Active site number

A matrix in a particular canonical form Number of active sites Number of active sites of type SI Number of active sites of type SB... 

The isomerization of 1-hexene decreased with increased ruthenium loading as shown in Table 2. It is considered that with the increased active site number on the catalyst surface, CO adsorption improved, contributing to CO insert reaction and inhibiting the isomerization of 1-hexene. The formation of oxygenate increased with increasing Ru loading, see Table 2. 

Keywords Active site number catalysts Olefin polymerizatiOTi... 

Data on the dependence of active site number on monomer concentration might help in understanding the deviation from the low linear rate of polymerization with changing monomer concentration... 

For fractal description of low-temperature polycondensation process the authors [33] made use of the relationship, connecting accessible for reaction active sites number, which is supposed proportional to Q, and Devalue [40] ... 

Fe2+/Fe + of unreduced catalysts Exposed percentage/% Active site density A X 10 Active site number N X 10 TOF/s -1... 

Notes Dpe is the percentage of Fe atoms exposed on surface measured by chemisorption of CO Dk is the percentage of K atoms exposed on surface measured by chemisorption of CO2 A = Fe%- Dpe/55.85ST, active site density, mol-m N = ASt, active site number, mol-g TOF = r/(3600N) x 10 , turn-over frequency, s Sx is the BET total surface area. 

When promoters are the same, the surface active site densities of fused iron catalysts derived from the different iron oxides are not with the obvious differences, but all about (7- 8) x 10 mol-m , while the active site number approx. (0.9 - 1.2) X 10 mol g which is in the direct proportion to its specific surface area. It is seen from Table 3.32 that along with the variation of the precursor iron oxides, especially with the increasing content of FeO, the surface active site numbers are not increasing, but seem to be in decreasing tendency. It can be deduced from this that the reason why the Fei xO based catalysts show a higher activity than Fe304 based one is not the fact that the surface active site number of the former is higher than that of the latter. 

Ni face-face centered cubic crystals with a basic cubo-octahedral morphology, they found that B5 sites were only present on crystals with a size larger than ca. 1.5 nm. The maximum probability for B5 sites was found for particles of 1.8nm-2.5nm and for particles larger than that, the probability for B5 sites monotonically decreased. In Fig. 6.47, Jacobsen et have similarly counted the relative number of B5-type sites, which are part of edges on small Ru crystals with only hep (001) and (100) surfaces exposed. Prom Fig. 6.47, if crystal is too small, there is basically no B5 active site. After the active site numbers reaches maximum under the crystal size between 1.5nm-2.0nm, they may decrease with the growth of crystal grain, which is mainly caused by the rapid decline of edge atoms. 

Radhakrishnan, R. and Oyama, S.T. Reactant-probe method for estimating active site number in catalysis. J. Catal 2001, 204, 516-519. 

This example clearly shows that TPD and adsorption microcalorimetry are complementary techniques, and combination of these two techniques provides very good characterisation of active sites number, strength and distribution on particular solid material. 

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