Beads catalyst

This was explained by having only the contribution of surface reaction in the case of batch processing, whereas micro reactors profit, in addition, from processing inside the pores of the catalyst beads. The penetration of the reaction solution into the pores is achieved here by applying pressure [2]. By this means, the number of available catalyst sites is increased. 

Figure 7. SEM and XRMA microphotographs of palladium catalysts supported on the amphiphilic resin made by DMAA, MTEA, MBAA (cross-linker) [30]. Microphotographs (a) and (b) show an image and the radial palladium distribution after uptake of [Pd(OAc)2] from water/acetone the precursor diffuses only into the outer layer of the relatively little swollen CFP after reduction the nanoclusters remain close to the edge of the catalyst beads. Microphotographs (c) and (d) show the radial distribution of sulfur and palladium, respectively, after uptake of [PdCU] from water after reduction palladium is homogenously distributed throughout the catalyst particles. This indicates that under these conditions the CFP was swollen enough to allow the metal precursor to readily penetrate the whole of polymeric mass. (Reprinted from Ref. [30], 2005, with permission from Elsevier.)...

With these goals in mind, we have studied the distribution of the liquid phase in the course of the hydrogenation reaction in a catalyst bed comprised of 1-mm catalyst beads (Figure 5.4.5). The 2D images shown reflect the distribution of the liquid phase in a 2-mm thick axial slice upon variation of the liquid AMS flow rate. The results show that while the increase in the flow rate leads to larger liquid contents in the bed (and vice versa), a steady state operation of the catalyst bed with unchanging spatial distribution of the liquid is observed if the external conditions remain unchanged. 

Similar experiments were performed with beds comprised of 2-3-mm catalyst beads. In this case, a catalyst bed 3 cm in height was supported by a 2-cm layer of catalytically inactive beads of the same size (y-A1203 + 0.1% Mn, but without Pd). 

Fig. 5.4.6 Distribution of the liquid phase in particles (C) and the lower part comprising the bed comprised of 2-3-mm catalyst beads in inert beads (I) are labeled on the right-hand the course of AMS hydrogenation. Acquisition side of the figure. H2 temperature was 85 °C. of each image took 34 s sequential numbers Flow rates of H2 and AMS are given in Table of images shown are indicated in the figure. 5.4.1.

Further spectroscopic experiments were carried out with an operating reactor using a bed of 1-mm catalyst beads [13]. A 3D experiment with one spectral and two spatial coordinates was carried out, yielding NMR spectra for each pixel of a 2D axial slice. Figure 5.4.7 shows several representative spectra selected from the entire data set. The NMR spectra of neat AMS [Figure 5.4.7(d)] and cumene [Figure 5.4.7(f)] are provided for comparison, they were experimentally detected for bulk liquid samples (lower traces with narrow lines) and their lines were then mathematically broadened to 300 Hz (upper traces) to account for the broadening in the... 

For the purposes of this illustrative example, we wish to calculate the combined and effective diffusivities of cumene in a mixture of benzene and cumene at 1 atm total pressure and 510 °C within the pores of a typical TCC (Thermofor Catalytic Cracking) catalyst bead. For our present purposes, the approximation to the combined diffusivity given by equation 12.2.8 will be sufficient because we will see that the Knudsen diffusion term is the dominant factor in determining the combined diffusivity. 

Fig. 9. Magnified Pd EnCat catalysts bead and high-resolution electron microscope image of the surface of the polyurea matrix...

BEAD - Diffusion and Reaction in a Spherical Catalyst Bead System... 

Fig. 4. Fish eye burning in cracking catalyst beads. Appearance after partial bum-off (top), and coke concentration versus radius in beads for successive stages of buro-off (bottom) for three temperature regions (a) low, (b) intermediate, (c) high.

At the same time as the basic work was being done on the kinetics and difFusivity effects in coke burning, the kinetics of the processes that determined the CO/CO2 ratio from slow coke was investigated by Weisz (1966). Studies were made of the cumulative CO2/CO ratios for individual, whole, spherical catalyst beads. The results, shown in Fig. 28, scattered very badly. 

Fig. 28. The cumulative COj/CO ratio for coke bum-off on spherical catalyst beads versus combustion temperature in air (O) white amorphous silica-alumina ( ) green Cr02-containing amorphous silica-alumina (M) macroporous white catalyst. The weight (mg) of the bead tested is denoted by the numerals adjacent to the respective symbol. Dashed line represents intrinsic ratios from carbon combustion research. From Weisz (1966).

These observations are explained by the conversion of CO to CO2 on sites active for CO conversion, as the intrinsically produced CO makes its way out of the catalyst bead by diffusion. The greater the diffusion limitation, the more the CO conversion. Weisz gave the mathematical solution for two special cases of these phenomena and demonstrated that the above interpretation was correct. 

Pt. Density of the catalyst beads, lb/ D Diffusion-limited burning... 

Present catalysts are developed for process plant service where transient conditions are not a concern. Typical shift catalysts, such as copper-zinc oxide, are reduced in place and must be isolated from air. There is a need for smaller, high surface area catalyst beads on low-density monolith substrate to be developed without reducing activity. This need applies to all fuel processor catalyst, not just the shift catalysts. There is also a need to demonstrate that the low-temperature, PROX catalysts have high selectivity toward CO and long term stability under operating conditions. 

The images obtained during an experiment demonstrated the ignition of individual catalyst beads throughout the reactor. These beads disappear from the image completely or partially since only the liquid-filled catalyst particles and their parts are observed in the images. The oscillations of the liquid front were observed to persist for long periods of time and were only possible in the Operando mode. 

The decomposition of the catalyst beads can cause a secondary air pollution emission consisting of the particulate dust generated by abrasion of the surface of the catalyst. Operating cost for catalyst replacement varies directly with catalyst attrition rate. The system can process waste streams with VOC concentrations of up to 25% of the lower explosive limit (LEL). The proprietary catalyst contains up to 10% chromium, including 4% hexavalent chromium. This could lead to the emission of hexavalent chromium in some applications of the technology. 

The kinetics of the reaction of solid sodium iodide with 1-bromooctane were studied with a 95 % RS graft of polyethylene oxide) 6-mer methyl ether on 3 % CL polystyrene as catalyst (51)176). The rates were approximately first order in 1-bromooctane and independent of the amount of excess sodium iodide. The rates varied with the amount of the solid catalyst used, but there was not enough data to establish the exact functional dependence. All experiments employed powdered sodium iodide, magnetic stirring, and 75-150 pm catalyst beads. Thus the variables stirring speed and particle size, which normally are affected by mass transfer and intraparticle diffusion, were not studied. Yanagida 177) favors a mechanism of transfer of the sodium iodide by dissolution in the solvent (benzene) and diffusion to the catalyst particle... 

Immobilized enzyme beads with a diameter of 10 mm containing the same amount of the enzyme above are used in the same stirred-batch reactor. Determine the initial reaction rate of the substrate solution of 0.1 kinolm". Assume that the effective diffusion coefficient of the substrate in the catalyst beads is 1.0 x 10" cm s". ... 

Chu and Storrow (1952) >1 H Air Glass, steel, lead, Socony-Vaeuum catalyst beads Spheres 1-6 -... 

Electron Scan Microscopic Shot of Catalyst Beads... 

OPE Etching (min.) Rhodium Catalyst Beads Rh 3d Intensity (1000 counts/sec.) P 2p Intensity (1000 counts/sec... 

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