Heterogeneous Catalyst Research Articles

Integrated Ziegler-Natta/Brookhart-Ni Catalysts for the Synthesis of Sutured Polar High-Impact Polypropylenes.

The direct synthesis of polar high-impact polypropylenes using industrially-preferred heterogeneous catalysts is challenging due to the poisoning of polar functional groups towards metal center and the high stereo-selectivity requirement. In this work, dual-site catalysts combining Ziegler-Natta and Brookhart-Ni catalysts were used to produce polar polyolefin ionomers, followed by polar high-impact polypropylenes containing isotactic polypropylene and branched polyethylene as toughening agents. Three combination modes between these catalysts were investigated, including mixed, core-shell, and integrated types. The integrated dual-site catalyst achieved the optimal material properties because the polyolefin ionomer acted as a suture molecule that stitched different components into a whole network. This produced sutured polar high-impact polypropylenes with excellent mechanical properties and compatibility with polar substances. The restraining effect of the suture molecules greatly reduced the release of microplastic particles after aging. Moreover, the obtained polar high-impact polypropylene can serve as an efficient compatibilizer to recycle polyethylene/polypropylene mixed-waste plastics. This work provides an appealing and potentially practical strategy to upgrade the widely used polypropylenes and to alleviate the ever-growing plastic pollution issue.

Advancement in Heterogeneous Catalysts for the Synthesis of Benzothiazole Derivatives

AbstractBenzothiazole derivatives, a class of heterocyclic compounds, hold significant relevance in medicinal chemistry, materials science, and agrochemicals due to their diverse biological activities and applications. The conventional synthetic routes often involve harsh conditions and generate significant waste, prompting the exploration of more sustainable approaches. This work offers a comprehensive analysis of the developments in the use of heterogeneous catalysts for the production of benzothiazole derivatives, covering research from 2013 onward. Compared to traditional techniques, heterogeneous catalysts provide improved sustainability, efficiency, and recyclability. The review covers many heterogeneous catalysts and discusses their selectivity, recyclability, and catalytic activity. The utilization of heterogeneous catalysts is noteworthy as it facilitates the synthesis process's overall sustainability by allowing for milder reaction conditions, less environmental effect, and easier catalyst separation and recovery. The potential of heterogeneous catalysis in promoting the production of benzothiazole derivatives and satisfying the increasing need for these substances in various industrial applications is also highlighted.

High-Valent Iron–Oxo species in heterogeneous Catalysis: Formation, Mechanism, and reactivity for the degradation of various emerging organic contaminants

High-valent iron–oxo species (FeⅣ/Ⅴ=O), generated via peroxide activation with Fe-based catalysts, have shown potential in the selective and efficient degradation of organic contaminants. However, a comprehensive understanding of the oxidative degradation mechanism induced by FeⅣ/Ⅴ=O is still pending. In this research, to unravel this oxidation mechanism, an Fe-single atom catalyst (FeN4-C) was synthesized, and FeⅤ=O was formed as the predominant reactive species upon peroxymonosulfate (PMS) activation. The FeN4-C/PMS system was experimentally studied on its catalytic oxidation behavior for the degradation of 34 typical emerging organic contaminants (EOCs) in water, exhibiting a significant variation in the pseudo first-order kinetic rate constants (kobs) among the EOCs. A quantitative structure–activity relationship (QSAR) model was established based on the molecular structure feature and measured kobs of the EOCs. The model infers that EOCs with higher electron donating ability (EHOMO) are more susceptible towards FeN4-C/PMS oxidation, implying an electrophilic reaction following the single electron transfer (SET) mechanism. Further exploration of the degradation pathways for seven representative EOCs revealed that the oxidation occurs through the abstraction of either a hydrogen atom or a nonbonded (or π) electron by FeⅤ=O, enabling processes such as C-, N-, and S-oxidation, along with N- and O-dealkylation and deamination, to effectively degrade EOCs. These research findings provide a robust theoretical framework for understanding the reaction mechanisms and predicting the degradability and removal of various EOCs by FeⅣ/Ⅴ=O for water purification.

1,4-Bis(pyridin-1-ium)benzene trifluoroacetate coordinated to chloropropyl functionalized SiO2-nano-NiFe2O4 (BPBTCSF): as a novel and effectual mesoporous bi-functional magnetic catalyst for the synthesis pyrido[2,3-d:6,5-d']dipyrimidines

Here in, we report the synthesis of 1,4-Bis(pyridin-1-ium)benzene trifluoroacetate coordinated to chloropropyl functionalized SiO2-nano-NiFe2O4 (BPBTCSF). Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), elemental mapping analysis, Brunauer-Emmett-Teller (BET), thermal gravimetric analysis (TGA), vibrating-sample magnetometry (VSM) and X-ray diffraction (XRD) techniques characterized the framework of this catalyst. The catalytic activity of this nano-composite was then examined in the one-pot four-component reaction of 2-thiobarbituric acid, NH4OAc, and aldehyde for synthesis of pyrido[2,3-d:6,5-d']dipyrimidines under optimal conditions (5 mg of BPBTCSF, H2O, 25°C). BPBTCSF exhibits benefits as a heterogeneous catalyst, such as exciting performance in the production of derivatives (2 to 5 min, 90% to 98%), six times reproducibility with a slight decrease in catalytic activity, the simultaneous presence of acidic and basic sites (Hydrogen attached to the electronegative nitrogen atom and CF3COOˉ, respectively), convenient purification and separation from the reaction mixture.

Immobilized Tetrabutylammonium Amino Acid Ionic Liquids as Heterogeneous Catalyst in Biodiesel Production from Chlorella vulgaris

Ionic liquids (ILs) are molten salts below 100 °C with the ability to be used as a catalyst for biodiesel production. However, to this date, the implementation of ILs as catalysts remains an enigma due to their practicability. Immobilizing ILs onto waste biomass solid support may improve the sustainability of its implementation. This study is focused on synthesizing immobilized tetrabutylammonium amino acid ionic liquids (TBA AAILs) onto bamboo activated carbon (BAC) as catalysts in transesterification of fatty acids extracted from Chlorella vulgaris. Three AAILs, consisting of tetrabutylammonium paired with arginine, histidine, and lysine, were synthesized via neutralization reaction and immobilized onto BAC through wet impregnation method. Thereafter, microwave-assisted transesterification was performed with C. vulgaris as a feedstock. Impregnation of TBA AAILs caused modifications on morphology, chemical composition, and surface area of the BAC. [TBA][His]/BAC had greater impact compared to [TBA][Arg]/BAC and [TBA][Lys]/BAC, where it reduced the surface area up to 35 m2/g and pore volume to 0.020 cm3/g, initially BAC's surface area are 842 m2/g and pore volume of 0.387 cm3/g. Optimization with the Box-Behnken method achieved the highest yield 81.9% FAME using 20% [TBA][His]/BAC with 3% of catalyst dosage and 21 grams of methanol at 80°C for 48 mins with three times reusability. The immobilized TBA AAILs/BAC reduced IL consumption by 10 times and obtained comparatively higher yield than TBA AAILs, providing a sustainable alternative to conventional ILs catalyst.

Exploring the efficacy of calcined eggshell as a heterogeneous catalyst in enhancing biodiesel production through transesterification of Jatropha oil

Exploring the efficacy of calcined eggshell as a heterogeneous catalyst in enhancing biodiesel production through transesterification of Jatropha oil

Grafting of cinchonine onto rice husk nanosilica and its potential application in the synthesis of 2‐arylideneindan‐1,3‐diones and 2‐arylidene-5,5-dimethyl-1,3-cyclohexanedione

In this study, an eco-friendly and green procedure for Knoevenagel condensation reaction of aromatic aldehydes with indan-1,3-dione and dimedone was reported utilizing a rice husk silica‐anchored cinchonine nanocomposite as a heterogeneous catalyst in aqueous media. Without the need for an additional surfactant, rice husk was utilized as a raw material to create nanosilica. Through the grafting of 3-mercaptopropyl) trimethoxysilane, the rice husk nanosilica was modified. Next, azobisisobutylonitrile initiator was used to trigger the thiol-ene free radical interaction of the SH groups with the Cinchonine's alkene function. The morphology and structure of the nano SiO2-S-cinchonine were characterized using fourier transform infrared spectra, field emission scanning electron microscope, and energy-dispersive X-ray spectroscopy. The catalytic activity of the nanocomposite was investigated in the synthesis of 2-arylideneindan-1,3-diones and 2-arylidene-5,5-dimethyl-1,3-cyclohexanedione through an aqueous medium at 80 °C by the Knoevenagel condensation reaction. The advantages of this method are simple methodology, high yields, easy work-up, and green solvent.

Lithium iodide promoted CO2 hydrogenation towards ethanol via biphasic lewis-acid-base pairs synergistic catalysis

Ethanol synthesis via CO2 hydrogenation is of great importance in view of its high-value utilization. Herein, combining with heterogeneous and homogenous catalysis, we have developed an efficient biphasic Lewis-acid-base pairs synergistic catalysis strategy from CO2 hydrogenation. Apart from conventional heterogeneous ethanol synthesis route, it was surprisingly found that LiI homogenous promoter significantly enhanced CO2 conversion, ethanol selectivity, and productivity. LiI promoted CO2 dissolution in pure water and accelerated reaction intermediates consumption, favoring CO2 conversion. In detail, it can weaken C-O bond of CH3OH intermediate through Li+-I- Lewis-acid-base catalysis. The formed CH3I* with lower bond energy for C-I was more facile to dissociate into CH3*, favoring its subsequent coupling with CO* to form ethanol. In combination of Rh1/CeTiOx catalyst, LiI promoter, and methanol as solvent, a record-breaking ethanol yield was achieved (223.1 mmol·g−1·h−1). The obtained ethanol yield was about 18.7 times of that reported the best result in literatures. Especially, the established catalyst system could also be applied for synthesis of higher-carbon-number alcohols by the CO2 hydrogenation with other alcohols solvent (CnH2n+1OH, n = 2,3…).

Unraveling the synergistic mechanisms of dual-atom catalysts on BeN4 substrates for enhanced hydrogen evolution reaction: A machine learning-assisted first-principles study

Synergistic effects have been widely studied in both homogeneous and heterogeneous bimetallic catalysis. However, the exact mechanisms underlying the synergistic effects between bimetallic atoms remain elusive. This study, using density functional theory calculations, systematically explores a dual-atom catalyst (DAC) on a BeN4 substrate, where two beryllium atoms are substituted with transition metals. The results demonstrate that the dual-atom catalysis TMTM’@BeN4 exhibits synergistic effects. Notably, five DAC systems, particularly those co-doped with V and Cr, significantly reduce the Gibbs free energy (ΔGH∗) for the hydrogen evolution reaction (HER). We further utilized machine learning to explore how the dual-atom catalysts exhibit synergistic effects. Machine learning analysis indicates that changes in the average interatomic distance and the Fermi level of the catalyst system are the main factors influencing the Gibbs free energy variation in dual-atom catalysts, jointly determining the hydrogen evolution catalytic activity. This work provides profound insights into understanding the synergistic mechanisms of dual-atom catalysts.

Vitalizing Perovskite Oxide-Based Acetone Sensors with Metal-Organic Framework-Derived Heterogeneous Oxide Catalysts.

Perovskite oxides are promising candidates for chemiresistive-type gas sensors owing to their exceptional thermal and chemical stability during solid-gas reactions. However, perovskites suffer from critical issues such as low surface area and poor surface activity, which negatively influence the sensing characteristics. While metal nanoparticles can be incorporated in perovskites to improve their reactivity, the fundamental incompatibility between catalytic metals and perovskite oxides often leads to substantial structural degradation as well as phase instability. Herein, we overcome this challenge through the introduction of an intermediary phase that forms coherent interfaces with both the perovskite phase and catalyst metals. Specifically, we present the case study of p-type La0.8Ca0.2Fe0.98Pt0.02O3 perovskite, whose hole accumulation layer was modulated by the incorporation of metal-organic framework (MOF)-derived n-type α-Fe2O3 nanoparticles decorated with highly dispersed Pt catalysts. The resulting composite exhibited significantly improved surface activity over the nonmodified La0.8Ca0.2FeO3 perovskite, leading to exceptional chemiresistive sensing performance toward acetone gas (Rg/Ra = 39.8 toward 10 ppm of acetone at 250 °C) with high cross-sensitivity against interfering gases. Importantly, our findings reaffirm the critical influence of interfacial engineering in facilitating surface chemical reactions on perovskite oxides and, by doing so, effectively provide a general synthetic guideline to the design of perovskite-based chemiresistors.

Unveiling the influence of open metal sites in quasi ZIF-67 for eco-friendly catalysis of solvent-free aldehyde cyanosilylation

Quasi metal–organic frameworks (Q-MOFs) containing a high density of open metal centers are considered as an effective method of expanding the effectiveness of defective MOF-based catalysts. To achieve this, quasi ZIF-67 (Q-ZIF-67), having large scale structural defects in the framework, is produced through partial deligandation of ZIF-67 under controlled thermal treatment at 310 °C in air. This generates many unsaturated cobalt centers as Lewis acid sites, and results in the coexistence of micro and meso-pores within the Q-ZIF-67 network. Subsequently Q-ZIF-67 was employed in the catalytic cyanosilylation of benzaldehyde with trimethylsilyl cyanide, resulting in the corresponding cyanohydrin within 30 min under solvent free-conditions in air at 40 °C and room temperature with TOF values of 1.62, 1.53 min−1, respectively. The related cyanohydrin product was identified via 1H NMR. Importantly, Q-ZIF-67 displayed a highly efficient heterogeneous Lewis acid catalyst for the cyanosilylation of benzaldehyde compared to the pristine ZIF-67 and related cobalt oxide. Furthermore, investigating the impact of the electron-donating and electron-withdrawing para-substitutions on benzaldehyde revealed that electron-withdrawing groups are suitable for nucleophilic reactions. It was also observed that there was no significant decrease in catalytic activity after five catalytic runs. Thus, the Q-ZIF-67 has considerable potential as environmentally friendly catalyst for wide range of practical application in aldehyde cyanosilylation reactions.

Magnetic Fe3O4 nanoparticles supported on carbonized corncob as heterogeneous Fenton catalyst for efficient degradation of methyl orange

Magnetic Fe3O4 nanoparticles supported on carbonized corncob as heterogeneous Fenton catalyst for efficient degradation of methyl orange

Advancing Hybrid Nanocatalyst Research: A Python-based Visualization of Similarity Analysis for Interdisciplinary and Sustainable Development

Background: This study presents a comprehensive analysis of hybrid nanocatalysts, which amalgamate attributes of both heterogeneous and homogeneous catalysts. Aim: To achieve a holistic understanding of the topic, we embarked on a meticulous exploration across multiple databases. Methods: The Web of Science repository yielded 239 pertinent documents, while the Scopus database offered a more exhaustive collection of 1,887 documents. Although Google Scholar suggested a staggering 25,000 articles, its unclear selection criteria raised questions about the precision and dependability of its data. Hence, our study primarily relied on the Scopus database to ensure an extensive sample and analytical rigor. Using the Python-boosted visualization of Similarities methodology, we illuminated interconnections among various terminologies, identifying burgeoning areas within hybrid nanocatalyst research. Results: Our findings emphasized the ascending trajectory toward innovating materials with superior properties in hybrid nanocatalysis. This trajectory accentuated the pivotal role of interdisciplinary collaboration and sustainable methodologies. Advanced analytical techniques, notably X-ray diffraction, emerged as quintessential in delineating the nuanced relationship between hybrid nanocatalysts' structural and functional attributes. We also spotlighted Energy-Dispersive X-ray Spectroscopy's capability in fine-tuning hybrid nanocatalysts' properties, enhancing their catalytic efficacy and selectivity. An intriguing trend our study unearthed was the surge in interest toward integrating natural enzymes as potential catalysts within hybrid nanocatalysts, positioning them as beacons for sustainable and cost-efficient catalyst development. Conclusion: By synthesizing these insights, this research underlines the significance of diverse characterization techniques and the ethos of interdisciplinary collaboration. The derived knowledge offers a repository for fellow researchers, guiding further inquiries, especially regarding integrating natural enzymes in hybrid nanocatalyst innovation.

Efficient activation of peroxyacetic acid by cobalt-iron alloy/oxide heterojunctions anchored in defect-rich biochar for pesticide degradation in water: Unravelling the radical-unradical mechanism

The activation processes of peracetic acid (PAA-AOPs) have garnered significant attention in wastewater treatment. In this study, an amorphous carbon-modified bimetallic CoFe alloy/oxide catalyst (CoFe@DBCx-y, where x represents biomass mass and y represents pyrolysis temperature) was developed to activate PAA for the degradation of organochlorine pesticides (OCPs). Due to the size effect, biochar dynamically regulates the particle size of metal species, which is influenced by the pyrolysis temperature. Among these systems, the CoFeDBC2.0–700/PAA oxidation system effectively removed 95.7 % of 2,4-dichlorophenoxyacetic acid (2,4-D), exhibiting a kinetic constant 1.7 times higher than that of the Nano/PAA system. Furthermore, quenching experiments and electron paramagnetic resonance (EPR) analysis revealed that high-valent metal oxides (MIV = O) and singlet oxygen (1O2) are the primary active species responsible for the removal of 2,4-D, whereas organic radicals (RO·) and hydroxyl radicals (·OH) play a secondary role. Electrochemical and Raman spectroscopy tests revealed the formation of a metastable surface complex (≡Co(III)–OO(O)CCH3) between PAA and the catalyst, which acted as an intermediate oxidant to generate reactive oxygen species (ROS) through a chain reaction. Carbon defects in the biochar functioned as an electron source, continuously replenishing the electrons consumed in the reaction and facilitating the valence cycling between Co and Fe. This study provides new insights into the remediation of pesticide-contaminated wastewater using PAA-AOPs with heterogeneous bimetallic carbon-based catalysts.

Integrated capture and conversion of CO2 to methane using deep eutectic solvents under mild conditions

Addressing the issues of absorbent regeneration, CO2 compression and purification, and energy consumption during transportation in the integrated carbon capture and utilization (ICCU) process, an integrated technology for CO2 capture and hydrogenation conversion has been proposed. In this study, deep eutectic solvents (DESs) composed of tetramethylguanidine (TMG) and ethylene glycol (EG) were employed to capture and hydrogenate CO2. When a heterogeneous Ru-based catalyst and a TMG:EG DES were used as a catalytic system, CO2 methanation was achieved under mild conditions (170°C and 8 MPa H2 pressure), with a CH4 yield of up to 75 % and a conversion number (TON) of 148. Importantly, the structure of the DES remained unchanged before and after the reaction, and the catalytic system could be reused three times without significantly diminishing the effectiveness of CO2 hydrogenation. This method not only reduces desorption energy consumption but also benefits from the absorbent’s high specific heat capacity, enabling the absorbent to absorb the heat generated during CO2 hydrogenation and addressing issues such as carbon deposition and catalyst deactivation resulting from poor heat transfer.

Green Synthesis, Characterization, and Catalytic Applications of CuO Nanoparticles Using Prosopis Cineraria Seed Extract

Abstract The current study used a seed extract of Prosopis cineraria as a stabilizing and reducing agent to produce CuO nanoparticles via an easy, low-cost, affordable, and environmentally friendly synthesis process. The formation of copper oxide nanoparticles and the maximum absorbance of the CuO nanoparticles produced in the solution at 565 nm were verified by UV-vis. Copper oxide nanoparticles were found to have secondary metabolites on their surface, as shown by a distinctive Cu-O stretching band at 532 cm−1, which confirmed the reduced Cu2+ ions in copper oxide nanoparticles. This was confirmed by FTIR analysis. The XRD analysis confirmed the produced copper oxide nanoparticles’ monoclinic crystalline nanostructure with an average particle size of 34 nm. The phytonutrients in Prosopis cineraria seed extract stabilized and reduced copper, as demonstrated by the existence of copper and oxygen atoms at 85.2% and 12.5%, respectively, as demonstrated by SEM-EDX analysis. According to the HR-TEM study, copper oxide nanoparticles with a mean size of 18 nm are spherical in shape and well distributed. Prosopis cineraria seed extract-derived copper oxide nanoparticles were utilized as a catalyst in the Ullmann process to produce diphenyl ether. CuO nanoparticles produced by Prosopis cineraria seed extraction as a catalyst yielded 91% diphenyl ether. The results showed that a more ecologically friendly way of synthesizing copper oxide nanoparticles with great homogeneity of particle sizes could be achieved using seed extract. This work aims to facilitate heterogeneous catalysis from CuO nanoparticles utilising Prosopis cineraria seed extract. Overall, this technique offers several advantages, like high yields at fast reaction times, and low catalyst loading are just a few of this approach’s many benefits.

Facilitating catalytic research via better data reporting and curation: A case study of propane dehydrogenation on Ga/H-ZSM-5

In the field of experimental heterogeneous catalysis, the generation, analysis, and curation of large-scale, high-quality datasets are crucial yet challenging. This work highlights the significance of proper data reporting and curation through a case study on propane dehydrogenation over Ga/H-ZSM-5 catalysts. We demonstrate the challenges and benefits of analyzing larger datasets across multiple publications in the identification of active structures and elucidation of reaction mechanisms. The findings highlight the need for reporting reliable datasets in accessible format to facilitate integration and comparison of catalytic data across different studies, potentially leading to novel scientific insights.

Electrochemical synthesized copper mesh catalysts for catalytic combustion: A comprehensive study of Mn doping and atmospheric conditions during calcination

Metal-based monolithic catalysts offer significant advantages in heterogeneous catalysis attributed to their exceptional thermal conductivity and mechanical strength. However, controlling the loading of active components on metallic substrates remains a major challenge. Here, we synthesized a Mn-doped Cu mesh catalyst using a facile electrochemical method, allowing the active components to grow directly on Cu mesh without extra pretreatments or binding agents. The synthesized catalyst exhibits approximately a 30 % increase in carbon monoxide oxidation activity at 100°C and a 60 % increase in toluene oxidation activity at 240°C compared to the Mn-free Cu mesh catalyst. We found that calcination in inert gases enhances interactions between Cu and Mn species, leading to more oxygen vacancies and adsorption sites for reactants. This investigation paves the way for fabricating multi-metal monolithic catalysts on metallic substrates.

Mixed-mode oscillations and chaos in a complex chemical reaction network involving heterogeneous catalysis.

The nonlinear dynamical behavior in a complex isothermal reaction network involving heterogeneous catalysis is studied. The method first determines the multiple steady states in the reaction network. This is followed by an analysis of bifurcation continuations to identify several kinds of bifurcations, including limit point, Bogdanov-Takens, generalized Hopf, period doubling, and generalized period doubling. Numerical simulations are performed around the period doubling and generalized period doubling bifurcations. Rich nonlinear behaviors are observed, including simple sustained oscillations, mixed-mode oscillations, non-mixed-mode chaotic oscillations, and mixed-mode chaotic oscillations. Concentration-time plots, 2D phase portraits, Poincaré maps, maximum Lyapunov exponents, frequency spectra, and cascade of bifurcations are reported. Period-doubling and period-adding routes leading to chaos are observed. Maximum Lyapunov exponents are positive for all the chaotic cases, but they are also positive for some non-chaotic orbits. This result diminishes the reliability of using maximum Lyapunov exponents as a tool for determining chaos in the network under study.

Polyoxometalates ionic liquids based magnetic nanocomposites as an efficient heterogeneous catalysts for oxidation of thiobenzoic acid and dibenzothiophene by employing RP-HPLC-UV

Polyoxometalates ionic liquids based magnetic nanocomposites as an efficient heterogeneous catalysts for oxidation of thiobenzoic acid and dibenzothiophene by employing RP-HPLC-UV