Preparation, Characterization And Catalytic Performance Of Porous Carbon Solid Superbase

In recent years,solid super bases have got extensive attention as alternatives to homogeneous ones in various fields to meet the need for sustainable development and green chemistry.Solid strong bases are good candidates for heterogeneous catalysts in environmentally friendly catalytic processes.Solid bases catalyze various organic reactions,transesterifications,alkylation reaction,Michael additions e.g..Solid super bases are also application related to energy and the environment.So,solid super bases are receiving increasing attention in the field of catalysis.The first part of this paper described the preparation of mesoporous carbon solid super bases by wet impregnation method.The decomposition of alkali-metal nitrates on mesoporous supports was a facile approach to the preparation of mesoporous super bases.However,the decomposition of nitrates needs a high temperature and the generated basic oxides would destroy the mesoporous support structure because of the low electro negativities of the alkali metals.In the present study,highly ordered mesoporous solid super bases were prepared by using ordered mesoporous carbons(OMCs)as supports.The dispersion and decomposition of the base precursor(KNO3)on the OMCs were studied using X-ray diffraction(XRD),Fourier Transform Infrared(FTIR),X-ray photoelectron spectroscopy(XPS),Transmission electron microscope(TEM)and so on.The results show that the KNO3 decomposed into potassium oxides at low temperature and then these potassium o xides 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.TEM and N2 adsorption-desorption isotherm studies showed that the meso-structure was well preserved even after calcination at 800 oC.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.In the second part,a series of base-acid catalysts are prepared by loading KNO3 on granular coconut-shell activated carbons(GCSACs).The solid based were obtained after calcination at different temperatures.The structure and base-acid capabilities of the obtained catalysts were characterized by various approaches.The decomposition of KNO 3 played an important role in the formation of strength base and acid sites.The dispersion and decomposition of the base precursor(KNO3)on the GCSACs were studied by using X-ray diffraction(XRD),Fourier Transform Infrared(FTIR).The obtained materials exhibit excellent properties for the ethanol condensation to butanol.The moderate base-acid sites are more beneficial to the ethanol aldol coupling reaction.The optimal catalyst,prepared with 10 wt % KNO3 loading after calcination at 800 oC,exhibited high ethanol conversion(45.3 %)and butanol selectivity(27.6 %).The current work may provide a new idea to design and synthesis base-acid catalysts for ethanol condensation reaction.The last chapter introduced the preparation of N-doped mesoporous carbons and its catalysis application.By using the resorcinol as the carbon source,F127 as the soft template,melamine as the nitrogen source,the N-doped mesoporous carbons were synthesized by the hydrothermal synthesis.TEM and N2 adsorption-desorption isotherm studies showed that the meso-structure was well preserved after modification by potassium oxides.X-ray photoelectron spectroscopy(XPS)was used to detect the content of the nitrogen at around 2 %.The XRD and IR results show that the KNO3 decomposed into potassium oxides at low temperature.The obtained materials were strong bases and had high catalytic activities in dimethyl carbonate synthesis by transesterification.A dimethyl carbonate yield of 30.2 % was achieved.