Sintering of Cr2O3 in H2/H2O Gas Mixtures

Sintering of Cr₂O₃ was performed at 1530°C under low pO₂ close to the Cr–Cr₂O₃ equilibrium generated by H₂/H₂O gas mixtures. Addition of 1 wt%ZrO₂ and 0·1 wt%MgO increases the density of Cr₂O₃ from 97% TD to nearly full density. Rapid densification and the higher density are attributed to the appearance of a transient CrO liquid phase as a result of the presence of ZrO₂ and MgO under the sintering conditions. A grain size reduction is also achieved owing to the presence of ZrO₂ particles and the possible formation of a MgCr₂O₄ spinel at grain boundaries. There is no connection between densification and loss of material due to evaporation. ©     

A microporous chiral metal coordination polymers: Solvothermal synthesis and structural characterization of KMn2[(L-C4H2O6)2B] · 3H2O

A microporous chiral complex KMn₂[(L-C₄H₂O₆)₂B] · 3H₂O was synthesized solvothermally in the presence of l-tartaric acid. In this framework, Mn²⁺ ions exhibit distorted octahedral coordination and the tartrate group is bonded to the B atom as a bidentate ligand via oxygen atoms of neighbouring hydroxyl groups.     

Layered manganese and copper phosphonates with metamagnetism observed in Mn(2-pmp)(H2O)2·H2O (2-pmpH2 = 2-pyridylmethylphosphonic acid)

Hydrothermal reactions of 2-pyridylmethylphosphonic acid (2-pmpH₂) and corresponding metal salts lead to two new layered compounds Mn(2-pmp)(H₂O)₂·H₂O (1) and Cu(2-pmp)(H₂O) (2). The {MnO₅N} octahedra in 1 or {CuNO₄} square pyramids in 2 are each corner-shared with the {PO₃C} tetrahedra, forming inorganic layers containing alternative 8- and 16-membered rings. The organic groups graft on the two sides of the inorganic layers. The layers are packed in different fashions, resulting in interlayer distances of 10.0876 Å in 1 and 8.548 Å in 2. Magnetic measurements reveal that dominant antiferromagnetic interactions are found between metal ions in both cases. At low temperature, compound 1 shows metamagnetism with a critical field of 35 kOe at 1.8 K, while compound 2 displays an antiferromagnetism.     

Direct H2-to-H2O2 oxidation over highly active/selective Br–F–Pd/Al2O3 catalyst in aqueous acidic medium: Influence of process conditions on the H2O2 formation

The influence of the O₂/H₂ mole ratio in the gaseous feed and also those of other reaction conditions [viz. concentration of H₃PO₄ (0–5 mol/dm³), temperature (5–50 °C), gas (H₂ and O₂) space velocity (5.8–23.4 h^?1) and reaction time (0.1–8 h)] on the H₂O₂ formation in the H₂-to-H₂O₂ oxidation over the Br(1 wt%)–F(1 wt%)–Pd(5 wt%)/Al₂O₃ catalyst in an aqueous acidic (H₃PO₄) medium have been thoroughly investigated. The effects of the O₂/H₂ ratio, reaction temperature and acid concentration on the destruction of H₂O₂ by its decomposition and/or hydrogenation reactions over the catalyst in the acidic reaction medium have also been studied. The net H₂O₂ formation (H₂O₂ yield) over the catalyst passed through a maximum with increasing the acid concentration, the temperature or the O₂/H₂ feed ratio. However, it decreased markedly with increasing the gas space velocity or the reaction period. The H₂O₂ decomposition and hydrogenation activities of the catalyst increased appreciably with increasing the reaction temperature and decreased with increasing the acid concentration. The H₂O₂ destruction during the H₂-to-H₂O₂ oxidation increased with increasing the concentration of H₂ (relative to that of O₂) due to the increased H₂O₂ hydrogenation rate over the catalyst. The net H₂O₂ formation in the H₂-to-H₂O₂ oxidation decreased sharply with increasing the initial amount of H₂O₂ present in the reaction mixture. The presence of H₂O₂ and the higher H₂/O₂ ratios have detrimental effects on the net formation of H₂O₂.     

A study on proton conduction in a layered metal–organic framework,Rb2(adp)[Zn2(ox)3]·3H2O (adp = adipic acid,ox2 − = oxalate)

We newly synthesized a metal–organic framework (MOF) Rb₂(adp)[Zn₂(ox)₃]·3H₂O (adp = adipic acid; ox^2 − = oxalate), where the rubidium ions, carboxylic acid groups, and water molecules are located in an interlayer space of a two-dimensional (2-D) oxalate-bridged network. The structure of this compound was determined using single-crystal X-ray diffraction analysis. Hydrated phases of this compound were examined using thermogravimetry and water vapor adsorption measurements. Proton conductivity in this MOF was investigated by alternating current impedance measurements. Systematic comparison with previously reported isomorphous 2-D compounds A₂(adp)[Zn₂(ox)₃]·3H₂O (A = NH₄ and K) showed that the difference in the ionic radii of the cations leads to a difference in activation energy of proton conductivity and that absence of NH₄⁺ ions causes a significant decrease in proton conductivity, even though the ionic radius of Rb⁺ (1.52 Å) is closer to that of NH₄⁺ (1.61 Å) than that of K⁺ (1.38 Å).     

A novel paradodecatungstate-B compound decorated by transition metal copper,Na2Cu5(H2O)24(OH)2[H2W12O42]·10H2O: Synthesis,structure and antitumor activities

A new paradodecatungstate-B compound decorated by transition metal copper, Na₂Cu₅(H₂O)₂₄(OH)₂[H₂W₁₂O₄₂]·10H₂O (1), has been synthesized by convenient aqueous solution method and structurally characterized by single-crystal X-ray diffraction, IR spectrum, elemental analysis and TGA. The compound crystallizes in the triclinic P-1 space group with a = 10.7140(8) Å, b = 12.9476(9) Å, c = 13.6696(10) Å, α = 73.56°, β = 75.73°, γ = 67.69°, V = 1661.8(2) ų and Z = 1. In compound 1, polyanion of [H₂W₁₂O₄₂]^10 − acts as a dodecadentate ligand that links copper and sodium cations, forming a remarkable three-dimensional framework. The experiment of antitumor activities in vitro shows that the title compound exhibits remarkable inhibitory actions on human cervical carcinoma HeLa cells, ovarian carcinoma SKOV-3 cells, hepatoma HepG2 cells and neuroblastoma SHY5Y cells.     

Synthesis,structural characterization and properties of a novel 1D helical chain arsenomolybdate {[Cu(en)2][Cu(en)(H2O)][(Cu(en)2(H2O)] [AsIIIAsVMo9O34)]} · 2H2O

An organic–inorganic hybrid 1D helical chain arsenomolybdate {[Cu(en)₂][Cu(en)(H₂O)][(Cu(en)₂(H₂O)] [As^IIIAs^VMo₉O₃₄)]} · 2H₂O (1) (en = ethylenediamine) has been hydrothermally synthesized and characterized by elemental analyses, IR, UV and CD spectrum, powder X-ray diffraction, TG-DTA and single-crystal X-ray diffraction. The asymmetric unit of 1 consists of a monocapped trivacant Keggin [As^IIIAs^VMo₉O₃₄]^6 − subunit, a pendant [Cu(en)₂(H₂O)]^2 + cation, a pendant [Cu(en)(H₂O)]^2 + cation, one bridging [Cu(en)₂]^2 + cation and two lattice water molecules. It should be noted that 1 illustrates a one-dimensional (1D) helical chain assembled by {[Cu(en)(H₂O)][(Cu(en)₂(H₂O)][As^IIIAs^VMo₉O₃₄)]}^2 − clusters and [Cu(en)₂]^2 + linkers.     

Optimization of carbamazepine removal in O3/UV/H2O2 system using a response surface methodology with central composite design

This study used an ozone/ultraviolet/hydrogen peroxide (O₃/UV/H₂O₂) system to remove carbamazepine (CBZ) from water using a second-order response surface methodology (RSM) experiment with a five-level full-factorial central composite design (CCD) for optimization. The effects of both the primary and secondary interactions of the photocatalytic reaction variables, including O₃ concentration (X₁), H₂O₂ concentration (X₂), and UV intensity (X₃), were examined. The O₃ concentration significantly influenced CBZ and total organic carbon (TOC) removal as well as total inorganic nitrogen ion production (T-N) (p < 0.001). However, CBZ, TOC removal, and T-N production were enhanced with increasing O₃ and H₂O₂ concentrations up to certain levels, and further increases in O₃ and H₂O₂ resulted in adverse effects due to hydroxyl radical scavenging by higher oxidant and catalyst concentrations. UV intensity had the most significant effect on T-N production (p < 0.001). Complete removal of CBZ was achieved after 5 min. However, only 34.04% of the TOC and 36.99% of T-N were removed under optimal concentrations, indicating formation of intermediate products during CBZ degradation. The optimal ratio of O₃ (mg L^? 1): H₂O₂ (mg L^? 1): UV (mW cm^? 2) were 0.91:5.52:2.98 for CBZ removal, 0.7:18.93:12.67 for TOC removal, and 0.94: 4.85:9.03 for T-N production, respectively.     

One 2D anionic coordination polymer with {[Co(H2O)6]}2 + cationic guest for fast and selective adsorption of cationic dyes

One new anionic Coordination Polymer, namely [Co(H₂O)₆]^2 +·[Co₃(bptc)₂(H₂O)₁₀]^2 −·3H₂O (1), where H₄bptc = 3,3′,5,5′-biphenyltetracarboxylate, has been synthesized hydrothermally and characterized. In compound 1, bptc^4 − as tridentate ligands connect the Co^2 + cations to form a 2D layer with 1D pseudo channels encapsulation of [Co(H₂O)₆]^2 + guest. In addition, their adsorption activities for organic dyes were investigated in aqueous solution. The results suggested that the anionic complex 1 show rapid and selective adsorption of cationic dyes for Neutral red, Methylene blue.     

A novel three-dimensional coordination polymer containing tetranuclear [Co4(μ3-OH)2] building blocks: Synthesis,crystal structure and magnetic behavior of {[Co2(btc)(μ3-OH)(H2O)2] · H2O}n

A cobalt coordination polymer {[Co₂(btc)(μ₃-OH)(H₂O)₂] · H₂O}_n 1 (btc = 1,2,4-benzenetricarboxylate) was synthesized hydrothermally and structurally characterized by single-crystal X-ray diffraction method. In 1, the six-coordinated Co(II) ions are held together by two bridging hydroxides to form a tetranuclear [Co₄(μ₃-OH)₂] unit, which are connected further through btc³⁻ ligands in a new μ₇-bridging mode to give a porous three dimensional framework. The study of magnetic properties indicated dominant antiferromagnetic coupling interactions between the adjacent Co(II) sites.     

Solvothermal synthesis,crystal structure and photoluminescent property of a novel 3-D magnesium metal–organic framework Mg1.5(μ5-btec)(H2O)2] · [H2N(CH3)2] · H2O

A novel 3-D magnesium metal–organic framework [Mg_1.5(μ5-btec) (H₂O)₂] · [H₂N(CH₃) ₂] · H₂O (btec = 1,2,4,5-benzenetetracarboxylic acid) has been synthesized under solvothermal conditions, and characterized by single-crystal X-ray structure determination, thermogravimetric analysis, X-ray powder diffraction, IR, and photoluminescent studies.     

X-ray single-crystal structure and magnetic properties of KMn(H2O)5Ru2(CO3)4·5H2O: A layered soft magnet

The temperature manipulation induces the aggregation of Ru₂(CO₃)₄^3 − paddle-wheel precursors and Mn^2 + ions in lower temperature ~ 10 °C forming layer structural complex, K[Mn(H₂O)₄Ru₂(CO₃)₄]·5H₂O (1). It composes of new negative layer {Mn(H₂O)₅Ru₂(CO₃)₄}_nⁿ⁻, and magnetic exchanges between spin centers result in ordering below 3.8 K. The observed critical temperature is like the previously reported 3D hetero-metallic carbonates H_0.3K_0.7Mn[Ru₂(CO₃)₄](H₂O)_5.5, which demonstrates that it is independent of the interlayer connecting in such heterometallic complexes based on square-grid layer {Ru₂(CO₃)₄}_n³ⁿ⁻.     

Enhanced production of benzyl alcohol in the gas phase continuous hydrogenation of benzaldehyde over Au/Al2O3

Exclusive hydrogenation of benzaldehyde to benzyl alcohol in gas phase continuous operation (393–413 K, 1 atm) was achieved over Au/Al₂O₃, Au/TiO₂ and Au/ZrO₂. Synthesis of Au/Al₂O₃ by deposition–precipitation generated a narrower distribution (2–8 nm) of smaller (mean = 4.3 nm) Au particles relative to impregnation (1–21 nm, mean = 7.9 nm) with increased H₂ uptake under reaction conditions and higher benzaldehyde turnover. Switching reactant carrier from ethanol to water resulted in a significant enhancement of selective hydrogenation rate over Au/Al₂O₃ with 100% benzyl alcohol yield, attributed to increased available reactive hydrogen. This response extends to reaction over Au/TiO₂ and Au/ZrO₂.     

Decavanadate with a novel coordination complex: Synthesis and characterization of (NH4)2[Ni(H2O)5(NH3)]2(V10O28)·4H2O

A new compound (NH₄)₂[Ni(H₂O)₅(NH₃)]₂[V₁₀O₂₈]·4H₂O (1) containing a {V₁₀O₂₈} ⁶⁻ anionic cluster and a novel complex cation, [Ni(H₂O)₅(NH₃)]^2 +, has been synthesized and fully characterized by single crystal X-ray crystallography, spectroscopy and thermogravimetric analysis. The presence of the ammonia ligand in the complex cation in 1 was established unambiguously by X-ray crystallography and variable temperature (200–400 °C) thermogravimetric analyses in combination with FTIR spectroscopic studies. The formation of the novel complex species {Ni(H₂O)₅(NH₃)}^2 + during the synthesis of 1 can be rationalized in terms of ligand substitution involving {Ni(H₂O)₆}^2 +.     

A sinusoidal chain constructed from decorated Keggin clusters and {Cu(enMe)2}2+ bridging groups in [Cu(enMe)2(H2O)] [{Cu(enMe)2}{Cu(enMe)2(H2O)W12O40(H2)}] · nH2O

A novel organic–inorganic hybrid material, [Cu(enMe)₂(H₂O)][{Cu(enMe)₂}{Cu(enMe)₂(H₂O)W₁₂O₄₀(H₂)}] · nH₂O (n = 0.33, enMe = 1,2-diaminopropane), has been prepared under mild hydrothermal conditions and characterized by single-crystal X-ray diffraction, IR and magnetic susceptibility measurements. It is revealed that the one-dimensional [{Cu(enMe)₂}{Cu(enMe)₂(H₂O)W₁₂O₄₀(H₂)}]²⁻ chain in the structure shows a unique sinusoidal ruffling, which is constructed from decorated Keggin clusters and {Cu(enMe)₂}²⁺ bridging groups through sharing one terminal and one doubly-bridging oxygen atoms of a cluster. The magnetic measurements show that the compound possesses well-separated Cu²⁺ centers. It was indicated that the hybrid exhibits a good catalytic activity in H₂O₂ decomposition.     

High performance electrochemical H2O2 sensor based on MWCNT thin films fabricated by novel electron beam evaporation

High quality multi-walled carbon nanotubes (MWCNT) were grown by electron beam evaporation (EBE) under a high vacuum of 10⁻⁶ mtorr. The influence of deposition thickness on the orientation, morphology and vibrational bands of MWCNT films fabricated on tantalum (Ta) substrate was discussed. XRD patterns of the film revealed the presence of (002) preferential plane of carbon. Raman spectral analysis show the G-band Raman feature corresponding to high frequency E₂g of first order mode, suggesting that CNTs were composed of crystalline carbon. SEM image of 200 nm thick MWCNT film shows well shaped homogenous fine nanotubes of length ~300 nm and diameter ~70 nm with high purity. The electrochemical performance of the MWCNTs/Ta electrodes was studied by cyclic voltammetry. The sensor prepared with optimum thickness can detect H₂O₂ in the wide range covering 5 µM to 0.025 mM, with the detection limit as low as 0.09 µM. The results demonstrate that the fabrication of MWCNTs/Ta electrode by EBE is a very interesting and useful approach, likely to be a focus of upcoming research efforts in electrochemical sensing.     

Conversions of fuel-N,volatile-N,and char-N to NO and N2O during combustion of a single coal particle in O2/N2 and O2/H2O at low temperature

Oxy-steam combustion is a promising next-generation combustion technology. Conversions of fuel-N, volatile-N, and char-N to NO and N₂O during combustion of a single coal particle in O₂/N₂ and O₂/H₂O were studied in a tube reactor at low temperature. In O₂/N₂, NO reaches the maximum value in the devolatilization stage and N₂O reaches the maximum value in the char combustion stage. In O₂/H₂O, both NO and N₂O reach the maximum values in the char combustion stage. The total conversion ratios of fuel-N to NO and N₂O in O₂/N₂ are obviously higher than those in O₂/H₂O, due to the reduction of H₂O on NO and N₂O. Temperature changes the trade-off between NO and N₂O. In O₂/N₂ and O₂/H₂O, the conversion ratios of fuel-N, volatile-N, and char-N to NO increase with increasing temperature, and those to N₂O show the opposite trends. The conversion ratios of fuel-N, volatile-N, and char-N to NO reach the maximum values at < O₂ > = 30 vol% in O₂/N₂. In O₂/H₂O, the conversion ratios of fuel-N and char-N to NO reach the maximum values at < O₂ > = 30 vol%, and the conversion ratio of volatile-N to NO shows a slightly increasing trend with increasing oxygen concentration. The conversion ratios of fuel-N, volatile-N, and char-N to N₂O decrease with increasing oxygen concentration in both atmospheres. A higher coal rank has higher conversion ratios of fuel-N to NO and N₂O. Anthracite coal exhibits the highest conversion ratios of fuel-N, volatile-N, and char-N to NO and N₂O in both atmospheres. This work is to develop efficient ways to understand and control NO and N₂O emissions for a clean and sustainable atmosphere.     

[Zn(H2O)4][B6O10]: An open-framework borate with acentric structure

An open-framework borate [Zn(H₂O)₄][B₆O₁₀] with acentric structure, has been successfully obtained for the first time under solvothermal conditions. It has been characterized by powder and single crystal X-ray diffraction, IR spectroscopy, diffuse-reflectance spectroscopy and thermogravimetric (TG) analyses, respectively. It crystallizes in the orthorhombic system, space group Pna2₁, a = 11.3140(6) Å, b = 11.8995(7) Å, c = 8.6140(5) Å and Z = 4. In the structure, the alternative connections between [B₃O₇] units give rise to an unprecedented 3D borate framework with 11- and 10-MR channels, in which the [Zn(H₂O)₄]²⁺ complexes are located. It has a cut-off edge below 200 nm and exhibits second harmonic generation (SHG) efficiency approximately 0.4 times that of KH₂PO₄ (KDP).     

Impact of support oxide and Ba loading on the NOx storage properties of Pt/Ba/support catalysts: CO2 and H2O effects

A series of 1 wt.%Pt/_xBa/Support (Support = Al₂O₃, SiO₂, Al₂O₃-5.5 wt.%SiO₂ and Ce_0.7Zr_0.3O₂, x = 5–30 wt.% BaO) catalysts was investigated regarding the influence of the support oxide on Ba properties for the rapid NO_x trapping (100 s). Catalysts were treated at 700 °C under wet oxidizing atmosphere. The nature of the support oxide and the Ba loading influenced the Pt–Ba proximity, the Ba dispersion and then the surface basicity of the catalysts estimated by CO₂-TPD. At high temperature (400 °C) in the absence of CO₂ and H₂O, the NO_x storage capacity increased with the catalyst basicity: Pt/20Ba/Si < Pt/20Ba/Al5.5Si < Pt/10Ba/Al < Pt/5Ba/CeZr < Pt/30Ba/Al5.5Si < Pt/20Ba/Al < Pt/10BaCeZr. Addition of CO₂ decreased catalyst performances. The inhibiting effect of CO₂ on the NO_x uptake increased generally with both the catalyst basicity and the storage temperature. Water negatively affected the NO_x storage capacity, this effect being higher on alumina containing catalysts than on ceria–zirconia samples. When both CO₂ and H₂O were present in the inlet gas, a cumulative effect was observed at low temperatures (200 °C and 300 °C) whereas mainly CO₂ was responsible for the loss of NO_x storage capacity at 400 °C. Finally, under realistic conditions (H₂O and CO₂) the Pt/20Ba/Al5.5Si catalyst showed the best performances for the rapid NO_x uptake in the 200–400 °C temperature range. It resulted mainly from: (i) enhanced dispersions of platinum and barium on the alumina–silica support, (ii) a high Pt–Ba proximity and (iii) a low basicity of the catalyst which limits the CO₂ competition for the storage sites.     

Facile proton conduction via Keggin anion ⋯ H2O H-bonded chain in a Ag+-5-Phenyltetrazole framework by acid-functionalization

A novel Ag⁺-5-Phenyltetrazole framework with Keggin anions (PMo₁₂O₄₀^3 −)⋯ H₂O H-bonded chain resided in channels was hydrothermally obtained. When functionalized by acid molecules, it shows facile proton conduction along the chains, with a decent conductivity of 4.26 × 10^− 4 S cm^− 1at 85 °C under 97% relative humidity.