Effects of mechanochemical treatment to the vanadium phosphate catalysts derived from VOPO4·2H2O

Modification by using mechanochemical treatment of vanadium phosphate catalysts on the microstructure, morphology, oxygen nature and catalytic performance for n-butane oxidation is described and discussed. In this work, the precursor, VOHPO₄·0.5H₂O prepared by reduction of VOPO₄·2H₂O by isobutyl alcohol was subjected to a high energy planetary ball mill for 30, 60 and 120 min in ethanol. The ball milling process reduced the crystallite size of the catalysts and consequently increased their surface area. The morphologies of the milled catalysts are dependent on milling time. The highest reactivity and mobility of the lattice oxygen species has been achieved by the catalyst milled for 60 min with lower reduction peak temperature and higher amount of oxygen atoms removed. The oxygen species removed from the active V⁴⁺ phase was shown to be correlated with the rate of reaction. A good relationship was also found between the oxygen species associated with V⁵⁺ and maleic anhydride selectivity. However, a larger amount of this oxygen species will give a deleterious effect on the conversion rate. The present study demonstrate that the mechanochemical method (with an appropriate duration) effectively enhanced the catalytic activity by increasing the surface area and controlling the reactivity, and that the amount of oxygen species contributed to the partial oxidation of n-butane to maleic anhydride.     

Volatile constituents of Custard Apple

Summary Volatile components in Custard Apple (Annona atemoya) have been isolated by both trapping on Tenax GC followed by thermal desorption and by simultaneous distillation extraction (SDE). Analysis by capillary gas chromatography-mass spectrometry led to the characterisation of 40 components. Twenty components were identified in the headspace sample, and 94% of the GC peak area consisted of esters. The major components were methyl and ethyl butanoate and methyl hexanoate. All 25 components detected in the SDE extract were terpenes, major components being α- and β-pinene, E-ocimene and germacrene-D.     

Magnetochemical Properties and Reactions of Vanadium(III) Thiolate Complexes: Preparation of (NEt(4))(3)[V(3)Cl(6)(edt)(3)] and Mixed-Valence (NEt(4))[V(2)(edt)(4)] (edt = Ethane-1,2-dithiolate)

Reactions of the previously reported dinuclear vanadium(III) thiolate anion [V(2)(edt)(4)](2)(-) (edtH(2) = ethane-1,2-dithiol) are described. Treatment of (NEt(4))(2)[V(2)(edt)(4)] (1) in MeCN with equimolar (C(12)H(8)S(2))BF(4) (C(12)H(8)S(2)(+) = the thianthrenium radical cation) results in a one-electron oxidation and isolation of the V(III),V(IV) complex (NEt(4))[V(2)(edt)(4)] (2). The same product can also be obtained by controlled-potential electrolysis of 1 at -0.20 V vs Ag/AgCl. Treatment of 1 in CH(2)Cl(2) with py gives no reaction, but addition of Me(3)SiCl leads to formation of the known V(2)OCl(4)(py)(6) (3). The latter is also formed by the reduction of a 1:1 mixture of VOCl(3) and VCl(3)(THF)(3) in CH(2)Cl(2)/py and by the reaction in CH(2)Cl(2) of VCl(3)(THF)(3) and py with edt(2)(-). Treatment of 1 in MeCN with bpy (2,2'-bipyridine) gives no reaction, but addition of Me(3)SiCl results in formation and isolation of [V(2)OCl(2)(bpy)(4)]Cl(2) (4) identified by spectroscopic comparison with literature data. The reaction of 1 in MeCN with equimolar VCl(3)(THF)(3) and NEt(4)Cl gives (NEt(4))(3)[V(3)Cl(6)(edt)(3)] (5). A more convenient procedure to 5 is the reaction in MeCN of VCl(3)(THF)(3), Na(2)edt, and NEt(4)Cl in a 1:1:1 molar ratio. Complex 5.MeCN crystallizes in triclinic space group P&onemacr; with (at -154 degrees C) a = 14.918(3) ?, b = 17.142(5) ?, c = 11.276(3) ?, alpha = 106.78(1) degrees, beta = 95.03(1) degrees, gamma = 106.18(1) degrees, and Z = 2. The anion contains a near-linear V(3) unit with a face-sharing trioctahedral structure: the three edt(2)(-) groups provide the six bridging S atoms; two edt(2)(-) groups are in a &mgr;-eta(2):eta(2) mode (as in 1), but the third is in a &mgr;(3)-eta(1):eta(2):eta(1) mode. The V.V separations (>3.1 ?) preclude V-V bonding. Variable-temperature solid-state magnetic susceptibility studies have been performed on complexes 1, 2, and 5 in a 1.0 kG field and 5.00-300 K temperature range. For 1, the effective magnetic moment (&mgr;(eff)) gradually decreases from 1.09 &mgr;(B) at 300 K to 0.26 &mgr;(B) at 5.00 K. The data were fit to the Bleaney-Bowers equation, and the fitting parameters were J = -419(11) cm(-)(1) and g = 2.05. The singlet-triplet gap is thus 838 cm(-)(1). For 2, &mgr;(eff) is essentially temperature-independent, slowly decreasing from 1.90 &mgr;(B) at 300 K to 1.86 &mgr;(B) at 55 K and then to 1.63 &mgr;(B) at 5.00 K. The complex thus is S = (1)/(2) with no thermally accessible S = (3)/(2) state. The combined data on 1 and 2, together with the results of EHT calculations, show that 1 and 2 contain a V-V single bond tying up two of the d electrons and that the remaining two d electrons in 1 are antiferromagnetically coupled to give an S = 0 ground state and S = 1 excited state; for 2, the one remaining d electron gives an S = (1)/(2) state. For 5, &mgr;(eff) increases from 5.17 &mgr;(B) at 320 K to a maximum of 6.14 &mgr;(B) at 30.0 K and then decreases slightly to 6.08 &mgr;(B) at 5.00 K. The data were fit to the appropriate theoretical expression to give J = +42.5(6) cm(-)(1), J' = -1.8(5) cm(-)(1), and g = 1.77, where J and J' gauge the interactions between adjacent and terminal V(III) atoms, respectively. The complex has an S = 3 ground state and represents a very rare example of ferromagnetic coupling between V(III) centers.     

Dimuon events produced in high energy antineutrino interactions observed in BEBC

A study is presented of dimuon events from an exposure of BEBC to a wide band $\text{ν}$ beam from the CERN SPS. These data double the available statistics on $\text{ν}$ induced dilepton events observed in bubble chambers. The relative production rate and V⁰ yield have been measured and found to agree with previous experiments. The analysis of several kinematical variables shows that the gros features of the data agree with the predictions of the GIM model. Some indication exists that part of the signal could be due to quasi elastic production of the “beautiful baryon”, but the statistical significance is too weak to draw definitive conclusions.     

Oxidation of Benzyl Alcohol and Carbon Monoxide Using Gold Nanoparticles Supported on MnO2 Nanowire Microspheres

MnO₂ was synthesised as a catalyst support material using a hydrothermal method. This involved reacting MnSO₄ ? H₂O and (NH₄)₂S₂O₈ at 120 °C for a range of crystallisation times, which affords control over the morphology and phase composition of the MnO₂ formed. Gold was deposited on these supports using sol‐immobilisation, impregnation and deposition precipitation methods, and the resultant materials were used for the oxidation of benzyl alcohol and carbon monoxide. The effect of the support morphology on the dispersion of the gold nanoparticles and the consequent effect on the catalytic performance is described and discussed.     

Photochemistry of RuII 4,4′‐Bi‐1,2,3‐triazolyl (btz) Complexes: Crystallographic Characterization of the Photoreactive Ligand‐Loss Intermediate trans‐[Ru(bpy)(κ2‐btz)(κ1‐btz)(NCMe)]2+

We report the unprecedented observation and unequivocal crystallographic characterization of the meta‐stable ligand loss intermediate solvento complex trans‐[Ru(bpy)(κ²‐btz)(κ¹‐btz)(NCMe)]²⁺ ( 1 a ) that contains a monodentate chelate ligand. This and analogous complexes can be observed during the photolysis reactions of a family of complexes of the form [Ru($\widehat{NN}$ )(btz)₂]²⁺ ( 1 a – d : btz=1,1′‐dibenzyl‐4,4′‐bi‐1,2,3‐triazolyl; $\widehat{NN}$ =a) 2,2′‐bipyridyl (bpy), b) 4,4′‐dimethyl‐2,2′‐bipyridyl (dmbpy), c) 4,4′‐dimethoxy‐2,2′‐bipyridyl (dmeobpy), d) 1,10‐phenanthroline (phen)). In acetonitrile solutions, 1 a – d eventually convert to the bis‐solvento complexes trans‐[Ru($\widehat{NN}$ )(btz)(NCMe)₂]²⁺ ( 3 a – d ) along with one equivalent of free btz, in a process in which the remaining coordinated bidentate ligands undergo a new rearrangement such that they become coplanar. X‐ray crystal structure of 3 a and 3 d confirmed the co‐planar arrangement of the $\widehat{NN}$ and btz ligands and the trans coordination of two solvent molecules. These conversions proceed via the observed intermediate complexes 2 a – d , which are formed quantitatively from 1 a – d in a matter of minutes and to which they slowly revert back on being left to stand in the dark over several days. The remarkably long lifetime of the intermediate complexes (>12 h at 40 °C) allowed the isolation of 2 a in the solid state, and the complex to be crystallographically characterized. Similarly to the structures adopted by complexes 3 a and d , the bpy and κ²‐btz ligands in 2 a coordinate in a square‐planar fashion with the second monodentate btz ligand coordinated trans to an acetonitrile ligand.     

Relative Permeability Analysis of Tube Bundle Models

The analytical solution for calculating two-phase immiscible flow through a bundle of parallel capillary tubes of uniform diametral probability distribution is developed and employed to calculate the relative permeabilities of both phases. Also, expressions for calculating two-phase flow through bundles of serial tubes (tubes in which the diameter varies along the direction of flow) are obtained and utilized to study relative permeability characteristics using a lognormal tube diameter distribution. The effect of viscosity ratio on conventional relative permeability was investigated and it was found to have a significant effect for both the parallel and serial tube models. General agreement was observed between trends of relative permeability ratios found in this work and those from experimental results of Singhal et al. (1976) using porous media consisting of mixtures of Teflon powder and glass beads. It was concluded that neglecting the difference between the average pressure of the non-wetting phase and the average pressure of the wetting phase (the macro-scale capillary pressure) – a necessary assumption underlying the popular analysis methods of Johnson et al. (1959) and Jones and Roszelle (1978) – was responsible for the disparity in the relative permeability curves for various viscosity ratios. The methods therefore do not account for non-local viscous effects when applied to tube bundle models. It was contended that average pressure differences between two immiscible phases can arise from either capillary interfaces (micro-scale capillary pressures) or due to disparate pressure gradients that are maintained for a flow of two fluids of viscosity ratio that is different from unity.