Fiber catalysts

Nano fibers are well suited as catalyst support owing to their high surface area and the good accessibiUty of the active sites. 

1 FiberCatalysts As an alternative to foams, fibrous materials in the form of tissues or filters may be used as structured catalysts [43-50]. The characteristic properties of fibrous materials as catalyst supports are compared with catalyst pellets and monoliths in Table 11.2. 

Properly Pellet Monolith Fibrous structure (wire mesh, cloths) 

Cooling water channel Reaction-side cooling slit Cooling tube- 

1) Negligible influence of fluid-soM mass transfer phenomena 

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Recently, many papers have been published on fiber catalysts and foam structures (Figure 9.2). Although, strictly speaking, fibers and foams might not be considered as structured systems, beds of such catalysts exhibit typical features of structured catalysts, namely, low pressure drop, uniform fiow, a good and uniform access to the catalytic surface, and they are definitely nonrandom. Therefore, we have included them in this chapter. 

Figure 9.2 Fiber and foam structures, (a) Knitted silica fibers catalyst. (Reprinted from [7].) (b) Woven active carbon fiber catalyst. (Reprinted from [8].) (c) Aluminum foam. (Reprinted from [9].)...

Investigations of gas-phase processes in the presence of fiber catalysts focused on oxidation, SGR, and synthesis of chemicals. Oxidation studies of CO [68-71],... 

Physisorption measurements showed that carbon nanomaterials exhibit rather meso- and macroporous structures (maximum micropore fraction, 15% see Table 2.1). The lowest specific surface area was measured with the platelet fiber catalyst exhibiting slightly more than 100 m2/g. The Co/HB material offers 120 m2/g of surface area, and the highest BET value was determined with the Co/ MW catalyst featuring nearly 290 m2/g. Carbon nanomaterials, though, are not really porous, as the space between the graphene layers is too small for nitrogen molecules to enter. The only location of adsorption is the external surface of the nanomaterials and the inner surface of the nanotubes. 

Aumo, J., Oksanen, S., Mikkola, J. P., Salmi, T. and Murzin, D. Yu., Novel Woven Active Carbon Fiber Catalyst in the Hydrogenation of Citral, Cat Today 102-103 (2005), 128-132... 

The design of stirred reactors with hollow fiber catalysts for Michaelis-Menten kinetics (with C. Georgakis and P.C.-H. Chan). Biotechnol. Bioeng. 57, 99-106 (1975). 

FIGURE 5 Fiber structures left, knitted silicon fibers catalyst (6) right, woven carbon fibers (7). 

Use Solvent for vinyl resins and acetylene, butadiene, acid gases poly acrylic fibers catalyst in car-boxylation reactions organic synthesis carrier for gases. 

FIGURE 7 Schematic illustration of a sandwich reactor (top) and scanning electron microscopic images of a sintered metal fiber catalyst. 

L. Kiwi-Minsker, I. Yuranov, B. Siebenhaar, A. Renken, Glass fiber catalysts for total oxidation of CO and hydrocarbons in waste gases, Catal. Today 54 (1999) 39. 

M. Grasemarm, N. Semagina, A. Renken, L. Kiwi-Minsker, Hydrodynamics of a bubble column reactor staged with sintered metal fiber catalyst for contiuous 3-phase hydrogenation, Ind. ling. Chem. Res. 46 (2007) 8602. 

Polysilicate. [DuPont] Polysilicate binder for refractory, ceramic, metal, inorg. fiber, catalyst support, inorg. paint systems, zinc coatings findustrial applic. glass surface modifier. 

The temperature programmed decomposition of the firesh and used Pd/SF-1173 catalyst indicated the presence of two PdO species on the catalyst surface. A single 02-evolution peak with maximum at 903 K took place from the fi-esh catalyst, whereas, on the aged catalyst two 02-evolution peaks with maxims at 948 K and 1053 K were observed. Similar twin 02-evolution peaks are also observed from alinnina supported Pd-catalysts [7]. The 02-evolution peak at lower temperatures is originating from the decottq>osition of crystalline palladium oxide, while the higher teitq)erature peak is due to the decomposition of the amorphous PdO. A comparison of the performances of the knitted silica-fiber catalysts with those over... 

Figure 3 TOF as a function of temperature over the Pt/silica-fiber catalysts (ph2 = 0.36. Pcxyi = 0.06 bar).

Liquid-phase hydrogenation of citrai (34 mol% cis- and 66 mol% trans-citral) was carried out at 343 K in a tubular glass reactor over Niloiitted silica-fiber catalyst containing 5, 10, 15 and 20 wt.% nickel [9]. Citronellal and citronellol were the primary and secondary products. Small amounts of nerol and geraniol were also detected. 

A knitted silica-fiber was produced and employed as a catalyst support. Different Pt, Pd and Ni/knitted silica-fiber catalysts were prepared. The activity of the catalysts was investigated in oxidation of volatile organic compounds, gas-phase hydrogenation of o-xylene, liquid-phase hydrogenation of citral and liquid phase enantioselective hydrogenation of 1-phenyl- 1,2-propanedione. 

In fixed-bed reactor technologies, an important factor is the pressure drop over the catalyst bed. In order to minimize the mass transfer effects, knitted silica fiber catalysts having small diffusion distance (< 10 pm) and low pressure drop, were applied in this study. 10 layers (0.4 g) of the catalyst was placed in the reactor between stainless steel nets and glass beads were used as inert packing material. The catalyst layer thickness was 0.15 cm resulting in catalyst bed length of... 

Hung, C. M. Activity of Cu-activated carbon fiber catalyst in wet oxidation of ammonia solution. J. Hazardous Mater. 2009,166(2), 1314-1320. 

Figure 11.19 Staged bubble column reactor with integrated structured catalyst layers and microheat exchanger (a) vertical cut through the heat exchanger element (b) and sintered metal fiber catalyst (c) [53]. (Adapted with permission from Elsevier.)...

Example 6, A -Methylpiperazine-Functionalized Polyacrylonitrile Fiber Catalyst ... 

Glass fiber catalysts for total oxidation of CO and hydrocarbons in waste gases. 

In the SMC process, typically the unsaturated polyester resin with styrene monomer along with the fillers, glass fibers, catalyst, and other additives are mixed together... 

FIGURE 9.13 (a) Three-phase continuous hydrogenation of an organic compound over a metal supported on silica fibers, (b) A scanning electron microscopy (SEM) image of a knitted silica fiber catalyst. 

FIGURE 9.14 An SEM image of Pt on Kynol -activated carbon fiber catalyst. 

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