Recovery of rare earths from spent FCC catalysts by solvent extraction using saponified 2-ethylhexyl phosphoric acid-2-ethylhexyl ester (EHEHPA)

A process to recover rare earth (RE) metals from spent fluid catalytic cracking (FCC) catalysts by solvent extraction was studied, using saponified 2-ethylhexyl phosphoric acid-2-ethylhexyl ester (EHEHPA or P507). The recovery process involved three steps: (1) leaching REs (mainly lanthanum and cerium); (2) solvent extraction by applying saponified P507-kerosene system; (3) stripping. Experiments to assure optimal operating conditions were conducted. Results indicated that RE metals could be recovered effectively from spent catalyst with saponified P507-kerosene-HCl system. At room temperature of 25 degrees C, 10 g spent catalyst with 110 mL of HCl (1 mol/L) could achieve a leaching efficiency of 85%. For extraction, initial pH value of 3.17, organic/aqueous ratio (O/A ratio) of 2:1 with an extractants' saponification rate of 20% could obtain 100% efficiency. In the stripping process, 1 mol/L HCl with O/A ratio of 1:1 led to a stripping efficiency of 96%. In the present study, RE metals from spent FCC catalysts were effectively recovered, which avoided wasting a large amount of RE resources. It provides a theoretical support for commercial recycling of RE resources.