Strong Solid Acid Catalyst Research Articles

Hydrothermally synthesized poorly-crystalline binary oxides with ZrW2O8 composition: preparation, structural analysis, and catalytic activity for the alkylation of anisole with benzyl alcohol.

Hydrothermally synthesized poorly-crystalline metastable Zr–W binary hydroxide (W/Zr = 2), after calcination, was confirmed to be a strong solid acid catalyst to promote the alkylation of anisole with benzyl alcohol. The preparation conditions, structure of the as-prepared catalysts and the calcined hydroxides were investigated using XRD, nitrogen adsorption isotherms, TG-DTA, and XANES/EXAFS techniques. The crystalline phase was controlled by the hydrochloric acid concentration used for preparing a mother gel, and 5–9 M HCl was suitable for preparing the active phase. The tungsten species exists as a six-valent WO6 distorted octahedron connected with the ZrO7 unit via corner-sharing linkages. The incompleteness of the network structure is suggested to be responsible for the solid acidity.

Hercynite silica sulfuric acid: a novel inorganic sulfurous solid acid catalyst for one-pot cascade organic transformations.

Herein, we delignated the synthesis of a novel inorganic sulfurous magnetic solid acid catalyst by the immobilization of an extremely high content of sulfuric acid functionalities on the amorphous silica-modified hercynite nanomagnetic core–shell via a simple method. Silica sulfuric acid (SSA) modified hercynite nanocomposite (hercynite@SSA) combines excellent recoverability and stability characteristics of hercynite (which can be regarded as a ferro spinel with Fd3m space group and cubic crystal structure) with the strong Brønsted acid properties of –SO3H groups. This nanomagnetic solid acid was found to be an efficient and facile strong solid acid catalyst for the synthesis of bis(pyrazolyl)methanes via two different one-pot multicomponent methodologies under green conditions. The hercynite@SSA catalyst shows excellent catalytic activity and reusability in the ethanolic medium among different solid acid materials. A plausible reaction mechanism is proposed for this synthesis.

Single‐Pot Alcoholysis of Furfuryl Alcohol to Alkyl Levulinates Using Heterogenized p‐TSA Catalyst**

AbstractSynthesis of levulinate esters which are known to be excellent sustainable fuel additives, was achieved by alcoholysis of furfuryl alcohol over strong solid acid catalyst, prepared by copolymerization of p‐toluenesulfonic acid with paraformaldehyde. Our catalyst possessed Brønsted acidity (3 mmol/g) with an excellent stability up to 220 °C. XPS, FT‐IR and Pyridine‐IR along with microanalysis studies confirmed the presence of terminal −SO3H functional groups responsible for Brønsted acidity in the catalyst. The catalyst was found to efficiently catalyze the alcoholysis of furfuryl alcohol to give alkyl levulinates under mild reaction conditions. The complete conversion of furfuryl alcohol with 96 % and 97 % selectivities to ethyl and butyl levulinates could be achieved using ethanol and butanol, respectively. Detailed study on effect of various reaction parameters like catalyst loading, reaction time and reaction temperature on conversion and product distribution was also carried out for the ethanolysis of furfuryl alcohol to ethyl levulinate. The catalyst could be easily recovered and recycled for five times successfully, with no loss in its original activity.

Strong Lewis acidic catalysts for C–F bond activation by fluorination of activated γ-Al2O3

A strong solid Lewis acid catalyst has been successfully obtained by modifying a known procedure of fluorinating γ-aluminium oxide, which was pre-calcined under vacuum.

Solid Sulfamic acid Catalyst for Glucose Production

Silica from rice husk ash was immobilized with sulfamic acid to form strong solid acid catalyst labeled as RHANS (RH = Rice Husk). The spectroscopic evidence confirms that the sulfamic acid was heterogenized onto silica. The XPS with the elemental analysis shows the presence of C, N, S, O, and Si onto RHANS. The FT-IR spectra supported both XPS and elemental analysis via showing the presence of NH2, SO2, CH2, and Si-O-Si functional groups which include the elements showing by XPS and elemental analysis. The RHANS had 139 m2 g−1 as a specific surface area with thermal stability reached to 252°C according to the TGA. The AFM, TEM and SEM showed that the RHANS had nano shape. The RHANS was efficient catalyst for cellulose hydrolysis to glucose. Approximately 96% of glucose was formed with in 2 h at 140°C over RHANS. The repeatable catalyst was stable during the cellulose hydrolysis without a significant loss of its catalytic activity.

Sulfonic acid-functionalized polyallylamine (sevelamer) as an efficient reusable strong solid acid catalyst for the synthesis of xanthenes derivatives

Sevelamer (polyallyamine resin)-supported sulfonic acid (S-SO3H) has been prepared from the reaction of sevelamer with chlorosulfonic acid and characterized using FT-IR spectroscopy, scanning electronmicroscopy (SEM) and thermogravimetric analysis (TGA). The catalytic activity of S-SO3H was investigated in the synthesis of 1,8-dioxo-octahydroxanthene derivatives. All of the reactions were fast and gave excellent yields. The catalyst was easily recovered and reused for 5 runs without significant loss of its catalytic activity.

Synthesis and characterization of zirconia-based catalyst for the isomerization of n-hexane

ABSTRACTSulfated zirconia is a very strong solid acid catalyst which can be utilized for various reactions. The present study focuses on synthesis of zirconia-based catalyst with high acidity and high surface area, particularly for isomerization reaction. Sulfated zirconia has been obtained by sulfation of zirconia prepared by hydrothermal route. The catalyst was developed by impregnating tungstophosphoric acid on sulfated zirconia by wet incipient method. The catalyst was characterized through Brunauer–Emmett–Teller (BET) surface area, temperature-programmed desorption of ammonia, temperature program reduction of hydrogen, Fourier transmission infrared spectroscopy, and thermogravimetric analysis. The results revealed that the catalyst is crystalline in nature with surface area 190–225 m2 g−1 and acidity 0.135–0.558 mmol g−1. Twenty-five percent conversion was obtained (as confirmed by gas chromatography) at 225°C using n-hexane as model hydrocarbon in fixed-bed microreactor.

A New Type of Magnetically-Recoverable Heteropolyacid Nanocatalyst Supported on Zirconia-Encapsulated Fe3O4 Nanoparticles as a Stable and Strong Solid Acid for Multicomponent Reactions

A novel highly efficient magnetically retrievable catalyst was developed by the immobilization of H3PW12O40 (20–60 wt%) on the surface of zirconia-encapsulated Fe3O4 nanoparticles. The prepared HPW supported on nano-Fe3O4@ZrO2 heterogeneous acid catalyst (or n-Fe3O4@ZrO2/HPW) was fully characterized by several physicochemical techniques such as: Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, vibrating sample magnetometry and thermogravimetric analysis. The FT-IR spectroscopic data revealed that H3PW12O40 molecules on the nano-Fe3O4@ZrO2 support existed in the Keggin structure. The acidity of the catalyst was measured by the help of a potentiometric titration with n-butylamine. It was surprising that this very strong solid acid catalyst exhibited an excellent acid strength which was as a result of possessing a higher number of surface active sites compared to its homogeneous analogues. The catalytic activity of the as-prepared novel nano-Fe3O4@ZrO2/HPW was explored through the one-pot three-component synthesis of different 3,4-dihydropyrimidin-2(1H)-ones (i.e. Biginelli reaction) and 1,4-dihydropyridines (i.e. Hantzsh reaction) under solvent free condition. The sample of 40 wt% showed higher acidity and activity in the catalytic transformation. After the reaction, the catalyst/product isolation could be easily achieved with an external magnetic field and the catalyst could be easily recycled for at least five times without any decrease in its high catalytic activity. The excellent recyclability was attributed to the strong interaction between the hydroxyl groups of the nano-Fe3O4@ZrO2 support and the HPW species.

Generation of Strong Acid Sites on Yttrium-Doped Tetragonal ZrO2-Supported Tungsten Oxides: Effects of Dopant Amounts on Acidity, Crystalline Phase, Kinds of Tungsten Species, and Their Dispersion

A tungsten oxide catalysts supported on yttrium- or ytterbium-doped crystalline zirconium oxide (WOx/Y(Yb)-ZrO2) with different dopant concentrations but the same tungsten loadings and calcination temperatures were prepared to investigate the mechanism responsible for the strong solid acidity of so-called tungstated zirconia. The surface acid–base properties of WOx/Y(Yb)-ZrO2 and the support were characterized by catalyses of n-butane skeletal isomerization, alkylation of anisole with benzyl alcohol, and 2-butanol decomposition. The structural characterization and quantitative analysis were conducted by XRD, XAFS, and UV–Vis techniques. Crystalline zirconium oxides were effective as the starting material for tungsten–zirconium-based strong solid acid catalysts instead of amorphous Zr(OH)x if the crystalline form was tetragonal. Tetragonal-phase Y(Yb)-ZrO2 substitutional solid solutions with dopant concentrations of 3–5 mol % was a suitable support for stabilization of active small WO3 clusters. Tungsten species aggregated to form inactive large WO3 particles on the monoclinic ZrO2 polymorph with Y-dopant amount less than 2 mol % even though the surface density of tungsten species and calcination temperature were the same as those for the active catalysts. Inactive yttrium–tungsten binary oxides formed when the yttrium doping level exceeded 10 mol %. Intrinsic role of crystalline phase of tetragonal zirconia on generating the strong solid acidity is confirmed to stabilize WO3 small clusters without aggregation.

Catalytic Conversion of Biomass-derived Carbohydrates into 5-Hydroxymethylfurfural using a Strong Solid Acid Catalyst in Aqueous γ-Valerolactone

Selective conversion of biomass-derived carbohydrates into 5-hydroxy-methylfurfural (HMF) is of great significance for biomass conversion. In this study, a novel solid Bronsted acid was prepared simply by the copolymerization of paraformaldehyde and p-toluenesulfonic acid and then used to catalyze the conversion of various carbohydrates into HMF in γ-valerolactone-water (GVL/H2O) reaction medium for the first time. The catalyst exhibited strong acidity, good water resistance, and high thermal stability. The present work focuses on the effects of various reaction parameters, including reaction temperature, time, water concentration, solvent, fructose level, and catalyst loading, on fructose dehydration. The catalyst exhibited excellent catalytic performance for HMF production from fructose in GVL and furnished a high HMF yield of 78.1% at 130 °C in 30 min. The recycling experiments suggested that the solid acid catalyst could be recycled at least seven times without a noticeable decrease in the catalytic activity. In addition, an attempt to study the one-step conversion of sucrose, glucose, and cellulose into HMF and furfural was performed using the same catalytic system.

Formation of Subnanometer Zr-WOx Clusters within Mesoporous W–Zr Mixed Oxides as Strong Solid Acid Catalysts for Friedel–Crafts Alkylation

WO3-ZrO2 mixed metal oxides is an important class of acid solid. Here, we successfully synthesized a variety of mesoporous WO3-ZrO2 mixed metal oxides by a well-controlled sol-gel process (AcHE) using Zr(OBu)(4) and WCl6 as the inorganic precursors in the presence of poly block copolymer F127. Their structures and acid properties have been well characterized by XRD, Raman, N-2 adsorption measurement, and HRTEM analyses. In addition, new insights from TG-DSC and P-31 NMR characterization also provide useful information on the formation of strong acidity of this important solid acid. Moreover, their structure-to-properties relationship has been studied in the Friedel-Crafts (F-C) reaction of anisole and benzyl alcohol. We identified that the subnanometer WOx clusters act as the most active sites for the F-C reaction. Most importantly, we show that the formation of these subnanometer WOx clusters can be rationally controlled. It is shown that a minimum W concentration (0.07 at the calcination temperature of 800 degrees C) and a minimum calcination temperature (650 degrees C at a given W concentration of 0.1) are required during the preparation of these acid catalysts for the development of highly active subnano WOx clusters.

Catalytic conversion of bio-oil to oxygen-containing fuels by simultaneous reactions with 1-butanol and 1-octene over solid acids: Model compound studies and reaction pathways

Upgrading bio-oil by addition reactions across olefins represents a route to refine bio-oil to combustible and stable oxygen-containing fuels. Development and application of highly active strong solid acid catalysts with good hydrothermal stability has become a key determinant for success, because bio-oil’s complexity includes large amounts of water. Temperatures of 120°C or more are needed for satisfactory kinetics. Batch upgrading of a model bio-oil (phenol/water/acetic acid/acetaldehyde/hydroxyacetone/d-glucose/2-hydroxymethylfuran) over five water-tolerant solid acid catalysts (Dowex50WX2, Amberlyst15, Amberlyst36, silica sulfuric acid (SSA) and Cs2.5H0.5PW12O40 supported on K-10 clay (Cs2.5/K-10, 30wt.%)) with 1-octene/1-butanol were studied at 120°C/3h. SSA, ▪, exhibited the highest water tolerance and activity. Upgrading using olefin/1-butanol is complex, involving many simultaneous competing esterification, etherification, olefin hydration, phenol alkylation, aldol condensation, sugar dehydration etc. reactions.

H5CoW12O40 supported on nano silica from rice husk ash: A green bifunctional catalyst for the reaction of alcohols with cyclic and acyclic 1,3-dicarbonyl compounds

Rice husk ash (RHA) is an abundant agricultural by-product. The present research work deals with the production of nano silica powders, with high surface area and in amorphous form, from RHA using optimized technique. 12-Tungestocobaltic acid, H5CoW12O40 (CoW), was supported on silica from RHA to produce silica supported CoW (CoW/NSiO2) as a nano catalyst. The characterization data derived from FT-IR reveal that the Keggin structure of CoW remains intact in CoW/NSiO2. TEM image showed that the catalyst had spherical shape with an average particle size of 10nm. The acidity of the catalyst was measured by potentiometric titration with n-butylamine. To our surprise, this very strong solid acid catalyst showed an excellent distribution of acid sites, suggesting that the catalyst possesses a higher number of surface active sites compared to CoW supported on commercial silica (CoW/SiO2), CoW and K5CoW12O40. A high catalytic activity was found over CoW/NSiO2. Finally, CoW/NSiO2 has been used as a highly effective catalyst for benzylation of linear 1,3-dicarbonyl compounds with benzylic alcohols and synthesis of β-keto enol ethers from cyclic 1,3-dicarbonyl compounds. The present methodology offers a practical, simple, mild, environmentally friendly, and timesaving method under solvent-free conditions.

ChemInform Abstract: H3PW12O40 Supported on Silica‐Encapsulated γ‐Fe2O3 Nanoparticles: A Novel Magnetically‐Recoverable Catalyst for Three‐Component Mannich‐Type Reactions in Water.

AbstractThe separation of the catalyst is achieved by magnetism.

H3PW12O40 supported on silica-encapsulated γ-Fe2O3 nanoparticles: a novel magnetically-recoverable catalyst for three-component Mannich-type reactions in water

A new type of magnetically-recoverable catalyst was synthesized by the immobilization of H3PW12O40 on the surface of silica-encapsulated γ-Fe2O3 nanoparticles. This catalyst was characterized by transmission electron microscopy (TEM), a laser particle size analyzer, infrared spectroscopy (IR) and inductively coupled plasma atomic emission spectroscopy (ICP-AES). The results show that the particles are mostly spherical in shape and have an average size of approximately 94 nm. The characterization data derived from IR spectroscopy reveal that H3PW12O40 on the support exists in the Keggin structure. The acidity of the catalyst was measured by a potentiometric titration with n-butylamine. To our surprise, this very strong solid acid catalyst showed an excellent distribution of acid sites, suggesting that the catalyst possesses a higher number of surface active sites compared to its homogeneous analogues. The activity of the catalyst was probed through one-pot three-component Mannich-type reactions of aldehydes, amines and ketones in water at room temperature. The excellent conversions show that the catalyst has strong and sufficient acidic sites, which are responsible for its catalytic performance. After the reaction, the catalyst/product separation could be easily achieved with an external magnetic field, and more than 95% of the catalyst could usually be recovered. The catalyst was reused at least five times without any loss of its high catalytic activity.

Synthesis and Characterization of Mesoporous Ta−W Oxides as Strong Solid Acid Catalysts

Several mesoporous TaxW10−x mixed oxides prepared from TaCl5 and WCl6 in the presence of poly block copolymer surfactant Pluronic P-123 were examined as potential solid acid catalysts. Amorphous wormhole-type mesopores were observed in samples with x values from 3 to 10, whereas W-rich samples (x = 0−2) formed nonmesoporous structures with crystallized tungsten oxide (WO3). The acid strength increased with addition of W for mesoporous TaxW10−x oxides, and mesoporous Ta3W7 oxide exhibited the highest acid catalytic activity for the Friedel−Crafts alkylation of anisole and the hydrolysis of disaccharides. The results are compared with those of nonporous Ta2O5−WO3, HTaWO6 nanosheets, which were a solid acid obtained by exfoliation and aggregation of layered HTaWO6 with strong Brønsted acid sites in the interlayer, and a range of conventional solid acid catalysts. Mesoporous Ta−W oxides exhibited a turnover rate higher than that of nonporous Ta2O5−WO3 and HTaWO6 nanosheets, indicating that the mesoporous structure is an advantageous environment for the strong acid sites, because of the high surface area and easy reactant accessibility.

Layered and nanosheet tantalum molybdate as strong solid acid catalysts

Layered and nanosheet aggregates of HTaMoO 6 were examined as solid acid catalysts. The HTaMoO 6 aggregated nanosheets were formed by soft chemical processing of layered HTaMoO 6 using tetra ( n-butylammonium) hydroxide. The catalytic activity and acid properties of the HTaMoO 6 compounds were compared with those of layered HNbMoO 6 and a range of conventional solid acids. The catalytic activity of HTaMoO 6 for Friedel–Crafts alkylation with benzyl alcohol, hydrolysis of disaccharides, and esterification of acetic acid and lactic acid increased after exfoliation and aggregation, consistent with the acid strengths determined by NH 3 temperature-programmed desorption and 31P magic-angle spinning nuclear magnetic resonance spectroscopy measurements. HTaMoO 6 nanosheets possess additional strong acid sites on the oxide formed by exposure of a single layer, along with strong acid sites within the interlayer of the layered aggregate structure, resulting in higher acid catalytic activity than that of the original layered oxide.

Highly Efficient Synthesis of 14-Aryl-14H-dibenzo[a,j]xanthenes Catalyzed by Carbon-Based Solid Acid Under Solvent-Free Conditions

Carbon-based solid acid, a strong solid acid catalyst, was prepared readily by sulfonation and carbonization of aromatic compounds such as naphthalene in sulfuric acid at 250°C. This reusable and ecofriendly carbon-based solid acid highly efficiently condensed β-naphtol with aromatic aldehydes under solvent-free conditions, and the corresponding aryl-14-H-dibenzo[a,j]xanthenes were obtained in excellent yields. The catalyst can be reused several times without loss of its activity.

Efficient Utilization of Nanospace of Layered Transition Metal Oxide HNbMoO6as a Strong, Water-Tolerant Solid Acid Catalyst

Layered HNbMoO6 was found to function as a strong solid acid catalyst, exceeding the activity of zeolites and ion-exchange resins for Friedel-Crafts alkylation. HNbMoO6 also exhibited high catalytic activity for esterification of hydrocarboxylic acid and hydration. The catalytic performance of layered HNbMoO6 is attributed to the intercalation of reactants into the interlayer and the development of strong acidity.

ChemInform Abstract: Synthesis of a Novel Carbon Based Acid Catalyst and Its Catalytic Activity for the Acetalization and Ketalization.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.