Study On Mercury-free Catalyst For Hydrochlorination Of Acetylene

Vinyl chloride, an important monomer in polymer chemical industry, is mainly used in the production of polyvinyl chloride (PVC). Methods for production of vinyl chloride monomer vary based on different raw materials. Hydrochlorination based on coal resources and ethylene oxychlorination on petroleum are the two common industrial processes. Poor storage in petroleum versus rich storage in coal, present situation determined80%of domestic vinyl chloride is produced via hydrochlorination.It is well known that mercury bichloride is the key catalyst used in hydrochlorination. But the mercury are both poisonous and easily sublimate, which has already posed serious threat to the environment. Voice of prohibition in utilization of mercury is raised. Thus, the development of mercury-free catalysts become a vital issue to be concerned.Many researches have been performed in preparation of mercury-free catalysts for acetylene hydrochlorination reactions. But at present the breakthrough in the catalysts design has not been achieved to our best knowledgement.In this research, the performances of catalysts with different active components for acetylene hydrochlorination in fixed-bed reactor are studied, and the corresponding results are concluded as follows.Referring to the correlation between tandard electrode potential of metal chlorides and its catalytic activity, Cu and Pt are selected for their excellent reactivity. Via isometric impregnation, catalysts are prepared with such mono-components of different loadings, whose catalytic performance and deactivation mechanism are studied. The catalysts containing Cu have a better stability and a lower activity, while the catalysts containing Pt have a much higher activity but an easy reduction character.Using H2PtCl6and Pt(NH3)4Cl2as catalyst precursor, multi-valence Pt(Ⅳ)-Pt(Ⅱ)/C catalysts were prepared. The experimental results show that the addition of20wt.%Pt(Ⅱ) to Pt(Ⅳ)/C can increase the initial activity, but yet the aggravation over reduction deactivation occur.The catalysts prepared in different impregnation sequence vary in catalytic performance concerning acetylene hydrochlorination. A better activity is obtained over the performance of the catalyst prepared by simultaneously impregnating Pt and Cu components.Aiming at improving the catalytic performance, compositional catalysts of Pt-Cu/C catalysts were prepared and investigated. The results reveal that Pt-Cu/C catalysts, containing Pt by0.2wt.%and Cu by3.0wt.%, have a comparatively better catalytic performance to the industrialized catalyst.