FTIR study of Methanol decomposition on copper and gold catalysts supported on ZnO and on TiO2
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(2) sulfur pollutants unburnt hydrocarbons CO CO2 NOx particulate. ☺ H2 - fuelled engine But… using H2 for vehicle applications : " STORAGE " SAFETY. H2 on-board production from a liquid fuel. " REFUELING. Torino, 22-27 Giugno 2003.
(3) ! decomposition CH3OH. 2H2 + CO. ∆H >0. ! steam reforming CH3OH + H2O. 3H2 + CO2. ∆H>0. ! partial oxidation CH3OH + 1/2 O2. 2H2 + CO2. ∆H<0. ! combined or autothermal reforming CH3OH + (1-2a)H2O +aO2→CO2 + (3 –2a)H2 0<a<0.5 Torino, 22-27 Giugno 2003.
(4) ! Cu catalysts: rapid deactivation, Au catalysts: very active in CO oxidation, WGSR F. Boccuzzi, A. Chiorino, M. Manzoli, P. Lu, T. Akita, S. Ichikawa, M. Haruta, J. Catal., 2001, 202, 256. F. Boccuzzi, A. Chiorino, M. Manzoli, D. Andreeva, T. Tabakova, J. Catal., 1999, 188, 176.. ! Cu/ZnO & Au/ZnO. (co-precipitation method). ! Cu/TiO2 & Au/TiO2. Cu ≈ 8-10 at. % Au ≈ 5 at. %. (deposition-precipitation method). Interaction with 2 mixtures at increasing temperature pure CH3OH & CH3OH–H2O–O2 Torino, 22-27 Giugno 2003. (1:1:0.2 ratio).
(5) in situ spectra in controlled atmospheres & temperatures ! Produce H2 ! Clean-up of H2 fuel from CO ! Identify surface & gas phase species ! Understand the reaction mechanism on both Cu and Au catalysts Torino, 22-27 Giugno 2003.
(6) ! CH3OH interaction at r.t.: methoxy doubly bridged on Zn2+. undissociated CH3OH 1030. .25 A. .25 A 1058 2932 2822. CuZnO 3673 3620. 3450. AuZnO. 4000 3750 3500 3250 3000 2750. 1200. 1150 -1. On both catalysts:. CH3OH +. Wavenumber [cm ]. OH Zn2+ ZnO. 1100. 1050. CH3 O Zn2+ Zn2+ ZnO. Torino, 22-27 Giugno 2003. 1000. + H2 O.
(7) ! CH3OH interaction at increasing temperature: formates on Zn2+. 1058. .25 A 473 K. .5 A. 473 K 423 K. CO2. CO Cu-OH 2822 1575 2933 2308 HCHO 1369 3251 2866 1751. 3450. 2819. 373 K 4000. 3500. 3000. 2500. 2000 -1. Wavenumber [cm ]. ! QMS: CO & CO2. H2 starting from 423 K. Torino, 22-27 Giugno 2003. 1500. 1000. Au/ZnO.
(8) ! CH3OH-H2O-O2 interaction at increasing temperature:. Cu/ZnO. CO2 2354 1058 473 K. 2982. 473 K 423 K. 1377 1291 2947 2922. already at r.t., absent in CH3OH. 1350 2843. 1467. 373 K. 4000. 3500. 3000. 2500. 2000. -1. Wavenumber [cm ]. 1500. 1000. !band related to methoxy species less intense Torino, 22-27 Giugno 2003.
(9) About Cu & Au on the same support: Different thermal evolution & stability of the species: ! Au/ZnO (both CH3OH & MIXTURE: bands completely depleted at 473 K). ! Cu/ZnO. (at 473 K CH3OH: formates, MIXTURE: strong bands). ! O2 is probably adsorbed in atomic form on small. Cu and Au particles at the interface with ZnO. ! Highly basic oxygen sites extract H atoms from. –OCH3 species inducing the formation of carbon– containing species CxOyHz Torino, 22-27 Giugno 2003.
(10) ! CH3OH interaction at r.t.: undissociated CH3OH 2918 2817 2940. .5 A. -OCH3 on .5 A on Ti4+ top. -OCH3 doubly bridged on Ti4+ 1030 1055. -OCH3 on top on Ti3+. 1156. 1125. AuTiO2. 3726. CuTiO2. 3634. 4000 3750 3500 3250 3000 2750. 1250. 1200. 1150. 1100. 1050. 1000. -1. Wavenumber [cm ]. ! On TiO2: differently coordinated methoxy species Torino, 22-27 Giugno 2003.
(11) !CH3OH interaction at increasing temperature: formates on Ti4+ 1156. Au/TiO2. .5 A. 2923 2817. HCHO CO2. 473 K. 1755. 373 K. 4000. 1128. 1352 1560. 473 K 3730 423 K. 1055. 3642 3678. 3500. 3000. 2500. 2000 -1. Wavenumber [cm ] Torino, 22-27 Giugno 2003. 1500. 1000. formates on Cu.
(12) ! CH3OH-H2O-O2 interaction at increasing temperature: HCHO on on Au formates formates onAu Ti4+. .25 A. Cu/TiO2. CO2. 473 K. 29232829. 473 K. 2948. 2864. 1567. 423 K. 1632. 1357. 2731. 373 K. 3680 4000. 3500. 3000. 2500. 2000. -1. Wavenumber [cm ] F. Boccuzzi, A. Chiorino, M. Manzoli, J. Power Sources, 118 (2003) 304.. Torino, 22-27 Giugno 2003. 1500. 1000.
(13) About Cu & Au both supported on TiO2: 1156 cm-1. 1128 cm-1. OCH3 Ti4+. CH3OH, ∆T. TiO2. OCH3 Cu Ti3+ TiO2. Mixture: ! O2 enhances the formation of reaction intermediates on Au/TiO2 (formates on both metal & support). Torino, 22-27 Giugno 2003.
(14) CO adsorption at r.t. on Cu catalysts before & after CH3OH decomposition reactions stepped Cu0 surfaces. .25 A. Cu/ZnO 2114. 2107. before after. Cu(111) 2081. not fully reduced Cu. .25 A. stepped Cu0 surfaces. 2119 2108. Cu/TiO2. 2107. before after 2250. 2200. blue shift of the 2107 cm-1 band. 2077. 2150. 2100. Cu(111). 2050. -1. Wavenumber [cm ]. 2000. Cu sites: reduced, either agglomerated into larger particles or covered by residual species. ! A fraction of the surface metallic area (more uncoordinated & reactive sites) is no more able to adsorb CO Torino, 22-27 Giugno 2003.
(15) ! blue shift of the band at 2107 cm-1 Reducing atmosphere. Cu. ZnO. ZnO. P.L. Hansen, J.B. Wagner, S. Helveg, J.R Rostrup-Nielsen, B.S. Clausen, H. Topsøe, Science, 295 (2002) 2053.. Torino, 22-27 Giugno 2003.
(16) Mass Spectrometry results a.u.. H2. CO2. Cu/ZnO Au/ZnO. H2O. !. high. H2. &. CO2. amounts on Cu/ZnO. CH3OH. ! very low CO amount on Au/ZnO mass49. mass46. mass43. mass40. mass37. mass34. mass31. mass28. mass25. mass22. mass19. mass16. mass13. mass10. mass7. mass4. mass1. CO. ! Surface species, reaction intermediates & gaseous products in different relative amounts (depending on the nature of the metal & of the support) have been evidenced Torino, 22-27 Giugno 2003.
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