Selective hydrochlorination of acetylene to vinyl chloride using Au-containing catalysts J.R. Monnier 1, J.R. Regalbuto 1, and Donna A. Chen 2 1 Department of Chemical Engineering 2 Department of Chemistry and Biochemistry University of South Carolina Center for Rational Catalyst Synthesis Planning Grant Workshop University of South Carolina, Columbia, SC June 16, 2014

Selective hydrochlorination of acetylene to vinyl chloride using Au-containing catalysts Research Team: John Monnier, JR Regalbuto, and Donna Chen Overview: Direct reaction of CH≡CH + HCl  CH 2 =CHCl is superior method for production of annual needs of 80B lbs of VCM for PVC production. Current catalyst for direct hydrochlorination is environmentally-unsafe HgCl 2 /C. Alternative Au/C catalyst sinters very rapidly and active Au surface is not known. Technical information: Develop bimetallic catalysts that are resistant to sintering and have higher activities. Use surface science and model Au surfaces to determine nature of Au-Cl site active for hydrochlorination.

Industrial Relevance 1.PVC (80B lbs/yr) is 3 rd largest volume polymer after PE and PP. 2. CH 2 =CHCl is highest volume monomer prepared by catalysis. 3.Majority of VCM produced by oxychlorination of CH 2 =CH 2. CH 2 =CH HCl + ½O 2 → ClCH 2 CH 2 Cl + H 2 O + Δ (CuCl 2 /C cat) ClCH 2 CH 2 Cl + Δ → CHCl=CH 2 + HCl (500 o C, bar) 4.China is largest producer of VCM and 70% produced from HC≡CH. 5. HgCl 2 /C catalyst is reduced to Hg o and volatilizes--320 tons of Hg lost/yr.  Improved Au-based catalyst would have large impact on VCM production. Fewer than 5 research groups world-wide are active in this area.

Current status of Au/C  Activities are similar after 3 hrs of reaction regardless of pretreatment.  Sintering of Au from 2  20 nm after 1 hr on-line, primarily due to HCl.  Slow deactivation at longer reaction times—Au sintering or restructuring?  What is the active surface? Not yet identified. Monnier, Appl. Cat. A: General, 475 (2014) 292.

Direct formation of VCl from HC≡CH + HCl Hutchings group have determined following correlation: Pt Au Hg e -  Hg o E 0 = 0.80 V Pd e -  Pd o E 0 = 1.00 V Au 3+ +3e -  Au o E 0 = 1.52 V  Activity related to reduction potential.  Active catalyst assumed to be oxidized state, e.g., AuCl 3 /C.  Above assumptions are inconsistent—easily reduced catalysts should not re-oxidize.  Does reactive Cl come from Au-Cl or from adsorbed HCl and HCl reoxidizes Au o ?

Proposed hypotheses  SEA will be used to prepare small, well-distributed Group IB or Group VIII metal particles (cores) on carbon support. ED then used to deposit stable shell of Au on core. Core metal with higher surface free energy than Au should stabilize Au from sintering.  Controlled and lower amounts of Au on core metal such as Cu will give bimetallic Cu-Au surfaces. Bifunctional effect may assist Cl transfer from Cu to Au to maintain Au n+ surface sites (modified Wacker process).  Model Au surfaces will be partially chlorided using ClCH 2 CH 2 Cl and studied by XPS, ISS, and AFM to probe Au surface. Possibilities include Au o, AuCl y, Au x Cl y. Pulsed flow of CH≡CH to measure reactivity.  All supported catalysts to be evaluated in dedicated micro-reactor.

Outcomes/ Deliverables Year 1  Current reactor/GC modified for unattended operation > 100 hrs.  Synthesis and evaluation of multiple series of metal core – Au shells.  Catalysts with bimetallic, Au-containing surfaces prepared and evaluated.  Surface analysis method for Cl deposition on Au model surfaces demonstrated. Year 2  Identify nature of active site for reaction.  Use results from model studies to refine catalyst compositions.  Assess feasibility for private, contract research with industrial partner.

Impact Duration of Project and Proposed Budget Year 1: $60K for equipment and one FT graduate student. Year 2: $60K for one FT graduate student and materials/supplies. Year 3: Assess future of project.  Successful synthesis of active and stable Au catalyst could change economics of VCM synthesis. Potentially lower cost feed (coal) and much simpler process. Knowledge learned about stabilizing Au surfaces would have direct impact for other Au-catalyzed reactions. Education of students highly skilled in catalyst preparation and evaluation and appreciation of industrial research.