Oxidation phthalic anhydride

Subject to resolution of these concerns, scaling in parallel has no obvious limit. Multitubular reactors with 10,000 tubes have been built, e.g., for phthalic anhydride oxidation. 

Formerly, benzoic acid was produced by the decarboxylation of phthalic anhydride. Oxidation of acetophenon, benzyl bromide, and toluene with sulfur and water has been described in the literature, but are not commercially feasible routes of synthesis. Carboxylation of benzene with carbon dioxide is not practical due to the instability of benzoic acid at the required reaction conditions [8]. 

These few examples show an advantage of anaerobic oxidations for selected reactions, to minimize CO2 formation. A few other opportunities for further study should include the oxidation of o-xylene to phthalic anhydride, oxidative dehydrogenation of ethylbenzene to styrene, oxidation of isobutylene to methacrolein and methacrylic acid, and oxidative dehydrogenation of paraffins to olefins. 

Example 13.1 Phthalic anhydride is an important intermediate for the plastics industry. Manufacture is by the controlled oxidation of o-xylene or naphthalene. The most common route uses o-xylene via the reaction... 

Figure 13.5 shows a flowsheet for the manufacture of phthalic anhydride by the oxidation of o-xylene. Air and o-xylene are heated and mixed in a Venturi, where the o-xylene vaporizes. The reaction mixture enters a tubular catalytic reactor. The heat of reaction is removed from the reactor by recirculation of molten salt. The temperature control in the reactor would be diflficult to maintain by methods other than molten salt. 

It was first described in 1608 when it was sublimed out of gum benzoin. It also occurs in many other natural resins. Benzoic acid is manufactured by the air oxidation of toluene in the liquid phase at 150°C and 4-6 atm. in the presence of a cobalt catalyst by the partial decarboxylation of phthalic anhydride in either the liquid or vapour phase in the presence of water by the hydrolysis of benzotrichloride (from the chlorination of toluene) in the presence of zinc chloride at 100°C. 

Phthalic Anhydride Recovery and Purification. The accepted method of recovering phthalic anhydride from vapor-phase oxidation... 

Henkel Rearrangement of Benzoic Acid and Phthalic Anhydride. Henkel technology is based on the conversion of benzenecarboxyhc acids to their potassium salts. The salts are rearranged in the presence of carbon dioxide and a catalyst such as cadmium or zinc oxide to form dipotassium terephthalate, which is converted to terephthahc acid (59—61). Henkel technology is obsolete and is no longer practiced, but it was once commercialized by Teijin Hercules Chemical Co. and Kawasaki Kasei Chemicals Ltd. Both processes foUowed a route starting with oxidation of napthalene to phthahc anhydride. In the Teijin process, the phthaHc anhydride was converted sequentially to monopotassium and then dipotassium o-phthalate by aqueous recycle of monopotassium and dipotassium terephthalate (62). The dipotassium o-phthalate was recovered and isomerized in carbon dioxide at a pressure of 1000—5000 kPa ( 10 50 atm) and at 350—450°C. The product dipotassium terephthalate was dissolved in water and recycled as noted above. Production of monopotassium o-phthalate released terephthahc acid, which was filtered, dried, and stored (63,64). 

Hydroxyphthalazin-l(2//)-one is obtained in a smooth reaction between phthalic anhydride and hydrazine hydrate and this is again the starting compound for many 1-substituted and/or 1,4-disubstituted phthalazines. The transformations of 1,4-dichloro-phthalazine, which is prepared in the usual manner, follow a similar pattern as shown for pyridazines in Scheme 110. On the other hand, phthalonitrile is the preferential starting compound for amino- and hydrazino-phthalazines. The most satisfactory synthesis of phthalazine is the reaction between a,a,a, a -tetrachloro-o-xylene and hydrazine sulfate in sulfuric acid (67FRP1438827), alt iough catalytic dehalogenation of 1-chloro- or 1,4-dichloro-phthalazine or oxidation of 1-hydrazinophthalazine also provides the parent compound in moderate yield. 

Phthalic anhydride. Naphthalene is oxidized by air to phthalic anhydride in a Bubbling flmdized reaclor. Even though the naphthalene feed is in liquid form, the reaction is highly exothermic. Temperature control is achieved by removing heat through vertical tubes in the bed to raise steam [Graham and Way, Chem. Eng. Prog., 58, 96 (Januaiy 1962)]. 

Toluene hydrodealkylation to benzene and methane Phthalic anhydride by air oxidation of naphthalene Trickle bed reactor for hydrodesulfurizatiou... 

Quinizarin has been prepared by heating /)-chlorophenol, phthalic anhydride, and sulfuric acid by heating hydroquinone with phthalic anhydride - by heating hydroquinone, phthalic anhydride and c.i>. sulfuric acid by oxidizing anthraquinone... 

Cataljdic reactions performed in fluid beds are not too numerous. Among these are the oxidation of o-xylene to phthalic anhydride, the Deacon process for oxidizing HCl to CI2, producing acrylonitrile from propylene and ammonia in an oxidation, and the ethylene dichloride process. In the petroleum industry, cataljdic cracking and catalyst regeneration is done in fluid beds as well as some hydroforming reactions. 

The prime function of the saturated acid is to space out the double bonds and thus reduce the density of cross-linking. Phthalic anhydride is most commonly used for this purpose because it provides an inflexible link and maintains the rigidity in the cured resin. It has been used in increasing proportions during the past decade since its low price enables cheaper resins to be made. The most detrimental effect of this is to reduce the heat resistance of the laminates but this is frequently unimportant. It is usually produced by catalytic oxidation of o-xylene but sometimes naphthalene and is a crystalline solid melting at 131°C. 

Currently, phthalic anhydride is mainly produced through catalyzed oxidation of o-xylene. A variety of metal oxides are used as catalysts. A typical one is V2O5 -1- Ti02/Sb203. Approximate conditions for the vapor-phase oxidation are 375-435°C and 0.7 atmosphere. The yield of phthalic anhydride is about 85% ... 

Cyclohexadiene has been prepared by dehydration of cyclohexen-3-ol,3 by pyrolysis at 540° of the diacetate of cyclohexane-1,2-diol,4 by dehydrobromination with quinoline of 3-hromocyclohexene,6 by treating the ethyl ether of cyclohexen-3-ol with potassium bisulfatc,6 7 by heating cyclohexene oxide with phthalic anhydride,8 by treating cyclohexane-1,2-diol with concentrated sulfuric acid,9 by treatment of 1,2-dibromocyclo-hexane with tributylamine,10 with sodium hydroxide in ethylene glycol,10 and with quinoline,6 and by treatment of 3,6-dibromo-cyclohexene with sodium.6... 

The oxidation of dimethyl 3-methyl-3//-3-benzazepine-2,4-dicarboxylate (1) with potassium permanganate in acetone solution brings about destruction of the azepine ring and formation of phthalic anhydride (2).24... 

Phosphorus pentachloride, for conversion of pentaacetylgluconic add to add chloride, 41, 80 for oxidation of cycloheptatriene to tropylium fluoborate, 43, 101 with cyanoacetic acid, 41, 5 Phosphorus tribromide, reaction with 1.5-hexadien-3-ol, 41, 50 Phthalic anhydride, reaction with L-phenylalanine to yield N-phthalyl-L-phenylalanine, 40, 82 Phthalic monoperacid, 42, 77 N-Phthalyl-i.-alanine, 40, 84 N-Phthalyl-/3-alanine, 40, 84 N-Phthalylglycine, 40, 84 N-Phthalyl-l-/5-phenylalanine, 40, 82... 

The preferred catalysts are salts of inorganic and organic acids as well as tertiary amines. Phthalic anhydride, succinic anhydride and maleic anhydride are typical acid anhydrides, while ethylene oxide, propylene oxide, epichlorohydrin and phenyl glycidyl ether are typical epoxides. The synthesis of a ladder polymer was carried out by using bisanhydrides264. ... 

Phthalic anhydride will, in the presence of the V2O5 catalyst of Example 9.1, undergo complete oxidation with A772 = — 760kcal/mol. Suppose the complete oxidation is pseudo-first-order in phthalic anhydride concentration and that ln( k//) = 12.300—10,000/T. 

An alternative route to phthalic anhydride is the partial oxidation of naphthalene. The heat of reaction is — 430 kcal/mol. This reaction can be performed using a promoted V2O5 catalyst on silica, much like that considered in Example 9.1. Suppose In(fik) = 31.6800—19,100/T for the naphthalene oxidation reaction and that the subsequent, complete oxidation of phthalic anhydride follows the kinetics of Problem 9.3. Suppose it is desired to use the same reactor as in Example 9.1 but with a,>, = 53g/ m. Determine values for and T aii that maximize the output of phthalic anhydride from naphthalene. 

It is dangerous to prepare phthalic anhydride because of the oxidation exothermicity and risks of accidental catalysis by rust. This reaction forms naphthoquinone as a by-product. This compound may have caused a large number of accidents (that caused the compounds to ignite spontaneously) causing the compounds to combust. These accidents may have been caus by the naphthoquinone oxidation catalysed by iron phthalates, which are present in this reaction. However, it will be seen later that phthalic anhydride can also decompose in certain conditions that may be combined here. 

In the same way, phthalic anhydride gave rise to a violent detonation when it came into contact with copper (II) oxide. 

Ninhydrin (also named 1 2 3-triketoindane or 1 2 3-triketohydrindene hydrate) is prepared most simply from the inexpensive phthalic anhydride (I). The latter is condensed with acetic anhydride in the presence of potassium acetate to give phthalylacetlc acid (II) reaction of the latter with sodium methoxide in methanol yields 1 3-indanedionecarboxylic acid, which is decomposed upon warming with dilute hydrochloric or sulphuric acid to indane-1 3-dione (or 1 3-diketohydrindene) (HI). Selenium dioxide oxidation of (III) affords indane-1 2 3-trione hydrate (ninhydrin) (IV). 

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