Efficient Solid Acid Catalyst Research Articles

Facile construction of a stable biomass-derived carbon-supported AlZr composite with crystalline solid solution and Brønsted-Lewis dual acidity for efficient catalytic conversion of cellulose.

Exploiting cellulose-derived levulinic acid (LA) in biorefinery has potential application prospects, and the development of efficient and stable catalysts is crucial yet challenging. In this study, a bimetallic synergy strategy was proposed to construct an efficient and durable solid acid catalyst with crystalline solid solution by a totally solid-phase method. Mechanical activation (MA)-treated precursor (metal salts, starch, and urea) was calcined to obtain a stable biomass-derived carbon (BC)-supported AlZr (MA-AZ/BC) composite, which was applied for catalytic conversion of cellulose to LA in aqueous-phase system. The results indicate that the synergistic effect of bimetallic crystalline solid solution and the existence of Brønsted-Lewis dual-acid sites in the MA-AZ/BC catalyst contributed to a cellulose conversion efficiency of 97.5% and a LA yield of 67.1%. Benefiting from the strong bimetal-support interaction, the MA-AZ/BC catalyst exhibited favorable stability and recoverability. On the basis of comprehensive analysis, a reaction mechanism of Brønsted-Lewis dual-acid sites for synergistic catalytic conversion of cellulose was proposed. This study provides a new idea for the rational design and environmentally friendly fabrication of functional BC-based catalysts for efficiently producing platform compounds derived from biomass.

Nanostructured Iron (III)-Copper (II) Binary Oxide as a Highly Efficient Magnetically Recoverable Nanocatalyst for Facile One-pot Synthesis of 2, 4, 5-trisubstituted Imidazole and 1, 4-dihydro Pyridine Derivatives under Solvent-free Conditions

Abstract: The Fe (III)-Cu (II) binary oxide magnetic nanocatalyst emerges as an environmentally friendly and highly efficient solid acid catalyst, demonstrating remarkable utility in the one-pot synthesis of 2, 4, 5-trisubstituted imidazole and 1,4-dihydropyridine compounds, all achieved under solvent-free conditions. A facile co-precipitation method was used to synthesize nanostructured Fe-Cu binary oxide. Notably, this Fe-Cu binary oxide magnetic nanocatalyst proves its eco-friendly credentials as an exceptionally efficient and reusable catalyst, offering ease of handling, recovery, and multiple uses with minimal reactivity loss. Furthermore, the Fe (III)-Cu (II) binary oxide magnetic nanocatalyst's magnetic separability enhances its practicality, allowing for effortless catalyst retrieval after reactions. Significantly, the structural characteristics are meticulously elucidated through advanced analytical techniques, including 1H and 13C nuclear magnetic resonance (NMR) spectroscopy. This work presents a versatile and sustainable solution for catalysis, with wide-reaching implications for green chemistry and the development of reusable, efficient catalysts for organic synthesis. The exceptional performance and eco-friendliness of the Fe-Cu binary oxide magnetic nanocatalyst underscore its practical significance. Fe-Cu binary oxide magnetic nanocatalyst exhibits the highest catalytic activity compared to others. The employment of this catalyst consistently delivers excellent yields in the target reactions, highlighting its potential to contribute positively to sustainable chemical processes.

Synthesis and characterization of alumina supported molybdosilicic acid (SiMo12/Al2O3): Efficient solid acid catalyst for the synthesis of pyranopyrazole derivatives

A series of highly reusable heterogeneous catalysts (10-40 wt.% SiMo12/Al2O3), consisting of molybdosilicic acid (SiMo12) impregnated on alumina (Al2O3) support was synthesized by the wetness impregnation method. The physicochemical properties of synthesized catalyst were studied using FT-IR, XRD, SEM, EDX, TEM, BET and TG-DTA analysis techniques. The study proves that the synthesized SiMo12 catalyst efficiently incorporated on the surface of Al2O3. The catalytic activity of prepared catalyst was investigated for the synthesis of pyranopyrazole(6-amino-4-phenyl-3-methyl-2,4-dihydropyrano[2,3-c]pyrazole-5carbonitrile) via cyclocondensation reaction of aldehydes, malononitrile, hydrazine hydrate and ethyl-acetoacetate under solvent-free conditions. Among different catalysts, 30% SiMo12 supported on to Al2O3 showed the highest catalytic activity. High yield, shorter reaction time, operational simplicity, solvent-free conditions and reusability of the catalyst are the distinct features of this protocol.

Heteropoly acid catalysis in the valorization of bio-renewables: Acetylation of 1,4-cineole and 1,8-cineole (eucalyptol) in green solvents

In this work, a novel synthesis of monoterpenic acetate esters potentially valuable as flavoring agents was developed. It involves the reactions of 1,4-cineole and 1,8-cineole with acetic anhydride giving the desired products in 80–88 % total yields. The process is performed under ambient conditions in green solvents such as methyl isobutyl ketone, methyl ethyl ketone, dimethyl carbonate or diethyl carbonate in the presence of acidic cesium salt of phosphotungstic acid, Cs2.5H0.5PW12O40, as an efficient solid acid catalyst. The catalyst is stable toward leaching in the reaction system and can be reused. The process produces mixtures of acetate esters with different flavor bouquets which can be used directly as ingredients in fragrance compositions without separating individual compounds.

Biomass derived sulfonated carbon catalysts: efficient catalysts for green chemistry

BDSCCs, known as efficient solid acid catalysts with easy preparation and a green source, are anticipated to play a role in advancing circular and economic development in various sectors.

Acidic ionic liquid-functionalized ordered mesoporous polymers: Highly efficient solid acid catalysts for water-medium organic reactions

Strong acidic ionic liquid-functionalized mesoporous organic material (MPOM-T-AIL) has been created by quaternary ammonization of mesoporous organic material (MPOM) with 1,3-propane sultone and subsequent strong acid (H2SO4 or HSO3CF3) acidification. The novel supporting material, MPOM, had high nitrogen content and was synthesized by direct high-temperature (400–550 °C) polymerization of an easily prepared and low cost protic salt [pPDA][2HSO4], which was obtained by simple neutralization of p-phenylenediamine with two equivalents of H2SO4. MPOM-T-AIL possesses high BET specific surface area, ordered and uniform mesoporosity, hydrophobic property, and highly active acidic ionic liquid components. Catalytic tests in the water-medium Prins reactions and acetalization of benzaldehyde with ethylene glycol showed that MPOM-T-AIL exhibits much better catalytic activities and reusabilities than commercially available solid acid catalysts Amberlyst 15 and H-ZSM-5, and mineral acid H2SO4. Additionally, MPOM-T-AIL significantly improved the catalytic selectivity of the water-medium Prins reaction, which was strongly related to its hydrophobic property. MPOM-T-AIL with excellent catalytic performance is a promising new solid acid catalyst for various acid-catalyzed reactions.

High-efficiency recyclable reduced graphene oxide-tin oxide nanocomposite catalyst for esterification

Graphene oxide (GO) possesses 2D nanostructures and was synthesized indigenously via the enhanced Hummer method. It is well-accepted that the redox approach is a distinctive technique to fabricate GO on an expanded scale. Here, reduced graphene oxide-tin oxide (SnO2-rGO) nanocomposite material was produced for application as an efficient heterogeneous solid acid catalyst esterification reaction. Fourier transform infrared analysis was carried out to validate the incidence of oxygen functional groups in GO and SnO2-rGO nanocomposite. The Raman spectra of GO and SnO2-rGO nanocomposite have been simulated to get stable structure and functional groups. To get surface morphological and structural features, powder X-ray diffraction, scanning electron microscope-energy dispersive X-ray spectra, transmission electron microscope and high resolution-TEM analysis, and thermogravimetric analysis were delineated during this experimental study. It is seen that the catalyst has high efficiency for esterification reaction. The maximum efficiency (96% yield) was obtained when a 1:3 (acetic acid to benzyl alcohol) molar ratio, catalyst (25 mg), temperature (60 0C), and time (4 h) were maintained. The SnO2-rGO nanocomposite was recycled several times with a minimal loss of its efficiency.

Sulfated iron oxide mesoporous silica [SO42−/Fe2O3–mSiO2]: A highly efficient solid acid catalyst for the green production of pharmaceutically significant 7-hydroxy-4-methyl coumarin, 3,4-dihydropyrmidinone and hydroquinone diacetate

Sulfated iron oxide mesoporous silica [SO42−/Fe2O3–mSiO2]: A highly efficient solid acid catalyst for the green production of pharmaceutically significant 7-hydroxy-4-methyl coumarin, 3,4-dihydropyrmidinone and hydroquinone diacetate

Ionic Liquid Functionalized Polymer as an Efficient Solid Acid Catalyst for the Esterification Between Methanol and Methylacrylic Acid

Ionic Liquid Functionalized Polymer as an Efficient Solid Acid Catalyst for the Esterification Between Methanol and Methylacrylic Acid

Metallic W/WO2 solid-acid catalyst boosts hydrogen evolution reaction in alkaline electrolyte

The lack of available protons severely lowers the activity of alkaline hydrogen evolution reaction process than that in acids, which can be efficiently accelerated by tuning the coverage and chemical environment of protons on catalyst surface. However, the cycling of active sites by proton transfer is largely dependent on the utilization of noble metal catalysts because of the appealing electronic interaction between noble metal atoms and protons. Herein, an all-non-noble W/WO2 metallic heterostructure serving as an efficient solid-acid catalyst exhibits remarkable hydrogen evolution reaction performance with an ultra-low overpotential of −35 mV at −10 mA/cm2 and a small Tafel slope (−34 mV/dec), as well as long-term durability of hydrogen production (>50 h) at current densities of −10 and −50 mA/cm2 in alkaline electrolyte. Multiple in situ and ex situ spectroscopy characterizations combining with first-principle density functional theory calculations discover that a dynamic proton-concentrated surface can be constructed on W/WO2 solid-acid catalyst under ultra-low overpotentials, which enables W/WO2 catalyzing alkaline hydrogen production to follow a kinetically fast Volmer-Tafel pathway with two neighboring protons recombining into a hydrogen molecule. Our strategy of solid-acid catalyst and utilization of multiple spectroscopy characterizations may provide an interesting route for designing advanced all-non-noble catalytic system towards boosting hydrogen evolution reaction performance in alkaline electrolyte.

Bimetallic Zrx-Aly-KIT-6 modified with sulfate as acidic catalyst for biodiesel production from low-grade acidic oils

For the purpose of fabricating an efficient solid acid catalyst for biodiesel production from low-grade acidic oils, bimetallic silica mesoporous composites with different Zr/Al molar ratios were initially synthesized via a facile one-step hydrothermal method, and then sulfated with sulfuric acid at different concentrations to get a series of sulfated Zrx-Aly-KIT-6 catalysts (denoted as SZA-K, where x/y represents the molar ratio of Zr to Al). The sulfated bimetallic solid catalysts were fully characterized by using XRD, FT-IR, TEM, SEM, EDS, NH3-TPD, and nitrogen porosimetry measurements. Results showed that the remarkable amount of acidic sites in the catalysts was derived from the Zr and Al incorporation and further sulfation, and specifically, the Zr4+ and Al3+ could afford abundant weak acid sites while the inductive effect of SO42− species greatly influences the acidic strength of this solid catalyst. In combination with the enhancement in mass transfer resulting from the inherent interconnected mesoporous structure, the SZA-K catalyst could facilitate the transesterification reaction to take place efficiently. The sulfated Zr5–Al1-KIT-6 catalyst (Zr/Al molar ratio of 5/1, treated using 0.75 mol/L sulfuric acid for 12 h) exhibited enhanced acid strength with larger number of acidic sites (7.81 mmol/g), resulting in a high catalytic performance to the oil transesterification reaction. An oil conversion of 96.3% was attained for the transesterification reaction performed at 120 °C for 7 h by using a methanol/oil molar ratio of 20:1 and a catalyst dosage of 6 wt%. Further, this solid catalyst exhibited better acid and water-resistance capacity with above 80% of oil conversion even with 10% of free fatty acid (FFA) and 2% of moisture present in the low-grade acidic oils. Meanwhile, the good reusability was shown for this catalyst with 80.1% conversion even after reusing for three cycles. The good stability of the solid catalyst was resulted from the strong interactions between the acidic species and the bimetallic composite support.

Hierarchical LTL Zeolite as an Efficient and Sustainable Solid Acid Catalyst for Replacing HCl in the Production of Polyurethane Intermediates.

In many industrially important reactions, caustic mineral acid catalysts have been successfully replaced with green solid acids such as zeolites. In this context, extensive efforts have been devoted to replacing HCl to produce methylenedianiline (MDA), a key intermediate in polyurethane production. Unfortunately, limited success has been achieved thus far due to low activity, selectivity towards the desired 4,4'-MDA, and rapid catalyst deactivation. Here we report that meso-/microporous hierarchical LTL zeolite exhibits unprecedentedly high activity, selectivity, and stability. The one-dimensional cage-like micropores of LTL promote the bimolecular reaction between two para-aminobenzylaniline intermediates to selectively produce 4,4'-MDA and inhibit the formation of undesired isomers and heavy oligomers. Meanwhile, the secondary mesopores alleviate mass transfer limitations, resulting in a 7.8-fold higher MDA formation rate compared to solely microporous LTL zeolite. Due to suppressed oligomer formation and fast mass transfer, the catalyst exhibits inappreciable deactivation in an industrially relevant continuous flow reactor.

Hierarchical LTL Zeolite as an Efficient and Sustainable Solid Acid Catalyst for Replacing HCl in the Production of Polyurethane Intermediates

AbstractIn many industrially important reactions, caustic mineral acid catalysts have been successfully replaced with green solid acids such as zeolites. In this context, extensive efforts have been devoted to replacing HCl to produce methylenedianiline (MDA), a key intermediate in polyurethane production. Unfortunately, limited success has been achieved thus far due to low activity, selectivity towards the desired 4,4′‐MDA, and rapid catalyst deactivation. Here we report that meso‐/microporous hierarchical LTL zeolite exhibits unprecedentedly high activity, selectivity, and stability. The one‐dimensional cage‐like micropores of LTL promote the bimolecular reaction between two para‐aminobenzylaniline intermediates to selectively produce 4,4′‐MDA and inhibit the formation of undesired isomers and heavy oligomers. Meanwhile, the secondary mesopores alleviate mass transfer limitations, resulting in a 7.8‐fold higher MDA formation rate compared to solely microporous LTL zeolite. Due to suppressed oligomer formation and fast mass transfer, the catalyst exhibits inappreciable deactivation in an industrially relevant continuous flow reactor.

Improved surface acidity of niobium doped tungstated-zirconia solid acid catalyst over production of 5-hydroxymethylfurfural

The 5-hydroxymethylfurfural (5-HMF) acts as an important chemical intermediate to bridge the biomass resources and industrial applications, which shows the potential for green development. However, the performance of biomass materials conversion to 5-HMF is still limited in the green solvent. Herein, an effective approach is reported to prepare the highly efficient solid acid catalysts, NbOx/WOy-ZrO2, to improve fructose conversion. It is found that the introduction of Nb results in the generation of the niobium oxides, which improves acid sites and tunes the ratios of Brønsted acid and Lewis acid on the surface of the WOy-ZrO2 support. With the acidity improvement and increasing acid sites of the NbOx/WOy-ZrO2, the highest fructose conversion is 99% in water. Meanwhile, the 5-HMF yield and the selectivity are also as high as 50.1% and 50.7% under the reaction temperature of 180 °C for a short reaction time of 30 min. The proposed NbOx/WOy-ZrO2 catalyst strategy will not only open a new way for designing the solid acid catalysts to achieve high performance of the 5-HMF in the water, but also promote the green production of biomass and sustainable development in the future.

Sulfonic acid functionalized β zeolite as efficient bifunctional solid acid catalysts for the synthesis of 5-hydroxymethylfurfural from cellulose

Introduction of the sulfonic acid group into H-β zeolite to prepare β-SO3H bifunctional catalysts for the efficient synthesis of 5-hydroxymethylfurfural (HMF) from cellulose. Catalysts characterization, such as XRD, ICP-OES, SEM (Mapping), FTIR, XPS, N2 adsorption-desorption isotherm, NH3-TPD, Py-FTIR demonstrate the sulfonic acid group was successfully grafted onto the β zeolite. A superior HMF yield (59.4 %) and cellulose conversion (89.4 %) was obtained in the H2O(NaCl)/THF biphasic system under 200 °C for 3 h with β-SO3H(3) zeolite as catalyst. More valuable, β-SO3H(3) zeolite converts other sugars and obtains ideal HMF yield, including fructose (95.5 %), glucose (86.5 %), sucrose (76.8 %), maltose (71.5 %), cellobiose (67.0 %), starch (68.1 %), glucan (64.4 %) and also converts plant material (25.1 % for moso bamboo and 18.7 % for wheat straw) with great HMF yield. β-SO3H(3) zeolite catalyst keeps an appreciable recyclability after 5 cycles. Moreover, in the presence of β-SO3H(3) zeolite catalyst, the by-products during the production of HMF from cellulose were detected, and the possible conversion pathway of cellulose to HMF was proposed. The β-SO3H bifunctional catalyst has excellent potential for the biorefinery of high value platform compound from carbohydrates.

Sulfonated ionic liquid immobilized SBA-16 as an active solid acid catalyst for the synthesis of biofuel precursor 5-hydroxymethylfurfural from fructose

The catalytic conversion of biomass-derived chemicals to 5-hydroxymethylfurfural (HMF) is of high current interest. In this work, an efficient solid acid catalyst was synthesized by anchoring sulfonic imidazolium-based ionic liquid (IL) over the surface of mercaptopropyl-modified SBA-16 via thiol-ene click reaction. Various characterization techniques exhibited that the mesostructure of SBA-16 was preserved after the immobilization of acidic IL on its surface. The catalytic activity of the synthesized catalyst was evaluated for the dehydration of fructose to HMF. The influence of different reaction parameters on the catalyst efficiency was examined and optimized. A maximum HMF yield of 98% was attained after 30 min of reaction at 120 °C in dimethyl sulfoxide (DMSO) with a catalyst load of 15 mg. Importantly, the catalyst was simply recoverable and can be reused for five successive runs.

Sustainable aromatic production from catalytic pyrolysis of lignin mediated by a novel solid Lewis acid catalyst

Lignin catalytic pyrolysis for sustainable aromatic production is a promising approach for reducing the overwhelming dependence on fossil resources while mitigating CO2 emissions. The key to achieving the efficient catalytic pyrolysis of lignin lies in the rational design of advanced catalysts with excellent deoxygenation capacity. In this study, we develop a novel mixed metal oxide (WOx-TiO2-Al2O3) as efficient solid Lewis acid catalysts for the catalytic pyrolysis of lignin. We demonstrate that WOx-TiO2-Al2O3 exhibits the best catalytic ability at a pyrolysis temperature of 600 °C with a catalyst-to-lignin weight ratio of 2. The yields of bio-oil and monocyclic aromatic hydrocarbons (benzene, toluene, and xylene) can respectively reach 30.2 wt% and 1.6 wt%, which is slightly lower than those of the commercial HZSM-5 catalyst (31.7 wt% and 1.9 wt%). We also prove that the M−O−M bonds formed between oxygenophilic metals can generate electron holes as the temperature increasing. Those holes may combine with C-O bonds of phenolic compounds to generate metal–oxygen–carbon (M−O−C) bonds, facilitating the deoxygenation of lignin-derived pyrolysis vapours. These findings may provide guidance for the design of novel solid Lewis acid catalysts for the direct deoxygenation of lignin for the preparation of aromatic compounds.

Synthesis of Hollow Mesoporous Silica Nanospheroids with O/W Emulsion and Al(III) Incorporation and Its Catalytic Activity for the Synthesis of 5-HMF from Carbohydrates

Controlling the particle size as well as porosity and shape of silica nanoparticles is always a big challenge while tuning their properties. Here, we designed a cost-effective, novel, green synthetic method for the preparation of perforated hollow mesoporous silica nanoparticles (PHMS-1) using a very minute amount of cationic surfactant in o/w-type (castor oil in water) emulsion at room temperature. The grafting of Al(III) through post-synthetic modification onto this silica framework (PHMS-2, Si/Al ~20 atomic percentage) makes this a very efficient solid acid catalyst for the conversion of monosaccharides to 5-HMF. Brunauer–Emmett–Teller (BET) surface area for the pure silica and Al-doped mesoporous silica nanoparticles (MSNs) were found to be 866 and 660 m2g−1, respectively. Powder XRD, BET and TEM images confirm the mesoporosity of these materials. Again, the perforated hollow morphology was investigated using scanning electron microscopic analysis. Al-doped hollow MSNs were tested for acid catalytic-biomass conversion reactions. Our results show that PHMS-2 has much higher catalytic efficiency than contemporary aluminosilicate frameworks (83.7% of 5-HMF yield in 25 min at 160 °C for fructose under microwave irradiation).

Efficient conversion of biomass derivatives to furfural with a novel carbon-based solid acid catalyst

The novel carbon-based solid acid catalyst (S-800-CG) was synthesized by high-temperature carbonization of calcium gluconate followed by sulfonation with 4-diazoniobenzene sulfonate at room temperature. The catalyst was characterized by TEM, SEM, N2 adsorption-desorption, TGA, FT-IR, and XPS to reveal its physical and chemical properties. The S-800-CG was used as a catalyst for converting xylose or corncob into furfural via a one-step process. Furthermore, the effects of calcination temperatures of the carbon support, reaction temperature, residence time, catalyst loading, and substrate concentration were investigated. It was demonstrated that S-800-CG is an efficient solid acid catalyst for furfural production from xylose in 1,4-dioxane. 85.9% furfural yield can be achieved from 50 mg xylose at 140 °C in 40 min by using 100 mg catalyst. Moreover, 52.9% furfural yield was obtained from 200 mg corncob at 190 °C in 70 min using 100 mg catalyst.

Nano TiCl4/γ-Al2O3: An efficient heterogeneous solid acid catalyst for rapid and solvent-less synthesis of azo dyes based on 2-naphthol at room temperature

A green heterogeneous solid acid was prepared as an extremely efficient catalyst, through the reaction of γ-alumina with titanium tetrachloride. Nano TiCl4/γ-Al2O3 was characterized by fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), Brunner–Emmet–Teller (BET) surface area analysis, X-ray fluorescence (XRF) and thermal gravimetric analysis (TGA). Nano TiCl4/γ-Al2O3 was used for the synthesis of aryl diazonium salts as the starting reactant and then, diazo coupling with 2-naphthol produced the azo dyes in a solvent-free medium at room temperature (25 °C). The work-up of the reaction is easy, and the catalyst is removed from the products by simple filtration.