Ru/K2CO3–MgO catalytic sorbent for integrated CO2 capture and methanation at low temperatures

Dual Functional Materials: At the Interface of Catalysis and Separations

“…10 kPa CO 2 , or 10% CO 2 at atmospheric pressure, a commonly studied CO 2 concentration. 2,11,16,24 The exact transition likely shifts as a function of the DFM identity, but this study suggests that it may be difficult to compare DFM performance because the adsorption kinetics transition is close to commonly studied conditions. Designing an effective DFM also requires consideration of the synergy between the adsorbent and the catalytic active site, as illustrated in Figure 3.…”

“…H 2 is typically used in excess to achieve high CO 2 conversions and CH 4 selectivities that exceed 90% on a basis of adsorbed CO 2 . 11 However, thermodynamics prevents CO 2 methanation from operating at full conversion, indicating that renewable H 2 will be wasted in the product stream, which is undesirable because the purpose of the process is to store renewable energy as CH 4 . 13 If significant amounts of H 2 are mixed with CH 4 at the reactor outlet, then the overall scheme of hydrogenating CO 2 becomes less efficient than using H 2 directly.…”

“…The discrepancy between the calculations ultimately depends on the basis of the calculation: CO 2 flowed over the DFM, CO 2 adsorbed, or CO 2 desorbed plus products formed. 11,37 Selected definitions from the literature are summarized below:…”

“…In the case of "CO 2 desorbed", it is likely that a fraction of the adsorbed CO 2 does not desorb from the DFM, which is mistakenly mathematically counted as converted CO 2 , thereby inflating the conversion calculation. 11 The two commonly used definitions are also not a function of the cycle time, which is important because if 10% CO 2 is flowed over 0.5 g of DFM at 40 mL/min for 1 h, 1.12 mmol CH 4 /g DFM translates to an actual CH 4 yield of 5.7%, and not 97.4% when 1.15 mmol CO 2 captured/g DFM is used as the basis of the calculation. 11 Furthermore, using definitions (2) or (3) makes it difficult to calculate the maximum equilibrium conversion because the equilibrium value is a function of the H 2 amount flowed over the DFM, which is generally orders of magnitude larger than the stoichiometric amount, as we show in the Introduction where the effluent H 2 /CH 4 ratio is 158/1.…”

Zr-Modified Ni/CaO Dual Function Materials (DFMs) for Direct Methanation in an Integrated CO2 Capture and Utilization Process

“…Integrated CO 2 capture and utilization (ICCU) has arisen as a promising climate mitigation technology that uses dual function materials (DFMs) to directly transform captured CO 2 into fuels and chemical commodities without the need for separation and purification. − For conventional CCU, the CO 2 is separated from various waste streams (e.g., flue gas), transported using a pipeline, and transformed into fuels and chemical commodities, in which decarbonation is the most energy-intense process. ,, For example, CaO sorbent materials capture CO 2 as a formation of CaCO 3 at 500–700 °C, and then spent sorbents (CaCO 3 ) are regenerated under condensed or pure CO 2 condition at higher temperatures (∼950 °C), followed by purification to achieve pure CO 2 feedstock. The separated CO 2 is catalytically converted to value-added chemicals.…”