Multiphasic Acetalization and Alkylation on Organically Modified MSU-X Silica (original) (raw)
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Mesoporous silica-aluminas as catalysts for the alkylation of aromatic hydrocarbons with olefins
Microporous and Mesoporous Materials, 1999
Two amorphous mesoporous silica-aluminas are compared with the amorphous microporous silica-alumina (ERS-8) and the zeolite beta in the liquid-phase alkylation of toluene with propylene. The catalytic activity, the selectivity to o-, m-and p-cymenes and the formation of polyalkylates are discussed as a function of acidity and porosity. The catalytic behaviour of MSA, MCM-41, ERS-8 and zeolite beta is also compared with data reported in the literature for traditional alkylation catalysts (AlCl 3 -HCl and supported phosphoric acid, SPA) and for other acidic zeolites. MSA and MCM-41 show alkylation activities comparable with zeolite beta, while their isomerization and transalkylation activities are lower than those of zeolite beta and AlCl 3 -HCl, but similar to SPA. Such behaviour is in agreement with the Brønsted acidity of the materials studied.
Comptes Rendus Chimie, 2016
High surface area mesoporous silica based catalysts have been prepared by a simple hydrolysis/solegel process without using any organic template and hydrothermal treatment. A controlled hydrolysis of ethyl silicate-40, an industrial bulk chemical, as a silica precursor, resulted in the formation of very high surface area (719 m 2 /g) mesoporous (pore size 67 Å and pore volume 1.19 cc/g) silica. The formation of mesoporous silica has been correlated with the polymeric nature of the ethyl silicate-40 silica precursor which on hydrolysis and further condensation forms long chain silica species which hinders the formation of a close condensed structure thus creating larger pores resulting in the formation of high surface mesoporous silica. Ethyl silicate-40 was used further for preparing a solid acid catalyst by supporting molybdenum oxide nanoparticles on mesoporous silica by a simple hydrolysis solegel synthesis procedure. The catalysts showed very high acidity as determined by NH 3-TPD with the presence of Lewis as well as Brønsted acidity. These catalysts showed very high catalytic activity for esterification; a typical acid catalyzed organic transformation of various mono-and di-carboxylic acids with a range of alcohols. The in situ formed silicomolybdic acid heteropoly-anion species during the catalytic reactions were found to be catalytically active species for these reactions. Ethyl silicate-40, an industrial bulk silica precursor, has shown a good potential for its use as a silica precursor for the preparation of mesoporous silica based heterogeneous catalysts on a larger scale at a lower cost.
Glycerol Acetylation over Organic-Inorganic Sulfonic or Phosphonic Silica Catalysts
ChemistrySelect, 2017
Silica based catalysts containing organic framework with both amino and sulfonic or phosphonic functions were synthesized, characterized and tested in esterification reaction of aliphatic polyalcohols as glycerol. The aim of the research was to study the relations between the structure and the activity of the materials focusing on both, the effect of the amino group and the influence of aliphatic or aromatic chain on the acidic active sites. The effects of the sulfonic and phosphonic functions and the morphology of SiO 2 , amorphous or mesostructured Santa Barbara Amorphous (SBA-15), were also addressed. The materials were compared with some commercial catalysts, showing good performances in term of activity and stability. Fresh and spent specimens were analyzed by means of thermo-gravimetrical analysis (TGA), X-ray photoelectron spectroscopy (XPS), small angle X-ray scattering (SAXS), FT-Infrared spectroscopy (FT-IR) and acid capacity measurements. The best performances in terms of glycerol conversion and selectivity to acetins were achieved in presence of the sulfonic function linked to the amino-propyl SiO 2 , while the highest stability during three catalytic cycles was registered for the analogous SBA-15 sample.
A prospective study on Silica based heterogeneous catalyst as modern organic synthesis tool
ABSTRACT The objective of this tutorial review is to summarize some of the recent advances in a specific class of silica based multifunctional, heterogeneous catalysis. We are focusing on recent advances have led to the preparation of silica materials containing multiple, different functional groups that can be used as catalyst in organic synthesis. In this review we summarizes the recent used silica based catalyst in synthesis of different organic compounds their preparation, reaction schemes and procedures. This review will help the reader to understand the preparation and use of silica based catalyst in both theoretical and practical aspect. Key words: Silica based catalyst, Heterogeneous catalyst, Green synthesis, Organic synthesis
Acetalization of glycerol using mesoporous MoO 3/SiO 2 solid acid catalyst
Journal of Molecular Catalysis A-chemical, 2009
Acetalization of glycerol with various aldehydes has been carried out using mesoporous MoO 3 /SiO 2 as a solid acid catalyst. A series of MoO 3 /SiO 2 catalysts with varying MoO 3 loadings (1-20 mol%) were prepared by sol-gel technique using ethyl silicate-40 and ammonium heptamolybdate as silica and molybdenum source respectively. The sol-gel derived samples were calcined at 500 • C and characterized using various physicochemical characterization techniques. The XRD of the calcined samples showed the formation of amorphous phase up to 10 mol% MoO 3 loading and at higher loading of crystalline ␣-MoO 3 on amorphous silica support. TEM analyses of the materials showed the uniform distribution of MoO 3 nanoparticles on amorphous silica support. Raman spectroscopy showed the formation of silicomolybdic acid at low Mo loading and a mixture of ␣-MoO 3 and polymolybdate species at high Mo loadings. Moreover the Raman spectra of intermediate loading samples also suggest the presence of -MoO 3 . Acetalization of glycerol with benzaldehyde was carried out using series of MoO 3 /SiO 2 catalysts with varying MoO 3 loadings (1-20 mol%). Among the series, MoO 3 /SiO 2 with 20 mol% MoO 3 loadings was found to be the most active catalyst in acetalization under mild conditions. Maximum conversion of benzaldehyde (72%) was obtained in 8 h at 100 • C with 60% selectivity for the six-membered acetal using 20% MoO 3 /SiO 2 . Interestingly with substituted benzaldehydes under same reaction conditions the conversion of aldehydes decreased with increase in selectivity for six-membered acetals. These results indicate the potential of this catalyst for the acetalization of glycerol for an environmentally benign process.
Combined Alkyl and Sulfonic Acid Functionalization of MCM-41-Type Silica
Journal of Catalysis, 2000
The esterification of glycerol with lauric and oleic acids (1:1 molar ratio) has been carried out by using hybrid MCM-41 materials containing simultaneously alkyl (methyl or propyl) and sulfonic acid groups as catalysts. It has been found that for each fatty acid the catalyst activity is affected by the concentration of methyl groups, and maximum activity per sulfonic acid group is achieved by tuning the methyl/sulfonic acid ratio. Monolaurin yield of 63% is obtained with the most active catalyst, whereas for oleic acid the maximum monoolein yield was 45%. Reduction of the average pore size (determined by N 2 adsorption) from 14 to below 10 Å has a detrimental influence on the catalyst activity for both acids.