Activation energy determination different measurement techniques

The catalytic work on the zeolites has been carried out using the pulse microreactor technique (4) on the following reactions cracking of cumene, isomerization of 1-butene to 2-butene, polymerization of ethylene, equilibration of hydrogen-deuterium gas, and the ortho-para hydrogen conversion. These reactions were studied as a function of replacement of sodium by ammonium ion and subsequent heat treatment of the material (3). Furthermore, in some cases a surface titration of the catalytic sites was used to determine not only the number of sites but also the activity per site. Measurements at different temperatures permitted the determination of the absolute rate at each temperature with subsequent calculation of the activation energy and the entropy factor. For cumene cracking, the number of active sites was found to be equal to the number of sodium ions replaced in the catalyst synthesis by ammonium ions up to about 50% replacement. This proved that the active sites were either Bronsted or Lewis acid sites or both. Physical defects such as strains in the crystals were thus eliminated and the... 

Many reports have been made of the activation energy of polystyrene degradation from measurements of a variety of properties and using different techniques of analysis of the kinetics. The closest to that determined by factor-jump thermogravimetry is... 

The Arrhenius parameters determined by Wise et al. [31] have been reproduced by Hofer et al. [39] and Flowers et al. [40] using different techniques (a detailed description of this work is given below). All three groups find activation energies of 57-58 kcal/mol. This raises the issue of why Sinniah et al. [33] found a much lower value. Differences in surface preparation or impurities must be considered, but there is no evidence that the surface of Sinniah et al. was of substantially better or worse quality than the others. An error in temperature measurement, caused for example by... 

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