1. Heterogeneous Catalysis for Green Chemistry Dr. M. Sankar Cardiff Catalysis Institute School of Chemistry Cardiff University Cardiff, UK. 02/01/2010 Cardiff Catalysis Institute

2. Overview of this Presentation  Organic Carbonates using CO 2  Synthesis of Cyclic Carbonates  Synthesis of Dimethyl Carbonates  Selective oxidation using Gold nanocrystals based Catalysts  Oxidation of Benzyl Alcohol using Au-Pd Supported on TiO 2  Oxidation of Glycerol using supported monometallic Catalysts.

3. Mt. Kilimanjaro (Africa ). Ice cap is shrinking Columbia glacier Alaska Glacier National Park 1914-1997 2008 Global Warming – Visible Effects

4. CO 2 Emission & Possible Solution Sequestration Utilization M. A. Scibioh, B. Viswanathan Proc.Indn.Natl.Acad.Sci., 70A (3), 2004.

5. Various Chemical Transformations using CO 2  Monomers  Aprotic Organic Solvents  Fine Chemical Intermediates Cyclic Carbonate  Methylating Agent  Carbonylating Agent  Oxygenated fuel additive  Substitute for MTBE Dimethyl Carbonate

6. Specific Reactions of Interest Cyclic Carbonate Dimethyl Carbonate

7. Synthesis of Cyclic Carbonates

8. + Catalytic System-I Na 12 [WZn 3 (H 2 O) 2 (ZnW 9 O 34 ) 2 ]46H 2 O (Zn-W-Sandwich Polyoxometalate) Dimethylaminopyridine

11. Experimental conditions: 0.4 MPa CO 2, 10 ml CH 2 Cl 2, 0.0026 mmol of Zn-POM, DMAP = 3 mole equivalent Zn POM Typical Reaction Data Substrate Product Temp (deg C) Time (Hrs) Conv (%) Selectivity (%) 140398 16099697 160129997

12. Experimental conditions: 0.4 MPa CO 2, 0.0026 mmol of Zn-POM, DMAP = 3 mole equivalent Zn POM Data Continued……. SubstrateTemp (deg C) Time (Hrs) Conv (%) Selectivity(%) 140398 (without solvent) 14039998 (Recovered POM) 14039998

13. Experimental conditions: 0.4 MPa CO 2, 10 ml CH 2 Cl 2, 0.0026 mmol of Zn-POM, DMAP = 3 mole equivalent Zn POM Data Continued….. SubstrateSub: Cat ratio Temp (deg C) Time (Hrs) Conv (%) Selectivity (%) 10,00014039798 25,000140398 50,00014038498

14. Structural Integrity of Zinc - Polyoxometalate

15. Proposed mechanism

16.  Very high Substrate Vs Catalyst Ratio  Reaction without organic solvent – atom economy  Applicable to a range of epoxides  Polyoxometalate part is Recoverable and reusable  First ever Polyoxometalate based catalyst system for this particular reaction Highlights M. Sankar, N. Tarte, P. Manikandan, Appl. Catal. A. 276 (2004) p.217. US Patent - 6,924,379 Indian Patent - Granted

17. Catalytic System-II Si Si-O Si-O Si-O N N Si Si-OH Si-O Si-O N N OH I II and/or Si EtO EtO EtO NH N Si-OH Si-OH Si-OH + Silica Cl + Chloropropyl triethoxy silane Imidazole L. T. Aany Sofia, Asha Krishnan, M. Sankar, N. K. Kala Raj, P. Manikandan, P. R. Rajamohanan, and T. G. Ajithkumar* J. Phys. Chem. C 113 (2009), 21114.

18. Si-NMR of Fumed SilicaSi-NMR of Functionalised Silica Solid State NMR Characterization

19. 13 C NMR of Functionalised Silica

20. Reaction Data Temperature EffectRecycle Studies

21. Catalyst Epoxide Temp/TimeEpox ConvCC Selec Si-ImidECH120 °C/4 h98 No CatalystECH120 °C/4 h<50 Si-ImidPO130 °C/10 h99 Si-ImidBO130 °C/10 h9994 Si-ImidSO130 °C/10 h7997 ECHPO BO SO Catalyst Activity

22. Structural Stability – MAS-NMR 13 C 29 Si Fresh Recovered Fresh Recovered

23. Proposed - Mechanism M.Sankar et.al., (Manuscript under preparation)

24. Highlights  Single Site – Heterogeneous Catalyst  Recoverable and Reusable  Easy to synthesize  Relatively mild reaction condition

25.  CO 2 : 6-10 bar, Temp: 90-130 ºC, Time: 4-10 h  Yield : > 96 %, Solvent:No Recoverable & Reusable: Yes R = H, Cl, CH 3 Cyclic Carbonate Summary

26. Synthesis of Dimethyl carbonate

27. Exp. Cond. EC/PC : 50mmol, Methanol : 500mmol Catalyst: 1gm p-Xylene : 1gm Time: 5hrs Sl. No. Subs Catalyst Temp o C DMC Yield(%) 1ECNa 2 WO 4.2H 2 O2579 2ECNa 2 WO 4.2H 2 O (I-Recov) 2578 3PCNa 2 WO 4.2H 2 O2523 4ECCaWO 4 2579 5ECLi 2 WO 4 2566 6ECK 2 WO 4 2571 7ECNa 2 VO 3 2579 Catalytic System-I

28. Catalysis Data Effect of TemperatureHeterogeneous Catalyst

29. Powder XRD IR Structural Integrity of Sodium Tungstate

30. Adsorbed CH 3 O - CH 3 OH Adsorbed CH 3 O - Active Intermediate: IR and Raman Studies

31. Proposed Mechanism DMC formation M. Sankar, N. Madhavan Nair, K.V.G.K. Murty, P. Manikandan, Appl. Catal. A. 312 (2006) p.108. US Patent – Applied Indian Patent - Applied

32. Highlights  Active at room temperature  No CO 2 pressure – pot reaction  Recoverable & Reusable  No complicated synthesis

33. Selective Oxidation using “Green” Oxidants Introduction: Au and Au-Pd nanoparticles based catalysts have been reported to be very effective for :  Epoxidation of Alkenes: Hutchings et.al., Nature (2005).  Direct synthesis of Hydrogen Peroxide: Hutchings et.al., Science (2009).  Oxidation of Primary Alcohols: Hutchings et.al., Science (2006), In this Presentation:  Oxidation of Benzyl Alcohol : Mechanistic Investigation  Oxidation of Bio-renewable Feedstocks : Glycerol Oxidation

34. Benzyl alcohol conversion and selectivity in benzaldehyde with the reaction time at 100 o C, 0.2 MPa O 2 pressure: () Au/TiO 2, (  )Pd/TiO 2, (  ) Au-Pd/TiO 2 ; solid symbols – conversion, open symbols – selectivity Science 2006 AuPd nanoparticles prepared by impregnation 1-50 nm Au-rich core, Pd-rich surface Oxidation of Benzyl Alcohol using Au-Pd supported on TiO 2 Aim is to understand the origin of Toluene in the “Solventless” oxidation of Benzyl alcohol and thereby “switching off” the toluene production

35. Experimental  50 ml Glass Reactor  Stirred at 1000 rpm – No mass transport limitations  Analysed by GC using mesitylene as external standard  Rates of the reaction were calculated for the first 10% conversion level Catalyst Synthesis: (Au-Pd)/TiO 2, Au/TiO 2, Pd/TiO 2 by Sol-immobilization technique 1 Catalytic Reaction (3 phase system: solid/liquid/gas) 1 J.A. Lopez-Sanchez, N. Dimitratos, P. Miedziak, E. Ntainjua, J.K. Edwards, D. Morgan, A.F. Carley, R. Tiruvalam, C.J. Kiely and G.J. Hutchings, Phys.Chem. Chem. Phys, 2008, 10, 1921.

36. Initial rates of reaction under oxygen at 80 o C CatalystBenzyl AlcoholBenzaldehydeToluene d[BzOH]/dt ( 10 -7 mol s -1 ) R2R2 d[Ald]/dt ( 10 -7 mol s -1 ) R2R2 d[Tol]/dt ( 10 -7 mol s -1 ) R2R2 1%(Au-Pd)/TiO 2 -5.420 ± 0.460.9864.810 ± 0.460.9820.755 ± 0.1510.950 0.5%Au/TiO 2 -0.032 ± 0.00470.9890.0316 ± 0.00440.9900.000237 ± 0.00010.921 0.5%Pd/TiO 2 -0.376 ± 0.090.9470.359 ± 0.08570.9480.00158 ± 0.00640.869 Catalyst: 0.02g Benzyl Alcohol: 1g O 2 : 1 bar Stirring: 1000rpm Initial rates of reaction under He at 80 o C CatalystBenzyl AlcoholBenzaldehydeToluene d[BzOH]/dt ( 10 -7 mol s -1 ) R2R2 d[Ald]/dt ( 10 -7 mol s -1 ) R2R2 d[Tol]/dt ( 10 -7 mol s -1 ) R2R2 1%(Au-Pd)/TiO 2 - 0.795 ± 0.0430.9590.422 ± 0.024 0.9660.373 ± 0.027 0.941 0.5%Au/TiO 2 -0.0367 ± 0.00320.9920.0373 ± 0.002 0.9970.000494 ± 0.000114 0.951 0.5%Pd/TiO 2 - 0.404 ± 0.1300.9100.260 ± 0.078 0.9210.144 ± 0.056 0.877 Catalyst: 0.02g Benzyl Alcohol: 1g He: 1 bar Stirring: 1000rpm Monometallic versus Bimetallic Catalysts No reaction in the absence of catalyst

37. Reaction of PhCH 2 OH versus PhCD 2 OH Rate of disappearance of benzyl alcohol ▲(Proton) ● (Deuterated) under 1 bar He Under Oxygen (1 bar) SubstrateBenzyl AlcoholBenzaldehydeToluene d[BzOH]/dt ( 10 -7 mol s -1 ) R2R2 d[Ald]/dt ( 10 -7 mol s -1 ) R2R2 d[Tol]/dt ( 10 -7 mol s -1 ) R2R2 PhCH 2 OH-5.42 ± 0.460.9864.808 ± 0.460.9820.755 ± 0.150.950 PhCD 2 OH-2.05 ± 0.140.9931.867 ± 0.130.9930.222 ± 0.030.974 KIE 2.652.58 3.41 Substrate: 1g Catalyst: 0.02g O 2 : 1bar Stirring: 1000 rpm Temp: 80 o C

38. Deuterium NMR (coupled) of the reaction mixture (inset toluene peak magnified)

39. GC- Mass analysis of the reaction mixture – Comparison of protonated toluene and deuterated toluene part alone shown for clarity.

40. Effect of atmosphere on the initial rate of reaction Gas/PressBenzyl AlcoholBenzaldehydeToluene d[BzOH]/dt ( 10 -7 mol s -1 ) R2R2 d[Ald]/dt ( 10 -7 mol s -1 ) R2R2 d[Tol]/dt ( 10 -7 mol s -1 ) R2R2 He-0.795 ± 0.040.9590.422 ± 0.020.9660.373 ± 0.030.941 Air-2.288 ± 0.170.9891.454 ± 0.090.9920.832 ± 0.090.976 O 2 / 1 bar-5.420 ± 0.460.9864.808 ± 0.460.9820.755 ± 0.150.950 O 2 / 2 bar-6.440 ± 0.290.9965.803 ± 0.290.9960.595 ± 0.050.987 O 2 / 3 bar-6.313 ± 0.380.9955.862 ± 0.350.9950.464 ± 0.060.980 Benzyl Alcohol : 1g Catalyst: 0.02g Temp: 80 o C Stirring: 1000 rpm Pressure: 1bar

41. Effect of dilution with o-xylene Lineweaver-Burk plot of initial rates versus formal concentration of benzyl alcohol Derive v max & K d K d ald << K d tol Active site for the two products Appears to be different

42. PhCH 2 H C HOPh H C PhHO O O. H CO O. PhH H HO H H PHePO1 PO2 Speculation on mechanism & structure of precursor states PhCH 2 OH PhCH 2 OH CAT PHe PhCHO PhCH 3 PhCH 2 OH/O 2 CAT PO1 PO2 PhCHO PhCH 3 O 2 He M. Sankar et.al., Faraday Discussions, 2009 (In Press)

43. Glycerol Oxidation – Possible Products

44. Oxidation of Glycerol in an autoclave reactor using O 2 or aq. H 2 O 2 M.Sankar, N. Dimitratos,D. W. Knight, A. F. Carley,R. Tiruvalam,C. J. Kiely, D.Thomas,and G. J. Hutchings*, ChemSusChem, 2010 (In press)

45. Acknowledgements  Dr. P. Manikandan, NCL Pune  Prof. Graham J Hutchings, Cardiff University  Prof. David W Knight, Cardiff University  Prof. Donald Bethell, Liverpool University  Dr. S. Sivasanker, NCCR, Chennai  Prof. B. Viswanathan, NCCR, Chennai  EPSRC & CSIR