Catalytic conversion of cellulose into polyols using carbon-nanotube-supported monometallic Pd and bimetallic Pd–Fe catalysts

A series of carbon nanotube (CNT)-supported monometallic Pd and bimetallic Pd–Fe catalysts were synthesized and employed for catalytic hydrogenolysis of cellulose into polyols, including hexitol, ethylene glycol (EG), 1,2-propanediol (1,2-PG), and glycerol (Gly). The physicochemical properties of the catalysts were characterized by nitrogen physical adsorption measurements, X-ray diffraction analysis, transmission electron microscopy, and X-ray photoelectron spectroscopy. The total yield of hexitol, EG, 1,2-PG, and Gly in hydrolytic hydrogenation of cellulose was 37, 55, and 53% for Pd/CNTs, Pd–Fe/CNTs (Pd:Fe = 1:1), and Pd–Fe/CNTs (Pd:Fe = 1:2), respectively. Addition of Fe to Pd significantly modified the physicochemical properties of the nanoparticles and their catalytic performance, especially regarding hexitol selectivity. The promoting effect of Fe, especially for hexitol selectivity, compared with the monometallic catalyst is due to the fact that incorporation of Fe may stabilize Pd⁰ nanoparticles and lead to downshift of the d-band center of Pd metal nanoparticles by charge transfer from Fe to Pd. Recycling experimental results showed that leaching of Fe resulted in a significant decrease in the hexitol yield obtained using the Pd–Fe/CNTs after the first recycle, further demonstrating that Fe element plays a promoting role for hexitol formation.     

Controlled green synthesis of Au–Pt bimetallic nanoparticles using chlorogenic acid

Research on Chemical Intermediates - Well-dispersed Au–Pt alloyed bimetallic nanoparticles are synthesized using chlorogenic acid as the only reducing agent and stabilizer to reduce Au/Pt...     

Hydrogenolysis of glycerol to propanediols over supported Ag–Cu catalysts

Hydrogenolysis of glycerol to 1,2-propanediol and 1,3-propanediol has significant scientific importance and commercial interest due to the huge surplus of glycerol and the various application of propanediols. A series of supported Ag–Cu catalysts synthesized by impregnation method were studied for hydrogenolysis of glycerol to propanediols. The catalysts were characterized by H₂-TPR, NH₃-TPD, XRD, BET, N₂O chemisorption, TG, ICP and SEM. It was observed that the loading of 5% Ag–Cu-based catalysts facilitated the reduction, surface acidity and dispersion of the Cu particles, which improved the conversion of glycerol and promoted the generation of propanediols. It was also found that when loading Ag and Cu simultaneously on Al₂O₃, the catalyst had a better performance for the reaction because of the higher acidity, dispersion and surface area of the Cu species on the catalyst surface. In addition, effects of metal concentrations, metal impregnation sequence, reaction temperature, reaction pressure, reaction time, solvent and pH value of the solution on glycerol hydrogenolysis together with the recyclability of catalyst were investigated in detail. The optimal 5Ag–15Cu/Al₂O₃ achieved 66.4% glycerol conversion with 68.2% 1,2-propanediol and 3.1% 1,3-propanediol selectivity at 200 °C under 3.5 MPa in ethanol for 8 h.     

Catalytic oxidation of NO over Mn–Co–Ce–Ox catalysts: effect of reaction conditions

Manganese–cobalt–cerium oxide (Mn–Co–Ce–Ox) catalysts were synthesized by the co-precipitation method and tested for activity in low-temperature catalytic oxidation of NO in the presence of excess O₂. With the best Mn–Co–Ce mixed-oxide catalyst, approximately 80 % NO conversion was achieved at 150 °C and a space velocity of 35,000 h^?1. The effect of reaction conditions (reaction temperature, volume fractions of NO and O₂, gas hourly space velocity (GHSV), and catalyst stability) was investigated. The optimum reaction temperature was 150 °C. Increasing the O₂ content above 3 % results in almost no improvement of NO oxidation. This catalyst enables highly effective removal of NO within a wide range of GHSV. Furthermore, the stability of the Me–Co–Ce–Ox catalyst was excellent; no noticeable decrease of NO conversion was observed in 40 h.     

Fischer–Tropsch synthesis over iron catalysts with corncob-derived promoters

A sustainable strategy for Fischer–Tropsch iron catalysts is successfully achieved by embedding of synergistic promoters from a renewable resource, corncob. The iron-based catalysts, named as "corncob-driven"catalysts, are composed of iron species supported on carbon as primary active components and various minerals(K, Mg, Ca, and Si, etc.) as promoters. The corncob-driven catalysts are facilely synthesized by a one-pot hydrothermal treatment under mild conditions. The characterization results indicate that the formation of iron carbides from humboldtine is clearly enhanced and the morphology of catalyst particles tends to be more regular microspheres after adding corncob. It is observed that the optimized corncob-driven catalyst exhibits a higher conversion than without promoters' catalyst in Fischer–Tropsch synthesis(ca. 73% vs. ca. 49%). More importantly, a synergistic effect exists in multiple promoters from corncob that can enhance heavy hydrocarbons selectivity and lower CO_2 selectivity, obviously different from the catalyst with promoters from chemicals. The proposed synthesis route of corncob-driven catalysts provides new strategies for the utilization of renewable resources and elimination of environmental pollutants from chemical promoters.     

Catalytic combustion of methane over nano ZrO2-supported copper-based catalysts

The nano ZrO2-supported copper-based catalysts for methane combustion were investigated by means of N2 adsorption, TEM, XRD, H2-TPR techniques and the test of methane oxidation. Two kinds of ZrO2 were used as support, one （ZrO2-1） was obtained from the commercial ZrO2 and the other （ZrO2-2） was issued from the thermal decomposition of zirconium nitrate. It was found that the CuO/ZrO2-2 catalyst was more active than CuO/ZrO2-1. N2 adsorption, H2-TPR and XRD measurements showed that larger surface area, better reduction property, presence of tetragonal ZrO2 and higher dispersion of active component for CuO/ZrO2-2 than that of CuO/ZrO2-1. These factors could be the dominating reasons for its higher activity for methane combustion.     

Synthesis of polyester by means of polycondensation of diol ester and dicarboxylic acid ester through ester–ester exchange reaction

Based on our finding that the ester-ester exchange reaction between butyl benzoate and ethyl 4-phenylbenzoate in the presence of a metal alkoxide is faster than the ester-alcohol exchange reaction of butyl benzoate and ethanol, we investigated the synthesis of polyester through ester-ester exchange reaction under various conditions. The polycondensation of diol formate and methyl dicarboxylate in the presence of a catalytic amount of potassium tert-butoxide (^tBuOK) in diglyme at 120 °C under reduced pressure (90–100 Torr) afforded high-molecular-weight polyesters. Methyl dicarboxylate containing an amino group could be used for this polycondensation, although the corresponding diacid chloride containing an amino group was not isolable. The ester-ester exchange reaction could proceed even at the polyester backbone, and the reaction of poly(1,12-dodecamethylene isophthalate) ( PEs ₁ ) with poly(ε-caprolactone) (PCL) in the presence of ^tBuOK at 140 °C afforded a copolymer PEs ₁ -stat-PCL, the structure of which was confirmed by ¹³C NMR spectroscopy and DSC thermal analysis. A similar copolymer was also obtained by the polycondensation of dodecane-1,12-diol formate and dimethyl isophthalate in the presence of PCL and ^tBuOK at 120 °C under reduced pressure.     

Kinetic studies of methanol synthesis from CO_2+H_2 over copper based catalysts

The catalytic activity for the synthesis of methanol from carbon dioxide and hydrogen wasmeasured on various binary and ternary catalysts containing copper oxide under a pressure of 10 atm.Among these samples the catalysts, CuO/ZnO/γ-Al_2O_3, demonstrated the highest activity andselectivity to methanol; MnO, as third component, had no promotional effect on the activity of meth-anol formation. Based on a simple power rate law the apparent activation energy estimation and par-tial pressure dependence measurement were accomplished over eight catalysts. The activation energiesvaried from 40 to 120 kJ / mol depending on the composition of catalysts. The rates of methanol for-mation to be 0.3 -- 0.9 order in H_2 and about 0.1 -- 0.2 order in CO_2 were reported.     

Shape-selective isopropylation of naphthalene over H–mordenite catalysts for environmentally friendly synthesis of 2,6-dialkylnaphthalene

Recent development of advanced polymer materials such as polyethylene naphthalate, polybutylene naphthalate and liquid crystalline polymers has created an increasing demand for 2,6-dialkylnaphthalene, which has spurred interest in shape-selective naphthalene alkylation. This work deals with mordenite-catalyzed shape-selective naphthalene isopropylation to produce 2,6-diisopropylnaphthalene (2,6-DIPN). Effects of dealumination of mordenite on the structural and acidic characteristics and on the shape selectivity and activity were examined by physicochemical analysis, TPD, solid-state ²⁷Al and ²⁹Si MAS NMR, XRD, as well as catalytic alkylation reactions. Dealumination removes octahedral Al species as well as tetrahedral Al species, decreases the unit cell dimensions and reduces the number of strong acid sites in mordenites. Proper dealumination can improve selectivity to 2,6-DIPN from 33 to 61 % and significantly increases 2,6/2,7 ratio. Improved selectivity to 2,6-DIPN upon proper dealumination was attributed to the decrease in mordenite acidity, reduction in unit cell dimension and removal of some strong acid sites. However, neither the change in selectivity nor that in activity is a simple function of dealumination degree or SiO₂/Al₂O₃ ratio. Some minor difference in the apparent framework SiO₂/Al₂O₃ ratio can result in a major difference in activity or selectivity. There exist optimum conditions of dealumination as well as optimum reaction conditions for achieving higher selectivity to 2,6-DIPN.     

Catalytic reduction of NO by CO over Pd — doped Perovskite-type catalysts

The perovskite type oxides (nominal formula LaTi_0.5Mg_0.5O₃) with addition of Pd were prepared by annealing the ethanol solution of precursors in nitrogen flow at 1200°C and characterized by X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and temperature programmed desorption of NO (NO-TPD). Their activity was evaluated for NO reduction by CO under stoichiometric and oxidizing conditions and for direct decomposition of NO. Pd substituted samples exhibited high NO reduction activity and selectivity towards N₂. Nearly complete elimination of NO was achieved at 200°C. Two simultaneous reactions, NO reduction by CO and direct decomposition of NO as well as two forms of NO adsorption were observed on the surface of Pd substituted perovskite samples. The distribution of Pd in different catalytically active sites or complexes on at the catalyst surface may be responsible for the proceeding of two reactions: NO reduction with CO and direct NO decomposition.      

Stereoselective synthesis of conjugated all-trans-tetraenes. Application to the synthesis of β-parinaric acid methyl ester

in this paper is reported the stereoselective synthesis of all-trans-tetraenes by reductive elimination of 1,8-dibenzoate-2,4,6-trienes with sodium amalgam. The method was applied to the syntheses of 4E, 6E, 8E, 10E-heptatetraene and β—parinaric acid methyl ester.     

Cooperative effect of Fe and Ti species over Fe–Ti–Ox catalysts on the catalytic hydrolysis performance of hydrogen cyanide

FeO_x, TiO₂, and Fe–Ti–O_x catalysts were synthesized and used in the catalytic hydrolysis of hydrogen cyanide (HCN). Nearly 100% HCN conversion was achieved at 250 °C over the Fe–Ti–O_x catalyst. TiO₂ rutile was detected over TiO₂, but not over Fe–Ti–O_x, which suggested that the interaction between Fe and Ti species could inhibit the TiO₂ phase transition. Furthermore, the interaction between Fe and Ti species over Fe–Ti–O_x could promote the selectivity of NH₃ and CO. The mechanism of hydrolysis of HCN over FeO_x, TiO₂, and Fe–Ti–O_x can be given as follows: HCN + H₂O → methanamide → ammonium formate → formic acid → H₂O + CO.     

Decomposition of methane over alumina supported Fe and Ni–Fe bimetallic catalyst: Effect of preparation procedure and calcination temperature

Catalytic decomposition of methane has been studied extensively as the production of hydrogen and formation of carbon nanotube is proven crucial from the scientific and technological point of view. In that context, variation of catalyst preparation procedure, calcination temperature and use of promoters could significantly alter the methane conversion, hydrogen yield and morphology of carbon nanotubes formed after the reaction. In this work, Ni promoted and unpromoted Fe/Al₂O₃ catalysts have been prepared by impregnation, sol–gel and co-precipitation method with calcination at two different temperatures. The catalysts were characterized by X-ray diffraction (XRD), N₂ physisorption, temperature programmed reduction (TPR) and thermogravimetric analysis (TGA) techniques. The catalytic activity was tested for methane decomposition reaction. The catalytic activity was high when calcined at 500 °C temperature irrespective of the preparation method. However while calcined at high temperature the catalyst prepared by impregnation method showed a high activity. It is found from XRD and TPR characterization that disordered iron oxides supported on alumina play an important role for dissociative chemisorptions of methane generating molecular hydrogen. The transmission electron microscope technique results of the spent catalysts showed the formation of carbon nanotube which is having length of 32–34 nm. The Fe nanoparticles are present on the tip of the carbon nanotube and nanotube grows by contraction–elongation mechanism. Among three different methodologies impregnation method was more effective to generate adequate active sites in the catalyst surface. The Ni promotion enhances the reducibility of Fe/Al₂O₃ oxides showing a higher catalytic activity. The catalyst is stable up to six hours on stream as observed in the activity results.     

Catalytic combustion of benzene over CuO/CeO2 catalysts prepared using the precipitation–deposition method

Research on Chemical Intermediates - Catalytic combustion of benzene over CeO2-supported copper oxides has been investigated. The supported copper oxide catalysts were prepared by use of the...     

Steam reforming of methanol over mesoporous Cu–Al spinel catalysts synthesized by mechanochemical method

Hydrogen production for fuel cells via on-board steam reforming of methanol is a promising approach. In this study, an ammonium carbonate-assisted mechanochemical procedure has been developed for Cu-based catalyst synthesis for SRM. Catalytic performance in SRM was evaluated in a fixed bed reactor at varied conditions, and physical and structure properties of the catalysts were characterized by N₂ adsorption-desorption, N₂O titration, SEM, H₂-TPR, XRD and TG, etc. Mechanical milled samples exhibited a porous structure that differed from that of the catalyst prepared by conventional impregnation. The SRM activity was enhanced for the strong interaction between copper ions and the copper aluminate formed on the ball-milled catalysts. Cu₁Zn₃Al₆ exhibited the worst in activity, which could be ascribed to the poor metal dispersion. Cu–Al spinel in the catalysts plays an important role in the catalytic stability, which has prevented Cu from quick sintering in SRM, and the ball-milled catalysts have exhibited a slight deactivation with the time-on-stream of 25 ?h.     

Effects of glow discharge plasma on Cu–Co–Al-based supported catalysts for higher alcohol synthesis

The novel plasma assisted Cu–Co/γ-Al₂O₃ catalysts were prepared by incipient impregnation method for CO hydrogenation to higher alcohols and characterized by means of scanning electron microscopy (SEM), N₂ adsorption, X-ray powder diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) techniques. It was found that introduction of plasma significantly improved the specific surface area, dispersion of catalyst and the enrichment of active species on the surface of catalysts. Under the conditions of P = 5.0 MPa, GHSV = 6,000 h⁻¹, V(H₂)/V(CO) = 2, T = 573 K, the conversion of carbon monoxide over the plasma enhanced catalyst increased by 41.9% compared with that of the conventional sample, and the space time yield reached 337.1 g kg⁻¹ h⁻¹.     

Catalytic transfer hydrogenation of levulinate ester intoγ-valerolactone over ternary Cu/ZnO/Al_2O_3 catalyst

An effective catalytic transfer hydrogenation(CTH) process of bio-based levulinate esters into γ-valerolactone(GVL) was explored over ternary Cu/ZnO/Al_2O_3 catalyst which was prepared by coprecipitation method and could be sustainably used. As a result, quantitative conversion of ethyl levulinate(EL) and 99.0% yield of GVL were obtained in the CTH process using i-PrOH as hydrogen donor.The Cu/ZnO/Al_2O_3 catalyst with high-surface-area could be reused at least four times without the loss of catalytic activity. Furthermore, the structure and properties of Cu/ZnO/Al_2O_3 catalyst was characterized through XRD, BET, SEM, TEM and H_2-TPR. Also, the influence of different support oxides and calcination temperatures was investigated.