Date of Award

Summer 2020

Document Type

Open Access Dissertation

Department

Chemical Engineering

First Advisor

John R. Reglabuto

Second Advisor

John R. Monnier

Abstract

Over 20 million tons of vinyl chloride monomer (VCM) is produced every year using acetylene hydrochlorination using a supported mercuric chloride catalyst. During this process mercury is reduced and sublimes into the environment harming all living animals and humans, so carbon-supported Au catalysts have been developed in attempts to replace it. Various techniques have been used to make these catalysts including several variations of dry impregnation. In this study we investigate the ability of Strong Electrostatic Adsorption (SEA) of Au(en)2Cl3 onto various supports to demonstrate the ability to rationally and consistently synthesize gold catalysts with ultra-small particle sizes. The supports include carbon, silica, titania, zirconia, ceria, and alumina.

SEA of Au(en)2Cl3 is employed with oxidized Norit Rox carbon as the support for the acetylene hydrochlorination reaction and results in greater activity and stability when compared to other carbon supports. The hydroxyl group content on Norit Rox which results from oxidation of the support facilitates high uptake of the Au(en)2Cl3 during SEA. XPS studies revealed that Norit Rox has 5 times the surface area of sp3 hybridized carbon, which are indictive of defect sites in the predominant sp2 hybridized carbon substrate, when compared to Timrex. It is hypothesized that these defects are stable binding sites for the active AuCl3 site. During HCl pretreatment gold nanoparticles on most carbon supports sinter, but because Norit Rox has an abundance of stable binding sites for the active AuCl3 species, the HCl pretreatment results in a redispersion of Au, including nanoparticles up to 4 nm in size, into atomically dispersed AuCl3. Norit Rox also can adsorb up to 3 times more Cl onto its surface during pretreatment, permitting the addition of Cl to Au during the reaction process. There is a direct correlation between the sp3 surface area and the acetylene conversion, and Cl adsorption during pretreatment and reaction. When compared to the leading catalysts made with the traditional HAuCl4 and aqua regia method, catalysts synthesized by SEA using Au(en)2Cl3 precursor are more active and stable.

Rights

© 2020, Sean Reginald Noble

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