Stage 1 Group 1 metal/porous metal oxide compositions or Stage II Group 1 metal/porous metal oxide compositions are shown to be useful to remove impurities and act as drying agents for various types of solvents and for olefinic monomers used in anionic polymerizations. One important advantage of these compositions is their ability to dry simultaneously solvent and monomers, without inducing a significant polymerization of the latter. Another important characteristic is the capacity of the compositions to be totally inactive toward conventional anionic polymerization which allows them to be left in situ during the polymerization itself.