Alkaline-substituted sepiolites as a new type of strong base catalyst

Strong base catalysts have been prepared by substituting a part of the Mg z+ located at the borders of the channels of sepiolite with alkaline ions. These materials show higher basicity than alkaline X zeolites and are able to catalyze at moderate temperatures the condensation of benzaldehydes with ethyl cyanoacetate, ethyl acetoacetate, and ethyl malonate. The kinetic rate constants obtained indicate that alkaline sepiolites have basic sites with strengths corresponding to pKb ≤ 13.3, with most of the sites showing basicities up to pK b = 10.7.