Formation of NOx during high temperature combustion in air is inevitable and of increasing environmental concern. NOx participates in detrimental photochemical reactions in both the stratosphere and the troposphere, depleting the ozone layer and contributing to the greenhouse effect. There are several techniques which can be utilized to remove NOx from off gasses. The most widely used of these is selective catalytic reduction (SCR). The most used SCR catalyst (V2O5/WO3 on TiO2) is not well suited for NOx abatement from alternative sources such as biomass firing, waste incineration, maritime engines etc. Therefore, a more diverse portfolio of NOx abatement solutions is needed. Recently, it has been shown that several ILs can absorb and oxidize NOx gas at ambient temperatures and pressure to form nitric acid. The nitric acid is retained in the IL until heated above 120oC[1]. Capacities slightly above a 1:1 molar ratio as well as excellent reversibility and stability of the IL was reported. It has not been possible to reproduce these capacities when using SILP (supported ionic liquid phase) at higher space velocities, with other porous supports such as silica and anatase. It is paramount that the capacity of SILP is increased for this method to become viable for NOx abatement in large scale operations. HS are hollow, nano-sized silica particles with an inner diameter of 10-15 nm, and a microporous silica shell with a wall thickness of 3-5 nm. HS have been proposed as an excellent support material for reactions and separation of smaller gas phase molecules[2]. The hollow sphere decreases mass transfer limitations for gaseous species compared to the complex microporous network found in conventional supports. It has already been shown that HS can increase both the activity and selectivity of supported Pd nano-clusters in the catalytic oxidation of hydrocarbons with oxygen[3]. Here, we present a method for using hollow silica spheres (HS) as a support for ionic liquids (ILs) in selective gas phase separation. The results presented include the first attempts on NOx absorption and oxidation in a HS-SILP, as well as a method for impregnation and “ship in a bottle” assembly of several ILs in the HS. [1] A. Kunov-Kruse, S. Mossin et. al. ACS Catal. 2015, submitted [2] J. Zhang, S. Dai et al. Angewandte Chem. Int. Ed. 2015, 54 (3), 1041 [3] Z. Qiao, S. Dai et. al. J. Am. Chem. Soc. 2014, 136, 11260

Advances in gas phase separation of NOx with supported ionic liquid phase using hollow silica spheres

251st National Meeting (2016)

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