Study on the hydrothermal stability of MCM-41 via secondary restructure

A series of MCM-41 mesoporous molecular sieves with different Si/Al molar ratio has been synthesized by hydrothermal crystalline method using cetyltrimethylammonium bromide as structural template, sodium silicate as silica source and sodium aluminate as aluminum source in alkaline solution. The results show that all the samples have hexagonal mesoporous structure. The secondary restructured materials exhibit well defined structure and the long distance order of the mesopores. The mesoporous structure for Si/Al = 25 MCM-41 with high specific area can be maintained after hydrothermal stability test in boiling water more than 12 h, showing that the secondary restructure can enhance the hydrothermal stability of MCM-41 with the pore diameter size of larger than 3.3 nm and BET surface area of more than 800 m2·g− 1. Furthermore, MCM-41 with Si/Al = 25 has the optimal hydrothermal stability due to the introduction of Al atom.

The XRD patterns of MCM-41 with different Si/Al molar ratio via secondary restructure show a very strong characteristic peak at 2.3° and several Bragg peaks at low reflection angles between 1.8 and 6.5°. All samples prepared can also keep the characteristic diffraction peak even after hydrothermal stability test in boiling water more than 12 h.Figure optionsDownload as PowerPoint slideHighlights
► We synthesized a series of MCM-41 with different Si/Al molar ratio using secondary restructure in hydrothermal condition.
► The secondary restructure can obviously improve the long distance order of MCM-41 materials.
► The materials can be heated more than 12 h in boiling water without suffering from significant structure damage.
► There was an optimum Si/Al molar ratio to enhance the hydrothermal stability of MCM-41.