Optimal Reaction Conditions Research Articles

Nitrogen-doped mesoporous carbon as metal-free catalysts for the aerobic oxidation of alcohols

The selective oxidation of alcohols to carbonyl compounds is a crucial reaction in organic chemistry. In this study, we report the synthesis of nitrogen-doped mesoporous carbon material by hard template method using biomass derivative sucrose and melamine as carbon and nitrogen sources and silica sol as template agent. Using molecular oxygen as the oxidant, the obtained NC-900 exhibits excellent selectivity in the oxidation of primary alcohols to the corresponding aldehydes without generating over-oxidized acid. For example, under optimal reaction conditions, 4-methoxybenzyl alcohol is almost quantitatively converted to 4-methoxybenzaldehyde. The catalytic system showed robust tolerance to sensitive functional groups and demonstrated favorable reaction effects in gram-scale experiments and multi-step, one-pot reaction sequences. The catalyst was reused for 5 times, and its catalytic activity did not decrease significantly. Hammett correlation studies indicated that the reaction favored substrates with electron-donating substituents. Characterization and experimental results indicate that the synergistic effect of graphitic N and mesoporous structure plays a pivotal role in enhancing the catalytic activity of NC-900 in this transformation. The mechanism study shows that the reaction involves free radical process.

Synthesis of novel isoxazole/dihydroisoxazole tethered β-lactam hybrids via regiospecific 1,3-dipolar cycloaddition methodology on 3-phenylthio-β-lactams

Tethering of two biologically active molecules in a single unit is considered as a captivating solution for the extension of existing antibiotics. β-Lactams which display a vast array of biological properties due to various ring substitutions continue to attract the attention of synthetic chemists. The incorporation of the ‘isoxazole’ nucleus in its appendage is known to enhance the properties of β-lactam compounds. Its inclusion in the compounds offers decreased toxicity, increased efficacy, and improved pharmacokinetics spectrum. In the reported work, we highlight the efficient use of 1,3-dipolar cycloaddition reaction to synthesize novel isoxazole/dihydroisoxazole ring-linked β-lactam hybrids using 3-propargyloxy-β-lactams/3-allyl-β-lactams as synthons. The methodology devised has been found to be highly regioselective and generalized for the selected substrates to provide a variety of novel hybrid compounds under elementary reaction conditions. The synthesized compounds have been well characterized by various spectroscopic techniques and optimized reaction conditions for both types of hybrid compounds have been studied.

Electrooxidative Thiocyanation of Hydroxy‐ and Alkoxybenzenes

We developed an original method for thiocyanation of hydroxy‐ and alkoxy‐substituted benzenes (including naturally occurring compounds) using electrogenerated thiocyanogen, (SCN)₂. The presence of zinc chloride as a Lewis acid significantly enhances reaction efficiency by activating thiocyanogen. Cyclic voltammetry of the reactants and their combinations was employed to optimize reaction conditions and investigate the proposed mechanisms. This method demonstrated broad synthetic utility, leading to mono‐ and bis‐thiocyanated arenes and various heterocycles with yields 36–97%. Notable products include the neuroprotective drug riluzole and precursors for the antiprotozoal drugs toltrazuril and ponazuril.

Domino Approach to Heterocycles-Based Unsymmetrical Triarylmethanes through Heteroannulation of 2-(2-Enynyl)-pyridines with Enaminones.

Herein, we report a copper-catalyzed protocol to access unsymmetrical triarylmethanes containing both indolizine and the chromone scaffolds in the same molecule via a 5-endo-dig cyclization of 2-(2-enynyl)-pyridines followed by reaction with 2-hydroxyaryl enaminones. A variety of 2-hydroxyaryl enaminones and 2-(2-enynyl)-pyridines were subjected to reaction under the optimal reaction conditions, and the respective triarylmethanes were obtained in good to excellent yields.

Electrochemical C-H Azidation and Diazidation of Anilines for the Synthesis of Aryl Azides and Diazides.

The increasing importance and need in many aspects have driven the rapid development of synthetic studies toward aryl azides. In this paper, electrochemical C-H azidation and diazidation of anilines have been developed using TMSN3 as an azide source. A range of functional groups can be tolerated under the optimized reaction conditions.

Solvent-free synthesis of diacylglycerols via enzymatic glycerolysis between edible oils and glycerol catalyzed by self-made immobilized lipase PS@LXTE-1000

Diglycerol (DAG) is a structural lipid with the functions to lower body fat accumulation and decrease serum triglyceride level. However, the enzymatic synthesis of DAG is limited by the high-efficient and economic lipases. In this paper, the immobilized lipase PS@LXTE-1000 was self-made by immobilizing the Pseudomomas cepacian lipase on to the hydrophobic microporous resin LXTE-1000. The results indicate that LXTE-1000 was a uniform mesoporous sphere with the mean diameter of 400 ​μm, pore size of 14.6 ​nm, pore volume of 0.5 ​cm3/g and surface area of 126.0 ​m2/g, showing superior structural properties for lipase immobilization. Under the optimal reaction conditions with the molar ratio of rapeseed oil to glycerol being 1:1, adding amount of immobilized lipase being 4%, reaction at 50 ​°C, the highest DAG content of 46.7% was achieved in 3 ​h via enzymatic glycerolysis catalyzed by LXTE-1000. After 7 cycles of reuse, the self-made LXTE-1000 could still retain 78.3% of its initial catalytic ability. Besides, LXTE-1000 was observed to facilitate the DAG production via glycerolysis reaction between glycerol with other seven edible oils including corn oil, sesame oil, peony seed oil, rice bran oil, peanut oil, soybean oil and flaxseed oil. Specifically, the glycerolysis reaction with sesame oil, peony seed oil and rice bran oil even led to the DAG content of 52.1%, 53.3% and 51.2%, respectively, Hence, this paper provide a novel strategy to produce high-efficient and economic immobilized lipases, which shows great potential in the green synthesis of functional lipids such as DAG.

Enhanced methylene blue degradation by graphene oxide-encapsulated nano zero-valent iron composites: Optimization, mechanistic insights, and environmental implications

Methylene blue (MB) in textile dye wastewater poses a significant environmental challenge due to its high chemical stability and resistance to biodegradation. This study investigates the use of a novel graphene oxide-encapsulated nano zero-valent iron (GO/nZVI) composite for the efficient and sustainable degradation of MB. The GO/nZVI composite was synthesized via hydrothermal co-precipitation and self-assembly methods and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Under optimized conditions, the composite achieved an impressive 99.99 % degradation of MB within 40 min, demonstrating substantial improvements in stability and reusability. The composite retained over 84.5 % of its catalytic activity after five cycles, underscoring its potential for practical wastewater treatment applications. The optimization of reaction conditions through response surface methodology (Box-Behnken design, BBD) facilitated the formation of a core-shell structure, which significantly enhanced electron transfer and radical generation, crucial for MB oxidation. Radical quenching experiments confirmed hydroxyl radicals (·OH) as the primary active species, and gas chromatography-mass spectrometry (GC-MS) analysis elucidated the degradation pathway. This study presents a scalable and environmentally friendly solution for the treatment of recalcitrant organic pollutants, marking a significant advancement in water purification technologies.

Anchoring Ni(II) bisacetylacetonate complex into CuS immobilized MOF for enhanced removal of tinidazole and metronidazole

Here in this study, a novel ternary CuS/HKUST‒1/Ni(acac)2 nano photocatalyst (CSHK‒Ni) was developed through a facile modification of HKUST‒1 MOF with Ni(acac)2 metal complex and by immobilizing CuS into the metal-organic framework (MOF). The incorporation of CuS, a narrow bandgap semiconductor, is anticipated to allow easy excitation by visible-light and improve the photocatalytic potential of the formulated catalyst which is validated by the decrease in the bandgap energy from 3.10 eV of pristine MOF to 2.19 eV. Moreover, the anchoring of the metal complex improves the light harvesting behavior by increased conjugation. Photoluminescence studies provided evidence of the effective separation of the photoinduced charge-carriers, reducing the rate of recombination and enhancing the photocatalytic potential of the CSHK‒Ni nanocomposite. The engineered catalyst displayed remarkable efficiency in the degradation of nitroimidazole containing antibiotics, Tinidazole (TNZ) and Metronidazole (MTZ), via H2O2 assisted AOP achieving a maximum photocatalytic efficiency of 95.87 ± 1.64% and 97.95 ± 1.33% in just 30 min under irradiation of visible light at optimum reaction conditions. The possible degradation pathway was elucidated based on the identification of ROS and degradation intermediates via HR‒LCMS and quenching experiments. Meanwhile, the chemical oxygen demand (COD) and total organic carbon (TOC) removal were also examined, encompassing the discussing of various aspects including reaction conditions, influence of various oxidizing agents, competing species and dissolved organic substrates present in the wastewater, marking the novelty of the study. This research elucidated the role of the CSHK‒Ni nanocomposite as an interesting photocatalyst in the elimination of emerging nitroimidazole containing pharmaceutical pollutant under visible-light exposure, presenting an exciting novel avenue for a cleaner and greener environment in the days to come.

Photocatalytic Methanol Dehydrogenation Promoted Synergistically by Atomically Dispersed Pd and Clustered Pd.

Supported metal in the form of single atoms, clusters, and particles can individually or jointly affect the activity of supported heterogeneous catalysts. While the individual contribution of the supported metal to the overall activity of supported photocatalysts has been identified, the joint activity of mixed metal species is overlooked because of their different photoelectric properties. Here, atomically dispersed Pd (Pd1) and Pd clusters are loaded onto CdS, serving as oxidation and reduction sites for methanol dehydrogenation. The Pd1 substitutes Cd2+, forming hole-trapping states for methanol oxidation and assisting the dispersion of photodeposited Pd clusters. Therefore, methanol dehydrogenation on CdS with supported Pd1 and Pd clusters exhibits the highest turnover frequency of 1.14 s-1 based on the Pd content and affords H2 and HCHO with a similar apparent quantum yield of 87 ± 1% at 452 nm under optimized reaction conditions. This work highlights the synergistic catalysis of supported metal for improved photocatalytic activity.

Treatment of brominated epoxy resin waste in subcritical dimethylformamide wastewater: Upcycling of brominated epoxy resin and dimethylformamide degradation

The debromination and upcycling of brominated epoxy resin (BER) waste is important for the e-waste treatment, while the degradation and removal of N, N-dimethylformamide (DMF) is the critical step for the DMF wastewater treatment. In this study, a co-treatment strategy was proposed for the BER waste and DMF wastewater by the subcritical water process. The co-treatment was carried out using subcritical DMF wastewater (SDW) as the reaction medium. The results showed a significantly synergistic effect between the BER conversion and DMF degradation in the SDW process. The optimal reaction conditions were as follows: reaction temperature of 300 °C, solid-to-liquid ratio of 1:15 g/mL, DMF wastewater of 30000 mg/L and reaction time of 60 min. Under the optimal reaction conditions, the debromination ratio of the BER was 98.57 %, the degradation ratio of the DMF reached 99.59 %, and phenolic substances with a purity of 86.61 % were recovered. The formation of HBr from the debromination of the BER was the most significant factor affecting the pH of the system, which had a noticeable impact on the degradation of the DMF. The main degradation products of the DMF were dimethylamine (DMA), methylamine (MA), NH3, NH4+, and CO2. The products degraded from the DMF could significantly promote the debromination and conversion of the BER. Life cycle assessment (LCA) analysis showed that the SDW process had low CO2 emissions. It is believed that the SDW process proposed in this study is an efficient technology for the synergistic treatment of the BER waste and DMF wastewater.

Fabrication of Laminated Electrospun Fire˗Resistant Phosphorylated Poly(Vinylalcohol) Membrane for Enhanced Firefighter Safety

AbstractThe current study focuses on the creation of breathable and fire˗retardant fibrous membranes using phosphorylated poly(vinylalcohol) (PPVA) via the electrospinning method, with a specific interest in their application for structural firefighter clothing. Poly(vinylalcohol) (PVA) was phosphorylated to enhance its inherent flame resistance. Optimization of reaction conditions, including time and temperature, was conducted to achieve a solution suitable for electrospinning. The flame resistance of PPVA was confirmed through vertical flammability tests, with thermogravimetric analysis indicating a significant increase in carbonaceous char formation during PPVA decomposition compared to unmodified PVA. The limiting oxygen index also exhibited a notable increase from PVA to PPVA. Furthermore, the study established optimal operating conditions for producing uniform fibers, considering parameters such as polymer concentration, feed rate, tip to collector distance, and applied potential difference. The PPVA membrane demonstrated superior water vapor transmission rates compared to PVA, indicating enhanced breathability. The entire fabrication process utilized an environmentally friendly water‐based solvent. Additionally, a moisture‐cum‐thermal barrier layer (MCTB) was developed by laminating the PPVA fibrous membranes with microporous polytetrafluoroethylene and further with needle punch‐spunlaced OPAN fabric. Experimental assessments of the MCTB layer revealed satisfactory breathability and thermal performance, surpassing the standard requirements of 35 cal/cm2 for structural firefighting configuration.

Identification and characterization of Lacticaseibacillus rhamnosus HP-B1083-derived β-glucuronidase and its application for baicalin biotransformation

Baicalein, showing higher bioavailability and stronger pharmacological activity, can be obtained via a β-glucuronidase (GUS)-catalyzed transformation of baicalein 7-O-β-D-glucuronide (baicalin). Recently, we have found that the fermentation broth of Lacticaseibacillus rhamnosus HP-B1083 can efficiently convert baicalin to baicalein. In this study, the L. rhamnosus HP-B1083-derived enzyme involved in baicalin biotransformation was identified and characterized. First, the LruidA gene, encoding the responsible enzyme, was cloned and sequenced. Sequence analysis revealed that the deduced enzyme (designated as LrUidA) belonged to the glycosyl hydrolase family 2. The recombinant LrUidA was expressed and purified for characterization. LrUidA had a molecular weight of 70 kDa, with an optimal temperature of 50 °C and pH 4.5. Although LrUidA was susceptible to temperature, it possessed a relative pH stability. Its Michaelis–Menten constant, maximum reaction velocity and catalytic constant values were 9.710 mM, 13.08 mM/min/mg, and 14.95 s−1, respectively. Site-directed mutagenesis experiment results demonstrated that the enzyme reaction uses side chains of E509 and E415 to hydrolyze the glycosidic bond of baicalin and involves three negatively charged residues, E450, D451, and D452, respectively. Surprisingly, biotransformation was performed under optimized reaction conditions by incubating the purified enzyme with 0.1 % baicalin for 4 h, resulting in a considerable conversion ratio of 99 %. Altogether, our findings provide insights into the properties of L. rhamnosus HP-B1083-derived enzyme and expand our understanding regarding using GUS for the industrial production of baicalein.

Metal-Organic Frameworks as Electrode Materials for Lithium-Ion Battery

Over recent decades, Metal-Organic Frameworks (MOFs) have distinguished themselves as a unique class of porous materials due to their adaptable surface and structural properties. This versatility has made MOFs highly relevant across various fields, including drug delivery, gas separation, catalysis, and sensor technology. Additionally, their conductive properties have made them promising candidates for use in energy storage systems like high-energy-density batteries and supercapacitors. MOFs are particularly noted for their role in the development of rechargeable lithium-ion batteries (LIBs) and supercapacitors, where they serve as both anode and cathode materials. The ability to fine-tune MOFs at a molecular level allows for precise control over their structure and chemistry, enhancing their functionality in energy storage applications. This control facilitates superior electronic and ionic transport within MOFs, which is critical during the charging and discharging cycles of LIBs. This review delves into the various synthetic methods used to develop specific MOF structures, focusing on their implementation within LIBs to improve cyclic stability and discharge capacity. Recent advancements in MOF technology as anode and cathode materials are explored, providing insights into how these developments can optimize reaction conditions and design choices within the battery development community and broader electrochemical energy storage sectors. The aim is to highlight how MOFs’ inherent characteristics can be leveraged to enhance the performance and efficiency of energy storage devices.

Impact of Surface Modification on the Oxidation of Linear Aliphatic Alcohols by Vanadium Complexes Supported on Merrifield Resin with Mixed Functionality Ligands

AbstractTwo oxidovanadium(IV) complexes [VO(xbp‐sc)] (1) and [VO(xbp‐tc)] (2) were prepared using hydrazine‐ether mixed functionality ligands Hxbp‐sc (I) and Hxbp‐tc (II), respectively. Complexes 1 and 2 were carefully grafted separately into imidazole‐modified chloromethylated polystyrene (Ps−Im) and unmodified chloromethylated polystyrene (PS−Cl) beads. Successfully anchored vanadium complexes Ps−Im‐[VO(xbp‐sc)] (3), Ps−Im‐[VO(xbp‐tc)] (4), Ps‐[VO(xbp‐sc)] (5), and Ps‐[VO(xbp‐tc)] (6) were tested for their catalytic potential towards the oxidation of aliphatic alcohols in the presence of hydrogen peroxide. Polymer‐grafted catalysts display excellent substrate conversion compared to most recent reports and good recyclability up to three cycles without losing much reactivity. High TOF values in the range of 183–591 h−1 are observed for the supported catalysts 3–6. The highest substrate conversion is observed for ethanol (63–97 %) under the optimized reaction conditions. Mainly, better substrate conversion is obtained with imidazole‐modified polymer beads grafted catalysts 3 and 4 than those grafted on unmodified polymer beads (5 and 6). Moreover, catalysts with the semicarbazide group in their ligand framework (3 and 5) show better reactivity towards alcohol with fewer carbon atoms. On the contrary, alcohols with longer carbon chains oxidize more easily in the presence of the catalyst with thiosemicarbazide frameworks (4 and 6).

Biotransformation of Cinnamic Acid, Cinnamaldehyde, Furfural and Epoxidation of Cyclohexene by Plant Catalase

Background: Epoxides are widely useful in various fields such as pharmaceuticals, pesticides, cosmetics, polymer synthesis, fragrance compounds, and food additives. However, the synthesis of epoxides involves heavy metal catalysts and toxic, unstable organic catalysts which causes serious environmental and safety concerns. In recent years, biocatalysts have received a great deal of interest in the synthesis of olefin-derived epoxides due to their mild reaction conditions, environmental friendliness, good selectivity, and sustainability. This study focuses on catalases as a biocatalyst for potential epoxidation reactions of olefins. Objective:: To determine the possibility of using biocatalyst catalase from a novel source Sechium edule (squash) for epoxidation of olefins in the presence of H2O2. Methods: UV-Vis spectrophotometer was used to monitor the formation of epoxide from substrates- cyclohexene, cinnamic acid, cinnamaldehyde, furfural in acetonitrile solvent and a suitable aliquot of the enzyme solution in the presence of H2O2. The products formed were analyzed using FTIR and GC-MS. For the immobilized enzyme, chitosan beads activated with TPP were used in place of the enzyme and a similar procedure was followed for the analysis. Results: Four different olefin substrates (cyclohexene, cinnamic acid, cinnamaldehyde, and furfural) were selected to study the catalysis reaction of epoxidation by the catalase enzyme. The course of the epoxidation was monitored by UV-Vis, FTIR, and GC-MS methods. However, under optimized reaction conditions and spectral analysis, further confirmed by GC-MS, data showed only epoxide formation from cyclohexene. CAT completely catalyzed other olefins like furfural, cinnamic acid, and cinnamaldehyde into its degraded products biochemically. Therefore, cyclohexene was selected for further immobilization studies and the identified metabolites of olefins and their degradation mechanism. Major biodegradation products of cinnamic acid were found to be styrene( m/z 104.0) and benzaldehyde(m/z 105.0). GC-MS data of biotransformation of cinnamaldehyde, identified 2,4 dimethyl benzaldehyde(m/z 133) as the main product. The catalytic biotransformation of furfural investigated by GC-MS data identified 2,5 dimethyl benzaldehyde (m/z 133), dodecanol (m/z 181) and Pentanoic acid, 5 hydroxy, 2,4 dibutyl phenyl ester(m/z 306) as the major product. Three major oxidized products were detected in GC-MS data from the epoxidation of cyclohexene viz., cyclohexane diol(m/z 116), cyclohexene epoxide-1-ol(m/z 110), cyclohexene epoxide-1-one(m/z 110). Conclusion: In this investigation, catalase purified from Sechium edule(squash) was developed as an efficient catalytic tool for the biotransformation of olefins and selective epoxidation of cyclohexene. Under optimized conditions, the experimental results revealed the main products found in cinnamaldehyde as benzaldehyde (m/z 133.0) and cinnamic acid as benzaldehyde (m/z 133), styrene (m/z 104.0) and benzoic acid (m/z 122.0), while the data from furfural oxidation could not be justified from previous studies. The optimal concentration of CH3CN solvent for cyclohexene epoxidation was found to be 4 mM. Enzymatic characterization of free and immobilized catalase on chitosan was investigated using cyclohexene as a variable substrate and found to be 0.017 mM, 83.33 μmol/min for Km and Vmax values, pH 6.8 and 30˚C for free CAT and 0.03 mM, 200 μmol/min, pH 7.6 and 35˚C for immobilized one. Immobilization increases the thermal stability of the CAT and changes the pH to alkalinity. The possible oxidation of cyclohexene was deduced as the radical chain mechanism for the generation of epoxide with the key products obtained as cyclohexane diol(m/z 116), cyclohexene epoxide-1-ol(m/z 110) and cyclohexene epoxide-1-one(m/z 110). The reusability of the biocatalytic tool opens up the opportunity to reduce the cost of various catalytic reactions. Further studies can focus on the separation and advancement of epoxide yields, improved immobilization strategy for maximum repetitive cycles, and chemo-enzymatic epoxidation on biological olefins.

Fabrication and Electrochemical Evaluation of Cobalt Sulfide for Energy Storage Application

This work significantly contributes to this field by focusing on the synthesis and application of cobalt sulfide (CoS) as an innovative electrode material. Utilizing a straightforward hydrothermal process, we successfully synthesized CoS, emphasizing the optimization of reaction conditions. This included a detailed exploration of different solvents, primarily water and ethanol, to determine their impact on the final product. A comprehensive characterization of these parameters was conducted, shedding light on their crucial role in the material’s performance. The electrochemical attributes of the CoS electrodes were tested using cyclic voltammetry and galvanostatic charge discharge techniques. These investigations revealed that the CoS variant labeled as CoS_1 and CoS_2 demonstrated improved electrochemical properties. CoS_2 exhibited a specific capacitance of 360.0 Fg−1 at current load of 1.0 A/g. This superior performance of CoS_2 is largely attributed to its unique structural properties. The porous nature of CoS_2, coupled with its high surface area, plays a crucial role in enhancing its electrochemical capabilities. Furthermore, the material displayed impressive cyclic stability, maintaining up to 82.0% of its original capacitance. This level of durability highlights its suitability for long-term applications in energy storage devices. When tested in a three-electrode assembly, both CoS_1 and CoS_2 electrodes exhibited promising results. However, the distinct advantages of CoS_2, particularly in terms of capacitance and stability, underscore its potential as a superior candidate for energy storage applications.

Effect of Catalyst Concentration on Reaction Rate in Organic Synthesis in Kenya

Purpose: The aim of the study was to assess the effect of catalyst concentration on reaction rate in organic synthesis in Kenya. Methodology: This study adopted a desk methodology. A desk study research design is commonly known as secondary data collection. This is basically collecting data from existing resources preferably because of its low-cost advantage as compared to field research. Our current study looked into already published studies and reports as the data was easily accessed through online journals and libraries. Findings: Increased catalyst concentration typically enhances the reaction rate by providing more active sites for the reactants to interact, thereby accelerating the reaction process. This phenomenon follows the principles of collision theory, which states that a higher concentration of catalyst molecules leads to more frequent collisions with reactant molecules, thus increasing the likelihood of successful reactions. Studies have shown that in many organic syntheses, an optimal catalyst concentration exists where the reaction rate is maximized; beyond this point, further increases in catalyst concentration may result in negligible improvements or even adverse effects due to catalyst aggregation or inhibition. Additionally, the nature of the catalyst, its dispersion in the reaction medium, and the specific reaction mechanism all play significant roles in determining the overall impact of catalyst concentration on reaction kinetics. Consequently, fine-tuning the catalyst concentration is essential for optimizing reaction conditions, improving yields, and achieving desired product selectivity in organic synthesis. Implications to Theory, Practice and Policy: Transition state theory, collision theory and michaelis menten kinetics may be used to anchor future studies on assessing effect of catalyst concentration on reaction rate in organic synthesis in Kenya. Practical guidelines are crucial for optimizing catalyst concentration in specific reaction types and industrial settings. Establishing regulatory frameworks that incentivize efficient catalyst concentration practices within industries is imperative.

Performance of mesoporous ceria supported Ru catalysts for oxidative degradation of aqueous solution of plastic monomer bisphenol A in a fixed bed flow reactor: Structure-activity insights, optimization of reaction conditions, kinetics, catalyst stability, and characterization

One of the important defects is the oxygen vacancy on metal oxide surfaces, and the defects function as the active sites in different catalytic reactions. Herein, Ru/CeO2-rod and Ru/CeO2-cube catalysts were prepared via the ESI method, and CeO2-rod and CeO2-cube supports were synthesized by hydrothermal processes. The activity of these catalysts was tested in a high-pressure fixed-bed reactor, and the oxidative degradation of industrial organic raffinate containing the plastic chemical bisphenol A (BPA) was compared with their oxygen vacancy concentration estimated after calcination. The Ru/CeO2-rod catalyst showed higher catalytic activity with 90 % BPA conversion at 453 K, 30 bar, 0.5 % Ru metal content, 15 O2 to BPA molar ratio, and 2 g−1.h−1 BPA feed weight hourly space velocity (WHSV). In contrast, 80 % BPA degradation was achieved using the Ru/CeO2-cube catalyst under similar reaction conditions. The higher oxygen vacancy concentration and the higher interfacial surface area between metal and the support of the CeO2-rod supported Ru catalyst triggered the higher BPA degradation at low oxidation conditions. Besides, the atomic ratio, Ce3+/Ce4+, is lower in the Ru/CeO2-rod catalyst than that of the Ru/CeO2-cube catalyst, indicating the higher Ce4+ available in the catalyst, leading to the higher degradation of BPA. Moreover, the Ru/CeO2-rod catalyst possesses {111} planes that boost the generation of energetic Ru to improve the pursuit of the catalyst. The Weisz-Prater modulus and Thiele modulus values indicated that the surface reaction is the rate limitation step and there is no diffusion limitation. TEM, HRTEM, XPS, Raman, H2-TPR, XRD, CO chemisorption and BET surface area analyzers were used to characterize the catalysts.

Enzymatic synthesis of structured lipids rich in α‐linolenic acid: impacts of triacylglycerol profile on physicochemical characteristics

SummaryMedium‐ and long‐chain triacylglycerols rich in α‐linolenic acid (ALA‐MLCT) are a kind of functional structural lipids that provide ω‐3 fatty acid and faster energy supply to human body. To improve the functional and nutritional properties of vegetable oils, we proposed an effective strategy for the synthesis of ALA‐MLCT by enzymatic interesterification of coconut oil and flaxseed oil. Lipase UM1 exhibited the highest interesterification activity compared with commercial Lipozyme RM IM, Lipozyme TL IM and Novozym 435. MLCT (76.59%) and ALA‐MLCT (45.03%) were obtained under the optimum reaction conditions: substrate molar ratio (coconut oil/flaxseed oil) 1:1, temperature 40 °C, Lipase UM1 loading 25 U g‑1. Furthermore, we identified 14 characteristic triacylglycerols molecules between enzymatic interesterification and physical blend by orthogonal partial least squares‐discrimination analysis (OPLS‐DA) model. The content of triunsaturated type triacylglycerols in enzymatic interesterification product (11.29%) was lower than that of physical blend (36.25%). Enzymatic interesterification product had lower solid fat content and 2.44 times oxidative stability than physical blend. These findings provide an effective strategy for the synthesis of functional ALA‐MLCT and advance the understanding of the relationship between triacylglycerols composition and physicochemical characteristics.

Selective oxidation of methane to C2+ products over Au-CeO2 by photon-phonon co-driven catalysis

Direct methane conversion to high-value chemicals under mild conditions is attractive yet challenging due to the inertness of methane and the high reactivity of valuable products. This work presents an efficient and selective strategy to achieve direct methane conversion through the oxidative coupling of methane over a visible-responsive Au-loaded CeO2 by photon-phonon co-driven catalysis. A record-high ethane yield of 755 μmol h−1 (15,100 μmol g−1 h−1) and selectivity of 93% are achieved under optimised reaction conditions, corresponding to an apparent quantum efficiency of 12% at 365 nm. Moreover, the high activity of the photocatalyst can be maintained for at least 120 h without noticeable decay. The pre-treatment of the catalyst at relatively high temperatures introduces oxygen vacancies, which improves oxygen adsorption and activation. Furthermore, Au, serving as a hole acceptor, facilitates charge separation, inhibits overoxidation and promotes the C-C coupling reaction. All these enhance photon efficiency and product yield.