Recyclable Heterogeneous Catalyst Research Articles

Water-Dispersible, Magnetically Recyclable Heterogeneous Cobalt Catalyst for C–C and C–N Cross-Coupling Reactions in Aqueous Media

Water-Dispersible, Magnetically Recyclable Heterogeneous Cobalt Catalyst for C–C and C–N Cross-Coupling Reactions in Aqueous Media

Atomically dispersed Rh catalysts formed on defective CeO2 surfaces with hydroformylation activity

The electron density of the metal active sites depends on the surface properties of the support. This study aimed to demonstrate that the formation of atomically dispersed Rh on ceria and the corresponding Rh electron density can be tuned depending on ceria concentration. The highly optimized Rh/CeO2-Al2O3 catalyst exhibited the highest activity during propylene hydroformylation, which was similar to that of the commercially available homogeneous catalyst RhCl(PPh3)3. Combined analytical results and theoretical calculations demonstrated that the increased Ce3+ fraction promoted high Rh electron density and attenuated CO adsorption strength, resulting in an increased hydroformylation activity. Additionally, the catalyst achieved separation and high added value by converting olefins to aldehydes through hydroformylation of olefins in a mixed C2–C4 olefin/paraffin gas. This study showed that atomically dispersed metal supported catalysts can be designed as recyclable heterogeneous catalysts by tailoring the local environment and corresponding electron density of the metal to achieve high activity similar to that of the homogeneous catalysts that manipulate ligands around the metal.

Eco-synthesis route: Developing bis-hydrazono[1,2,4]-thiadiazoles via a green synthetic approach with calcium oxide-chitosan nanocomposite

Modern environmental organic chemistry is focused on developing cost-efficient, versatile, environmentally acceptable catalytic chemicals that are also highly effective. Herein, hybrid calcium-chitosan nanocomposite films was prepared by doping calcium oxide molecules into a chitosan matrix at weight percentage (15, 20, and 25 % wt. chitosan‑calcium) using an easy and affordable simple co-precipitation process. The CS–CaO nanocomposite's structure was elucidated using analytical techniques such as Fourier transform infrared (FTIR), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). Based on the X ray diffraction (XRD) measurements, the crystallinity was reduced by the incorporation of the CaO molecules. Also, from the calculation of the Debye-Scherrer equation on this X-ray diffraction (XRD) pattern, the crystallite size was found to be 17.2 nm for the nanocomposite film with 20 % wt. The energy dispersive spectroscopy graph demonstrated the presence of the distinctive Ca element signals within the chitosan, with the amount in a sample of 20 % wt. being discovered to be 21.32 % wt. For the synthesis of bis-hydrazono[1,2,4]thiadiazoles, the obtained CS–CaO nanocomposite could be employed as a potent heterogeneous recyclable catalyst. Better reaction yields, quicker reactions, softer reaction conditions, and green reusable efficient biocatalysts for several uses are just a few advantages of this approach.

Prussian Blue Analogue Derived N-Doped Graphitic Carbon Wrapped Iron-Cobalt Nanoparticles as Recyclable Heterogeneous Catalysts for Friedel-Crafts Acylation

Prussian Blue Analogue Derived N-Doped Graphitic Carbon Wrapped Iron-Cobalt Nanoparticles as Recyclable Heterogeneous Catalysts for Friedel-Crafts Acylation

The Role of the Heterogeneous Catalyst to Produce Solketal from Biodiesel Waste: The Key to Achieve Efficiency.

The valorization of the large amount of crude glycerol formed from the biodiesel industry is of primordial necessity. One possible direction with high interest to the biorefinery sector is the production of fuel additives such as solketal, through the acetalization of glycerol with acetone. This is a chemical process that conciliates high sustainability and economic interest, since solketal contributes to the fulfillment of a Circular Economy Model through its use in biodiesel blends. The key to guarantee high efficiency and high sustainability for solketal production is the use of recovery and recyclable heterogeneous catalysts. Reported works indicate that high yields are attributed to catalyst acidity, mainly the ones containing Brönsted acidic sites. On the other hand, the catalyst stability and its recycling capacity are completely dependent of the support material and the acidic sites incorporation methodology. This review intends to conciliate the information spread on this topic and indicate the most assertive strategies to achieve high solketal production in short reaction time during various reaction cycles.

Two Different Three-Dimensional Uranium-Containing Polymolybdates Based on Zn(II) for the Heterogeneous Catalytic Construction of C-N Bond.

The introduction of transition metal (TM) ions into polyoxometalates (POMs) cannot only bring about interesting structural diversities but also enable changes in properties. However, TM-containing Silverton-type polyoxomolybdates are still lacking in terms of structural diversity and application development. Herein, two Zn(II)-containing Silverton-type {UMo12O42}-based polyoxomolybdates, H1.89Na4.11(H2O)9Zn[UMo12O42]·4.5H2O (Zn-1) and H1.8Na4.2(H2O)12Zn[UMo12O42] (Zn-2) were hydrothermally synthesized, demonstrating a practical strategy to assembly of TM-containing Silverton-type POMs. Zn-1 is proven to be an excellent and recyclable heterogeneous catalyst in cross-dehydrogenation coupling of 1,4-naphthoquinones with amines reactions, and a series of 2-amino-1,4-naphthoquinones with potential medicinal value have been constructed.

Synthesis and characterization of a Pd Schiff base complex anchored on Fe3O4 as a novel and recyclable catalyst for C[sbnd]C cross-coupling reactions

Pd Schiff base complex was immobilized onto the surface of magnetic Fe3O4 as a novel, eco‐friendly, and recyclable heterogeneous catalyst and fully characterized by BET, TEM, XRD, EDS, SEM, TGA, FT-IR, ICP‐OES, and VSM techniques. The obtained Fe3O4@SiO2@APT@BDA@Schiff base-Pd performance can show excellent catalytic activity for CC coupling reactions, and the corresponding products were obtained with high yields. The main advantages of using this catalyst include green reaction conditions, low loading of the catalyst, a simple experimental procedure, short reaction time, non‐use of hazardous organic solvents, and the ability to use various substrates. Palladium leaching was checked using ICP-OES and hot filtration. The synthesized nanocatalyst can be recovered and reused several times. The catalyst can be easily separated from the reaction mixture and recovered and reused without loss of stability and activity.

Ni/C-catalyzed aminocarbonylation of aryl halides using DMF as an amine source and o-chlorophenyl formate as a CO surrogate and promoter

We developed Ni/C-catalyzed aminocarbonylation of aryl halide by utilizing DMF and o-chlorophenyl formate to produce tertiary amides. This reaction employed o-chlorophenyl formate (OCPF) as a CO source, and it also acts as a promoter for the selective tertiary amide synthesis. Even under ideal conditions, this newly established approach considerably reduces the generation of homo-coupled biaryl ketone and phenoxy carbonylation byproducts. This protocol shows remarkable activity towards a wide range of aryl halides containing electron-donating and electron-withdrawing functional groups. This methodology represents the moisture-sensitive ligand-free, co-catalyst-free, and heterogeneous recyclable catalyst. The Ni/C catalyst was utilized for up to five consecutive runs. The fresh and recycled Ni/C catalysts were characterized using several techniques, including TEM, SEM, EDX, XRD, and TGA analysis.

Fe3O4@SiO2@CSH+VO3− as a novel recyclable heterogeneous catalyst with core–shell structure for oxidation of sulfides

Iron nanoparticles, with low toxicity and many active sites, are among the materials that not only reduce waste along with green chemistry but also increase the separation power and recover the catalyst from the reaction environment. In this study, first, the surface of iron nanoparticles was silanized, and in the next step, the complex of chitosan HCl.VO3 was placed on the surface of Fe3O4 (Fe3O4@SiO2@CSH+VO3−). This nanocatalyst is a novel, recoverable, and potent nanocatalyst with high selectivity for the oxidation of sulfides to sulfoxides. Various physicochemical techniques such as IR, XRD, TGA, SEM, EDX, mapping, TEM, and VSM were used to affirm the well synthesis of the catalyst. Oxidation of sulfides in the presence of hydrogen peroxide as a green oxidant and in ethanol was catalyzed by the Fe3O4@SiO2@CSH+VO3−. All sulfoxides were achieved with high efficiency and in a short time. The notable privileges of this method include facile and economic catalyst synthesis, proper catalyst durability, great performance, simple catalyst isolation, good recovery capability, at least up to 5 times without an index drop in catalytic power.

Chitosan-functionalized poly(3-hydroxybutyrate) bead as a novel biosupport for palladium in the Suzuki cross-coupling reaction

The utilization of environmentally friendly biopolymer poly(3-hydroxybutyrate) (PHB) as a support for metal catalysts is an unexplored area. Herein, exploring a stable and recyclable heterogeneous palladium (Pd) catalyst based on PHB for the Suzuki cross-coupling reaction is an attractive topic. In this study, a novel hydrophobic and hydrophilic core-shell bead supported Pd catalyst was developed by using PHB particle as a hydrophobic rigid framework and hydrophilic chitosan (CS) as the surface of the supporting matrix to fix Pd nanoparticles (NPs). The results of structural characterization showed that the Pd NPs with a small average size of 2.3±0.82 nm were uniformly distributed on the surface of the PHB-CS bead with a Pd content of 0.12 wt%. This demonstrated that the PHB-CS bead created a stable coordinated environment for Pd fixation, preventing Pd leaching. Furthermore, the Pd@PHB-CS catalyst exhibited high catalytic efficiency with 99% conversion in the Suzuki reaction under mild conditions, using a solvent mixture of EtOH and H2O (1:1) for 0.5 h. It is worth noting that the catalyst exhibits excellent stability, and reusability. It can be reused five times without a significant reduction in activity while maintaining its structural integrity. The successful construction of Pd@PHB-CS will further expand the application of PHB in the field of metal catalysts and may help establish a green and environmentally friendly multifunctional platform for the development of highly recyclable heterogeneous catalysts containing metal nanoparticles.

Confinement Effect in Metal-Organic Framework Cu3(BTC)2 for Enhancing Shape Selectivity of Radical Difunctionalization of Alkenes.

The radical difunctionalization of alkenes plays a vital role in pharmacy, but the conventional homogeneous catalytic systems are challenging in selectivity and sustainability to afford the target molecules. Herein, the famous readily available metal-organic framework (MOF), Cu3(BTC)2, has been applied to cyano-trifluoromethylation of alkenes as a high-performance and recyclable heterogeneous catalyst, which possesses copper(II) active sites residing in funnel-like cavities. Under mild conditions, styrene derivatives and various unactivated olefins could be smoothly transformed into the corresponding cyano-trifluoromethylation products. Moreover, the transformation brought about by the active copper center in confined environments achieved regio- and shape selectivity. To understand the enhanced selectivity, the activation manner of the MOF catalyst was studied with control catalytic experiments such as FT-IR and UV-vis absorption spectroscopy of substrate-incorporated Cu3(BTC)2, which elucidated that the catalyst underwent a radical transformation with the intermediates confined in the MOF cavity, and the confinement effect endowed the method with pronounced selectivities.

Magnetic CuFe2O4 nanoparticles immobilized on mesoporous alumina as highly efficient peroxymonosulfate activator for enhanced degradation of tetracycline hydrochloride

Nanoscaled magnetic copper ferrite (CuFe2O4) is widely used as a peroxymonosulfate (PMS) activator but suffers from agglomeration owing to its inherent magnetic properties and high surface energy. In this work, spinel structured CuFe2O4 anchored on mesoporous alumina (denoted as CFO@AO) were synthesized, characterized, and applied as a PMS activator for the removal of tetracycline hydrochloride (TC·HCl). Approximately 97.5 % of TC·HCl was decomposed within 10 min in 30 %–CFO@AO (0.2 g/L)/PMS (0.3 g/L) system, and the corresponding kinetic rate constant of 30 %–CFO@AO/PMS (0.417 min−1) was around 1.57 times higher than that of CuFe2O4/PMS (0.266 min−1), which indicating that the existence of synergistic catalysis between CuFe2O4 and Al2O3 enhanced the degradation of TC·HCl. Moreover, nano-sized CuFe2O4 were successfully anchored on the surface of Al2O3 because of FeOAl bond, which could account for the enhanced catalytic activity, superior pH flexibility, and high chemical stability and reusability of 30 %–CFO@AO. Quenching experimentals, electron paramagnetic resonance, and methyl phenyl sulfoxide (PMSO) chemical probe assays confirmed that both radical oxidation (OH) and non-radical oxidation (1O2 and Fe(IV)O) were proposed in the developed CFO@AO/PMS system, and OH played a key role in the process. Meanwhile, the PMS activation mechanism by CFO@AO composite was also analyzed based on the results of adsorption energy, which was calculated via DFT. Based on UPLC–MS technique, a possible degradation pathway for TC·HCl destruction in 30 %–CFO@AO/PMS system was proposed. The toxicity assessment showed that the catalytic degradation of TC·HCl in 30 %–CFO@AO/PMS system reduced the toxicity of most of degradation intermediates. Present work proved that CuFe2O4@Al2O3 composite is an efficient, environment-friendly, and recyclable heterogeneous catalyst for practical wastewater treatment via PMS activation.

Biodiesel Synthesis from Vegetable Oils Using a Recyclable Heterogeneous Catalyst: Employing Active Learning to Implement Education for Sustainable Development

Biodiesel Synthesis from Vegetable Oils Using a Recyclable Heterogeneous Catalyst: Employing Active Learning to Implement Education for Sustainable Development

Salt-Supported Nickel Oxides for Boosted Hydrogen Production: The Critical Role of Halogen.

Hydrogen production from organic waste by gasification and reforming technologies offers major benefits to both the environment and climate. The long-term stability and regeneration of the reforming catalyst are still the biggest challenges because of carbon deposition. Here we report a recyclable salt-supported nickel oxide NiO/NaX (X: F, Cl, Br) catalyst for effective autothermal reforming of the oxygenated volatile organic compound (OVOC) ethyl acetate to hydrogen. The optimal hydrogen selectivity achieved 82.0% at 650 °C and the durability reached 43 h. Interestingly, with the decreasing of halogen electronegativity (F > Cl > Br) in NaX, the corresponding hydrogen selectivity of the catalysts decreased. Although NiO/NaX catalysts possess a very small specific surface area and a dense microstructure, their catalytic performance is better than that of normal Ni-based catalysts loaded on high-specific-surface-area supports. Detailed investigations revealed the critical roles played by halogen during the reforming reaction. First, the strong electronegative halogen in NaX induced the formation of hydrogen bonds with the reactants and reaction intermediates, which may prolong the surface residence time of such species, thus ensuring efficient hydrogen production over small-specific-surface-area catalysts under high-temperature conditions. Second, the halogen of the support NaX weakening the Ni-O bonds of the exposed Ni atoms in NiO/NaX made it easier for NiO to be reduced to Ni0, thus reducing the reaction activation energy and prompting the rapid catalytic reaction. The strength of such metal-support interaction can be easily modulated by varying the halogen electronegativity. This study provides a new prospect for the design of innovative recyclable heterogeneous catalysts with low specific surface area but high activity.

Improved Process for the Continuous Acylation of 1,3-Benzodioxole

The acylation of 1,3-benzodioxole was studied in a continuous process using a recyclable heterogeneous substoichiometric catalyst. In a short time period (30 min), at 100 °C, the conversion rate was 73%, with a selectivity of 62% of the desired acylated product; the reaction was run continuously for 6 h, showing excellent stability and selectivity. Moreover, the unreacted starting material, 1,3-benzodioxole, can be easily separated by distillation and recycled.

Design and Preparation of a Bifunctional Nanobiohybrid Catalyst by Combining Palladium and α‐Amylase Enzyme: Application in One‐pot Chemoenzymatic Catalysis

AbstractA chemoenzymatic approach that combines chemical and bio‐catalyst has proven very useful in synthetic chemistry, however, mutual deactivation of chemical and bio‐catalyst when employed in the same pot is still a challenge. In this context, the development of nanobiohybrid catalysts has played an important role and overcoming the issue of mutual deactivation between catalysts to a certain extent. Herein, we design and synthesize a novel heterogeneous recyclable nanobiohybrid catalyst comprising palladium nanoparticles and α‐amylase from Aspergillus oryzae immobilized onto halloysite nanotubes as a solid heterogeneous support. Further, the wider applicability of the developed nanobiohybrid catalyst is revealed in the one‐pot chemoenzymatic synthesis of functionalized biphenyls and bis(indolyl)methanes which consists of Pd‐catalyzed Suzuki‐Miyaura coupling and α‐amylase mediated aza‐Michael addition or electrophilic substitution reactions respectively. Further, the robustness and generality of the developed one‐pot chemoenzymatic synthesis are demonstrated by incorporating different substitutions at the starting materials and obtaining the corresponding products in moderate to good yields.

A mesoporous ionic metal-organic framework decorated by flexible alkyl imidazolium bromide as heterogeneous catalyst for efficient conversion of CO2 to cyclic carbonates

A mesoporous ionic MOF-based catalyst (Br−)C3H7-Imidazolium-MOF-1 for the cycloaddition of CO2 to epoxides (CCE) was synthesized by template-assisted method, and its composite and structure were determined by FT-IR, PXRD, NMR, SEM, TEM, XPS and N2 adsorption. (Br−)C3H7-Imidazolium-MOF-1, is constructed by Zr6O4(OH)4 clusters and linear dicarboxylic acid ligands covalently modified by flexible alkyl imidazolium groups (1-methylene-3-propyl-imidazolium bromide). By the synergistic effect of Zr4+ Lewis acid sites and Br− nucleophiles, (Br−)C3H7-Imidazolium-MOF-1 shown superior catalytic performance for the cycloaddition of CO2 to epichlorohydrin in the absence of any co-catalyst under mild conditions. Small steric hindrance from the flexible imidazolium groups and rapid mass transport of reactants and products in the mesoporous catalyst acted synergistically to promote this process. A firm bond between the imidazolium bromide and the framework of (Br−)C3H7-Imidazolium-MOF-1 made it a recyclable heterogeneous catalyst. Furthermore, several additional coupling reactions were investigated with other epoxides as substrates.

Heterogeneous catalysis of FeOOH in-situ loaded biochar for reactive red X-3B: Catalytic mechanism based on Fenton-like system

Fenton reaction is one of the effective methods applying in the industrial wastewater treatment. However, the iron ions (Fe3+) used in conventional Fenton reaction are difficult to recover, which will convert into Fe(OH)3 and produce a large amount of excess sludge. Biochar with rich porous structure is an excellent adsorbent, but it is challenging to reuse after adsorption. Considering these facts, the FeOOH was in-situ loaded onto carboxylated biochars, and the recyclable heterogeneous catalysts (FeOOH@CBC) were fabricated. The cyclic adsorption-photocatalytic processes of FeOOH@CBC with different crystal structures (amorphous FeOOH, α-FeOOH and β-FeOOH) for reactive red X-3B were explored. Under the simulated solar irradiation, the α-FeOOH@CBC shown outstanding catalytic activity for reactive red X-3B (1000 mg·L−1) with a decolorization rate of 99.9% in 90 min, and the released Fe3+ concentration was below the detection range (0.1 mM) of potassium thiocyanate colorimetry method. After the 10th cycle, the COD removal rate of α-FeOOH@CBC for reactive red X-3B still reached 95% (14,550 mg·g−1). The excellent reusability of α-FeOOH@CBC and minimal iron ion release can decrease the solid waste pollution from adsorbed biochar, which may promote the large-scale application of biochar in industrial wastewater treatment.

Cassia fistula galactomannan stabilized copper nanocatalyst as an efficient, recyclable heterogeneous catalyst for the fast clickable [3+2] Huisgen cycloadditions in water

In this study, we have first time investigated the synthesis of copper nanocatalyst by using biopolymer galactomannan, naturally extracted from Cassia fistula pods. The methodology involved for the preparation of copper nanocatalyst is economical, efficient, environment friendly, and did not involve further processing for stabilization or reduction of copper nanoparticles. The morphology and structural characterization of the nanocatalyst was performed by using different techniques such as FT-IR, 1H NMR, SEM, EDX, HR-TEM, XRD, XPS, ICP-MS, BET, and TGA analysis. The prepared copper nanocatalyst is applied for the click [3+2] Huisgen cycloadditions of various azides and alkynes, employing water as environmentally benign solvent. In comparison to earlier reported methods, our method requires lowest catalyst loading, less reaction time, excellent yields and have wide substrate scope. Additionally, the catalyst was easily recovered by simple filtration and recycled at least ten consecutive times without any appreciable loss of efficiency and selectivity. The effect of mannose and galactose (Man/Gal) ratio of Cassia fistula galactomannan on the catalytic activity were also investigated.

Sonochemical synthesis of ortho‐aminocarbonitrile tetrahydronaphthalenes using mesoporous yolk–shell nanocomposites as a recyclable heterogeneous catalyst and evaluation of their in vitro antimicrobial activities

A mobile Ca/Mg core was formed inside the silica shell of mesoporous yolk–shell nanocomposites (CaO‐MgO@SiO2). This new structure of hollow mesoporous silica spheres has been successfully synthesized inside the inner cavity. The used carbon spheres as a rigid template in the multi‐step synthetic process are covered with tetraethyl orthosilicate (TEOS) and a mixture of cetyltrimethylammonium bromide (CTAB). Then, the tetrahydronaphthalenes were synergistically synthesized using CaO‐MgO@SiO2 nanocomposites as a nanocatalyst under ultrasound irradiation. By this technique, the required items could be produced with a high to excellent efficiency between 90% and 98% and the reaction times of 5–15 min. As an effective and reusable catalyst in multicomponent processes, the CaO‐MgO@SiO2 catalyst exhibits high reactivity. The FT‐IR, 1H NMR, and melting point methods were used to identify all of the products. Moreover, FT‐IR, XRD, FE‐SEM, EDS, Mapping, and HR‐TEM techniques are used to characterize the prepared catalysts. Also, in vitro antibacterial activity of some synthetic compounds was evaluated.