Arrhenius plots turnover frequency. 140

Fig. 16. An Arrhenius plot of the rate of methanation over sulfided (a) Ni(lOO) and (b) Ru(0001) catalysts at 120torr and a Hj/CO ratio of 4. Coverages are expressed as fractions of a monolayer. Nch, is the turnover frequency or the number of methane molecules produced per surface nickel...

Fig. 14. Arrhenius plots of CO oxidation reaction rates (turnover frequencies) on Rh showing a ramparison between two [(111) and (100)] Rh single-crystal surfaces and supported Rh catalysts. Eq = = 10 bar. The activation energy is ca. 126 kJ moE in all cases...

Using activation energies for CO dissociation and carbon hydrogenation reported in the literature (i.e., 230 and 145 kJ/mol, respectively), calculations showed that changes in heats of adsorption of the reactants H, and CO on Ni significantly alter methanation behavior. Turnover frequencies for the Ni and TiOx/Ni surfaces are plotted in an Arrhenius fashion in Figure 9 for a total pressure of 120 Torr and an H,/C0 ratio of 4. The plots show that... 

Fig. 4.14. Comparison of CO oxidation activities of palladium-on-zirconia catalysts prepared by in situ activation from amorphous Pd33Zr(>7 ( ) and by conventional impregnation of zir-conia with a palladium salt (O). Arrhenius plots of the turnover frequencies are plotted. Conditions reactant gas mixture. 1700 ppm of CO, and 1700 ppm 03 in nitrogen flow rate. 150 ml (STP) min amount of catalyst, 0.37 g O 1.24 g...

Figure 1.15 shows the influence of temperature on the catalytic activity in an Arrhenius plot of the turnover frequency (TOFs). These data can now be compared to data obtained for the reduction of 4-nitrophenol with an excess of NaBH4 in presence of the metal nano-composite particles. From Figure 1.15a nonlinear relation between In(TOF) and HT can be seen. The TOFs increase more than exponentially when increasing the temperature. Only in the immediate vicinity of the LOST is a significantly smaller TOF monitored. 

The effect of Cl on CO, methane, and ethane oxidation reactions on Pt/AljOj catalysts is shown in Figure 17.3. The plots in the left panels correspond to the conversion at different temperatures, and those in the right, to the Arrhenius plots. The turnover frequency (TOF) values used to obtain the Arrhenius plots were obtained at low conversion (<15%) to minimize the effect of reactant concentration. 

The effect of temperature and V2O5 content on the rate is shown in figure 3, an Arrhenius plot of turnover frequency N q for standard gas composition. In... 

Recently, Kim et al. carried out CO oxidation on 2 and 6.5 nm Rh nanoparticles capped by poly(vinylpyrrolidone) (PVP) before and after UV/O3 surface treatment [51]. Figure 7.3 shows the catalytic activity, Arrhenius plot, and summary of catalytic turnover rates at 443 K for the CO oxidation reaction on two-dimensional arrays of 2 and 6.5 nm Rh nanoparticles before and after UV-ozone treatment. As shown in Fig. 7.3a, the smaller Rh nanoparticles before UV-ozone treatment show a higher activity than the larger Rh nanoparticles and it is also clear that the turnover frequency (TOF) of the 2 and 6.5 nm Rh nanoparticles increased by a factor of two or three after UV-ozone treatment. The activation energies for 2 and 6.5 mn Rh nanoparticles were obtained from Arrhenius plots of catalytic activity (Fig. 7.3b). Figure 7.3c shows a summary of the catalytic turnover rates at 443 K and the activation energies measured on the Rh nanoparticles before and after UV-ozone surface treatment. The activation energy decreased from 29.4 to 27.8 kcal/mol for the 2 nm Rh nanoparticles and decreased from 31.3 to 28.5 kcal/mol for the 6.5 mn Rh nanoparticles after UV-ozone treatment, as shown in Fig. 7.3c. 

Fig. 7.3 Catalytic activity of the CO oxidation reaction on two-dimensional arrays of Rh NPs. (a) Turnover frequency (TOP) of Rh NPs with temperature, (b) Arrhenius plots of Rh NPs, and (c) summary of TOFs and activation energies of the CO oxidation reaction measured on Rh NPs before and after UV-ozone surface treatment...

Figure 14.5 shows the Arrhenius plot of the experimental results for Pt/Al203 and Pt/n02 and for a feed ratio of CO/O2 = 3.014. The TOP, turnover frequency, was obtained by normalizing the reaction rates with the total number of surface atoms, measured by CO chemisorption at room temperature after reduction at 573 K [11]. 

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