Effects of various factors on capacitive properties of VO<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>·<Emphasis Type="Italic">n</Emphasis>H<Subscript>2</Subscript>O powders in aqueous electrolyte

In this work, effects of drying temperature, pH of aqueous electrolyte and current density on capacitive performance of VO _x ·nH₂O material were firstly investigated. VO _x ·nH₂O powders were prepared by a melt quenching method. The samples were characterized by X-ray diffraction analysis (XRD) and Fourier transform infrared (FTIR). The capacitive properties of VO _x ·nH₂O samples were examined by cyclic voltammetry and galvanostatic charge/discharge test. VO _x ·nH₂O sample which was obtained at the drying temperature of 80 °C, delivers a maximum specific capacitance of 227.3 F g⁻¹ and exhibits excellent capacity retention in the potential range of −0.3 to 0.7 V at a current density of 200 mA g⁻¹ in NaNO₃ solution with pH 2.     

A New Metal–Organic ZnII Supramolecular Assembled via Hydrogen Bonds and N···N Interactions as a New Precursor for Preparation Zinc(II) Oxide Nanoparticles, Thermal, Spectroscopic and Structural Studies

A new 1D supramolecular involving two different ligands, {[Zn(GB)₂]·(μ-bpe)₃} _n (ClO₄)_2n ·nH₂O (GB = 2-guanidinobenzimidazole and bpe = 1,2-bis(4-pyridyl)ethylene, has been synthesised, characterized by elemental analysis, IR-, ¹H NMR-, ¹³C NMR spectroscopy. The thermal stability of compound {[Zn(GB)₂]·(μ-bpe)₃} _n (ClO₄)_2n ·nH₂O was studied by thermal gravimetric and differential thermal analyses. The single crystal X-ray analysis shows that the complex is a one-dimensional polymer involving macrocycle rings as a result of non-covalent bridging bpe ligands via N–H···N and N···N interactions, N–H···bpe···bpe···H–N, with the basic repeating {[Zn(GB)₂](μ-bpe)₃}(ClO₄)₂·H₂O units and by connecting [Zn(GB)₂]²⁺ nodes. ZnO nanoparticles were obtained by calcination of compound {[Zn(GB)₂]·(μ-bpe)₃} _n (ClO₄)_2n ·nH₂O at 500 °C in air. The nanoparticles were characterized by X-ray diffraction and scanning electron microscopy.     

Diffraction Studies on Concentrated Aqueous Hydrochloric Acid Solutions

X-ray diffraction and neutron diffraction experiments with H/D isotopically substituted aqueous 21 mol% hydrochloric acid solutions were carried out in order to obtain detailed features concerning the intermolecular hydrogen-bonded structure in highly concentrated aqueous acidic solutions. Structure parameters, namely, intermolecular distance, root-mean-square amplitude, and coordination number, for the nearest neighbor H₃O⁺···H₂O interaction were determined from the least-squares-fitting analysis of the observed X-ray interference term. These were, respectively, r(H₃O⁺···H₂O) = 2.45(1) Å; l(H₃O⁺···H₂O) = 0.11(1) Å; and n(H₃O⁺···H₂O) = 1.8(1). The intermolecular nearest neighbor distances, r(H···H) = 2.02(5) Å and r(O···H) = 1.69(2) Å, were determined from the least-squares fit to partial structure factors, a_ij (Q), derived from the observed neutron intermolecular interference terms for sample solutions with different H/D isotopic ratios. The present values of intermolecular distances are significantly shorter than those for pure liquid water, implying that extremely strong hydrogen bonds exist in concentrated aqueous acidic solutions.     

Chemical Processes During Energy‐Saving Preparation of Lightweight Ceramics

Lightweight glass‐ceramic material similar to foam glass was obtained at 700°C–800°C directly from alkali‐activated silica clay and zeolitized tuff without preliminary glass preparation. It was characterized by low bulk density of 100–250 kg/m³ and high pore size homogeneity. Chemical processes occurring in alkali‐activated silica clay and zeolitized tuff were studied using X‐ray diffraction, thermal gravimetry, IR‐spectroscopy, and scanning electron microscopy. Pore formation in both compositions is caused by dehydration of hydrated sodium polysilicates (Na₂O·mSiO₂·nH₂O), formed during alkali activation. Additional pore‐forming gas source in alkali‐activated zeolitized tuff is trona, Na₃(CO₃)(HCO₃)·2H₂O, formed during interaction between unbound NaOH and CO₂ and H₂O from air. Influence of mechanical activation of raw materials on chemical processes occurring in alkaline compositions was also studied.     

Novel Au/TiO2/Al2O3 · xH2O catalysts for CO oxidation

Au/Al₂O₃ · xH₂O and Au/TiO₂/Al₂O₃ · xH₂O (x = 0–3) catalysts were prepared by assembling gold nanoparticles on neat and TiO₂-modified Al₂O₃, AlOOH, and Al(OH)₃ supports, and their catalytic activity in CO oxidation was tested either as synthesized or after on-line pretreatment in O₂–He at 500 °C. A promotional effect of TiO₂ on the activity of gold catalysts was observed upon 500 °C-pretreatment. The catalyst stability as a function of time on stream was tested in the absence or presence of H₂, and physiochemical characterization applying BET, ICP-OES, XRD, TEM, and ²⁷Al MAS NMR was conducted.     

Hydrothermal Syntheses and Crystal Structures of Two Coordination Polymers with Terephthalic Acid and N-Donor Ligand: 2-Methyldipyrido[3,2-f:2′,3′-h]quinoxaline

Two 3D coordination polymers, [Cd(BDC)(Medpq)·H₂O]_n 1, and [Co(BDC)(Medpq)·H₂O] _n 2 (BDC = terephthalic acid, Medpq = 2-Methyldipyrido[3,2-f:2′,3′-h]quinoxaline), have been synthesized by self-assembly. The structure analyses show that both of the two coordination polymers are formed by 1D infinite chains through non-covalent interactions, and both of them are based on 1D zigzag ones. The photoluminescent study of the coordination polymer [Cd(BDC)(Medpq)·H₂O] _n shows that it exhibit fluorescent emission bands at 567.7 nm.     

Synthesis and photocatalytic properties of H2La2Ti3O10/TiO2 intercalated nanomaterial

H₂La₂Ti₃O₁₀/ TiO₂ intercalated nanomaterial was fabricated by successive intercalation reactions of H₂La₂Ti₃O₁₀ with n-C₆H₁₃NH₂/C₂H₅OH mixed solution and acid TiO₂ sol, followed by irradiating with a high-pressure mercury lamp. The intercalated materials possess a gallery height of 0.46 nm and a specific surface area of 31.58 m²·g⁻¹, which indicate the formation of a porous material. H₂La₂Ti₃O₁₀/TiO₂ shows photocatalytic activity for the decomposition of organic dye under irradiation with visible light and the activity of TiO₂ intercalated material was superior to the unsupported one.     

Nano-sized crystallites of vanadyl pyrophosphate as a highly selective catalyst for n-butane oxidation

Exfoliation-reduction of VOPO₄ · 2H₂O in a mixed alcohol consisting of 2-butanol and ethanol, followed by the thermal treatment in the presence of n-butane, O₂, and He at 663 K for 300 h, produces novel nano-sized crystallites (~ 50 nm) of (VO)₂P₂O₇. The nano-sized (VO)₂P₂O₇ crystallites exhibit a high selectivity to maleic anhydride (~ 84%) for the selective oxidation of n-butane.     

Butadiene polymerization with nickel compounds: Effect of cocatalysts

The preparation of a high cis-1,4-polybutadiene, using a novel ternary catalyst system composed of triethylaluminum, a soluble nickel compound, and boron trifluoride diethyl etherate has been reported in the literature. The present paper reports the polymerization results obtained when the triethylaluminum was replaced with other alkylaluminums and the BF₃ · Et₂O was replaced with other BF₃ complexes or HF · Et₂O. When utilizing BF₃ · Et₂O, both the polymerization rate and the polymer DSV decreased significantly as the length of the alkyl group in the alkylaluminum increased from C₁ to C₆. However, the length and nature of the alkyl group had virtually no effect when utilizing BF₃ · phenolate (BF₃ · 2C₆H₅OH) and only a small effect with HF · Et₂O; although the length of the alkyl group had no significant effect when using BF₃ complexes of aromatic aldehydes, the branched alkyl groups gave greater polymerization rates than did the corresponding n-alkyls. In summary, the strongly acidic complexes, BF₃ · phenolate and HF · etherate, promoted rapid polymerization when employed with any of the alkylaluminums. However, with other BF₃ complexes, the alkylaluminum selected had an important influence upon either the conversion and/or the polymer DSV.     

Seven Coordinated Metal Complexes derived from (3-Carboxymethoxy-Naphthalen-2-yloxy)-Acetic Acid and Coordination Polymers

A design principle for seven coordinated metal carboxylate complexes and coordination polymers of Mn(II), Cd(II) and Na(I) derived from (3-carboxymethoxy-naphthalen-2-yloxy)-acetic acid (LH2) is presented. The complexes/coordination polymer [Mn(L)(H₂O)₃]·3H₂O (1), [{Cd(L)(H₂O)₂}·H₂O]_n (2); [Cd(L)(py)₃]·3H₂O (3) have metal ions in pentagonal bipyramid environments (py = pyridine). The coordination polymer [{Cd(L)(H₂O)₂}·H₂O]_n (2) may be considered to be the self-assembly of hexacoordinated [Cd(L)(H₂O)₂] units; it reacts with pyridine to form mono-nuclear complex 3. Depending on the reaction conditions, Ni-coordination polymers of L adopt different compositions. From the reaction carried out with NiCl₂ and NaOH in quinoline and water, a hetero bimetallic coordination polymer; namely, [[NaL(H₂O)]₂Ni(H₂O)₄]_n (4) is obtained. A similar reaction in pyridine-water solvent led to [{Ni(L)(py)₃}.py]_n (5). The coordination polymer 5 has pyridine in its interstices held by C–H···π interactions.     

Preparation and characterization of RuO<Subscript>2</Subscript> · <Emphasis Type="Italic">x</Emphasis>H<Subscript>2</Subscript>O/carbon aerogel composites for supercapacitors

A series of RuO₂ · xH₂O/carbon aerogel (CA) composite electrode materials was prepared by a chemical precipitation method. Ultrasonication was used to accelerate the chemical reaction and improve the dispersion of RuO₂ · xH₂O particles on the surface and the pores of the aerogel. The structure and morphology of the as-prepared composite were characterized by N₂ adsorption isotherm, X-ray diffraction (XRD), and field emission-scanning electron microscopy (FE-SEM). The results showed that the CA had a pearly network structure and the composites had a relatively high specific surface area and mesopore volume. The electrochemical performance of the composite electrodes was studied by cyclic voltammetry, galvanostatic charge/discharge measurements and electrochemical impedance measurements. The results indicated a substantial increase in the specific capacitance of the composite. Moreover, the utilization efficiency of RuO₂ · xH₂O was greatly improved by loading it on the conductive and porous CA due to a significant improvement in the inter-particle electronic conductivity and the extensive mesoporous network of the composites.     

Preparation and characterization of multicomponent porous materials prepared by the sol-gel process

An experimental strategy was developed to obtain transparent Si-Al-Ti-Ni-Mo and Si-Zr-Ti-Ni-Mo sols via the sol-gel process. The sol was prepared from Si(OEt)₄ (TEOS), Al(OBu^s)₃ (OBu^s: C₂H₅CH(CH₃)O), Ti(OEt)₄ (OEt: OCH₂CH₃), Zr(OPrⁿ)₄ (OPrⁿ: OCH₂CH₂CH₃). In both cases nickel nitrate hexahydrate (Ni(NO₃)₂ · 6H₂O) and ammonium heptamolybdate tetrahydrate ((NH₄)₆Mo₇O₂₄ · 4H₂O) were the Ni and Mo sources, respectively. The sols were characterized by Fourier Transform Infrared Spectroscopy (FTIR). Assignments of the simultaneous formation of the Si-O-Al, Si-O-Ti, Si-O-Ni, and Si-O-Zr bonds were done. The sols were polymerized at room temperature (293 K) to obtain gels, and these were dried at 423 K and calcined at 573, 853 and 893 K in air. The characterization techniques used were small-angle X-ray scattering (SAXS), X-ray diffraction (XRD), scanning electron microscopy (SEM), and ²⁹Si and ²⁷Al magic angle spinning nuclear magnetic resonance (MAS NMR). The density of the solids was measured following ASTM method D-4892 and the porosity and surface area were determined by N₂ adsorption/desorption isotherms. The corresponding average pore diameters were evaluated using the BJH, HK, and DA methods.     

Microwave‐assisted Hydrothermal Synthesis of Single‐crystal Nanorods of Rhabdophane‐type Sr‐doped LaPO4·nH2O

A novel, simple, soft, and fast microwave‐assisted hydrothermal method was used for the preparation of single‐crystal nanorods of hexagonal rhabdophane‐type La_1?xSr_xPO_4?x/2·nH₂O (x = 0 or 0.02) from commercially available La(NO₃)₃·6H₂O, Sr(NO₃)₂, and H₃PO₄. The synthesis was conducted at 130°C for 20 min in a sealed‐vessel microwave reactor specifically designed for synthetic applications, and the resulting products were characterized using a wide battery of analytical techniques. Highly uniform, well‐shaped nanorods of LaPO₄·nH₂O and La_0.98Sr_0.02PO_3.99·nH₂O were readily obtained, with average length of 213 ± 41 nm and 102 ± 25 nm, average aspect ratio (ratio between length and diameter) of 21 ± 9 and 12 ± 5, and specific surface area of 45 ± 2 and 51 ± 1 m²/g, respectively. In both cases, the single‐crystal nanorods grew anisotropically along their c crystallographic‐axis direction. At 700°C, the hexagonal rhabdophane‐type phase has already transformed into the monoclinic monazite‐type structure, although the undoped and Sr‐doped nanorods retain their morphological features and specific surface area during calcination.     

A low-potential, H2O2-assisted electrodeposition of cobalt oxide/hydroxide nanostructures onto vertically-aligned multi-walled carbon nanotube arrays for glucose sensing

A novel nanocomposite was synthesized using a cathodic, low-potential, electrochemical reduction of H₂O₂ to homogeneously deposit cobalt oxide/hydroxide (denoted as CoOx·nH₂O) nanostructures onto vertically well-aligned multi-walled carbon nanotube arrays (MWCNTs), while the MWCNTs were prepared by catalytic chemical vapor deposition (CVD) on a tantalum (Ta) substrate. The CoOx·nH₂O–MWCNTs nanocomposite exhibits much higher electrocatalytic activity towards glucose (Glc) after modification with CoOx·nH₂O than before. This non-enzymatic Glc sensor has a high sensitivity (162.8 μA mM⁻¹ cm⁻²), fast response time (<4 s) and low detection limit (2.0 μM at signal/noise ratio = 3), and a linear dynamic range up to 4.5 mM. The sensor output is stable over 30 days and unaffected by common interferents that co-exist with Glc in analytical samples; it is also resistant to chloride poisoning. These features make the CoOx·nH₂O–MWCNTs nanocomposite a promising electrode material for non-enzymatic Glc sensing in routine analysis.     

Syntheses, Characterization and Crystal Structures of 1D and 2D Organotin Polymers Containing 3-Methyladipic Acid Ligand

Four new organotin (IV) complexes of two types [(R₂Sn)₂(C₇H₁₀O₄)(μ₃-O)] _n (R = Me: 1; nBu: 2; and {(R₃Sn)₂[C₅H₁₀(COO)₂]} _n (R = Me: 3; nBu: 4) have been synthesized by the reaction of 3-methyladipic acid with the corresponding R₃SnCl (R = Me, nBu) under two different experimental conditions. All the complexes were characterized by elemental analysis, FT-IR, and NMR (¹H, ¹³C, ¹¹⁹Sn) spectroscopy. Except for 2, all of the complexes were also characterized by X-ray crystallography. The structural analyzes show that complex 1 is a 1D infinite chain polymer and forms a 2D organotin framework through intermolecular C–H···O interactions and weak Sn···O interactions. Complexes 3 and 4 are 2D network polymers in which 3-methyladipic acid acts as a tetra dentate ligand coordinated to the trialkyltin (IV) ion.     

Ultrasonic-assisted ruthenium-catalyzed oxidation of aromatic and heteroaromatic compounds

Ruthenium-catalyzed oxidation of aromatic and heteroaromatic compounds is reported. It was found that ultrasonic irradiation in a biphasic system consisting of substrate, CH₂Cl₂, H₂O, CH₃CN, NaIO₄ and catalytic amounts of RuCl₃ · nH₂O, accelerates the oxidation reaction to afford the desired products in good yields.     

Synthesis, Structures and Luminescent Properties of Two New Cd(II) Coordination Polymers Based on V-Shaped 3,3′,4,4′-Oxidiphthalic Acid

Two new Cd(II) coordination polymers, namely [Cd₂(H₂OA)₂(μ₂-H₂O)(H₂O)₆] _n ·3nH₂O (1) and [Cd₂(H₂OA)(phen)₂] _n ·nH₂O (2) (H₄OA = 3,3′,4,4′-oxidiphthalic acid, phen = 1,10-phenanthroline) have been synthesized by combining H₄OA or H₄OA and phen with Cd(II) salts under hydrothermal conditions. Single-crystal X-ray diffraction analysis reveals that 1 features a hydrogen-bond directed two-dimensional (2D) layered structure constructed from alternating left- and right-handed double strand helical chains, 2 represents a one-dimensional (1D) chain structure with the phen molecules dangling on it, which is further extended into a three-dimensional (3D) supramolecular framework through strong face-to-face π···π interactions. In addition, luminescent properties of these two compounds were also investigated in the solid state at room temperature.     

Catalytic deNO x properties of novel vanadium oxide based open-framework materials

The deNO _x catalytic properties of a new class of open-framework structure materials, Li₆[Mn₃(H₂O)₁₂V₁₈O₄₂(XO₄)] · 24H₂O (X = V, S) (1), [Fe₃(H₂O)₁₂ V₁₈O₄₂(XO₄)] · 24H₂O (X = V, S) (2), [Co₃(H₂O)₁₂V₁₈O₄₂(XO₄)] · 24H₂O (X = V, S) (3), and Li₆[Ni ₃ ^II (H₂O)₁₂V ₁₆ ^VI V ₂ ^V O₄₂(SO₄)] · 24H₂O (4), have been studied. The crystal structures of these novel systems consist of three-dimensional arrays of vanadium oxide clusters {V₁₈O₄₂(XO₄)} , as building block units, interlinked by {–O–M–O–} (M = Mn, 1; M = Fe, 2; M = Co, 3; M = Ni, 4) bridges. Their open-framework structures contain cavities, similar to those observed in conventional zeolites, which are occupied by exchangeable cations and/or readily removable water of hydration. The catalysts derived from these materials were tested for the selective catalytic reduction (SCR) of nitrogen oxides {NO _x } into N₂ using a hydrocarbon, propylene, as the reducing agent. The catalysts were ineffective under lean burn conditions. However, the new catalysts, especially the one derived from the cobalt derivative (3), showed intriguing deNO _x activity under rich conditions. They remove up to ~ 99% of the toxic NO _x emissions in 1.5% O₂ with 100% selectivity to N₂. The active phase of the catalysts exhibit good stability, can be readily regenerated, and are selective to the desired product-N₂. The catalytic reactions occur at moderately low temperatures (400–500 °C). The catalysts were characterized by FT-IR, temperature programmed reactions (TPR and TPO), SEM, BET surface area measurements, elemental analysis, and X-ray diffraction (XRD). Additional advanced techniques were used to further characterize the catalyst phases that showed most promising deNO _x activity and increased tolerance to oxygen.     

A green process for recovery of H2SO4 and Fe2O3 from FeSO4·7H2O by modeling phase equilibrium of the Fe(П)– –H+–Cl– system

Ferrous sulfate heptahydrate FeSO₄·7H₂O is a major waste produced in titanium dioxide industry by the sulfate process and has caused heavy environmental problem. A new green process for the treatment of FeSO₄·7H₂O was proposed to make use of iron source and recycle sulfate source as H₂SO₄. It was found that by adding concentrated HCl to the FeSO₄ solution, FeCl₂·4H₂O was crystallized out, which was subsequently calcined to produce Fe₂O₃ and HCl. Concentrated H₂SO₄ solution (about 65 wt %) was obtained by evaporating the FeCl₂·4H₂O‐saturated filtrate. To facilitate the process development and design, the solubilities of FeCl₂·4H₂O in HCl, H₂SO₄, and HCl + H₂SO₄ solutions were measured and the experimental data were regressed with both the mixed‐solvent electrolyte model and the electrolyte NRTL model. On the basis of the prediction of the optimum conditions for the crystallization of FeCl₂·4H₂O, material balance of the new process was calculated. FeCl₂·4H₂O and Fe₂O₃ were obtained from a laboratory‐scale test with about 70% recovery of ferrous source for a single cycle, indicating the feasibility of the process. © 2017 American Institute of Chemical Engineers AIChE J, 63: 4549–4563, 2017     

One-pot Synthesis of 5-Unsubstituted 3,4-Dihydropyrimidin-2(1H)-ones from Aldehydes,Ketones, and Urea under Solvent-free Conditions

Various 5-unsubstituted 3,4-dihydropyrimidin-2(1H)-ones were synthesized efficiently by a one-pot three-component condensation of aromatic aldehydes, aromatic ketones, and urea using SnCl₂·2H₂O as a catalyst under solvent-free conditions. All products were identified by IR, NMR, MS, and elemental analysis. The novel method offers several advantages such as excellent yields (81–95%), short reaction time (5–16 min), broader substrate scope, and environmentally friendly conditions.