Highly stable and selective Ru/NiFe_2O_4 catalysts for transfer hydrogenation of biomass-derived furfural to 2-methylfuran

Spinel ferrites NiFe_2O_4 supported Ru catalysts have been prepared via a simple sol–gel route and applied for converting biomass-derived furfural to 2-methylfuran. The as-prepared catalysts were characterized by thermogravimetric analysis(TG), N_2 adsorption–desorption, X-ray diffraction(XRD), scanning electronic microscopy(SEM), and X-ray photoelectron spectroscopy(XPS). Results showed that the catalysts had well-dispersed Ru active sites and large surface area for calcination temperature ranging from 300 to 500 ℃. The conversion of biomass-derived furfural into 2-methylfuran was conducted over Ru/NiFe_2O_4 through catalytic transfer hydrogenation in liquid-phase with 2-propanol as the hydrogen source. A significantly enhanced activity and increased 2-methylfuran yield have been achieved in this study. Under mild conditions(180 ℃ and 2.1 MPa N_2), the conversion of furfural exceeds 97% and 2-methylfuran yield was up to 83% over the catalyst containing 8 wt% Ru. After five repeated uses, the catalytic activity and the corresponding product yield remained almost unchanged. The excellent catalytic activity and recycling performance provide a broad prospects for various practical applications.     

Stannous oxalate as a novel catalyst for the synthesis of polytrimethylene terephthalate

Stannous oxalate was prepared efficiently and characterized by XRD and FT-IR. It exhibited higher catalytic activity and had profitable effect than tetrabutyl titanate and stannous octoate for the synthesis of polytrimethylene terephthalate (PTT) via esterification-route. Over this catalyst, the degree of esterification of pure terephthalic acid was up to 94.4% at 260°C after 1.5 h, while the intrinsic viscosity and content of terminal carboxyl groups of the corresponding PTT polyester, polymerized at 260°C, 60 Pa for 2 h, was 0.8950 dL/g and 15 mol/t, respectively. Stannous oxalate was a promising catalyst for the synthesis of PTT polyester.     

Reaction of nitrous oxide with methane to synthesis gas: A thermodynamic and catalytic study

The aim of the present study is to explore the coherence of thermodynamic equilibrium predictions with the actual catalytic reaction of CH4 with N_2O,particularly at higher CH4 conversions.For this purpose,key process variables,such as temperature(300℃-550℃) and a molar feed ratio(N_2O/CH4 = 1,3,and 5),were altered to establish the conditions for maximized H_2 yield.The experimental study was conducted over the Co-ZSM-5 catalyst in a fixed bed tubular reactor and then compared with the thermodynamic equilibrium compositions,where the equilibrium composition was calculated via total Gibbs free energy minimization method.The results suggest that molar feed ratio plays an important role in the overall reaction products distribution.Generally for N_2O conversions,and irrespective of N_2O/CH_4 feed ratio,the thermodynamic predictions coincide with experimental data obtained at approximately 475℃-550℃,indicating that the reactions are kinetically limited at lower range of temperatures.For example,theoretical calculations show that the H2 yield is zero in presence of excess N2O(N_2O/CH_4 = 5).However over a Co-ZSM-5 catalyst,and with a same molar feed ratio(N_2O/CH_4) of 5,the H_2 yield is initially 10%at 425℃,while above450℃ it drops to zero.Furthermore,H_2 yield steadily increases with temperature and with the level of CH4 conversion for reactions limited by N_2O concentration in a reactant feed.The maximum attainable(from thermodynamic calculations and at a feed ratio of N_2O/CH4=3) H_2 yield at 550℃ is 38%,whereas at same temperature and over Co-ZSM-5,the experimentally observed yield is about 19%.Carbon deposition on Co-ZSM-5 at lower temperatures and CH4 conversion(less than 50%) was also observed.At higher temperatures and levels of CH_4 conversion(above 90%),the deposited carbon is suggested to react with N_2O to form CO_2.     

Effects of calcination and activation temperature on dry reforming catalysts

The effect of calcination temperatures on dry reforming catalysts supported on high surface area alumina Ni/γ-Al₂O₃ (SA-6175) was studied experimentally. In this study, the prepared catalyst was tested in a micro tubular reactor using temperature ranges of 500, 600, 700 and 800 °C at atmospheric pressure, using a total flow rate of 33 ml/min consisting of 3 ml/min of N₂, 15 ml/min of CO₂ and 15 ml/min of CH₄. The calcination was carried out in the range of 500–900 °C. The catalyst is activated inside the reactor at 500–800 °C using hydrogen gas. It was observed that calcination enhances catalyst activity which increases as calcination and reaction temperatures were increased. The highest conversion was obtained at 800 °C reaction temperature by using catalyst calcined at 900 °C and activation at 700 °C. The catalyst characterization conducted supported the observed experimental results.     

Ni–Al hydrotalcite-like material as the catalyst precursors for the dry reforming of methane at low temperature

Nickel–aluminium and magnesium–aluminium hydrotalcites were prepared by co-precipitation and subsequently submitted to calcination. The mixed oxides obtained from the thermal decomposition of the synthesized materials were characterized by XRD, H₂-TPR, N₂ sorption and elemental analysis and subsequently tested in the reaction of methane dry reforming (DRM) in the presence of excess of methane (CH₄/CO₂/Ar = 2/1/7). DMR in the presence of the nickel-containing hydrotalcite-derived material showed CH₄ and CO₂ conversions of ca. 50% at 550 °C. The high values of the H₂/CO molar ratio indicate that at 550 °C methane decomposition was strongly influencing the DRM process. The sample reduced at 900 °C showed better catalytic performance than the sample activated at 550 °C. The catalytic performance in isothermal conditions from 550 °C to 750 °C was also determined.     

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.     

Annealing temperature dependent catalytic water oxidation activity of iron oxyhydroxide thin films

Nanostructured iron oxyhydroxide(Fe OOH) thin films have been synthesized using an electrodeposition method on a nickel foam(NF) substrate and effect of air annealing temperature on the catalytic performance is studied. The as-deposited and annealed thin films were characterized by X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS), field emission scanning electron microscopy(FE-SEM) and linear sweep voltammetry(LSV) to determine their structural, morphological, compositional and electrochemical properties, respectively. The as-deposited nanostructured amorphous Fe OOH thin film is converted into a polycrystalline Fe_2O_3 with hematite crystal structure at a high temperature. The Fe OOH thin film acts as an efficient electrocatalyst for the oxygen evolution reaction(OER) in an alkaline 1 M KOH electrolyte. The film annealed at 200 °C shows high catalytic activity with an onset overpotential of 240 m V with a smaller Tafel slope of 48 m V/dec. Additionally, it needs an overpotential of 290 mV to the drive the current density of 10 m A/cm~2 and shows good stability in the 1 M KOH electrolyte solution.     

Sulfonate group modified Ni catalyst for highly efficient liquid-phase selective hydrogenation of bio-derived furfural

A simple and highly efficient Ni catalyst was synthesized and showed excellent catalytic performance for selectively liquid-phase hydrogenation of furfural to furfuryl alcohol or tetrahydrofurfuryl alcohol.     

Stannous-acetylacetonate： A new catalyst for poly（trimethylene terephthalate） synthesis

Stannous-acetylacetonate was prepared efficiently and characterized by 1H NMR and FT-IR. Its catalytic activity for poly(trimethylene terephthalate) (PTT) synthesis was investigated. By this catalyst, the degree of esterification of pure terephthalic acid was up to 91.7% after reaction at 260°C for 2 h, while the intrinsic viscosity and content of ter- minal carboxyl groups of the corresponding PTT polymerized at 260°C, 60 Pa for 2 h was 0.8816 dL/g and 17 mol/t, respectively. Stannous-acetylacetonate was more active and promising than tetrabutyl titanate and stannous octoate for PTT synthesis.     

Ultrathin free-standing electrospun carbon nanofibers web as the electrode of the vanadium flow batteries

Ultrathin free-standing electrospun carbon nanofiber web(ECNFW) used for the electrodes of the vanadium flow battery(VFB) has been fabricated by the electrospinning technique followed by the carbonization process in this study to reduce the ohmic polarization of the VFB. The microstructure, surface chemistry and electrochemical performance of ECNFW carbonized at various temperatures from 800 to 1400 °C have been investigated. The results show that ECNFW carbonized at 1100 °C exhibits the highest electrocatalytic activity toward the V~(2+)/V~(3+)redox reaction, and its electrocatalytic activity decreases along with the increase of carbonization temperature due to the drooping of the surface functional groups.While for the VO~(2+)/VO_2~+redox couple, the electrocatalytic activity of ECNFW carbonized above 1100 °C barely changes as the carbonization temperature rises. It indicates that the surface functional groups could function as the reaction sites for the V~(2+)/V~(3+)redox couple, but have not any catalytic effect for the VO~(2+)/VO_2~+redox couple. And the single cell test result suggests that ECNFW carbonized at 1100 °C is a promising material as the VFB electrode and the VFB with ECNFW electrodes obtains a super low internal resistance of 250 mΩ cm~2.     

Enhanced effect of plasma on catalytic reduction of CO_2 to CO with hydrogen over Au/CeO_2 at low temperature

In terms of the reaction of CO_2 reduction to CO with hydrogen, CO_2 conversion is very low at low temperature due to the limitation of thermodynamic equilibrium(TE). To overcome this limitation, plasma catalytic reduction of CO_2 to CO in a catalyst-filled dielectric barrier discharge(DBD) reactor is studied. An enhanced effect of plasma on the reaction over Au/CeO_2 catalysts is observed. For both the conventionally catalytic(CC) and plasma catalytic(PC, Pin= 15 W) reactions under conditions of 400 °C, H_2/CO_2= 1,200 SCCM, GHSV = 12,000 mL·g~(-1)cat·h~(-1), CO_2 conversions over Au/CeO_2 reach 15.4% and 25.5% due to the presence of Au, respectively, however, those over CeO_2 are extremely low and negligible. Moreover,CO_2 conversion over Au/CeO_2 in the PC reaction exceeds 22.4% of the TE conversion. Surface intermediate species formed on the catalyst samples during the reactions are determined by in-situ temperatureprogrammed decomposition(TPD) technique. Interestingly, it disclosed that in the PC reaction, the formation of formate intermediate is enhanced by plasma, and the acceleration by plasma in the decomposition of formate species is much greater than that in the formation of formate species on Au/CeO_2. Enhancement factor is introduced to quantify the enhanced effect of plasma. Lower reactor temperature, higher gas hourly space velocity(GHSV), and lower molar ratio of H_2/CO_2 would be associated with larger enhancement factor.     

A non-precious metal catalyst for oxygen reduction prepared by heat-treating a mechanical mixture of carbon black,melamine and cobalt chloride

A non-precious metal catalyst CoMe]C for the oxygen reduction reaction is prepared by heat-treating a mechanical mixture of carbon black, melamine and cobalt chloride at 600 under nitrogen atmosphere for 2 h. The catalytic activity of CoMe/C is characterized by the electrochemical linear sweep voltammetry technique. The onset reduction potential of the catalyst is 0.55 V （vs. SCE） at a scanning rate of 5 mV/s in 0.5 mol/L H2SO4 solution. The formation of the ORR activity sites of CoMe/C is facilitated by metallic β- cobalt.     

Syngas production from ethanol dry reforming over Rh/CeO2 catalyst

Carbon dioxide reforming of ethanol over Rh/CeO₂ catalyst was deeply investigated at different reaction temperatures of 450–700 °C and reactant ratios (CO₂/ethanol from 1 to 3) under atmospheric pressure. The obtained results indicated that Rh/CeO₂ catalyst presented a promising activity and stability for syngas production from renewable bio-ethanol instead of conventional methane. Typically, CO₂-rich conditions (CO₂/ethanol = 3) were favorable for reaction process and dynamic coke cleaning, which led to remarkably stable performance over 65 h on stream. The strong redox capacity of CeO₂ support might also accelerate CO₂ activation and prevent the carbon accumulation over the catalyst surface. Additionally, tunable H₂/CO ratios were available by changing the CO₂/ethanol ratios. The results from characterization of samples before and after catalytic tests allowed to establish the relationship between textural properties and catalytic performance.     

Comparison of catalytic pyrolysis of biomass with MCM-41 and CaO catalysts by using TGA–FTIR analysis

Pyrolysis of corncob with and without catalyst was investigated using thermogravimetry analyzer coupled with Fourier transform infrared spectroscopy (TGA–FTIR). The effects of two completely different catalysts, acid catalyst (MCM-41) and base catalyst (CaO), on the formation characteristics and composition of pyrolysis vapor were studied. The results show that these two catalysts give different product distributions. For catalytic run with MCM-41, the molality of carbonyl compounds decreases 10.2%, while that of phenols, hydrocarbons and CH₄ increases 15.32%, 4.29% and 10.16% compared with non-catalytic run, respectively. The increase of phenols exhibits in a wide temperature range from about 295 °C to 790 °C in the catalytic run with MCM-41 catalyst. However, the use of CaO in pyrolysis of corncob leads to a huge change of product distribution. The molality of acids decreases 75.88%, while the molality of hydrocarbons and CH₄ increases 19.83% and 51.05% compared with non-catalytic run, respectively. CaO is very effective in deacidification and the conversion of acids promotes the formation of hydrocarbons and CH₄. Catalytic pyrolysis of corncob with CaO shows two main weight-loss stages. The first stage is from 235 °C to 310 °C with a weight loss of 31%. The second stage is from 650 °C to 800 °C with a weight loss of 21%.     

Fabrication of a nano-sized ZSM-5 zeolite with intercrystalline mesopores for conversion of methanol to gasoline

Carbon deposition during methanol to hydrocarbons leads to the quick deactivation of ZSM-5 catalyst and it is one of the major problems for this technology. Decreasing the crystal size or introducing mesopores into ZSM-5 zeolites can improve its diffusion property and decrease the coke formation. In this paper, nano-sized ZSM-5 zeolite with intercrystalline mesopores combining the mesoporous and nanosized structure was fabricated. For comparison, the mesoporous ZSM-5 and nano-sized ZSM-5 were also prepared. These catalyst samples were characterized by XRD, BET, NH3-TPD, TEM, Py-IR and TG techniques and used on the conversion of methanol to gasoline in a fixed-bed reactor at T = 405 °C, WHSV = 4.74 h-1and P = 1.0 MPa. It was found that the external surface area of the nano-sized ZSM-5 zeolite with intercrystalline mesopores reached 104 m2/g, larger than that of mesoporous ZSM-5(66 m2/g) and nanosized ZSM-5(76 m2/g). Catalytic lifetime of the nano-sized ZSM-5 zeolite with intercrystalline mesopores was 93 h, which was only longer than that of mesoporous ZSM-5(86 h), but shorter than that of nanosized ZSM-5(104 h). Strong acidity promoted the coke formation and thus decreased the catalytic lifetime of the nano-sized ZSM-5 zeolite with intercrystalline mesopores though it presented large external surface that could improve the diffusion property. The special zeolite catalyst was further dealuminated to decrease the strong acidity. After this, its coke formation rate was slowed and catalytic lifetime was prolonged to 106 h because of the large external surface area and decreased weak acidity. This special structural zeolite is a potential catalyst for methanol to gasoline reaction.     

Ternary non-noble metal chalcogenide (W–Co–Se) as electrocatalyst for oxygen reduction reaction

In this study, a catalyst based on a novel ternary non-noble metal chalcogenide, W–Co–Se, was synthesized for the oxygen reduction reaction (ORR) in acidic medium. The non-noble metal chalcogenide catalyst was electrochemically stable in the potential range of 0.05–0.8 V versus NHE in 0.5 M H₂SO₄ aqueous solution. This catalyst demonstrated significant catalytic activity towards the ORR, showing the ORR onset potential at 0.755 V versus NHE in 0.5 M H₂SO₄ at 25 °C. Such high activity might be attributed to the electronic structure of non-noble metals modified by chalcogen.     

Environment friendly hydrothermal synthesis of carbon–Co_3O_4 nanorods composite as an efficient catalyst for oxygen evolution reaction

The design of cost-effective, highly active catalysts for hydrogen energy production is a vital element in the societal pursuit of sustainable energy. Water electrolysis is one of the most convenient processes to produce high purity hydrogen. Cobalt-based catalysts are well-known electrocatalysts for oxygen evolution reaction(OER). In this article, all these merits indicate that the present cobalt nanocomposite is a promising electrocatalyst for OER. C–Co_3O_4-nanorods catalyst with nanorod structure was synthesized by hydrothermal treatment of CoCl_2·6H_2O/dextrose/urea mixture at 180 °C for 18 h and then calcined at400 °C for 3.5 h. The role of dextrose percentage in solution to achieve the uniform coating of carbon on the surface of Co_3O_4-nanorods has been demonstrated. The prepared materials were characterized by X-ray diffraction(XRD), X-ray photoelectron spectrum(XPS), field emission scanning electron microscopy(FE-SEM), high-resolution transmission electron microscopy(HR-TEM), and Brunauer–Emmett–Teller instrument(BET). Due to its unique morphology, the C–Co_3O_4-nanorods catalyst exhibited better activity than Co_3O_4-microplates catalyst for OER in 1 M KOH aqueous solution. The results showed a highly efficient, scalable, and low-cost method for developing highly active and stable OER electrocatalysts in alkaline solution.     

Syngas Production from Lignite Coal Using K2CO3 Catalytic Steam Gasification with Controlled Heating Rate in Pyrolysis Step

Gasification uses steam increases H2 content in the syngas. Kinetics of gasification process can be improved by using K₂CO₃ catalyst. Controlled heating rate in pyrolysis step determines the pore size of charcoal that affects yield gas and H₂ and CO content in the syngas. In previous research, pyrolisis step was performed without considering heating rate in pyrolysis step. This experiment was performed by catalytic steam gasification using lignite char from pyrolysis with controlled heating rate intended to produce maximum yield of syngas with mole ratio of H₂/CO ≈ 2. Slow heating rate (3 °C/min) until 850 °C in the pyrolysis step has resulted in largest surface area of char. This study was performed by feeding Indonesian lignite char particles and K₂CO₃ catalyst into a fixed bed reactor with variation of steam/char mole ratio (2.2; 2.9; 4.0) and gasification temperature (750 °C, 825 °C, and 900 °C). Highest ratio of H₂/CO (1.682) was obtained at 750 °C and steam/char ratio 2.2. Largest gas yield obtained from this study was 0.504 mol/g of char at 900 °C and steam/char ratio 2.9. Optimum condition for syngas production was at 750 °C and steam/char mole ratio 2.2 with gas yield 0.353 mol/g of char and H₂/CO ratio 1.682.     

Cu2O-catalyzed Ullmann-type reaction of vinyl bromides with imidazole and benzimidazole

Cu₂O was found to be an efficient and economical metal catalyst in the Ullmann cross-coupling reaction of vinyl bromides with imidazole or benzimidazole. The system Cu₂O/ethyl 2-oxocyclohexanecarboxylate showed high catalytic activity in MeCN at 80–90 °C. The reaction gave the corresponding coupling products in good to excellent yields.     

Expedient one-pot organometallics-free synthesis of tris(2-pyridyl)phosphine from 2-bromopyridine and elemental phosphorus

2-Bromopyridine reacts with elemental phosphorus (red or white) in a superbasic KOH/DMSO(H₂O) suspension at 100 °C (for red phosphorus) and 75 °C (for white phosphorus) over 3 h to afford tris(2-pyridyl)phosphine in a 62% yield (from red phosphorus) and a 50% yield (from white phosphorus). Under microwave assistance, the reaction with red phosphorus takes just 20 min to produce tris(2-pyridyl)phosphine in 53% yield. A hitherto unknown complex, [Pd(PPy₃)₂Cl₂]·CH₂Cl₂, synthesized from tris(2-pyridyl)phosphine and PdCl₂, has the cis-configuration; this is unusual for bis(phosphino)palladium dichloride complexes.