Nanoporous Catalysts

Haruta, M. (2007) New Generation of Gold Catalysts Nanoporous Foams and... 

In addition, iron(II) complexes of tetraaza macrocyclic ligands 17-20 were encapsulated within the nanopores of zeolite-Y and were used as catalysts for the oxidation of styrene with molecular oxygen under mild conditions (Scheme 9) [57]. 

Figure 2.52 2-D model of a counter-current heat-exchanger reactor with a nanoporous catalyst layer deposited on the channel wall.

A nanoporous structure on the surface of the micro channels can be realized via anodic oxidation, thereby considerably enlarging the catalyst surface [17]. Catalysts... 

P 17] In order to have a catalyst with a sufficiently high specific surface area, pretreatment of the micro channels made of aluminum was necessary [17], Following a cleaning procedure, an oxide layer with a regular system of nanopores was generated by anodic oxidation (1.5% oxalic acid 25 °C 50 V DC 2 h exposure using an aluminum plate cathode followed by calcination). 

GL 18] [R 6a] [P 17] CFD calculations were performed to give the Pd concentration profile in a nanopore of the oxide catalyst carrier layer [17]. For wet-chemical deposition most of the catalyst was deposited in the pore mouth, in the first 4 pm of the pore. Hence most of the hydrogenation reaction is expected to occur in this location. For electrochemical deposition, large fractions of the catalyst are located in both the pore mouth and base. Since the pore base is not expected to contribute to large extent to hydrogenation, a worse performance was predicted for this case. 

The reduction of palladium(II) with an alcoholic solution of NaBH4 [101] or by treatment in situ of the methanol-swollen material under hydrogen [129] yielded a supported palladium catalyst, referred to as self supported by the authors [101,129]. The same co-polymerization reaction was carried out inside the nanopores of a DMF-swollen gel-type resin made by DMA and MBAA (crosslinker, 4% mol) [101,129], thus obtaining a sequential IPN [131]. Also this material was transformed into a... 

Figure 1.6 Top Low-temperature nitrogen adsorption ( ) and desorption (x) isotherms measured on a calcined SBA-15 mesoporous silica solid prepared using an EO20PO70EO20 block copolymer [54]. Bottom Pore size distribution derived from the adsorption isotherm reported at the top [54]. A high surface area (850 m2/g), a uniform distribution of cylindrical nanopores (diameter —90 A), and a large pore volume (1.17 cm3/g) were all estimated from these data. These properties make this material suitable for use as support in the preparation of high-surface-area solid catalysts. (Reproduced with permission from The American Chemical Society.)...

Pores are found in many solids and the term porosity is often used quite arbitrarily to describe many different properties of such materials. Occasionally, it is used to indicate the mere presence of pores in a material, sometimes as a measure for the size of the pores, and often as a measure for the amount of pores present in a material. The latter is closest to its physical definition. The porosity of a material is defined as the ratio between the pore volume of a particle and its total volume (pore volume + volume of solid) [1]. A certain porosity is a common feature of most heterogeneous catalysts. The pores are either formed by voids between small aggregated particles (textural porosity) or they are intrinsic structural features of the materials (structural porosity). According to the IUPAC notation, porous materials are classified with respect to their sizes into three groups microporous, mesoporous, and macroporous materials [2], Microporous materials have pores with diameters < 2 nm, mesoporous materials have pore diameters between 2 and 50 nm, and macroporous materials have pore diameters > 50 nm. Nowadays, some authors use the term nanoporosity which, however, has no clear definition but is typically used in combination with nanotechnology and nanochemistry for materials with pore sizes in the nanometer range, i.e., 0.1 to 100 nm. Nanoporous could thus mean everything from microporous to macroporous. 

Figure 3. Possible configuration of strategically-deposited catalyst atom on nanoporous silicon...

Janowska, I. Hajiesmaili, S. Begin, D. Keller, V. Keller, N. Ledoux, M.-J. Pham-Huu, C., Macronized aligned carbon nanotubes for use as catalyst support and ceramic nanoporous membrane template. Catal. Today 2009,145 76-84. 

M. S. Wong, H. C. Huang, and J. Y. Ying, Supramolecular-templated synthesis of nanoporous zirconia-silica catalysts, Chem. Mater. 14(5), 1961—1973 (2002). 

NANOPOROUS AND NANOSTRUCTURED CATALYSTS Self-Assembly AND Co-Assembly of Multiple Site-Isolated Catalytic Sites on Mesoporous Materials... 

New Synthetic Methods to Efficient Nanoporous and Nanostmctured Catalysts 83... 

---