Efficient Heterogeneous Acid Catalyst Research Articles

Efficient cenosphere supported catalyst for the esterification of n-octanol with acetic acid

An efficient heterogeneous acid catalyst was developed using cenospheres, a byproduct of coal-fired thermal power plants by the method of wet impregnation. Catalyst characterization was carried out using various analytical techniques, namely, Fourier transform infrared, X-ray diffraction, field emission gun scanning electron microscopy and Brunauer–Emmett–Teller surface area and surface acidity analysis. The characterization revealed the excellent catalytic activity of the catalyst for the esterification reaction of n -octanol and acetic acid. Various reaction parameters, namely, catalyst loading, a molar ratio of alcohol/acid and reaction temperature were evaluated and optimized by response surface methodology using the Box–Behnken model. The response surface methodology model equations corresponding to the conversion of acid and % yield of ester were developed. The model well predicted the optimal reaction conditions, which were validated experimentally with good agreement. The excellent catalytic performance was observed in the esterification reaction with high conversion of acid (95.34%) and high yield of n -octyl acetate (94.81%). Reusability study of the catalyst showed that the catalyst could be used efficiently up to three reaction cycles. This study explores the use of cenospheres to prepare a solid acid catalyst for the industrially important esterification reactions.

Hollow Fe3O4@DA-SO3H: an efficient and reusable heterogeneous nano-magnetic acid catalyst for synthesis of dihydropyridine and dioxodecahydroacridine derivatives

In this work, for the first time, a highly stable and efficient super-paramagnetic catalyst, H-Fe3O4@DA-SO3H, involving hollow morphology of Fe3O4 as core and dopamine as shell was prepared through hydrothermal template-free method. It has been used as a new and recoverable catalyst for various one-pot multi-component organic reactions such as synthesis of 1,4-dihydropyridine (1,4-DHP) and 1,8-dioxodecahyroacridine derivatives. The new magnetic catalyst was characterized with different analyses including X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), vibrating sample magnetometer (VSM) and thermogravimetric analysis (TGA). Moreover, the ρ shell of the prepared hollow-Fe3O4 microparticles was calculated, being found just slightly lighter than that of solid sphere-like Fe3O4. The catalyst was conventionally recovered, using an external magnet and reused at least in six successive runs, without appreciable loss of its activity.

Heterogeneous Synthesis of Indole-2-Carboxylic Esters Via Bischler Cyclization Under the Catalysis of Sulfonic Acid-Functionalized SBA-15 Silicas

Phenylsulfonic acid-functionalized SBA-15 silica was found to be an efficient heterogeneous acid catalyst in Bischler cyclization for the synthesis of indole-2-carboxylic esters. Under the optimized conditions, a wide range of substituted 4-nitrobenzyl 3-hydroxy-2-(N-methyl-N-arylamino)-2-enoates could be smoothly transformed to the corresponding 4-nitrobenzyl indole-2-carboxylates in excellent yields (87–99 %). Moreover, the catalyst could be conveniently recovered and reused at least four times without significant loss of catalytic activity.

New heterogeneous catalyst for the esterification of fatty acid produced by surface aromatization/sulfonation of oilseed cake

In this work, an efficient heterogeneous acid catalyst for the esterification of oleic acid was prepared directly from oilseed cake by a simple sulfonation with concentrated H2SO4. Characterization by SEM/EDS, IR, Raman, TG, TG/MS, potentiometric titration showed that treatment with H2SO4 for 1, 2 and 4h at 120°C partially dehydrates the cake to form a carbon/cellulose composite which is sulfonated to produce strong SO3H acidic sites. These surface sites were active for the esterification of oleic acid with yields ca. 84%, 88% and 94% in the presence of 5, 10 and 20wt% catalyst, respectively. These results are comparable to 98% yield obtained with 1wt% H2SO4 and higher than 75% observed for a high surface area (880m2g−1) sulfonated activated carbon with similar number of SO3H active groups. These results are discussed in terms of two effects: (i) the number of sulfonic surface acidic groups and (ii) the presence of a hydrophilic cellulosic fraction in the catalyst that adsorbs/traps water formed in the reaction shifting the esterification equilibrium and improving the yield.

SYNTHESIS AND BIOLOGICAL EVALUATION OF SPIRO[INDOLINE-3,4'-PYRANO[2,3-C:6,5-C']DIPYRAZOL]-2-ONES IN THE PRESENCE OF SBA-Pr-SO3H AS A NANOCATALYST

Sulfonic acid functionalized SBA-15 nanoporous material (SBA-Pr-SO3H) with a large pore size of 6 nm, a high surface area, high selectivity, and excellent chemical and thermal stability was applied as an efficient heterogeneous nanoporous acid catalyst in the reaction of isatin with pyrazolones under mild reaction conditions. A novel class of symmetrical spiro[indoline-3,4'-pyrano[2,3-c:6,5-c']dipyrazol]-2-one derivatives was successfully obtained in high yields. Comparison of these results with those reported in the literature shows that the current method is efficient, and results in better reaction times and yields of the desired products. Other advantages of this new method are its operational simplicity, easy work-up procedure, and the use of SBA-Pr-SO3H as a reusable and environmentally benign nanoreactor, such that the reaction proceeds easily in its nanopores. We also tested the antimicrobial activity of the prepared compounds using the disc diffusion method, and some of the synthesized compounds exhibited the best results against B. subtilis and S. aureus.

Propylsulfonic acid and methyl bifunctionalized TiSBA-15 silica as an efficient heterogeneous acid catalyst for esterification and transesterification

Propylsulfonic acid and methyl bifunctionalized TiSBA-15 silica material, TiSBA-15-Me-PrSO3H, is prepared by a direct nonionic surfactant-templated sol–gel co-condensation approach combined with low-temperature hydrothermal treatment. The structural integrity of the incorporated propylsulfonic acid groups and terminally bonding methyl groups are studied by 13C CP-MAS NMR and 29Si MAS NMR spectroscopy, while the chemical state of Ti(IV) species in the hybrid material is tested by XPS and UV–Vis/DRS. The ordered mesostructure, morphology and porosity of as-prepared hybrid material are characterized by low-angle XRD measurements, TEM observations and nitrogen gas porosimetry measurements. As the efficient solid acid catalyst, the heterogeneous acid catalytic activity and stability of the TiSBA-15-Me-PrSO3H are evaluated by esterification of palmitic acid and transesterification of yellow horn oil with methanol under refluxing temperature (65°C) and atmospheric pressure. Based on the physicochemical properties and catalytic testing results, the excellent heterogeneous acid catalytic behaviors of as-prepared hybrid catalyst are explained by the contribution of their strong Brönsted and Lewis acidity, excellent porosity properties as well as surface hydrophobicity.

Sulfonic acid-functionalized mesoporous silica nanoparticles (SAMSNs): a recoverable heterogeneous acid catalyst for green synthesis of dicoumarols

Sulfonic acid-functionalized mesoporous silica nanoparticles (SAMSNs) have been used as a highly efficient and recoverable heterogeneous acid catalyst for green synthesis of dicoumarols by reaction of different aldehydes with 4-hydroxycoumarin in aqueous media. High to excellent yields were obtained. This mesoporous catalyst is readily recovered and can be reused at least six times without significant loss of its catalytic activity.

Freeze-Drying Kinetics in Synthesis of Biological Hydroxyapatite-Supported Catalyst

Kinetics of freeze-drying for the preparation of high performance bone-derived-hydroxyapatite (BDHAp) supported iron catalyst has been experimentally evaluated and modeled using standard drying models. The BDHAp was economically derived from Rohu fish (Labeo rohita) bone, which is considered as a municipal solid waste (MSW). After wet-impregnation of Fe 2 (SO 4 ) 3 .H 2 O on BDHAp, the precipitated mass was freeze-dried using three types of radiation viz. grey body radiation (GBR), infrared radiation (IRR) and tungsten halogen lamp radiation (THLR).Freeze-drying kinetics for all the different heating systems were evaluated and compared with standard drying models. THLR-assisted-freeze-drying (THLRAFD) rate was found maximum among all the thermal radiation. Midilli model was found to corroborate the experimental freeze-drying kinetics of THLRAFD operation. The acidity of the catalysts prepared through THLRAFD (10.27, 10.36 and 11.21 mmol KOH/g catalyst) was found higher than their air-dried counter parts (8.14, 9.01 and 9.60 mmol KOH/g catalyst) corresponding to 65, 75 and 85°C drying temperatures at 1.75 Fe 2 (SO 4 ) 3 .H 2 O to BDHAp weight ratio. The prepared Fe-BDHAp catalyst developed through THLRAFD possessed appreciable acidity making it suitable for application as an efficient heterogeneous acidic catalyst.

Application of SiO2-Pr-SO3H as an efficient catalyst in the Ritter reaction

Sulfonic-acid-functionalized silica was applied as an efficient heterogeneous acid catalyst in the Ritter reaction to prepare amides by reaction of various benzylic, allylic, and tertiary alcohols with various nitriles in good to excellent yields under solvent-free conditions. The simplicity of the reaction, recovery of catalyst without loss of reactivity, high yield of products, and short reaction time represent improvements over many existing methods.

Organic–inorganic hybrid porous aerogel: efficient catalyst in transesterification reactions

Hybrid silica-based porous aerogels containing propylsulfonic acid and methyl functionalities were prepared by co-condensation route from the corresponding mercaptopropyltriethoxysilane and methyltriethoxysilane precursors using aqueous ammonia as hydrolyzing agent in the absence of any organic templates. The hybrid aerogel was dried under supercritical CO2 and characterized by SEM, TEM, 13C CP-MAS NMR, 29Si MAS NMR, TG/DTA, and nitrogen adsorption/desorption analyses. The hybrid-silica aerogel containing propylsulfonic acid serves as an efficient heterogeneous acid catalyst in transesterification of fatty acid esters with methanol in a batch reactor.

One‐Pot Synthesis of 1,8‐Dioxo‐octahydroxanthenes Utilizing Silica‐Supported Preyssler Nano Particles as Novel and Efficient Reusable Heterogeneous Acidic Catalyst

A highly efficient one‐pot synthesis of 1,8‐dioxo‐octahydroxanthenes from dimedone and various aromatic aldehydes under reflux conditions in water, catalyzed by silica‐supported preyssler nano particles (SPNP) is reported. The products were formed in excellent yields and the acidic catalyst was completely heterogeneous and can be recycled for many times.

MOF-5 as an efficient heterogeneous catalyst for Friedel–Crafts alkylation reactions

A highly porous metal-organic framework (MOF-5) was synthesized by a solvothermal method, and used as an efficient heterogeneous acid catalyst for Friedel–Crafts alkylation reactions. The solid acid catalyst was characterized using a variety of different techniques, including X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), atomic absorption spectrophotometry (AAS), and nitrogen physisorption measurements. Quantitative conversion was achieved under mild conditions without the need for an inert atmosphere. The MOF-5 catalyst could be facilely separated from the reaction mixture, and could be reused several times without significant degradation in catalytic activity. Furthermore, no contribution from homogeneous catalysis of active acid species leaching into reaction solution was detected.

Design of mesoporous SO42−/ZrO2–SiO2(Et) hybrid material as an efficient and reusable heterogeneous acid catalyst for biodiesel production

Mesoporous sulfated zirconia material functionalized by ethane-bridged organosilica moieties was prepared in a single step. Compared with alkyl-free sulfated zirconia materials, the as-prepared hybrid catalyst showed much higher catalytic activity towards biodiesel production from pure triglyceride as well as low-cost virgin plant oil.

Highly efficient heterogeneous acylations of aromatic compounds with acid anhydrides and carboxylic acids by montmorillonite-enwrapped titanium as a solid acid catalyst

Montmorillonite-enwrapped titanium hydroxide species (Ti4+-mont) acted as a highly efficient heterogeneous acid catalyst for the acylation of aromatic compounds with acid anhydrides or carboxylic acids. The catalytic activity of the Ti4+-mont was higher than those of other acid catalysts such as zeolites, SO42−/ZrO2 and p-toluenesulfonic acid. For example, the reaction of anisole with dodecanoic acid in the presence of the Ti4+-mont catalyst gave 1-(4-methoxyphenyl)-1-dodecanone in 97% yield. Furthermore, the Ti4+-mont catalyst was easily separated from the reaction mixture and was recyclable.

Synthesis of Ordered Microporous Silicates with Organosulfur Surface Groups and Their Applications as Solid Acid Catalysts

Mercaptopropyl-functionalized porous silicates were synthesized by the co-condensation of (mercaptopropyl)triethoxysilane and tetramethoxysilane in the presence of a cationic surfactant. The ordered hexagonal arrays of channels in the extracted product were microporous (14 A pore diameter) and contained high concentrations of alkylthiol functions. It was possible to oxidize the supported thiol groups to sulfonic acid groups, thus creating a solid acid ion exchanger. The sulfonic-acid functionalized material is an efficient heterogeneous acid catalyst.