English abstract
Conventional amine-based solvents currently used for CO2 capture processes are liable for some operational, environmental and economic issues. The need for developing better and more environmentally friendly solvents has attracted the
attention of many research groups on a global level.
In this work, two new solvents are proposed and evaluated for potential use as CO2 capture solvents. The first solvent is an equimolar Diethanolamine (DEA) and Sarcosine (SAR) aqueous solution and the second solvent is an equimolar
Triethanolamine (TEA) and Sarcosine aqueous solution. Both aqueous systems were prepared at four different mass concentrations (2.5, 5, 7.5, and 10 wt%) of DEA-SAR or TEA-SAR. Physical properties including density (which is needed for the CO2 loading calculation), viscosity and refractive index (RI) for DEA-SAR and TEA-SAR aqueous solutions were measured for all the compositions at different temperatures (303.15, 313.15, and 333.15 K). The physical properties results for the two systems
showed that density increased by increasing the concentration and decreased by increasing the temperature. The viscosity results showed that viscosity increases with concentration and decreases with increasing the temperature.
CO2 loading (defined as moles of CO2 absorbed per mole solvent) for the proposed two systems was experimentally measured in a solubility cell apparatus at different pressures (4, 8, 12, and 16 bar), different temperatures (303.15, 313.15, and
333.15 K) and different mass concentrations (2.5, 5, 7.5 and 10 wt%). The parameters for the conducted experiments were optimized using Design Expert software to select the recommended parameters for each experiment and the number of experiments to be conducted. The experimental results showed that CO2 solubility increases when the concentration and temperature decrease. Moreover, the CO2 solubility increased with increasing the pressure. Similar observations were reported in literature for different amine-amino acid systems.
The CO2 loading for the DEA-SAR system ranged from a minimum of 0.29 mole CO2/mole solvent at (333.15 K, 4.095 bar and 10 wt% DEA-SAR) to a maximum loading of 3.37 mole CO2/mole solvent at (313.15 K, 15.95 bar and 2.5 wt% DEA- SAR). However, for the TEA-SAR system, the CO2 loading ranged from a minimum of 0.2 mole CO2/mole solvent at (333.15 K, 4.062 bar and 10 wt% DEA-SAR) to a maximum loading of 3.22 mole CO2/mole solvent at (313.15 K, 16.054 bar and 2.5 wt% DEA-SAR).
To evaluate the effect of adding Sarcosine, a comparison between DEA-SAR aqueous solutions and DEA aqueous solutions was conducted at similar temperatures, pressures and compositions. It was observed that adding Sarcosine enhanced the CO2 loading in DEA-SAR by 23.7% over the DEA aqueous solution. Similar comparison was done between TEA-SAR aqueous solution and TEA aqueous solution which demonstrated that adding sarcosine increased the CO2 loading capacity of TEA-SAR by 15.3 % over TEA aqueous solution. In addition, a comparison between the two amine-amino acid salt systems DEA-SAR & TEA-SAR was done at the same conditions. The results showed that the (DEA-SAR) aqueous solution has better CO2 loading than TEA-SAR system.
