[...]... 420°C Absorption coefficient 18 .99 Figure 1. 3 NbPMo11VO40pyr 380°C reaction 19 19 . 01 19.02 19 .03 19 .04 19 .05 Energy (keV) NbPMo11VO40pyr EXAFS Nb-Mo Fourier transform Figure 1. 2 0 Nb-O 0.04 1 2 3 R (Å) 4 5 6 Left: Detailed view of the Nb K-edge XANES data of a pyridine salt of niobium-exchanged molybdo(vanado)phosphoric acid (NbPMo 11( V)pry) as a function of temperature [ 31] A change in niobium oxidation... Magnetic Resonance 16 1. 4.5 Electron Spin Resonance 18 1. 5 Surface- Sensitive Spectroscopies 19 1. 5 .1 X-Ray and Ultraviolet Photoelectron Spectroscopies .19 1. 5.2 Auger Electron Spectroscopy 20 1. 5.3 Low-Energy Ion Scattering 21 1.5.4 Secondary-Ion Mass Spectroscopy 21 1.6 Model Catalysts .22 1. 7 Concluding Remarks ... CRC_DK3277_ch0 01. qxd 3/8/2006 2 :13 PM Page 1 CHAPTER 1 Characterization of Heterogeneous Catalysts Zhen Ma and Francisco Zaera CONTENTS 1. 1 1. 2 Introduction 2 Structural Techniques 2 1. 2 .1 X-Ray Diffraction 2 1. 2.2 X-Ray Absorption Spectroscopy 3 1. 2.3 Electron Microscopy 5 1. 3 Adsorption–Desorption and Thermal Techniques 7 1. 3 .1 Surface. .. accessibility and photocatalytic activity of the vanadium centers after different catalyst pretreatments Special spin-trapping techniques are also available for the detection of short-lived radicals in both homogeneous and heterogeneous systems For instance, -phenyl N-tert-butyl nitrone (PBN), tert-nitrosobutane (t-NB), -( 4-pyridyl N-oxide) N-tert-butyl nitrone (4-POBN), or 5,5-dimethyl-1pyrroline N-oxide... enough for lowsurface-area ( 1 cm2) solids [ 71] This instrumentation has already been used in model systems to determine the energetics of bonding of catalytic particles to the support, and also in adsorption and reaction processes [72,73] © 2006 by Taylor & Francis Group, LLC CRC_DK3277_ch0 01. qxd 3/8/2006 2 :13 PM 12 Page 12 SURFACE AND NANOMOLECULAR CATALYSIS 1. 4 OPTICAL SPECTROSCOPIES 1. 4 .1 Infrared... 1. 3 .1 Surface Area and Pore Structure 7 1. 3.2 Temperature-Programmed Desorption and Reaction 8 1. 3.3 Thermogravimetry and Thermal Analysis 9 1. 3.4 Microcalorimetry .10 1. 4 Optical Spectroscopies 12 1. 4 .1 Infrared Spectroscopy 12 1. 4.2 Raman Spectroscopy 13 1. 4.3 Ultraviolet–Visible Spectroscopy 15 1. 4.4 Nuclear Magnetic... 10 % Ni/Al2O3 IR vs T in O2 atmosphere 0 .1 (7) 670 K in 10 torr O2 Transmittance (6) 530 K in 10 torr O2 (5) 490 K in 10 torr O2 (4) 450 K in 10 torr O2 (3) 440 K in 10 torr O2 (2) Heated at 400 K (1) 10 Torr 2-ProOH at 300 K; then pumped 12 00 15 00 18 00 210 0 2400 2700 3000 Frequency (cm 1) Figure 1. 12 Transmission IR spectra obtained during the oxidation of 2-propanol on a Ni/Al2O3 catalyst as a function... catalyst [17 3] Gold clusters of 1 to 6 nm diameter were deposited on TiO2 single-crystal surfaces in a controlled fashion, and the samples characterized under ultrahigh vacuum in order to correlate physical properties with activity STM and reaction SFG signal (a.u.) CH3 C 2876 cm 1 ethylidyne SFG PH =11 0 torr 2 PC2H4 = 35 torr H2C−CH2 2 910 cm 1 di- ethylene T = 295 K Pt (11 1) surface H2C−CH2 2992 cm 1 ethylene... spectroscopies, including field emission microscopy (FEM) [17 5], field ion microscopy (FIM) [17 6], scanning tunneling and atomic force microscopies (STM and AFM, respectively) [17 7 ,17 8], photoemission electron microscopy (PEEM) [17 9 ,18 0], electron tomography [18 1], ellipsometry [18 2], luminescence spectroscopy [18 3], SFG [18 4 ,18 5], and Mössbauer spectroscopy [18 6 ,18 7], among others, have also been used for the... by Taylor & Francis Group, LLC CRC_DK3277_ch0 01. qxd 3/8/2006 2 :13 PM Page 19 CHARACTERIZATION OF HETEROGENEOUS CATALYSTS ESR of VS -1 •H 19 g = 1. 915 , A = 14 8 G || || 10 0 G •H (a) Reduced g = 1. 932, A = 18 3 G || || (b) Hydrated g = 1. 988, A = 65 G || || Figure 1. 17 (a) ESR spectrum from a vanadium silicate catalyst after photoreduction with H2 at 77 K [13 8] The ESR data obtained indicate the existence . States of America on acid-free paper 10 9876543 21 International Standard Book Number -1 0 : 1- 5 744 4-4 8 1- 6 (Hardcover) International Standard Book Number -1 3 : 97 8 -1 -5 744 4-4 8 1- 0 (Hardcover) Library. recording, or in any information http://www.taylorandfrancis.com http://www.crcpress.com ISBN 1- 5 744 4-4 8 1- 6 (US-HC) ISBN 3 -1 3 -1 4029 1- 1 (GTV) 1. Catalysis. 2. Surface chemistry. 3. For permission to photocopy. reaction Nb K edge NbPMo 11 VO 40 pyr NbPMo 11 VO 40 pyr Absorption coefficient 18 .99 19 .0 519 .0 419 .0 319 .0 219 . 011 9 Energy (keV) EXAFS Fourier transform Nb-O 0.04 Nb-Mo 43 210 56 R (Å) Figure 1. 3 Left : Detailed