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1.
Methanol: A “Smart” Chemical Probe Molecule 总被引:1,自引:0,他引:1
A novel chemisorption method was employed for the dissociative adsorption of methanol to surface methoxy intermediates in order to quantitatively determine the number of surface active sites on one-component metal oxide catalysts (MgO, CaO, SrO, BaO, Y2O3, La2O3, CeO2, TiO2, ZrO2, HfO2, V2O5, Nb2O5, Ta2O5, Cr2O3, MoO3, WO3, Mn2O3, Fe2O3, Co3O4, Rh2O3, NiO, PdO, PtO, CuO, Ag2O, Au2O3, ZnO, Al2O3, Ga2O3, In2O3, SiO2, GeO2, SnO2, P2O5, Sb2O3, Bi2O3, SeO2 and TeO2). The number of surface active sites for methanol dissociative adsorption corresponds to 3 mol/m2 on average for many of the metal oxide catalysts. Furthermore, the methanol oxidation product distribution at low conversions reflects the nature of the surface active sites on metal oxides since redox sites yield H2CO, acidic sites yield CH3OCH3 and basic sites yield CO2. The distribution of the different types of surface active sites was found to vary widely for the different metal oxide catalysts. In addition, the commonality of the surface methoxy intermediate during dissociative chemisorption of methanol and methanol oxidation on oxide catalysts also allows for the quantitative determination of the turnover frequency (TOF) values. The TOF values for the various metal oxide catalysts were found to vary over seven orders of magnitude (10–3 to 104 s–1). An inverse relationship (for metal oxide catalysts displaying high (>85%) selectivity to either redox or acidic products) was found between the methanol oxidation TOF values and the decomposition temperatures of the surface M–OCH3 intermediates reflecting that the decomposition of the surface M–OCH3 species is the rate-determining step during methanol oxidation over the metal oxide catalysts. 相似文献
2.
Amorphous Cr2O3, SnO2 and SrO presented an excellent performance in the conversion of glucose to 5-hydroxymethylfurfural (5-HMF), and 5-HMF yields achieved 84%, 81% and 99%, however, the calcined metal oxides almost completely lost the catalytic activities. Although Fe2O3 exhibited very poor catalytic activity, the graphene oxide–Fe2O3 (GO–Fe2O3) displayed a better performance in catalytic glucose conversion to 5-HMF (86% yield) in 1-ethyl-3-methylimidazolium bromide ([EMIM]Br). The plausible mechanisms of glucose conversion to 5-HMF over amorphous Cr2O3, SnO2, SrO and GO–Fe2O3 were proposed. 相似文献
3.
《Journal of Adhesion Science and Technology》2013,27(8):1137-1147
We have measured the adhesion strengths of metal oxide and metal nitride thin films reactively sputtered onto glass substrates using a specially devised direct pull-off test. For double-layer coatings such as metal nitride (CrNx, TiNx)/metal oxide (Al2O3, SnO2, Ta2O5, TiO2, ZnO, ZrO2)/glass, separation usually took place at the nitride/oxide interface. The adhesion strength at the interface was found to depend on the strength of chemical bonding in the films concerned: for the same nitride top layer, the adhesion strength increased as the strength of the metal-oxygen (M-O) bond in the oxide underlayer decreased. X-ray photoelectron spectroscopy (XPS) measurements showed that a mixed layer was created at the nitride/oxide interface and that the adhesion strength at the interface increased with increasing thickness of the mixed layer. For single-layer coatings such as metal nitride (CrNx, TaNx, TiNx, ZrNx)/glass, the adhesion strength of the film to the glass substrate was found to increase with increasing strength of the M-O bond between the metal atom (M) in the nitride film and an oxygen atom (O). These adhesion behaviors could be explained by adhesion models based on chemical bonds at the interfaces. 相似文献
4.
S. M. Rabie S. A. Moharram A. Y. Daghistani M. A. Moharram 《Polymer-Plastics Technology and Engineering》2013,52(5):397-414
The electrical conductivity of polyacrylamide (PAAm) before and after treatment with low concentrations of ZnCl2, NiCl2, and CoCl2 was determined at different temperatures. The effects of γ-irradiation on the electrical conductivity and activation energy of the original and the metal-chloride-treated specimens were investigated. The experimentally obtained data revealed that the conduction in PAAm is ionic in nature. The treatment of the polymer with 2% or 4% (w/w) of ZnCl2, NiCl2, or CoCl2, as determined from its weight, either increases or decreases its conductivity according to the nature of the metal ions, concentration of metal chloride, ratio of KOH/metal chloride, and temperature and cycle of measurement. The exposure of PAAm to 2 to 10 Mrad of γ-radiation produces no significant changes in its conductivity. On the other hand, the exposure of the PAAm pretreated with a metal chloride produces considerable changes in its conductivity. Also, the γ-irradiation of PAAm increases its activation energy. The extent of the γ-induced changes in activation energy was influenced by the pretreatment of PAAm with metal chlorides. 相似文献
5.
《Catalysis communications》2009,10(15):2560-2564
Single-step catalytic synthesis of diphenyl carbonate (DPC) through the transesterification of dimethyl carbonate (DMC) and phenol could be firstly arrived by using the transition-metal-substituted polyoxometalates (TMS-POMs) K5[PW11O39M(H2O)]/TiO2 system (M = MnII, CoII, NiII, CuII, ZnII). The catalytic activity of this transesterification was strongly influenced by the type of transition metal in the TMS-POMs. Among them, the K5[PW11O39Zn(H2O)]/TiO2 catalytic system showed the highest activity and selectivity for DPC. The conversion of phenol reached 12.8%, and the selectivity to DPC was 83.6%. The turnover number (TON) reached 6.44 × 104 mol/mol [PW11O39Zn(H2O)]5−/TiO2. A possible mechanism that the transition metal in the polyoxometalates anchored DMC to form intermediate compound in the transesterification was proposed. 相似文献
6.
A novel chemical conversion coating was prepared by adding tannic acid and coating-forming accelerator in the treatment solution containing titanium and zirconium ions. Corrosion behavior of the coatings in contact with 3.5% NaCl solution was investigated using potentiodynamic measurement. The structure and composition of the coatings were determined with EDS, XPS and IR. The morphologies of the coatings were observed with scanning electron microscopy (SEM). According to the results, the modified Ti–Zr based conversion coating (MTZ) shows a smoother and more compact morphology characterization comparing with the traditional Ti–Zr treated (TZ) substrates; The Tafel results and the long-time immersion experiments also indicate that the MTZ coating presents a more effective corrosion protection property compared with the TZ coating; The MTZ coating is a multi-components chemical conversion coating which is mainly composed of metal oxide (TiO2, ZrO2, V2O5, Al2O3), fluoride (AlF3 and ZrF4) and metal–organic complex. 相似文献
7.
The study was conducted on the effects of Cr2O3, Fe2O3, Cu(OH)2, ZnO and Pb2O(OH)2 on the formation of ettringite and microstructure of hardened ettringite. The cement samples were prepared by mixing C3A synthesized and CaSO4·2H2O and adding 5 % by weight of above additives. The heavy metal oxides and hydroxides promote the crystal growth of ettringite and produce some changes in microstructure and Cr2O3 and Cu(OH)2 exert a considerable influence. 相似文献
8.
Transition metal/Y zeolites have been prepared by solid state ion exchange with microwave irradiation of mechanical mixtures of VCl3, CrCl3 ⋅ 6H2O, MnCl2 ⋅ 4H2O or CoCl2 ⋅ 6H2O with NaY zeolite at 900 W in 10–20 min. The prepared transition metal/Y zeolites were characterized by X-ray diffraction (XRD), infrared spectroscopy (IR), simultaneous thermal analysis (STA) and surface area measurement (BET). Concentration of dispersed transition metal on zeolite was measured and results revealed that transition metal was dispersed and ion exchanged onto the surface of NaY zeolite. 相似文献
9.
Wei Li Mercedes Coughlin Robert L. Albright Richard H. Fish 《Reactive and Functional Polymers》1995,28(1)
We report on the synthesis and reactivity of a polymer-supported o-phenylenediamine hydrochloride ligand, PS-PDHC, using macroporous 6% crosslinked polystyrene-divinylbenzene beads. The PS-PDHC ligand was found to be highly selective to AuCl4− ions in strongly acidic solutions in the presence of other precious metal ions, PdCl42−, PtCl42−, RhCl63−, and RuCl52− (selectivity values: 2.5, Au/Pd; 7.5, Au/Pt; 7, Au/Rh; 2.2, Au/Ru) as well as other transition metal ions, Fe 3+, Cr3+, CU2+, Nit+, and Mn2+. The sorption capacity, selectivity, kinetics of removal and recovery, and solution isotherms have been determined for AuCl4− ions in competition with the above-mentioned metal ions. The relative ease of formation of the anionic complex in 0.5 M HCI, AuCl4− was thought to be the primary reason for its selective ability to bind to the PS-PDHC ligand by an anion-exchange mechanism. Therefore, the effect of the HCI concentration on the kinetics of AuCl4− ion removal from solution was also investigated to clearly show that raising the pH from 0 to 5 caused a dramatic decrease in rate. The AuCl4− ion can be recovered quantitatively from the PS-PDHC beads using a 5% thiourea solution in 0.1 M HCl, allowing the polymer-supported ligand to be reused. 相似文献
10.
In this study, acrylic-based nanocomposites containing different contents of multi-walled carbon nanotubes (MWCNTs) and metal oxide nanoparticles (i.e., TiO2, CuO and Fe2O3) were fabricated by solvent mixing method. The thermal conductivity of these samples was evaluated. The results indicated that the thermal conductivity of all fabricated samples was significantly improved even at small loading of MWCNTs. It was found that the thermal conductivity was enhanced by increase in MWCNTs content up to 5 wt%. Similarly, the metal oxide nanoparticles caused up to 75 % increment in thermal conductivity at 1.5 wt% of their loading in acrylic film. Contrary to expectations, the thermal conductivity of acrylic film was more increased by nanometal oxides (i.e., TiO2, CuO and Fe2O3) than MWCNTs. The effect of hybridizing of nanometal oxide particles (1.5 wt%) and MWCNTs (1.5 wt%) on thermal conduction was investigated as well. It was found that hybridizing improved thermal conductivities by about 85, 94 and 97 % for Fe2O3, TiO2 and CuO, respectively. Finally, the effects of TiO2 pigment and CaCO3 extender on the thermal conductivity of acrylic polymer and nano-TiO2 acrylic composites were studied. It was found that TiO2 could increase considerably thermal conduction of its acrylic films and acrylic nanocomposites. 相似文献
11.
Summary
The vinyl polymerization of norbornene with di-μ-chloro-bis-(6-methoxybicyclo-[2.2.1]hept-2-ene-5σ,2π)-palladium(II), Ni(acetylacetonate)2 and Ni(2-ethylhexanoate)2 in combination with methylalumoxane (MAO) was investigated by varying the molar MAO:metal-complex ratio, the norbornene:metal
ratio and the metal concentration. The effects on the catalyst activity could be explained with a complexation equilibrium
for the active homogeneous complex. Activity data in combination with polymer analyses suggest that at low, yet economical
Al(MAO):metal ratios of 100 the fraction of active metal centers is less than 15%. The turnover frequency for the monomer
insertion was found to reach 50 s−1. Polydispersities around Mw/Mn= 2 indicate a coordination polymerization with chain transfer and a single-site character of the active centers.
Received:27 February 2001/Revised version:11 November 2001/ Accepted: 20 November 2001 相似文献
12.
Alumina supported phosphovanodomolybdic acid and alumina supported phosphovanodomolybdic acid‐transition metal ions (M: Fe3+, Co2+, or Ni2+) were prepared by impregnation. The thermal decomposition, in situ at 400°C, of supported catalysts showed the formation of V2O5, P2O5, MoO3 and MoO3, CoMoO4, (Mo0.3V0.7)2O5 phases, on the alumina surface, in the presence of H4PMo11VO40/α‐Al2O3 and H4PMo11VO40? Co/α‐Al2O3, respectively. The catalytic activity of alumina‐supported catalysts was evaluated in the reaction of propane oxidation at 380 and 400°C. The addition of transition metal increases the conversion and changes the reaction products distribution. The reaction conditions (temperature and propane/oxygen ratio) have also modified the behaviour of the studied catalysts. 相似文献
13.
Kyung-Ho Park Debasish Mohapatra Chul-Woo Nam Hong-In Kim 《Korean Journal of Chemical Engineering》2007,24(5):835-842
The extraction behaviors of Cu, Ni and Co from a complex matte under different leaching conditions have been discussed. The
synthetic Cu-Ni-Co-Fe-S matte was prepared by melting the pure metals. The matte contained 24.95% Cu, 35.05% Ni, 4.05% Co,
11.45% Fe, 24.5% S, similar composition as is expected to be obtained by reduction smelting of the Pacific Ocean nodules followed
by sulphidisation of the alloy. The different phases identified are CuFeS2, CuS2, (FeNi)9S8, (FeNi)S2, Ni9S8, Ni3S2, (CoFeNi)9S8 and Co metal. The merits and demerits of each process of dissolution i.e., H2SO4/oxygen pressure leaching, atmospheric FeCl3 leaching, NH4OH/(NH4)2SO4 pressure leaching are discussed in detail. Out of the three, the H2SO4/oxygen pressure leaching process is found to be the most suitable with more than 99% metal extraction efficiency within 1
h of leaching time. From the X-ray diffraction analysis, the different undissolved phases corresponding to different leaching
processes have been identified. The metal extraction efficiency decreased in case of atmospheric FeCl3 leaching and NH4OH/(NH4)2SO4 pressure leaching processes due to the formation of product layer such as elemental sulfur and goethite, respectively. 相似文献
14.
S. H. Chien C. B. Christianson M. S. Lupin G. E. Peters 《Nutrient Cycling in Agroecosystems》1987,14(2):181-191
It has been the experience of the fertilizer industry that urea should not be cogranulated or blended with superphosphate because urea reacts with monocalcium phosphate monohydrate (MCP·H2O) in superphosphate to form an adduct. This reaction releases the water of hydration and causes the product to become wet and sticky or severely caked during storage. The objectives of this study were [1] to test the feasibility of preventing or retarding the reaction by complexing the urea with various salt hydrates and [2] to measure ammonia volatilization from metal salt-urea complexes on the soil surface.Three metal salt-urea complexes — Al(urea)6(NO3)3, Fe(urea)6(NO3)3, and Mn(urea)4Cl2 — were prepared and cogranulated by compaction with pure MCP·H2O or triple superphosphate (TSP) at a mole ratio of MCP:urea as 1:2. These materials were then compared with the same material without metal salts in terms of changes in free water content during a storage period of 6 weeks. Without metal salts a rapid and significant increase in free water content of the cogranulated MCP·H2O + urea or TSP + urea was observed. The increases in free water content were found to range from 1.5% to 1.8%, corresponding to approximately 63% and 78% of the added MCP·H2O that reacted with urea in the cogranulated products. On the other hand, little change or only a slight increase (less than 0.5%) in free water content was observed with the cogranulated metal salt-urea complexes.Ammonia volatilization losses from urea on the soil surface were measured in a period up to 14 d with two soils: Windthorst (pH 7.6) and Savannah (pH 7.0). The fertilizer materials used were granular. In Windthorst soil, the amounts of NH3-N lost were 25% for prilled urea, 11% for Mn(urea)4Cl2, and essentially none for Mn(urea)4Cl2 compacted with TSP at a mole ratio of MCP:urea as 1:1 or 1:2. In Savannah soil, the amounts of NH3-N lost were 39% for prilled urea, 24% for Mn(urea)4Cl2, 15% for Fe(urea)6(NO3)3, and less than 6% for each of the two metal salt-urea complexes compacted with TSP. The acidity that resulted from metal complexing of urea reduced NH3 volatilization from hydrolyzed urea in soils, and additional acidity produced from hydrolysis of MCP·H2O further reduced NH3 losses when materials were applied as multicomponent granules (metal salt + urea + TSP). 相似文献
15.
İsmet Kaya Bayram Kιzιlkaya Eyüp Özdemir 《Polymer-Plastics Technology and Engineering》2013,52(7):1307-1322
The oxidative polycondensation reaction conditions of 2-[(4-chlorophenyl) imino methylene] phenol (CPIMP) were studied by air O2 and NaOCl oxidants at various temperatures and times. Optimum reaction conditions of air O2 and NaOCl were determined for CPIMP. Oligo-2-[(4-chlorophenyl) imino methylene] phenol (OCPIMP) was synthesized from the oxidative polycondensation of CPIMP with air O2 and NaOCl in alkaline medium between 50 and 90°C. The number-average molecular weight (Mn) weight-average molecular weight (Mw) and polydispersity index (PDI) values of OCPIMP were found to be 470 g mol?1, 895 g mol?1, and 1.90, using NaOCl, and 455 g mol?1, 765 g mol?1, and 1.68, using air O2, respectively. At the optimum reaction conditions, the yield of OCPIMP was found to be 62.80% (for air O2 oxidant) and 87.50% (for NaOCl oxidant). The OCPIMP was characterized by 1H-NMR, FT-IR, UV-Vis and elemental analysis. The thermogravimetric (TGA)-DTA analyses were shown to be stable of OCPIMP and its oligomer metal complexes (such as Co+2, Ni+2, and Cu+2) against thermo-oxidative decomposition. The weight loss of OCPIMP and its oligomer metal complexes (such as Co+2, Ni+2, and Cu+2) were found to be 98%, 85%, 80%, and 82%, respectively, at 1000°C. 相似文献
16.
Sanjay Bisht Sasikumar Balaguru Sathish Kumar Ramachandran Arthanareeswaran Gangasalam Jihyang Kweon 《应用聚合物科学杂志》2021,138(22):50530
Proton exchange membrane fuel cell (PEMFC) is a promising technology that offers a clean and efficient renewable energy source. The hybrid SiO2, sulfonated SiO2 (S SiO2), and metal–organic framework-5 (MOF-5) incorporated sulfonated poly (ether ether ketone) (SPEEK) ternary composite membranes are fabricated using dry phase inversion technique for PEMFC. The membrane performance is evaluated in terms of water uptake, ion exchange capacity, methanol permeability, and proton conductivity (PC) measurements. The morphological study of fabricated membranes was carried out using scanning electron microscopy and atomic force microscopy analysis. The mechanical stability is strengthened up to 30–40%, and the PC gets enhanced with the incorporation of MOF-5, achieving simultaneous improvement in proton conduction and membrane stability. The PC of the ternary SPEEK/S SiO2/MOF-5 membrane is 3.69 × 10−3 S cm−1, 32% more than the neat membrane. A significant increase in selectivity of 23% is observed by incorporating S SiO2 and MOF-5 fillers when compared with the neat membrane. The synergistic effect of MOF-5 and S SiO2 in the ternary membrane has significantly improved water retention and proton conductivity. The functional SO3H groups of SiO2 and MOF-5 bonded via acid–base electrostatic interactions with the SPEEK; enhances proton conduction accompanied by suppressing the methanol penetration through membranes. 相似文献
17.
Carrier-assisted transport through liquid membranes is one of the important applications of supramolecular chemistry. This work investigates the use of synthetic carrier (ionophore) for the separation of metal ions. We have tested the effect of structure of ionophore on the separation of metal ions. For this purpose, we have used a new series of non-cyclic ionophores having different end groups and chain length (R1–R5). 1,5 bis (2-naphthyloxy)-3-oxapentane (R1), 1,8 bis (2-naphthyloxy)-3,6-di-oxaoctane (R2), 1,11 bis (2-naphthyloxy)-3,6,9-tri-oxaundecane (R3) 1,11-(dianthraquinonyloxy) 3,6,9-trioxaundecane (R4), 1,8 (dianthraquinonyloxy) 3, 6-dioxaoctane (R5) have been used in extraction, bulk liquid membrane (BLM) and supported liquid membrane (SLM) transport of alkali (Li+, Na+, K+) and alkaline earth metal cations (Ca2+, Mg2+). The supported liquid membrane consisted of a porous cellulose nitrate and and an onion membrane support impregnated with ionophore using chloroform as a solvent. The results reveal that ionophores R1, R2 and R3 are better extractants for K+ while R4 and R5 are better extractants for Ca2+. Among these ionophores R3 and R4 are best extractants for K+ and Ca2+ ions. The results of BLM reveal that ionophores R1, R2 and R3 transport Na+ at a greater extent, while R4 and R5 transport Ca2+ and K+ at a greater extent. In SLM experiments using a cellulose nitrate membrane support, it was observed that naphthyl end group bearing ionophores (R1–R3) transports Na+ > K+, and anthraquinone bearing ionophores (R4 and R5) transport K+ > Na+ > Ca2+ respectively. In the onion membrane support R4 transports Ca2+ and Na+ equally and R5 transports K+ selectively. On comparing the membrane support, the cellulose nitrate membrane is found better support for the transport of metal ions. The results suggest that due to the presence of different end groups and chain lengths the selectivity of non-cyclic ionophores towards metal ions is enhanced. Thus selectivity of ionophores may have fruitful application in ion selective electrodes and separation of metal ions. 相似文献
18.
Summary The new single ion conductors, poly(oligo-oxyethylene methacrylate-co-alkali metal acrylamidocaproic acid) ((CH2CCH3COO(CH2CH2O)9H)x–(CH2CHCONH(CH2)5 COO-M+)1-x), M+=Li+, Na+, K+, were synthesized and the effects of the cation and the temperature on ionic conductivity were investigated. The alkyl spacer in the alkali metal acrylamidocaproate was introduced to increase the flexibility of the side chain for the complex formation between the ionic groups and the oxygens in PEO unit. The room temperature(30°C) conductivity of the K single ion conductor was found to be 5x10-7 S/cm which is the highest value reported for the single ion conductors having carboxylate groups without any additives. The pseudo-activation energy in the VTF equation was not dependent on the type of the cation, which indicates that the ion hopping rate is higher than the string renewal rate in these single ion conductors. 相似文献
19.
The most mature and practical technology to reduce industrial CO2 emissions, the main contributor to global warming, is amine-based post-combustion CO2 capture. However, this results in amine degradation products that pose a threat to human health as well as marine life. To reduce the impact on human health and marine life, identifying and treating carcinogenic and mutagenic compounds like N-nitrosamines is extremely important. Photocatalysis, in particular, an advanced oxidation process which uses a UV light source and semiconductor catalysts is studied for the degradation of organic and inorganic pollutants. N-Nitrosodiethylamine (NDEA) is treated with strong reactive hydroxyl radicals generated by a bismuth tungstate (Bi2WO6) semiconductor under UV/visible irradiation. The Bi2WO6 was studied both in pure form and surface-modified forms using transition metal impregnation like Ag, Fe, Cu, and La. Various catalyst characterization techniques like Brunauer–Emmett–Teller (BET), X-ray diffraction analysis (XRD), UV–visible, and scanning electron microscopy–energy-dispersive X-ray (SEM-EDS) are used to study the surface textural and morphological properties of the catalyst. Furthermore, the effect of pH of the solution, catalyst dosing, and metal impregnation (%) on the photocatalytic degradation of NDEA is analyzed. The face centred-central composite design (FC-CCD) experimental design method was used through response surface methodology (RSM) and optimization studies for removal of NDEA. The quadratic model was obtained as a functional link between NDEA concentration and three operation variables for all metal impregnated Bi2WO6. The results showed that the pH of the solution was the most significant factor compared to other variables like catalyst dosing and metal impregnation. The average degradation efficiency of NDEA was 89.2% for Fe-Bi2WO6, 87.4% Ag-Bi2WO6, 86.9% for La-Bi2WO6, and 85% for Cu-Bi2WO6. 相似文献
20.
《国际聚合物材料杂志》2012,61(8):757-766
ABSTRACT Coordination polymers of a novel bis(oxine) bidentate ligand, namely 1,9-bis(8-hydroxyquinolin-5-yl)-2,5,8-trioxanonane (BHQTN) (H2L) have been prepared with the metal ions Zn+2, Cu+2, Ni+2, Co+2, and Mn+2. The novel bis(bidentate) ligand BHQTN was synthesized by condensation of 5-chloromethyl-8-hydroxyquinoline hydrochloride with diethylene glycol in the presence of a base catalyst. All of these coordination polymers and the parent ligand were characterized by elemental analyses and IR spectral studies. The diffuse reflectance spectral studies and magnetic susceptibilities of all of the coordination polymers have also been performed. Thermogravimetric parameters such as To, T10, Tmax., IPDT, and the activation energy of the thermo-degradation process were calculated. 相似文献