(31f) High Performance Non-Mercury Catalysts for VCM Production: From Theoretical Study to Industrialization

Acetylene hydrochlorination is the main reaction for the dominant coal based process for VCM (vinyl chloride monomer) production from coal resource in mainland China. The traditional activated carbon based mercury catalyst for this reaction causes severe human damage and environmental pollution. Gold is widely considered as the most active metal for acetylene hydrochlorination reaction and copper is the most common metal with cost-effective advantage. The combination of two metals shows the best potential as the active component for environmentally friendly non-mercury catalysts. In our study, the performance of Au/Cu catalyst was enhanced dramatically by the introduction of organic ion ligands. Several ligands including trichloroisocyanuric acid (TCCA), cyanuric acid (CA) and melamine (M) were studied and TCCA was proved to be the best ligand for preventing Au³⁺ from reduction by acetylene, leading to longer catalyst lifetime. The findings were successfully verified by over 18000 hour’s industrial plant-trial evaluation, and the VCM productivity reached about 4.2 times comparing to industrial mercury catalyst. Abundant characterization methods including TEM, XRD, TPR, XPS, ICP-AES and nitrogen adsorption-desorption were carried out to reveal the factors which affect the activity and stability of catalysts. Meanwhile, DFT calculation results also illustrated the stability of catalyst is strongly related to the adsorption energy of reactants on the surface of catalysts. As a conclusion, TCCA can strongly interact with Au³⁺ active sites, reducing acetylene adsorption energy and inhibiting the reduction of high valence Au by acetylene, thus enhance the stability of the catalysts. Furthermore, the electrophilic atoms and conjugated molecular structure of TCCA are important for the stabilization effect. The experiment and DFT results provide reasonable methodology for the design of high performance non-mercury catalysts in acetylene hydrochlorination process, which demonstrate enormous potential for the industrialization in PVC (poly vinyl chloride) industry.