Inorganic Solid Acids Research Articles

Efficient synthesis of N-substituted pyrroles catalyzed by a novel an organic–inorganic hybrid solid acid catalyst

A novel organic–inorganic hybrid solid acid [MIMBS]3PW12O40 has been successfully prepared. It showed high catalytic activity for N-substituted pyrroles through the cyclocondensation of primary amines with 1,4-dicarbonyl compounds. The solid acid catalyst is stable and can be easily recovered and reused without losing its activity in its efficiency. In addition, a plausible mechanism for the catalytic action of [MIMBS]3PW12O40 has been introduced.

Zr‐Containing Hybrid Organic–Inorganic Mesoporous Materials: Hydrophobic Acid Catalysts for Biodiesel Production.

AbstractZirconium‐containing periodic mesoporous organosilicas (Zr‐PMOs) with varying framework organic content have been synthesized through a direct synthesis method. These materials display the excellent textural properties of the analogous inorganic solid acid Zr‐SBA‐15 material. However, the substitution of silica by organosilicon species provides a strong hydrophobic character. This substitution leads to meaningful differences in the environment surrounding the zirconium metal sites, leading the modification of the catalytic properties of these materials. Although lower metal incorporation is accomplished in the final materials, leading to a lower population of metal sites, hydrophobisation leads to an impressive beneficial effect on the intrinsic catalytic activity of the zirconium sites in biodiesel production by esterification/transesterification of free fatty acid ‐containing feedstock. Moreover, the catalytic activity of the highly hybridised materials is hardly affected in presence of large amounts of water, confirming their very good water‐tolerance. This makes Zr‐PMO materials interesting catalysts for biodiesel production from highly acidic water‐containing feedstock.

ChemInform Abstract: Catalytic Conversion of Lignocellulosic Biomass to Fine Chemicals and Fuels

AbstractReview: 235 refs.

A Simple and Fast Method for Protection of Aldehydes as 1,1-Diacetates Using Cerium(IV) Sulfate as an Efficient and Reusable Inorganic Catalyst

A simple, green, and very fast method for protection of aryl aldehydes as 1,1-diacetates promoted by cerium(IV) sulfate tetrahydrate, Ce(SO4)2·4H2O, as a novel inorganic solid acid catalyst at room temperature and under solvent-free conditions is described. The present methodology offers several advantages, such as a simple procedure with an easy workup, very short reaction times, high yields, and the absence of any volatile and hazardous organic solvents.

Solid Acids as Heterogeneous Support for Primary Amino Acid‐Derived Diamines in Direct Asymmetric Aldol Reactions

AbstractWe have achieved the non‐covalent immobilization of chiral primary amino acid‐derived diamines on organic and inorganic sulfonated solid acids through acid‐base interaction. With the commercial sulfonated fluoropolymer nafion® NR50 as support an optimal balance was found between activity and stereoselectivity of the supported catalyst in direct asymmetric aldol reactions of linear ketones and aromatic aldehydes. Under optimized conditions aldol products were obtained in high yields and with excellent enantioselectivities for the syn‐product (up to 98% ee). Furthermore, catalysis with the supported diamine was demonstrated to occur truly heterogeneously and the loaded nafion® NR50 beads could be reused several times. Ultimately, the immobilized catalyst/nafion® NR50 system was successfully implemented in a fixed‐bed reactor set‐up under continuous flow conditions.

Efficient Conversion of Furfuryl Alcohol into Alkyl Levulinates Catalyzed by an Organic–Inorganic Hybrid Solid Acid Catalyst

A clean, facile, and environment-friendly catalytic method has been developed for the conversion of furfuryl alcohol into alkyl levulinates making use of the novel solid catalyst methylimidazolebutylsulfate phosphotungstate ([MIMBS]₃PW₁₂O₄₀). The solid catalyst is an organic-inorganic hybrid material, which consists of an organic cation and an inorganic anion. A study for optimizing the reaction conditions such as the reaction time, the temperature and the catalyst loading has been performed. Under optimal conditions, a high n-butyl levulinate yield of up to 93 % is obtained. Furthermore, the kinetics of the reaction pathways and the mechanism for the alcoholysis of furfuryl alcohol are discussed. This method is environmentally benign and economical for the conversion of biomass-based derivatives into fine chemicals.

Automated Protein Hydrolysis Delivering Sample to a Solid Acid Catalyst for Amino Acid Analysis

In this study, we developed an automatic protein hydrolysis system using strong cation-exchange resins as solid acid catalysts. Examining several kinds of inorganic solid acids and cation-exchange resins, we found that a few cation-exchange resins worked as acid catalysts for protein hydrolysis when heated in the presence of water. The most efficient resin yielded amounts of amino acids that were over 70% of those recovered after conventional hydrolysis with hydrochloric acid and resulted in amino acid compositions matching the theoretical values. The solid-acid hydrolysis was automated by packing the resin into columns, combining the columns with a high-performance liquid chromatography system, and heating them. The amino acids that constitute a protein can thereby be determined, minimizing contamination from the environment.

ChemInform Abstract: Hydrosilylation of Carbonyl Compounds Catalyzed by Solid Acids and Bases.

Abstract Hydrosilylation of carbonyl compounds with hydrosilane is efficiently catalyzed by inorganic solid acids and bases such as Fe 3+ ion-exchanged montmorillonite and hydroxyapatite (Ca 10 (PO 4 ) 6 (OH) 2 ) at reaction temperatures between 25 and 90 °C. Enones are also selectively hydrosilylated in the presence of hydroxyapatite to afford the corresponding 1,2-addition products in high yields.

Composite electrolytes composed of Cs-substituted phosphotungstic acid and sulfonated poly(ether–ether ketone) for fuel cell systems

Abstract Composite electrolytes composed of cesium hydrogen sulfate containing phosphotungstic acids (CsHSO 4 –H 3 PW 12 O 40 ) and sulfonated poly(ether–ether ketone) (SPEEK) were prepared by casting the corresponding precursor for application in fuel cells. Partially Cs-substituted phosphotungstic acids (Cs x H 3− x PW 12 O 40 ) were formed in the CsHSO 4 –H 3 PW 12 O 40 system by mechanochemical treatment. SPEEK was prepared from PEEK by sulfonation using concentrated sulfuric acid. Flexible composite electrolytes were obtained and their electrochemical properties were markedly improved with the addition of Cs x H 3− x PW 12 O 40 , into the SPEEK matrix. A maximum power density of 213 mW cm −2 was obtained from the single cell test for 50H 3 PW 12 O 40 –50CsHSO 4 in SPEEK (1/5 by weight) composite electrolyte at 80 °C and at 80 RH%. Electrochemical properties and transmission electron microscopy (TEM) results suggest that three-dimensional cluster particles were formed and homogeneously distributed in the SPEEK matrix. The mechanochemically synthesized Cs x H 3− x PW 12 O 40 incorporated into the SPEEK matrix increased the number of protonate sites in the electrolyte. The composite electrolytes were successfully formed with Cs x H 3− x PW 12 O 40 , which consist of hydrogen bonding between surface of inorganic solid acids and not only –HSO 4 − dissociated from CsHSO 4 but also –SO 3 H groups in the SPEEK.

Ionogel electrolytes at medium temperatures by composite of ionic liquids with proton conducting cesium hydrogen sulfate

Ionogel electrolytes at medium temperatures were prepared by composite of ionic liquid [1-butyl-3-methylimidazole][bis-(fluoromethanesulfonyl) amide] ([BMIM][TFSI]) with the proton-conducting inorganic solid acid CsHSO 4. The incorporation of only 10 wt.% of the ionic liquid into the solid acids drastically increased the conductivity of solid acids over a wide temperature range. The ionogel electrolytes contained up to 40 wt.% of the ionic liquid within their inorganic CsHSO 4 networks and had an ion conductivity of 2 × 10 − 2 S/cm.

Insight into Friedel-Crafts acylation of 1,4-dimethoxybenzene to 2,5-dimethoxyacetophenone catalysed by solid acids—mechanism, kinetics and remedies for deactivation

Friedel-Crafts acylation of aromatic ethers is challenging, which frequently encounters rapid catalyst deactivation by the ether. Although H-Y and H-β are known to perform better, there is still deactivation due to both the ether and the acylated ether. In the current work, the synthesis of 2,5-dimethoxyacetophenone, an intermediate used in the production of fine chemicals, was carried out via acylation of 1,4-dimethoxybenzene with acetic anhydride over various solid acid catalysts such as sulfated zirconia, UDCaT-1, UDCaT-5, 20% w/w H 3P 12W 40/K10, 20% w/w Cs 2.5H 0.5P 12W 40/K10, Amberlyst-15 and Indion-125. The cation exchange resins, Amberlyst-15 and Indion-125, were superior to other inorganic solid acids. A systematic study was undertaken to understand the reaction mechanism and catalyst functioning with Indion-125. The catalyst gets deactivated slowly over repeated use and this was studied independently. The adsorption of reactants and products was studied from pure component solutions and mixtures. The experimental data so generated were used to develop a model, incorporating deactivation. The model fits the experimental data very well. The current work gives an insight into choice of catalyst, kinetic modeling, studies in catalyst deactivation and methods to avoid deactivation.

Tungstate Sulfuric Acid (TSA)/ KMnO4 as a Novel Heterogeneous System for Rapid Deoximation

Neat chlorosulfonic acid reacts with anhydrous sodium tungstate to give tungstate sulfuric acid (TSA), a new dibasic inorganic solid acid in which two sulfuric acid molecules connect to a tungstate moiety via a covalent bond. A variety of oximes were oxidized to their parent carbonyl compounds under mild conditions with excellent yields in short times by a heterogeneous wet TSA/KMnO4 in dichloromethane system.

Selectivity Engineering of Cation-Exchange Resins over Inorganic Solid Acids in C-Alkylation of Guaiacol with Cyclohexene

Friedel−Crafts alkylation of guaiacol with cyclohexene gives both C- and O-alkylated products, which are commercially valuable. The C-alkylated products are important intermediates for the production of resins, antioxidants, drugs, dyes, polymer additives, agrochemicals, and antiseptic substances. The objective of the current work was to achieve maximum selectivity for the C-alkylated products, using an active catalyst with minimum separation cost. A variety of eco-friendly solid acid catalysts such as sulfated zirconia, Amberlyst-15, Filtrol-24, cesium-modified dodecatungstophosphoric acid (Cs-DTP) supported over K-10 clay (20% w/w Cs2.5H0.5PW12O40/K-10), and 20% w/w dodecatungstophosphoric acid (DTP)/K-10 clay were screened to study the effect of their nature of acidity on product distribution. Amberlyst-15 was determined to be the best catalyst to achieve maximum selectivity for C-alkylated product at 80 °C. The O-alkylation versus C-alkylation not only was observed to be highly temperature sensitive, but the nature of the acidic sites also had an important role. Effects of various parameters on rates and product distribution are discussed to deduce the kinetics of the reaction.

Tungstate Sulfuric Acid (TSA)/NaNO2 as a Novel Heterogeneous System for the N‐Nitrosation of Secondary Amines under Mild Conditions.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Tungstate Sulfuric Acid (TSA) /NaNO2as a Novel Heterogeneous System for the N-Nitrosation of Secondary Amines under Mild Conditions

Nitrosation chemistry has been introduced as an active area for organic and biological chemists. Their strong mutagenic and carcinogenic properties of N-nitrosamines have caused considerable attraction in this view. Also they have been used as pesticides, lubricant and antioxidants. NNitrosamines have key role in preparation of various N, Nbonded functionalities and their easy lithiation followed by denitrosative electrophilic reaction which can be applied for the electrophilic substitution of secondary amines at the aposition. In situ generated HNO2 from sodium nitrite and inorganic acids in water or water/alcohol mixture solvent, is the most general reagent for nitrosation. Some other nitrosating agents, such as fermy's salt, N-haloamides/ NaNO2 under phase-transfer conditions, 5 nitrogen tetroxide, oxyhyponitrite and oxalic acide have been reported. Recently, several heterogeneous reagent systems using Nafion-H, silica sulfuric acid and trichloroisocyanuric acid in combination with NaNO2 have also been used. Today, heterogenation of chemical systems is an active field in industrial and laboratorial chemistry because of simplification in handling procedures, reduction of corrosion, green chemistry point of view, avoidance of byproducts, easy and clean reaction and simple work-up. With regard to wide application of acids as reagent or catalyst in organic chemistry, (for producing more than 1 × 10 mt/year of products) introduction of a new inorganic solid acid can be useful in this direction. Recently silica sulfuric acid and Nafion-H have been used for a wide variety of reactions such as production of disulfides from thiols, oxidation of 1,4-dihydropyridines, N-nitrosation of secondary amines,

Adsorption of Polymers on Inorganic Solid Acids Investigated by Means of Coadsorbed Solvatochromic Probes

The adsorption of five different synthetic polymers, namely, polystyrene (PS), poly(methyl methacrylate) (PMMA), poly(ethylene oxide) (PEO), poly(4-vinylpyridine) (PVPy), and poly(N-vinylpyrrolidone) (PVP) in a 1,2-dichloroethane or dichloromethane slurry has been studied by measuring the UV/vis spectra of coadsorbed solvatochromic probes. Fe(phen)2(CN)2 [cis-dicyano-bis-(1,10)-phenanthroline-iron(II), (1)] and Michler's ketone [4,4‘-bis(N,N-dimethylamino)-benzophenone, (2)] were used as solvatochromic surface polarity indicators. The UV/vis transmission spectra of the two surface polarity indicators 1 and 2 adsorbed on silica and alumina, respectively, were measured as a function of the adsorption time of the coadsorbed polymer in slurries in dichloromethane or 1,2-dichloroethane. Kamlet−Taft's α (hydrogen-bond acidity) parameter of the polymer/solid acid interfaces has been calculated using the linear function of υmax(1) with α of solid acids after Spange, S.; Vilsmeier, E.; Zimmermann, Y. J. Phys. Chem...

Hybrid Materials Approach In The Design Of Electrodes And Electrolytes For Energy Storage And Conversion

ABSTRACTThe integration of electro-ionically active inorganic species in polymer matrices allows for the design of either electrode or electrolyte materials depending on the conducting or insulating properties of the polymer used. Conducting polymers can be used as the basis for a variety of hybrid electrode systems, whereas other polymers such as polybenzimidazoles have been used as electrolyte membranes by themselves or in combination with inorganic solid acids. We will discuss the general approach of hybrid design with this in mind and specifically we will describe our recent results on the use of polyoxometalate-containing hybrids in energy storage and conversion devices. In this respect we have worked in our laboratory on electrochemical supercapacitors and fuel cells but emphasis should be made on the broader potential fields of application of this type of materials.

Solvent Influence on the Catalytic Activity and Surface Polarity of Inorganic Solid Acids

The surface-mediated hydride-transfer reaction of 1,4-cyclohexadiene with triphenylmethylium induced by two silicas, an alumina, and an aluminosilicate as solid acid catalyst, respectively, has been kinetically studied as a function of the polarity of the surrounding solvent. The specific rate constants k‘ have been determined in 10 different solvents. Generally, k‘ decreases with increasing polarity of the solvent. Kamlet−Taft's α (hydrogen-bond acidity) and π* (dipolarity/polarizability) parameters of the solid acid/solvent interface have been determined for alumina and aluminosilicate in various solvents. Fe(phen)2(CN)2 [cis-dicyanobis(1,10-phenanthroline)iron(II), (1)] and Michler's ketone [4,4‘-bis(N,N-dimethylamino)benzophenone, (2)] were used as solvatochromic surface polarity indicators. The UV/vis spectra of the two surface polarity indicators 1 and 2 adsorbed on solid acid catalysts from the solvents were measured by the reflection mode and the UV/vis absorption maxima were used to calculate the...

Polystyrene-Bound Tetrafluorophenylbis(triflyl)methane as an Organic-Solvent-Swellable and Strong Brønsted Acid Catalyst The authors thank Mr. Shoichi Kondo for the single-crystal X-ray analysis. Sodium triflate was generously donated by Central Glass Co., Ltd., Japan. The authors also acknowledge Dr. Yuko Wasada and Dr. Manabu Kubota for their helpful discussions on the theoretical calculations.

Several advantages over inorganic solid acids such as zeolites and perfluororesinsulfonic acids such as Nafion are offered by the new reusable polystyrene-bound catalyst 1: a broader range of applications, improved yields, improved selectivity, and milder reaction conditions. Tf = F3 CSO2 .

Solid acid catalysts for converting alkenes and alkanols to carboxylic acids

Tertiary carboxylic acids are presently manufactured by hydrocarboxylation of branched alkenes in the presence of CO, water and a corrosive homogeneous acid. Acidic ion-exchange resins also catalyse the hydrocarboxylation reaction when operated under specific conditions. Critical factors are the use of a moderately polar, non-basic solvent and the maintenance of a very low alkanol or alkene/water concentration in the reactor. Consistently, very good performances were achieved when using the carboxylic acid product as solvent and operating the reaction in a continuous stirred tank reactor (CSTR). The best resins included the Nafion NR50 as well as styrene-based sulphonated resins with high content of acid sites (>4.5 mmol/g) and moderate divinyl-benzene content (8–12%), such as the Amberlyst 15 and 36. By contrast, inorganic solid acids, such as zeolites, sulphated zirconia or heteropoly acids showed marginal activity.