Experimental study on CO2 adsorption with silica-supported ionic liquid in a high gravity reactor

Abstract

For the problem of mass transfer limitation in the process of CO2 adsorption, the high gravity reactor-Rotating Adsorption Bed (RAB) is used as a device to intensify the gas–solid mass transfer in this paper. The rapidly updated gas–solid interface formed by mean of rotation and peristalsis of dynamic adsorbent in the RAB, is the key reason for improving mass transfer effect and diffusion rate. Firstly, as filler of the RAB, mesoporous silica modified by tetraethylammonium lysine ionic liquid (N2222Lys-Si) is prepared by ultrasonic impregnation method and then characterized by FT-IR, TGA, BET, and SEM. Results show that N2222Lys is uniformly layered on silica by the interaction of electrostaticity and hydrogen bonding. When the N2222Lys loading was 16.7 %, the specific surface area, pore volume and average pore size of the adsorbent were 141.9 m2·g−1, 0.47 cm3·g−1 and 8.72 nm, respectively. The sufficient remain available pores of N2222Lys-Si facilitate the diffusion of CO2. Then, the influence of different operating factors including initial CO2 volume concentration (C0), simulated gas flow rate (Qa), high gravity factor (β), and temperature (Ta) to the adsorption capacity (qe) are explored systematically. The qe reaches 23.33 mg·g−1 at the optimal operating conditions within the experimental range, which are N2222Lys loading of 16.7 %, C0 of 10.0 %, Qa of 600 mL·min−1, Ta of 298.15 K, and β of 7.68. The adsorption process is consistent with Freundlich multi-layer adsorption and Avrami kinetic adsorption, and the adsorption rate in the RAB is intensified by increasing the external and internal diffusion rate from 1.43 and 0.46 mg·g−1·s−1/2 to 2.30 and 0.77 mg·g−1·s−1/2, respectively, with the increase of β from 1.72 to 15.88. Expectedly, excellent mass transfer characteristic makes the RAB a potential intensification device in the process of CO2 adsorption.