Study On Mercury-free Catalyst For Vinyl Chloride Synthesis By Acetylene Method

Vinyl chloride?VCM?is a polyvinyl chloride?PVC?monomer that is one of the five general-purpose plastics.Vinyl chloride synthesis mainly uses acetylene hydrochlorination and ethylene oxychlorination.Due to the special energy structure of coal-and oil-rich coal,the process route for the synthesis of vinyl chloride from acetylene is dominant in China.Mercuric chloride,the active component of the mercury catalyst used in the acetylene process,is easily lost to the human body and is harmful to the human body.Domestic mercury resources are increasingly Depletion and mercury pollution on the environment are imperative for the development of environmentally friendly mercury-free catalysts that can replace mercury catalysts.Although mercury-free catalysts have been studied for many years,they have not been developed to replace mercury catalysts because of their low cost,high activity,good stability,and long lifetime.The previous research group found that the addition of tin as a promoter showed excellent catalytic performance when the copper-based mercury-free catalysts were researched.This topic further explored the use of non-precious metal mercury-free catalysts with tin as the main active component in acetylene hydrochlorination.Catalytic performance.In this paper,activated carbon is used as the carrier,high valence tin is the main active component,high valence copper is the secondary active component,various additives are added,non-precious metal mercury-free catalysts are prepared by different loading processes,and the types,washing and reform of activated carbon are studied.The effects of different impregnation methods on the catalytic performance of mercury-free catalysts;the activity of mercury-free catalyst formulations with high valence tin-copper composites was investigated;additives such as KCl,BiCl₃,and alkaline-earth metal elements were added,and the addition of rare earth element cerium can improve the stability of the catalyst and reduce the loss.The influence of the catalytic performance of the catalyst;the material ratio of the active component and the reaction process conditions were optimized,and preliminary discussion was made on the anti-interference performance of the mercury-free catalyst.The main conclusions are as follows:?1?The catalytic performance of the mercury-free catalyst prepared after pretreatment of the carrier is significantly improved.The effect of coal-based activated carbon treatment is obvious,and the effect of coal-based activated carbon after water washing is close to that of coconut shell activated carbon.The effect of the catalyst prepared from washed coal activated carbon and acidic coal activated carbon is similar.The mercury-free catalyst active component prepared by water-washed coal activated carbon as the carrier by the equal volume impregnation method has good loading effect and no waste liquid.The preparation method of the catalyst is simple and highly efficient and environmentally friendly.?2?The multi-component composite catalyst has better catalytic performance than single and two-component catalysts,and has good catalytic performance and long service life.The increase in the conversion of BaCl2,SrCl2,CaCl2,and MgCl2,the alkaline earth element chlorides,increased monotonically,The cerium chloride and tin-copper elements have obvious synergistic effects.The addition of rare earth element cerium chloride can improve the stability of the catalyst and reduce the loss.After the introduction,the interaction between the components can be significantly changed to achieve the same catalytic performance.SnCl4-CuCl2-BiCl3-The amount of CuCl2 added in the CeCl3/C catalyst can be halved.?3?The optimized SnCl₄-CuCl₂-BiCl₃-CeCl₃/C multi-component composite mercury-free catalyst was obtained.The optimal composition was 22%SnCl4/6%CuCl₂/10%BiCl₃/2%CeCl₃,and the most suitable process conditions were determined.For the activation of 1h,reaction temperature 120°C,space velocity 90h^-1,and material ratio V?HCl?/V?C2H2?=1.1,under the conditions,the initial activity of the mercury-free catalyst can approach the mercury catalyst level,and the stability is good.The acetylene conversion was 95.1%and the vinyl chloride selectivity was 99.5%.