Recycled eggshells as precursors for iron-impregnated calcium oxide catalysts for partial oxidation of methane

One-pot preparation of H2-mixed CH4 fuel and CaO-based CO2 sorbent by the hydrogenation of waste clamshell/eggshell at room temperature

The preparation of clean fuel or CO₂ adsorbents using industrial and domestic garbage is an alternative way of meeting global energy needs and alleviating environmental problems. Herein, H₂-mixed CH₄ fuel and CaO-based CO₂ sorbent were first prepared in one pot by the mechanochemical reaction of pretreated clamshell or eggshell wastes (carbon and calcium source) with calcium hydride (hydrogen source) at room temperature. In the above reactions, CH₄ was the sole hydrocarbon product, and its yield reached 78.23%. The H₂/CH₄ ratio of the produced H₂-mixed CH₄ fuel was tunable according to the need by changing the reaction conditions. It is inspiring that the simultaneously formed solid CaO/carbon products were efficient CaO-based sorbents, which possessed a higher CO₂ adsorption capacity (49.81-58.74 wt.%) at 650 °C and could maintain good adsorption stability in 30 carbonation/calcination cycles (average activity loss per cycle of only 1.6%). The three achievements of the idea are that it can simultaneously eliminate clamshell or eggshell wastes, obtain valuable clean fuel, and acquire efficient CaO-based sorbents.