Au nanoparticles have a high potential in catalysis and have been studied extensively for years beginning with Haruta’s discovery in 1987 that gold nanoparticles are highly active in CO oxidation reactions at sub-ambient conditions. Since then Au has been found to be active for many reactions like the water gas shift reaction, oxidation of 5-hydroxymethylfurfural, and acetylene hydrochlorination. In my work we demonstrate a simple, scalable synthesis of ultra-small (<2nm) Au nanoparticles on a variety of supports using Strong Electrostatic Adsorption (SEA). SEA is used to create highly dispersed nanoparticles that are strongly bound to a support by controlling the pH of the solution. By controlling the pH of the solution relative to the support point of zero charge, the surface of the support becomes protonated or deprotonated resulting in an electrostatic interaction with an oppositely charged ionic precursor complex. Using the precursor salt Au(en)2Cl3 we have demonstrated the ability to synthesize ultra small Au nanoparticles on various supports using SEA. After showing that SEA is an excellent method for the synthesis of Au catalysts, Au/C catalysts were studied for acetylene hydrochlorination for the generation of vinyl chloride monomer.
Vinyl chloride monomer (VCM) is the largest produced commodity chemical worldwide with a production of 40 million tons a year. VCM is the monomer used to make polyvinyl chloride (PVC) which is one of the top three plastic polymers produced per year by volume. 13 of the 40 million tons of VCM produced is produced through acetylene hydrochlorination, a process yields a highly pure stream of VCM and requires little further treatment or thermal cracking. This process traditionally uses a mercuric chloride catalyst, which comes with environmental and health concerns. My work involves developing an alternative Au/C catalyst for the acetylene hydrochlorination process and investigating the role of the oxidation state of the hydroxyl groups on the surface of the carbon support on the size, activity, and stability of the catalyst. From this study there is evidence that SEA coupled with the Au(en)2Cl3 cationic precursor is able to deposit monometallic Au onto some carbon supports, which is known to be the primary active site for the acetylene hydrochlorination reaction. This ability to ability to synthesize atomic Au particles onto a carbon support whose surface that I have modified has allowed me to understand the affect of the support surface on synthesis and activity.