Catalysts specific surface areas

Disk holder material Polypropylene Catalyst specific surface area 3.6 0.4 m g ... 

The physical properties of the catalyst (specific surface area, porosity, effective thermal conductivity, effective diffusivity, pellet density, etc.). 

Large particles (diskettes) were formed by applying a spark plasma sintering process to leached catalyst particles. Almost all of the catalyst specific surface area was retained after sintering. This may open a way to manufacture pellet type catalysts or electrodes with high specific surface area. 

Figure 36 Catalyst-specific surface area as a function of operation temperature. P = 3.4 kg cm 2 flow rate of oxidative mixture (5.04% vol oxygen in nitrogen) = 325 cm min period of contact with oxidative mixture = 24 h 0= sample A = sample B A = sample...

Besides, it has been claimed that a proper design of the catalyst morphology (ie, specific surface area and pore size distribution) with a good balance between macropores (to speed up diffusion of reagents and products) and micropores (to sustain the reaction by providing high catalyst specific surface area) can lead to superior catalytic performances (46—48). These points will be addressed in the section Optimization of Catalyst Morphology. 

Another advantage of the GSC method is its applicability for a short time of contact between adsorbate and adsorbent, which is not possible for static methods. This applies to measurements of adsorption on catalysts and studies of catalyst specific surface area at higher temperatures, close to the working temperature as well as adsorption on polymers. In this latter case static methods do not distinguish between adsorption and absorption. 

Comparative study of the structiiral characteristics (Sgp, Vj.) of the oxide vanadium-titanium catalysts has shown that the texture starts to form even at the stage of catalyst batch formation. When the plasticizer nature is varied, catalyst specific surface area (Sgp) and pore volxune (V ) remain practically... 

Cathode exchange current density is 1 x 10" °A/cm of Pt surface (measured with oxygen at 25°C and atmospheric pressure). Calculate the expected current density at 0.9 V (iR corrected) if an MEA is prepared with catalyst specific surface area of 640cm /mg and with Pt loading of 0.4mg/cm and the cell operates with Hi/Air at 60°C and 300 kPa. What potential gain may be expected at same current density if the Pt loading on the cathode is increased to 2mg/cm ... 

After it is washed, dried, and granulated, this silica gel has a very high specific surface area (about 700 m2-g 1) and is useful as a drying agent, a support for catalysts, a packing for chromatography columns, and a thermal insulator. 

Table 1. Specific surface area and acidity of Ni0-Ti02/15-W03 catalysts containing different NiO contents and calcined at 400"C for 1.5 h...

Nitrogen adsorption experiments showed a typical t)q5e I isotherm for activated carbon catalysts. For iron impregnated catalysts the specific surface area decreased fix>m 1088 m /g (0.5 wt% Fe ) to 1020 m /g (5.0 wt% Fe). No agglomerization of metal tin or tin oxide was observed from the SEM image of 5Fe-0.5Sn/AC catalyst (Fig. 1). In Fig. 2 iron oxides on the catalyst surface can be seen from the X-Ray diffractions. The peaks of tin or tin oxide cannot be investigated because the quantity of loaded tin is very small and the dispersion of tin particle is high on the support surface. 

We have also tried the trapping reactor system, in which ammonia is trapped on the catalyst/adsorbent and microwave is irradiated intermittently. However, due to the small specific surface area and the small ammonia adsorption capacity on the employed CuO, the trapping system was not effective compared to the continuous irradiation. Further study should be made to develop a material having high ammonia adsorption capacity and high efficiency for microwave absorption. Supported CuO on high surface area material or preparation of high surface area CuO can be effective. 

Adequate description of many catalysts will require a large number of bits of data since they are usually rather complicated materials rather than simple chemicals. Attempts at tMs were just beginning by ICC 1, but now, one expects authors to give specific surface areas and some details of the porosity of their catalysts. Automation of the former tedious point by point measiirement of the N2 adsorption isotherm has greatly facilitated this. 

Specific surface areas of the catalysts used were determined by nitrogen adsorption (77.4 K) employing BET method via Sorptomatic 1900 (Carlo-Erba). X-ray difiraction (XRD) patterns of powdered catalysts were carried out on a Siemens D500 (0 / 20) dififactometer with Cu K monochromatic radiation. For the temperature-programmed desorption (TPD) experiments the catalyst (0.3 g) was pre-treated at diflferent temperatures (100-700 °C) under helium flow (5-20 Nml min ) in a micro-catalytic tubular reactor for 3 hours. The treated sample was exposed to methanol vapor (0.01-0.10 kPa) for 2 hours at 260 °C. The system was cooled at room temperature under helium for 30 minutes and then heated at the rate of 4 °C min . Effluents were continuously analyzed using a quadruple mass spectrometer (type QMG420, Balzers AG). 

Supported iron catalysts are notoriously difficult to reduce [6-8] and thus a substantial fraction of the iron can be expected to remain inactive for the catalysis of hydrogenation. Particular attention has therefore been paid to the preparation of Fe/MgO catalysts by several different methods and examination of their effectiveness in producing metallic iron of adequate specific surface area after reduction in hydrogen. The activity and selectivity for primary amine formation have been determined for the hydrogenation of ethanenitrile (acetonitrile) and propanenitrile. 

Table 2 also lists the noble metal surface areas normalized to the total mass of the catalyst. The surface areas were calculated directly from the dispersion data taking into account the different mass of noble metal in each cataly and assuming a constant site density of 1x10 /m As with dispersion, no clear correlation exists between mass-specific noble metal surface areas and CO/NOx cross-over efficiencies. 

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