Acid Catalyst Research Articles

Multifunctional HxMoO3-y-MoO2/Carbon Composite Particles for Water Remediation.

Solving a scarcity of freshwater resources is an urgent global challenge by a safe and sustainable approach using renewable energy. We demonstrate the multifunctional catalyst of HxMoO3-y-MoO2/carbon composite particles toward highly efficient water remediation. A one-step mechanochemical reaction successfully upgraded the composites from commercially available MoO3-polypropylene (PP) powders without introducing hydrogen gas. The composite particles exhibited broad light absorption in the UV-visible (Vis)-near-infrared (NIR) region (200-2000 nm), with an optical band-gap narrowing to 1.03 eV. The plasmonic properties of HxMoO3-y-MoO2 allowed a fast water evaporation rate (3.29 kg m-2 h-1) with a photothermal conversion efficiency of 88.8%. In addition, the HxMoO3-y-MoO2 heterojunction dominated wide-spectrum activity under Vis and NIR light irradiation, up to 3 orders of magnitude higher than pristine MoO3 in the photocatalytic degradation of azo-dye pollutants. Furthermore, the byproduct carbon with abundant oxygen-containing groups efficiently eliminated water pollutants as a Brønsted acid catalyst and performed exceptional adsorption capacities of heavy metal ions in the dark.

Divergent Enantioselective Access to Diverse Chiral Compounds from Bicyclo[1.1.0]butanes and α,β-Unsaturated Ketones under Catalyst Control.

Achieving structural and stereogenic diversity from the same starting materials remains a fundamental challenge in organic synthesis, requiring precise control over the selectivity. Here, we report divergent catalytic methods that selectively yield either cycloaddition or addition/elimination products from bicyclo[1.1.0]butanes and α,β-unsaturated ketones. By employing chiral Lewis acid or Brønsted acid catalysts, we achieved excellent regio-, diastereo-, and enantioselectivity across all three distinct transformations, affording a diverse array of synthetically valuable chiral bicyclo[2.1.1]hexanes and cyclobutenes. The divergent outcomes are controlled by the differential activation of the substrates by the specific chiral catalyst with the reaction conditions dictating the pathway selectivity. This strategy demonstrates the power of divergent catalysis in creating molecular complexity and diversity, offering a valuable tool for the synthesis of enantioenriched chiral building blocks.

Heavea brasilienis (Rubber seed oil) as cost effective non edible feedstock for sustainable high quality biofuel production.

Biodiesel is renewable fuel acquired from biomass which has short chain alkyl esters derived from vegetable oil or animal fats. It has greater advantages over traditional diesel oil. In first level esterification, H2SO4 is used because the acid catalyst to decrease the FFA from 4. 5% to 0. 85 %. In 2nd stage, transesterification chemical process was carried with methanol and NaOH, the elevated temperature 600c and response time is 45 min to 75min. Only a few experiments have been carried out for evaluating the results of equation using a Scientific tool.

Furanic jet fuels – Water-free aldol condensation of furfural and cyclopentanone

A method for the water-free, large-scale synthesis of bio-jet fuel precursors, distinct from traditional fossil-based sources, is introduced. This approach involves the aldol condensation of furfural with cyclopentanone, producing C10-C15 fuel precursors eligible for further hydrodeoxygenation to high-performance diesel and jet fuel hydrocarbons. In the context of process integration, aldol condensation reactions were conducted under water-free conditions, utilizing excess furfural as the solvent. Evaluation of various commercial catalysts confirmed the feasibility of running in excess furfural. Both basic and acidic catalysts demonstrated significant activity, with CaO and amorphous silica-alumina achieving ≥80 mol% conversion of cyclopentanone and yielding ≥80 mol% selectivity towards the desired fuel components within 5 h of reaction. However, an overlooked aspect is the notable formation of undesired heavy side products. Observations indicated that the high furfural concentration, combined with the use of strong acidic catalysts, were the primary cause of heavy side product formation. The strong base catalyst, CaO, significantly reduced the formation of these oligomers, but did not appear to stop it completely. Interestingly, water content did not appear to play a major role in byproduct selectivity. To further suppress the formation of oligomers, the use of process-owned intermediates as solvents is proposed.

Quantum-chemical study of alkyl- and alkenyladamantanes formation by ionic alkylation with olefins

In B3LYP-D3(BJ)/6-311++G** approximation thermodynamic parameters of formation reactions (total energy at 0 К, enthalpy and the Gibbs free energy at temperature 298.15 К and pressure 101325 Pa) are assessed for the products of ionic alkylation of adamantane and lower alkyladamantanes with ethylene and propylene. Aluminium chloride was used as acid catalyst model. Quantum-chemical calculations demonstrate the influence of methyl groups in adamantanes and olefin molecular weight on energetics of formation of relevant alkyl- and alkenyladamantanes.

Aromatic Poly(dithioacetal)s: Spanning Degradability, Thermostability, and High Refractive Index Towards Eco-friendly Optics.

In the quest for eco-friendly optics, high refractive index polymers (HRIPs) with degradability have been one of the desirable optical materials for realizing eco-friendly and efficient lighting technologies. However, it has been challenging for HRIPs to simultaneously realize thermostability, high refractive index (RI), visible transparency, and efficient degradability, all of which are essential for their practical use. In this context, we herein focus on aromatic poly(dithioacetal)s, composed of visible-transparent yet degradable dithioacetal moieties and rigid diphenyl disulfide spacers, exhibiting moderately high Tg (> 60 °C), high RI (> 1.7), and colorless film features. In addition, poly(dithioacetal)s can balance (1) high stability under the operating conditions even upon heating and (2) quantitative degradability that can selectively yield cyclic low-molecular-weight products that can be further repolymerized upon further addition of an acid catalyst. These results provide a key concept for high refractive index polymers that allow on-demand degradability and recyclability without compromising their high potential thermal and optical properties.

Comparative Analysis of Optimal Reaction Conditions for Hydrothermal Carbonization and Liquid Hot-Water Processes in the Valorization of Peapods and Coffee Cherry Waste into Platform Chemicals

The management of coffee and peapod waste presents significant environmental challenges, with millions of tons generated annually, leading to disposal issues and resource inefficiencies. Hydrothermal processes offer a promising valorization method, though biomass characteristics significantly influence the resulting products. Biomass characterization revealed distinct profiles for coffee cherry waste (moisture: 10.94%, ashes: 7.79%, volatile matter: 79.91%, fixed carbon: 1.36%, cellulose: 27.6%, hemicellulose: 12.5%, and lignin: 13.7%) and peapods (moisture: 7.77%, ashes: 4.22%, volatile matter: 74.18%, fixed carbon: 13.0%, cellulose: 20.2%, hemicellulose: 17.4%, and lignin: 5.0%). Experiments were conducted in 100 mL and 500 mL hydrothermal reactors with varying conditions for temperature (120–260 °C), time (1–4 h), stirring (none and at 5000 and 8000 rpm), biomass/water ratio (1:5, 1:10, 1:20, and 1:40), particle size (0.5–5 mm), and catalysts (acids and bases). The results showed that peapods produced over 30 times more platform chemicals than coffee. High temperatures (over 180 °C) degraded peapods, whereas coffee yields increased. Both biomasses were influenced similarly by reaction conditions: lower biomass/water ratios, smaller particle sizes, acid catalysts, and no stirring increased yields. Peapods consistently had higher yields than coffee in all conditions. Biochar analysis revealed anthracite from coffee and coal from peapods.

Microwave-Assisted Synthesis of Bis-(Hydroxybenzylidene)-Cycloalkanones via Acid Catalyzed Claisen-Schmidt Condensation

In the present study, bis-(hydroxybenzylidene)cycloalkanone derivatives were synthesized by Claisen-Schmidt condensation using cycloalkanones and arylaldehydes in the presence of HCl as an acid catalyst. The synthetic reaction was carried out under microwave irradiation. The structure of the synthesized compounds was determined by UV, IR, 1H NMR spectroscopic methods. The obtained reaction yields were not optimal due to the self-polymerization of p-hydroxybenzaldehyde in an acid solution.

Halloysite Nanotube Modified (CuO@HNTs-SO3H) Novel Heterogeneous Catalyst for One-Pot Synthesis of Tetrahydrobenzo[ɑ]Xanthen-11-One

In this study, CuO@HNTs-SO3H was investigated as a novel eco-friendly heterogeneous solid acid catalyst prepared by straightforward co-precipitation method. Thus, the cost-effective CuO NPs was used to modify halloysite nanotubes initially, which were subsequently further functionalized with sulfonic acid. The prepared catalyst was analyzed by means of FT-IR, XRD, EDX, SEM and TGA methods. Its catalytic activity is investigated in the solvent-free one-pot condensation of various aromatic aldehydes, dimedone, and β-naphthol to produce tetrahydrobenzo[a]xanthen-11-one derivatives. A few benefits of the discovered method are its simple process, quick reaction time, high yields (96%), affordable cost, and the catalyst ability to be reused without losing its activity.

Copper-Catalyzed Enantioselective [4π + 2σ] Cycloaddition of Bicyclobutanes with Nitrones.

The selective construction of bridged bicyclic scaffolds has garnered increasing attention because of their extensive use as saturated bioisosteres of arene in pharmaceutical industry. However, in sharp contrast to their racemic counterparts, assembling chiral bridged bicyclic structures in an enantioselective and regioselective manner remains challenging. Herein, we describe our protocol for constructing chiral 2-oxa-3-azabicyclo[3.1.1]heptanes (BCHeps) by enantioselective [4π + 2σ] cycloadditions of bicyclo[1.1.0]butanes (BCBs) and nitrones taking advantage of a chiral copper(II) complex as a Lewis acid catalyst. This method features mild conditions, good functional group tolerance, high yield (up to 99%), and excellent enantioselectivity (up to 99% ee). Density functional theory (DFT) calculation elucidates the origin of the reaction's enantioselectivity and the mechanism of BCB activation by Cu(II) complex.

Selective synthesis of oxygenated fuel derivative from microwave assisted acetalization of glycerol: Optimization and mechanistic investigations

Glycerol contains 52 wt% oxygen content, therefore unable to be directly used as fuel due to its poor combustion ability. Thus, the catalytic conversion of glycerol into various oxygen-containing fuel additives is grabbing more attention nowadays. This work provides a novel, sustainable, and eco-friendly method for synthesizing heterogeneous acid carbon catalysts from pearl millet cob (PMC) waste. The hydrothermal carbonization process was carried out at different temperatures to fabricate the series of sulfonated pearl millet cob (SPMC) catalysts. XRD, FT-IR, SEM-EDS, XPS, BET, TGA, and CHNSO analyses were performed to characterize fabricated catalysts. The synthesized catalyst, SPMC-70 (catalyst synthesized at 70 °C temperature), possesses OH, COOH, and SO3H functional groups and a significant total acid density (2.03 mmol/g) with 37 m2/g surface area. The SPMC catalysts were employed for the microwave-assisted acetalization reaction of glycerol with acetone for solketal production. The optimization process was carried out using various reaction parameters, including catalyst dosage (2–6 wt.%), reaction temperature (30–60 °C), glycerol to acetone (GL to AC) molar ratio (1:3–1:9), and reaction time (4–13 min). The SPMC-70 catalyst showed the highest catalytic activity among all the synthesized catalysts and provided 99.11 ± 0.3 % GL conversion with 100 % selectivity of solketal under optimal reaction conditions. Additionally, the recyclability test was performed, and it found that the best catalyst was reusable for up to five reaction cycles. These results showed the effectiveness of carbon-based heterogeneous acid catalysts in deriving a fuel additive, solketal.

Synthesis and characterization of functionalized cerium and zirconium metal-organic frameworks as novel solid acid catalysts for hydrogen generation

Synthesis and characterization of functionalized cerium and zirconium metal-organic frameworks as novel solid acid catalysts for hydrogen generation

Biobased Chemicals from d-Galactose: An Efficient Route to 5-Hydroxymethylfurfural Using a Water/MIBK System in Combination with an HCl/AlCl3 Catalyst.

5-Hydroxymethylfurfural (HMF) is an attractive building block for biobased chemicals. Typically, ketoses like d-fructose (FRC) are suitable starting materials and give good yields of HMF in a simple aqueous phase process with a Bro̷nsted acid catalyst. With aldoses, such as d-glucose (GLU), much lower yields were reported in the literature. Here, we report an experimental and modeling study on the use of d-galactose (GAL) for HMF synthesis, using a liquid-liquid system (water/MIBK) in combination with an HCl/AlCl3 catalyst. Experiments were conducted in a batch system with temperatures between 112 and 153 °C, HCl and AlCl3 concentrations ranging from 0.02 to 0.04 M, and initial GAL concentrations between 0.1 and 1.0 M. The highest HMF yield was 49 mol % obtained for a batch time of 90 min at 135 °C. This value is much higher than in experiments with GAL in a monophasic aqueous system with HCl as the catalyst (2 mol % HMF yield) under similar reaction conditions. Based on detailed product analyses, a reaction scheme is proposed in which the isomerization of GAL to tagatose (TAG), catalyzed by the Lewis acid AlCl3, is the first and key step. TAG is then converted to HMF by Bro̷nsted acid HCl. The experimental data were modeled using a statistical approach as well as a kinetic approach. The kinetic model demonstrates a good agreement between the experimental and modeled data. Our findings reveal that temperature is the reaction variable with the most significant influence on the HMF yield. The use of a biphasic system appears to be a promising method for HMF production from GAL.

Facile synthesis of hierarchically porous carbon monolith without templating agent for various applications in energy and catalysis

Monolithic carbon with hierarchically porous structure has a promising prospect for a wide range of applications in the fields of energy, environment, catalysis, etc. Due to the reliance on the utilization of templating agents, conventional preparation approaches often suffer from time-consuming preparation, complex post-processing, and uneconomical cost. Herein, we develop a novel strategy to match the sol-gel transition with the phase separation process for the direct preparation of hierarchically porous carbon monolith (HPCM) without templating agent. Resorcinol and resol are employed as carbon sources to adjust the polymerization for the formation of bi-continuous microstructure. Well-defined hierarchical pores and large specific surface area for fast mass diffusion enable the HPCM to be a prospective kind of electrode material in supercapacitor with an outstanding specific capacitance over 350 F g−1 (1.0 A g−1). After facile sulfonation, the modified HPCM can act as solid acid catalyst to realize a high-performance production of 5-hydroxymethylfurfural (5-HMF) in a 90 % yield with turnover frequency (TOF) value up to 155.9 h−1. Additionally, HPCM also exhibits an excellent Joule heating effect, which can be applied to the thermal management after compounding with phase change materials. The desirable integrated performance enables HPCM to be a valuable material suitable for various applications.

Recent Advances in Combining Photo- and N-Heterocycle Nitrenium Catalysis

AbstractN-Heterocyclic nitreniums (NHNs) are isoelectronic and isostructural analogues of N-heterocyclic carbenes (NHCs). Unlike NHCs, NHNs are much less developed. While a comprehensive understanding of NHN reactivity remains elusive, recent advancements have demonstrated their utility as Lewis acid catalysts, photoreductants, and photooxidants, leading to several reaction patterns. In this short review, we focus on the applications of NHNs in photoredox reactions. We also discuss the mechanisms behind these transformations and outline future research directions.1 Introduction2 Application of N-Heterocyclic Nitreniums as Photoreductants3 Application of N-Heterocyclic Nitreniums to Facilitate Photohomolysis4 Application of N-Heterocyclic Nitreniums as Photooxidants5 Conclusion

Hydrothermal growth of Zn2GeO4 nanorods for optical and (Photo)Catalytic applications: An experimental and theoretical study

From the material design perspective, we reported a systematic investigation based on theoretical and experimental approaches to explore the physical properties of Zn2GeO4 nanorods prepared by hydrothermal method with different zinc precursors for optical and (photo)catalytic applications. All ZGO samples exhibited uniform nanorod morphology with high purity and crystallinity. A negative zeta potential ranging from −13 mV to −16 mV have been observed for these nanorods. Bandgap values indicated variations among samples synthesized with different precursors. The photoluminescence and photocatalytic activities for these nanorods, have been attributed to the presence of oxygen vacancies on the Zn2GeO4 surfaces. Experimental evidence suggests that these surface defects favor the formation of hydroxyl radicals identified as primary reactive oxygen species responsible for the methylene blue photodegradation. Toxicity testing of photocatalytic residues showed minimal phytotoxic effect on lettuce seed (Lactuca sativa) germination. Additionally, Zn2GeO4 was utilized as an acid catalyst for synthesizing isoxazol-5(4H)-ones, resulting in an increase in the yield from 69 % to 92 % by using this catalyst in multicomponent reactions. Lastly, the theoretical efforts outlined in the study aim to enhance the comprehension of the material design with well-defined morphology using realist theoretical models for the Zn2GeO4 nanorods for the first time.

Microwave and ultrasound-assisted green protocols for 5-methylthiazole induced Betti bases: molecular docking, in-silico pharmacokinetics, and anticancer activity studies

ABSTRACT Herein, we describe an efficient one-pot three-component microwave and ultrasound-endorsed approaches for synthesizing distinct 5-methylthiazole induced Betti bases (5-methyl-thiazol-2-ylamino-aryl-benzylnapthols) employing silica sulfuric acid (SSA, silica-OSO3H) as an active heterogeneous acid catalyst. The title compounds produced in good yields (86–95%) from naphthalen-2-ol, 5-methylthiazol-2-amine, and assorted aryl aldehydes; and structurally characterized by spectral and elemental analyses. A comprehensive comparative study of conventional, ultrasonic, and microwave-irradiated synthetic routes has been achieved by optimizing various reaction parameters. These new protocols provide several advantages, including the use of an inexpensive, non-toxic, and reusable catalyst. Additionally, they benefit from mild reaction conditions, short reaction times, and simple workup and purification procedures, thereby increasing their practicality. Furthermore, the synthesized compounds were evaluated for their anticancer potency against A-549 (lung cancer) and A-498 (kidney cancer) cell lines, with scaffold IVa demonstrating excellent (GI50 < 10 µg/mL) inhibitory activity against A-549. Additionally, molecular docking was performed to investigate potential binding interactions between ligands and proteins. Scaffold IVa exhibited the best docking with cancerous target proteins 1M17 (−8.9 kcal/mol) and 1M14 (−7.2 kcal/mol), thereby supporting our bio-activity studies.

Heteroatom‐Containing Zeolites as Solid Lewis Acid Catalysts for the Cycloaddition of CO2 to Epoxides

AbstractThe catalytic cycloaddition of CO2 to epoxides to produce valuable cyclic carbonates represents a simple and promising strategy for CO2 utilization, circumventing the ineffective CO2 reduction process. Despite current progresses, there remains an impending demand for highly‐active, cost‐effective and stable catalysts especially the ideal heterogeneous catalytic systems. Herein, we report the preparation of heteroatom‐containing zeolites through a two‐step process comprising of framework dealumination and subsequent heteroatom incorporation, and their catalytic applications in CO2 cycloaddition to epoxides. Characterization results reveal the successful incorporation of heteroatoms into framework to derive Lewis acidic M‐Beta zeolites (M = Ti, Zr or Hf). The as‐prepared M‐Beta Lewis acids show remarkable performance in the model reaction of CO2 cycloaddition to propylene oxide with the assistance of potassium iodide under solvent‐free conditions. The reaction parameters have been optimized employing Ti‐Beta catalyst and the substrate scope has been investigated. Finally, the impact of Lewis acidity on the cycloaddition reaction is discussed and the actual bifunctional Ti‐Beta/KI catalyst system is proposed, which is of important significance for the understanding of CO2 catalytic cycloaddition to epoxides.

BPBSBDM as an influential Brønsted acidic ionic liquid catalyst in preparing bis(pyrazolyl)methanes under mild conditions

BPBSBDM as an influential Brønsted acidic ionic liquid catalyst in preparing bis(pyrazolyl)methanes under mild conditions

Facile synthesis of novel acidic modified magnetic graphene oxide and its application in the green synthesis of pyrimido[4,5-b]quinolines

This study aimed to create an innovative acidic nano catalyst capable of producing pyrimido[4,5-b]quinolines under environmentally friendly conditions. To achieve this objective, 1,3-benzenedisulfonyl amide (BDSA) was immobilized onto the surface of magnetic graphene oxide (GO/Fe3O4@PTRMS@BDSA@SO3H), and its surface was acidified using chlorosulfonic acid. The synthesized catalyst's structure was thoroughly examined and verified through various analyses, including FTIR, EDX, elemental mapping, FESEM, XRD, TGA, and DSC. This novel nano catalyst exhibited exceptional activity and selectivity in synthesizing pyrimido[4,5-b]quinoline derivatives under solvent-free conditions, at low temperatures, and with high efficiency. Its catalytic effectiveness stemmed from features such as easy and eco-friendly synthesis methods, abundant accessible catalytic sites, a high surface area, remarkable selectivity, and facile separation from the reaction medium. Additionally, the catalyst proved to be cost-effective, safe, scalable, and reusable for up to four times.