Acrylic acid oxidation

Black, K.A. Finch, L. (1995) Acrylic acid oxidation and tissue-to-blood partition coefficients in rat tissues. Toxicol. Lett., 78, 75-78... 

The oxidation of acrylic acid also follows the reaction mechanism of Mars-van Krevelen, figure 8. In contrast to the acrolein oxidation no hindrance of reoxidation is observed when the partial pressure of acrylic acid is raised Addition of water vapor causes only a small increase of the rate of acrylic acid oxidation also in contrast to the considerable effect in acrolein oxidation, figure 9. 

The results obtained by N2 adsorption are presented in table 3, as well as 6TOC/S (TOC variation as a function of unit area) obtained for acrylic acid oxidation. MnCe7 and CoCe7 have the highest surface areas. On the other hand, Mn Ox exhibited the lowest value, only 32 m /g while all other surface areas were higher than 91 mVg. Nevertheless, the TOC variation per unit of surface area achieved with Mn Ox is the highest of all. 

In allylic oxidation reactions (Eqns. 8-13), an olefin (usually propylene) is activated by the abstraction of a hydrogen a to the double bond to produce an allylic intermediate. This intermediate can be intercepted by catalyst lattice oxygen to form acrolein or acrylic acid (oxidation), lattice oxygen in the presence of ammonia to form acrylonitrile (ammoxidation),... 

Glycidic Acid Ethylene oxide carboxylic acid, acrylic acid oxide)... 

Ml phase " represents the clearest example of a multifunctional catalyst in which each element, in close geometrical and electronic synergy with the surrounding elements, plays a specific role in turn, as an isolated active site, in every reaction step for the alkane transformation into the partial oxidation product desired. The flexibility of the structure allows modification of the catalyst composition and hence its catalytic behavior. Moreover, this type of mixed-metal oxide catalyst has the ability to catalyze other different oxidation reactions starting from alkanes, such as propane oxidation to acrylic acid, " oxidative dehydrogenation of ethane to ethylene, and n-butane selective oxidation. ... 

Figure 24.10. Variation of the yield of acrylic acid (oxidation) and acrilonitrile and acrylic acid (ammoxidation) with the reaction temperature, with the propane/steam and propane/ammonia ratio, respectively. Y a = to acryhc acid Yan = to acrilonitrile. From Ref. 250.

CHjlCH COOH. Colourless liquid having an odour resembling that of ethanoic acid m.p. 13 C, b.p. I4I°C. Prepared by oxidizing propenal with moist AgO or treating -hy-droxypropionitrile with sulphuric acid. Slowly converted to a resin at ordinary temperatures. Important glass-like resins are now manufactured from methyl acrylate, see acrylic resins. Propenoic acid itself can also be polymerized to important polymers - see acrylic acid polymers. 

Poly(acrylic acid) and Poly(methacrylic acid). Poly(acryHc acid) (8) (PAA) may be prepared by polymerization of the monomer with conventional free-radical initiators using the monomer either undiluted (36) (with cross-linker for superadsorber appHcations) or in aqueous solution. Photochemical polymerization (sensitized by benzoin) of methyl acrylate in ethanol solution at —78° C provides a syndiotactic form (37) that can be hydrolyzed to syndiotactic PAA. From academic studies, alkaline hydrolysis of the methyl ester requires a lower time than acid hydrolysis of the polymeric ester, and can lead to oxidative degradation of the polymer (38). Po1y(meth acrylic acid) (PMAA) (9) is prepared only by the direct polymerization of the acid monomer it is not readily obtained by the hydrolysis of methyl methacrylate. 

The significance of industrial acrolein production may be clearer if one considers the two major uses of acrolein—direct oxidation to acryUc acid and reaction to produce methionine via 3-methyhnercaptopropionaldehyde. In acryUc acid production, acrolein is not isolated from the intermediate production stream. The 1990 acryUc acid production demand in the United States alone accounted for more than 450,000 t/yr (28), with worldwide capacity approaching 1,470,000 t/yr (29). Approximately 0.75 kg of acrolein is required to produce one kilogram of acryUc acid. The methionine production process involves the reaction of acrolein with methyl mercaptan. Worldwide methionine production was estimated at about 170,000 t/yr in 1990 (30). (See Acrylic ACID AND DERIVATIVES AmINO ACIDS, SURVEY.)... 

Reaction conditions depend on the reactants and usually involve acid or base catalysis. Examples of X include sulfate, acid sulfate, alkane- or arenesulfonate, chloride, bromide, hydroxyl, alkoxide, perchlorate, etc. RX can also be an alkyl orthoformate or alkyl carboxylate. The reaction of cycHc alkylating agents, eg, epoxides and a2iridines, with sodium or potassium salts of alkyl hydroperoxides also promotes formation of dialkyl peroxides (44,66). Olefinic alkylating agents include acycHc and cycHc olefinic hydrocarbons, vinyl and isopropenyl ethers, enamines, A[-vinylamides, vinyl sulfonates, divinyl sulfone, and a, P-unsaturated compounds, eg, methyl acrylate, mesityl oxide, acrylamide, and acrylonitrile (44,66). 

In paints, zinc oxide serves as a mildewstat and acid buffer as well as a pigment. The oxide also is a starting material for many zinc chemicals. The oxide supphes zinc in animal feeds and is a fertilizer supplement used in zinc-deficient soils. Its chemical action in cosmetics (qv) and dmgs is varied and complex but, based upon its fungicidal activity, it promotes wound healing. It is also essential in nutrition. Zinc oxide is used to prepare dental cements in combination with eugenol and phosphoric and poly(acrylic acid)s (48) (see Dental materials). 

Acetic acid (qv) can be produced synthetically (methanol carbonylation, acetaldehyde oxidation, butane/naphtha oxidation) or from natural sources (5). Oxygen is added to propylene to make acrolein, which is further oxidized to acryHc acid (see Acrylic acid and derivatives). An alternative method adds carbon monoxide and/or water to acetylene (6). Benzoic acid (qv) is made by oxidizing toluene in the presence of a cobalt catalyst (7). 

Polycarboxylate Cements. Polycarboxylate cements (30,31) are made by mixing a 2inc oxide-based powder and an aqueous solution of poly(acryHc acid) [9003-01 ] or similar polyacid (see Acrylic acid). The biological effects of these cements on soft and minerali2ed tissues are mild (32). 

The addition of benzonitrile oxide to acrylic acid gave only the 4-carboxylic acid (441) (59MI41601), while addition to cis- and trans-cinnamic esters gave cis and trans diastereomeric pairs of 4-carboxylic acids (442) (Scheme 100) (59MI41600). Arbisono repeated the experiment and, when methyl c/s-cinnamate was used, in addition to the 4-carboxylic acid some 5-carboxylic acid (442) was isolated (66MI41600). The reaction of vinyl bromides with benzonitrile oxide yielded only an isoxazole and not a bromoisoxazoline (Scheme 101) (78JCR(S)192). 

These enable temperature control with built-in exchangers between the beds or with pumparound exchangers. Converters for ammonia, 80.3, cumene, and other processes may employ as many as five or six beds in series. The Sohio process for vapor-phase oxidation of propylene to acrylic acid uses hvo beds of bismuth molybdate at 20 to 30 atm (294 to 441 psi) and 290 to 400°C (554 to 752°F). Oxidation of ethylene to ethylene oxide also is done in two stages with supported... 

Degenerate Explosion it was a free radical autocatalytic process and control was difficult, but manageable. The main disadvantage was that it produced as much or more acrolein as propylene oxide. Because no market existed for acrolein at that time, the project was abandoned. Within two years, the acrylic market developed and a new project was initiated to make acrolein and acrylic acid by vapor-phase catalytic oxidation of propylene. 

Because the polymer degrades before melting, polyacrylonitrile is commonly formed into fibers via a wet spinning process. The precursor is actually a copolymer of acrylonitrile and other monomer(s) which are added to control the oxidation rate and lower the glass transition temperature of the material. Common copolymers include vinyl acetate, methyl acrylate, methyl methacrylate, acrylic acid, itaconic acid, and methacrylic acid [1,2]. 

Note Maximum ambient levels for ethylene oxide are 0.3 ppb at the plant fence. Maximum total emissions of the VOCs acetaldehyde, acrylic acid, benzyl chloride, carbon tetrachloride, chlorofluorocarbons, ethyl acrylate, halons, maleic anhydride, 1,1,1-trichlorethane, trichloroethylene, and trichlorotoluene are 20 mg/Nnf. Maximum total heavy metal emissions are 1.5 mg/Nnf. 

The new propylene oxidation process uses less hazardous materials to manufacture acrylic acid, followed by esterification with the appropriate alcohol (Hochheiser, 1986) ... 

Attenlion should be drawn to ihe use of tin oxide systems as heterogeneous catalysts. The oldest and mosi extensively patented systems are the mixed lin-vanadium oxide catalysis for the oxidation of aromatic compounds such as benzene, toluene, xylenes and naphthalene in the. synthesis of organic acids and acid anhydride.s. More recenily mixed lin-aniimony oxides have been applied lo the selective oxidaiion and ammoxidaiion of propylene to acrolein, acrylic acid and acrylonilrile. 

Currently, the main route to acrylic acid is the oxidation of propene (Chapter 8). 

The direct oxidation of propylene using air or oxygen produces acrolein. Acrolein may further he oxidized to acrylic acid, which is a monomer for polyacrylic resins. 

Transition metal oxides or their combinations with metal oxides from the lower row 5 a elements were found to be effective catalysts for the oxidation of propene to acrolein. Examples of commercially used catalysts are supported CuO (used in the Shell process) and Bi203/Mo03 (used in the Sohio process). In both processes, the reaction is carried out at temperature and pressure ranges of 300-360°C and 1-2 atmospheres. In the Sohio process, a mixture of propylene, air, and steam is introduced to the reactor. The hot effluent is quenched to cool the product mixture and to remove the gases. Acrylic acid, a by-product from the oxidation reaction, is separated in a stripping tower where the acrolein-acetaldehyde mixture enters as an overhead stream. Acrolein is then separated from acetaldehyde in a solvent extraction tower. Finally, acrolein is distilled and the solvent recycled. 

There are several ways to produce acrylic acid. Currently, the main process is the direct oxidation of acrolein over a combination molybdenum-vanadium oxide catalyst system. In many acrolein processes, acrylic acid is made the main product by adding a second reactor that oxidizes acrolein to the acid. The reactor temperature is approximately 250°C ... 

The production of acrylic acid from the oxidative carhonylation of ethylene is descrihed in Chapter 7. 

Much like the oxidation of propylene, which produces acrolein and acrylic acid, the direct oxidation of isobutylene produces methacrolein and methacrylic acid. The catalyzed oxidation reaction occurs in two steps due to the different oxidation characteristics of isobutylene (an olefin) and methacrolein (an unsaturated aldehyde). In the first step, isobutylene is oxidized to methacrolein over a molybdenum oxide-based catalyst in a temperature range of 350-400°C. Pressures are a little above atmospheric ... 

Composite proplnts, which are used almost entirely in rocket propulsion, normally contain a solid phase oxidizer combined with a polymeric fuel binder with a -CH2—CH2— structure. Practically speaking AP is the only oxidizer which has achieved high volume production, although ammonium nitrate (AN) has limited special uses such as in gas generators. Other oxidizers which have been studied more or less as curiosities include hydrazinium nitrate, nitronium perchlorate, lithium perchlorate, lithium nitrate, potassium perchlorate and others. Among binders, the most used are polyurethanes, polybutadiene/acrylonitrile/acrylic acid terpolymers and hydroxy-terminated polybutadienes... 

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