PTA - Purified Terephthalic Acid
Purified terephthalic acid (PTA) is primarily used in polyester production with polyester fibre consuming a large proportion of global output.
However, polyethylene terephthalate (PET) resin production for packaging and film applications is growing very rapidly due to its success in penetrating the soft drinks and water bottles market.
A smaller proportion of PTA is utilized in the production of polyester film which had, until recently, been the material of choice for the audio recording industry.
The remaining PTA is used in making cyclohexanedimethanol, terephthaloyl chloride, copolyester-ether elastomers, plasticisers and liquid crystal polymers.
Del Meyer produced the first PTA. He joined Amoco in 1953; the company was testing a new technology developed by a firm called Scientific Design that would convert paraxylene – a raw material Amoco could produce in great quantities from its extensive refining operations – to terephthalic acid (TA), the feedstock for polyester.
Believing there eventually would be a huge market for synthetic fibers, Amoco acquired worldwide rights to the process in 1957, the year Amoco Chemical Company officially came into existence. Two months after Meyer’s first successful experiment, Phil Towle decided to go with this newly discovered technology and put together a team to design Amoco’s commercial process.
With no pilot plant, no process studies and only a few experiments, the new plant proposal was presented to the Standard Oil board.
Worldwide around 65% of PTA goes into polyester fibre, 27% to PET bottle resin and the remaining 8% to film and other plastic end uses.
BP, Amoco Chemicals, Alfa Mexico, Reliance Industries Ltd, Mitsubishi Chemical Corporation (MCC), Sinopec, Zhuhai Biyang Chemical Co., Ltd, Luoyang Petrochemical Co., Ltd Tianjin Petrochemical Co., Ltd. Xiamen Xianglu Petrochemical Co., Ltd, Jinan Qilu Group Synthetic Fiber Co., Ltd are some of the leading producers of PTA. Technology licensors for PTA are Dupont, Mitsui, Dow/Inca, Mitsubhishi, Tuntex, Interquisa, Eastman, Lonza and Hüls/Witten.
The Global nameplate capacity of PTA is projected to be nearly 73 MMT in 2016.
The first PTA capacity of 150 KTA was installed in India in 1988 and it is projected to reach around 6400 KTA in 2016-17. The demand has shown a consistent growth of 8-10% and is expected to be around 5400 KTA in 2016-17.
PTA applications can be found in plastic containers for beverages, food and electronics, apparel, home textiles, carpets and industrial fibre products, and audio and video recording tapes, photographic films and labels.
The core technology for producing TPA has remained the same since the 1960s—crude TPA is produced by bromine-promoted catalytic oxidation of p-xylene, and purified by a hydrogenation step. However, several incremental improvements have been implemented in the TPA process over the years, covering both the main oxidation and the purification sections.
In late 2000, BP announced the development of a new-generation TPA process, called “X Technology”. The new technology achieves great process simplification by using innovative methods for water recycling and improved solid-liquid separation techniques. As a result, purified terephthalic acid (PTA) can be produced at significantly lower capital and operating costs. Another technology that has attracted renewed interest is the production of medium-quality terephthalic acid (MTA). The MTA process uses a post-oxidation system that allows for elimination of the entire purification section of the PTA process. Eastman-Lurgi and Mitsubishi Chemical are the main licensors of this technology.