The XRD profiles of SiO2/CaO–n and SiO2/CaO–5 + 10 calcined at
773 K are shown in Fig. 2. The XRD profiles of samples heat-treated
and samples allowed to stand in air for one day after heat treatment
were compared. These are denoted fresh and exposed, respectively.
The XRD profile of SiO2/CaO–5 + 10 used for the reaction of diacetone
alcohol with 5 wt% water is also shown.