Mesoporous silicas containing carboxylic acid: Preparation, thermal degradation, and catalytic performance

The calcination and thermal degradation behaviors of surfactants in mesoporous silicas SBA-15 and MCM-41 were investigated by FT-IR, 13C CP/MAS NMR, TG/DTA, and GPC. It was found that carboxylic acid-containing products were generated as active components in the mesopores of SBA-15 and MCM-41 from the triblock copolymer (PEO)20(PPO)70(PEO)20 and cetyltrimethylammonium bromide (CTAB), respectively; the latter materials were used as templates. The carboxylic acid-containing mesoporous silica obtained showed a catalytic activity for hydrolysis of sucrose. The acidity was evaluated by means of NaOH titration. The acidity sensitively depended on both the calcination temperature and the atmosphere; the maximum appeared at 150 °C in air for SBA-15 where the highest activity was observed. However, the product in MCM-41 showed a lower catalytic activity than that in SBA-15. The SBA-15 product was easily leached from the mesopores of SBA-15 into the solution, but the degree of leaching for MCM-41 was considerably smaller than that for SBA-15.

Carboxylic acid-containing products were generated in the mesopores of SBA-15 and MCM-41 during the calcination and thermal degradation of the triblock copolymer, (PEO)20(PPO)70(PEO)20, and cetyltrimethylammonium bromide (CTAB) as templates. The acidity sensitively depended on both the calcination temperature and the atmosphere.Figure optionsDownload as PowerPoint slide