One-pot dual functional materials preparation for ICCU-RWGS

Except physical mixing of sorbent and catalyst, and impregnating sorbent with catalyst, one-pot synthesis of dual functional materials (DFMs) is another common method.

In the one-pot synthesis, catalytic sites (e.g. Ni), adsorption sites (e.g. Ca) and promotor (e.g. Ce) if used are mixed together, normally using sol-gel methods.

For example, the following methodologies are from https://doi.org/10.1039/D0EE03320K

“Fe_xCo_yMg₁₀CaO was prepared through a simple one-pot sol–gel method⁴⁷ and subsequent calcination. Typically, 8.43 g of calcium nitrate tetrahydrate (equivalent to 2 g CaO) and 2.133 g magnesium nitrate hexahydrate (the mass fraction of Mg based on CaO was 10%) were dissolved in an aqueous solution at room temperature with a molar ratio of Ca²⁺ to water of 1 : 40. Then, 7.5 g of the chelating agent of citric acid monohydrate was added under stirring. After mixing for 0.5 h, iron nitrate nonahydrate and cobalt nitrate hexahydrate with a total loading amount of 10 wt% corresponding to CaO were added into the mixture solution. Under vigorous stirring at 90 °C for 5 h, a transparent light-yellow sol was obtained. After filtration, it was further dried at 120 °C overnight and calcined in a muffle furnace at 800 °C for 4 h with a heating rate of 2 °C min⁻¹. The obtained samples were denoted Fe_xCo_yMg₁₀CaO (x and y are the mass percentage of Fe and Co corresponding to CaO, respectively). Fe₁₀Mg₁₀CaO and Co₁₀Mg₁₀CaO, as well as pure CaO, were also prepared as reference samples. All the samples were crushed and compacted into fine pelleted particles of 40–50 mesh (0.35–0.45 mm or 10–20 mesh (0.85–2.0 mm) before the CO₂ capture and conversion test.”

Sun et al. (https://doi.org/10.1016/j.apcatb.2018.11.040) also reported the sol-gel method to prepare one-pot DFMs.

“All the DFMs were synthesized by a standard sol-gel combustion method reported by Santos et al. [47] and a typical synthesis process is as follows. Initially, predetermined amounts of analytical reagent-grade calcium nitrate tetrahydrate (Ca(NO₃)₂·4H₂O, Sigma-Aldrich, 99.99%), nickel nitrate hexahydrate (Ni(NO₃)₂·6H₂O, Sigma-Aldrich, 99.99%) and citric acid monohydrate (Sigma-Aldrich, 99.99%) working as the chelation agent were added to distilled water at room temperature (water, citric acid and Ni²⁺ to Ca²⁺ molar ratios were 40:1, 1:1 and 0.1:1, respectively). Subsequently, for the Ce-doped DFMs, appropriate amounts of cerium nitrate hexahydrate (Ce(NO₃)₂·6H₂O, Sigma-Aldrich, 99.99%) were added to the mixture solution and the Ce²⁺ to Ca²⁺ molar ratios were 1:60 and 1:30. Then, the mixture was continuously stirred at 80 °C to form a well-dispersed translucent pale green sol. The pale green sol was dried overnight at 130 °C. After drying, a low-density foam was obtained. The foam was easily crushed in a porcelain mortar and then calcined in a muffle furnace at 850 °C for 5 h with a heating rate of 2 °C min⁻¹. The obtained samples are designated as Ca₁Ni_0.1, Ca₁Ni_0.1Ce_0.017, and Ca₁Ni_0.1Ce_0.033, respectively. Pure sol-gel CaO was also prepared according to the same method used as the reference adsorbent.”