TPD and DSC insights in the basicity of MCM-48-like silica and modified counterparts

Abstract

The basicity of MCM-48-like silica and modified counterparts was investigated by CO2 thermal programmed desorption (TPD) and differential scanning calorimetry (DSC). Post-synthesis modifications were achieved through: (i) incorporation of dihexylamine (DHA); (ii) DHA removal by ethanol; (iii) calcination at 550°C in air stream and (iv) incorporation of Boltorn H-20 dendrimer. After DHA incorporation, the specific surface area dropped from 953 down to 74m2g−1, and the pore volume decreased from 0.41 to 0.13cm3g−1. The surface basicity, expressed in terms of retained CO2 amount decreased markedly after template removal, but was slightly revived after dendrimer loading. CO2 was found to adsorb via physical or chemical interactions on two types of sites, according to the post-synthesis treatment. Correlating TPD and DSC measurements allows assessing the extent of the acidity attenuation and basicity adjustment for a wide variety of catalysts and adsorbents through suitable post-synthesis modifications.