Silica mean particle size

After the catalytic runs no modification of mean particle size is observed for this last system. Conversly, Ru CO) deposited on silica-alumina is readily decomposed at 200°C to metallic particles of 1 nm mean size which are also catalysts for the F-T synthesis. The catalytic activity at 200°C is C i one tenth of the Y zeolite supported ones and methane is practically the only hydrocarbon formed. Electron microscopy examination of the catalyst after reaction reveals a drastic sintering of the... 

Table 2 Operating conditions and mean ] a silica support particle size of platinum deposition obtained on ...

Fig. 1 shows changes in the mean particle size ni as a function of time for raw materials ground in the mills at Opoczno and Paradyz. In all cases, in the initial grinding period, an intensive change of the mean particle size m takes place. For terracotta and silica ground at Opoczno,... 

Silica gel 60, the most versatile and most frequently used TLC sorbent, was taken as a basis. The mean particle size of this sorbent was optimized simultaneously, the particle size distribution was brought to within as narrow limits as possible (L- ) The sorbent material thus obtained was used t prepare HPTLC pre-coated plates silica gel 60, being followed subsequently by the development of other sorbents for processing into HPTLC pre-coated layers. The materials chosen were largely "reversed phase" sorbents, that is to say, chemically modified silica gels with a non-polar surface (, 8), as well as microcrystalline cellulose ( )""... 

Optimization of the mean particle size of silica gel 60 and the consequent reduction of the particle size distribution produced a number of advantages in HPTLC pre-coated plates silica gel 60 prepared from this improved material which the traditional TLC silica gel 60 pre-coated layers do not possess. These advantages are to be found not only in the already mentioned optimized mean particle diameter and the narrower particle size distribution, but also in the smoother suid more homogeneous surface of the plates, which leads to an increase in chromatographic performance. 

Previous studies of our work group demonstrated that isomaltose exhibits a distinct higher affinity towards certain dealuminated p-zeolites as opposed to other carbohydrates like fructose or glucose [94, 109]. Sucrose is not adsorbed at all. As a consequence, a process could be developed which directly removes the isomaltose from the reaction solution by adsorption onto zeolite. For this purpose a fluidized bed reactor has been utilized with a special focus on the separation of the two solid phases (Fig. 14). The biocatalyst containing entrapped dextransucrase is produced by the jet-cutter method [110] the alginate beads have a mean particle size of 0.5 mm. To accomplish an adequate high density of biocatalyst, silica flour (30% w/v) is included. The particle diameter of the second solid phase (zeolite) is adjusted to 10 pm. As a consequence, zeolite is loaded with isomaltose inside the reactor and can then freely exit the reactor together with the product solution, whereas the biocatalyst is retained inside the fluidized bed reactor [92, 94],... 

The following test materials have often been used FCC catalysts, aluminium oxide, silica gel, glass beads, silica or quartz sand, sea sand, coal and coal ash, petroleum coke, metal powders, resin particles, boric acid, and magnesite powder. Mean particle size ranges from 11 /un to 1,041 /rm, and particle density, from 384 kg/m3 to 7,970 kg/m3. According to Geldart s classification (1973), most of these materials belongs to Class A, some to Class B, and a few to Class D or C, as listed in Table II. 

Kieselguhr is the most used support. Improvements in supports have been made synthetic silica or silicates have shown better catalyst reproducibility from batch to batch, with an increase in Ni surface area and a decrease of mean particle size. 

It is important to note that present AccuSizer measurements were obtained with a particle-size threshold of 0.56 pm (the lowest possible size threshold available for this analyzer) and any LPC growth behavior for particles smaller than 0.56 pm could not be seen in these data. MLC pump extensive handling showed a slight increase in mean particle size and PSD of silica-H slurry, as will be discussed later. The above behavior of LPC may be attributed to the cumulative effects of low-intensity continuous shear application to the bulk volume of slurry handled at very high pump speeds in MLC pump. In Fig. 18.21b, the LPC trend for the complete 330 h of Test 1 is very similar to the first 45 h. 

Test 10 Silica-H was recirculated in MLC pump at 5000 rpm, 11 psi back pressure, 31.7turnovers/h, 41pm, for 24h (761 turnovers). LPC and PSD measurements (Figs. 18.31a-c) show results very similar to Test 8, with slight increase in mean particle size and an increase in LPC for size 0.56-0.60 pm. 

Our third applications example highlights the work of Nakano et al. in modeling structural correlations in porous silica. MD simulations of porous silica in the density range 2.2—0.1 g/cm were carried out on a 41,472-particle system using an iPSC/860. Internal surface area, ratio of pore surface to volume, pore size distribution, fractal dimension, correlation length, and mean particle size were determined as a function of the density, with the structural transition between a condensed amorphous phase and a low density porous phase characterized by these quantities. Various dissimilar porous structures with different fractal dimensions were obtained by controlling the preparation schedule and the temperature. 

Fig.15. FT-RAIRS spectra of CO adsorbed at 90K on alumina supported palladium particles, as a function of mean particle size [85] The two sets of spectra correspond to particles formed by depositing palladium at 90K or 300K. FT-RAIRS spectra are also shown for CO adsorbed at lOOK on silica supported Pd (pre-exposed to oxygen) following the annealing of the surface to various temperatures [86].

Major results Figure 14.16 shows the effect of mean particle size of spherical silica (flame-fused synthetic silica) on acoustic emission. The emission increases with the particle size of filler increasing. The source of this increase in acoustic emission is thought to be related to the fracture of particles, debonding of particles from... 

Figure 14.16. The effect of mean particle size of silica on total acoustic emission of epoxy filled with 70% silica. [Data from Ohta M, Nakamura Y, Hamada H, Maekawa Z, Polym. Polym. Composites, 2, No.4, 1994, 215-21.]...

According to details supplied by the manufacturer, the mean particle size is about 5 pm (spherical silica). 

The separation efficiency obtained in TLC is essentially determined by the mean particle size and the size distribution of the sorption agent used in the preparation of the layer. As can be seen from Fig. 4, the mean particle size of silica gel of a quality suitable for HPTLC is 5 pm, that of TLC quality ca. 11 pm and that of PSC quality (for preparative work) over 20 pm. In a very recent development, spherical particles with... 

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