Cation-exchanged Montmorillonite Research Articles

Scandium cation-exchanged montmorillonite catalyzed direct C-glycosylation of a 1,3-diketone, dimedone, with unprotected sugars in aqueous solution

The condensation of dimedone with unprotected sugars in aqueous solution in the presence of a catalytic amount of Sc 3+-montmorillonite (Sc 3+-mont) gave 9-hydroxyalkyl-3,3,6,6,-tetramethyl-3,4,5,6,7,9-hexahydro-1 H-xanthene-1,8(2 H)-diones in good yields, while the use of Sc(OTf) 3 instead of Sc 3+-mont gave the hydroxyalkyl-6,7-dihydrobenzofuran-4(5 H)-one derivatives in good yields. Furthermore, Sc 3+-mont could be recycled without inactivation.

Surface acidity study of Mn+-montmorillonite clay catalysts by FT-IR spectroscopy: Correlation with esterification activity

A simple method for evaluating the surface acidity of different cation-exchanged montmorillonite (mont) clay catalysts, Mn+-mont (Mn+=Al3+, Fe3+, Cr3+, Zn2+, Ni2+, Cu2+, and H+), involving treatment with pyridine is described. After treating with pyridine, the samples were heated at 120°C and the FT-IR spectra were directly recorded in the region 1650 and 1350cm−1. The data obtained show the presence of both Lewis and Brønsted acid sites. The activities of the catalysts to bring about Brønsted acid catalysed esterification of succinic acid with iso-butanol to yield di-(iso-butyl) succinate have been studied. The Brønsted acidity data obtained for Mn+-mont correlated well with activity in the esterification reaction. The activities of the catalysts were found to decrease in the order of exchange ions Al3+>Fe3+>Cr3+>Zn2+>Ni2+>Cu2+>Na+-mont. They also correlated well with the charge to radius ratio of the cations. The catalysts exchanged with trivalent cations showed stronger absorption bands attributed to Brønsted acidity (1540cm−1) whereas those exchanged with divalent cations showed an increased Lewis acidity (1450cm−1) and reduced Brønsted acidity along with charge to radius ratio. Zn2+-, Cu2+- and Ni2+-exchanged clays showed an additional peak around 1605cm−1 which is attributed to the pyridine adsorption on surface sites through its π electrons. The method suggested here to evaluate the acidity is suitable for active sites which are thermally unstable such as water molecules in the hydration shell of a cation in exchanged clay.

Liquid-phase Epoxidation of Alkenes Using Molecular Oxygen Catalyzed by Vanadium Cation-exchanged Montmorillonite

Abstract Vanadium cation-exchanged montmorillonite can efficiently catalyze the selective epoxidation of various alkenes and the oxygenation of adamantane using molecular oxygen as a sole oxidant.

Metal Cation-Exchanged Montmorillonite-Catalyzed Addition of Organic Disulfides to Alkenes

Abstract The addition of organic disulfides to alkenes, giving vic-bis(alkylthio)alkanes and vic-bis(arylthio)alkanes, proceeds in chlorobenzene in the presence of a catalytic amount of a variety of metal cation-exchanged montmorillonites (abbreviated as Mn+-monts), Al3+, Fe3+, Zr4+, and In3+ being effective as Mn+. The most effective Fe3+-mont can be reused for the addition of diphenyl disulfide to cyclohexene at least 8 times without an appreciable loss of catalytic activity.

Metal Cation‐Exchanged Montmorillonite (Mn+‐Mont)‐Catalyzed Friedel—Crafts Acylation of 1‐Methyl‐1‐cyclohexene and 1‐Trimethylsilyl‐1‐alkynes.

The acylation of 1-methyl-1-cyclohexene and 1-trimethylsilyl-1-alkynes with acyl chlorides has been investigated in the presence of a variety of metal cation-exchanged montmorillonites (abbreviated...

Metal Cation-Exchanged Montmorillonite (Mn+-Mont)-Catalyzed Friedel–Crafts Acylation of 1-Methyl-1-cyclohexene and 1-Trimethylsilyl-1-alkynes

Abstract The acylation of 1-methyl-1-cyclohexene and 1-trimethylsilyl-1-alkynes with acyl chlorides has been investigated in the presence of a variety of metal cation-exchanged montmorillonites (abbreviated as Mn+-monts), where the catalysts are recyclable for several times after simple washing.

The adsorption of valine on cation-exchanged montmorillonites

The interfacial reaction of valine was systematically studied on the surface of different cation-exchanged montmorillonites, namely calcium-, copper-, zinc-montmorillonite, and montmorillonite KSF. The exchanged cations were selected on the basis of stability of their valine complexes. At first the interfacial acid/base properties of cation exchanged montmorillonites were studied: the stability constants of the ion exchange processes on the layer charges were determined by radioisotopic labeling, the edge charges were studied by potentiometric titration and surface complexation model. The adsorption was studied as a function of valine concentration, pH and time. The results were evaluated by a surface complexation model and the possible surface complexes and their stability products were given. The results show what kind of interactions are possible in the ternary system of montmorillonite/valine/metal ions and how the metal ions can effect on these interactions. The assumed processes are: (1) the adsorption of valine in the interlayer space, where valine is adsorbed in protonated form, (2) the adsorption of valine on the protonated aluminol sites, and (3) the adsorption of positively charged complexes on the deprotonated silanol sites, if the exchangeable cation forms a positive complex with valine. The total amount of the adsorbed valine and the ratio of the different adsorption processes is determined by the affinity of metal ions to the layer charges and by the stability of the metal ion–valine complexes in solution.

Highly Efficient Deprotection of Acetals by Titanium Cation-exchanged Montmorillonite as a Strong Solid Acid Catalyst

Abstract Deprotection of various kinds of acetals sufficiently occured in the presence of Ti4+-exchanged montmorillonite as a recyclable strong solid acid catalyst.

Metal cation-exchanged montmorillonite catalyzed protection of aromatic aldehydes with Ac 2O

The protection of aromatic aldehydes with acetic anhydride was investigated in the presence of 26 metal cation-exchanged montmorillonites (M n+ -MMT) and commercial acid-activated K10 and KSF montmorillonites (Südchemie Moosburg, Germany). The acid sites of all catalysts were investigated by infrared spectroscopy and thermal analysis using pyridine as a molecular probe. The yield of reaction is roughly related to the strength of acid sites and depends also on the substitution on the benzene ring of the aldehydes. The order of activity of selected cation-exchanged forms was Al>K10∼KSF>Zn>Na which correlates well with the polarizing power of these cations and resulting acidity. Al 3+-MMT is revealed to be an effective catalyst for protection of aromatic aldehydes with Ac 2O and produces almost solely 1,1-diacetates. Relatively high yield of products observed for “moderately acid” cations, such as Zn 2+, can be explained by the fact that protection of aldehydes requires medium-strength acid sites.

Investigation of cation-exchanged montmorillonites by combined x-ray diffraction and positron annihilation lifetime spectroscopy

A characterization of some mineral and organophilic montmorillonites has been carried out using x-ray diffraction and positron annihilation lifetime spectroscopy. The combination of the two techniques supplies information on the microscopic structure of clays, in particular on the fraction of interlayer gap which is occupied by water molecules in the mineral clays. Nanocavities among cations of quaternary ammonium salts inserted in the organophilic clays were also investigated and compared with those existing in the free salt.

Highly efficient heterogeneous acetalization of carbonyl compounds catalyzed by a titanium cation-exchanged montmorillonite

The titanium cation-exchanged montmorillonite efficiently catalyzed the selective acetalization of various carbonyl compounds as a recyclable solid acid. This heterogeneous catalyst has an advantage of a strikingly simple workup procedure over conventional homogeneous acids.

Adsorption Study of Acetylacetone on Cation-Exchanged Montmorillonite by Infrared Spectroscopy

The adsorption of acetylacetone on layer silicates containing various cations has been studied by means of infrared spectroscopy, X-ray diffraction, and thermogravimetric analysis. An analysis of several split bands in the region of 1740−1520 cm-1 was made. The bands were attributed to the interaction of carbonyl with structural hydroxyl and cationic hydroxyl groups and were responsible for the formation of acetylacetonate complexes between enolic or anionic acetylacetone and metal cations in the silicate layers.

Metal cation-exchanged montmorillonite(M n+ -mont)-catalyzed reductive alkylation of phenol and 1-naphthol with cyclohexanones

The alkylation of phenol with cyclohexanone has been investigated in the presence of a variety of metal cation-exchanged montmorillonites (M n+ -monts; M n+ = Zr 4+, Al 3+, Fe 3+, Na +) and montmorillonite K10. Al 3+-mont is revealed to be an effective catalyst for alkylation of phenol with ketones. Al 3+-mont-catalyzed alkylation of phenol with 4-substituted-cyclohexanones produces almost solely trans-(4-alkylcyclohexyl)phenols, which are good starting materials for some liquid crystals. On the other hand, when a similar reaction is carried out with 1-naphthol instead of phenol in chlorobenzene as solvent, the products are tetrahydrobenzonaphthofuran derivatives and 2-(4-alkylcyclohexyl)-1-naphthols, the former being the major and Fe 3+-mont being the most effective catalyst.

Simple and clean synthesis of 9,9-bis[4-(2-hydroxyethoxy)phenyl]fluorene from the aromatic alkylation of phenoxyethanol with fluoren-9-one catalysed by titanium cation-exchanged montmorillonite

9,9-Bis[4-(2-hydroxyethoxy)phenyl]fluorene is simply obtained by the condensation of phenoxyethanol with fluoren-9-one using a Ti4+ cation-exchanged montmorillonite as a strong solid acid catalyst.

Complex Formation of Cation-Exchanged Montmorillonites with Propylene Carbonate: Osmotic Swelling in Aqueous Electrolyte Solutions

AbstractMontmorillonites saturated with Li+, Na+, K+, NH4+, Mg2+, Ca2+, Ba2+, or Ni2+ ions can form complexes with propylene carbonate (PC) by intercalation; the d(001) of montmorillonite expands to 19 Å. In the infrared absorption spectra of these complexes, the C=0 stretching band of the intercalated PC molecules shifts to lower frequencies, and the amount of the shift increased with the increase of the polarizing power of the interlayer cations. Water molecules were strongly bound to the cations. The PC molecules interacted with the cations by way of H2O molecules. With the removal of H2O, the PC molecules directly coordinate to the cations and the PC molecules show a much larger red-shift in the C=O frequency. The PC-montmorillonite complexes exhibited osmotic swelling, even in aqueous electrolyte solutions. This finding is interpreted in terms of the formation of thick electric double-layers consisting of PC and H2O between the 2:1 layers.

Use of the Second Derivative of TG Curves for Investigation of the Exchanged Interlayer Cation in Montmorillonite

Various cation-exchanged montmorillonites (Li+, Na+, Ba2+, Mg2+, Ca2+, Mn2+, Co2+, Cu2+, Ag+, Cd2+, Hg2+, Al3+, Pb2+ and NH4+) were prepared from calcium montmorillonite and their properties were studied by means of X-ray diffraction and thermal analysis. The two methods give information on the cation exchange in the interlayer space only. X-ray diffraction studies at room temperature are mainly suitable for estimation of the exchange of cations of different valencies. At 500°C, when the structure is completely collapsed, the d value of montmorillonite depends on the non-hydrated ionic radius of the interlayer cation, but the measurement interval is limited for fine interpretation. The thermoanalytical method is suitable for a better distinction of different exchangeable cations of higher hydration energy on the basis of the DTG or DDTG curve.

Cation-exchanged montmorillonite catalyzed hydration of styrene derivatives

Iron-exchanged Wyoming montmorillonite (Fe 3+-SWy-1) is quite an effective catalyst for the hydration of styrene derivatives. The yields and selectivities depend on the reaction conditions, with good efficiency attained using THF as solvent at 120°C. Fe 3+-SWy-1 calcined at 300°C, and pillared clays (PIL.Fe 3+-SWy-1), either air dried or calcined at 300°C, were inactive for the hydration of styrene. The hydration of styrene was also investigated in the presence of a cation-exchanged Fluka K10 montmorillonite (M n+-K10). Fe 3+-K10 was found to be the most effective catalyst. However, it shows less activity, selectivity and reproducibility than Fe 3+-SWy-1.

Metal cation-exchanged montmorillonite (Mn+-mont)-catalysed aromatic alkylation with aldehydes and ketones

The alkylation of aromatic compounds with aldehydes and ketones in the presence of a variety of metal cation-exchanged montmorillonites (Mn+-mont; Mn+ = Zr4+, Al3+, Fe3+, Zn2+, H+, Na+) has been investigated. Al3+- and Zr4+-Monts are revealed to be effective as catalysts, while no reaction takes place with Na+-mont. Al3+-Mont-catalysed alkylation of phenol with several aldehydes produces mainly or almost solely the corresponding gem-bis(hydroxyphenyl)alkanes (bisphenols) in good yields, while that with several ketones affords selectively the corresponding alkylphenols in moderate to good yields. The alkylation always occurs at the carbonyl carbon without any skeletal rearrangement and the kind of products depends much on the steric hindrance of an electrophilic intermediary carbocation. The alkylation of anisole, veratrole and p-cresol proceeds well, while that of toluene, benzene, chlorobenzene and nitrobenzene scarcely occurs.

Metal cation-exchanged montmorillonite(Mn+-Mont)-catalysed carbonyl-ene reactions

Metal cation-exchanged montmorillonite (M n+ -mont) works in acetonitrile at 80 °C as a Lewis acid catalyst for the intermolecular carbonyl-ene reaction of α-methylstyrenes with paraformaldehyde to give the corresponding homoallylic alcohols, Zr 4+ -mont being the most effective of the many M n+ -mont catalysts examined. Similarly, the catalyst is also useful for the highly stereoselective intramolecular cyclization of citronellals to afford isopulegols, the reaction being much faster. Regeneration of the catalyst is confirmed for Zr 4+ -mont, which can be effectively recycled at least five times.

Cation-Exchanged Montmorillonite (Mn+-Mont)-Catalyzed Prins Reaction

Abstract The Prins reaction of styrenes with paraformaldehyde or 1,3,5-trioxane in toluene in the presence of cation-exchanged montmorillonite (Mn+-mont), which worked as a Brønsted acid catalyst, at 80 °C produced 4-aryl-1,3-dioxanes selectively in up to 99% isolated yield with a turnover number of up to 5.9 × 102. Among the examined 21 Mn+-monts, Ce3+- and Fe3+-monts were revealed to be quite effective. Regeneration of the catalyst was confirmed with the Ce3+-mont, which could be effectively recycled at least three times. Many lanthanide metal ion-exchanged montmorillonites (Ln3+-monts) were prepared and characterized by X-ray powder diffraction (XRD) and temperature-programmed desorption of ammonia gas (NH3-TPD) methods.