Maleic acid recovery

Oxidation of n-butane and butenes requires higher reaction temperatures (400-480°C). Since more water is produced in this reaction, most of the product is recovered in the form of maleic acid. The currently best process is the Alma (Alusuisse) process.1015-1018 Its main features are a fluidized-bed reactor and an anhydrous product recovery. Because of the better temperature control, a lower air hydrocarbon ratio can be employed (4 mol% of n-butane). Instead of absorption in water, maleic anhydride is recovered from the reactor effluent gas by a high-boiling organic... 

Air and n-butane are introduced into a fluid-bed, catalytic reactor (1). The fluid-bed reactor provides a uniform temperature profile for optimum catalyst performance. Reaction gases are cooled and filtered to remove small entrained catalyst particles and then routed to the recovery section. Reactor effluent is contacted with water in a scrubber (2), where essentially 100% of the reactor-made maleic anhydride is recovered as maleic acid. The process has the capability of co-producing maleic anhydride (MAH) with the addition of the appropriate purification equipment. Scrubber overhead gases are sent to an incinerator for safe disposal. 

The resulting maleic acid from the scrubber is then sent directly to the fixed-bed, catalytic hydrogenation reactor (3). Reactor yields exceed 94% BDO. By adjustments to the hydrogenation reactor and recovery-purification sections, mixtures of BDO with THF and/or GBL can be directly produced at comparable, overall yields and economics. 

Figure 2 Creep-recovery tests of chemically treated woods. U, untreated wood Fs, vapor phase formalization F, liquid phase formalization A, acetylation PO, etherification with propylene oxide MG, treatment with maleic acid and glycerol PFl, impregnation with low molecular weight phenol-formaldehyde resin PEG-ICP, impregnation with polyethylene glycol (PEG-IOOO) WPC, formation of a wood- polymer composite (PMMA) WIC, formation of a wood-inorganic material composite.

Malic acid (hydroxybutanedioic acid) is a chemical intermediate and is also used as a food flavor enhancer. It can be made by several routes. U.S. 5,210,295 (to Monsanto) describes a nonenzymatic process. U.S. 4,772,749 (to Degussa) describes recovery of malic acid from the product of enzymatic conversion of fumaric acid. U.S. 4,912,042 (to Eastman Kodak) describes an enzymatic separation process for separating the L- and D-isomers. U.S. 5,824,449 (to Ajinomoto Co.) describes a selective fermentation from maleic acid. Estimate the cost of production of D-malic acid by each process and determine which is cheapest. 

In general, wliat has been said in regard to the oxidation of naphthalene to phthalie anhydride applies to the oxidation of benzene to maleic acid with the exception tliat the volume demand for phthalie anhydride is greater. Somewhat different methods are also used in the recovery of product due to its different nature. 

A new process to manufacture THF and 1,4 butanediol from maleic anhydride is currently slated for start-up by DuPont in Asturias, Spain in 1996. The process involves the oxidation of n-butane in a transport bed reactor to form maleic anhydride. Recovery of maleic anhydride is accomplished by scrubbing with water which converts the anhydride immediately to maleic acid. The maleic acid is then hydrogenated to tetrahydrofuran in a bubble column reactor. By varying operating conditions in the hydrogenation reactor the alternate or coproduction of 1,4 butanediol can be accomplished. 

Equation (1.5) is equivalent to (1.4), except the factor of 2 reflects the use of a 180° pulse, meaning that the magnetization (signal intensity) now should take twice as long to recover as when a 90° pulse is used.The results of the inversion-recovery experiment are illustrated in Figure 1.3, where the recovery of ibuprofen and maleic acid resonances are shown as a series of spectra and as signal intensities (inset) fit to Eq. (1.5). 

Figure 1.3. Inversion-recovery experimental results for determining Tj relaxation times of ibuprofen and maleic add. The spectral region from 5.6 to 7.6 ppm is displayed as a function of the variable delay time t. The t values used were (from left to right across the figure) 0.125s, 0.25s, 0.50s, 1.0s, 2.0s, 4.0s, 8.0s, 16s, 32s, and 64s. The acquisition and processing parameters are the same as for Figure 1.1. The inset shows the signal intensities of the maleic acid peak (5.93 ppm) fit to Eq. (1.5).

Poly (hexamethylenebiguanide) hydrochloride preservative, mouthwashes Bromochlorophene Chlorhexidine digluconate preservative, mucilage Sodium salicylate preservative, nebulizer solutions Potassium bisulfite preservative, nontherapeutic 8-Hydroxyquinoline preservative, nonwovens Poly (hexamethylenebiguanide) hydrochloride preservative, NR latex Tetramethylthiuram disulfide Zinc diethyidithiocarbamate preservative, oil field chemicals Dimethyl oxazolidine preservative, oil recovery Tributyltin oxide preservative, oils Maleic acid... 

As an introduction, our previous studies on the conformations of maleic acid copolymers with aromatic vinyl monomers are summarized. To characterize the compact form and the pH-indueed conformational transition of the maleic acid copolymer with styrene in aqueous NaCl, 400 MHg H-NMR spectra were measured. The spectral form depended on the molecular conformation. Because each of proton resonance peaks could not be separated, the spin-lattice relaxation time T was estimated by using the inversion recovery technique (tf-t-tf/2). The T s for both side chain and backbone protons reflected the transition, and the protons were considered to be in a more restricted motional state in the compact form than in the coil form. Also, from temperature dependence of each Tj, motion of the copolymer in the coil form was described in terms of the local segmental jump (D) combined with the isotropic rotational motion (O), when a ratio between both the correlation times tq and Tq was about 0.07. For the compact form, the ratio was found to be about 10. By referring to theoretical diagram of Tj vs. tq for the methylene protons on the backbone, value of Tn for the compact form was compared with that for the coil form at 35 C. 

When 40.4 mg of maleic acid was added to 4 g of the anhydride, 47.1 mg was recovered, indicating the sample contained 0.1% maleic acid (Fig. 4). Recovery of maleic acid from a 28.60 acid in anhydride mixture was 100.1. ... 

After the primary recovery of MA during production, the remaining MA is recovered as maleic acid by scrubbing with water. Some of this can be and often is converted to fumaric acid. High-purity fumaric acid for food applications is made from refined MA. The isomerization may be brought about in a number of ways, e.g., thermal, yy (7i,83) catalytic. Aqueous solutions containing 40% maleic acid when heated to form fumaric... 

In the aqueous recovery, generally a 40% solution of maleic acid is used in the scrubber. As mentioned earlier, aqueous recovery is a part of most of the processes and is used after a primary collection. The aqueous solution so produced is either used for recovering MA (see below) or may be converted to fumaric acid by thermal isomerization (Chapter 1). 

Where water is a part of the recovery system as in maleic acid solution, water is removed by azeotropic distillation. Appropriate care is taken to... 

An aqueous maleic acid solution on heating above 70 C yields fumaric acid by isomerization. This can be taken advantage of to produce fumaric acid. (See Chapter 1.) However, the demand for 5 is not high. As a result, where aqueous recovery is necessary (second stage in most benzene processes or in all C4 processes), extreme care is taken to prevent excessive heat treatment of maleic acid solutions. 

This process is a modification of the basic Ruhrol process. The recovery system is similar to SD, i.e., part of the effluent is recovered as molten MA and part as an aqueous maleic acid solution. The latter is dehydrated by azeotropic distillation with xylenes (Fig. 2-3). Benzene in the exhaust gases is removed in absorbers, making it odor free. 

As can be seen from the foregoing, permaleic acid is an excellent reagent where a peracid is called for. Especially in the Bacyer-Villiger oxidation, it may be the reagent of choice. Recovered maleic acid can be recycled easily and, as mentioned earlier, the recovery is facilitated by the insolubility of the acid in the reaction medium. 

If the only concern is the identification of the dialkyl groups attached directly to tin, then a method using methanolic sodium hydroxide solution is recommended (Figure 7.9). The thin-layer chromatographic method described is also suitable. For pure samples of dialkyltin carboxylates with no ester present, the time of reflux with alkali can usually be much reduced, the recovery and identification of the dialkyltin oxide, believed to be in polymeric form, still being quite satisfactory. In addition, maleic acid can be recovered fi om a sample of dibutyltin maleate after decomposition by this simplified method. 

The reaction of alkyl bromides with alcohols to form ethers, promoted by silver salts of dicarboxylic acids, the Koenigs-Knorr synthesis, is sometimes complicated by the recovery of the ether from the dicarboxylic acid. A copolymer network of maleic acid and l,4-bis(vinyloxy)butane was transformed into the silver salt (41) and used for the reaction of 2,3,4,6-tetra-O-acetyl-la-bromoglucopyranose with cholesterol to give the cholesteryl ether in 55% yield as shown in Scheme The polymeric by-product dicarboxylic acid was filtered easily from the product solution. 

Separation of benzene/cyclohexane mixture is investigated most extensively. This is not surprising because separation of this mixture is very important in practical terms. Benzene is used to produce a broad range of valuable chemical products styrene (polystyrene plastics and synthetic rubber), phenol (phenolic resins), cyclohexane (nylon), aniline, maleic anhydride (polyester resins), alkylbenzenes and chlorobenzenes, drugs, dyes, plastics, and as a solvent. Cyclohexane is used as a solvent in the plastics industry and in the conversion of the intermediate cyclohexanone, a feedstock for nylon precursors such as adipic acid. E-caprolactam, and hexamethylenediamine. Cyclohexane is produced mainly by catalytic hydrogenation of benzene. The unreacted benzene is present in the reactor s effluent stream and must be removed for pure cyclohexane recovery. 

The monomer conversion using the mixture of styrene and maleic anhydride is much higher than in the other cases. This value does not truly represent monomer conversion but, instead, the amount of monomer not lost during treatment. Thus, both reacted monomers and non-volatilized monomers are present in the reported value. The values obtained with maleic anhydride alone represent a large amount of unreacted maleic anhydride, as indicated by the amount extracted and the acid value of the polymer after extraction. In any event, the recovery with styrene-maleic anhydride is considerably higher than in all the other cases. 

A transformation showing enhancement of the reactivity of phenol through transition metal complexation occurs in the reaction of [Os(NH3)s(fi -phenol]-(OTO2 with maleic anhydride in acetonitrile over 20 hours at ambient temperature followed by recovery of the product, dimethyl (4-hydroxyphenyl)succinate in 85% yield by simple ethereal precipitation and removal of the osmium by refluxing in acidic methanol (ref.39). These last two examples illustrate the versatility of the appropriately modified phenolic structure to function either in a nucleophilic or in an electrophilic manner. 

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