Catalyst For Synthesis Research Articles

Advancing H-Bonding Organocatalysis for Ring-Opening Polymerization: Intramolecular Activation of Initiator/Chain End.

Organocatalytic ring-opening polymerization (ROP) of lactones is a green method for accessing renewable and biodegradable polyesters. Developing new organocatalysts with high activity and controllability is a major and challenging research topic in this field. Here, we report a series of organocatalysts to achieve a fast and controlled ROP of lactones. These catalysts incorporate (thio)urea and alkoxide in one molecule and act as initiators in the ROP. Such catalysts enable an effective intramolecular activation of initiator/chain end, as revealed by computational studies, resulting in higher activity and fewer (thio)urea loads than existing (thio)urea/alkoxide binary systems. These organocatalysts exhibit ultrahigh activity comparable to metal complexes, i.e., turnover number up to 900 and turnover of frequency up to 4860 min-1, affording polyesters with tailor-made structure, predicted molecular weights, narrow dispersity, less epimerization, and minimal transesterification. The catalyst synthesis is simple and scalable, allowing widely tuned activities of the ROP.

A Chemically Robust 2D Ni-MOF as an Efficient Heterogeneous Catalyst for One-Pot Synthesis of Therapeutic and Bioactive 2-Amino-3-Cyano-4H-Pyran Derivatives.

Despite possessing numerous catalytic advantages of MOFs, developing 2D frameworks having excellent chemical stability along with new catalytic properties, remains a grand challenge. Herein, by employing a mixed ligand synthetic approach, we have constructed a 2D Ni-MOF, IITKGP-52, which exhibits excellent framework robustness in open air, water, as well as over a wide range of pH solutions (2-12). Benefitting from its robustness and abundant Lewis acidic open metal sites, IITKGP-52 is explored in catalyzing the heterogeneous three-component condensation reaction for the tandem synthesis of bioactive 2-amino-3-cyano-4H-pyran derivatives with low catalytic loading, greater compatibility for a wide range of substrates, excellent recyclability and superior catalytic efficiency than the previously employed homo and heterogeneous systems. IITKGP-52inaugurates the employment of MOF-based catalysts for one-pot synthesis of therapeutic and bioactive 2-amino-3-cyano-4H-pyran derivatives.

Development of ruthenium-based catalysts for ammonia synthesis via polyol reduction method

In this work, ruthenium-based catalysts were synthesized via polyol reduction method with different metal oxides as support and caesium as promoter. The samples were characterized through XRD, ICP-OES, nitrogen physisorption and XPS. Then, the catalysts were tested for ammonia synthesis in the range of temperatures 548–673 K and pressures 1–5 MPa. The synthesized catalysts allowed an ammonia production rate approximately four times higher compared with the performances of similar catalytic formulations in literature (tested at same conditions). The best performance were achieved with the Cs–Ru/CeO2 (1%wt Cs, 5%wt Ru), reaching an ammonia production of nearly 73 mmol h−1∙gcat−1 at 673 K and 5 MPa. As showed by the XPS analysis, the increased Ce3+/Ce4+ ratio led to an enhancement of oxygen vacancies, which favoured the dissociative adsorption of nitrogen, that is the limiting step in the ammonia synthesis reaction. Such high catalytic activity can be ascribed to the beneficial effect of the polyol reduction method for the maximization of the exposure of active sites.

Tailoring the Compositions and Nanostructures of Trimetallic Prussian Blue Analog-Derived Carbides for Water Oxidation.

The electrochemical splitting of water for hydrogen production faces a major challenge due to its anodic oxygen evolution reaction (OER), necessitating research on the rational design and facile synthesis of OER catalysts to enhance catalytic activity and stability. This study proposes a ligand-induced MOF-on-MOF approach to fabricate various trimetallic MnFeCo-based Prussian blue analog (PBA) nanostructures. The addition of [Fe(CN)6]3- transforms them from cuboids with protruding corners (MnFeCoPBA-I) to core-shell configurations (MnFeCoPBA-II), and finally to hollow structures (MnFeCoPBA-III). After pyrolysis at 800°C, they are converted into corresponding PBA-derived carbon nanomaterials, featuring uniformly dispersed Mn2Co2C nanoparticles. A comparative analysis demonstrates that the Fe addition enhances catalytic activity, while Mn-doped materials exhibit excellent stability. Specifically, the optimized MnFeCoNC-I-800 demonstrates outstanding OER performance in 1.0mKOH solution, with an overpotential of 318mV at 10mAcm-2, maintaining stability for up to 150h. Theoretical calculations elucidate synergistic interactions between Fe dopants and the Mn2Co2C matrix, reducing barriers for oxygen intermediates and improving intrinsic OER activity. These findings offer valuable insights into the structure-morphology relationships of MOF precursors, advancing the development of highly active and stable MOF-derived OER catalysts for practical applications.

Economic limitation of recent heterogeneous catalysts for ammonia synthesis

The economic performance of newly developed catalysts for ammonia synthesis, Ru/Ca(NH2)2 and Ru/Pr2O3, are evaluated by process simulation using Aspen Plus©. The results show that the high activity of the new catalysts reduces the electricity cost for pressurizing reactant gases; however, the electricity for lowering the temperature in ammonia separation through liquefaction is significant due to the mitigated pressure and almost compensates for the decreased cost. The results show an economic limitation to current research trends that develop a catalyst for ammonia synthesis under low pressure. It is noted that catalyst costs are high due to expensive ruthenium; thus, the lifetime of catalysts significantly influences the total cost. With the assumption of a long lifetime of catalysts, the new catalysts are advantageous when the electricity cost is high, the characteristics of the case in which renewable energy is employed. As the future direction of the catalyst development, recycling or extending the lifetime of the catalysts and replacing Ru with cheap metal will be crucial from the economic viewpoint. Moreover, effective methods for ammonia collection, such as adsorbents, should be focused on reducing the electricity of ammonia liquefaction in cooling separation and giving a vital meaning to the condition mitigated by the newly developed catalysts.

Sustainable catalysts for propylene synthesis.

Sustainable catalysts for propylene synthesis.

Kinetics and soft computing evaluation of Linseed oil transesterification via CD-BaCl-IL catalyst

A novel clay-doped ionic liquid and BaCl (CD-BaCl-IL) heterogeneous catalyst for biodiesel synthesis from linseed oil (LSO) was generated after 4 h of calcination at 600°C using Scanning Electron Micrograph (SEM), X-ray Diffraction (XRD), Brunauer-Emmett-Teller (BET), Fourier Transform Infrared Spectroscopy (FT-IR) and X-ray fluorescence (XRF) was used to evaluate the catalyst's processability. After optimization using response surface methodology (RSM), the second-order polynomial model was shown in the Analysis of variance (ANOVA) with R2 values of 0.9947, Adj R2 (0.9850), and Pred R2 (0.8594), demonstrating model acceptability. The maximum biodiesel yield (97.097 %) was obtained with 2.6 wt% catalyst, 6 mol/mol methanol/molar ratio, 1.5 h, 50 °C, and 400 rpm agitation. ANFIS predicted biodiesel yield more accurately than ANN (R2 = 0.999, MSE = 0.27594), with the lowest MSE (R2 = 0.99, MSE = 0.00038). Under optimal conditions, this study employed a kinetic model based on two elementary chemical processes: Eley-Rideal (ER) and Langmuir-Hinshelwood-Hougen-Watson (LHHW). The LHHW model accurately described CD-BaCl-IL catalyst experimental data at 50 °C, with favourable parameters, an R2 value of 0.9348, and a variance of 2.61E-8. The surface reaction between adsorbed triglyceride and alcohol dictated the rate-determining step. Temperature increased the rate, indicating an endothermic process. The reaction's activation energy and frequency factor were 10.22 kJ/mol and 6.41 h-1, respectively. Linseed biodiesel met the D6751 criterion.

Influence of pore structure on catalytic performance of Cs-Zr/SiO2 catalyst for methyl methacrylate synthesis from methyl propionate and formaldehyde

Methyl methacrylate (MMA) synthesis via aldol condensation of methyl propionate with formaldehyde over Cs-based supported catalysts is intensively investigated, while the effect of their pore structures on catalytic performance still lacks in-depth understanding. Herein, series of Cs-Zr/SiO2 catalysts with different pore structures were prepared for this aldol condensation. The physicochemical characteristics of as-prepared Cs-Zr/SiO2 catalysts were characterized using physical N2 adsorption–desorption isotherms and CO2–/NH3-TPD. In addition, the impact of pore structure on mass transfer, adsorption, and desorption of reactants and products was studied through in situ DRIFTS. The results show that the acid and base site densities elevated with the increasing pore volume. The mass transfer of reactants and products could be promoted with increasing pore size, while their adsorption energies exhibited a volcanic trend. As a result, the Cs-Zr/SiO2 catalysts having average pore diameter of 12–18 nm and acid-base balance was considered as the optimal candidate for MMA production.

Design of Dendritic Foldamers as Catalysts for Organic Synthesis

Background:: Multistranded foldamers mimic biopolymer architecture, through the assembly and folding of intrinsically flexible polymeric chains attached to polyol core have been synthesised here. The synthesised dendritic motifs possess helical cavities with properly arranged active sites. As these cavities are large enough to accommodate guest molecules, their application as synthetic foldamer catalyst were investigated in Knoevenagel and Mannich reactions. Methods:: It is presumed to be the potentiality of dendritic foldamers to form reverse micelle in the interior of helical motif containing many reactive sites. Results:: Inside the dendritic foldamer, the substrates are adequately concentrated, work together in cooperation for ligand-binding, and stabilize the transition state as in enzymes that helps to accelerate the reaction rate many times greater than in bulk solution. Conclusion:: An unrivalled reaction rate and high yield of products were obtained within a short time in both Knoevenagel and Mannich reactions by using dendritic foldamers as catalysts.

Tin-Based Keggin-Type Phosphomolybdate and Silicomolybdate as Catalysts for the Green Synthesis of Adipic Acid

The catalytic activity of two series of Keggin-type salts of formula Cs4-xSnxSiMo12O40 (x: 0.5 and 1) and Cs3-xSnxPMo12O40 (x: 0.25-1) was examined in the liquid phase cyclohexanone oxidation to adipic acid (AA) in the solvent absence. The materials were prepared and characterized by FTIR, UV-Vis and SEM. The adipic acid synthesis was carried out at 90°C in presence of hydrogen peroxide (30%), a green oxidant that produces only water as by-product. The effects of catalyst/substrate molar ratios and time reaction on dipic acid yields were studied. The results of this study showed that the POM-H2O2 system was found to be efficient for the production of adipic acid from the oxidation of cyclohexanone and the yields were closely dependent on the operating conditions. The highest AA yield (55%) was obtained with Cs2Sn0.5PMo12O40 using a catalyst/substrate molar ratio of 3.7×10-3 and a reaction time of 20h.

Constructing novel metal-free HCOF-Ph@g-C3N4 heterojunctions through molecular expansion to enhance photogenerated carrier involved molecular oxygen activation and photocatalytic hydrogen evolution

Modification of covalent organic frameworks (COFs) have exceptional stability as well as tunable structures is the key to efficient photocatalysts. In this study, hyper-crosslinked COF-Ph was constructed with g-C3N4 to obtain a novel HCOF-Ph@g-C3N4 heterojunction, and the lamellar mesoporous of g-C3N4 was successfully embedded into the pores of 3D HCOF-Ph. The synthetic strategy greatly enhanced the photocatalytic properties and molecular oxygen activation capability of the catalyst. 10 mg of HCOF-Ph@g-C3N4 heterojunction could completely degrade 30 mg/L of tetracycline (TC) within 14 min, and the rate of hydrogen generation reached 9214.69 μmol g−1 h−1. The active species in this process of photocatalysis were verified through tests with free radical trapping and ESR spectra. In addition, the molecular oxygen activation capacity of heterojunction interface and the yield of superoxide radicals were examined by 3,3′,5,5′-tetramethylbenzidine (TMB) oxidation and degradation of nitrotetrazolium nlue chloride (NBT) experiments, respectively. We found that the molecular expansion strategy can change molecule energy band structure to improve absorption of sunlight, and the efficient segregation of the photogenerated charge were ensured by the complementary energy band structure between g-C3N4 and HCOF-Ph. This study created an efficient molecular expansion method for the synthesis of COF-based catalysts with potential uses in the energy and environmental fields.

The impact of the porous structure on the efficiency of PdIn methanol synthesis catalysts

The characteristics of the porous structure and the specific surface area of the support have a significant impact on both the structure of the active sites and the efficiency of catalysts for the synthesis of methanol from CO2. The use of a complex of physicochemical methods of analysis in combination with the results of catalytic experiments has enabled the main tendencies in the development of productive and selective catalysts based on PdIn intermetallic nanoparticles to be established.

Effect of Mg modification on the catalytic performance of zinc malachite for methanol synthesis

The complex conditions of methanol production from coke-oven gas have brought challenges to the copper-based methanol synthesis catalyst. In this work, a series of zinc-malachite samples with different Mg contents were prepared. The zinc-malachite and calcined samples were characterized by in-situ X-ray diffraction (XRD), thermogravimetry-mass spectrometry (TG-MS), N2 physical adsorption, H2 programmed temperature reduction (H2-TPR), CO2 programmed temperature desorption (CO2-TPD) and other methods. The effects of Mg addition on the structure of zinc-malachite and its catalytic performance of methanol synthesis were investigated. The results showed that the addition of Mg increased the degree of Cu substitution inside the zinc-malachite structure and promoted the formation of high temperature carbonates in the catalyst after roasting. With the increase of Mg content, the specific surface area of the calcined catalyst increased gradually, and the Cu grain size decreased simultaneously. In-situ XRD results showed that a small amount of Mg could effectively inhibit the growth of copper grain size during the heat treatment. The evaluation showed that the initial activity of the catalyst increased first and then decreased with Mg addition, and the activity of the Mg-doped catalyst remained at a relatively high level after heat treatment. The appropriate Mg addition is beneficial to the initial activity and thermal stability of Cu-based methanol synthesis catalyst.

Recent progress in high‐entropy nanocatalysts

AbstractHigh‐entropy alloys (HEAs) are a promising group of materials composed of multiple elements (≥5) in nearly equal proportions (5 at%–35 at%), which exhibit uniformly mixed compositions and highly stable crystal structures and offer a wide range of design possibilities, making them exceptionally stable, multifunctional, and suitable for various applications. Recent research studies have identified the potential of HEAs as catalysts for electrocatalytic reactions, focusing on adjustable stress environments, optimizable d‐band centers, and high conformational entropy. Understanding the interactions among constituent elements, alloy formation, and catalytic reaction mechanisms is essential for optimizing HEAs' catalytic performance. This comprehensive review delves into the historical context, defining characteristics, and underlying significance of HEAs development. It also examines four primary effects of HEAs (high‐entropy effect, lattice distortion, sluggish diffusion, and cocktail effect) and their relevance to catalyst design criteria (selectivity, activity, stability, and cost). Additionally, it summarizes recent advances in nanostructured HEA catalyst synthesis, highlighting their advantages and challenges and explores the use of HEAs in electrocatalytic redox reactions involving small molecules (H, C, O, N). The paper underscores the importance of integrating experimental methods and theoretical calculations to design, synthesize, and understand alloy–property relationships of HEAs, emphasizing their vast potential for catalytic applications.

Performance of supported Co3O4 catalysts in the preferential oxidation of carbon monoxide: Effect of support type and synthesis method

This study investigated the performance of supported Co3O4 catalysts during the preferential oxidation of carbon monoxide (CO-PrOx) in a H2-rich environment, focusing on the effects of different catalyst synthesis methods, namely, wetness impregnation (WI) and solution combustion synthesis (SCS), and different support materials, namely, Al2O3 and SiC. During CO-PrOx, the SiC-supported Co3O4 catalysts attained higher CO2 yields when compared with the Al2O3-supported Co3O4 catalysts possibly because of the existence of weaker interactions between Co3O4 and SiC. Moreover, the catalysts prepared via SCS achieved higher CO2 yields than the catalysts prepared via WI likely due to the presence of smaller and well-dispersed Co3O4 particles in the SCS-prepared catalysts. Significantly high amounts of unwanted CH4 were produced over the SiC-supported catalysts between 225 and 250 °C. The high CO methanation activity was also attributed to the weaker Co3O4-SiC interactions, which enabled the easier reduction of Co3O4 to methanation active metallic Co.

Highly active manganese nitride-europium nitride catalyst for ammonia synthesis

The development of efficient catalysts for ammonia synthesis under mild conditions is critical for establishing a carbon-neutral society powered by renewable ammonia. While significant effort has been focused on Fe and Ru-based catalysts, there have been very limited studies on manganese-based catalysts for ammonia synthesis because of their low intrinsic catalytic activity. Herein, we report that the synergy between manganese nitride (Mn4N) and europium nitride (EuN) yields an ammonia synthesis rate that is 41 and 25 times higher than that of neat Mn4N and EuN, respectively. Detailed studies suggest that a [Eu-N-Mn] species at the interface of Mn4N and EuN plays a pivotal role in ammonia synthesis. Compositing of Mn4N with other rare earth metal nitrides such as LaN, PrN, and CeN also leads to a significant enhancement in catalytic activity. This work broadens the scope of advanced nitride catalysts for ammonia synthesis.

The Effect of Mole Ratio Natural-CaCO₃/KF in the Synthesis of KCaF₃ Perovskite Base Catalyst

The KCaF3 perovskite catalyst was successfully synthesized by reacting limestone (natural-CaCO3) with potassium fluoride (KF). The synthesis of the KCaF3 catalyst was conducted with several variations in the mole ratio of CaCO3 to KF (1:1, 1:2, and 1:3). The research results showed that the addition of KF can affect the characteristics of the catalyst. The optimal catalyst is the KCaF3 catalyst with a mole ratio variation of 1:3. X-ray diffractometer analysis revealed that the highest KCaF3 phase composition reached 74.05%, while thermogravimetric analysis indicated a CaCO3 concentration of 34.50%. Surface Area Analyzer analysis shows that KCaF3 has the largest surface area, which is 187.1 m2/g. This catalyst efficiently facilitated the transesterification of palm oil, yielding 93.4% biodiesel.

Ni-Fe2O3@SiO2-Pr-DBU: A novel efficient magnetically retrievable catalyst for one-pot synthesis of dihydropyrano [3,2-c] chromene

In the present work, Ni-Fe2O3@SiO2-Pr-DBU was synthesized as a novel magnetically separable nano-catalyst and characterized by various techniques like Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), Scanning electron microscopy (SEM), Vibrating-sample magnetometry (VSM), Transmission electron microscopy (TEM) and Elemental analysis by energy dispersive X-ray (EDX). The catalytic efficiency of NiFe2O3@SiO2-Pr-DBU was explored in the synthesis of dihydropyrano[3,2-c] chromenes through a one-pot multicomponent reaction of 4-hydroxycoumarin, malononitrile, and aryl aldehydes in aqueous solution at ambient temperature condition. An external magnet easily removed the nano-sized magnetic core catalyst from the synthesized reaction mixture. It was recycled for five successive runs while maintaining its potential and adhering to our green synthesis approach. We used dihydropyrano chromene, a highly biologically active commercial compound, to prepare some novel derivatives.

Synthesis and application of an effective magnetic catalyst immobilized copper oxide for the one-pot ultrasound-assisted synthesis of 1,4-dihydropyridines

In this study, Fe3O4 was modified with a biocompatible carbohydrate D-(+)-ribonic γ-lactone (RL) followed by immobilization with CuO nanoparticles (CuO NPs) to produce Fe3O4-APTES-RL-CuO as a Lewis acid catalyst. The sustainable RL can be utilized as a novel support for CuO NPs with increased catalytic activity. RL with plenty of hydroxyl groups not only catch the CuO NPs and prevents them from agglomeration but also, prevails upon immobilization of CuO NPs making the nanohybrid RL-supported CuO NPs significantly stable. This green and effective heterogeneous catalyst can be used for one-pot ultrasound-assisted synthesis of 1,4-dihydropyridines (1,4-DHPs) with high yield (95٪) and short time (15 min). The catalyst can be separated easily and cleanly by using an external magnet. This nanomagnetic catalyst is reused five times without any remarkable reduction in its activity. To illustrate the structure of the catalyst and characterize its physicochemical properties, different techniques like FT-IR, XRD, FE-SEM, EDS, TGA, and VSM were applied.

Cavitation-assisted synthesis and chracterization of a novel catalyst from waste coconut trunk biomass for biodiesel production

In the current study, a novel heterogeneous catalyst has been prepared from waste coconut trunk biomass using an ultrasound-assisted batch reactor. It is observed from the characterization studies that the raw coconut trunk biomass consists of the maximum amount of silicon dioxide (SiO2) present in it which is further converted to mullite (composition of 3Al2O3.2SiO2) with a composition of 94.18 % (analyzed through Energy Dispersive Spectroscopy (EDAX) studies) is formed through the reaction in an ultrasound reactor processed at a very mild reaction temperature and reaction time 80℃ and 90mins. Synthesis of catalyst at mild process conditions will help to enhance the formation of energy-intensive products at a low cost. It is also observed from the XRD studies of raw feedstock and synthesized catalyst a change in the crystalline structure from hexagonal silicon dioxide to orthorhombic mullite shape. In comparison with the surface area of the raw biomass and mullite, a large amount of surface area ∼ 32 m2/g is observed which is due to the process of reaction in a highly intense ultrasound reactor. A change in the morphological structure of raw feedstock and synthesized catalyst is also observed through scanning electron microscope (SEM) analysis. The activity of the synthesized catalyst has been analyzed through its application in the production of biodiesel from waste cooking oil is also studied., and a yield of 75 % with a conversion of 74 % is observed at process conditions of 1:3 (oil: ethanol) (volumetric ratio), 3 (wt%) of catalyst concentration and 3hrs of reaction time. A prospective aspect of the implication of the entire work to analyze the life cycle analysis (LCA) is also reported in terms of environmental friendliness and sustainability.