Mitsubishi Chemical Industries Limited

Hiroshi Hashizume

Yoshiaki Izumisawa

Tsuneo Kimura

Sigeki Harada

Disclosed herein is a process for producing highly pure terephthalic acid which forms polyesters of a particularly favorable color tone, the process comprising the steps of

Process for producing highly pure terephthalic acid

A process for producing terephthalic acid from p-xylene continuously, wherein p-xylene is oxidized to terephthalic acid by air in the presence of a catalyst containing cobalt, manganese and bromine at a temperature of 180.degree. to 230.degree. C. in a water containing acetic acid solvent in which the concentration of oxygen gas contained in an exhaust gas obtained from the reaction vessel used for oxidizing p-xylene is 2 to 8% by volume, said process comprising, (a) preparing an oxidation exhaust gas by condensing a gas withdrawn from said reaction vessel for removing condensates from said gas, (b) dividing the prepared oxidation exhaust gas into a discharged gas and a recycled gas, in which the volume ratio of said recycled gas to said discharged gas is 0.3 to 5, said discharged gas being exhausted to the outside of the reaction system, (c) supplying continuously said recycled gas to the liquid phase of said reaction vessel, and (d) carrying out the oxidation reaction of p-xylene under reaction pressure higher than the pressure of the reaction system when gas is not recycled to the system.

Process for preparing terephthalic acid by the catalytic oxidation with

There is disclosed a process for producing terephthalic acid in which the mother liquor of the terephthalic acid slurry resulting from the oxidation of para-xylene, from which terephthalic acid has been separated is subjected to distillation to recover at least a portion of methyl acetate present therein, the recovered methyl acetate being circulated into the reactor.

Process for producing terephthalic acid

There is disclosed a process for the production of terephthalic acid by oxidizing para-xylene with molecular oxygen in which substantially all of the methyl acetate present in the vapor evolved from the reactor is recovered and circulated into the reactor.

A process is disclosed a process for the production of terephthalic acid by oxidizing para-xylene with molecular oxygen in which substantially all of the methyl acetate present in the vapor evolved from the reactor is recovered and circulated into the reactor.

Preparation of terephthalic acid by oxidizing p-xylene with molecular oxygen in an acetic acid solvent in the presence of a catalyst containing at least one heavy metal and bromine. Preparation of terephthalic acid of high purity accompanied by low level of combustion of the acetic acid solvent can be achieved by

Process for preparing terephthalic acid

A purified terephthalic acid is prepared by dissolving a crude terephthalic acid in water at high temperature under high pressure and then contacting the resulting aqueous solution with a catalyst of an active carbon supporting palladium under maintaining the pressure P(kg/cm.sup.2) of the gaseous phase in the catalytic contacting zone in a range of

Process for preparing purified terephthalic acid

A process for the continuous preparation of pure terephthalic acid by oxidation of p-xylene with molecular oxygen in acetic acid solvent comprising conducting the oxidation at a temperature of 205.degree. to 230.degree. C. in the presence of an oxidation catalyst comprising (a) a cobalt compound in an amount of at least 120 ppm and less than 200 ppm as cobalt based on the weight of solvent, (b) a manganese compound sufficient to provide a manganese to cobalt weight ratio of 0.5 to 1.5 and (c) a bromine compound selected from hydrogen bromide, cobalt bromide and manganese bromide in an amount of 200 to 1,000 ppm as bromine based on the weight of solvent, while the water content of the liquid phase of the reaction system is kept at 4 to 14 percent by weight.

There is disclosed a process for producing terephthalic acid in which the reaction temperature range and the proportion of catalyst components of a cobalt compound, a manganese compound and at least one bromine compound are specifically chosen to produce a high grade terephthalic acid suitable for direct polycondensation in the production of polyester.

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Kurashiki, Japan

Hiroshi Hashizume