Infra-red studies of ammoniation of pillared montmorillonites

Ammoniation of montmorillonites pillared with polyhydroxo-complexes of Al w as performed in flow conditions at 773-1073 K and monitored by IR spectrosc opy. Interaction of the clay with ammonia revealed exchange of terminal and bridging -OH groups by NH2-, NH- and N-species depending on the reaction t emperature. Amination begins at 773 K while formation of NH groups starts a t 873 K, Transformation of NH- into N-species occurs at 973 K. A mechanism for the ammoniation reaction is proposed and the series of the relative rea ctivity of OH groups was established: Si-OH > Mg-OH-Mg > Al-OH-Mg > Al-OH-A l. This series was rationalized in terms of accessibility of the OH groups.