Excellent Catalytic Reactivity Research Articles

Highly efficient synthesis of isoprene from methyl tert-butyl ether and formaldehyde over activated carbon supported silicotungstic acid catalysts

In this contribution, we reported the liquid single-stage synthesis of isoprene from methyl tert-butyl ether (MTBE) and formaldehyde over activated carbon supported silicotungstic acid (STA/AC) catalysts. In comparison with the corresponding homogeneous STA catalysts, the STA/AC catalysts exhibited much higher activity of the prins condensation reaction under the same conditions. The results could be attributed to the highly dispersed STA, the relative weaker acidity resulting from the strong interaction between STA and AC and the structural collapse of STA. Additionally, the catalyst could be reused at least 3 times with only a slight decrease of activity. The physical and chemical properties of the STA/AC catalysts were characterized by means of DRIFT, HRTEM, HAADF-STEM, NH3-TPD, XRD, XPS and TG techniques. The excellent catalytic reactivity and easy recycling advantages make the STA/AC catalyst to be an attractive candidate of the prins reactions in the future.

High catalytic performance of an innovative Ni/magnesium slag catalyst for the syngas production and tar removal from biomass pyrolysis

The study aims to evaluate the catalytic potential of a Ni-based catalyst supported by magnesium slag (MS) for catalytic reforming of pyrolysis volatiles from pine sawdust. The catalysts were prepared by a wet impregnation method. The effects of different parameters (Ni loading content, calcination/catalytic bed temperature and steam to carbon (S/C) ratio) on the catalytic performance were investigated. In addition, tar cracking capability and coke deposition resistance of Ni/MS catalyst and Ni/γ-Al2O3 catalyst were explored under different calcination/catalytic bed temperatures. The catalysts were characterized by BET, XRD, SEM, TEM, TPO and Raman spectroscopy. The Ni/MS catalyst exhibited excellent catalytic reactivity as well as thermal stability. The best tar conversion (95.69%) and the highest hydrogen yield of 38.9 mmol/g biomass were obtained over Ni/MS catalyst under the conditions of Ni loading content = 3%, calcination/catalytic bed temperature = 800 °C, and S/C = 0.5. The interactions among Ni, Fe, Ca, and Mg formed multiple active centers (e.g., Ca2Fe2O5, (Ni, Mg) O solid solution and NiFe2O4) in the catalyst to show synergistic catalysis effects, thereby jointly improving catalyst activity and coke deposition resistance. Furthermore, both amorphous carbon and graphitic carbon were formed on the used catalysts and the D/G ratio (the relative intensity ratio between the D and G bands) was positively correlated with the catalytic activity.

Catalytic characteristics of innovative Ni/slag catalysts for syngas production and tar removal from biomass pyrolysis

In this study, innovative Ni-based catalysts supported by five typical slag carriers (magnesium slag (MS), steel slag (SS), blast furnace slag (BFS), pyrite cinder (PyC) and calcium silicate slag (CSS)) were prepared by wet impregnation. With the prepared catalysts and Ni/γ-Al2O3 catalyst, catalytic reforming of pyrolysis volatiles from pine sawdust for syngas production and tar removal was investigated. The catalysts were characterized by BET, XRD, SEM, TEM and Raman. The catalytic performances of the six catalysts were decreasing in the following order: Ni/MS > Ni/γ-Al2O3 > Ni/SS > Ni/BFS > Ni/CSS > Ni/PyC. Ni/MS catalyst exhibited excellent catalytic reactivity as well as thermal stability in terms of tar conversion (95.19%), gas yield (1.46 Nm3/kg) and CO2 capture ability (CO2 yield of 0.5%). Both amorphous carbon and graphite-type carbon were formed on the catalysts after catalytic reforming and the D/G ratio (the relative intensity ratio of the D-band to the G-band) was positively correlated to the catalytic activity.

Heterogeneous Palladium–Chitosan–CNT Core–Shell Nanohybrid Composite for Ipso-hydroxylation of Arylboronic Acids

A novel palladium-nanohybrid (Pd–Chitosan–CNT) catalytic composite has been developed using CNT–chitosan nanocomposite and palladium nitrate. The prepared catalytic platform displays excellent catalytic reactivity for the ipso-hydroxylation of various arylboronic acids with a mild oxidant aqueous H2O2 at room temperature, affording the corresponding phenols in excellent yields. Significantly, the easy recovery and reusability by simple manipulation demonstrate the green credentials of this catalytic platform.

Activation of peroxymonosulfate by magnetic catalysts derived from drinking water treatment residuals for the degradation of atrazine.

Magnetic catalysts (MCs) derived from iron-rich drinking water treatment residuals (WTRs) were prepared through pyrolysis treatment and introduced as activators of peroxymonosulfate (PMS) for refractory atrazine (ATZ) degradation. Comprehensive characterization analysis indicated that pyrolytic temperature could manipulate the crystalline structure evolution of the MCs and influence their physicochemical and catalytic properties. The catalytic performances of the as-prepared samples pyrolyzed at 600 °C (MC-600) and 1000 °C (MC-1000) were evaluated, and MC-1000 exhibited far more excellent catalytic reactivity than MC-600 in PMS oxidation system. Such difference was mainly attributed to that Fe3O4 and Fe° are the dominant active ingredients of MC-600 and MC-1000, respectively. The electron spin resonance (ESR) tests and radical quenching experiments revealed that hydroxyl radical (•OH) and sulfate radical (SO4•-) predominated in the MC-600/PMS and MC-1000/PMS systems, respectively. The mechanisms of the MCs-mediated PMS activation process were elucidated, among which the role of iron mineral phase was emphatically explored. Furtherly, possible degradation by-products were identified by LC-MS, and potential degradation pathways were proposed. Ultimately, the effects of pivotal parameters (i.e. MC-1000 dosage, PMS concentration, initial pH, and water matrix species) on ATZ degradation were investigated to assess the applicability of the MC-1000/PMS system.

Efficient visible-light-driven depolymerization of oxidized lignin to aromatics catalyzed by an iridium complex immobilized on mesocellular silica foams

A novel Ir(ppy)2(bpy) complex-containing mesoporous cellular silica foams (Ir(ppy)2(bpy)-MCFs) was prepared by a facile thiol-ene click reaction between the prefabricated thiol-functionalized mesoporous cellular silica foams and vinyl-tagged [Ir(ppy)2(bpy)]PF6 complex. The elaborate Ir(ppy)2(bpy)-MCFs material possessed the large surface area (355 cm2/g), open foam-like mesoporous structure with 30 nm cell pore size and 3.0 nm window pore size. Importantly, it had the well-defined molecular configuration of Ir(ppy)2(bpy) active species. As expected, it exhibited excellent catalytic reactivity and selectivity in the visible-light-driven reductive depolymerization of oxidized lignin β-O-4 model compounds including p-hydroxyphenyl (H)-, guaiacyl (G)- and syringyl (S)-type units under the mild conditions. Meanwhile, it showed the comparable catalytic efficiency with the corresponding homogeneous [Ir(ppy)2(bpy)]PF6 catalyst. These high catalytic performances could be attributed to aerogel-like three-dimensional pore structure and high visible-light transparency, which efficiently decreased the mass transfer resistance and the photon propagation hindrance. Furthermore, it could be easily recycled and reused at least six times without the remarkable loss of catalytic activity.

Synthesis and Catalytic Properties of New Sustainable Aluminosilicate Heterogeneous Catalysts Derived from Fly Ash

The field of heterogeneous catalysis has recently become increasingly interested in the utilization of industrial wastes as inexpensive precursors for active catalysts. Here we report a facile synthesis of fly-ash-based geopolymers as new highly reactive sustainable porous aluminosilicate heterogeneous catalysts for acidic and/or redox applications. The catalytic properties of these catalysts for Friedel–Crafts benzylation reactions of benzene and other substituted aromatics were thoroughly investigated. Fly ashes were collected from various sources were investigated, and the impact of the variation of their chemical and physical properties on the resulting catalysts was studied. The catalysts demonstrated excellent catalytic reactivity superior to other commonly used aluminosilicate catalysts such as M-zeolite, mesoporous molecular sieves, mixed oxides, and ionic liquids. This study not only highlights the feasibility of synthesizing active heterogeneous catalysts with predictable features from several different fly ash precursors but also suggests a new and very useful means for effectively utilizing fly ash.

Nanostructured Co3O4 grown on nickel foam: An efficient and readily recyclable 3D catalyst for heterogeneous peroxymonosulfate activation

Cobalt-based heterogeneous catalyst has been recognized as one of most efficient activators for peroxymonosulfate (PMS) decomposition, but usually suffers from the poor stability and difficulty to recover and reuse. Here easily recyclable cobalt oxide (Co3O4) nanowires and nanoflowers grown on nickel foam (NF) are fabricated by a hydrothermal and calcination method. The prepared 3D Co3O4/NF catalyst is characterized and applied as a heterogeneous catalyst for PMS activation to generate sulfate radicals for decomposition of Acid Orange 7 (AO7). The results show that the AO7 degradation rate increases with cobalt loading and PMS dosage, but decreases with the increase of solution pH. The Co3O4/NF catalyst using 2 mM Co(NO3)2·6H2O as cobalt source exhibits highest activity, and almost complete decolorization could be achieved within 30 min. The diverse effects of coexisting anions (SO42−, HCO3−, NO3− and Cl−) on AO7 degradation are observed and explained. After 10 consecutive runs, excellent catalytic reactivity of the catalyst remains while the level of leached cobalt during the catalyst usage is much lower than the maximum allowable concentration in drinking and natural water. More importantly, the macroscopic Co3O4/NF catalyst shows advantage of easy recycling after application compared to traditional catalysts. It is believed that the as-prepared Co3O4/NF is promising to be an effective and green heterogeneous catalyst for PMS activation to degrade organic pollutants for environmental application.

In(III) and Sc(III) based coordination polymers derived from rigid benzimidazole-5,6-dicarboxylic acid: Synthesis, crystal structure and catalytic property

Two new coordination polymers (CPs), [InCl(H2bidc)2(H2O)]n (1) and [Sc(Hbidc)(OH)(H2O)]n (2) (H3bidc = benzimidazole-5,6-dicarboxylic acid) were synthesized through a solvothermal approach. 1 exhibits a 1D infinite chain, which further constructs a 3D supramolecular framework via hydrogen bonds. 2 features a 3D supramolecular framework consisting of left- and right-handed chiral layers, which contain the left- and right-handed chiral spiral chains. The adjacent layers stack through π–π stacking interactions between benzene and imidazole rings. 1 exhibits excellent catalytic reactivity for the Strecker reaction and can be recycled four consecutive reactions with more than 95% conversion yields.

Multifunctional Single-Site Catalysts for Alkoxycarbonylation of Terminal Alkynes.

A multifunctional copolymer (PyPPh2 -SO3 H@porous organic polymers, POPs) was prepared by combining acidic groups and heterogeneous P,N ligands through the copolymerization of vinyl-functionalized 2-pyridyldiphenylphosphine (2-PyPPh2 ) and p-styrene sulfonic acid under solvothermal conditions. The morphology and chemical structure of the copolymer were evaluated using a series of characterization techniques. Compared with traditional homogeneous Pd(OAc)2 /2-PyPPh2 / p-toluenesulfonic acid catalyst, the copolymer supported palladium catalyst (Pd-PyPPh2 -SO3 H@POPs) exhibited higher activity for alkoxycarbonylation of terminal alkynes under the same conditions. This phenomenon could be attributed to the synergistic effect between the single-site Pd centers, 2-PyPPh2 ligands, and SO3 H groups, the outstanding swelling properties as well as the high enrichment of the reactant concentration by the porous catalyst. In addition, the catalyst could be reused at least 4 times without any apparent loss of activity. The excellent catalytic reactivity and good recycling properties make it an attractive catalyst for industrial applications. This work paves the way for advanced multifunctional porous organic polymers as a new type of platform for heterogeneous catalysis in the future.

CoSe2 nanoparticles embedded defective carbon nanotubes derived from MOFs as efficient electrocatalyst for hydrogen evolution reaction

Development of electrocatalysts for hydrogen evolution reaction (HER) with low overpotential and robust stability remained as one of the most serious challenges for energy conversion. In this work, CoSe2 nanoparticles embedded in defective carbon nanotubes (CoSe2@DC) was synthesized by a carbonization-oxidation-selenylation procedure of Co-based metal-organic frameworks (MOFs). The pre-oxidation treatment was a crucial step in introducing an increasing number of defects into carbon nanotubes, which promoted the reaction between Co@carbon and selenium and led to the enhanced HER performance. The as-prepared CoSe2@DC exhibited excellent HER catalytic reactivity with a low onset potential of −40mV vs. RHE, a small Tafel slope of 82mV dec−1 as well as a high current density with robust catalytic stability in 0.5M H2SO4. This work may provide a generic methodology for rational design and fabrication of the partially encased core-shell structure derived from MOFs as efficient HER electrocatalysts.

Preparation of Triazole Gold(III) Complex as an Effective Catalyst for the Synthesis of E‐α‐Haloenones

AbstractThe pyridyltriazole ligand was prepared and applied as a new ligand system for the coordination towards gold(III) cations. The resulting complex showed excellent stability and effective catalytic reactivity for the Meyer–Schuster rearrangement of propargyl alcohols and sequential allene halogenation, giving α‐haloenones with excellent yields and good E/Z selectivity. More importantly, by using this new gold(III) catalytic system, the challenging α‐chloroenone substrates were synthesized in good yields for the first time. This work also permits the avoidance of preparing of acetate derivatives as required in the case of Au(I) catalysts and validates that the triazole gold(III) complex is an effective new catalyst for alkyne activation.magnified image

In-situ transesterification of Jatropha oil over an efficient solid alkali using low leaching component supported on industrial silica gel

An efficient solid-base catalyst with low leaching K2MgSiO4 component on industrial silica gel was synthesized by a simple sol–gel method. The Jatropha biodiesel with high yield of 96.8% was produced by adopting in-situ esterification and transesterification reactions using the solid-base catalyst. The facile methanolysis process with excellent catalytic reactivity depends on the low leaching active component and surface base sites as well as easy dispersed particles in reaction medium. The eco-benign catalyst exhibited consistently high activity after being reused in five reaction runs.

Coal chemical-looping gasification of Ca-based oxygen carriers decorated by CaO

Chemical-looping gasification (CLG) for reacting coal with oxygen carriers to yield syngas is a clean and effective coal gasification technology. In the present investigation, a mechanical mixing-impregnation method was used to prepare a CaSO4–CaO/bentonite (CaSO4–CaO/Ben) compound oxygen carrier with excellent catalytic reactivity and stabilizing ability. An investigation on the reaction performance, cyclability and sulfur release of CaSO4–CaO/Ben was performed in a batch fluidized-bed reactor with steam as the gasification–fluidization medium. The results of this study demonstrate that the CaSO4–CaO/Ben compound oxygen carrier has excellent catalytic reactivity. At 900°C, the carbon conversion rate, cold gas efficiency and syngas content reached 96.84%, 84.28% and 66.98%, respectively. Furthermore, the addition of CaO can inhibit CaSO4 side reactions to improve the stability of the oxygen carrier. The cold gas efficiency, carbon conversion efficiency and syngas content exhibited slight changes during ten redox cycles, which indicates that the CaSO4–CaO/Ben oxygen carrier has excellent reactive stability. SEM images of the oxygen carrier after being recycled in ten redox reactions indicated that the surface of the oxygen carrier became porous, which favored CLG. The coal CLG kinetics could be well explained by an active site extending model, and the synergy of CaSO4 and CaO was verified during the coal CLG process.

Fe[sbnd]N[sbnd]C catalyst modified graphene sponge as a cathode material for lithium-oxygen battery

The cathode of a lithium-oxygen battery needs the synergism of a porous conducting material and a catalyst to facilitate the formation and decomposition of lithium peroxide. Here we introduce a graphene sponge (GS) modified with FeNC catalyst for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER). The porous, 3-dimensional conductive and free standing nature of the graphene sponge makes it become excellent skeleton of cathode for lithium-oxygen battery. The FeNC catalyst nanoparticles dispersed uniformly on the graphene sheets show excellent catalytic reactivity in both discharge and charge processes. This kind of composite material greatly improves the capacity and cyclability of the lithium-oxygen battery. With dimethyl sulphoxide as electrolyte, the capacity reaches 6762mAhg−1 which is twice of the pure graphene sponge. In addition, the cell containing FeNGS air electrode exhibits stable cyclic performance and effective reduction of charge potential plateau, indicating that FeNGS is promising as an OER catalyst in rechargeable lithium-air batteries.

Fe0-Fe3O4 nanocomposites embedded polyvinyl alcohol/sodium alginate beads for chromium (VI) removal

In this study, Fe0-Fe3O4 nanocomposites embedded polyvinyl alcohol (PVA)/sodium alginate (SA) beads were synthesized, which exhibited an excellent physical properties and catalytic reactivity, and a robust performance of post-separation (complete separation using a simple grille) and reusability (efficiency of 69.8% after four runs) in Cr(VI) removal. 5.0wt% PVA with 1.5wt% SA was the optimal proportion for beads molding, and the followed acidification and reduction treatments were critical to ensure high mechanical strength and high Cr(VI) removal ability of beads. Effects of Fe0 and Fe3O4 mass fraction, initial pH and Cr(VI) concentration on final removal efficiency were also evaluated. Merely 0.075wt% Fe0 together with 0.30wt% Fe3O4 was sufficient to deal with 20mgL−1 Cr(VI) solution. The efficiency decreased from 100 to 79.5% as initial Cr(VI) increased from 5 to 40mgL−1, while from 99.3 to 76.3% with increasing pH from 3.0 to 11.0. This work provides a practical and high-efficient method for heavy metal removal from water body, and simultaneously solves the problems in stabilization, separation and regeneration of Fe0 nanoparticles.

Synthesis and Reactivity of Silyl Iron, Cobalt, and Nickel Complexes Bearing a [PSiP]-Pincer Ligand via Si–H Bond Activation

The synthesis and characterization of a series of Ni, Co, and Fe complexes bearing a tridentate bis(phosphino)silyl ligand (κ3-(2-Ph2PC6H4)2SiMeH, [PSiP]-H, 1) are reported. 1 reacted with Ni(PMe3)4 to afford the mononuclear nickel(0) complex [η2(Si–H)-PSiP]Ni(PMe3) (2). The halogeno nickel complexes [PSiP]Ni(X)(PMe3) (X = Cl (3), Br (4), I (5)) were synthesized in the reactions of 2 with Me3SiCl or MeHSiCl2, EtBr, and MeI. Complex 2 underwent ligand substitution of PMe3 by CO to give [η2(Si–H)-PSiP]Ni(CO) (6). Complex 3 reacted with NaOMe to deliver [PSiP]Ni(OMe)(PMe3) (7) through anionic ligand substitution, while the neutral ligand replacement of PMe3 by CO in 3 afforded the rare hexacoordinate 20-electron nickel(II) complex [PSiP]Ni(Cl)(CO)2 (8). Unexpectedly, reaction of 1 with NiMe2(PMe3)3 produced the tetracoordinate nickel(0) complex [Me2PSiP]2Ni (9). The complex [Me2PSiP]Ni(CO)2 (10) was acquired from 9 after the substitution of one [PSiP] ligand by two carbonyl ligands. 1 reacted with Co(PMe3)4 or CoCl(PMe3)3 to afford the hydrido cobalt(II) complex [PSiP]CoH(PMe3) (11) or hydrido cobalt(III) complex [PSiP]Co(H)(Cl)(PMe3) (13). Complex 12, [PSiP]Co(H)(I)(PMe3), could be obtained from the reaction of MeI with 11 or 13. Treatment of 13 with 1 equiv of MeLi or n-BuMgBr in THF resulted in the clean formation of cobalt(I) complex [PSiP]Co(PMe3)2 (14) via reductive elimination. The simple anhydrous inorganic salt NiCl2 or CoCl2 could also react with 1 in the presence of PMe3 to form the corresponding silyl complexes 3 and [PSiP]Co(Cl)(PMe3) (15) via Si–H bond cleavage. 1 reacted with Fe(PMe3)4 to form the hexacoordinate octahedral hydrido iron(II) complex [PSiP]Fe(H)(PMe3)2 (16). The molecular structures of complexes 2–5, 10, 12, 13, 15, and 16 were determined by X-ray single crystal diffraction. 16 has excellent catalytic reactivity for the reduction of aldehydes and ketones.

Controlling the selectivity of the manganese/bicarbonate/hydrogen peroxide catalytic system by a biphasic pyrrolidinium ionic liquid/n-heptane medium

The Mn2+/HCO3−/H2O2 catalytic system exhibits excellent aldehyde selectivity in the oxidation of various benzylic and allyic alcohols under mild conditions and short reaction time when the reactions are carried out in a biphasic dicationic pyrrolidinium ionic liquid/n-heptane medium. The dicationic pyrrolidinium ionic liquid shows differential solubility towards alcohols and their aldehydes whereas the immiscible n-heptane instantaneously extracted and separated aldehydes from the reaction phase. This design of biphasic ionic liquid/n-heptane catalytic system prevents the over-oxidation of aldehydes to carboxylic acids effectively. Separation and recycling can also be easily done by decantation of the n-heptane layer after reaction. With the biphasic system, high conversion of benzyl alcohol to benzaldehyde was achieved with very low loadings of H2O2 and Mn(OAc)2 catalyst at room temperature and within short reaction time. Throughout 10 reaction cycles, a total turnover number (TON) of 37,600 was achieved and excellent catalytic reactivity and selectivity were maintained with an average yield of 94%.

A Novel Porous-Polymer-Supported Ru(II)-<i>dm</i>-Pheox Catalyst and its Application in Highly Efficient N-H Insertion Reactions

A novel macroporous polymer supported ruthenium (II) dimethyl phenyloxazoline (Ru (II)-dm-Pheox) catalyst has been developed by crosslinking polymerizing monomeric Ru (II)-dm-Pheox complex with styrene and 1,4-divinyl benzene (DVB) in the presence of 2,2-azobisizobutyronitrile (AIBN) and water. We evaluated the catalytic activity of our novel porous catalyst in the intermolecular N-H insertion of the commercially available ethyl diazoacetate (EDA) with various amines. The polymer supported catalyst showed excellent catalytic reactivity by delivering the amino acid derivatives in high yields after centrifugation.

Carbon nanotube–hydroxyapatite–hemoglobin nanocomposites with high bioelectrocatalytic activity

In this paper, carbon nanotubes–hydroxyapatite (MWCNTs–HA) composite were synthesized by self-assembling technique, and investigated by X-ray diffraction, scanning electron microscopy (SEM) and FT-IR spectroscopy. Hemoglobin (Hb) immobilized in MWCNTs–HA film not only retained its similarly native conformations, but also achieved the direct electron transfer. The apparent heterogeneous electron transfer rate constant ( k s) was evaluated as (5.05 ± 0.41) s − 1 according to Laviron's equation, and the surface coverage ( Γ*) was estimated as (9.25 ± 0.69) × 10 − 10 mol cm − 2 . Moreover, the Hb immobilized in MWCNTs–HA film exhibited remarkable bioelectrocatalytic activity for the electrochemical reduction of H 2O 2. The amperometric response of the biosensor varied linearly with the H 2O 2 concentration ranging from 0.5 μM to 2 μM, and the results showed a detection limit of 0.09 μM. Furthermore, the Hb-immobilized MWCNTs–HA film exhibited the excellent catalytic reactivity toward trichloroacetic acid (TCA).