Research on thermal decomposition of trinitrophloroglucinol salts by DSC, TG and DVST

The thermal decomposition of the four nitrogen-rich salts of ammonia (NH₄), aminoguanidine (AG), carbohydrazide (CHZ) and 5-aminotetrazo (ATZ) based on trinitrophloroglucinol (H₃TNPG) was investigated using the differential scanning calorimetry (DSC), thermogravity (TG), and dynamic vacuum stability test (DVST). DSC and TG methods research the complete decomposition, while DVST method researches the very early reaction stage. The peak temperatures of DSC curves are consistent with the temperatures of maximum mass loss rates of TG curves. The apparent activation energies of these H₃TNPG-based salts obtained by DSC and DVST have the same regularity, i.e., (ATZ)(H₂TNPG)·2H₂O < (CHZ)(HTNPG)·0.5H₂O < NH₄(H₂TNPG) < (AG)(H₂TNPG). The thermal stability order is (ATZ)(H₂TNPG)·2H₂O < (CHZ)(HTNPG)·0.5H₂O < (AG)(H₂TNPG) < NH₄(H₂TNPG), which was evaluated by DVST according to the evolved gas amount of thermal decomposition. DVST can monitor the real-time temperature and pressure changes caused by thermal decomposition, dehydration, phase transition and secondary reaction, and also evaluate the thermal stability and kinetics.      

Synthesis and characterization of nanosized NiO2 and NiO using Triton® X-100

Nanosized NiO₂ particles with an average diameter of 15 nm are prepared by treating of Ni(NO₃)₂ · 6H₂O with an aqueous solution of KClO in the presence of Triton® X-100. This black fine powder of nickel peroxide was characterized by XRD diffraction, energy dispersive spectroscopy (EDS) and scanning electron microscopy (SEM). The as-prepared NiO₂ can be easily transformed to nanosized NiO merely by washing it with acetone. The obtained NiO has an average diameter of 40 nm and was characterized by the same means used for NiO₂. The nanoparticles of NiO₂ and NiO were obtained in high yields and purities.      

Hydrogen bonding-based 3D supramolecular architecture of [Cu(CHA)2][TCM]·11H2O

Reaction of Na₄TCM (1) (H₄TCM = tetra[4-(carboxyphenyl)oxamethyl]methane) with [Cu(CHA)](ClO₄)₂ (2)(CHA = 1,3,6,8,11,14-hexaaz atricyclo[12.2.1.1.^8,11] octadecane) in a DMF-water mixture yields [Cu(CHA)]₂[TCM] (3). Structural analysis of [Cu(CHA)]₂[TCM]·11H₂O (3·11H₂O) by single crystal X-ray diffraction reveals strong copper-oxygen bonds between two complex cations and the tetraanion leading to a 3D coordination network (zwitterionic structure), consolidated through additional NH...O=C hydrogen bonding within the cation/anion association. The resulting coordination geometry around a copper atom is a distorted square pyramidal with an oxygen atom of the anionic ligand in the apical position. A 3D supramolecular network is developed in the crystal based only on NH...OC hydrogen bonds between the macrocyclic metallic tecton and the carboxylate groups of neighboring 3D coordinated (zwitterionic) moieties. The pseudotetrahedral TCM^4? tetraanionic ligand induces a diamondoid architecture formed of large distorted adamantanoid cages.      

New 5-bromo-2-hydroxybenzaldehyde S-ethylisothiosemicarbazone and its mixed-ligand Cu(II) complex with imidazole: synthesis, characterization and DFT calculation

A new Schiff base ligand of 5-bromo-2-hydroxybenzaldehyde S-ethyl-isothiosemicarbazone (H₂L) was synthesized and its mixed-ligand Cu(II) complex was also prepared by reaction of Cu(NO₃)₂·3H₂O with H₂L and imidazole. Their structures were fully characterized by elemental analysis, FT-IR, molar conductivity and UV-Vis methods. The analytical data suggest that the metal, H₂L and imidazole ratios in the Schiff base complex are 1:1:1. Single crystal diffraction was also used to better understand the molecular structure of the Cu(II) complex. The results of physico-chemical analyses of the Schiff base complex reveal the coordination geometry around the central atom is square planar. The H₂L ligand (NNO donor) is coordinated to the metal center as a tridentate bionegatively agent. Another position of the square planar geometry is occupied by the imidazole ligand. Furthermore, computational studies of the new complex were performed by carrying out DFT calculations. Geometry optimization and natural band analysis of the complex is discussed in further detail.      

Novel Cu and Cu2In/aluminosilicate type catalysts for the reduction of biomass-derived volatile fatty acids to alcohols

This work relates to the consecutive reduction of short chain carboxylic acids (volatile fatty acids, VFAs) to alcohols as main products. Acetic acid (AA) was used as a reactant to model the VFAs that can be produced by either thermochemical or biological biomass degradation. The amorphised zeolite supported copper catalysts (Cu/SiAl), especially the In-modified CuIn/SiAl catalysts, showed high hydroconversion activity and selectivity for alcohol, ester and aldehyde. Catalysts containing dispersed copper particles in amorphous aluminosilicate were obtained by dehydrating and H₂-reducing Cu-forms of low-silica synthetic zeolites (A, X, P). The activity of the highly destructed Cu-aluminosilicates was found to depend on the structure of the zeolite precursor. The formation of ethyl acetate could be suppressed by adding water to the AA feed and by modifying the catalyst, e.g. by In₂O₃ additive. In the catalysts modified by In₂O₃ additive formation of copper-indium alloy phase (Cu₂In intermetallic compound) was detected resulting in a different selectivity than the one recorded for the Cu/SiAl.      

Synthesis, characterization and magnetic investigation of (NH4)0.5Mn1.25(H2O)2[BP2O8]·0.5H2O

A new borophosphate compound with the composition (NH₄) _χ Mn_((3?χ)/2)(H₂O)₂ [BP₂O₈]·(1?x)H₂O was prepared under mild hydrothermal conditions and characterized by X-ray powder diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR) methods. The title compound was synthesized from MnCl₂·2H₂O, H₃BO₃, and (NH₄)₂HPO₄ with variable molar ratios by heating at 180 °C for 7 days in an autoclave. The X-ray diffraction data of the water insoluble polycrystalline powder was indexed using the TREOR program in hexagonal system with the unit cell parameters of a = 9.5104, c = 15.7108 Å, Z = 6 and the space group P6₅ (No.176). (NH₄) _χ Mn_((3?χ)/2)(H₂O)₂ [BP₂O₈]·(1?x)H₂O is isostructural with (NH₄) _χ M _((3?χ) ^2)/II (H₂O)₂ [BP₂O₈]·(1?x)H₂O (M^II = Co, Cd, Mg; x = 0.5–1). Its unit cell parameters and hkl values were in good agreement with the other isostructural compounds. This is the first report presenting both the synthetic details and the indexed X-ray powder diffraction pattern of this compound along with the characterization by FTIR, thermal gravimetric analysis, scanning electron microscopy and EPR.      

Comparative studies of Pd, Ru, Ni, Cu/ZnAl2O4 catalysts for the water gas shift reaction

The activity of monometallic Pd, Ru, Ni and Cu catalysts supported on spinel ZnAl₂O₄ for water gas shift reaction (WGS) was investigated. The physicochemical properties of each catalyst was studied by XRD, TPR, BET and chemisorption methods. The highest activity was obtained for Cu/ZnAl₂O₄ among the catalysts tested. The activation process carried out in a reducing atmosphere 5%H₂-95%Ar in the case of Cu/ZnAl₂O₄ system lead to the catalytic activity improvement. In the case of copper catalysts, the water gas shift reaction proceeded by the redox surface mechanism between Cu⁰/Cu⁺. The PdZn alloy formation after reduction at 350°C was shown.      

Crystal structures and spectral properties of new Cd(II) and Hg(II) complexes of monensic acid with different coordination modes of the ligand

The single crystal X-ray structures and the spectroscopic properties of complexes of monensic acid (C₃₆H₆₂O₁₁·H₂O) with toxic metal ions of Cd(II) and Hg(II) are discussed. The cadmium(II) complex (1) is of composition [Cd(C₃₆H₆₁O₁₁)₂(H₂O)₂] and crystallizes in the monoclinic system (space group P2(1), Z = 2) with a = 12.4090(8), b = 24.7688(16), c = 14.4358(11) Å, β = 91.979(7)°. Two ligand monoanions are bound in a bidentate coordination mode to Cd(II) via the carboxylate and the primary hydroxyl oxygens occupying the equatorial plane of the complex. The axial positions of the inner coordination sphere of Cd(II) are filled by two water molecules additionally engaged in intramolecular hydrogen bonds. The Hg(II) complex (2), [Hg(C₃₆H₆₀O₁₁)(H₂O)], crystallizes in the orthorhombic system (space group P2(1)2(1)2(1), Z = 4) with a = 12.7316(2), b = 16.4379(3), c = 18.7184(4) Å. The monensic acid reacts with Hg(II) in a tetradentate coordination manner via both oxygen atoms of the carboxylate function and oxygens of two hydroxyl groups. The twofold negative charge of the ligand is achieved by deprotonation of carboxylic and secondary hydroxyl groups located at the opposite ends of the molecule. Hg(II) is surrounded by five oxygen atoms in a distorted square pyramidal molecular geometry.

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Synthesis, characterization, solution study and crystal structure of complexes of Cr(III), Co(II), Ni(II) and Cu(II) with chelidamic acid and 2,9-dimethyl-1,10-phenanthroline

The title compounds, (dmpH)[Cr(chelH)₂]·3H₂O, 1, (dmpH)[Co(chelH₂)(chelH)]·3H₂O, 2, (dmpH)[Ni(chelH₂)(chelH)]·2H₂O, 3 and [Cu(chelH)(dmp)]·3H₂O, 4 (dmp is 2,9-dimethyl-1,10-phenanthroline and chelH₃ is chelidamic acid or 4-hydroxypyridine-2,6-dicarboxylic acid) were obtained by one-pot reaction of 2,9-dimethyl-1,10-phenanthroline and 4-hydroxypyridine-2,6-dicarboxylic acid with corresponding salts in aqueous solution. The compounds were identified by IR, MS, elemental analysis and single crystal X-ray crystallography; also they were studied in the solution phase. The compounds 1, 2 and 3 are similar in coordination sphere around the metal ions, with some differences between protonation sites of chelidamate ion and the charge of complex, but compound 4 is essentially different. The compounds 1, 2 and 3 are six coordinated, but 4 is five coordinated. There are various O–H···O, O–H···N and N–H···O hydrogen bonds found in the structures. In a solution study, the protonation constants of dmp and chel, the equilibrium constants of the chel–dmp proton-transfer system and the stoichiometry and stability of complexation of this system with Cr(III), Co(II), Ni(II) and Cu(II) ions in an aqueous solution were investigated by potentiometric pH titration method. The stoichiometry of the most complexes species in solution was found to be very similar to the crystalline cited metal ion complexes.     

Effect of anions on supramolecular architecture of benzimidazole-based ionic salts

The reaction of N,N,N′,N′-tetrakis-(1H,benzimidazol-2ylmethyl) propane-1,3-diamine (L) with different inorganic acids affords salts viz., LH₄ ⁴⁺·4ClO₄ ^?·H₂O (1), LH₄ ⁴⁺·4Cl^?·2H₂O (2), LH₄ ⁴⁺·2H₂PO₄ ^?·H₇P₃O₁₂ ^2?·3H₃PO₄ (3), LH₄ ⁴⁺·4NO₃ ^? (4), and 2LH⁺·2CF₃COO^?·5H₂O (5). The X-ray crystallographic studies revealed that the proton transfer occurred from acid to the ligand. It also demonstrated that different type of hydrogen bond between protonated ligand and anions is responsible for the supramolecular framework. The colorimetric test showed color change upon the addition of acids in the solution of the ligand. The photo-physical experiments suggested the fluorescence properties of ligand in the presence of acids.     

Simplified bicyclic cage-type molecule as a C 3 -symmetric host: X-ray and FTIR characterization of encapsulation of a nitrile molecule

We synthesized a new amine-type host molecule 2 by 2 steps, using 1,3,5-tris(aminomethyl)-2,4,6-trimethylbenzene and 2,6-pyridinedicarboxaldehyde as starting materials. Recrystallization of 2·6H₂O from hot acetonitrile, hot propionitrile and hexane/benzonitrile solutions gave colorless crystals of MeCN@2·MeCN·2H₂O, EtCN@2·EtCN, and 8H₂O@2·PhCN. In the former two crystals, the nitrile compounds were captured inside of the cavity of 2. On the other hand, in the latter one, the benzonitrile was laid outside 2. Infrared spectral measurements of MeCN@2·MeCN·2H₂O, EtCN@2·EtCN, and 8H₂O@2·PhCN showed that absorption bands assignable to the C ≡ N stretching vibrations of nitrile compounds were observed at 2240, 2241, and 2226 cm^?1 for MeCN@2·MeCN·2H₂O, EtCN@2·EtCN, and 8H₂O@2·PhCN, respectively. The former two peaks shifted to a lower energy region by 6–13 and 21–26 cm^?1 than those of liquid and gas phases of MeCN and EtCN, respectively. That for 8H₂O@2·PhCN shifted to a slightly lower region by 2 and 12 cm^?1 those of liquid and gas states of PhCN, respectively, indicating that the outer benzonitrile molecule dose not so much interact with 2 in the crystal.     

Mechanochemical synthesis of thenoyltrifluoroacetone-1,10-phenanthroline europium complex

The paper considers the possibilities for mechanochemical synthesis of rare earth complexes. The complex Eu(TTA)₃·phen (HTTA — 2-thenoyltrifluoroacetone, phen — 1,10-phenanthroline) is synthesized by mechanical treatment of a mixture of EuCl₃.6H₂O, HTTA, phen and NaOH in planetary ball mill Pulverisette 7 for 30 min at 800 min^?1. The non reacted starting reagents and reaction side products are separated by treating activated mixture with water-ethanol solution following a procedure proposed in the literature. The elemental composition, X-ray diffraction pattern, IR spectra, optical properties (excitation and emission spectra, luminescence lifetime) and morphology of the mechanochemically synthesized complex are compared with those of the complex prepared from solution by the conventional method. The results confirm close similarity in the molecular structure and identity of the elemental composition, X-ray diffractograms and fluorescence properties of the compounds prepared by both methods.      

Syngas production by biogas reforming over the Co-based multicomponent catalysts

The new multicomponent Co-based catalysts with additives of group 8 metal and rare earth elements and supported on alumina have been tested in the dry and steam conversion of a model biogas. The processes were carried out in a flow quartz reactor under the following conditions: atmospheric pressure, a gas hourly space velocity of 1000 h^?1 and temperatures of 300–800°C. The catalysts were characterised using electron microscopy, BET and X-ray analysis. The methane is almost completely converted in the dry reforming of biogas at T≤800°C. Synthesis gas with a ratio of H₂/CO>1.0 is a main product of biogas reforming over the multicomponent catalysts studied. Adding steam in a feed composition increases both the methane conversion and the hydrogen yield at lower temperatures. Almost complete methane conversion occurs at T<750°C in the steam reforming of biogas. The catalysts are highly effective and exhibit stable activity throughout 100 h of continuous testing.      

Synthesis, thermal behavior, and other properties of Y(III) and La(III) complexes with 4,4′-bipyridine and trichloro- or dibromoacetates

New Y(III) and La(III) complexes with 4-bpy (4,4??-bipyridine) and trichloro- or dibromoacetates with the formulae: Y(4-bpy)₂(CCl₃COO)₃·H₂O I, La(4-bpy)_1.5(CCl₃COO)₃·2H₂O II, Y(4-bpy)_1.5(CHBr₂COO)₃·3H₂O III, and La(4-bpy)(CHBr₂COO)₃·H₂O IV were prepared and characterized by chemical, elemental analysis, and IR spectroscopy. Conductivity studies (in methanol, dimethyloformamide, and dimethylsulfoxide) were also described. They are small, crystalline substances. The way of metal?Cligand coordination was discussed. The thermal properties of complexes in the solid state were studied by TG-DTG techniques under dynamic flowing air atmosphere. TG-FTIR system was used to analyze principal volatile thermal decomposition and fragmentation products evolved during pyrolysis in dynamic flowing argon atmosphere for La(III) compounds.     

Catalytic reduction of sulfuric acid to sulfur dioxide

The reduction of H₂SO₄ to SO₂ occurs with a relatively good efficiency only at high temperatures, in the presence of catalysts. Some experimental results, regarding conversion of sulfuric acid (96 wt.%) to sulfur dioxide and oxygen, are reported. The reduction has been performed at 800 ?C 900°C and atmospheric pressure, in a tubular quartz reactor. The following commercial catalysts were tested: Pd/Al₂O₃ (5 wt.% and 0.5 wt.% Pd), Pt/Al₂O₃ (0.1 wt.% Pt) and ??-Fe₂O₃. The fresh and spent catalysts were characterized by X-Ray diffraction and BET method. The highest catalytic activity was determined for 5 wt.% Pd/Al₂O₃, a conversion of 80% being obtained for 5 hours time on stream, at 9 mL h^?1 flow rate of 96 wt.% H₂SO₄. A conversion of 64% was determined for 0.5 wt.% Pd/Al₂O₃ and 0.1 wt.% Pt/Al₂O₃. For ??-Fe₂O₃, a less expensive catalyst, a conversion of 61% for about 60 hours was obtained.      

The synthesis, structure and physical properties of lanthanide(III) complexes with nicotinic acid

This article reports the synthesis of novel, rare-earth coordination complexes with nicotinic acid. Three compounds with the general formula Ln₂[(C₅H₄NCOO)₆(H₂O)₄] (Ln = Yb, 1; Ln = Gd, 2; Ln = Nd, 3) were prepared from relatively cheap and readily available reactants. Their compositions and structure were characterized by IR spectroscopy and single-crystal X-ray diffraction. The magnetic and thermogravimetric properties were also studied. The complexes consist of centrosymetric, dimeric molecules having all six nicotinato ligands coordinated with the central atom in the bidentate mode. The coordination environment of the Ln³⁺ for all three compounds is 8. Here we describe the crystal structure of Yb and Gd complexes with nicotinic acid.      

Synthesis and spectral characterization of stannocanes of the type [O(CH2CH2S)2SnR2](R=Me1,Bun2,Ph3)

The stannocanes of the type [O(CH₂CH₂S)₂SnR₂](R=Me1,Buⁿ 2,Ph3) have been synthesized in an improved method by the reaction of R₂SnCl₂ with 2, 2′-oxydiethanethiol O(CH₂CH₂SH)₂ in molar ratio of 1:1 at the presence of sodium ethoxide in anhydrous ethanol. The reactions are carried out under inert atmosphere. These compounds have been extensively characterized by FT-IR, UV-Vis spectrophotometry, multi-nuclear (¹H, ¹³C, ¹¹⁹Sn) NMR, elemental analysis and mass spectrometry. The obtained data clearly indicates that, there is a strong interaction between oxygen atom of the ligand as a donor and Sn atom of the organotin species as a Lewis acid acceptor. Therefore, the resulted dithiostannocanes possess a transannular secondary bonding and hypervalency at the central Sn atom which leads to an increase in the coordination number of tin from four to five-coordinated tin.      

Synthesis, characterization and structures of copper(II) complexes containing carboxylate and sulfonate groups

Four copper(II) complexes containing Schiff base and reduced Schiff base ligands derived from pyridine-2-aldehyde and amino acid containing carboxylate and sulfonate functional groups (N-(2-pyridylmethylene)-amino acid and N-(2-pyridylmethyl)-amino acid, (amino acids = ??-alanine and aminoethanesulfonic acid) namely, [Cu(Pbals)(H₂O)₂]ClO₄·H₂O 1, [Cu(Pbal)(ClO₄)(H₂O)] 2, [Cu₂(Paes)₂(ClO₄)₂]·2H₂O 3, and [Cu(Pae)(H₂O)]·ClO₄·H₂O 4 have been synthesized and characterized. The structural features of carboxylate and sulfonate donor groups have been elucidated. These copper(II) complexes demonstrate different coordination behaviour of the carboxylate and sulfonate groups. Carboxylate groups in complexes 1 and 2 bridge the metal centers and facilitate the formation of 1D helical coordination polymeric structures. In compound 3, the sulfonate groups bridge the metal centers to form a discrete dinuclear complex. In 4, the sulfonate groups link the neighbouring metal centers to form a 1D coordination polymeric structure.     

Synthesis and study of tetraamminecobalt hydrogen hexamolybdometalates(III)

Tetraamminecobalt hydrogen hexamolybdoferrate [Co(NH₃)₄] · H[FeMo₆O₁₈(OH)₆] · 6H₂O (I) and tetraamminecobalt hydrogen hexamolybdogallate(III) [Co(NH₃)₄] · H[GaMo₆O₁₈(OH)₆] · 6H₂O (II) were synthesized and studied by mass spectrometry, thermogravimetry, IR spectroscopy, and X-ray diffraction. Crystals of I and II are monoclinic; a = 16.21 Å, b = 5.43 Å, c = 12.32 Å, β = 119.63°, V = 1092.11 ų, ρ_calcd = 2.21 g/cm³, and Z = 1 for I; a = 16.24 Å, b = 5.59 Å, c = 12.29 Å, β = 119.79°, V = 1064.05 ų, ρ_calcd = 2.15 g/cm³, and Z = 1 for II. Compounds I and II were used as catalysts for soft oxidation of natural gas.     

Cooligomerization of dominant monomers of C9 fraction of liquid pyrolysis products: comparison of heterogeneous catalytic approach with common methods

Cooligomerization of liquid products of the C9 fraction of diesel fuel pyrolysis to produce cooligomers of wide application is suggested to be carried out with silica-alumina catalysts, among which the activated bentonite clay seems to be optimal. Cooligomerization of the mixture simulating the C₉ fraction composition was studied to compare the suggested heterogeneous catalytic method with other methods of cooligomers production. Different methods have been compared in terms of yield of cooligomers and their properties, namely molecular weight and its distribution, density, unsaturation and colour. The ratio of monomer units in cooligomer has been determined and the monomers conversion degrees have been calculated for different cooligomerization methods. Reasons of structure and composition differences of cooligomers obtained by different methods are suggested.