Study on the deactivation mechanism of mercury chloride catalyst employed for polyvinyl chloride production

Mercury chloride catalyst is widely employed for the polyvinyl chloride (PVC) production in China, whereas the catalyst deactivation mechanism which is crucial for the design, regeneration, and disposal of deactivated catalyst is still unclear. Herein, the physical and chemical characteristics of fresh and deactivated catalysts were systematically investigated. The results show that chlorinated organic compounds, including 2-chloromethyl-1,3-dichloro-2-methylpropane (C 5 H 9 Cl 3 ), 1,3,3-trichloro-2-methyl-4-pentanone (C 6 H 9 Cl 3 O), and 1,3-dichloro-2-butene (C 4 H 6 Cl 2 ), were identified as the dominant constituents of deposited carbon, which caused pore blockage and active site coverage. The content and species of mercury on the catalyst were changed after deactivation. The mercury content on the deactivated catalyst was decreased from 3.73%(mass) to 1.47%(mass). Nonlabile organic and elemental mercury instead of crystalline oxide-bound mercury dominate the mercury species on deactivated catalyst. The thermal stability of mercury species on the deactivated catalyst was reduced, in which the desorption peak temperature was decreased from 310 °C to 285 °C. The content of other active components, including potassium, zinc, and copper chlorides, also declined. These findings offer critical insights for the design of mercury chloride catalyst and the development of deactivated catalyst regeneration or disposal technologies.