Facile CO2 diffusion for decarbonization through thermal insulation membranes

Abstract

It is hypothesized and demonstrated that thermal insulation membranes can provide an effective barrier to heat flow and simultaneously facilitate effective CO₂ diffusion. Decarbonization technology often requires a CO₂ concentration system, often based on amine binding or lime reaction, which is energy intensive and carries a high carbon footprint. Alternatively, C2CNT electrolytic molten carbonate decarbonization does not require CO₂ pre-concentration and also provides a useful product (graphene nanocarbons) from the captured CO₂.

Here, a method of effective CO₂ diffusion is demonstrated that simultaneously thermally insulates the decarbonization source gas from the high-temperature C2CNT system. Open pore, low-density, thermal insulations are implemented as membranes that facilitate effective CO₂ diffusion for high-temperature decarbonization. Selected, high-temperature, strongly thermal insulating, silica composites are measured with porosities, $\epsilon$, exceeding 0.9 (>90% porosity), and which display, as measured by SEM, large open channels facilitating CO₂ diffusion. A derived and experimentally verified estimate for the CO₂ diffusion constant through these membranes is D_M-porous ​= ​${\epsilon }^{3/2}$ D_CO2, where D_CO2 is the diffusion constant in air. D_M-porous is applicable to a wide-range of CO₂ concentrations both in the air and N₂.

The CO₂ diffusion constant is translated to the equivalent decarbonization system mole influx of CO₂ and shown capable of sustaining high rates of CO₂ removal. Combined with the strong electrolyte affinity for CO₂ compared to N₂, O₂, or H₂O, the system comprises a framework for decarbonization without pre-concentration of CO₂.