Xylenes terephthalic acid from

Manizen (1) A process for making terephthalic acid from/>-xylene. Similar to the Amoco process but yielding a purer product in one stage. Operated in Japan by Matsuyama Chemical Company. 

Phthalic acid (1,2-benzene dicarboxylic acid), isophthalic acid (1,3-benzene dicarboxylic acid), and terephthalic acid (1,4-benzene dicarboxylic acid) are made by the selective oxidation of the corresponding xylenes. Terephthalic acid may also be produced from the oxidation of naphthalene and by the hydrolysis of terephthalonitrile. 

Liquid phase oxidation of hydrocarbons by molecular oxygen forms the basis for a wide variety of petrochemical processes,3 "16 including the manufacture of phenol and acetone from cumene, adipic acid from cyclohexane, terephthalic acid from p-xylene, acetaldehyde and vinyl acetate from ethylene, propylene oxide from propylene, and many others. The majority of these processes employ catalysis by transition metal complexes to attain maximum selectivity and efficiency. 

Terephthalic Acid from Toluene. Both carbon monoxide and methanol can react with toluene to yield intermediates that can be oxidized to terephthalic acid. In work conducted mainly by Mitsubishi Gas Chemical Company (62,63), toluene reacts with carbon monoxide and molar excesses of HF and BF3 to yield a jtanz-tolualdehyde—HF—BF3 complex. Decomposition of this complex under carefully controlled conditions recovers HF and BF3 for recycle and ra-tolualdehyde, which can be oxidized in place of para-xyiene to yield terephthalic acid. One drawback of the process is the energy-intensive, and therefore high cost, decomplexing step. The need for corrosion-resistant materials for construction and the need for extra design features to handle the relatively hazardous HF and BF3 also add to the cost. This process can be advantageous where toluene is available and xylenes are in short supply. 

Production of acids (i) terephthalic acid from p-xylene, (ii) acetic acid from n-butane,... 

The primary example is the production of terephthalic acid from p-xylene which is used in the production of polyethylene(terephthalate). A recent review describes the oxygenation of at least 251 hydrogens to give 279 products using at least 35 different catalyst combinations. There are a number of reports which include cerium as one of the elements... 

Production of terephthalic acid from o-xylene, Henkel 1 process... 

Metal-ion catalysed air oxidations of aromatic compounds are industrially important. Oxidation of a methyl to a carboxylic acid group, such as in the first stage of the manufacture of terephthalic acid from p-xylene, is believed to involve peroxidation of benzylic carbon [formed in eqn (29)] (Andrulis et al., 1966). The reactions leading to benzyl acetates [eqns (29)-(31) for example] must therefore be carried out in the absence of air. Oxidations of alkylaromatics in the presence of oxygen and involving cation radical intermediates have been reported (Onopchenko et al., 1972 Holtz, 1972 Scott and Chester, 1972). 

Terephthalic acid from p-xylene Co(II), Mn(II) salts, bromide ion... 

This method has been licensed world-wide to prepare terephthalic acid from p-xylene. We have used the reaction of m-chloroperbenzoic acid (MCPBA) with mixtures of Co(II) acetate/ Mn(II) acetate/bromide in acetic acid/water solutions to understand the functions of each catalyst component. The sequence of redox reactions that occurs is first the reaction of MCPBA with Co(n) to give Co(III) Co(III) then oxidizes Mn(II) to Mn(III) and finally, Mn(III) oxidizes bromide to bromine. Some of the functions of each component are 1) the cobalt rapidly reacts (very selectively) with the MCPBA (Mn and Br react slowly), 2) Mn lowers the steady state of Co(III) which significantly reduces solvent decomposition and also avoids Co(III) re-arranging into a less reactive form, and 3) bromine reacts rapidly with the methylaromatic compound to generate methylaromatic radicals (Co(III) and Mn(III) react slowly). The dimeric structure of Co(II) in acetic acid is partly responsible for the highly selective nature of the MCPBA oxidation of Co(II). The order of the redox reactions is the opposit to that expected from thermodynamics. 

Whereas benzene and toluene serve as the raw materials for a wide range of products, applications for the three xylene isomers, o-, m- and p-xylene, are basically limited to chemicals arising through oxidation, i.e. phthalic anhydride (PA) from o-xylene, isophthalic acid from m-xylene and terephthalic acid from p-xylene. 

In addition to the use of p-xylene as a raw material in the production of tere-phthalic acid, processes were also operated in the past to produce terephthalic acid from toluene and phthalic anhydride. 

We will begin with the carbonylation of Mel which in situ is generated from MeOH for acetic acid production because of its industrial importance. Acetic acid is an important chemical commodity with a wide range of appUcations in organic chemistry. In organic synthesis, acetic acid is mainly used as a raw material for vinyl acetate monomers and acetic anhydride synthesis, as well as a solvent for producing terephthalic acid from xylene via the oxidation process. In 1998 the world s capacity of acetic acid production was approximately 7.8 milUon tons, of which more than 50 % were produced by BP-Amoco and Celanese. 

Toray Company in Japan and Virent Company in the United States have produced terephthalic acid from para-xylene and MEG, which were made from organic sources. Gevo Company in the United States can produce terephthalic acid and MEG from sugars, starches, and cellulosic materials via para-xylene and isobutanol intermediates (Gevo 2011 Toray 2011 Virent 2011). 

Hamley, R, Ilkenhans, T., Webster, J., et al. (2002). Selective partial oxidation in supercritical water the continuous generation of terephthalic acid from para-xylene in high yield. Green Chem., 4, pp. 235-238. 

Fig. 22.45. Fiber-grade terephthalic acid from p-xylene and methanol. (Reproduced from Hydrocarbon Processing, p. 171, Nov. 1985 copyright 1985 by Gulf Publishing Co.)...

A variety of transition metal ions accelerate the oxidative degradation of the carbon-chain polymers by catalysing both the formation and the decomposition of hydroperoxides. Typically, cobalt-catalysed oxidation of hydrocarbons is used in the manufacture of terephthalic acid from p-xylene. These prooxidant reactions also accelerate the breakdown of polymer molecules to smaller fragments (see Fig. 12.2) but are effectively inhibited by metal deactivators. All antioxidants have some retarding effect, but the most effective are the peroxide decomposers (PD) that remove hydroperoxides as they are formed by ionic (non-free radical) reactions.Deactivated transition metal ions (e.g. 

Decarbonylation of aromatic aldehydes proceeds smoothly[71], Terephthalic acid (86), commercially produced by the oxidation of p-.xylene (85), contains p-formylbenzoic acid (87) as an impurity, which is removed as benzoic acid (88) by Pd-catalyzed decarbonylation at a high temperature. The benzoic acid produced by the decarbonylation can be separated from terephthalic acid (86) based on the solubility difference in water[72]. 

This is called a technical or cmde grade of terephthaUc acid, but the purity is typically greater than 99%. It is not, however, pure enough for the poly(ethylene terephthalate) made from it to reach the required degree of polymerization. The main impurity is 4-formylbenzoic acid [619-66-9] which is incompletely oxidized -xylene and is monofunctional with regard to esterification. 4-Formylbenzoic acid is usually referred to as 4-carboxybenzaldehyde (4-CBA) in the industry. 

An example of this is the commercial process for preparing puru-xylene, the precursor to terephthalic acid, which is polymerised to give polyjethy-lene terephthalate) (PET). In this case, the mixture of xylenes obtained from crude oil is reacted in a zeolite (known as HZSM5). The relative rates of diffusion in and out of the pores are sufficiently different (by a factor of about ten thousand) to allow the extremely efficient and selective conversion of all the isomers to the desired paia isomer, which is the narrowest and can thus move through the structure most rapidly (Figure 4.3). 

The Sandoz company used the dibromoterephthalic acid method. This acid was made from p-xylcnc by brominating it to form 2,5-dibromo-p-xylene and then oxidising this to 2,5-dibromoterephthalic acid. Reaction of one mole of this acid with two moles of an arylamine in the presence of copper(II) acetate gives 2,5-bis(arylamino)terephthalic acid, which can be ring-closed to a linear quinacridone. Unsymmetrical substitution using two different arylamines is possible. 

Meanwhile attempts to find an air oxidation route directly from p-xylene to terephthalic acid (TA) continued to founder on the relatively high resistance to oxidation of the /Moluic acid which was first formed. This hurdle was overcome by the discovery of bromide-controlled air oxidation in 1955 by the Mid-Century Corporation [42, 43] and ICI, with the same patent application date. The Mid-Century process was bought and developed by Standard Oil of Indiana (Amoco), with some input from ICI. The process adopted used acetic acid as solvent, oxygen as oxidant, a temperature of about 200 °C, and a combination of cobalt, manganese and bromide ions as catalyst. Amoco also incorporated a purification of the TA by recrystallisation, with simultaneous catalytic hydrogenation of impurities, from water at about 250 °C [44], This process allowed development of a route to polyester from purified terephthalic acid (PTA) by direct esterification, which has since become more widely used than the process using DMT. 

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