Preparation of silicate foams using HSi(OC2H5)3 and their NOx adsorption behavior

Lithium silicate foams have been prepared by reaction of HSi(OC2H5)3 with aqueous lithium silicate solution. During hydrolysis and condensation reactions of ethoxy groups, Si–H bonds were also broken under the base condition of aqueous lithium silicate solution with the evolution of hydrogen gas. The gelation occurred immediately and during the gelation the hydrogen gas produced macro-voids to provide lithium silicate foams. The wall of the macro-voids in the foams was made up of particulate porous gels with about 50 nm-sized particles. The surface of the lithium silicate foams showed the solid-basic property of H0=9 and adsorbed the acidic gases of NO and NO2. FT-IR spectrum of both the lithium silicate foams adsorbing NO and NO2 showed an absorption peak at 1385 cm−1 assigned to the ν3 stretching vibration of nitrate species, NO3−. The absorption peak of NO3− disappeared in the samples heated at 500 °C in air.