Facile synthesis of a Co–B nanoparticle catalyst for efficient hydrogen generation via borohydride hydrolysis

A Co–B nanoparticle catalyst was prepared by a modified polyol method. Borohydride served both as a reducing agent for Co²⁺ and as a boron source, and the solvent, ethylene glycol, served as the surfactant and stabilizer to assemble Co–B clusters into small and uniform particles. The as-prepared Co–B possessed high surface active metal area and highly unsaturated coordinated Co metal, resulting in lower activation energy and higher hydrogen generation rate for hydrolysis of alkaline NaBH₄ solution than the conventional Co–B catalyst synthesized from chemical reduction in water bath.     

Intramolecular selective hydrogenation of cinnamaldehyde over CeO2–ZrO2-supported Pt catalysts

Selective liquid phase hydrogenation of cinnamaldehyde is reported, for the first time, over CeO₂, ZrO₂, and CeO₂–ZrO₂-supported Pt catalysts. Cinnamyl alcohol is the selective product. These catalysts are highly active and selective even at 25 °C and found to be superior to most of the hitherto known supported Pt catalysts. Alkali addition (NaOH) has enhanced the performance of these catalysts. At an optimized reaction condition, 95.8% conversion of cinnamaldehyde and 93.4% selectivity of cinnamyl alcohol have been obtained. Acidity of the support (due to the presence of ZrO₂ component) and higher electron density at Pt (due to CeO₂ component) are attributed to be responsible for the superior catalytic activity of Pt supported on CeO₂–ZrO₂ composite material.     

Ultrafine Ni–Co–W–B amorphous alloys and their activities in benzene hydrogenation to cyclohexane

Quaternary Ni–Co–W–B amorphous alloys were prepared by chemical reduction of the aqueous solution of nickel and cobalt salts and sodium tungstate with potassium borohydride. The catalytic activities of the as-prepared materials were measured through liquid phase hydrogenation of benzene under moderate pressure. In comparison with Ni–Co–B, the as-prepared Ni–Co–W–B amorphous alloys showed superior activity, attributable to the promoting effect of tungsten on the microstructure of the alloys as revealed by XPS, XRD and DSC measurements.     

Effect of preparation method on catalytic performance,structure and surface reaction rates of MgO supported Fe–Co–Mn catalyst for CO hydrogenation

The MgO supported Fe–Co–Mn catalyst was prepared using different preparation methods including co-precipitation, sol–gel, incipient wetness impregnation and dry impregnation. All of these catalysts were tested for Fischer–Tropsch synthesis under the same operational conditions of T = 300 °C, P = 1 bar, H₂/CO = 2/1 and GHSV = 4500 h^?1. It was found that the co-precipitated catalyst has shown the better catalytic performance for CO hydrogenation. The effect of the preparation method on different surface reaction rates was also investigated and it was found that the preparation methods can influenced the rates of different surface reaction rates. Catalyst characterization was carried out using XRD, SEM, BET, TPR, TGA and DSC.     

Effect of boric oxide doping on the stability and activity of a Cu–SiO2 catalyst for vapor-phase hydrogenation of dimethyl oxalate to ethylene glycol

Stable and efficient B–Cu–SiO₂ catalysts for the hydrogenation of dimethyl oxalate (DMO) to ethylene glycol were prepared through urea-assisted gelation followed by postimpregnation with boric acid. Auger electron spectroscopy and CO adsorption by in situ Fourier transform infrared spectroscopy revealed that the Cu⁺ species on the catalyst surface increased together with an increase in the amount of boric oxide dopant. X-ray diffraction and N₂O chemisorption indicated that a suitable amount of boric oxide doping tended to improve copper dispersion and retard the growth of copper particles during DMO hydrogenation. Catalytic stability was greatly enhanced in the B–Cu–SiO₂ catalyst with an optimized Cu/B atomic ratio of 6.6, because of the formation and preservation of appropriate distributions of Cu⁺ and Cu⁰ species on the catalyst surfaces. The effect of boric oxide was attributed to its relatively high affinity for electrons, which tended to lower the reducibility of the Cu⁺ species.     

Effect of calcination and reaction conditions on the catalytic performance of Co–Ni/Al2O3 catalyst for CO hydrogenation

The Co–Ni/Al₂O₃ catalysts prepared using impregnation procedure, were used for the Fischer–Tropsch synthesis. The effect of calcination conditions of the catalyst as well as reactor situation was studied. It was found that the catalyst calcined at 550 °C for 6 h in air atmosphere has shown the best catalytic performance for CO hydrogenation. The best operational conditions were obtained as following: T = 350 °C, P = 1 atm and H₂/CO = 2/1.     

Exploration of cinnamaldehyde hydrogenation in Co–Pt/γ‐Al2O3 catalytic membrane reactors

The feasibility of Co–Pt/γ‐Al₂O₃ catalytic membrane reactors for cinnamaldehyde hydrogenation has been explored. The results of hydrogenation in four membrane reactors with different configurations indicate that the effect of the gas transport limitation is more important than the liquid diffusion limitation. The membrane with the catalytic layer situated on the gas side shows the highest activity due to the minimized gas transport limitation. This revised version was published online in July 2006 with corrections to the Cover Date.     

Liquid-phase transfer hydrogenation of furfural to furfuryl alcohol on Cu–Mg–Al catalysts

The liquid-phase transfer hydrogenation of furfural on Cu-based catalysts was studied. Catalysts were prepared by incipient wetness impregnation (Cu/SiO₂) and co-precipitation (Cu–Mg–Al). The effect of metal-support interaction, hydrogen donor, copper loading and temperature on catalytic performance was evaluated. Small particles, strongly interacting with a spinel-like matrix, had higher capability for transferring hydrogen than large ones having low interaction with support. An important increase in reaction rate was observed when temperature was raised from 110 to 150 °C. Thus, it was possible to attain complete furfural conversion to furfuryl alcohol with Cu(40%)–Mg–Al after 6 h at 150 °C.     

Gold–palladium supported on porous steel fiber matrix: Structured catalyst for benzyl alcohol oxidation and benzyl amine oxidation

Au, Pd and Au-Pd alloy are deposited on porous steel fiber matrices via sputtering technique. By this technique the preparation of the heterogeneous catalysts is clean, simple and fast as noble metal complexes, solvents or reducing agents are not needed. The studied Au-Pd catalyst exhibits good activity in the aerobic oxidation of benzyl alcohol and benzyl amines. Especially in the oxidation of benzyl amines, the Au-Pd catalyst shows a great synergistic enhancement in the activity.     

Kinetic study of CO hydrogenation on the MgO supported Fe–Co–Mn sol–gel catalyst

The kinetic of the Fischer–Tropsch synthesis over the MgO supported Fe–Co–Mn catalyst prepared using sol–gel procedure, was investigated in a fixed bed micro-reactor. Experimental conditions were varied as follow: reaction pressure 5–20 bar, reaction temperature 220–250 °C, H₂/CO feed molar ratio of 0.67–2 and space velocity range of 2400–3600 h^?1. 18 models according to the Langmuir–Hinshelwood–Hougen–Watson (LHHW) type rate equation were derived, and the reaction rate is fitted fairly well by one kinetic expressions based on LHWW mechanism. The kinetic parameters were estimated with non-linear regression method. The activation energy was obtained 110.9 kJ/mol for the best-fitted model.     

Electroless deposition of Ni–B, Co–B and Ni–Co–B alloys using dimethylamineborane as a reducing agent

Fundamental aspects of electroless Ni–B, Co–B and Ni–Co–B alloys have been systematically examined. The composition, crystal structure and deposition rate of the alloys were determined as a function of the concentration of reducing agent (dimethylamineborane) and complexing agents (tartrate, citrate, malonate and succinic acid), bath pH and Ni2+/Co2+ ratio. Changes in the deposition rate and metallurgical features of the alloys induced by the change in plating parameters are discussed, based on electrochemical polarization data and the formation enthalpy of the nickel and cobalt borides.     

Synthesis of waterborne polyurethane–silver nanoparticle antibacterial coating for synthetic leather

An antibacterial coating composed of silver nanoparticles and waterborne polyurethane was synthesized for use on synthetic leather. In this study, silver nanoparticles were prepared and used as nanofiller to impart antibacterial property. Silver nanoparticles were synthesized by using poly(vinyl pyrrolidone) as dispersant and sodium borohydride (NaBH₄) as reducing agent. Silver nanoparticles were characterized by transmission electron microscopy (TEM), Fourier-transform infrared (FTIR) spectroscopy, and X-ray diffraction (XRD) analysis. The optimum dispersant was selected according to the zeta potential of dispersions. Waterborne polyurethane was synthesized by using isophorone diisocyanate, 2-bis(hydroxymethyl)propionic acid, triethylamine, and polytetramethylene ether glycol. Waterborne polyurethane–silver antibacterial coating was obtained by ultrasonic dispersion, and then cast on the surface of synthetic leather. The antibacterial property and coating adhesion were investigated. The results showed silver nanoparticles homogeneously dispersed in waterborne polyurethane and adhesion reaching grade 4. Antibacterial testing showed bacterial reduction of 99.99% for Escherichia coli and 87.5% for Staphylococcus aureus.     

Promotion effect of the addition of Eu to Co/silica catalyst for Fischer–Tropsch synthesis

Co/silica (Eu–Co/SiO₂) catalysts with 1, 5, 10, and 20% Eu were synthesized and their catalytic activities towards Fischer–Tropsch synthesis were investigated in a slurry-phase reactor. The addition of 1% Eu improved the activity of the Co/SiO₂ catalyst, while more than 5% Eu reduced it. XRD and XANES analyses revealed that Eu has a negligible effect on the Co metal particle sizes of the reduced catalysts and that 1% Eu enhanced the reducibility of the Co oxides while excess Eu was ineffective. This is the first report demonstrating the promotion effect of Eu on FTS reaction of Co/SiO₂ catalyst.     

Ag–Cu–BTC prepared by postsynthetic exchange as effective catalyst for selective oxidation of toluene to benzaldehyde

A mixed-node MOF catalyst Ag–Cu–BTC was prepared by postsynthetic exchange (PSE) method. It is believed that PSE method can realize isomorphous replacement of Ag ion to framework Cu ion in Cu–BTC successfully. The catalytic performance of Ag–Cu–BTC was investigated via selective oxidation of toluene to benzaldehyde by molecular oxygen in the absence of solvent and initiator. This catalyst exhibits good catalytic performance: on the premise of keeping highly selective catalysis of Cu–BTC for toluene oxidizing to benzaldehyde, the introduction of Ag (Ag content is 2.76 wt.%) can promote toluene conversion from 6.5% to 12.7%.     

Preparation of Pd–Pb/α-Al2O3 catalysts for selective hydrogenation using PbBu4: the role of metal–support boundary atoms and the formation of a stable surface complex

Pd–Pb/α-Al₂O₃ catalysts were prepared by reacting PbBu₄ with supported palladium samples derived from Pd(AcAc)₂, both in the presence and absence of hydrogen. The amount of lead fixed depends mainly on the concentration of palladium on the metal–support boundary. In the presence of hydrogen, all butyl groups are released during the anchoring process. When the Pd/α-Al₂O₃ was reduced and then purged with nitrogen, two butyl groups remained attached to the lead atom and a stable surface complex was formed. The analysis of gaseous products evolved during the PbBu₄–Pd/α-Al₂O₃ interaction and subsequent temperature‐programmed reaction experiments indicate that a (]‐L)₂–Pb(Bu)₃ complex was obtained. Upon reduction at 573 K, the Pd–Pb/α-Al₂O₃ catalysts became very selective for the hydrogenation of acetylene in the presence of ethylene. This revised version was published online in July 2006 with corrections to the Cover Date.     

Preparation and characterization of ordered mesoporous Mg–Al–Co hydrotalcite based catalyst for decarboxylation of jatropha oil

This paper reported preparation of novel order mesoporous Mg–Al–Co hydrotalcite based catalysts through sol–gel procedure using precursors such Mg(NO₃)₂, Al(NO₃)₃ and Co(NO₃)₂ and Na₂CO₃. The catalyst also contained both acidity and basicity being very convenient for decarboxylation process of vegetable oil to green hydrocarbons. The alkaline media was maintained at pH 10 during the processes. Molar ratio of metal cations and temperature of the sol–gel processes were investigated for their effect in the mesoporous structure formation. The results showed that the procedure should be established at 70 °C with the molar Mg/Al/Co ratio of 1/5/0.2. Acidity and basicity of the mesoporous hydrotalcite based catalyst were demonstrated for their co-existence. The as-synthesized material at the suitable conditions was used as catalyst for decarboxylation of jatropha oil to obtain green hydrocarbons mainly belonging to diesel fraction. The decarboxylation was carried out at 400 °C for 3 h in closed auto-pressurized reactor exhibiting a yield of diesel involving hydrocarbons of over 70% after distillation and analysis. The result also confirmed that the acidity and basicity greatly accelerated the activity of the catalyst. Some techniques were used to characterizing the catalyst including XRD, SEM, TEM, TGA, NH₃-TPD, CO₂-TPD and BET, and GC–MS was also used to analyze the main product composition.     

Size-controlled Pd nanoparticles supported on α-Al2O3 as heterogeneous catalyst for selective hydrogenation of acetylene

Size-controlled Pd nanoparticles （PdNPs） were synthesized in aqueous solution, using sodium car-boxymethyl cellulose as the stabilizer. Size-controlled PdNPs were supported onα-Al2O3 by the incipient wetness impregnation method. The PdNPs onα-Al2O3 support were in a narrow particle size distribution in the range of 1-6 nm. A series of PdNPs/α-Al2O3 catalysts were used for the selective hydrogenation of acetylene in ethylene-rich stream. The results show that PdNPs/α-Al2O3 catalyst with 0.03%（by mass） Pd loading is a very effective and sta-ble catalyst. With promoter Ag added, ethylene selectivity is increased from 41.0%to 63.8%at 100 ＆#176;C. Comparing with conventional Pd-Ag/α-Al2O3 catalyst, PdNPs-Ag/α-Al2O3 catalyst has better catalytic performance in acety-lene hydrogenation and shows good prospects for industrial application.     

Synthesis and application of a novel strong and stable supported ionic liquid catalyst with both Lewis and Brønsted acid sites

Poly(4-vinylpyridine)-supported ionic liquid with both Lewis and Brønsted acid sites was easily prepared from its starting materials and used as a novel and highly efficient heterogeneous catalytic system for the synthesis of biscoumarins by two-component one-pot domino Knoevenagel-type condensation/Michael reaction between various aliphatic and aromatic aldehydes with 4-hydroxycoumarin. The Lewis and Brønsted acidic sites loading in [P₄VPy-BuSO₃H]Cl-X(AlCl₃) were found to be 2.15 and 0.9 mmol per gram of catalyst, respectively. The effect of the simultaneous presence of Lewis and Brønsted acid sites was evaluated. The catalyst was characterized by Fourier transform infrared spectroscopy (FT-IR), thermal gravimetric analysis (TGA), scanning electron microscopy (SEM), elemental analysis, and atomic absorption technique. The catalyst is stable (as a bench top catalyst) and reusable.     

Hydrothermal study of Pt–Sn-based SAPO-34 supported novel catalyst used for selective propane dehydrogenation to propylene

Catalyst's regeneration is unavoidable part during dehydrogenation. The hydrothermal treatment influence on the performance of Pt–Sn-based SAPO-34 supported novel catalyst, used for propane dehydrogenation to propylene is investigated in this study. The catalyst shows excellent stability for mild steaming (nitrogen mixed steam), during four consecutive runs (reaction–regeneration mode). On the other hand, Pt–Sn/ZSM-5 was largely affected on mild steaming due to severe dealumination. In order to get into mechanistic understanding, severe hydrothermal treatment was carried our using pure steam. The substation loss in catalyst activity was noted. Both fresh and severe hydrotreated catalysts were characterized by XRD, XRF, O₂-pulse analysis of coke, NH₃-TPD, IR spectrum of adsorbed ammonia, H₂-TPR, HR-TEM and XPS, to explore reasons for change in catalytic properties. The texture/topology is found stable. Changes in surface ensembles occur due to the loss of Sn, Al, formation of SnO_x species and in particular Pt sintering. This leads Pt active sites (zeolite–SnO–Pt) to inactive sites (zeolite–Pt, zeolite–PtO–Sn, Pt–Sn alloy, etc.) formation and reduced catalyst activity. TEM micrographs and H₂-chemisorption analysis confirms Pt particles agglomeration and/or sintering. About 98% catalyst activity is recovered by re-dispersed Pt using chlorination technique and credit goes to hydrothermally stable support (SAPO-34).     

On the promotional effect of Sn in Co–Sn/Al2O3 catalyst for NO selective reduction

NO reduction with propylene over Co/Al₂O₃ and Co–Sn/Al₂O₃ catalysts has been investigated. For the Co/Al₂O₃ catalyst, a calcination temperature exceeding 800°C led to a decrease of NO conversion. Calcination of the Co/Al₂O₃ catalyst at 1000°C resulted in the formation of -Al₂O₃ and Co₃O₄. The presence of 20% water vapor showed a significant shift for the maximum NO reduction temperature from 450 to 600°C over Co/Al₂O₃. It has been found that modification of 6 wt% Co/Al₂O₃ with 2 wt% Sn significantly enhanced the catalyst thermal stability and improved the inhibitory effect of water on NO conversion and reaction temperature. The promotional effect of Sn on the catalyst thermal stability was attributed to the suppression of the phase transformation from highly dispersed Co²⁺ species on -Al₂O₃ to -Al₂O₃ and Co₃O₄. The smaller influence of water vapor on NO reduction conversion and temperature over Co–Sn/Al₂O₃, compared to Co/Al₂O₃, was attributed to the dispersion effect of Sn species on Co²⁺ species as well as the involvement of Sn species in NO reduction at a relatively lower temperature. The synergetic effect between the octahedral Co²⁺ species and -alumina plays a significant role in the catalysis of NO selective reduction by C₃H₆.