Critical Review of Catalysis for Ethylene Oxychlorination

Abstract

Ethylene oxychlorination is the key technology in vinyl chloride (VCM, the monomer of PVC, polyvinyl chloride) production to close the chlorine loop by consuming the HCl released from the former cracking step. Due to the high demand for PVC, this leads to ethylene oxychlorination being one of the most important processes in the industry. This Review covers an indepth analysis of the dynamic nature of active sites for the main and side reactions involved in ethylene oxychlorination, featuring the findings and viewpoints from the dynamic kinetics study and analysis under industrial operating conditions. A unified picture of the mechanism of the surface reactions, and the effect of supports and promoters, has been presented based on the decoupled redoxcycle experiments, which leads to a significantly better understanding of the mechanism and provides valuable guidelines for effective catalyst design. Operando techniques and kinetic tools of the rate-diagram, as well as their application to the study of the redox-cycle in ethylene oxychlorination and kinetic models on both the main product and byproduct, are also reviewed. Perspectives on challenges and new process development and future research focus for better study of the VCM production chemistry are also proposed.

Prediction and Tuning of the Defects in the Redox Catalysts: Ethylene Oxychlorination

“…The Cl that can be removed by reduction is defined as removable Cl. The difference between the theoretical and measured maximum removable Cl is caused by strong covalent bonding with alumina [12] . The estimated reaction rates are shown in Figure 1a as a function of removable Cl.…”

“…The difference between the theoretical and measured maximum removable Cl is caused by strong covalent bonding with alumina. [12] The estimated reaction rates are shown in Figure 1a as a function of removable Cl. It reveals a non-linear relationship between the reduction rate and the removable Cl in the catalysts, clearly defining two regions.…”

Ethane‐Based Catalytic Process for Vinyl Chloride Manufacture

“…4%,f inding applications in construction, pharmaceutical, and automotive industries,a mong others. [1] PVC manufacture started in the 1930s from coal-derived acetylene by reacting this substrate with hydrogen chloride (HCl) over am ercury-based catalyst to yield monomer vinyl chloride (C 2 H 3 Cl) (Figure 1a). [1a, 2] Following the petroleum boom of the 1950s,t he acetylenebased pathway was gradually replaced by atwo-step route for the generation of C 2 H 3 Cl from oil-derived ethylene.T his socalled balanced process integrates catalytic ethylene chlorination and oxychlorination to ethylene dichloride (1,2-C 2 H 4 Cl 2 ), followed by its thermal cracking into C 2 H 3 Cl and HCl, which is recycled in the copper-catalyzed oxychlorination step to produce 1,2-C 2 H 4 Cl 2 (Figure 1b).…”

Nitrogen‐Doped Carbon‐Assisted One‐pot Tandem Reaction for Vinyl Chloride Production via Ethylene Oxychlorination

“…Polyvinyl chloride (PVC) is the most versatile of all thermoplastics that can be used in aw ide range of applications.I ti st he third-highest volume polymer,s lightly behind polyethylene and polypropylene. [1] Vinyl chloride (VCM), the monomer of PVC is the key building block for PVC production, which is mainly produced from ethylene dichloride (EDC) through thermal cracking.C urrently,a pproximately 90 %o fV CM production plants worldwide are using ab alanced VCM process where Cl 2 by first chlorinating ethylene to produce EDC,t he EDC is then thermally converted to VCM by dehydrochlorination. [1a] TheH Cl produced in the dehydrochlorination reactor is typically captured and recycled to an oxychlorination reactor to convert C 2 H 4 ,O 2 ,and HCl to EDC,which is again converted to VCM by dehydrochlorination.…”