Open turnover frequency

Figure 2.3. Catalysis (0), classical promotion ( ), electrochemical promotion ( , ) and electrochemical promotion of a classically promoted (sodium doped) ( , ) Rh catalyst deposited on YSZ during NO reduction by CO in presence of gaseous 02.14 The Figure shows the temperature dependence of the catalytic rates and turnover frequencies of C02 (a) and N2 (b) formation under open-circuit (o.c.) conditions and upon application (via a potentiostat) of catalyst potential values, UWr, of+1 and -IV. Reprinted with permission from Elsevier Science.

The hydrogenolysis of DBT to 2-phenylthiophenol (PTP) is catalyzed by (triphos)Rh(H), generated in situ, at 160 °C and 30 atm H2 pressure with a very low turnover frequency (2 mol TPT mol Rh h ). The DBT ring-opened Ir complex (triphos)Ir(H)(jj -C,S DBT) catalyzes the formation of PTP in only 8% yield at 170 °C under 30 atm H2 pressure over a period of 24 h. Some biphenyl (5%), the completely desulfurized form of DBT, is also formed in the reactions, but the authors do rule out the possibility that the formation of this product is due to catalysis by a heterogeneous form of Ir. Therefore, there appear to be no unequivocal examples of HDS catalyzed by a homogeneous metal complex that results in the complete removal of sulfur from T, BT, or DBT. 

Figure 2 Sulphur Pseudo Turnover Frequency (atoms S converted ks 1 ran Versus Time on Stream (hours) - open circles (solid line), solid circles (dotted line), and solid squares (dashed line) represent the 3.2 mm and the 1.6 mm alumina supported catalysts, and the carbon supported catalysts respectively...

Fig. 18. Turnover frequencies for CO hydrogenation over a series of Rh/Ti02 catalysts as a function of the pH of the solution used in the impregnation step in the preparation following reduction at 473 K (solid points) following reduction at 773 K (open points). (Data taken from Ref. 46.)...

PrCL) and 6-n-butyl-e-caprolactone (6-BuCL) were synthesised and subjected to a Novozym 435 catalysed ring-opening. The turnover frequencies (TOP) and the enantiomeric ratio E, which is a measure of the enantioselectivity of the enzyme for the lactone, were derived from the kinetic plots. 

Figure 6. Turnover frequency for isobutane formation (filled circles) and n-butane formation (open circles) vs. oxygen coverage.

Stable even in water. It was early recognised that the hydrolysis of one Sn-O-Si bond to form the so-called open (SiO)3Sn-OH site with a neighboring (SiO)3Si-OH, as shown in Figure 21.2, is a prerequisite to observe catalytic activity as long as the reactants are not too bullg/. Today, up to 10 wt% tin can be incorporated into the framework. However, high turnover frequencies are better achieved at low loadings (<2 wt%) to prevent the formation of inactive tin(iv) oxide in extra-framework locations. ... 

It should be noted that value Vg strongly depends on the experimental techniques used in measurement. The time-consuming, error-causing ways should be avoided (such as the surface titration method), and instead a much simpler way i.e. pulse technology could be used. When the measurement of chemisorption is carried out by the pulse technology at room temperature, the nature of the support does not relate to the fraction of the metal. Because it provides a more precise measurement for turnover frequency, this approach has opened up a new prospect for fundamental research. 

The Pt catalyst film with a surface area corresponding to N= 4.2T0" g-atom Pt, as measured by surface titration techniques, is deposited on YSZ and is exposed to P02 = 4.6 kPa, Pc2H4 = 0-36 kPa in the CSTR-type flow reactor depicted schematically in Figure 13.10a. Initially (t < 0), the circuit is open (I = 0) and the open-circuit catalytic rate r is 1.5 TO g-atom O/s. The corresponding turnover frequency (TOF), i.e., the number of oxygen atoms reacting per site per second, is 3.57 s. ... 

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