催化功能材料 2.结构及性能的关系.ppt

3. Defect structure point defect linear defect (dislocation) Impurity Conductive mechanism of ZrO2 electrolyte. (a) Atomically resolved STM image of a defective FeO island (15 nm × 15 nm) (Vb = –100 mV, I = 0.02 nA); (b) Zoomed O vacancy clusters in (a); (c) Schematic drawing of missing O atoms (the blue balls with dotted lines) at fcc sites; (d) STM image from a perfect 1.0 ML FeO film (10 nm × 10 nm) (Vb = 800 mV, I = 0.6 nA). 马腾, 傅强, 姚运喜, 崔义, 谭大力, 翟润生, 包信和. 催化学报, 2010, 31(8): 1013-1018. Temperature of the top of catalyst bed (Tb) and furnace temperature (Tf ) 4. Surface acid or base sites A Lewis acid is defined to be any species that accepts lone pair electrons. A Lewis base is defined to be any species that donates lone pair electrons. Example: H+ is a Lewis acid, since it can accept a lone pair, while OH- and NH3 are Lewis bases, both of which donate a lone pair. Me3B + ?:NH3 → Me3B:NH3 Me3B←-NH3 Lewis diagrams showing the formation of the ammonium ion. BF3 + F- → BF4? SiF4 + 2 F? → SiF62? sp3d2 RCl +AlCl3 → R+ + AlCl4? Desorption Thermogravimetry and Calorimetry of Room-Temperature Adsorbed Pyridine (Py) and CO2 Molecules on the Test Magnesias IR νCCN spectra of pyridine (Py)-adsorbed species established on the various test magnesias following thermoevacution at 10-5 Torr and the temperatures indicated for 5 min. Example of acid catalysis Esterification mechanism Aldol condensations are irreversible. Acid and base catalyzed aldol mechanism Acid catalyzed dehydration Base catalyzed dehydration Zeolites are microporous crystalline aluminosilicates, composed of TO4 tetrahedra (T = Si, Al) with O atoms connecting neighboring tetrahedra. For a completely siliceous structure, combination of TO4 (T = Si) units in this fashion leads to silica (SiO2), which is an uncharged solid. Upon incorporation of Al into the silica framework, the +3 charge on the Al makes the framework negatively charged, and requires the presence of extraframework cations (ino