Synthesis And Characterization Of Mesoporous Molecular Sieves Templated By Ionic Liquid

The discovery of mesoporous molecular sieves has caused a booming research in the field.Mesoporous materials has large pore diameter,pore volume and high surface area which is benefit for the spread and part in the reaction in the mesoporous channel.However mesoporous materials with pure silica have a chemical inert silicate and consequently no active sites which district its application in catalyst.Then much attention was devoted in the synthesis of hetero-atomed mesoporous materiasl for special catalytic reactions.But the heteroatom is not stable in the framework of mesoporous materials synthesized from traditional template and this limits its application in catalytic reaction.As the medium of clean-up technology and environment friendly catalytic system,room temperature ionic liquid has attracted much attention.Roomtemperature ionic liquids are simply organic liquids that are composed entirely of ions.Not only in organic reaction,ionic liquids are also used in the synthesis of inorganic materials.In this paper,ionic liquids were used as templates in the synthesis of mesoporous molecular sieves.The main contents are as follows:(1)Heteroatomed MCM-41 were synthesized templated by 1-cetyl-3-methylimidazolium bromide,these are:Al-MCM-41,Fe-MCM-41,Co-MCM-41,Cu-MCM-41 and bimetalic MgAlMCM-41,CuAl-MCM-41.For Al-MCM-41,all aluminum in as-synthesized samples exists in tetrahedral coordination.Upon calcination nearly all aluminum still remains the tetrahedral coordination even when the Si/Al ratio is as low as 15.This indicates that the tetrahedral-alumminum of Al-MCM-41 is stable.Tert-butylation of p-cresol with methyl tea-butyl-ether(MTBE)catalyzed by HAl-MCM-41 molecular sieves was investigated.The results showed that HAI-MCM-41 was an efficient catalyst with high activity,selectivity and stability for the preparation of 2-tert-butyl-p-eresol from p-cresol and MTBE.The conversion of pcresol and selectivity for 2-tert-butyl-p-cresol are 69%and 93%respectively,62% and 92%respectively after 100 hours.Mesoporous Fe-MCM-41 was synthesized using room temperature ionic liquid 1-cetyl-3-methylimidazolium bromide([C₁₆mim]Br)as template.Mesoporous Fe-MCM-41 exhibits hexagonal p6m pore architectures,and possesses high surface area. The pore size distribution of Fe-MCM-41 shows that there are two types mesoporous. Part of iron atom still retain in the framework after removal of the template by calcination except those transferring to the wall surface.Fe species on wall surface are of high dispersion.This indicates that stable framework-iron containing mesoporous molecular sieves Fe-MCM-41 have been successfully synthesized.(2)Al-MSU-S was prepared from the precursor of Y zeolite using 1-cetyl-3-methylimidazolium bromide as a template.Except higher hydrothermal stability,Al-MSU-S also possesses higher surface area,pore diameter and pore volume comparing with that templated by CTAB.The catalytic activity of Al-MSU-S-Y was studied via the acetalization and ketalization of different aldehydes and ketones with glycol.The conversion of butanone and selectivity for are butanone ethylene ketal are 80.5%and 99.1% respectively.The conversion of cyclohexanone only dropped 2.1%after recycled 10 times.FeAl-MSU-S was also synthesized using 1-cetyl-3-methylimidazolium bromide as template with lower thermol stability.(3)Except 1-cetyl-3-methylimidazolium bromide,we synthesized six ionic liquids:1-cetyl-3-methylimidazolium hydroxy,1-cetyl-3-butyl-imidazolium bromide, 1-tetradecyl-3-butyl-imidazoliumbromide,1-cetyl-1-methylmorpholin bromide,1-cetyl-1-methyl-2-pyrrolidinone bromide and -cetyl-1-methyl caprolactam bromide. These ionic liquids were applied in the synthsis of mesoporous moleculer sieves.The results show that 1-cetyl-3-methyl-imidazolium hydroxy,1-cetyl-3-butyl-imidazolium bromide,1-tetradccyl-3-butyl-imidazolium bromide and 1-cctyl-1-methylmorpholine bromide are good templates in the synthesis ofmcsoporous SiO₂.With carbonyl in the hydrophilic group,1-cctyl-1-methyl-2-pyrrolidinone bromide and 1-cctyl-1-methyl caprolactam bromide have weak ionicity and are not soluble easily in the water.So they canot be the template in the synthesis of mesoporous materials.(4)Mcsoporous SiO₂ and TiO₂ were synthesized in ionic liquid via colloidal-gel method.The results show that short-chained dicationic ionic liquid also is good template for the synthesis of mesoporous materials.This developed a new method for the synthesis of mesoporous.