|Sunday, July 17|
Gold Catalysts - Changing the commercial VCM production landscape
* Peter Johnston, Scientific Consultant within the Johnson Matthey Chemical Catalyst Business Unit, United Kingdom
Vinyl chloride monomer (VCM) is a major chemical intermediate for the manufacture of poly vinyl chloride (PVC), which is the third most important polymer in use today. Over 18 million tonnes of PVC are produced annually in China via acetylene hydrochlorination. Until recently, mercuric chloride supported on carbon has been the only commercial catalyst used in this process. Although it has been known for over 30 years that gold as a catalyst is active for this reaction, it is only since recent advances in the design and preparation of these catalysts that they have started to be investigated and evaluated at commercial scale. For commercial application a replacement catalyst requires a simple and environmentally benign preparation method, an ultra-low Au content and high stability which results in high productivity under reaction conditions. In this talk we describe the successful development and commercial application of carbon supported gold catalysts prepared from cationic gold complexes having S containing ligands. The JM supported gold-thiosulphate catalysts have been validated and qualified for use in full scale VCM plant trials by several Chinese VCM producers. We also discuss some of the challenges needed to be overcome for the use of these catalysts as drop-in replacements of the mercuric chloride catalyst. We describe detailed characterisation of these catalysts via a combination of several techniques including XAS and Transmission Electron Microscopy) that lead us to the conclusion that the active gold centres are single site gold Au (I) and Au (III) stabilised cations. This understanding has enabled development of further generations of gold catalysts with increased lifetimes and activity under milder conditions.