Cobalt frequency factor

The availability of a spin-free state at the right energy does not mean that the species use that path. The frequency factor may be too low, either as a result of the Aig T2g transition rate being too slow to compete with other paths, or because the lifetime in the T2g state is too short to allow the requisite atomic motion for substitution. A longlifetime would facilitate reduction of cobalt(III) to cobalt(II). In fact, cobalt(II) species are often found in cobalt(III) products when low ligand field ligands are involved in substitution reactions. 

UPRs based on a mixture of maleic anhydride, phthalic anhydride and adipic acid in a molar ration of 1 2 2 were prepared in the presence of the polyesterification catalysts, i.e. lead dioxide, p-toluenesulfonic acid monohydrate and zinc acetate dihydrate, and next crossHnked with styrene by using MEKP as the initiator and cobalt naphthenate (CoNp) as the promoter [197]. Most often, the catalysts used in the polyesterification process cannot be easily separated from the polyester, thus the effect of the residual catalysts on the curing process and color of the cured polyester resin should be taken into account. It was shown that the residual catalyst could affect the curing reaction even in a small amount (Table 28), increasing the activation energy a, frequency factor ko and the reaction order x. 

Ferromagnetic resonance (PMR) spectra of cobalt mcial were recorded at X-band frequencies on a Varian E-4 spectrometer. DPPH and weak pitch were used as standards for g factor. Transmission electron microscopy (TEM) was done with JEOL 200CX microscope using 160 KeV electrons. 

Fischer-Tropsch activity, selectivity and deactivation data obtained in fixed bed reaction tests of Co/Si02 catalysts are summarized in Table 1. The turnover frequencies (TOFs) or site time yields based on H2 uptake and on rate measured after 20 hours of reaction agree within a factor of two with those reported for other cobalt catalysts [2, 3, 25-27]. CO conversion and methane selectivity versus time for Cab-O-Sil supported cobalt at both low and high space velocities are shown in Figure 1. It can be seen that at high conversion the catalyst deactivates rapidly while at low conversion the catalyst appears to be stable. The conversion is proportional to the water partial pressure thus water could be causing this deactivation. 

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