4. Conclusions
Solid base catalysts of CaO covered with 5–20 mol% SiO2
were prepared by the decomposition of Si(OC2H5)4 over a
Ca(OH)2 surface in an ethyl acetate solution, followed by thermaldecomposition in air at 773–1023 K. Single- and double-deposition
procedures were applied to prepare the covered catalysts. Catalysts
containing 5–20 mol% SiO2 treated at 773–973 K showed sufficient
activity for the retro-aldol reaction of diacetone alcohol at 299 K.
Ca2+ ions dissolved in diacetone alcohol were detected in the catalysts
prepared by the single-deposition method. The dissolution
of Ca2+ in diacetone alcohol was strongly inhibited by covering the
surface using the double-deposition method. The prepared catalysts
showed excellent tolerance toward H2O.