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 first PTA capacity of 150 KT was installed in India in 1988 and it has grown to 3050 KT by 2006 driven by growth in demand. The current PTA capacity is 3850 KT and is projected to grow to 7130 KT by 2014-15. The demand has shown a consistent growth of 8-10% and future growth projections are 12-13% driven by downstream investments in Polyester capacities. IOC has already made investment in the polyester feedstock chain PXPTA-
MEG at Panipat and has further plans in Gujarat. MRPL has planned PX-PTA complex as part of its downstream investment with Mangalore refinery. India plans to construct new PTA projects to help ease its tight domestic supply, which had hampered local polyester production in recent years. Commercial operations are expected to begin at the new capacities in 2013-2015, including three new plants with a total capacity of 3.3m tonnes/year. While overcapacity of polyester in 2012-2015 may absorb extra PTA supply, the tight availability of PX supply may limit PTA production during the same period.
India's polyester demand growth fell significantly to 9% in 2011 from as high as 18% in the previous year. Most polyester makers deemed the growth figure as healthy and said the surge seen in 2010 was a rebound from the 2008 recession, and therefore unsustainable. Continued strong demand for polyester, which grew from a relatively small base, is expected to sustain India's relatively high growth rates into 2015. India's polyester producers have long been sufferers of variable feedstock PTA supply. Intermittent production problems at Japan's Mitsubishi PTA plant in Haldia, West Bengal state, since its start-up in 2010, have forced India to compete with other Asia countries for imported PTA. India's reliance on PTA imports is expected to rise further in 2012-2013 because of massive polyester capacity expansions in the country. A total of 1.9m tonnes/year of new capacity is set to come on stream, thus boosting the country's polyester capacity to 7.8m tonnes/year in 2013. Reliance Industries Ltd has planned capacity expansion from 2050 KTA in 2011 to 4330 KTA in 2016.
The new PTA expansions planned are expected to take care of the demand growth and replace imports which are currently meeting the growing demand. Asia's purified terephthalic acid (PTA) capacity is expected to reach 69m tonnes/year in 2015, a 60% increase from 43m tonnes/year in 2011. The main capacity boost in the next four years will come from China and India. Asia's polyester production exceeded 41m tonnes in 2011, up by 8% from the previous year.
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.