Generating Superbasic Sites on Mesoporous Silica SBA-15

Abstract

Superbasic sites have been generated on the mesoporous silica materials for the first time, through a\nnew strategy to prepare the MgO-modified SBA-15 in one-pot synthesis and then to disperse KNO₃,\npossessing the good textural structure of the host and the high basic strength (<i>H</i>_-) of 27.0. The in situ\ncoated Mg species passivated the silanol groups on the surface of siliceous SBA-15 so that the\nmesostructure of SBA-15 could be reserved after the composite was loaded with KNO₃ and activated at\nhigh temperature. Existence of the special protection layer of MgO on the surface of SBA-15 was also\nbeneficial for decomposition of KNO₃ to form superbasic sites on the mesoporous silica. The influence\nof coating amount of MgO on the protection of the textural properties of SBA-15 is examined and discussed\nin terms of consuming surface silanol groups. Dispersion and decomposition of KNO₃ on the MgO layer\nis also explored. Other metal oxides such as CaO, ZnO, and Al₂O₃ are in situ coated on the surface of\nSBA-15 through one-pot synthesis and their function of protecting SBA-15 is evaluated for comparison\nwith MgO.