Adsorption of CO2 by synthetic zeolites

The paper reports on a possible way to recycle fluid catalytic cracking catalysts (FCCCs), widely used in oil refining operations. This research proposes a novel approach that leads to a near zero-waste process. The spent FCCC was leached by 1.5 mol/L of HNO3, HCl and H2SO4 solutions at 80°C, for 3 h with a solid to liquid ratio of 20 %wt/vol. The leaching yields for cerium and lanthanum were in the range 69-82 %. The solid residues from the leaching stage were used as base material for the synthesis of the zeolites by means of a combined thermal-hydrothermal treatment. The characterization of the zeolites demonstrated that the Na-A phase was predominant over the Na-X phase. The zeolites were tested as sorbent material for CO2 separation from CH4, in order to simulate the upgrading of biogas to biomethane. The maximum adsorption rate of CO2 was 0.778 mol CO2/kg of zeolite at 3 bar, with a resulting CH4 recovery of 62 % and purity of 97 %vol. The zeolites synthesized from spent FCCC represent a feasible solution to recover such industrial waste.