptans and olefins Paraffins Methyl linoleate Propylene dimers
Dialkylphosphoric acid esters Dicarboxylic acids
Vinyl chloride and methyl dichlorophosphine n-Paraffins
Aldehydes and ketones Esters
Primary and secondary alcohols Capric acid
Diols, unsaturated and primary alcohols Hexyl alcohols
1-Dodecene Propylene dimers
first of the chloromethyl group and then of the methyl group, presents an interesting route to phthalic and terephthalic acids (6, 75,25). Several well known chemical oxidations have been studied mechanistically. Unlike the oxidation of alcohols or aldehydes, which involve the preliminary formation of chromate esters, the H2Cr04 oxidation of hydrocarbons involves abstraction of a hydrogen atom to form pentavalent chromium species and a hydrocarbon-free radical within a solvent cage. Collapse to a tetravalent chromium ester followed by hydrolysis gives an alcohol with retention of stereochemical configuration (737). The structure of the chromyl chloride complex formed in the oxidation of
Table 111.
Dicarboxylic acids Cyclo-octanone a,w-Dicarboxylic acid
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d Unit Processes Review
Air Oxidation of Aliphatic Compounds
Starting Material
Product Fatty acids Aliphatic alcohols
Product Cyclohexanol-cyclohexanone Alicyclic ketoximes
n
Remarks Use of ultrasonic vibrations Ester of HJBOP,HaPOa, HYPO,, HaAsOi Via epoxide to aldehyde, hydrogenation C12 and greater alcohols from ethylene Incomplete oxidation Ultraviolet radiation and photo sensitizer Aqueous solution of P t metal compounds By oxidation of olefin-Hg compound Reduction of hydroperoxide ; dehydration Accelerated by C1 or Br &Boa present; 60% primary 9- and 13-cisJrans products By dehydration of epoxides and alcohol At -2OO C. with oxygen
Mn naphthenate catalyst, high conversion, and pressure; hydrolysis P t catalyst, long chain compounds Octadecane solvent, decarboxylation 4% 02, E&BOs present By reduction and hydrogenation of hydroperoxides
toluene to benzaldehyde has been described by spectral and magnetic measurements as C6HbCH(OCrOHC12)e ( 729). The mechanism of oxidation of organometallics by H202 proceeds by formation of an organometallic hydroperoxide followed by a 1,2-rearrangement of the alkyl group from metal to oxygen (32). This leads to the formation of a metal alkoxide. I n contrast, the air oxidation of organometallics gives alkylperoxy metal salts as intermediates. Preparation of alcohols by HzOz oxidation of alkylbcranes derived from olefins by hydroboration (27) has become a common synthetic method. Further examples of the use of chemical oxidants are presented in Table IV.
Air Oxidation of Alicyclic Compounds
Starting Material Cyclohexane
Remarks Critical bubble size for control of products; metallic catalyst Alicyclic hydroxylamines Alcohol or hydrocarbon solvent, Co or Cu catalyst Cycloalkenes Ozonization ; oxidative cracking Cyclo-octane Metal salt catalysts, 12Oo-14OD C. 2-Chloro-1-formyl-1-cyVia 2-chloro-1-cycloalkene carcloalkene bosylic acid and hydrolysis
VOL. 53, NO. 10
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Ref (69. (70)
(45) (8) (133)
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Unit Processes Review
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Table IV.
Chemical Oxidants Starting Material
Product Dimethylquinones
Dimethylphenols
Chlorofluoro acids
Perhaloolefins
Crude H102; dilute Tertiary hydroTertiary alcohols HzO?in Hap04 ; peroxides 4O0-5Oo C. Dimeric fatty acids Unsaturated fatty With organic acids peroxides Cyclohexylamine Cyclohexanone H202 ; aqueous oxime Na2W04 catalyst a-Haloglutaric acid 3-Halocyclopentene HzO?in aqueous ozonide acid LiZO? LiOH H20P in methanol Biacetyl Methyl vinyl ketone HZ02in aqueous NaHC03; via epoxide Ethylene glycol Ethylene HzOyin fert-butyl alcohol ; OsOl catalyst e-Caprolactones Cyclohexanones Anhydrous peracetic acid; 30'-70' C.
Tolualdehydes Perfluorodicarboxylic acids
Xylenes a,w-perfluorodiolefins
Homophthalic acid
Fluorene
1,3-Cyclopentane dicarboxjdic acids Tetramethylammonium ozonate
Bicyclo(2,2,1)-2heptenes
" O B OR NITROGENOXIDES Benzene polyChloromethylxyDilute "01 ; carboxylic acids lenes 15O0-3OO0 C. high yields Terephthalaldehyde p-Xylylene dichloDilute " 0 3 ; ride 1020- 1100 c. Hydroxyisobutyric Isobutene N n 0 4 ,low temacid perature ; hydrolysis Mellitic acid Coal, coke HNOJ, finish with C1,-NaOH CI-CIOdicarboxylic Shale oil 98% HNOJ, 80' C. acids Fluorobenzoic acid Fluorotoluene 20% "03 or NOZ-water Tritolylbenzene Pressure, 200° C.; Terephthalic acid ring rupture Triphenyltriazine Tri-p-tolyltriazine 10-20% "03, p-p'-p"-tricar18Oo-19O0 C. ; boxylic acid some tercphthalic formed Dialkylsulfoxides Dialkyl sulfides NzOl in sulfoxide solvent Anthraquinone Anthracene Concentrated "05, 150' C., in nitrobenzene
Phthalic acids and CHCL Phthalic acids and CHCh Carbonyl compounds Unsaturated CSbromides Perchlorates
Product Cyclohexyl 1 , l peroxide Amine oxides Monopersulfates Peroxymonophosphoric acid Alkali perborates
Starting Material Remarks PEROXIDES Cyclohexanone H p O rin AcOH; H2S04 catalysis Tertiary amines H2O2 in formate esters HnSOi H202 and alkali persulfates P205 HnOn, 30'-3.5' C.
(1) A b r a h a m , M. H., J . Chem. Sac. 1960, p. 4130. (2) Air liquide (SOC. a n o n . p o u r l'etude et l'exploration des procedes Georges Claude), Fr. P a t e n t 1,163,205 (Sept. 23, 1958). (3) Aries, R. S., U. S. Patent 2,930,802 ( M a r c h 29, 1960). (4) Zbid., 2,971,981 (Feb. 14, 1961). (5) Arnold, Z . , Ratusky, J . , others, Czech. P a t e n t 93,298 (Dec. 15, 1959). (6) Badische Anilin- & Soda-Fabrik A.-G., Belg. P a t e n t 585.118 ( M a r c h 16, 1960). (7) Bidische Anilin- & Soda-Fabrik A.-G., Ger. P a t e n t 1,085,146 (July 14, 1960). (8) Zbid., 1,082,590 ( J u n e 2, 1960). (9) Zbid, 1,080,112 (April 21, 1960).
814
AIN COMPOUNIx3
Metaborates
Literature Cited
.
Pyridine and trialkyl phosphates Oxalic acid Phenol
(34)
Tetramethylammonium hydroxide
Olefins Butadiene Alkali chlorates Trialkylphosphites and tert-phosphines
Tropone
Cycloheptatriene
Soaps
High mol. wt. alcohols
Phthalic acids
Xylenes
Saturated acids
Unsaturated acids
(36)
(37) (58)
(67, 121) ('76)
Aromatic portion attacked By oxidation of ozonide Oxidizing agent
MISCELLASEOUS Pyridine-S-oxide Catalyzed by perand trialkyl phosoxides and O Z phite Ascorbic acid With HrNOH.HC1 and CuSO4 Benzene Aqueous Cu(I1) ion, radiolysis Diacetylbenzenes Ca(C10)z; 65'70' C. Alkylacetylbenzenes NaClO
Trialkylphosphate and phosphine oxides
(15) ~ ~ A., Grosskinsky, ~ ~ 0.: F r uih buss, H. (to Bergwerksverband, G.m. b.H.), Zbid., 2,966,514 (Dec. 27, 1960). (16) Bergwerksverband G.m.b.H.. Ger.
INDUSTRIAL AND ENGINEERING CHEMISTRY
Permanganate, Oo C.; hydrolysis of acid halides With Mnp(SOa)a KMnOa in aqueous acetone, 20°-250 C.
OZONE
(10) Bataafsche Petroleum Maatschappij, N. V. d e , Brit. Patent 855,751 (Dec. 7. ,~ 1960). (1 1) Bataafsche Petroleum Maatschappij, N. V. de, Ger. P a t e n t 1,087,589 (Aug. 25, 1960). (12) Bashkirov, A. N.: Pal, S., Proc. Acad. Sci. U.S.S.R., Cliem. Sect. 128, 875 (1959) (English transl.). (13) Berezin, I. V., R a g i m o v a , A. M.: Emanuel, N. iM., Bull. Acad. Sci. U.S.S.R., Diu. Chem. Sci. 1959, p. 1661 (English transl.). (14) Bengelsdorf, I. S. (to General Electric Co.), U. S. P a t e n t 2,948,756 (Aug. 9, i om\ I , V",
Remarks NO-NO2 in concentrated HnS04; -10'30' C.
Aqueous acidic vanadium(V) Ce(1V) ions and Br-, via Br Electrolytic oxidation persulfate catalyst With N,N-disubstituted trichloroacetamides, giving trichlorovinylamines SeOn in AcOHwater Concentrated caustic, high temperature, pressure (NH,)2SOa oxidant Caustic cleavage and oxidation
Patent 1,087,124 (Xug. 18, 1960). (17) Blanchard, H. S . , J . Am. Chem. SOG. 82, 2014 (1960). (18) Brandon, D. B. (to Minnesota Mining a n d Mfg. Co.), U. S. P a t e n t 2,950,300 (Aug. 23, 1960). (19) Bredereck. H., Wagner, A., K o t t e n h a h n . A,. Chem. Ber. 93. 2415 (19601. (20) Brill. it7.F.. Lister.'F., J . Or,
