Progressive conversion reaction mode

The dimerization of 28 has also been studied by Prasad, who used Raman spectroscopy to monitor both changes in intermolecular vibrations and lattice phonon modes [73]. The Raman spectrum shows the disappearance of alkene stretches at 997, 1180, 1593, and 1625 cm-1 as expected, and the appearance of cyclobutane modes at 878,979, and 1001 cm-1. Phonon modes broadened as the reaction progressed, and bands around 15-40 cm-1 showed a shift in frequency. Between about 50 and 66% conversion it was difficult to define distinct bands, but after that point product bands grew in distinctly. This amalgamation behavior is good evidence for a homogeneous reaction mechanism. 

At the end of each of the two sets of pulse-mode reaction runs, the catalyst was subjected to a progressive heating (10°C/min) up to 550°C. Both catalyst samples released H2O, VP and HEP in the order, but the C02-poisoned sample in much lower amount. To confirm these findings some additional experiments by CSTR under standard conditions were carried out after treating two samples of activated Y84 catalyst with pure CO2, either at room temperature or at 160°C. After four hours of reaction the conversion of HEP dropped by 8.4 and 25.9% with respect to the unpoisoned catalyst, for the two samples, respectively. It is then evident that the activity of the catalyst is greatly reduced when its basic sites are poisoned by CO2. 

In mode 1, as the first increment of A is added, it is converted rapidly to V by reaction with the B molecules. The V molecules then find themselves in the presence of excess B molecules and thus react further to yield W. The same process occurs as subsequent increments of A are supplied, the conversion rate being limited by the rate of addition of A. This mode of mixing leads to a situation in which one does not ever have significant amounts of V present in the vessel to which A is added. A is also absent from this vessel as long as any B remains, but it will be present after complete con-snmption of B. The vessel becomes progressively richer in W nntil all B is consumed. Figure 9.8 is a schematic representation of the various mole numbers present in the mixing beaker. 

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