Recyclable Heterogeneous Catalyst Research Articles

Experimental Investigation of Engine Performance for 2nd Generation Biodiesel Derived from Mg2Zr5O12 Catalyst

In the present study, experimental analyses were conducted by using biodiesel derived from second-generation feedstock. In terms of cost and accessibility, second-generation feedstock has gained more attention due to its environmental approach. Waste-cooking-oil-derived methyl ester was produced through a transesterification reaction in the presence of a synthesized magnesium zirconate (Mg2Zr5O12) heterogeneous catalyst. This trans-esterified waste cooking oil (WCO) was used as biodiesel and was blended with diesel in 10%, 20%, 30%, 40%, and 50% by volume ratio for further analysis. The fuel properties of pure and blended biodiesel were investigated in terms of flash point, density, kinematic viscosity, and lower heating value as per the American Society for Testing and Materials (ASTM) D-6751 standards. For each blended fuel, the engine performance and gaseous emissions trend with engine loads of 0, 3, 6, 9, and 12 kg were measured on a Kirloskar TV1 IC engine. The results indicated that the 40% blended biodiesel has the maximum brake thermal efficiency (BTE) of 19.13% and exhaust gas temperature (EGT) of 6.98% increment, also showing an increase with respect to engine load. On the other hand, brake-specific fuel consumption (BSFC) was highest for 40% blending as 36.48% increase, and that decreases with the increase in engine loads. Significant reductions in carbon monoxide (CO) and unburned hydrocarbon (HC) emissions were observed for 40% blended fuel and were 34.78% and 38.1% reduction, respectively. CO and HC emissions decreased with respect to the engine load. Meanwhile, reverse trends for carbon dioxide (CO2) and nitrogen oxide (NOx) have been observed as 14.57% and 27.85% increases for 100% biodiesel. CO2 and NOx increased with increase in engine load. The mass balance and environmental factor of crude and purified biodiesel were studied to show the environmental suitability of synthesized product. Overall, the results showed that the blended biodiesel can be used as a substitute and has an advantage over diesel fuel. The main contribution derived from this work is to improve engine performance and gaseous emission by using blended biodiesel derived from a recyclable heterogeneous catalyst and waste-cooking-oil feedstock.

Correlation of adsorbed and embedded palladium species in chitosan composite nanofibers with their catalytic activities for Suzuki reactions

Heterogeneous palladium catalysts play an important role in the synthetic organic chemistry. Palladium species have been adsorbed on the surface of solid matrices or embedded inside solid matrices to prepare recyclable heterogeneous catalysts. Due to the different surrounding environment, these two type palladium species had different electronic properties and catalytic performances. In this study, we fabricated three series of chitosan composite nanofibers with adsorbed and embedded palladium species. Their fiber morphologies and chemical structures were characterized by SEM and FT-IR, respectively. Positron annihilation lifetime spectra (PALS) showed that the intensities (I3) of o-Ps annihilations were all linearly decreased with the increase of palladium contents in the chitosan composite nanofibers. Moreover, compared with the palladium adsorbed chitosan composite nanofibers, the palladium embedded chitosan composite nanofibers had stronger o-Ps annihilation ability, which could be ascribed to the stronger electron donating property of embedded palladium species and higher crosslinking of chitosan molecules by embedded palladium species. At last, the I3 values were successfully correlated with the rate constants of chitosan supported palladium composite nanofibers catalyzed Suzuki reactions of iodobenzene with phenylboric acid. Therefore, we have developed a facile method to distinguish the adsorbed and embedded palladium species by PALS, which can be further related with their catalytic performance.

A Highly Active Nitrogen‐Doped Mixed‐Phase Mixed‐Valence Cobalt Nanocatalyst for Olefins and Nitroarenes Hydrogenation

AbstractDevelopment of an inexpensive, environmentally friendly and robust recyclable heterogeneous catalyst for alkene and nitroarene hydrogenation is in high demand for the sustainable future of chemical industries. Herein, we have synthesize and characterized a trinuclear mixed valence cobalt complex 1 and nitrogen doped mixed phase cobalt (β‐Co(OH)2 and CoO) nanocatalyst (N@MPCoNC) as reported earlier. N@MPCoNC was synthesized via single source molecular precursor by reducing 1 by aq. N2H4 followed by calcinations. Both mixed‐valence cobalt metal complex (1) and nitrogen doped mixed phase cobalt nanocatalyst (N@MPCoNC) were utilized for alkenes and nitroarenes hydrogenation reaction, however excellent catalytic activity was noticed by N@MPCoNC with the 100 % conversion of styrene and 4‐nitrotoluene to the corresponding ethylbenzene and 4‐aminotoluene with 100 % selectivity under mild reaction condition. The scope of the heterogeneous N@MPCoNC was further evaluated for other alkenes and nitroarenes to obtain corresponding alkanes and aminoarenes with an excellent conversion and high selectivity at room temperature.

Visible‐Light Driven C‐P Bond Formation with Recyclable Carbon Nitride Photocatalyst

AbstractThe development of metal‐free chemical process with recyclable heterogeneous catalyst under ambient conditions is highly desired in industrial production, especially for pharmaceutical purpose. We herein reported the efficient synthesis of pharmaceutically relevant organophosphorus(V) compounds through the coupling of readily available starting materials in the presence of insoluble carbon nitride (g‐CN) as recyclable photocatalyst. These reactions showed wide functional group tolerance and were performed at room temperatures under visible‐light irradiation. The heterogeneous g‐CN photocatalyst could be easily separated from the crude reaction mixture and reused for several cycles without decreasing the reaction efficiency, thus implying the great potential of use in industrial manufacture for larger‐scale synthesis.

C−C Coupling of Aryl Chlorides and Reduction of Nitroarenes to Amines Employing Recyclable Heterogeneous Green Catalysts

AbstractTwo new isostructural inorganic coordination polymers, [M(C14H8O6)(C10H8N2)2H2O)] ⋅ (C3H7NO), (M=Co, Ni) were prepared employing 2, 5‐bis(prop‐2‐yn‐1‐yloxy)terephthalic acid (2,5 BPTA) and 4,4′ bipyridine as ligands. The connectivity between the metal‐centers and the ligands give rise to a two‐dimensional layer structure. The Ni‐containing one has higher stability compared to the Co‐containing one. The Co‐containing compound, 1, was heated in Ar‐atmosphere to prepare Co‐nanoparticles, supported over graphitic carbon. The Co@C−T compounds were found to be active for the Bechamp reaction of reduction of nitroarenes to aminoarenes under solvent‐free condition with good yields and recyclability. The Ni‐containing compound, 2 was loaded with Pd‐nanoparticles by known procedures. The Pd@2 samples were found to be a good catalyst for the Suzuki‐Miyaura C−C coupling of chloroarenes in ethanol at 75 °C in good yield. The present work demonstrates a clean approach for the preparation of new heterogeneous catalysts for the reduction of nitroarenes and especially towards activating chloro‐arenes under recyclable reaction conditions. These catalysts and the reactions are green as the Bechamp reaction employing the Co@C−T catalysts was carried out under solvent‐free conditions and the Pd@2 catalysis employing environmentally benign ethanol.

Selective Conversion of Malononitrile and Unprotected Carbohydrates to Bicyclic Polyhydroxyalkyl Dihydrofurans Using Magnesium Oxide as a Recyclable Catalyst

Using renewable feedstocks to access highly functionalized molecules in a concise manner is a promising approach to sustainable syntheses. Previous studies used malononitrile to convert simple sugars to polyhydroxylalkyl aminofurans in the presence of various catalysts. Herein, a chemodivergent method is disclosed for the reaction of the same unprotected sugars with malononitrile to instead form bicyclic 2,3-dihydrofuran products in yields up to 85% with good regioselectivities. Kinetic, NMR, and computational studies support a proposed mechanism for the formation of dihydrofuran products. By employing a mild set of reaction conditions (aqueous solvent, at room temperature, in under 4 h) and a recyclable heterogeneous MgO catalyst, this method serves as a powerful tool for carbohydrate upcycling that offers useful and interesting nonaromatic products.

Nano 5% Fe–ZnO: A highly efficient and recyclable heterogeneous solid nano catalyst for the Biginelli reaction

In this paper, we report the synthesis and catalytic application of 5% Fe–ZnO nanocatalyst for the synthesis of 3,4-dihydropyrimidin-2-one derivatives as a highly efficient heterogeneous nanocatalyst. The structural and morphological features of the synthesized nanocatalysts were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Using Debye-Scherer's formula, the average particle size for undoped ZnO was calculated to be 24.55 nm, while the average particle size for 5% Fe–ZnO was calculated to be 22.37 nm. The high resolution transmission electron microscopy (HR-TEM) revealed a hexagonal crystal lattice type. The Brunauer–Emmett–Teller (BET) surface area of ZnO and 5% Fe–ZnO was found to be 56.50 m2/g and 72.65 m2/g, respectively. Energy Dispersive X-Ray Analysis (EDX) confirmed the elemental composition of undoped ZnO and doped 5% Fe–ZnO nanocatalysts. Biginelli products were produced using a one-pot three-component reaction of urea, β-dicarbonyl compound, and various aromatic aldehydes using 5% Fe–ZnO under clean conditions. It was found that a 5% Fe–ZnO nanocatalyst is a highly efficient heterogeneous nanocatalyst for the synthesis of 3,4-dihydropirimidinones. 1H NMR and 13C NMR analysis was used to confirm the structure of the synthesized Biginelli adducts. This synthetic protocol offers several advantages, including a short reaction time and purity of the synthesized, reusability and ease of catalyst separation, and a clean and quick workup.

Preparation and characterization of amine-terminated delafossite type oxide, CuMnO2–NH2, supported Pd (0) nanoparticles for the H2 generation from the methanolysis of ammonia-borane

Among the cuprous metal oxides of the delafossite type, which are generally formulated as CuMO2 (M = Al, Cr, Fe, Ga, Mn), the most promising is the CuMnO2 structures. CuMnO2 material, named crednerite, is a very interesting delafossite derivative with potential applications in many fields, mainly catalyst, photoelectrochemical cells and multiferroic tools. Herein, we report fabrication, characterization, and application of amine-terminated CuMnO2 (CuMnO2–NH2) supported palladium nanoparticles (Pd/CuMnO2–NH2) as highly efficient and recyclable catalysts for the hydrogen production from the methanolysis of ammonia-borane (AB). The results of characterization using P-XRD, TEM, HRTEM, TEM-EDX, XPS, SEM, SEM-elemental mapping, and ICP-OES disclose that Pd (0) nanoparticles were well spread on the surface of CuMnO2–NH2 with a mean particle size of 3.91 ± 0.33 nm. Pd/CuMnO2–NH2 shows high catalytic activity in the methanolysis of AB with an initial turnover frequency of 146.68 min−1 at 25 ± 0.1 °C which is one of the highest values ever reported for AB methanolysis in the literature. Besides, the extreme stability of Pd/CuMnO2–NH2 takes it a recyclable heterogeneous catalyst in this catalytic conversion.

A nanocaged cadmium-organic framework with high catalytic activity on the chemical fixation of CO2 and deacetalization-knoevenagel condensation

Heterogeneous MOFs catalysts have attracted great attention due to the efficient combination of heterogeneity (easy post-reaction separation and recyclability) and homogeneity (active sites and porosity), which inspire us to explore functional MOFs materials with higher catalytic activity on the chemical fixation of CO2 and deacetalization-Knoevenagel condensation. Herein, the self-assembly of Cd2+ and H6TDP under acidic solvothermal condition generated one cadmium-organic framework of {[(CH3)2NH2]2 [Cd2 (TDP) (H2O)2]⋅3DMF⋅2H2O}n (NUC-29, H6TDP = 2,4,6-tris(2,4-dicarboxyphenyl)pyridine) with nano-caged voids and hierarchical microporous channels, which were built on the combination of two kinds of mononuclear units of [Cd (1) (COO)3(H2O)] and [Cd (2) (COO)3(H2O)]. After the removal of solvent molecules by activation, NUC-29 possesses the coexistence of Lewis acid-base sites on the inner surface of channels including all exposed Cd2+ sites and Npyridine sites, which render it an excellent recyclable heterogeneous catalyst to facilitate the cycloaddition reaction of epoxides with CO2 and deacetalization-Knoevenagel condensation under mild conditions.

Simultaneous transformation of sugars and CO2 into sugar derivatives and formate at room temperature: Effect of alcohols and cations

Catalytic hydrogenation of CO2 to formate is an attractive pathway for CO2 utilization. In this system, replacing fossil fuel based H2 with a biomass-derived H2 source and using a recyclable heterogeneous catalyst at mild reaction conditions are advantageous to construct a green and sustainable process. Here, we demonstrate the transfer hydrogenation of biomass-derived sugars to CO2 affording sugar-derivatives and formate using a physical mixture of Pt/C and Pd/C catalysts. In this regard, the effects of various parameters such as the solvent composition, CO2 source, reactant concentrations, and sugar source were systematically investigated. In addition, the glucose dehydrogenation and bicarbonate hydrogenation were separately conducted to understand the effect of the parameters on each reaction. Based on the catalytic results and 13C NMR study, the reaction mechanism was suggested. The results demonstrated that the hydrogen transferring ability, salt solubility, and water structure breaking as well as pH and H2 solubility were crucial factors that could affect the catalytic activity. The high- concentration reaction was carried out to enhance the productivity, and high turnover numbers of 1018 and 99.8 were obtained for Pt/C and Pd/C, respectively. Moreover, the reaction system heterogeneity was confirmed by retained activity after consecutive cycling tests.

Nickel supported on magnetic biochar as a highly efficient and recyclable heterogeneous catalyst for the one‐pot synthesis of spirooxindole‐dihydropyridines

AbstractMagnetic materials show promising applications in heterogeneous catalysis because of their ease of separation and good reusability. The present work reports the design, synthesis, and characterization of a novel magnetic biochar supported nickel catalyst. Fourier infrared spectroscopy (FT‐IR), powder X‐ray diffraction technology (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), and vibrating sample magnetometer (VSM) techniques were used for analyzing the prepared catalyst. The prepared catalyst exhibited excellent catalytic activity for synthesis of spirooxindole‐dihydropyridines derivatives by a one‐pot three‐component reaction of isatin, barbituric acid, and 6‐amino uracil or 1H‐pyrazol‐5‐amine. This new methodology demonstrated some important features, including high yields, lower loading of the catalyst, easy work‐up, and recyclability of the catalyst for a minimum of six times without an obvious decay of catalytic performance.

Expeditious and Cost-effective Synthesis of α-Amino Nitriles Using ZnCl2/hydrotalcite as a Recyclable Heterogeneous Catalyst

Expeditious and Cost-effective Synthesis of α-Amino Nitriles Using ZnCl2/hydrotalcite as a Recyclable Heterogeneous Catalyst

In-situ synthesis of metal nanoparticle embedded soft hybrid materials via eco-benign approach

Abstract The unique optical and electronic properties of metal nanoparticles and tunable properties of the organic templates encourage the scientific community to generate metal nanoparticle embedded soft hybrid materials for various novel utilities. Here, we discuss the in-situ synthesis of metal nanoparticle embedded soft hybrid materials via eco-benign approach which exclude the use of toxic reducing/capping agents or toxic reaction media. In this protocol, the gel matrix composed of benign organic templates act as reducing as well as stabilizing agent for the in-situ generation and stabilization of metal nanoparticles. As the incorporation of metal salts (as nanoparticle precursor) in the gel medium is required in this process, in most of the cases aqueous media were used for the generation of metal nanoparticle embedded soft hybrid materials. This discussion includes interesting findings from our laboratory where hybrid gel matrix composed of renewable chemicals was utilized for the in-situ synthesis of palladium nanoparticle embedded soft trihybrid material. The hybrid gel matrix rich in polyphenols/flavonoids was exploited to generate palladium nanoparticle embedded trihybrid gel through in-situ reduction of doped Pd (II) salts to stable PdNPs. The xerogel of this trihybrid material was utilized as recyclable heterogeneous catalyst for C-C coupling reaction in air under phosphene free condition and reduction reaction.

Titanium tetrachloride immobilized on cross-linked poly(N-vinyl-2-pyrrolidone) as a recyclable heterogeneous catalyst for one-pot three component synthesis of 3, 4-dihydropyrimidin-2(1H)-ones/thiones

A new catalytic application of titanium tetrachloride immobilized on the cross-linked poly(N-vinyl-2-pyrrolidone) carrier as beads, TiCl4/PNVP, as a recoverable and heterogeneous macromolecular Lewis acidic catalyst is developed. This catalytic system allowed for the facile and cleaner synthesis of 3,4-dihydro pyrimidin-2(1H)-ones/thiones in high yields with TON up to 23.2 through the Biginelli three-component cyclocondensation reaction in ethanol. The reusability test ascertained that this heterogeneous titanium catalyst can be easily separated from the reaction mixture by simple filtration and reused several times with no great decline of activity.

Defect modulation of MOF-derived ZnFe2O4/CNTs microcages for persulfate activation: Enhanced nonradical catalytic oxidation

• ZnFe 2 O 4 /CNTs-Ar catalysts can efficiently activate PS to degrade BPA in a wide pH range. • Defective and porous microcages exhibit 17.5 times higher activity than blank ZnFe 2 O 4 . • Defect modulation of CNTs facilitated the electron transfer for nonradical degradation. • Magnetic property ensured the convenient collection of catalysts by magnets. • We offer a new strategy to enhance nonradical oxidation through defect modulation. There has been growing interest in the combination of porous metal organic frameworks (MOFs)-derived architectures with conductive carbonaceous materials for the synergistically enhanced catalytic activity. Herein, we described a facile strategy to synthesize a highly efficient and recyclable heterogeneous catalyst through pyrolysis of MOFs as sacrificial templates. We found that creating defective sites in CNTs precursors exhibited significant impact on the charge transfer capability of composite microcages and the coordination environment of Fe centers. With the assistant of persulfate oxidants, ZnFe 2 O 4 /CNTs-Ar with modulated defects exhibited 17.5-fold higher kinetic reaction rate (0.35 min −1 ) than blank ZnFe 2 O 4 microcages for Bisphenol A degradation. Experimental characterizations suggested that defective CNTs played a vital role in shuttling electron from BPA molecules to persulfate, triggered the direct decomposition of pollutants via a non-radical oxidation pathway. Our research provides a new strategy to develop high-performance MOFs-derived catalysts through defect modulation for wastewater treatment.

Tuning the Catalytic Activity of Recyclable Heterogeneous Catalysts for the Direct Etherification Reaction of Glycerol Using Antagonistic Additives

Using zeolite as a heterogeneous catalyst, the reaction conditions were optimized to increase the yield and selectivity of diglycerol (DG) and triglycerol (TG) in the direct etherification reaction of glycerol. By the addition of weakly acidic alkali metal-based inorganic salts (NaHSO4 and KHSO4), the selectivities and yields of DG and TG increased. Although the conversion of glycerol was lowered due to the role of the additive as an inhibitor, the reaction conditions were optimized by controlling the amounts and reaction times of the additives to increase the yields of DG and TG. Under the optimized condition, the glycerol conversion was as high as 85.4%, and the highest yields of DG and TG were observed as 54.1% and 21.3%, respectively. The recyclability of the catalysts was much enhanced by the influence of the additives suppressing the formation of oligomers.

A facile synthesis of quinoxalines by using SO4 2−/ZrO2-TiO2 as an efficient and recyclable heterogeneous catalyst

Quinoxaline derivatives have been synthesized in good to excellent yields by the cyclocondensation reaction of o-pheneylenediamine with substituted phenacyl bromides/benzil in the presence of SO4 2−/ZrO2-TiO2 as an efficient and heterogeneous catalyst. The catalyst can be recovered up to five catalytic cycles without significant loss in catalytic activity. The reported SO4 2−/ZrO2-TiO2 catalyst has been thoroughly characterized by using infrared spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and powder X-ray diffraction (XRD). Here, we have used ethanol as a green solvent in this cyclocondensation. This new method has several advantages, such as excellent yields, short reaction time, nontoxic, and easily recoverable catalyst.

Fullerene‐C60/NH2: A recyclable heterogeneous catalyst for the green synthesis of chromene and pyrimidine derivatives and antibacterial evaluation

AbstractAn effective procedure for the synthesis of amino‐functionalized fullerene with diethylenetriamine (C60‐NH2) is described. The obtained material was characterized by Fourier‐transform infrared spectroscopy, X‐ray diffraction, scanning electron microscopy, energy dispersive X‐ray spectroscopy, elemental analysis, thermogravimetric measurements, and X‐ray photoelectron spectroscopy. The catalytic activity of C60‐NH2 was studied in multicomponent reactions for the synthesis of chromene and pyrimidine derivatives. The results revealed that C60‐NH2 was very effective and the desired chromene and pyrimidine products were isolated in good to excellent yields 78%–97% and 81%–98%, respectively. Moreover, the C60‐NH2 catalyst could be recycled and reused for at least eight runs without substantial loss in its activity, which makes our procedure environmentally benign. Antibacterial behavior of some of the synthesized products was studied against Gram‐positive and Gram‐negative bacteria using disk and well diffusion methods. The chromene 4g showed a good antibacterial activity against both bacterial strains Staphylococcus aureus and Serratia marcescens. A good antibacterial activity was also detected for chromene 4o and pyrimidine 7j against S. aureus. The chromene 4m, 4n and pyrimidine 7i compounds displayed a good activity against Micrococcus luteus as a Gram‐positive bacterium.

Recyclable polymer-supported iridium-based photocatalysts for photoredox organic transformations

Various recyclable heterogeneous catalysts have been developed through anchoring a cyclometalated Ir(III) complex on different types of polymer support materials. These photocatalysts show dual emissive properties with a major short-lived MLCT phosphorescence and a minor polymer-based emission. The MLCT phosphorescence can be oxidatively quenched when suspended in the solution of perfluorohexyl iodide to generate perfluorohexyl radical that drives the photoredox addition and amidation reactions. The photocatalytic activity and performance of these photocatalysts have been studied with some of them displaying excellent recyclability. In this study, the criteria for designing efficient and recyclable heterogeneous immobilized photoredox catalysts have been intensively discussed.

Chemoselective reduction of nitroaromatics using recyclable alumina-supported nickel nanoparticles in aqueous medium—exploration to one pot synthesis of benzimidazoles

An economical and eco-compatible synthetic protocol for chemoselective and regioselective reduction of nitroaromatics in water has been achieved using easily accessible alumina-supported nickel nanoparticles as a stable recyclable heterogeneous catalyst. Various sensitive substituents like allyloxy, benzyloxy, t-butyldimethylsilyloxy, hydroxymethyl, alkoxycarbonyl, formyl, keto, carboxylic acid, chloro, bromo, azo and cyano were tolerated in the aforesaid protocol. This method has been extended for the construction of imidazole derivatives through one-pot reductive condensation of 2-nitroaniline with diversely substituted benzaldehydes. Some of the synthesized imidazoles have been used as antibacterial, antiplatelet and antithrombotic agents.