CO2 conversion by high-dose rate electron beam irradiation: one-step, metal-free and simultaneous production of H2, CO, CH4, C2H6 and organic acids from an acid-decomposed CaCO3/additive EtOH mixture

The reduction in CO2 emissions is an important issue across many industries. Inspired by extraterrestrial organic matter formation, we herein report a CO2 conversion approach based on high-dose rate electron beam (EB) irradiation of an acid-decomposed CaCO3/additive EtOH mixture. With 13C-CaCO3, 12C-EtOH and 100 kGy s−1 EB, H2, CO, CH4, C2H6 and organic acids are simultaneously produced within a few seconds, except for 2,3-butanediol formation from excess EtOH. According to the organic analysis results, CO and organic acids contain 13C carbon derived from 13C-CaCO3. The high-dose rate EB gives increased CO2 conversion products compared to the low-dose rate EB. The CO2 conversion yield/energy efficiency (product energy/input electrical energy) at 300 kGy is 1.51/0.50% in total (CO: 0.03/0.01%, formic acid: 1.31/0.29%, acetic acid: 0.05/0.04% and propionic acid: 0.12/0.16%), and the total radiation energy efficiency (REE, product energy/net radiation energy) of CO2 at 300 kGy is 51.5% (CO: 0.90%, formic acid: 30.3%, acetic acid: 3.71% and propionic acid: 16.6%). The CO2 conversion yield is ∼15 times larger than that of the only known CO2 gas radiolysis (0.1%, CO only). Furthermore, the REE at 100 kGy is also ∼15 times higher than that obtained in the absence of EtOH. The energy input for the 100% conversion yield is estimated to be 38 000 GJ per t-CO2. The combination of the high-dose rate EB with organic additives facilitated CO2 capture by radicals to afford improved CO2 conversion efficiency/yield.