GTC’s GT-DMT technology is a series of process enhancements for dimethyl terephthalate (DMT) production. This technology addresses oxidation, distillation, esterification, crystallization and wastewater treatment resulting in lower energy consumption, increased capacity and yield improvements.
The common method for the production of DMT from p-xylene and methanol consists of four major steps: oxidation, esterification, distillation and crystallization. A mixture of paraxylene (PX) and PT-ester is oxidized with air in the presence of a heavy metal catalyst. All useful organics are recovered from the offgas and recycled to the system. The acid mixture resulting from the oxidation is esterified with methanol to produce a mixture of esters. The crude ester mixture is distilled to remove all the heavy boilers and residue produced; the lighter esters are recycled to the oxidation section. The raw DMT is then sent to the crystallization section for removal of DMT isomers and aromatic aldehydes. This purification produces DMT that meets world-market specifications and is preferred in some polyester applications. Byproducts are recovered for sale or burned for fuel value, and usable intermediate materials are recycled.
The GTC process improvements enhance the traditional process in each of the four sections through changes in process configurations and operating conditions, alteration of separation schemes, revision of recovery arrangements, increase in the value of byproducts, and reduction in the overall recycles in the plant. The upgrade options may be implemented individually, combined, or through a series of revamps over a period of time.
Process advantages:
• Improved process yields (PX and methanol)
• Higher specific throughput
• Lower energy consumption/ton of DMT produced
• Flexible application for revamp projects
• Accumulated technical expertise available through engineering packages and follow-up services.
Oxidation Section
• Improved oxidation reduces side reactions and more effectively uses reaction volume, resulting in lower p-xylene consumption.
• New and more efficient scheme for the catalyst recovery in the plant helps reduce residue formation.
• Improved recovery of PX and removal of methyl benzoate: Product is upgraded to food or perfume grade.
• Carboxylic acid recovery: Recovery of formic and acetic acid as byproducts, upgrading value and reducing load in biotreatment unit.
Crystallization
• Typical double-crystallization scheme is simplified to increase throughputs and minimize equipment.
• New single-stage crystallization offers a low-cost alternative in revamps.
• Improved methanol recovery and handling system reduces plant losses.
• Improved isomer removal system helps reduce DMT losses.
Distillation section
• Improved distillation scheme increases purity of DMT to crystallization and reduces plant recycles.
• Improved residue treatment can increase the yields of the plant by recovering valuable materials.
Esterification
• Improved reactor design gives higher throughputs and improved methanol usage.
Licensor: GTC Technology
