Following the adventitious discovery, made some years ago, that γ-alumina, fluorinated with SF4 under static conditions and nominally at room temperature, promoted the room temperature dehydrochlorination of CH3CCl3, the subsequent oligomerisation of CH2=CCl2 and partial dehydrochlorination of the oligomeric product, we have been studying interactions of anhydrous HCl with transitional aluminas and their fluorinated or chlorinated analogues. These materials could be relevant as models for Lewis acid, heterogeneous catalysts and in a few instances are real catalysts. Here, the behaviour of anhydrous HCl, either generated in situ by dehydrochlorination of tert-butyl chloride or used directly, towards aluminium chloride fluoride (ACF) and nanoscopic, HS-AlF3 is compared. Comparisons are made also with the conventionally-synthesised, reference materials, β-AlF3 and fluorinated γ-aluminas. At these latter surfaces, the dehydrochlorination reactions are relatively slow at ambient temperature. Rapid dehydrochlorination of ButCl is observed on both ACF and HS-AlF3 at room temperature; weakly and strongly bound HCl are formed and interactions with bulk materials are observed. These findings originate from FTIR spectroscopic experiments and from labelling experiments using the isotope, chlorine-36. Proposals are made to account for the observation of multiple types of adsorbed HCl. Analogies are drawn with the multiple adsorption sites observed when η-alumina is chlorinated using HCl; this surface is a good catalyst for methanol chlorination.

Using anhydrous hydrogen chloride as a probe molecule for aluminum fluoride Lewis acids

255th National Meeting (2018)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.