Study On Synthesis Of Functionalized MCM-41 Mesoporous Materials And Catalytic Performance

The M41S silica-based mesoporous molecular sieves successfully synthesized have attracted great interest due to their large specific surface area, high pore volume, uniform pore size distribution, adjustable pore size and rich surface hydroxyl groups. However, the nature of the neutral framework with few lacuna, poor ion-exchange ability and lack of catalytic activity, limits their potential in catalysis, adsorption and separation and so on. Therefore, functionalized mesoporous materials have attracted more attention.By the hydrothermal method, a series of magnesium and aluminum-containing mesoporous materials MgAl-MCM-41 endowed with acid-base properties have been synthesized in one pot. The characterization results indicated that the MgAl-MCM-41 can possess the typical mesoporous structure properties, with ordered arrangement of uniform pores, high surface area and narrow pore size distribution. The magnesium and aluminum species can be efficiently introduced into the backbone, and form covalent bonds Si-O-Mg and/or Si-O-Al between the metal ions and the oxygen atoms of the Si-OH groups on the surface of MCM-41. The acidic sites, including Lewis and Br(o|¨)nsted acid sites, and basic sites co-exist on the surface of the MgAl-MCM-41 mesoporous materials.Combining the functionalized methords of backbone doping and surface modification, ionic liquids functionalized aluminum or titanium-containing MCM-41 mesoporous materials were synthesized. The characterization results indicated that the ionic liquids functionalized MCM-41 can keep mesoporous framework well, the aluminum and titanium species were efficiently introduced into the backbone and the ionic liquid groups were incorporated onto the surface of MCM-41. The cycloaddition reaction of carbon dioxide and epoxides was employed to evaluate the catalytic performance of ionic liquid functionalized MCM-41. The conversion of propylene oxide was 96% and the selectivity of propylene carbonate was 99% under the conditions: Al-MCM-41-Im(30) as the catalyst, reaction temperature 130℃, reaction pressure 3 MPa, catalyst loading 8 wt%, reaction time 6 h. Combining the functionalized methords of backbone doping and surface modification, a series of schiff base metal complexes functionalized aluminum-containing MCM-41 mesoporous materials were prepared and characterized. The characterization results showed that the schiff base metal complexes functionalized MCM-41 mesoporous materials kept mesoporous framework well, and the metal complexes groups were incorporated onto the surface of MCM-41. The conversion of propylene oxide was 97% and the selectivity of propylene carbonate was 99% under the conditions: Al-MCM-41-L1(30) as the catalyst, reaction temperature 110℃, reaction pressure 3 MPa, catalyst loading 8 wt%, reaction time 4 h.