Dimethyl terephthalate hydrogenation

Manufacture. The manufacture of 1,4-cyclohexanedimethanol can be accompHshed by the catalytic reduction under pressure of dimethyl terephthalate ia a methanol solution (47,65). This glycol also may be prepared by the depolymerization and catalytic reduction of linear polyesters that have alkylene terephthalates as primary constituents. Poly(ethylene terephthalate) may be hydrogenated ia the presence of methanol under pressure and heat to give good yields of the glycol (see Polyesters) (66,67). 

Some time earlier, Eastman-Kodak has been working on a novel polyester as an entry into the important polyester fiber market and had devised a new ahcychc diol, 1,4-cydohexanedimethanol [105-08-5] effectively made by exhaustive hydrogenation of dimethyl terephthalate. Reaction of the new diol with dimethyl terephthalate gave a crystalline polyester with a higher melting point than PET and it was introduced in the United States in 1954 as a new polyester fiber under the trade name Kodel (5). Much later the same polyester, now called PCT, and a cyclohexanedimethanol—terephthalate/isophthalate copolymer were introduced as mol ding resins and thermoforming materials (6). More recentiy stiU, copolymers of PET with CHDM units have been introduced for blow molded bottie resins (7). 

Cyclohexanedimethanol (47) starts from dimethyl terephthalate. The aromatic ring is hydrogenated in methanol to dimethyl cyclohexane-l,4-dicarboxylate (hexahydro-DMT) and the ester groups are further reduced under high pressure to the bis primary alcohol, usually as a 68/32 mixture of trans and cis forms. The mixed diol is a sticky low melting soHd, mp 45—50°C. It is of interest that waste PET polymer maybe direcdy hydrogenated in methanol to cyclohexanedimethanol (48). 

The product mixture, consisting mainly of p-toluic acid, monomethyl terephtha-late, and some terephthalic acid, is esterified and methyl p-toluate is recycled after separation from the end-product dimethyl terephthalate. The special advantage of cooxidation is that the hydroperoxy radical (111) formed in the autoxidation of p-xylene participates in initiation through hydrogen abstraction from methyl p-toluate, thus promoting oxidation of the latter ... 

Conventional uses of methanol account for 90% of present consumption and include formaldehyde, dimethyl terephthalate, methyl methacrylate, methyl halides, methylamines and various solvent and other applications. Newer uses for methanol that have revitalized its growth and outlook include a new technology for acetic acid, single cell protein, methyl tertiary butyl ether-(MTBE), and water denitrification. Potential uses for methanol include its use as a carrier for coal in pipelines, as a source of hydrogen or synthesis gas used in direct reduction of iron ore, as a direct additive to or a feedstock for gasoline, peak power shaving and other fuel related possibilities. Table II lists the world methanol demand by end use in 1979. 

Process Economics Program Report SRI International. Menlo Park, CA, Isocyanates IE, Propylene Oxide 2E, Vinyl Chloride 5D, Terephthalic Acid and Dimethyl Terephthalate 9E, Phenol 22C, Xylene Separation 25C, BTX, Aromatics 30A, o-Xylene 34 A, m-Xylene 25 A, p-Xylene 93-3-4, Ethylbenzene/Styrene 33C, Phthalic Anhydride 34B, Glycerine and Intermediates 58, Aniline and Derivatives 76C, Bisphenol A and Phosgene 81, C1 Chlorinated Hydrocarbons 126, Chlorinated Solvent 48, Chlorofluorocarbon Alternatives 201, Reforming for BTX 129, Aromatics Processes 182 A, Propylene Oxide Derivatives 198, Acetaldehyde 24 A2, 91-1-3, Acetic Acid 37 B, Acetylene 16A, Adipic Acid 3 B, Ammonia 44 A, Caprolactam 7 C, Carbon Disulfide 171 A, Cumene 92-3-4, 22 B, 219, MDA 1 D, Ethanol 53 A, 85-2-4, Ethylene Dichloride/Vinyl Chloride 5 C, Formaldehyde 23 A, Hexamethylenediamine (HMDA) 31 B, Hydrogen Cyanide 76-3-4, Maleic Anhydride 46 C, Methane (Natural Gas) 191, Synthesis Gas 146, 148, 191 A, Methanol 148, 43 B, 93-2-2, Methyl Methacrylate 11 D, Nylon 6-41 B, Nylon 6,6-54 B, Ethylene/Propylene 29 A, Urea 56 A, Vinyl Acetate 15 A. 

Ziegler catalysts prepared from nickel or cobalt 2-ethylhexanoate and triethylaluminum (3 or 4 1 ratio) are very efficient for the hydrogenation of aromatic compounds.o-Xylene (51) gives a mixture of cis- (52) and trans-1,2-dimethylcyclohexane (53) in 65 35 ratio. Phenol (54), dimethyl phthalate and dimethyl terephthalate are also reduced in high yield, while nitro-substituted benzene and phenols cannot be reduced. Catalytic activity toward benzene hydrogenation decreases in the order Ni > Co > Fe > Cr > Cu. ... 

Fig. 21.5 The one-step hydrogenation of dimethyl terephthalate to 1,4-cyclodimethanol using a [Aul] trimetalhc Ru PtSn nanocluster catalyst...

Use Manufacture of formaldehyde, acetic acid, and dimethyl terephthalate chemical synthesis (methyl amines, methyl chloride, methyl methacrylate) antifreeze solvent for nitrocellulose, ethylcellulose, polyvinyl butyral, shellac, rosin, manila resin, dyes denaturant for ethanol dehydrator for natural gas fuel for utility plants (methyl fuel) feedstock for manufacture of synthetic proteins by continuous fermentation source of hydrogen for fuel cells home-heating-oil extender. 

It can be obtained by depolymerization and hydrogenation of polyethylene terepb-thalate in the presence of methanol, but it is produced industrially by Tenttessee Eastman from dimethyl terephthalate. 

Cr -modified Zr09 has been used for the hydrogenation of a variety of aromatic carboxylic acids the results are given in Table 3. Alkyl- and phenoxy-substituted benzoic acids are hydrogenated to the corresponding aldehydes with selectivity up to 95%. Terephthalaldehyde and 4-carbomethoxybenzaldehyde are formed by hydrogenation of dimethyl terephthalate. 

The next most important demand for methyl alcohol is as a raw material in the synthesis of many important organic compounds, including formaldehyde acetic acid chloro-methanes, compounds in which the hydroxyl group and/or one or more hydrogen has been replaced by fluorine, chlorine, bromine, and/or iodine methyl methacrylate, a compound from which acrylic plastics are made methylamines, the source of another important class of plastics, dimethyl terephthalate, the monomer for yet another class of plastics and other products. 

Poly(butylene terephthalate) (PBT) was melt compounded at 230°C with ClOA (MMT preintercalated with dimethyl benzyl hydrogenated tallow ammonium) [Wu et al., 2005a]. The clay concentration was 0 to 8 wt% and dooi = 3.4 to 3.7 nm thus, CPNC was only intercalated. The linear viscoelastic region was observed for y < 0.01... 

We noted previously that aldehydes such as benzaldehyde can be prepared by direct oxidation of the side chain in the reactant. It is also possible to go from the opposite direction and reduce a carboxylic acid to the corresponding aldehyde. In both cases, side-chain halogenation using hazardous chemicals is avoided. A one-step direct hydrogenation process has been developed by Mitsubishi using a Cr modified zirconia catalyst (Yokoyama et al., 1992), which is reported to give aldehyde selectivities of 80-97% in the hydrogenation of benzoic acid, o-methylbenzoic acid, w-phenoxybenzoic acid, dimethyl terephthalate, etc. 

C40-60 pareth-3 C40-60 pareth-10 1,10-Decanediol 1,2-Diaminocyclohexane N,N-Diethylcyclohexylamine Diethyl toluene diamine Diisobutyl phthalate Dimer acid, hydrogenated Dimethylaminomethyl phenol Dimethyl terephthalate... 

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