Screening of CO₂ utilization routes from process simulation: Design, optimization, environmental and techno-economic analysis

This work aims at evaluating potential direct CO₂ conversion processes through systematic screening and process simulation. Fifteen direct routes converting CO₂ to carbonates or carbamates, with in situ chemical dehydration using 2-cyanopyridine (2-CP) are focused. The work covers an extensive examination (and supplement) on the physical properties, selection of promising routes, process simulation, optimization, environmental, and techno-economic evaluation. Firstly, three promising routes were selected, producing dimethyl carbonate (DMC), dipropyl carbonate (DPC), and Isopropyl N-phenylcarbamate (IPPhCM), based on three criteria: azeotropic search, product selectivity and reacting conditions. Next, the corresponding processes were simulated, optimized, heat-integrated, and systematically compared with the previously-proposed diethyl carbonate (DEC) process through environmental and economic analysis. From environmental analysis, the CO₂ emission rate (CO₂-e, in kg/kg-product) was 0.067, 0.088, −0.040 and −0.154 for producing DMC, DPC, IPPhCM and DEC, respectively. By reducing the excess ratio used for reaction (i.e. 2-CP/alcohol or amine/alcohol), the CO₂-e improved to −0.122, −0.086, and −0.117 for producing DMC, DPC and IPPhCM, respectively. Finally, the minimum required selling prices (MRSP) at 15 % internal rate of return (IRR) were determined, with the unit price of 2-CP, 2-picolinamide (2-PA), and the reactor residence time regarded as uncertainties. The MRSPs for DMC, DPC, IPPhCM and DEC are found in the range of 1.50–4.96, 2.29–4.24, 2.07–4.06 and 1.12–2.81 (all in USD/kg), respectively. Future studies exploring the commercial availability and the regeneration of 2-CP, and the feasibility of reducing the excess ratio and the reaction residence time are considered helpful.