Selective hydrochlorination of acetylene to vinyl chloride using Au-containing catalysts

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Selective hydrochlorination of acetylene to vinyl
chloride using Au-containing catalysts
J.R. Monnier1, J.R. Regalbuto1, and Donna A.
Chen2 1Department of Chemical Engineering 2Departm
ent 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
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Selective hydrochlorination of acetylene to vinyl
chloride using Au-containing catalysts
Research Team John Monnier, JR Regalbuto, and
Donna Chen Overview Direct reaction of CHCH
HCl ? CH2CHCl is superior method for production
of annual needs of 80B lbs of VCM for PVC
production. Current catalyst for direct
hydrochlorination is environmentally-unsafe
HgCl2/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.
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Industrial Relevance

• PVC (80B lbs/yr) is 3rd largest volume polymer
  after PE and PP.
• 2. CH2CHCl is highest volume monomer prepared
  by catalysis.
• Majority of VCM produced by oxychlorination of
  CH2CH2.
• CH2CH2 2 HCl ½O2 ? ClCH2CH2Cl H2O ?
  (CuCl2/C cat)
• ClCH2CH2Cl ? ? CHClCH2 HCl (500oC,
  15-30 bar)
• China is largest producer of VCM and 70 produced
  from HCCH.
• 5. HgCl2/C catalyst is reduced to Hgo 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.

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Current status of Au/C
Monnier, Appl. Cat. A General, 475 (2014) 292.

• 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 timesAu
  sintering or restructuring?
• What is the active surface? Not yet identified.

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Direct formation of VCl from HCCH HCl
Hutchings group have determined following
correlation
Hg2 2e- ? Hgo E0 0.80 V Pd2 2e- ? Pdo
E0 1.00 V Au3 3e- ? Auo E0 1.52 V

• Activity related to reduction potential.
• Active catalyst assumed to be oxidized state,
  e.g., AuCl3/C.
• Above assumptions are inconsistenteasily reduced
  catalysts should not re-oxidize.
• Does reactive Cl come from Au-Cl or from adsorbed
  HCl and HCl reoxidizes Auo ?

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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 Aun surface sites (modified
  Wacker process).
• Model Au surfaces will be partially chlorided
  using ClCH2CH2Cl and studied by XPS, ISS, and AFM
  to probe Au surface. Possibilities include Auo,
  AuCly, AuxCly. Pulsed flow of CHCH to measure
  reactivity.
• All supported catalysts to be evaluated in
  dedicated micro-reactor.

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Outcomes/ Deliverables

• Year 1
• Current reactor/GC modified for unattended
  operation gt 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.

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Impact

• 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.

• 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.