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Nonvolatile Colloidal Dispersion of MgO Nanoparticles in Molten Salts for Continuous CO2 Capture at Intermediate Temperatures

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journal contribution
posted on 22.03.2019, 00:00 by Takuya Harada, Paul Brown, T. Alan Hatton
The establishment of advanced CO2 capture, utilization, and storage (CCUS) technology is a crucial challenge for the mitigation of serious ongoing climate change. Herein, we report nonaqueous colloidal dispersions of MgO nanoparticles in molten salts as a new class of fluid absorbents for continuous CO2 capture at intermediate temperatures ranging from 200 to 350 °C. The colloidal absorbents were developed by dispersion of the nanoparticles in three different types of thermally stable low-melting point salts: ternary-eutectic alkali-metal nitrates ((Li–Na–K)­NO3), tetraphenyl­phosphonium bis­(trifluoro­methane)­sulfonimide ([P­(Ph)4]­[NTf2]), and their mixtures. The new absorbents show high CO2 uptake performance with acceptable rheological properties at the target temperatures. The analysis of reaction rate kinetics in the uptake of CO2 revealed that CO2 can diffuse quickly into the molten salts to initiate the rapid formation of carbonates on the surfaces of MgO nanoparticles dispersed in these molten salts. These results demonstrate that the new colloidal dispersions could be used as fluid absorbents for advanced continuous CO2 capture processes at the temperatures of exhausts from fossil fuel combustion reactors without the energy losses incurred upon cooling of the gases as required for traditional absorption systems.