Templated polymeric materials as adsorbents for the postcombustion capture of CO2

Amine solvents have long been used by industry as absorbents for acid gas (CO2, H2S) removal and are the current technology of choice for post-combustion carbon capture from fossil fuel power plants. However, these technologies are energy intensive and have a number of short comings. In an effort to reduce the capital cost and energy penalty of carbon capture alternative technologies are being explored, of which solid sorbents have shown good potential. Adsorbents containing basic nitrogen functional groups to increase adsorbent / adsorbate interaction have been demonstrated to be effective for post-combustion capture. These materials are usually synthesised by the impregnation of basic amine polymers or bonding of amine groups to the surface of inorganic porous substrates. In this work the development of a range of novel high nitrogen content activated carbon adsorbents will be described. The aim of this research is to introduce basic nitrogen directly into the matrix of activated carbon to yield high capacity adsorbents with high thermal stability in terms of volatile and thermal loss of nitrogen. Novel nitrogen enriched activated carbons have been synthesised by a templating or nanocasting technique by which a removable inorganic template is used to generate porous polymers with high surface area. A range of adsorbents have been synthesised by templating of melamine–formaldehyde resin with silica followed by activation over a range of temperatures from 400–700 ?C. The resultant adsorbents have been characterised in terms of their textural properties, elemental composition and surface chemistry, with materials containing up to 42 wt.% nitrogen and 880 m2 g?1 surface area generated. Adsorption capacities up to 2.25 mmol g?1 of CO2 at 25 ?C were measured using thermogravimetric analysis and will be discussed in terms of the textural and surface chemical properties of the carbons as determined by X-ray Photoelectron Spectroscopy (XPS). Both texture and surface chemistry influence the CO2 capture performance of the adsorbents. The activation temperature used during the synthesis step controls the nitrogen functional groups present, as determined by XPS, with the loss of triazine nitrogen with increasing activation temperature proposed to account for the decreased CO2 affinity. Finally the stability and regeneration of the carbons over numerous thermal swing adsorption cycles will be described.