TECHNOLOGY FOCUS - CHEMICAL ENGINEERING - Preferred Method: The converting step comprises steam reforming, auto-thermal reforming, partial oxidation or catalytic partial oxidation of the carbon-based fuel. The method further comprises contacting the H2-rich gas with a water-gas shift catalyst. The above steps are repeated at least 50 (preferably at least 500) times. The contacting step occurs at not more than 800 degrees C. The regenerating step comprises heating the absorbent material to at least 700 degrees C. The method further comprises providing steam or oxygen-containing gas with the carbon-based fuel. The repeating steps convert the pelletized absorbent material to a carbonized absorbent material having a second bulk density, and after the repeating steps the carbonized absorbent material has a third bulk density of up to 140% of the first bulk density. The heating step comprises first heating step to react the active absorbent precursor to intermediate precursor compound and second heating step to convert the intermediate precursor compound to the absorbent material. It comprises heating the precursor droplets to at least 200 (preferably at least 300) degrees C. It is carried out in a spray dryer or spray pyrolysis reactor.    TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The first conversion catalyst is a steam reforming catalyst, or water-gas shift catalyst. The absorbent material retains at least 70 (preferably at least 90) mol% of the theoretical capacity after the repeating step. The absorbent material comprises Group 1 and Group 2 metal oxides. It comprises calcium-containing compound such as calcium oxide (CaO), or Li2O. It is CaO:MgO, CaO:Al2O3, CaO:TiO2, CaO:ZrO2, or CaO:Al2O3:MgO. It is in the form of pellet, monolith or extrudate. It is coated on a support structure. It comprises particulates having spherical morphology. It retains at least 10 (preferably at least 40) g CO2/100 g unreacted absorbent compound after each repeating step. The catalyst achieves at least 95% of the theoretical thermodynamic conversion. The particulate support consists of metal oxides of aluminum, cerium, zirconium, lanthanum, silicon, magnesium, and/or zinc. The dispersed metal is rhodium, nickel, ruthenium, platinum, palladium, or its alloys (preferably rhodium). The absorbent material comprises absorbent compound having a reaction fraction of at least 70%, or at least 30 mol% after 100 cycles. The absorbent phase precursor is calcium oxalate, calcium nitrate, calcium acetate, calcium hydroxide, or calcium nitrate. The precursor solution further comprises porosity enhancing agent. The composite particles have an average particle size (d50) of 1-30 micron. Preferred Compositions: The absorbent material comprises at least 30 wt.% CaO. The H2-rich gas comprises at least 95 mol% H2 after each repeating steps. The reforming catalyst comprises 0.1-1 wt.% metal. The mass ratio of the absorbent material to the conversion catalyst is greater than 1:1 (preferably 9:1-5:1).