Catalysts apparent density

Catalyst Apparent density of particle or pellet (g/cm3) Equivalent diameter (m2/g) K (cm3/g) total... 

Rj -reaction rate for reaction j (mole/kg.s) ttji -stoichiometric coefficient of compound i for reaction j. -catalyst apparent density (kg/m ). 

The ortho-para conversion of molecular hydrogen is catalyzed by NiO. A supported catalyst is available with a specific surface area of 305 m2/g and a void volume of 0.484 cm3/g. A spherical catalyst pellet has an apparent density of 1.33 g/cm3 and a diameter of 0.5 cm. If the system is not far from equilibrium, an apparent first-order rate constant (kr) can be defined in the following manner. 

Hydrogenations were also carried out in 100% ethyl pyruvate and the results are shown in Figure 8. It should be noted that the turnover frequencies are lower than those observed in toluene (compare Fig. 7. with Fig. 8.). But more importantly, both TOF and ee s increase with particle size Gas-liquid resistance can be excluded since KLa for H2 transfer into ethyl pyruvate has been measured and is also about 0.06 s 1 at 600 RPM. Further, intraparticle control is unlikely because the TOF s should decrease with panicle size. Hence, we think that these observations can be explained by liquid-solid mass transpon effects as follows. The apparent density of the catalyst... 

Regenerator dimensions Reactor dimensions Catalyst retention in reactor Catalyst retention in generator API of raw oil feed Reactor pressure Regenerator pressure Average particle size Pore volume of catalyst Apparent bulk density Catalyst surface area... 

Figure 12.7 illustrates that, with the applied catalyst, reaction rates of up to tm 4 x 10-7 mol g-icat s could easily be achieved. This corresponds (with an apparent density of the catalyst of 1.2 g cm-3) to a STY of ca. 0.5 mol m 3 s (which is close to the value given in Eq. (28)). 

P - (Vp - vv / Vp), vanadium free fraction of catalyst pores, (-). r = instantaneous effectiveness factor, -), pc = apparent density of the catalyst, g / cucm. 

Several catalyst densities are used in the literature. True density may be defined as the mass of a powder or particle divided by its volume excluding all pores and voids. In a strict physical sense, this density can be calculated only through X-ray or neutron diffraction analysis of single crystal samples. The term apparent density has been used to refer to the mass divided by the volume including some portion of the pores and voids, and so values are always smaller than the true density. This term should not be used unless a clear description is given of what portion of the pores is included in the volume. So-called helium densities determined by helium expansion are apparent densities and not true densities since the measurement may exclude closed pores. 

Bulk density, or packing density, includes all pores and voids (interparticle spaces) in its calculation. It is determined by filling a graduated cylinder, with or without tapping. It follows that the value obtained is dependent upon the form of the catalyst (powder, tablets, extrudates) because of the different contribution of interparticle void space to the pore volume. Tap density is the apparent density of a bed of particles in a container of stated dimensions when a given amount of powder is vibrated or tapped under controlled conditions. The use of the term bulk density should be... 

However, if the reactor is filled, for example, with a catalyst, the situation becomes more complicated. The Vr would be the empty volume of the reactor, which is then difficult to determine, for instance, using settled apparent densities. The residence time can also be experimentally determined, usually resulting in a residence time distribution however, the experimental effort for such experiments is often large. Therefore, it is useful to apply a modified residence time, as shown in Equation (27), which defines the ratio of the mass of the catalyst and the gas flow, two easily measurable values ... 

The method of preparation involves mixii of polymeric isocyanate ( crude MDI) with the polyol, surfactant, catalyst and blowing agent, trichlorofluoromethane (fluorocarbon F-1 IB). The amounts of the latter and of the catalyst were chosen so that the apparent density was... 

Catalysts of wood pyrolysis are used to increase the yield of charcoal and to obtain a charcoal with modified properties or to produce definite valuable volatile products. The substances promoting condensation reactions are employed if high jields of charcoal are desired (4, 5, 7). Some catalysts increase the apparent density of charcoal, the pore dimensions and their adsorbency nature. Of all silvichemicals charcoal is currenUy the most in demand Commercial interest is focused on deciduous wood charcoal or charcoal briquettes. 

The direct contact model has some difiiculties, however. In fluidized beds, gas bubbles of very low solid content are usually considered to exist in the dense phase (H14, K13, T19). Also, the cloud layer is negligibly thin, due to small (/ r for the usual fluid catalyst beds, according to equa-ticMis of Davidson and Harrison (D3) and Murray (M47). The streamlines of gas phase through a bubble have been observed to pass through the cloud, but not through the bubble wake (R17). Thus there seems little possibility of believing that the bubble gas is in direct contact with a substantial amount of catalyst in the bubble phase (see also Secticxi VI,A). Furthermore, the direct contact model is applied to the data by Gilliland and Knudsen, and v in Eq. (7-9) is calculated to fit the data. Calculation (M26) shows that the volume of catalyst, with an apparent density the same as for the emulsion, which contacts the bubble gas freely exceeds the volume of bubble gas itself (v/ib = 3.3, 2.0, and 1.5, respectively, for Uc. = 10, 20, and 30 cm/sec). This seems to be unsound physically. 

A difference is observed between the structural paranrieters of the used, partially deactivated vanadium catalyst, and those of the fresh catalyst (Table 1). A decrease in the specific surface area and an increase in the picnometiic (solid) and apparent densities of the used sample should be noted. 

ASTM D 4180 - 82, Vibrated apparent density of formed catalyst particles. 

Activity of the unit of a catalytic layer volume is very important characteristics of the catalyst, which depends on the activity per the weight unit as well as on apparent density of the layer. For bulk ZrFe intermetallides (fraction 2-3 mm), the apparent density ( 3 g/cm ) is much higher than that for composite catalysts ( 1 g/cm ). However, enhancement of AC specific activity due to... 

Granulated Fe/Zr02 catalysts obtained via impregnation of zirconia support have an apparent density of the fixed bed catalyst layer about 1 g/cm [5]. For these catalysts, the rate of hquid hydrocarbons production varies from 6 to 15 gcnx/1 hr. Obviously, extrapolation of these data obtained for 20-40 pm... 

D. N. Miller and R. S. Kirk [AIChE J., 8, 183 (1962)] studied the kinetics of the catalytic dehydration of primary alcohols to produce the respective olefins. These investigators employed a TCC silica-alumina catalyst in a fixed bed reactor operating at 1 atm and temperatures from 400 to 700° R The catalyst is characterized by a specific surface area of 350 rc /g and a porosity of ca. 0.5. Within the bed the apparent density of the catalyst is 1.15 g/cm. The density of the nonporous bulk solid silica-alumina is 2.30 g/cm. The catalyst received from the vendor was sieved to obtain five sets of particles with apparent particle diameters equal to 0.40, 2.30, 3.05, 4.06, and 5.11 mm. 

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