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1、Towards Total Design of Towards Total Design of Heterogeneous CatalystsHeterogeneous Catalysts Harold H. Kung Chemical Engineering Department Northwestern University Evanston, IL 60208-3120 October 13, 2003 What would one like to accomplish in total catalyst synthesis? Shape of the cavity Path to ca
2、vity Ability to design and position ancillary groups Complete atomic control of active site (metal, oxide) Metal Crystallite Catalytic Active Phase Surface arrangement of atoms Composition Nature of support Location of crystallite on support (defect sites) Structure sensitivity Electronic effect Lig
3、and effect Metal clusters derived from metal carbonyl complexes BC Gates J. Molec. Catal. A Chem 163 (2000) 55 Os5C on MgO Ir4 in zeolite Size-selective cluster beam deposition of Aun clusters on MgO Heiz, Sanchez, Abbet, Schneider, Chem. Phys. 262 (2000) 189. MS signal of C16O18O in TPD after expos
4、ure to 18O2 and then CO Aaron S. Eppler, Gnther Rupprechter, Lszl Guczi, and Gabor A. Somorjai, J. Phys. Chem. B 101 (1997) 9973. Array of Pt on silica Deposition of metal clusters using lithography Insufficient control of shape, exact size, and atom locations; current limit on smallest size achieve
5、d. P-SO32- + Mn+(aq) P-SO32-Mn+ P-SO32-Mn+ + NaBH4 P-SO32-/Mo Preparation of uniform sized metal particles using functional resins Corain, Centomo, Ferrari Meyer-Zaika, Schmid, Gold2003, October 2003. Control of surface coordinative unsaturation sites of aluminum oxide (Al2O3) by synthesis Active si
6、tes are surface exposed Al ions (Lewis acid sites). Al O Al O O Al O O O Active site AlAl OR OR RO RO R O O R NRH2 H2O O H2 R N AlAl O O O H2 R N Strategy: use amine (Lewis base) to preserve Lewis acidity. Al OR NRH2 RO RO 2 monomer Can make monomer Amine protection is retained Final solid an active
7、 catalyst Kozlov, Kung, Xue, and Kung, Angew. Chem. Int. Ed. 42(2003) 2415 Conversion of cyclopentene oxide in reaction with piperidine catalyzed by various aluminas. PPD-Al2O3, SG-Al2O3-200, SG-Al2O3-500-H2O-200, SG-Al2O3-500- H2O, PA-Al2O3-500-H2O-200 PA-Al2O3-500-H2O, blank. Xue, Kung, Kozlov, Po
8、pp, and Kung, Catal. Today, 2003. Generation of active site by building on a well-defined structure 001203c J.M. Thomas, et al. Nature 398 (1999) 227; Angew. Chem. Int. Ed. 39 (2000) 2310. Hexane ( ) Oxidation Two Co(III) ions in CoAlPO-18 at the desired distance apart in Co/P = 0.1 samples. CoAlPO-
9、36 of larger pore structure and shape, produces much more 3-ol and 3-one. Importance in controlling relative location of sites Raja and Thomas, J. Molec. Catal. 181 (2002) 3 29Si NMR of (Si-O)n oligomer units Atom-by-Atom Synthesis of Metal-Oxygen Chain Chang, Kung, and Kung, Chem. Comm. submittted.
10、 Metal-Oxygen Backbone of Designed Sequence and Structure OSiM Molecular templating: A. Katz and M.E. Davis, Nature 403 (2000) 286. Introduce functional groups at specific locations in the cavity. Molecules diffuse through silica wall into and out of cavity. Preparing sites with predetermined spacin
11、g Dufaud and Davis, JACS 125 (2003) 9403 Table 3. Synthesis of Bisphenol A with Sulfonic Acid Functionalized SBA-15 Silicas and para-Toluene Sulfonic Acida per site yield of bisphenol Ab p, p/o, p molar ratio catalystfunctional groupGCcNMRdGCcNMRd para-toluene sulfonic acid CH3aryl-SO3H 36 29 2 2.6
12、1-propane sulfonic acid CH3CH2CH2-SO3H 9.6e n.d.f 1.8e n.d. 11SBA Si-CH2CH2aryl-SO3H 13 11 3 3.0 9SBA Si-propyl-SO3H 8.8 8.4 10 6.4 10SBA Si-propyl-SO3H HO3S -propyl-Si 18 18 12 8.3 Vronique Dufaud* and Mark E. Davis* , J. Am. Chem. Soc., 125 (31), 9403 -9413, 2003 What would one like to accomplish
13、in total catalyst synthesis? Shape of the cavity Path to cavity Ability to design and position ancillary groups Complete atomic control of active site Eliminated pore diffusion control, Little shape selectivity. A. Corma, U. Diaz, M.E. Domine, V. Forns, Angew. Chem. Int. Ed. 39 (2000) 1499. (h00) K.
14、 Polborn and K. Severin, Chem. Commun. (1999) 2481-2482. Molecular Imprinting Cat. 4 made from 2; control cat. 5 made from 1 RP RP Active At rest Molecular hinges to control accessibility of active sites Figure 1 Molecular model of endoclucanase 12A and schematic model of the DMAAm-enzyme molecular
15、switch. The red residues represent the catalytic glutamic acid side chains at the active site of EG 12A, the green residue is the Asn 55 position, the purple residue is the Ser 25 position, and the N-terminus is represented as the blue circle. Tsuyoshi Shimoboji, Edmund Larenas, Tim Fowler, Allan S.
16、 Hoffman,* and Patrick S. Stayton* Bioconjugate Chem., 14 (3), 517 -525, 2003 Figure 4 Characterization of ONPC enzyme activities for free DMAAm- EG 12A conjugates in solution at as function of polymer size and conjugation site. The enzyme activities were measured for 100 nM conjugates using ONPC (8mM) as a substrat
