Closing the Chlorine Cycle Through Oxychlorination Catalysis
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Presentation given to the UK Catalysis conference, January 8th 2016 based on the paper: Article title: XPS and STM studies of the oxidation of hydrogen chloride at Cu(100) surfaces Article reference: SUSC20763 Journal title: Surface Science Corresponding author: Prof. Philip R. Davies Online publication complete: 7-JAN-2016 DOI information: 10.1016/j.susc.2015.12.024
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Closing the Chlorine Cycle Through Oxychlorination Catalysis
- 1. UK Catalysis Conference 8th Jan. 2016 1 Surface Science & Catalysis XPS and STM studies of the reactivity of hydrogen chloride with oxygen pre-covered Cu(100) Philip R. Davies Hatem Altass, Albert F. Carley & Robert J. Davies Cardiff Catalysis Institute, School of Chemistry, Cardiff University Shaoliang Guan Cardiff & Glasgow Giovanni Rossi, David Lennon Catalysis Research, University of Glasgow
- 2. UK Catalysis Conference 8th Jan. 2016 2 Surface Science & Catalysis Environmental Catalysis Theme Exemplar Project 2. Towards closing the chlorine cycle in large-scale chemical manufacturing processes Project Leader: David Lennon (Glasgow) David J. Willock (Cardiff), Stewart F. Parker (ISIS) John M. Winfield (Glasgow) EPSRC grant EP/I038748/1. UK Catalysis Hub Consortium EPSRC grants EP/K014706/1, EP/K014668/1, EP/K014854/1, EP/K014714/1 and EP/M013219/1).
- 3. UK Catalysis Conference 8th Jan. 2016 3 Surface Science & Catalysis Production: 42 Mt per annum. Poor atom economy < 50% incorporated into product. > 30% waste : HCl & Cl‾ Chlorine in industry Closing the chlorine cycle ‘Catalytic Selective Oxidation: The Forefront in the Challenge for a More Sustainable Chemical Industry’ F. Cavani, Catal.Today, 157 (2010) 8
- 4. UK Catalysis Conference 8th Jan. 2016 4 Surface Science & Catalysis CO + ½ O2 + 2 HCl COCl2 + H2O Manufacture of isocyanates via phosgene : COCl2 CO + Cl2 COCl2 RNH2 + COCl2 RNCO + 2HCl Closing the chlorine cycle Can we close the cycle using oxychlorination? 4HCl + O2 2Cl2 + 2H2O The Deacon Process Cu/CuCl Cu/CuCl
- 5. UK Catalysis Conference 8th Jan. 2016 5 Surface Science & Catalysis Closing the Chlorine Cycle
- 6. UK Catalysis Conference 8th Jan. 2016 6 Surface Science & Catalysis Catalysis Shaoliang Guan, Giovanni Rossi, David Lennon
- 7. UK Catalysis Conference 8th Jan. 2016 7 Surface Science & Catalysis PCDD and PCDF formation Dioxin Polychlorinated dibenzo-furans •Toxic •t½ > 100 years •Formed in combustion processes by heterogeneous catalysis on fly ash (carbon nanoparticles) •Strong correlation with Cu content & Oxygen required B.R. Stanmore Combustion and Flame 136 (2004) 398–427 4HCl + O2 2Cl2 + 2H2O Cu based catalyst 450 °C Deacon process The oxidation state of copper in chlorination reactions.
- 8. UK Catalysis Conference 8th Jan. 2016 8 Surface Science & Catalysis Closing the Chlorine Cycle
- 9. UK Catalysis Conference 8th Jan. 2016 9 Surface Science & Catalysis The state of Cu during oxychlorination 1. Observing copper chloride (CuCl2) during dioxin formation using dispersive XAFS Fujimori et al. X-Ray Spectrom. 2008 37 210 XANES edge shift on heating model fly ash under a stream of 10% O2 gas. Catalysed PCDD/F formation •What happens when chlorine is present? •Does the surface composition reflect the bulk?
- 10. UK Catalysis Conference 8th Jan. 2016 10 Surface Science & Catalysis Hydrogen chloride adsorption at Cu(110) surfaces 200 nm Not an Oxychloride – XPS shows only Cl Density of the <100> structures is related to soxy 19.6 nm O(a) + 2HCl Cl(a) + H2O(g)1. HCl(g) Cl(a) + ½H2(g)
- 11. UK Catalysis Conference 8th Jan. 2016 11 Surface Science & Catalysis Cu(110)/O(a)/HCl A. F. Carley et al. Phys. Chem. Chem. Phys., 2009, 11, 10899 31-10-00#100 28.5 nm 28.5nm Cl Cu 0.36 nm 0.7 nm 0.36 nmCl Cu
- 12. UK Catalysis Conference 8th Jan. 2016 12 Surface Science & Catalysis HCl(g) and O2(g) dissociative chemisorption on Cu(100) at 290 K One monolayer = 7.7 x1014 cm-2 2 × 2 𝑅45 Cl(a)
- 13. UK Catalysis Conference 8th Jan. 2016 13 Surface Science & Catalysis HCl(g) and O2(g) dissociative chemisorption on Cu(100) at 290 K Oxygen chemisorption 290 K θO ≤ 1 One monolayer = 7.7 x1014 cm-2 2 × 2 2 𝑅452 × 2 𝑅45
- 14. UK Catalysis Conference 8th Jan. 2016 14 Surface Science & Catalysis O2(g) dissociative chemisorption on Cu(100) at 373 K and 523 K 373 K 523 K θO ~ 1.6 θO ~ 1
- 15. UK Catalysis Conference 8th Jan. 2016 15 Surface Science & Catalysis O(a) + 2HCl H2O + 2Cl(a) 2 × 2 2 𝑅45 2 × 2 𝑅45 2 × 2 𝑅45 2 × 2 2 𝑅45 2 × 2 𝑅45 Cl(a) θO ≤ 1
- 16. UK Catalysis Conference 8th Jan. 2016 16 Surface Science & Catalysis O(a) + 2HCl H2O + 2Cl(a) What are the implications of the surface coverage exceeding 1 monolayer?
- 17. UK Catalysis Conference 8th Jan. 2016 17 Surface Science & Catalysis O(a) + 2HCl H2O + 2Cl(a) HCl chemisorption at θO ~ 1.0
- 18. UK Catalysis Conference 8th Jan. 2016 18 Surface Science & Catalysis 2 × 2 2 𝑅45 O(a) 2 × 2 𝑅45 Cl(a) HCl chemisorption at θO ~ 1.0
- 19. UK Catalysis Conference 8th Jan. 2016 19 Surface Science & Catalysis 1.25×1015 atoms cm-2 7.23×1015 atoms cm-2 1.25×1015 atoms cm-2 HCl chemisorption at θO ~ 1.6
- 20. UK Catalysis Conference 8th Jan. 2016 20 Surface Science & Catalysis HCl chemisorption at θO ~ 1.6 Initial exposure to HCl
- 21. UK Catalysis Conference 8th Jan. 2016 21 Surface Science & Catalysis HCl chemisorption at θO ~ 1.6
- 22. UK Catalysis Conference 8th Jan. 2016 22 Surface Science & Catalysis Effect of O(a) on HCl adsorption kinetics Available Sites = Clmax - Cl Oxygen increases rate of Cl uptake Rate of Cl adsorption independent of θO – clean Cu not required
- 23. UK Catalysis Conference 8th Jan. 2016 23 Surface Science & Catalysis Summary • HCl adsorption is accelerated by the presence of O(a) • Cl saturation, but not adsorption kinetics are affected by the oxygen • Multilayer chlorides are easily accessible by this route • Some suggestion of epitaxial chlorides on Cu(100) but not conclusive • High chlorine concentrations gives islands at defect/boundary sites in the oxide
- 24. UK Catalysis Conference 8th Jan. 2016 24 Surface Science & Catalysis Contributors Hatem Altass, Albert F. Carley & Robert J. Davies Cardiff Catalysis Institute, School of Chemistry, Cardiff University Shaoliang Guan Cardiff & Glasgow Giovanni Rossi, David Lennon Catalysis Research, University of Glasgow
- 25. UK Catalysis Conference 8th Jan. 2016 25 Surface Science & Catalysis The structure of oxygen islands at a Cu(110) surface Cu(110) 1L O2 at 298K 30.2nm 5.11 Å Copper substrate Added Copper Added row Oxygen 3.6 Å <100> <110>
- 26. UK Catalysis Conference 8th Jan. 2016 26 Surface Science & Catalysis
Notes de l'éditeur
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