Terephthalic Acid Production via Greener Spray Process: Comparative Economic and Environmental Impact Assessments with Mid-Century Process

Abstract

Researchers at the University of Kansas, Center for Environmentally Beneficial Catalysis (CEBC) recently reported a spray process concept as a greener alternative to the conventional Mid-Century (MC) process to produce high-purity terephthalic acid (TPA) [<25 ppm 4-carboxybenzaldehyde] in a single step at 200 °C and 15 bar pressure. Plant-scale simulations of the MC process and the spray process, which considers four cases involving different amounts of acetic acid in the feed, are performed assuming a production rate of 500,000 t/yr of high-purity TPA. Comparative economic analyses and life cycle assessments (gate-to-gate and cradle-to-gate) show that the CEBC spray process significantly reduces capital and operating costs by 55% and 16%, respectively, (when using an identical amount of acetic acid in both processes) and also lowers some (such as global warming, acidification, and human health noncancer air potential) but not all adverse environmental impacts when compared to the MC process. These benefits of the CEBC spray process are mainly derived from the avoidance of a subsequent hydrogenation step required in the conventional process for purifying the crude TPA. These results provide valuable guidance for the rational design and development of a continuous spray process that has the potential to be a greener and more sustainable process for making polymer-grade dicarboxylic acids in one step.