Reaction with ozone temperature, table

Fig. 3. compares the ammonia conversion for nanostructured vanadia/TiOa catalysts pretreated with O2 and 100 ppm O3/O2 gases. The reactions were conducted at 348 K for 3 h. No N2O and NO byproducts were detected in the reactor outlet. It is clear from the figure that higher vanadium content is beneficial to the reaction and ozone pretreatment yields a more active catalyst. Unlike the current catalysts, which require a reaction temperature of at least 473 K, the new catalyst is able to perform at much lower temperature. Also, unlike these catalysts, complete conversion to nitrogen was achieved with the new catalysts. Table 2 shows that the reaction rate of the new catalysts compared favorably with the established catalysts. 

Table I. Second-Order Rate Constants (K) for the Reactions of Ozone with Olefins in CCI4 Solutions at Room Temperature (6)...

Room temperature rate constants and Arrhenius parameters for the gas-phase reactions of ozone with cw-2-butene, 2-methyl-2-butene and a number of cycloalkenes are shown in Table 1 together with the literature values. The rate coefficients for cw-2-butene and 2-methyl-2-butene are in excellent agreement with the data evaluation of Atkinson and Carter [3]. The reported room temperature rate constants for the reaction of ozone with cyclopentene and cyclohexene show a considerable degree of scatter. The present results for cyclopentene provide support for the recent determinations by Bennett et al [24], Nolting et al [25], and Green and Atkinson [21], while the value for cycloheptene is slightly lower than the reported values [20] and [25]. No previous kinetic studies have been carried out on the reactions of O3 with cw-cyclooctene and cw-cyclodecene. 

The table below presents measured rate constants for the reaction of NO with ozone at three temperatures. From these data, determine the activation energy of the reaction in kj/mol. 

TABLE 3 of alcohols Dependence of k on the temperature in °C for ozone reaction with three types ... 

The pentenamides were then treated with ozone. Changes in solvent and temperature (-78° to room temperature) did not alter significantly the course or yield of this reaction. The ozonolysis of the olefin gave an intermediate aldehyde which could not be isolated but cyclized immediately to the desired hydroxypyrrolidi-none, 2. This general procedure was applicable to a large number of heterocyclic amines (Table II). In all cases, good overall yields were obtained. 

TABLE 1.2 The Temperature Dependence of the Rate Constant k of the Ozone in the Reaction with PVA... 

The room temperature rate constants for the reactions of 03 with some alkenes are given in Table 6.9. While the values are many orders of magnitude smaller than those for the corresponding OH reactions, the fact that tropospheric ozone concentrations are so much larger makes these reactions a significant removal process for the alkenes. 

A more comprehensive analysis of the influences on the ozone solubility was made by Sotelo et al., (1989). The Henry s Law constant H was measured in the presence of several salts, i. e. buffer solutions frequently used in ozonation experiments. Based on an ozone mass balance in a stirred tank reactor and employing the two film theory of gas absorption followed by an irreversible chemical reaction (Charpentier, 1981), equations for the Henry s Law constant as a function of temperature, pH and ionic strength, which agreed with the experimental values within 15 % were developed (Table 3-2). In this study, much care was taken to correctly analyse the ozone decomposition due to changes in the pH as well as to achieve the steady state experimental concentration at every temperature in the range considered (0°C [Pg.86]

We have recently and critically evaluated the available high temperature experimental data for the ozone decomposition reaction (8). The expression used here and shown in Table I is consistent with all the direct experimental data known to us and is valid over a decade range in temperature. 

Further characterization of the ozone—mesitylphenylethylene complex produced at —150 °C was done by NMR and visible spectral studies. The low temperature NMR spectra of the starting olefin, the red complex (ozonized olefin at —150°C) and the dilute reaction mixture at —135°C containing the epoxide of 1-mesityl-1-phenylethylene are described in Table III. The —150 °C solutions of the olefin and the complex contain the same bands, the only difference being that the peaks were shifted slightly upfield in the formation of the complex. Such is typical of tt complexes with very little charge transfer, such as iodine and tetracyano-ethylene complexes of various aromatic molecules (5, 6). When the temperature of the ozonized reaction mixture was allowed to rise above about —145 °C, the NMR spectrum changed, giving rise to the characteristic peaks of the epoxide of 1-mesityl-l-phenylethylene. 

Table II presents a summary of the values of kreY which were obtained in the way just indicated, for p-methylstyrene, in CC14 solution, with respect to styrene. These results indicate that kTei is invariant with respect to the ozone flow rate, the temperature of ozonolysis, and the olefin initial concentration. The fact that kreA is independent of temperature in this case is readily understood when it is considered that the experimental activation energies for the ozone-olefin reaction are likely to be very similar for p-methylstyrene and styrene.

Several investigations of the reactions of atomic oxygen with COS, 082,349—351 and CSeg have been effected. The reactions of 0( D), produced by u.v. photolysis of ozone, have been studied in ddute mixtures of O3 and CS2 or COS in Xe or Ar matrices at temperatures between 15 and 60 K. I.r. spectrophotometry was used to identify the products. (Table 18). No... 

The distribution of atmospheric ozone based on data obtained by the Nimbus 4 BUV satellite is shown in Fig. 2. Ozone is most abundant in the tropical middle stratosphere ( 30 km), where the solar zenith angle is small and the atmospheric density is sufficiently large to produce O3 efficiently via reactions (1) and (2). The decrease in ozone toward the poles is due to a decrease in production due to the steeper solar zenith angles at high latitudes. The important solar absorption bands for ozone and oxygen are listed in Table I. Figure 3 shows the altitudes where the stratosphere and mesosphere are heated by these absorption bands. The peak in the heating is nearly coincident with the stratopause temperature maximum shown in Fig. 1. 

Table 9 lists reactions/processes featured in CFB reactor studies or in the development of reactor models, together with relevant references. The ozone decomposition reaction is of no commercial interest, but it is convenient for tests since it is essentially first order, irreversible, and able to proceed at room temperature, and since the concentration of ozone can be readily analyzed at low partial pressures. The other reactions are all of commercial interest. 

Table VIII-L-2 gives the upper limit to the rate coefficient of the reaction of O3 with nitrobenzene determined by Atkinson et al. (1987c). The measurement was conducted at ambient temperature and atmospheric pressure by monitoring the decrease of ozone in the presence of known concentrations of nitrobenzene and is the only reported investigation.

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