Dehydrogenation liquid media

The metal ion is a typical catalyst for a reaction of Class B, but because H+ and OH- ions are formed in the process, the reaction may be expected to be pH dependent as well. The catalyst does not necessarily have to be a metal ion. Every substrate that can change oxidation state at the right potential and is capable of reacting with the hydrogen peroxide molecule in its two valency states can be considered a catalyst for this reaction. This means that the best parameter to correlate this reaction with would be the redox potential of the catalyst, which unfortunately is very difficult to measure on a solid material. The best thing to do is to use a catalyst which can be dissolved in a liquid medium of some kind, and to study the redox properties in the dissolved state. Measurements of this kind will be discussed in the section on oxidation and dehydrogenation. 

All samples show a low m-cresol conversion, mainly because of the reaction conditions (low temperature and poor solubility of the methanol in the liquid phase). The conversion is particularly low for both samples with a low surface area and samples havii a low number of medium basic sites. In the latter case catalyst deactivation occurs because formaldehyde (precursor of heavy compounds) is formed by methanol dehydrogenation on strong basic sites the latter then soon deactivate. The most active catalyst is the Mg/Al/O 2/1 sample, characterized by the highest number of medium-strength sites. 

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