Apparent activation energies for

Applying the Arrhenius equation to Eq. (6.116) shows that the apparent activation energy for the overall rate of polymerization is given by... 

Based on an analysis of the initial dissolution rate in different solutions at different temperatures, several very useful conclusions and recommendations were made. It was found that the apparent activation energies for the dissolution of niobium and tantalum in 10 mol/1 HF solution are 56.5 and 65.5 kJ/mol, respectively for columbite, and 42.7 and 61.1, respectively, in the case of tantalite. It was also concluded that the mechanism of dissolution is the same for both columbite and tantalite. In addition, the initial dissolution rate of niobiuth (RNb) from columbite is controlled primarily by the activities of the... 

Since the interaction of linear hydrocarbons is dominated by the van der Waals interaction with the zeohte, the apparent activation energies for cracking decrease hnearly with chain length. In some cases, differences in the overall rate are not dominated by differences in the heat of adsorption but instead are dominated by differences in the enthrones of adsorbed molecules. 

Table 1 shows a summary of the apparent activation energies for various catalytic conditions. The apparent activation energy of HDPE mixed with pure MCM-41 is significantly lower than that of HDPE only, indicating that pure MCM-41 is likely to demonstrate catalytic activity. As the A1 content increased, the apparent activation energy significantly decreased. Al-MCM-41-P demonstrated activation energies lower than those demonstrated by Al-MCM-41 -D at the same Si/Al. 

The apparent activation energy for the overall reaction Eq. (105)/(106) can be readily derived from Eq. (Ill) activation energies in general are discussed below. 

Normally the activation energy for diffusion in the gas phase is much smaller than the activation energy for a catalyzed reaction, and hence, according to Eqs. (38) and (46), the overall or apparent activation energy for the diffusion-limited process is half of what it would be without transportation limitation. If we plot the rate as a function of reciprocal temperature one observes a change in slope when transport limitations starts to set in. 

Determine an expression for the reaction order in CO, O2, and CO2, as well as the apparent activation energy for this process. 

Determine the apparent activation energy for the sticking. In the experiment the dosage of 0.2 bar s took 152 s. Determine which pressure of methane (in torr) was used in these experiments. 

Figure 5 presents data for the non-lnteractlng Rh/S102 catalyst at similar pressures and at 48, 158, and 333 °C. Even with the scatter In the 333°C data, there Is an obvious transition In the spectra as the temperature Is Increased. The predominant peak around 10 rad/sec diminishes and the one around. 5 rad/sec Increases to dominate the spectrum, a trend similar to that observed In the Rh/T102 spectra. Presumably, these trends are the result of differences In apparent activation energies for H2 adsorption and desorption on the various types of sites. 

The activation energy for the spontaneous decomposition of benzoyl peroxide is 30 ( 1) kcal. per mole, and the same value applies also within experimental error to the azo nitrile.The apparent activation energy for the polymerization of styrene initiated by either is about 23 kcal. per mole, therefore. 

Apparent activation energies for the catalytic reactions were as expected about 80 kJ/mol for the formation of formaldehyde and 60 kJ/mol for the formation of acetaldehyde from the respective alcohols (Figure 3). The turnover rates of the samples were calculated either on the basis of the number of vanadiums (all of which could be assumed to be accessible) or by assuming that oxygen uptake counted the catalytic sites ... 

Figure 5 NO+propene. Dependence of apparent activation energy for CO, ...

Addition of CO also enhances the N2O conversion, by about a factor of two for Co and tremendously for Fe (figure 6). For Cu a maximum in the N2O conversion appears as a function of the CO/N2O ratio in the feed. This maximum shifts to higher values with increasing temperature (figure 7). The apparent activation energy for Co is hardly altered, for Fe it decreased nearly 1(X) kJ/mol, while for Cu it is increased by 50 kJ/mol. 

Table 4. Ag/Pt molar ratio and its influence on ethylene hydrogenation rates and apparent activation energy for nanoparticle encapsulated shape-controlled Pt nanoparticles [17].

Pt20/SiO2 and PtCl/Si02 catalysts, consistent with the structure insensitivity of this reaction (15). Apparent activation energies for this reaction (Figure 6) were also the same for both catalysts. 

The apparent activation energy for the thermal decomposition of phenyl benzyl ether was calculated to be 50 kcal/mole, since the first order rate constants were 1.39x10 at 320°C, 5.19xl0"4 at 340°C and 9.52x10" S at 350°C, respectively. 

Table 2 Apparent activation energies for each stage of the induction period of glass crystallization just above Tg for PET, PEN, sPS, and iPS [15]... 

Gold forms a continuous series of solid solutions with palladium, and there is no evidence for the existence of a miscibility gap. Also, the catalytic properties of the component metals are very different, and for these reasons the Pd-Au alloys have been popular in studies of the electronic factor in catalysis. The well-known paper by Couper and Eley (127) remains the most clearly defined example of a correlation between catalytic activity and the filling of d-band vacancies. The apparent activation energy for the ortho-parahydrogen conversion over Pd-Au wires wras constant on Pd and the Pd-rich alloys, but increased abruptly at 60% Au, at which composition d-band vacancies were considered to be just filled. Subsequently, Eley, with various collaborators, has studied a number of other reactions over the same alloy wires, e.g., formic acid decomposition 128), CO oxidation 129), and N20 decomposition ISO). These results, and the extent to which they support the d-band theory, have been reviewed by Eley (1). We shall confine our attention here to the chemisorption of oxygen and the decomposition of formic acid, winch have been studied on Pd-Au alloy films. 

Analysis of the kinetic parameters showed that the apparent activation energy for the reaction was reduced from 105 to 57 kj mol-1 (Tab. 3.2). This observation is consistent with the polar mechanism of this reaction implying the development of a dipole in the transition state (Fig. 3.8) even when the reaction was performed in a polar solvent. 

The overall stoichiometric equation for this decomposition leading to equilibrium depends on the temperature. A considerable amount of the final products are H, OH, and O. Bauer et al.3 were the first to report an investigation of the water dissociation by the shock-tube method. The temperature range for this study was 2400-3200 °K. They followed the reaction by measuring the uv absorption of the hydroxyl radical produced during the decomposition. The apparent activation energy for the parameter (1/ [H20])(d [OH]/df) of about 50 kcal.mole-1 seemed to indicate that the reaction... 

CO oxidation catalysis showed that, for all the supports, the bimetallic catalyst was more active at low temperatures than the corresponing monometallic and cometallic catalysts. Apparent activation energies for monometallic Pt and Au catalysts were very consistent, near 32 and 80 kJ/mole, respectively. The s)uiergism for PtieAuie catalysts also shows up in the apparent activation energies for these catalysts, which were consistently around 23 kJ/mole. 

Balandin and co-workers 143) have shown that the apparent activation energies for the dehydrogenation of ethylbenzenes to styrenes, as well as their similar previous data 144), can be correlated by the Hammett equation (series 116 and 117, three reactants in each, probably an Fe203 catalyst, negative slopes). 

The apparent activation energy for the absorption/desorption process is usually evaluated from the Arrhenius plot of rate constant k values with temperature [166] by simply plotting a straight line InA vs. IRT. 

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