The invention relates to a composition comprising anionic clay and rare earth metal hydroxy carbonate. This composition can suitably be used in FCC for the reduction of NOx and/or SOx emissions, the reduction of the S and/or N-content in fuels, and as a metal trap.The composition can be prepared by precipitating a divalent metal salt, a trivalent metal salt, and a rare earth metal salt to form a precipitate, calcining the precipitate at 200-800.degree. C., and rehydrating the precipitate in the presence of a carbonate source to form a composition comprising anionic clay and a rare earth metal hydroxy carbonate.