Abstract: A process for the purification of terephthalic acid in which a dispersion of the terephthalic acid in a liquid dispersant such as acetic acid is continuously pumped repeatedly through a cycle. Fresh dispersion is fed continuously into the cycle while simultaneously a corresponding amount of treated dispersion is removed. The cycle comprises a heater and a cooler and the cooler serves as a crystallizer. The dispersion prior to entering the heater is subjected to a highly effective particle comminution and is exposed upstream of or in the heater to an oxygen containing gas such as air. The acetic acid dispersant is removed from the treated dispersion and recycled to the cycle.

Abstract: Method and apparatus for the metered conveying of pulverulent solids with the aid of an eccentric screw pump. The pulverulent solids such as terephthalic acid (TPA) are mechanically or pneumatically loosened in the receiving chamber of the pump.

Abstract: An improvement in the liquid phase air oxidation process based upon a solvent system such as acetic acid and with a bromine activated heavy-metal catalyst system for preparing phthalic, isophthalic and terephthalic acids from their corresponding alkyl benzenes wherein the heavy metal is a soluble cobalt compound and sufficient excess of air is introduced so that the waste gas still contains an excess of oxygen.

Abstract: Crude 1,10-decanedicarboxylic acid produced by the nitric acid oxidation at 20.degree.14 60.degree. C. of cyclododecanone, cyclododecanol or a mixture thereof can be purified by distillation to a purity suitable for use in the production of polyamides and polyesters by reducing prior to distillation, e.g., by heating to 70.degree.-90.degree. C., the organically bound nitrogen content and as required the nitric acid content, e.g., by washing, and water content thereof so that the sample which is distilled has maximum contents thereof of 0.05%, 0.02% and 0.1% by weight, respectively, and distilling the pre-purified sample at a sump temperature of 215.degree.-225.degree. C. and at a pressure of 0.5 - 2 torr.

Abstract: Dimethyl terephthalate is prepared by the continuous esterification of terephthalic acid in the gas phase by evaporating solid terephthalic acid in a pre-reactor by means of a hot methanol vapor stream, conducting the gas mixture through a solid bed catalyst in a follow-up reactor, and recirculating a portion of the reaction product to the pre-reactor. After the pre-reactor the terephthalic acid dispersed in the methanol gas phase is heated and vaporized in one or more consecutive heat exchangers followed by one or more dwell period lengths and immediately heated to the esterification temperature prior to entry into the follow-up reactor.

Abstract: Silica gel esterification catalysts which are mechanically stable and are highly abrasion free, particularly suitable for the esterification of dimethyl terephthalate, are prepared by impregnating silica gel in solutions of aluminum, titanium, zinc and tin compounds, separating the excess solutions and drying at elevated temperatures. The catalysts are further improved by treatment with a gaseous mixture of methanol and water.

Abstract: The process of recovering methanolic mother liquor obtained by the esterification of terephthalic acid with methanol, where the terephthalic acid may be unprepurified, is improved by adjusting to a specific gravity of about 0.85 - 0.98 by addition of water and/or methanol distillate, a mother liquor containing esterification water and dissolved solids at a concentration of about 1.0 to 6.0 percent by weight and cooling the mother liquor from a temperature of about 65.degree. - 85.degree. C to a temperature of about 10.degree. - 30.degree. C to separate the solids and remove the separated solids. The separated solids may be recycled into the esterification reaction and the unseparated solids may be recycled for oxidation to terephthalic acid following distillation to remove the methanol.

Abstract: Dimethyl terephthalate is prepared by the continuous esterification of terephthalic acid in the gas phase by evaporating solid terephthalic acid in a pre-reactor by means of a hot methanol vapor stream, conducting the gas mixture through a solid bed catalyst in a follow-up reactor, and recirculating a portion of the reaction product to the pre-reactor.

Abstract: Dimethyl terephthalate is prepared by the continuous esterification of terephthalic acid in the gas phase by evaporating solid terephthalic acid in a pre-reactor by means of a hot methanol vapor stream, conducting the gas mixture through a solid bed catalyst in a follow-up reactor, and recirculating a portion of the reaction product to the pre-reactor. After the pre-reactor the terephthalic acid dispersed in the methanol gas phase is heated and vaporized in one or more consecutive heat exchangers followed by one or more dwell period lengths and immediately heated to the esterification temperature prior to entry into the follow-up reactor.

Abstract: Dimethyl terephthalate is prepared by the continuous esterification of terephthalic acid in the gas phase by evaporating solid terephthalic acid in a pre-reactor by means of a hot methanol vapor stream, conducting the gas mixture through a solid bed catalyst in a follow-up reactor, and recirculating a portion of the reaction product to the pre-reactor.