Characteristic Reactions and the Detection of Adsorbed Species by a Radiotracer Method

2 Characteristic Reactions and the Detection of Adsorbed Species by a Radiotracer Method 

Anhydrous HCl can be used as a probe either by direct exposure to a surface or it may be generated in situ by a dehydrochlorination reaction (XIII). 

Dehydrochlorination of hydrochlorocarbons in the vapour phase occurs under homogeneous flow conditions at moderate temperatures. Reaction occurs either via a 

In striking contrast to the dehydrochlorination of hydrochlorocarbons at oxides, observed above room temperature, is the room temperature dehydrochlorination of CH3CCI3 in the presence of resubUmed solid aluminium trichloride, 7-alumina that has been chlorinated using CCLi in order to enhance surface Lewis acidity or 7-alumina previously fluorinated at room temperature using sulfur tetrafluoride.  

Dehydrochlorination is accompanied by the formation on the surface of unsaturated oligomers derived from CH2=CCl2. These are dark red or purple, therefore even a trace reaction can be easily detected. The process is inhibited by traces of water. It should be noted however that not all Lewis acid fluorides give rise to this phenomenon. The behaviour of mixed metal fluorides, Lewis acid composites formed from a-Crp3,3H20 and Fep3, resembles that of 7-alumina rather than the fluorinated 7-alumina described above. ° 

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