Fabrication of ordered mesoporous solid super base with high thermal stability from mesoporous carbons

Abstract

Mesoporous solid super bases with high thermal stabilities are highly attractive for use as green catalysts in various reactions. The decomposition of alkali-metal nitrates on mesoporous supports is a facile approach to the preparation of mesoporous super bases. However, the decomposition of nitrates needs a high temperature and the generated basic oxides destroy the mesoporous support structures because of the low electronegativities of the alkali metals. In the present study, highly ordered mesoporous solid super bases were prepared using ordered mesoporous carbons (OMCs) as supports. The dispersion and decomposition of the base precursor (KNO3) on the OMCs were studied using in-situ X-ray diffraction. The results show that the KNO3 decomposed into potassium oxides at low temperature and then these potassium oxides reacted with carbon at high temperature to form strong bases. The OMCs provided supports with highly ordered meso-structures and promoted KNO3 transformation to strongly basic sites. Transmission electron microscopy and N2 adsorption-desorption isotherm studies showed that the meso-structure was well preserved even after calcination at 800 °C. The obtained materials were strong bases and had high catalytic activities in dimethyl carbonate synthesis by transesterification. A dimethyl carbonate yield of 72% was achieved.