Terephthalic acid from toluene

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 terephthalic acid from toluene 13.13.1 Henkel 2 process... 

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. 

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. 

Tartaric acid, 114 Terephthalic acid, i7r Tetrabromocresol, 165 7 hiocarbamide, 128 Thiocarbanilamide, 159 Thiocarbanilide, 159 Thiourea, 128 /i-Tolyl bromide, 167 / Tolyl chloride, 165 /-Tolyl cyanide, 169 Tolyliodochloride, 169 Toluene from toluidine, 163 / Toluic acid, 170 Tribromophenol, 180 Trichloracetic acid, 99 Trimethylxanthine, 131 l rinitrophenol, 185 Triphenylguanidine, ito Triphenylmetbane, 2 4 J schugac s hydroxyl method, 223 Tube furnace, 23 Tyrosine, 133... 

Petroleum refineries produce a stream of valuable aromatic compounds called the BTX, or benzene-toluene-xylenes (Ruthven 1984). The Cg compounds can be easily separated from the Ce and C compounds by distillation, and consist of ethyl benzene, o-xylene, m-xylene, and / -xylene. Ethyl benzene is the starting material for styrene, which is used to make polystyrene / -xylene is oxidized to make terephthalic acid, and then condensed with ethylene glycol to make polyester for fibers and films. The buyers of / -xylene are the manufacturers of terephthalic acid, such as BP-Amoco, who in turn sell to the fiber manufacturers such as DuPont and Dow. These are big and sophisticated companies that have strong research and engineering capabilities, and are used to have multiple suppliers. The eventual consumers of adsorbents are the public who consider polyester as one of the choices in fabric and garments, in competition with other synthetic and natural fibers. Their purchases are also dependent on personal income and prosperity. In times of recession, it is always possible for a consumer to downgrade to cheaper fibers and to wear old clothes for a longer period of time before new purchases. 

In the manufacture of terephthalic acid by the oxidation of p-xylene, separation of the xylene from its isomeric mixture is necessary (see Section 2.5.2). An alternative process introduced in Japan uses the oxidation of p-tolualdehyde, which is obtained in good regioselectivity by the HF—BF3 catalyzed carbonylation of toluene without the necessity of separation of the isomers. 

These are benzene, toluene and xylenes, which are some of the basic feedstocks of the chemical industry. The products that can readily be made from them can be found in most industrial chemical texts. The synthetic gasoline has certain advantages, e.g. the yield of p-xylene (the feedstock for terephthalic acid) is enhanced relative to that normally found in petrochemical feedstocks but the overwhelming requirement for octane in the synthetic gasoline stream may make it economically unattractive to attenpt to remove these components. 

The 50 largest-volume chemicals contain many derived from fossil carbon sources. Their 1995 volumes in billions of pounds produced in the United States4 are ethylene (46.97), ammonia (35.60), propylene (25.69), methyl tert-butyl ether (17.62), ethylene dichloride (17.26), nitric acid (17.24), ammonium nitrate (15.99), benzene (15.97), urea (15.59), vinyl chloride (14.98), ethylbenzene (13.66), styrene (11.39), methanol (11.29), carbon dioxide (10.89), xylene (9.37), formaldehyde (8.11), terephthalic acid (7.95), ethylene oxide (7.62), toluene (6.73), p-xylene (6.34), cumene (5.63), ethylene glycol (5.23), acetic acid... 

Cobalt compounds are useful chemical catalysts for the synthesis of fuels (Fi-scher-Tropsch process), the synthesis of alcohols and aldehydes from olefins, hydrogen and carbon monoxide at elevated temperatures and pressures ( oxo process , hydroformylation ). They are also used in petroleum refining and the oxidation of organic compounds. In the oxo process, cobalt carbonyl, Co2(CO)g, is employed or generated in situ. For the selective production of n-butanol from propylene, hydrogen and CO, an organophosphine-modified cobalt carbonyl complex is used as the catalyst. Cobalt salts are proven oxidation catalysts examples include the production of terephthalic acid by the oxidation of p-xylene, and the manufacture of phenol by the oxidation of toluene. 

There arc numerous examples of product selectivity, many of which involve mono-and disubslituted aromatics formed over ZSM-5 (MFI) catalysts (22-24). One of the early examples was xylene isomerization. Xylene can be formed over MFI catalysts via the acid-catalyzed reaction between methanol and toluene (see Fig. 10.3). According to thermodynamics the equilibrium distribution of o-, m-, and p-isomers is 26 51 23, which is different from the industrial demand as the p-isomer is a feedstock for terephthalic acid, a monomer for PET. However, very high selectivities of p-xylene can be obtained over MFT materials primarily because the diffusion of p-xylene is faster in the MFI pores compared to the other two isomers. 

Later stages of the decomposition are characterised by evolution of CO and aromatic species such as toluene, benzoic acid and terephthalic acid. It is also suggested that, unlike PET, there are no primary fragments from PBT-containing carbonyl groups, thus no acetalisation reactions are expected. 

Another alternative to the production of terephthalic acid is the process developed by Mitsubishi Gas Chemical, in which a complex generated from toluene, HF and BF3 is made to react under pressure with carbon monoxide (Gattermann-Koch). After decomposition of the complex, p-methylbenzaldehyde can be recovered by crystallization and may then be oxidized to terephthalic acid. 

Ethylene glycol for the synthesis of PET is obfained by air oxidation of ethylene to ethylene oxide (Section 11.8A) followed by hydrolysis to the glycol (Section 11.9A). Ethylene is, in turn, derived entirely from cracking eifher petroleum or ethane derived from natural gas (Section 2.9A). Terephthalic acid is obtained by oxidation of p-xylene, an aromatic hydrocarbon obtained along with benzene and toluene from catalytic cracking and reforming of naphtha and other petroleum fractions (Section 2.9B). 

Molecular oxygen oxidizes toluene to benzoic acid and p-xylene to terephthalic acid via p-toluic acid. These reactions are catalyzed by [Co(OAc)3] or [Mn(OAc)3]. The Mn salts, less oxidizing than those of Co , catalyze the oxidation of these alkylaromatics, but not the oxidation of alkanes whose redox potentials are higher than those of alkylaromatics. It is probable that the M ions are regenerated from and the ArCH200" radicals (mechanism below). 

Ester groups occur in a wide range of polymers (e.g., polyethylene terephthalate) and in copolymers such as, for example, ethylene vinyl acetate. The classical chemical method for the determination of ester groups, namely, saponification, can be applied to some types of polymer. For example, copolymers of vinyl esters and esters of vinyl esters and esters of acrylic acid, can be saponified in a sealed tube with 2 M sodium hydroxide. The free acids from the vinyl esters were determined by potentiometric titration or gas chromatography. The alcohols formed by the hydrolysis of the acrylate esters were determined by gas chromatography. Vinyl acetate ethylene copolymers can be determined by saponification with 1 N ethanolic potassium hydroxide at 80 C for 3 hours and back titration with standard acid or by saponification with p-toluene sulfonic acid and back titration with standard acetic acid [49, 50]. 

The most important transalkylation from the industrial standpoint is the disproportionation of toluene into benzene and xylenes, especially xylene, since -xylene is a starting material for terephthalic acid, a major component in polyester fibers. 

The alkylation of toluene with methanol has been investigated for many years as a potential alternative route to / - Qflene, ethylbenzene, and styrene. Conventional / -xylene production from petroleum reformate requires costly purification and separation from jQ lene isomers and other aromatics. A process that selectively produces /)-xylene could have a significant commercial impact by eliminating the need for p-xylene separation. Furthermore, styrene or ethylbenzene production from methanol and toluene is desired as part of the development of processes based on Cl feedstocks rather than ethylene or propylene feedstocks [48], Para- xyl ae is used primarily in terephthalic acid production, a major component of polyester manufacture. 

After the oxidation process, the reaction mixture is separated by filtration, into products that are recycled in the same process (toluene, p-tolualdehyde, monomethyltoluate) and removed from this process (HjO, Og and byproducts) and into products that are passed to the esterification reactor (toluic acid, terephthalic acid, monomethylterephthalate and methyl ester of p-benzaldehyde carbonic acid). The latter product does not participate in the esterification reaction, but is passed to this reactor because, being a soUd substance, it remains on the filter at normal temperatures with all the other oxidation products and is passed with them to the esterification cycle, where it circulates as ballast. 

The monomeric imidazole-blocked 1,4-phenyIenediisocyanates with n-alkoxymethyl substituents were prepared from 2,5-bis(n-alkoxymethyI) terephthalic acids by chlorination with oxalyl chloride in DM Ac at 0 C[19 - 21] followed by reaction with aqueous NaN3 as shown in Scheme 1. The isolated azido products were rearranged to isocyanates in the presence of excess imidazole at 85 °C in toluene. On cooling were precipitated the DIS-IBDIs, which were thoroughly purified by recrystallization from acetone. The substituted terephthalic acids were prepared by basic hydroysis of 2,5-bis(n-alkoxymethyl)-terephthalonitriles[17 - 18]. 

The Cg alkylaromatics fraction is formed by ethylbenzene and the three xylene isomers. Ethylbenzene is used as a raw material to produce styrene by dehydrogenation, or oxidative dehydrogenation. Para-xylene and ortho-xylene are catalytically oxidized to give terephthalic and phthalic acid. The meta-xylene isomer can also be oxidized to give isophthalic acid. The major industrial source of these products is the catalytic reforming of naphthas. The Cyclar process, can also produce xylenes from propane and butane. However, using this process, xylenes are formed less selectively than toluene or benzene in the BTX. 

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