Catalyst Development of Ethylene Oxychlorination to Ethylene Dichloride and Vinyl Chloride

Abstract

Vinyl chloride monomer (VCM) is a critical component in the production of polyvinyl chloride (PVC), one of the most extensively used plastic polymers, through the polymerization process. The global VCM industry capacity was valued at 50.67 Mt in 2021. The market is projected to grow at an average annual growth rate (AAGR) of more than 1% from 2021 to 2026.

Approximately 90% of VCM currently marketed across the globe are using the “balanced VCM process”. Ethylene dichloride (EDC) was initially generated by ethylene oxychlorination and direct ethylene chlorination, then thermally cracked to produce VCM while HCl can be recycled to participate in ethylene chlorination and complete the chlorine loop. The former EDC production is typically catalyzed by CuCl2/γ-Al2O3-based catalyst due to the outstanding EDC yield (ca. 90-97%) in the typical temperature range of 220-260°C and 1-5 bar, but it still suffers a rapid deactivation due to particle agglomeration and Cu loss owing to the high vaporization of CuCl. The subsequent EDC cracking runs an endothermic reaction at high temperatures (500-550 °C) and high pressures (15-20 bar) with VCM selectivity of > 90%, yet only has a conversion rate of ~50%, which is an intensive energy consuming process. There are many undesirable products (e.g., butadiene and methyl chloride, etc.) from EDC cracking that can foul the reactor and reduce the product quality. Besides, coke formation at the high-temperature cracker tubes is another main challenge in EDC cracking for VCM production. Therefore, efforts to address this using more efficient and sustainable materials and a new route for simplifying the complex process to produce VCM are highly demanded.

The scope of this PhD thesis was to study and gain a better understanding of fundamental reaction mechanisms and the dynamic behavior of active sites in real reaction conditions by using advanced characterization technologies and kinetic studies, highlighting the rational catalyst design and new chemistry on the ethylene oxychlorination process and further VCM production.

In this work, the study of ethylene oxychlorination encompasses both fundamental aspects and the exploration of novel chemistry. We strive to enhance the efficiency and sustainability of VCM manufacturing processes, contributing to a more environmentally friendly chemistry.