Catalyst granule size

Table P6.11-2 Rate of Oxidation of HjS [mmol/(s-L of catalyst bed)] at Constant Space Velocity as a Function of Catalyst Granule Size...

Pore diameters and their distribution. Small pores limit accessibility of internal surface because of increased resistance to diffusion of reactants inwards. Diffusion of products outward also is slowed down and may result in degradation of those products. When the catalyst is expensive, the inaccessible internal surface is a liability. A more or less uniform pore diameter is desirable, but the distribution usually is statistical and only molecular sieves have nearly uniform pores. Those catalyst granules that are extrudates of compacted masses of smaller particles have tamodal pore size distribution, between the particles and within them. Clearly a compromise between large specific surface and its accessibility as measured by pore diameter is required in some situations. 

Ratio between the size of the polymer granule and that of the catalyst granule... 

Such a different conclusion can be understood by considering the difficulties connected to the experimental determination and the definition of Thiele modulus parameters, such as So and D. According to Chien, S means the catalyst primary particle size with a value of about 10 cm for a-TiCIj instead, in the Multigrain model, Sp seems to correspond to the size of the whole catalyst granule. 

From the relative rates observed for separate particles and of coprecipitated metal (assumed to offer complete intimacy for the intermediate) we might estimate (see ref. 6) as of the order of magnitude 3 in Rylander and Cohn s observation, which leads for various catalyst particle sizes (carbon granules) to an estimate of concentration of intermediate as follows ... 

To achieve dependable performance, it is important to consider the morphology and structure of the catalyst granule, in the addition to the nature of the active centers and the polymerization kinetics. Proper combination of these factors will allow for a porous structure consisting of crystal and properly-sized, homogeneously dispersed, primary particles within the growing polymer granule, allowing the monomer equal access to the active centers (Fig. 1). 

Local overheating of the catalyst granules is known to occur on account of exothermal catalytic reactions under the catalyst-adsorbent regeneration. This leads to the transformation of active alumina into corundum and to the reduction of specific surface area and porosity. Thus, the improvement of the catalyst thermal stability depending on that of the support is of a key importance, y-Alumina is the most thermally stable alumina since its transition to a- starts at the highest temperature, %- alumina is the least stable. The temperature of the transformation is influenced by various factors such as crystalline form, particle size and morphology, the nature of the gaseous atmosphere, additives (or impurities) etc. [35]. 

Many solid catalysts are used in the form of porous granules. The size is a compromise between the need for large specific surface and ease of... 

After reporting the initial parallel experiments, the authors report a pooled approach using a chemical encoding strategy (176 and 177, see Fig. 3). Both the palladium and the nickel systems were screened in the same reaction vessel. Upon reaction, two different sized beads of polyethylene were observed. Deconvolution indicated the larger polymer granules were from catalysis by the nickel catalyst. 

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