Mesoporous solids for low temperature CO2 adsorption

Carbon dioxide concentrations in the atmosphere have risen since the onset of the Industrial Revolution. It is a potent green house gas contributing to climate change. One of the biggest carbon dioxide emitters are large stationary sources such as power plants. A conventional technology to capture this gas from power plants is to use amines such as monoethanolamine in aqueous solutions. However this technology suffers from several disadvantages such as very high energy requirements, toxicity and corrosion problems thus reducing the power plants efficiency by up to 40%. Mesoporous silicates have received a large amount of attention by researchers and chemical engineers since their discovery by Exxon Mobil researchers in 1992. The fact that they can be functionalised with a variety of reagents including organic functional groups and metals make them an interesting material to be applied in a wide range of technologies. Funtionalising amines onto the mesoporous silica SBA-15 and testing the resulting solid for its carbon dioxide adsorption and desorption characteristics was the content of this study. The aim was to investigate the adsorption capacity, the temperature required for CO2 release, the stability and regenerability of the prepared solids. SBA15 was synthesised and six different types of amines (aminopropyltriethoxysilane (APTES), tetraethylenepentamine (TEPA), polyethylenimine (PEI), N1-(3-trimethoxysilylprpyl)deithylenetriamine (TRI), hexamethylenetetramine (HEXA) and polyvinyl pyridine (PVP) were) funtionalised onto its’ surface. The solids prepared were characterised by nitrogen adsorption/desorption, thermogravimetric analysis (TGA), Fourier infrared spectroscopy (FTIR) and transmission electron microscopy (TEM) for structural examination. The solids were also tested in a temperature controlled reactor connected to a mass spectrometer for adsorption/desorption studies. SBA-15 had a surface area of 1800 m2 g-1 with a pore diameter of 6.8 nm. Upon functionalisation, the surface area and pore diameter were reduced. TEPA-functionalised solids exhibited the best adsorption