Abstract: A process for producing terephthalic acid, which comprises dissolving crude terephthalic acid in an aqueous medium, contacting it with a platinum group metal catalyst for purification under a temperature condition of from 260.degree. to 320.degree. C., crystallizing terephthalic acid from the aqueous solution of terephthalic acid by cooling the aqueous solution stepwise in a plurality of crystallizers connected in series, in such a manner that in a first crystallization zone, the crystallization temperature is adjusted to a level within a range of from 240.degree. to 260.degree. C. and agitating is carried out by impeller with a power requirement of impeller within a range of from 0.4 to 10 kw/m.sup.3, and then, in a second crystallization zone, the crystallization temperature is adjusted to a level within a range of from 180.degree. to 230.degree. C., which is lower by from 20.degree. to 60.degree. C.

Abstract: A process for preparing an aqueous slurry of terephthalic acid, which comprises oxidizing p-xylene with molecular oxygen in a liquid phase in an acetic acid solvent in the presence of a catalyst, to obtain an acetic acid slurry of terephthalic acid, separating terephthalic acid crystals from the acetic acid slurry, washing the terephthalic acid crystals containing acetic acid, with p-xylene or an acetic acid ester, and then mixing water thereto.

Abstract: A process for producing highly pure terephthalic acid, which comprises heating and dissolving crude terephthalic acid in water, and purifying it by contacting the aqueous solution with hydrogen at a temperature of from 260.degree. to 320.degree. C. in the presence of a platinum group metal catalyst, wherein the purification is initiated within three minutes after the aqueous solution under heating reaches a temperature of 250.degree. C.

Abstract: The present invention provides a process of preparing terephthalic acid of high quality which is characterized by:oxidizing p-xylene with molecular oxygen in an acetic acid solvent in the presence of a catalyst comprised of at least one heavy metal and bromine at a temperature of from 180.degree. to 230.degree. C. to convert at least 95 wt % of the p-xylene into terephthalic acid and, optionally, subjecting the resultant reaction mixture to low temperature post-oxidation with molecular oxygen at temperatures lower than the temperature of the first oxidation reaction, thereby obtaining a slurry containing terephthalic acid particles whose spectral reflectance defined below is not less than 70% and whose reflectance ratio (400/500) defined below is not less than 0.92;subjecting the slurry to high temperature post-oxidation with molecular oxygen at a temperature of from 235.degree. to 290.degree. C. and then to crystallization; andcollecting the resultant terephthalic acid from the reaction mixture.

Abstract: 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 ofoxidizing p-xylene, thereby obtaining a mixture containing terephthalic acid,subsequently further oxidizing the thus obtained mixture at not higher temperature than that of the first oxidation step,still further oxidizing the reaction mixture of the second oxidation step at a higher temperature than that of the first oxidation step andtreating the reaction mixture obtained by the third step of oxidation by bringing thereof into contact with molecular oxygen.

Abstract: A process for producing an orthoalkylphenol which comprises reacting phenol with an olefin in a liquid phase in the presence of an alumina catalyst, characterized in that the water content in the liquid phase of the reaction system is maintained at a level of not higher than 250 ppm.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.