CO2/CH4 adsorption at high-pressure using silica-APTES aerogel as adsorbent and near infrared as a monitoring technique

The synthesis of adequate adsorbents and efficient methods to separate CO2 present in natural gas streams in petroleum industry has been receiving increased attention in academic and industrial centers. The presence of CO2 in those streams causes serious inconvenient in the transport and processing of natural gas. In this work, the synthesis of pure (SA) and functionalized with (3-aminopropyl) triethoxysilane (APSA) silicas aerogel was performed under microwave irradiation and subsequent drying with supercritical CO2 (SC-CO2). Materials were characterized in relation to their surface area (BET), pore volume (BJH), thermal decomposition (TGA), carbon, hydrogen and nitrogen content (CHN), functional groups (FTIR) and morphology (SEM). The results indicated a modification of the surface of silica with APTES. In addition, the methodology for synthesis and drying of the silica aerogel was efficient and reduced the total time of synthesis. Materials were used as adsorbents in the separation of CO2/CH4 mixtures by using a high-pressure adsorption cell coupled to a near infrared spectroscopy (NIR) probe to monitor CO2 and CH4 concentrations. Adsorption experiments were conducted at 20°C, pressures from 90 to 120 bar and CO2 concentration in the mixture up to 10 mol%. Silica APSA presented adsorptive capacities of 3.30 mmol g−1 at 90 bar and 10.20 mmol g−1 at 120 bar, better than those obtained with the commercial 3-aminopropyl-functionalized silica gel (APSC) of 0.88 mmol g−1 at 90 bar and 9.43 mmol g−1 at 120 bar. NIR was able to quantify the adsorption of CO2 at high-pressure.