Disclosed is a process for producing terephthalic acid. The process includes contacting p-xylene with a gaseous stream containing oxygen (O.sub.2) in presence of a homogeneous catalyst solution, at a reaction temperature of 180° C. to 195° C. to oxidize at least a portion of the p-xylene and form a product stream containing terephthalic acid, said homogeneous catalyst solution contains 350 ppm to 450 ppm cobalt (Co), 170 ppm to 270 ppm manganese (Mn), and 410 ppm to 510 ppm bromine (Br), wherein a Br/(Co+Mn) wt. % ratio is 0.5:1 to 1:1, and a Co to Mn wt. % ratio is 1.5:1 to 2:1.

Disclosed is a process for producing terephthalic acid. The process includes contacting p-xylene with a gaseous stream containing oxygen (O.sub.2) in presence of a homogeneous catalyst solution, at a reaction temperature of 180° C. to 195° C. to oxidize at least a portion of the p-xylene and form a product stream containing terephthalic acid, said homogeneous catalyst solution contains 350 ppm to 450 ppm cobalt (Co), 170 ppm to 270 ppm manganese (Mn), and 410 ppm to 510 ppm bromine (Br), wherein a Br/(Co+Mn) wt. % ratio is 0.5:1 to 1:1, and a Co to Mn wt. % ratio is 1.5:1 to 2:1.

The present invention provides an effective and selective process for the depolymerization of polyethylene terephthalate (PET), polyethylene furanoate (PEF), polylactic acid, polycarbonates, polyethers and polyamides into pure and high yielding valorized products by combining the glycolysis-hydrolysis reactions using a homogeneous acidic ionic liquid (AIL) catalyst, resulting in excellent polymer conversion.

The present invention provides an effective and selective process for the depolymerization of polyethylene terephthalate (PET), polyethylene furanoate (PEF), polylactic acid, polycarbonates, polyethers and polyamides into pure and high yielding valorized products by combining the glycolysis-hydrolysis reactions using a homogeneous acidic ionic liquid (AIL) catalyst, resulting in excellent polymer conversion.

A method of obtaining a purified regenerated diacid from a depolymerization of a polyester in a waste material wherein the depolymerization provides a depolymerized mixture comprising a regenerated diol, a regenerated diacid, and a catalyst is disclosed. The method comprises: separating a regenerated composition including the regenerated acid and the catalyst from the regenerated diol; providing the regenerated composition in a liquid medium to form a pre-aged mixture; subjecting the pre-aged mixture to thermal cycling wherein the cycling occurs within 25° C. and within a temperature range of from 150° C. or more to 300° C. or less to form an aged mixture; and separating the regenerated composition from the liquid medium in the aged mixture.

A method of obtaining a purified regenerated diacid from a depolymerization of a polyester in a waste material wherein the depolymerization provides a depolymerized mixture comprising a regenerated diol, a regenerated diacid, and a catalyst is disclosed. The method comprises: separating a regenerated composition including the regenerated acid and the catalyst from the regenerated diol; providing the regenerated composition in a liquid medium to form a pre-aged mixture; subjecting the pre-aged mixture to thermal cycling wherein the cycling occurs within 25° C. and within a temperature range of from 150° C. or more to 300° C. or less to form an aged mixture; and separating the regenerated composition from the liquid medium in the aged mixture.

A built-in micro interfacial enhanced reaction system and process for PTA production with PX are provided. The system includes a reactor and a micro interfacial unit disposed inside reactor. The reactor includes a shell, an inner cylinder concentrically disposed inside shell, and a circulating heat exchange device partially disposed outside shell, inner cylinder having a bottom end connected to inner bottom surface of the shell in closed manner and an open top end, a region between shell and inner cylinder being first reaction zone, inner cylinder containing second reaction zone and third reaction zone from top to bottom, circulating heat exchange device being connected to inner cylinder and micro interfacial unit respectively. The invention can solve problems of large waste of reaction solvent acetic acid under high temperature and high pressure and being unable to take out the product TA in time during existing process of PTA production with PX.

A built-in micro interfacial enhanced reaction system and process for PTA production with PX are provided. The system includes a reactor and a micro interfacial unit disposed inside reactor. The reactor includes a shell, an inner cylinder concentrically disposed inside shell, and a circulating heat exchange device partially disposed outside shell, inner cylinder having a bottom end connected to inner bottom surface of the shell in closed manner and an open top end, a region between shell and inner cylinder being first reaction zone, inner cylinder containing second reaction zone and third reaction zone from top to bottom, circulating heat exchange device being connected to inner cylinder and micro interfacial unit respectively. The invention can solve problems of large waste of reaction solvent acetic acid under high temperature and high pressure and being unable to take out the product TA in time during existing process of PTA production with PX.

Systems and methods for recycling polymers are provided. One embodiment provides a method for recycling synthetic polymers by combining the polymers with a solid depolymerizing catalyst in a vessel, mechanically shearing the combined polymers and the solid depolymerizing catalyst against each other to produce monomers from the polymers; and collecting the monomers. In some embodiments the solid depolymerizing catalyst is solid sodium hydroxide. In some embodiments collecting the monomers is achieved by contacting the sheared polymer and catalyst with a recyclable volatile solvent to dissolve the monomers. In some embodiments, the method includes purifying the collected monomers for repolymerization. In some embodiments purifying the monomers is achieved using nanofiltration membrane technology, cyclic fixed bed adsorption, simulated moving-bed adsorption or a combination thereof.

Systems and methods for recycling polymers are provided. One embodiment provides a method for recycling synthetic polymers by combining the polymers with a solid depolymerizing catalyst in a vessel, mechanically shearing the combined polymers and the solid depolymerizing catalyst against each other to produce monomers from the polymers; and collecting the monomers. In some embodiments the solid depolymerizing catalyst is solid sodium hydroxide. In some embodiments collecting the monomers is achieved by contacting the sheared polymer and catalyst with a recyclable volatile solvent to dissolve the monomers. In some embodiments, the method includes purifying the collected monomers for repolymerization. In some embodiments purifying the monomers is achieved using nanofiltration membrane technology, cyclic fixed bed adsorption, simulated moving-bed adsorption or a combination thereof.