Loss of Supported ILs by Evaporation

To explain the mechanism of mass loss by evaporation, five scenarios and rate depending steps (r.d.s.) were assumed, simulated, and compared with the experiments. Subsequently, the equations of these five models are derived and the respective parameters for the experiments at 174°C with [EMIM][NTf2] coated on silica are given. 

Model I Effusion From External Surface of the Silica Particles is r.d.s. If the effusion 

the rate is proportional to the saturation pressure ([EMIM](NTf2] 3.3 mPa at 174 C)  

Model II Pore Diffusion in the Particles is r.d.s. (Knudsen Diffusion, Shrinking Core Model] If pore diffusion (Knudsen diffusion at HV) in the silica particles limits the mass loss and we assume that an IL-free shell is formed (shrinking core model), the mass loss is given by 

For pore diffusion in the IL-free shell region, we use the mean pore diameter (dp.) of 12 nm, a particle porosity (Sp) of 0.72, and the tortuosity t is estimated by 1/Sp. Hence we get  

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