Blown Activation Energy

Due to their highly polar nature, barbiturates require derivatization prior to analysis by GC-MS. In such cases, the sample is dissolved in methanol, centrifnged, the supernatant recovered and placed in a derivatizing vial and is then blown down under nitrogen. The derivatization procednre, using 0.2 M trimethylanilin-ium hydroxide in methanol, is, in principle, the same as that used for other pre-column derivatizations. However, with this system the reaction does not occnr immediately because insufficient activation energy is available at ambient temperature for this to take place. Direct transfer of the reaction mixture onto the heated injection block of the gas chromatograph overcomes this problem and the derivatization reaction can then proceed. Snch a reaction, an example of flash alkylation is illustrated in Scheme 9.1. 

Gardner et al. reported that H2S catalytic partial oxidation technology with an AC catalyst is a promising method for the removal of H2S from fuel cell hydrocarbon feedstocks.206 Three different fuel cell feedstocks were considered for analysis sour natural gas, sour effluent from a liquid middle distillate fuel processor, and a Texaco 02-blown coal-derived synthesis gas. Their experimental results indicate that H2S concentration can be removed down to the part per million level in these plants. Additionally, a power-law rate expression was developed and reaction kinetics compared with prior literature. The activation energy for this reaction was determined to be 34.4 kJ/g mol with the reaction being first order in H2S and 0.3 order in 02. 

Even the corresponding peak temperatures of the blown bitumens show very small variances in the tests in 10 bar methane and also permit the calculation of statistical means. The resulting coefficients of variation are 3.0 % maximum. This is also true for the colloid components, except for the dispersion medium of the two bitumens 85/40 (sample III) and 85/25 (sample IV). Here again a weight loss caused by distillation even occurs under pressure with the consequence of low values for the activation energy and frequency factor. Only the data of the other three samples was included in the statistics. The average values of the Arrhenius coefficients calculated in this manner and the means of the conversion aie shown in Table 4-93. 

In the plot of half life time, versus temperature, the differences of the activation energies for the blown Bitumens and their colloid components cause a clear divergence of the straight lines from the parallel (Fig. 4-76). 

The peak maximum temperatures of the blown bitumens are not so uniform and therefore the calculation of means is not worth while. Some of the blown bitumens, their dispersion medium and their petroleum resins demonstrate peak maxima both in the distillation and in the pyrolysis range because of the content of low boiling flux oils. The activation energies computed for the distillation range are equal to the enthalpies of vaporization, as shown by experiments on model substances. 

Thermogravimetry in air and the DSC oxidation experiments confirm the inferior oxidation, stability of blown bitumens. DSC peak maximum temperatures, the activation energy of the first oxidation peak, and the temperatures of corresponding DTG maxima for blown bitumens are inferior compared to distillation bimmens. 

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