Synthesis of green light olefins from direct hydrogenation of CO2. Part I: Techno-economic, decarbonization, and sustainability analyses based on rigorous simulation

Abstract

BackgroundsConverting CO2 into light olefins through direct hydrogenation is a promising pathway to achieve net-zero emissions. This part aims to present a detailed layout and the analysis results of the process through rigorous simulation. MethodologyThe process encompasses three sections (reaction, CO2 removal, and olefin recovery). Two alternatives for handling the off-gas were proposed, including sending it for additional hydrogen recovery (Scheme 1) or direct combustion (Scheme 2). The minimum required selling price (MRSP), the indirect CO2 emissions per kg of olefins produced (CO2-e), and the carbon efficiency are demonstrated for process evaluation. Significant FindingsScheme 1 demonstrates better economic performance but less decarbonization ability compared to Scheme 2 (i.e. Scheme 1: MRSP = 2327 USD/kg and CO2-e = -2.036 kg/kg; Scheme 2: MRSP = 2366 USD/kg and CO2-e = -2.247 kg/kg). To achieve carbon neutrality, the carbon footprint for the hydrogen feedstock should not exceed 6.92 and 7.08 kg-CO2/kg-H2 for Schemes 1 and 2, respectively. Considering the trade-offs between MRSP and CO2-e, using biomass-based hydrogen is currently the most viable option. Finally, the entire process has a 99.7 % carbon efficiency. In summary, the proposed process is effective in CO2 fixation, with minimal impact on the process economics and sustainability.