Terephthalic acid dinitrile

Lummus has developed an ammoxidation process, in which p-xylene is transformed into terephthalic acid dinitrile with ammonia on vanadium catalysts. The terephthalic acid dinitrile is then hydrolysed into the free acid. 

Terephthalic acid dinitrile refluxed 172 hrs. with Na-azide and LiCl in glycol monomethyl ether 1,4-di-(5-tetrazolyl)benzene (Y 91%) refluxed 2 hrs. with... 

Polyesters have been synthesized by the reaction of glycols with the diammonium or bis(triethylammonium) salts or fV-methylpyrrolidone complexes of dibasic acids. Dicarboxamides or dinitriles also react with glycols to form polyesters. Alkylene halides and salts of terephthalic acid react to give polyesters. In general, however, all these reactions give low-molecular-weight products, and no kinetic studies have been made. 

From a more preictical point of view it would be necessary to follow the reaction to higher mean residence times. Only for a higher yield of dinitrile with increa.sing residence time a practical application of this way to terephthalic acid is possible. The main advantage of the proposed route compared to the known processes would be the unification of isomer separation and reaction in one step. 

In a process developed by Lummus, / -xylene and ammonia are converted to terephthalonitrile in a fluidized bed at 450°C. A supported vanadium pentoxide catalyst is used and gives about 50% conversioa The vanadium pentoxide is reduced during the reaction and can be reoxidized with air in a separate reactor. The dinitrile is then hydrolyzed to terephthalic acid. The process has not been used in polyester production, although a similar process used in Japan produces diamines from terephthalonitrile or isophthalonitriles. 

Only one fiber and a series of thermoplastic copolyureas are manufactured commercially. For the fiber, one starts with 1,9-nonane diamine, obtained in the following way Rice-bran oil contains a large amount of oleic acid, (CH3—(CH2)7—CH=CH—(CH2)7—COOH), and linoleic acid, (CH3—azelaic acid (HOOC—(CH2)7—COOH). Ammonia is added to this, then water is eliminated during the formation of 1,7-heptane dinitrile, and 1,9-nonane diamine is obtained from this by hydrogenation. Polynonane urea has a melting point of 240 C and possesses better resistance to alkalis than, for example, poly(ethylene terephthalate). It can be dyed satisfactorily with acid dyestuffs. 

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