Easy Catalyst Research Articles

Fabrications of electrochemical sensors based on carbon paste electrode for vitamin detection in real samples

This review article examines some advancements in electrochemical sensors for vitamin detection in the past few decades. Vitamins are micronutrients found in natural foods essential for maintaining good health. Most vitamins cannot be synthesized by a body and must be obtained externally from natural food. Vitamins make a class of organic chemicals that shortage can cause various ailments and diseases, and consumption can become harmful if it exceeds the usually needed level. Because of these factors, vitamin detection has become highly significant and sparked interest over the past few decades. The electrochemical sensors function on the concept of electro­chemical activity of practically all vitamins. This implies that concentrations of vitamins in the electrolyte may be detected by measuring the amounts of current generated at certain potentials by their oxidation and reduction at the working electrode surface. Voltammetric methods are superior to other methods because they are cheaper and show sharp sensitivity with faster analysis speed. The carbon-based electrodes, in particular carbon paste electrodes (CPE), have significant advantages like easier catalyst incorpo­ration, surface renewability, and expanded potential windows with lower ohmic resistance. This review goes into detail about several electro­chemical sensors involving CPE as the working electrode and its utilization to detect water- and fat-soluble vitamins.

3D‐Printed Structured Reactor with Integrated Single‐Atom Catalyst Film for Hydrogenation

AbstractStructured catalytic reactors are gaining considerable attention for integrated chemical synthesis because they offer enhanced mass transfer and easy catalyst recovery. In this paper, a new, cost‐effective design strategy that combines 3D printing and single‐atom catalysis is presented, enabling the construction of an integrated mixer‐based reactor insert, coated with a thin single‐atom catalytic layer. The material has been characterized from the nano to the macro scale to unlock structure‐property relationships. The performance of the catalyst structure was evaluated via hydrogenation of two model compounds used in the flavorings and fragrances industry. The structured catalytic reactor was active, selective, and reusable several times without apparent drop in performance. This immobilized catalyst system removes the need for catalyst separation post‐reaction, and enables modern synthesis options catalyzed over atomically‐precise nanomaterials.

Heterogeneous Catalyzed Biodiesel Production Using Cosolvent: A Mini Review

Biodiesel is gaining recognition as a good replacement for typical diesel owing to its renewability, sustainability, and eco-friendly nature. Transesterification is the leading route for biodiesel generation, which occurs during homogeneous/heterogeneous/enzymatic catalysis. Besides this, the usage of heterogeneous catalysts is considered more advantageous over homogeneous catalysts due to the easy catalyst recovery. Consequently, numerous heterogeneous catalysts have been synthesized from multiple sources with the intention of making the manufacturing process more efficient and cost-effective. Alongside this, numerous researchers have attempted to improve the biodiesel yield using heterogeneous catalysts by introducing cosolvents, such that phase limitation between oil and alcohol can be minimized. This short review is aimed at examining the investigations performed to date on heterogeneously catalyzed biodiesel generation in the presence of different cosolvents. It encompasses the techniques for heterogeneous catalyst synthesis, reported in the literature available for heterogeneous catalyzed biodiesel generation using cosolvents and their effects. It also suggests that the application of cosolvent in heterogeneously catalyzed three-phase systems substantially reduces the mass transfer limitation between alcohol and oil phases, which leads to enhancements in biodiesel yield along with reductions in values of optimized parameters, with catalyst weight ranges from 1 to 15 wt. %, and alcohol/oil ratio ranges from 5.5 to 20. The reaction time for getting the maximum conversion ranges from 10 to 600 min in the presence of different cosolvents. Alongside this, most of the time, the biodiesel yield remained above 90% in the presence of cosolvents.

Reusable Nano Catalysed Synthesis of Heterocycles: An Overview

AbstractThe field of reusable nano‐catalysts has grown rapidly over the last decade. Recently, transition metal catalysed organic reactions have attracted considerable interest from the pharmaceutical and organic chemistry fields. Synthetic procedures based on such heterogeneous nanocatalysts are easier, less expensive, non‐toxic, and eco‐friendly, producing only the most desirable products in higher yields and allowing for easy catalyst separation. Heterogeneous nano‐catalysts were highly preferred over homogeneous catalysts for the synthesis of heterocyclic compounds due to their effective separation processes for both products and catalysts. According to recent studies, nanoparticles (NPs) are commonly used as a heterogeneous catalyst in the production of heterocyclic compounds. Heterogeneous catalysts are widely used in a variety of organic reactions due to their high surface‐to‐volume ratio. Most importantly, after the reaction is complete, easy magnetic separation of the catalyst minimises the requirement for catalyst filtration. Additionally, magnetic NPs, particularly supported magnetic nanocatalysts, have garnered considerable interest in both academic and industrial research due to their effectiveness as alternatives to traditional materials, their ease of separation via an external magnet, and their high degree of chemical stability in a variety of organic and inorganic solvents. To reach its depth, this review is focused on the most recent examples, their preparation, synthetic strategies and recycling studies of highly excited catalytic systems used for the synthesis of heterocyclic compounds.

Fe3O4@RB@LDH: Efficient and Recyclable Photocatalyst Visible‐Light Mediated Synthesis of Pyran and Pyrrolidinone Derivatives and Their Anti‐Microbial Activities

AbstractSelective and high yielding synthesis of pyran and pyrrolidinone derivatives through a magnetic layered double hydroxide (LDH) visible light photocatalyst (VLPC)‐promoted reaction is reported. The catalyst was prepared and characterized by various analytical techniques. Since it is magnetic the prepared catalyst could be easily separated from the reaction mixture by using an external magnet. The advantages of this synthetic protocol are good to excellent yields, short reaction times, easy catalyst recovery and recyclability. Also, in vitro antibacterial screening of pyrrolidinone derivative was studied against gram‐positive Bacillus cereus (B. cereus), gram‐negative bacteria Escherichia coli (E. coli) and S. aureus. Compound 9 f [Methyl‐2‐(3‐chlorophenyl)‐2,5‐dihydro‐4‐hydroxy‐5‐oxo‐1‐phenyl‐1H‐pyrrole‐3‐carboxylate] exhibited the maximum activity against all the bacteria tested in the experiment.

A green, an efficient and viable approach for the synthesis of novel 4H-pyran-indolin-2-one derivatives via a one-pot reaction by grinding method

• A simplistic and rapid protocol using Grinding method. • Synthesis of novel 4 H -pyran-indolin-2-one derivatives. • One-pot/two-component and solvent-free protocol. • Excellent yields (89 to 98%) in short reaction times (< 10 min). An highly efficient and green approach for the synthesis of novel 4 H -pyran-indolin-2-one analogues by the reaction of various isatins with 4 H -pyran-4-one using NaHCO 3 as catalyst under solvent-free, and grinding conditions at room temperature has been showed with good to excellent product yields (89-98%). All the synthesized target compounds has been categorized by various spectroscopic techniques ( 1 H NMR, 13 C NMR, HRMS and FT-IR). This novel protocol has several benefit of mild reaction condition, normal grinding, easy available catalyst, economy, environmentl-friendly, short reaction times (≤ 5 minutes), excellent product yields, and absence of any tedious workup.

A hybrid system bases on silica-alumina and Keggin heteropolyacids as catalyst in the suitable 2-(2-furyl)-chromones and chromanones synthesis

Molybdophosphoric acid/silica-alumina composites are synthesized a through a process described, in which the heteropolyacid was impregnated on different silica-aluminas, obtained by sol-gel. Three different techniques were used to prepare the samples. The catalysts were prepared by incipient wetness impregnation and different thermal treatments were applied. The hybrid systems were characterized by using SBET, DRX, XRD and acidity measurements. The catalytic activity of these materials was tested in the solvent-free cyclization of 1-(2-hydroxyphenyl)-3-(2-furyl)-1,3-propanedione to 2-(2-furyl)-chromones. The transformation gives very good yields of product, free of secondary products. Environmental benign procedure, and easy catalyst separation, is relevant features of this methodology. In this way the catalyst can be used and reused six cycles without loss of catalytic activity. The most active catalyst was also used in the solvent-free cyclization of 1-(2-hydroxyphenyl)-3-(2-furyl)-2-propen-1-one and the methodology can be extended to the synthesis of other 2-(2-(furyl)-chromones and chromanones. The green context for this new procedure was confirmed by greenmetrics parameters.

Selective CO2 hydrogenation reaction using recyclable TiO2 supported Ruthenium nanoparticles

Stable, well dispersed and agglomeration free Ru metal doped TiO2 nanoparticles were produced by a sol gel method (with and without ionic liquid reaction medium). Such unique physiochemical properties of Ru-TiO2-IL catalyst were utilized as catalysts for CO2 hydrogenation reaction in task specific ionic liquid medium. Low catalysts loading, moisture/air stability, high selectivity, easy catalyst synthesis protocol as well as stress-free reaction condition along with 5 times catalysts recycling are the major outcomes of the proposed report. Copyright © 2017 VBRI Press.

Ring‐Closing Metathesis of Aliphatic Ethers and Esterification of Terpene Alcohols Catalyzed by Functionalized Biochar

AbstractFunctionalized biochars, renewable carbon materials prepared from waste biomass, can catalyze transformations of a range of oxygen‐containing substrates via hydrogen‐bonding interactions. Good conversions (up to 75.2 %) to different O‐heterocycles are obtained from ring‐closing C−O/C−O metathesis reactions of different aliphatic ethers under optimized conditions using this heterogeneous, metal‐free, and easy separable catalyst. The diversity in the sorts of O‐containing feedstocks is further demonstrated by the utilization of functionalized biochar to promote the esterification of terpene alcohols, an important reaction in food and flavor industries. Under the optimized conditions, full conversions to various terpene esters are obtained. Moreover, both of the reactions studied herein are performed under neat conditions, thus increasing the overall sustainability of the process described.

Ultrasound promoted environmentally benign, highly efficient, and chemoselective N-tert-butyloxycarbonylation of amines by reusable sulfated polyborate

The sulfated polyborate catalyzed an efficient and chemoselective N-tert-butyloxycarbonylation of amines under ultrasonic irradiation is developed. A broad substrate scope has been demonstrated for N-Boc protection of various primary/secondary amines. It allows converting several aliphatic/aryl/heteroaryl amines, amino alcohol, aminoester, and chiral amines to their N-Boc-protected derivatives under solvent-free conditions with excellent yields. The protocol has several advantages such as easy catalyst, and product isolation, short reaction time, excellent yields, outstanding chemoselectivity, and catalyst recyclability, among others. This makes the process practicable, economical, and environmentally benign.

Hydrogen Peroxide Versus Hydrogen Generation at Bipolar Pd/Au Nano-catalysts Grown into an Intrinsically Microporous Polyamine (PIM-EA-TB)

Binding of PdCl42− into the polymer of intrinsic microporosity PIM-EA-TB (on a Nylon mesh substrate) followed by borohydride reduction leads to uncapped Pd(0) nano-catalysts with typically 3.2 ± 0.2 nm diameter embedded within the microporous polymer host structure. Spontaneous reaction of Pd(0) with formic acid and oxygen is shown to result in the competing formation of (i) hydrogen peroxide (at low formic acid concentration in air; with optimum H2O2 yield at 2 mM HCOOH), (ii) water, or (iii) hydrogen (at higher formic acid concentration or under argon). Next, a spontaneous electroless gold deposition process is employed to attach gold (typically 10- to 35-nm diameter) to the nano-palladium in PIM-EA-TB to give an order of magnitude enhanced production of H2O2 with high yields even at higher HCOOH concentration (suppressing hydrogen evolution). Pd and Au work hand-in-hand as bipolar electrocatalysts. A Clark probe method is developed to assess the catalyst efficiency (based on competing oxygen removal and hydrogen production) and a mass spectrometry method is developed to monitor/optimise the rate of production of hydrogen peroxide. Heterogenised Pd/Au@PIM-EA-TB catalysts are effective and allow easy catalyst recovery and reuse for hydrogen peroxide production.Graphical abstract

Recent progress of electrocatalysts for hydrogen proton exchange membrane fuel cells

Due to stringent environmental regulations and the limited resources of fossil-based fuels, there is an urgent demand for clean and eco-friendly energy conversion devices. These criteria appear to be met by hydrogen proton exchange membrane fuel cells (PEMFCs). PEMFCs have attracted tremendous attention on account of their excellent performance with tunable operability and good portability. Nonetheless, their practical applications are hugely influenced by the scarcity and high cost of platinum (Pt) used as electrocatalysts at both cathode and anode. Pt is also susceptible to easy catalyst poisoning. Herein, this paper reviews the progress of the research regarding the development of electrocatalysts practically used in hydrogen PEMFCs, where the corner-stone reactions are cathodic oxygen reduction reaction (ORR) and anodic hydrogen oxidation reaction (HOR). To reduce the costs of PEMFCs, lessening or eliminating the use of Pt is of prime importance. For current and forthcoming laboratory/large-scale PEMFCs, there is much interest in developing substitute catalysts based on cheaper materials. As such are non-platinum (non-Pt), non-platinum group metals (non-PGMs), metal oxides, and non-metal electrocatalysts. Hence, high-performance, state-of-the-art, and novel structured electrocatalysts as replacements for Pt are needed.

Sulfonic Acid-Functionalized Inorganic Materials as Efficient Catalysts in Various Applications: A Minireview

Acid catalysis is widely used in the chemical industry, and nowadays many efforts are being focused on replacing the more common homogeneous catalysts with heterogeneous ones in order to make greener the industrial processes. In this perspective, sulfonic solid acid materials represent a valid alternative to the homogenous mineral acid in several acid catalyzed reactions. In this minireview, an overview of the recent advances on the preparation, stability and application of these materials is reported. Special attention is addressed to the sustainability of the considered processes, starting from the catalyst’s preparation, the use of green solvents and reducing the possible reaction steps. Ways to tackle the main drawback represented by easy leaching of acid groups are described. For an easy catalyst recovery, the use of a magnetic core in a catalyst particle, with the related synthetic approaches, is also illustrated. Finally, a section is dedicated to the principal characterization techniques to identify the structural properties of the catalysts.

Palladium(II) and platinum(II) based S^N^S and Se^N^Se pincer complexes as catalysts for CO2 hydrogenation and N-formylation of diethylamine to diethylformamide

In this study, we report newly synthesized S^N^S and Se^N^Se tridentate platinum(II) and palladium(II) pincer complexes. These complexes have been evaluated as pre-catalysts in the hydrogenation of carbon dioxide to formate under basic conditions. These new molecular catalysts proved to be active in forming industrially valuable chemical intermediates like formate and diethylformamide from CO2. The complexes are soluble in THF and insoluble in water enabling easy catalyst recovery from a biphasic mixture of THF/water solvent system after catalysis. The pincer ligands provide a robust framework for stabilizing the active centers through various catalytic cycle steps. Palladium(II) catalysts yielded formate with TONs as high as 1881, while Se^N^Se platinum(II)-based catalysts (C1, C2, and C3) catalyzed the hydrogenation of CO2 to formate at TONs of 550, 421, and 1254, respectively, after 24 h. Similarly, the N-formylation of diethylamine using CO2 and H2 in the presence of C2 is effective with yields up to 71 %.

Composition-engineered LaCoO3-based monolithic catalysts for easily operational and robust peroxymonosulfate activation

Herein, we report for the first time the construction of perovskite oxide catalysts on monolithic supports for peroxymonosulfate (PMS) activation to eliminate organic pollutants in wastewater. Specifically, the commercially available porous alumina ceramic (PAC) was utilized as monolithic support, on which Ca − Ti co-modified LaCoO3 perovskites (L1−xCxC1−yTyO3) were successfully loaded through a simple, controllable, and reagent-saving “dripping − calcination” process. The resulting monolithic catalysts (L1−xCxC1−yTyO3@PAC) featured large sizes (cm-scale), highly open porous architectures, and compositionally favorable active components, by which easy catalyst recycling, rapid mass transfer of guest species, and high yet stable catalytic performance were harvested in PMS activation for degradation of the typical antibiotic pollutant metronidazole (MNZ). By optimizing the introduction amount of Ca and Ti, the resulting L0.8C0.2C0.4T0.6O3@PAC showed a high turnover frequency (TOF) value of 12.6 min−1 for MNZ with a low cobalt leaching amount of 0.203 mg L−1, which were significantly superior to the unmodified catalyst LCO3@PAC (TOF: 7.9 min−1; cobalt leaching: 1.71 mg L−1). Roles of Ca and Ti modifiers in the LaCoO3-based monolithic catalyst, degradation pathway of MNZ, and SO4−•/1O2 dominated catalytic mechanism were investigated and elucidated. Our work provides a promising avenue for rational design of low-cost, easily operational, and robust monolithic catalysts toward PMS activation for large-scale environmental remediation.

The novel acid-base magnetic recyclable catalyst prepared through carbon disulfide trapping process: Applied for green, one-pot, and efficient synthesis of 2,3-dihydroquinazolin-4 (1H) -ones and bis(indolyl)methanes in large-scale

• The synthesis of magnetic acid–base cooperativity catalyst through novel, facile and efficient method. • Synthesis of substituted dihydroquinazolinones and bis(indolyl)methanes with excellent yields in mild and green reaction conditions. • The easy separated catalyst recycled and employed for other eight successive runs. • The important medicinal compounds were successfully performed using introduced catalytic system in large-scale. Herein, a nano acid-base catalyst using magnetic core and carbamodithioic acid functional group have been synthesized and characterized. Its efficiency in the synthesis of dihydroquinazolinones and bis(indolyl)methanes derivatives was investigated. This novel metal-free catalyst exhibited significant catalytic activity in both reactions under green and mild reaction conditions (the yield obtained for the first reaction products: 82–98 % and for the second one: 61–97 %). The catalyst displayed good recyclability with no significant loss of catalytic activity after eight runs (the conversion of the eighth run was found as 83 %, the fresh catalyst conversion was 95 %). The introduced approach is attractive due to its applicability in the large-scale synthesis of important medicinal compounds.

Triethanolamine–sodium acetate as a novel deep eutectic solvent for promotion of tetrahydrodipyrazolopyridines synthesis under microwave irradiation

Deep eutectic solvents like ionic liquids were used as solvent or catalyst in organic synthesis. In this work, a novel deep eutectic solvent containing triethanolamine and sodium acetate was prepared and studied by Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), potential of hydrogen (pH), viscosity and conductivity. This deep eutectic solvent was applied for the synthesis of tetrahydrodipyrazolopyridines as an efficient reusable catalyst under microwave irradiation. The advantages of this method include easy catalyst preparation, low catalyst consumption, short reaction time, excellent product yields and safe operation.

Magnetic Ru Nanocatalysts for Sustainable Hydrogenation of CO2 Gas to Formic Acid

We performed the Ru nanoparticles encapsulation using silica-coated carbon-cobalt nanostructure (with and without amine functionality). The physicochemical properties of the above structures were evaluated using the following analytical techniques such as XPS, EDX, XRD, HR-TEM, and ICP-AES. The analytical data received from the above analysis were found in good correlation to each other and confirm the uniform distribution of ruthenium nanoparticles over the surface of the silica–carbon coated magnetic cobalt system. The uniform Ru dispersion confirms the high catalytic activity during CO2 hydrogenation reaction to formic acid. We also studied the effect of water and correlated the same with the quantity of formic acid. Easy catalyst preparation, hassle-free catalyst isolation under an applied magnetic field, and good catalyst recycling is the major outcome of this proposed work. The effect of the ionic liquid solvent system was also noticed in terms of high reaction rate, good catalyst stability, and nine times catalyst recycling.

Mesoporous Silica Nanoparticles Supported Atomically Precise Palladium Nanoclusters Catalyzed Aerobic Oxidation of Alcohols in Water

The first mesoporous silica nanoparticles (MSNs) supported atomically precise palladium nanoclusters catalyzed alcohol oxidation reactions in water have been achieved. The catalysts was synthesized with simple impregnation method and well characterized by TEM, FT-IR, XPS anddiffuse reflectance optical spectrum and the results proved that the Pd nanoclustersimmobilized into the pores of MSNs.The as-prepared catalyst show excellent activity for the alcohol oxidation reactions with high yield under extremely mild aqueous conditions utilizes 1 atmosphere of molecular oxygen as sole oxidant. The features of clean system, gram-scale oxidation and easy recovery catalyst make this method cost effectively and environmentally benign.

Mesoporous Silica Nanoparticles Supported Atomically Precise Palladium Nanoclusters Catalyzed Aerobic Oxidation of Alcohols in Water

The first mesoporous silica nanoparticles (MSNs) supported atomically precise palladium nanoclusters catalyzed alcohol oxidation reactions in water have been achieved. The catalysts was synthesized with simple impregnation method and well characterized by TEM, FT-IR, XPS anddiffuse reflectance optical spectrum and the results proved that the Pd nanoclustersimmobilized into the pores of MSNs.The as-prepared catalyst show excellent activity for the alcohol oxidation reactions with high yield under extremely mild aqueous conditions utilizes 1 atmosphere of molecular oxygen as sole oxidant. The features of clean system, gram-scale oxidation and easy recovery catalyst make this method cost effectively and environmentally benign.