Hydrophobic titania-silica aerogels:: epoxidation of cyclic compounds

被引:26
作者
Müller, CA [1 ]
Deck, R [1 ]
Mallat, T [1 ]
Baiker, A [1 ]
机构
[1] Swiss Fed Inst Technol, ETH Zentrum, Tech Chem Lab, CH-8092 Zurich, Switzerland
关键词
titania-silica aerogel; epoxidation; organic modification; methyltrimethoxysilane; phenyltrimethoxysilane; cyclohexene; cyclohexenol; tert-butylhydroperoxide;
D O I
10.1023/A:1027202604286
中图分类号
O69 [应用化学];
学科分类号
081704 ;
摘要
Titania-silica mixed oxides with covalently bound methyl or phenyl groups were prepared from the corresponding alkyltrimethoxysilane and tetramethoxysilane using a sol-gel process and ensuing low-temperature supercritical extraction with CO2. Prehydrolysis of the organically modified silicon precursor was applied to compensate for their lower sol-gel reactivity compared to the precursors of the other constituents. Trihexylamine was used as a gelation catalyst. The dominantly mesoporous aerogels were characterized by thermal analysis, N-2 adsorption, infrared spectroscopy, Si-29- and C-13-NMR spectroscopy, and transmission electron microscopy. Thermal analysis and Si-29 MAS NMR measurements indicated covalent incorporation of the modifying group. C-13 NMR spectra confirmed the integrity of the incorporated modifying groups. The materials were tested in the epoxidation of cyclohexene and cyclohexenol with tert-butylhydroperoxide. NH3 adsorption studied by DRIFT spectroscopy indicated no significant acidity of the aerogel surfaces, which was traced to the use of trihexylamine as gelation catalyst. Addition of zeolite 4 Angstrom or NaHCO3 did not improve the performance of the unmodified and phenyl-modified aerogel, corroborating the suppressed acidity of the surface. Interestingly, the phenyl-modified aerogel was more selective in the epoxidation of cyclohexenol, when using polar solvents (ethanol or acetone), compared to the reaction in toluene.
引用
收藏
页码:369 / 378
页数:10
相关论文
共 26 条
[1]   EFFECT OF DRYING TEMPERATURE ON THE PHYSICAL-PROPERTIES OF TITANIA AEROGELS [J].
BRODSKY, CJ ;
KO, EI .
JOURNAL OF MATERIALS CHEMISTRY, 1994, 4 (04) :651-652
[2]  
BROEKHOFF JCP, 1979, PREPARATION CATALYST, V2, P663
[3]   Ti-containing MCM-41 catalysts for liquid phase oxidation of cyclohexene with aqueous H2O2 and tert-butyl hydroperoxide [J].
Chen, LY ;
Chuah, GK ;
Jaenicke, S .
CATALYSIS LETTERS, 1998, 50 (1-2) :107-114
[4]   Mesoporous materials as catalysts for the production of chemicals: Synthesis of alkyl glucosides on MCM-41 [J].
Climent, MJ ;
Corma, A ;
Iborra, S ;
Miquel, S ;
Primo, J ;
Rey, F .
JOURNAL OF CATALYSIS, 1999, 183 (01) :76-82
[5]   SYNTHESIS OF AN ULTRALARGE PORE TITANIUM SILICATE ISOMORPHOUS TO MCM-41 AND ITS APPLICATION AS A CATALYST FOR SELECTIVE OXIDATION OF HYDROCARBONS [J].
CORMA, A ;
NAVARRO, MT ;
PARIENTE, JP .
JOURNAL OF THE CHEMICAL SOCIETY-CHEMICAL COMMUNICATIONS, 1994, (02) :147-148
[6]   Trimethylsilylation of ordered and disordered titanosilicates:: improvements in epoxidation with aqueous H2O2 from micro- to meso-pores and beyond [J].
D'Amore, MB ;
Schwarz, S .
CHEMICAL COMMUNICATIONS, 1999, (02) :121-122
[7]   Titania-silica mixed oxides: Influence of reaction additives on the epoxidation of (E)-2-hexen-1-ol [J].
Dusi, M ;
Mallat, T ;
Baiker, A .
JOURNAL OF CATALYSIS, 1998, 173 (02) :423-432
[8]   TITANIA-SILICA MIXED OXIDES .1. INFLUENCE OF SOL-GEL AND DRYING CONDITIONS ON STRUCTURAL-PROPERTIES [J].
DUTOIT, DCM ;
SCHNEIDER, M ;
BAIKER, A .
JOURNAL OF CATALYSIS, 1995, 153 (01) :165-176
[9]   Effects of hydrophobicity on the epoxidation of cyclohexene by tert-butyl hydroperoxide on TiO2-SiO2 mixed oxides [J].
Figueras, F ;
Kochkar, H .
CATALYSIS LETTERS, 1999, 59 (01) :79-81
[10]   TITANIA-SILICA MIXED OXIDES .2. CATALYTIC BEHAVIOR IN OLEFIN EPOXIDATION [J].
HUTTER, R ;
MALLAT, T ;
BAIKER, A .
JOURNAL OF CATALYSIS, 1995, 153 (01) :177-189