Alumina pillared montmorillonite:characterization and catalysis of toluene benzylation and aniline ethylation

摘要

Na montemorillonite (Wyoming,Source Clays, SWy-2) is modified by Ce exchange and by alumina pillaring. The interlamellar distance d(001) of the pillared samples is measured by XRD. Surface aream, total pore volume, external surface area (A_(ext)) and micropore (V_(mi))of the samples are calculated from N_2 adsorption-desorption isotherms.Acidity of the samples is measured from the step wise temperature-programmed desorption(STPD) of ammonia. Samples are evaluated for aniline ethylation and toluene benzylation reactions. Almost equal BET and external surface area(A_(ext))in Ce exchanged montmorillonite (Ce-Mont)suggest mesoporosity in the sample. Alumina pillared montmorillonite (AIPC(2)) and alumina pillared Ce exchanged montmorillonite (AIPC(Ce,2))have almost the same micropore width and volume, suggesting the presence of micropores of similar size and number. The higher external surface area (A_(ext))of AIPC(Ce,2) indicates comparatively more mesoporosity in the sample than in AIPC(2). The pillared samples are found to be thermally stable up to 873 K.Pillaring increased strong acidity, indicated by desorption of ammonia in the temperature region 573-723 K.Ce-Mont and AIPC(Ce,2)gave 100% conversin of benzyl alcohol. Over the same set of catalysts, aniline conversion is observed to be 55% and 81%, respectively.Low aniline and benzyl alcohol conversions (55%and51%)are observed over AIPC(2),probably due to restricted diffusion of the reactants and products through the micropores.