Preparation of siliceous cellular foams and polyamine-impregnated CO2 adsorbents

“Porous siliceous cellular foams (SCFs) with variable pore and window sizes were synthesised using a modified version of the micro-emulsion method reported earlier by Schmidt-Winkel and co-workers,41 with the amphipathic surfactant P123 as the template and TMB as the pore-expanding agent. Briefly, in a typical preparation with TEOS as the silicon source and a TMB/P123 mass ratio of 1 : 1, 8 g of P123 was first dissolved in 150 ml of 1.5 M HCl at 40 °C and then 8 g of TMB was added. Following 40 min of further stirring, 18.4 ml of TEOS and 10 ml of 2.5 M NH4F solution (F/Si molar ratio 0.03) were added to the mixture under vigorous stirring and the resultant solution was kept at 40 °C for variable times with continuous stirring. During this process, the hydrolysis of the TEOS at the surface of P123-coated TMB droplets leads to the formation of a composite shell material with interconnected cells and windows at the areas of contact of adjacent droplets. The formed milky reaction mixture was then transferred into an autoclave and kept at 100 or 120 °C for variable times under static conditions. The as-prepared white precipitate was separated by filtration and dried at ambient temperature. The dried precipitate was then calcined in air at 550 °C for 8 hours to obtain the porous silica support. The effect of preparation parameters on the surface textural properties of silica supports and hence the CO2 adsorptive properties of their supported polyamine sorbents was investigated, including the TMB/P123 ratio, aging time and aging temperature. For clarity and easy comparisons, the SCF materials synthesised under different conditions are denoted as SCF-x-y-z where xy and z represent the TMB/P123 ratio, aging temperature and time, respectively. Table 1 summarises the preparation parameters examined.”

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