PRODUCTION OF CRUDE TEREPHTHALIC ACID (CTA) FROM PARAXYLENE OXIDATION

Abstract

Terephthalic acid is a central component in polyester fibres , films, PET bottles, and other polyester products. It is a raw material for a variety of household products and clothing, and since much of the plastic and polyester needs of Pakistan are met through exports, there is an internal need to produce terephthalic acid. Most of the terephthalic acid now is commercially produced from the oxidation process of paraxylene. The project will aim to design a process that produces crude terephthalic acid from paraxylene by an air oxidation reaction, focusing on obtaining a crude product that can be further purified. Crude Terephthalic Acid (CTA) produced is about 99.7% pure containing 4-Carboxybenzaldehyde impurities which weaken the strength of plastics and fibers and hence must be removed. For mass production, the AMOCO process is used, which uses a homogenous liquid phase catalyst at set conditions and results in the highest yield. Our project is centered around producing 100 tons of CTA per day and maximizing the potential of the plant by optimal design. Moreover, we have focused on reducing the plant load, increasing efficiency, and making our process more environmentally friendly and safer. Under assumed economic conditions, this plant is expected to produce an annual profit of $ 16.3 million and result in a payback period of 3 years and 6 months. In our thesis, we will summarize the process design and simulation of a crude terephthalic acid production plant and describe how our final year project has been carried out. This will include all relevant stages such as determining the process and methodology, carrying out an efficient material and energy balance on every equipment, to designing those equipment and then carrying out an economic analysis to determine the total costs of the plant. Moreover, a hazard & operability study was carried out over the plant to account for all possible risks. Lastly, the plant was also simulated in Aspen Plus and relevant instrumentation for control loops on a reactor was identified.