Arrhenius frequency factor

Nitrocellulose is among the least stable of common explosives. At 125°C it decomposes autocatalyticaHy to CO, CO2, H2O, N2, and NO, primarily as a result of hydrolysis of the ester and intermolecular oxidation of the anhydroglucose rings. At 50°C the rate of decomposition of purified nitrocellulose is about 4.5 x 10 %/h, increasing by a factor of about 3.5 for each 10°C rise in temperature. Many values have been reported for the activation energy, E, and Arrhenius frequency factor, Z, of nitrocellulose. Typical values foiE and Z are 205 kj/mol (49 kcal/mol) and 10.21, respectively. The addition of... 

The Arrhenius frequency factor,47 9 A, is in units of liter mole sec. e Water was added to absolute ethanol to make 99.8% ethanol. f Values of JH were also given. 

The Arrhenius frequency factor,470 A, is in units of liter mole i sec i. 

It is a common assumption that the influence of steric factors will be manifested mainly as a higher activation energy. In fact, there is good evidence37 to show that steric factors are mainly reflected in a less favorable entropy of activation or Arrhenius frequency factor. This is due to the degrees of freedom... 

The Arrhenius frequency factors [log(T/M V)] for addition of carbon centered radicals to the unsubstiUited terminus of monosubslituted or 1,1-disubstituted olefins cover a limited range (6.0-9.0), depend primarily on the steric demand of the attacking radical and are generally unaffected by remote alkene substituents. Typical values of log(T/M" V) are ca 6.5 for tertiary polymeric (e.g. PMMA ), ca 7.0 for secondary polymeric (PS, PMA, and ca 7.5, 8.0 and 8.5 for small tertiary (e.g. /-C4H9 ), secondary (i-CiH ) and primary (CHj, CbHs ) radicals respectively (Section 4.5.4).4 For 1,2,2-trisubstituted alkenes the frequency factors arc about an order of magnitude lower.4 The trend in values is consistent with expectation based on Iheoretical calculations. 

A > A 2 Arrhenius frequency factors for desorption kmol/m2s NIA2 T 1... 

The results from the Arrhenius analyses indicate that the CO2/CH3OH system has a higher activation barrier (74.2 7.7 kJ/mol) for the solvation process compared to C02/CH3CN (43.3 18 kJ/mol). However, C02/CH30H has a faster solvation rate. The reason for this fast solvation rate lies in the collisional or Arrhenius frequency factor. The collisional frequency factor for C02/CH30H and C02/CH3CN are (1.6 0.3) x 1014 10 M1 s1 and (4.2 0.8) x 108 M1 s1, respectively. 

After E is calculated from Equation 1 or 2, an Arrhenius frequency factor (6) can be calculated from the same thermal data. 

Another possible correlation between coal structure and pyrolysis behavior is indicated by the temperature dependence of the evolution of pyrolytic water being strikingly different for the two coals. Figure 5 shows pyrolytic water evolution data for experiments in which the sample was heated at 1000°C/sec to the peak temperature indicated on the abscissa and then immediately allowed to cool at around 200°C/sec. The smooth curves are based on a single reaction, first-order decomposition model (7,8) and on the stated temperature-time history. Parameters used for the lignite have been published (8) while for the bituminous coal the Arrhenius frequency factor and activation energy were taken as 1013 sec"1 and 35 kcal/mol, respectively, with the yield of pyrolytic water ultimately attainable estimated from experimental measurements as 4.6 wt % of the coal (as-received). 

A DuPont Model 990 Thermal Analysis Console with Model 910 DSC accessory was interfaced to a minicomputer system by means of a microcomputer for automated data collection. A program to provide the analysis of reaction kinetics data by the single dynamic scan method for DSC kinetics was developed. Features of this program include a fit of the data to a single equation by multiple regression techniques to yield the reaction order, the energy of activation and the Arrhenius frequency factor. The rate constant k(T) is then calculated and conversion data as a function of time and temperature can be generated at the operator s option. 

E+16 0.355922E+02 0.9999 ORDER OF REACTION HEAT OF REACTION, CAL/G ENERGY OF ACTIVATION, KCAL/MOLE ARRHENIUS FREQUENCY FACTOR Ln < A) CORRELATION... 

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