Guaiacol hydrodeoxygenation kinetics with catalyst deactivation taken into consideration

The hydrodeoxygenation of guaiacol, a compound modeling bio-oil, has been investigated. Experiments have been carried out in an autoclave at 280, 320, and 360°C and an initial hydrogen pressure of about 17 MPa using a Ni-Cu/SiO₂-ZrO₂-La₂O₃ catalyst. A formal kinetic model of the first stage of guaiacol hydrodeoxygenation is suggested. It is assumed that the reaction is first-order with respect to both guaiacol and hydrogen. The model takes into account the deactivation of the catalyst and the decrease in the concentration of the deactivating compounds due to their hydrogenation. A possible cause of deactivation is the formation of coke and heavy intermediates, as well as the competitive adsorption of intermediate products of guaiacol conversion on the active sites of the catalyst. The parameters with which the model satisfactorily fits the observed dependence of the guaiacol concentration on the reaction time have been determined.     

Nucleon matrix elements and baryon masses in the Dirac orbital model

Using the expansion of the baryon wave function in a series of products of single-quark bispinors (Dirac orbitals), the nonsinglet axial and tensor charges of a nucleon are calculated. The leading term yields g _A = 1.27 in good agreement with experiment. Calculation is essentially parameter-free and depends only on the strong coupling constant value α _s . The importance of lower Dirac bispinor component, yielding 18% to the wave-function normalization is stressed. As a check, the baryon decupletmasses in the formalism of this model are also computed using standard values of the string tension σ and the strangequark mass m _s ; the results being in a good agreement with experiment. The text was submitted by the authors in English.     

Infrared quasifixed solutions in a nonminimal supersymmetric standard model

The constraints from LEPII on the mass of the lightest Higgs boson are such that, in the parameter space of the minimal supersymmetric standard model (MSSM), a considerable part of the region that corresponds to the scenario of an infrared fixed point is virtually ruled out by available experimental data. In a nonminimal supersymmetric standard model (NMSSM), the mass of the lightest Higgs boson takes its maximum value in the regime of strong Yukawa coupling, in which case the Yukawa coupling constants are much greater than the gauge coupling constants at the Grand Unification scale $(Y_i (0) \gg \tilde \alpha _i (0))$ . In this limiting case, solutions to the renormalization-group equations are attracted to Hill and infrared fixed lines or surfaces in the space of Yukawa coupling constants; for Y _i (0) → ∞, they are concentrated in the vicinities of quasifixed points. However, this attraction is quite weak. For this reason, solutions to the renormalization-group equations are grouped near some line on the Hill surface when all Y _i (0) are close to unity. Approximate solutions for the Yukawa coupling constants within the NMSSM are presented. In addition, the possibility of unifying the Yukawa coupling constants for the b quark and the τ lepton at the scale M _X is discussed.     

Phosphorescence spectra of acenaphthene,diphenyl, and carbazole

These spectra are for liquid-nitrogen temperature, the solvents being n-pentane, n-hexane, n-heptane, and n-octane. Each has a vibrational structure, the vibrational frequencies being independent of the solvent. Acenaphthene in pentane and octane gives 12 peaks corresponding to vibrational frequencies of 414, 630, 1152, 1409, and 1604 cm^–1, the last two being the strongest. Diphenyl in pentane and heptane gives gives 21 peaks; the strongest vibrations are 1610 and 1275 cm^–1, others being 1003, 320, and 735 cm^–1. Carbazole in pentane and hexane gives 15 peaks that fit the frequencies 750, 852, 1141, 1305, 1477, and 1605 cm^–1, the first and last being the strongest.     

Iron carbonyl complexes containing an azomethylene moiety III. Mass-spectrometric study of diiron hexacarbonyl complexes from azomethynes and azines

The electron impact mass spectra of diironhexacarbonyl complexes prepared from benzylidene- and α-naphthylidene-anilines, benzalazine and ketazines of acetophenone, p-bromoacetophenone and benzophenone are studied. The main fragmentation of the ligands occurs only after complete decarbonylation of the molecular ions and involves rupture of metal-ligand bonds, elimination of a part of the central ligand in the form of HCN and RCN, elimination of a neutral aromatic fragment or elimination of a part of the ligand.     

Ceramic membranes modified with catalytic oxide films as ensembles of catalytic nanoreactors

Hybrid catalytic membrane systems have been produced by modifying porous ceramic membranes with metal oxide films. A two-layer cermet membrane consisting of a flexible stainless steel layer and an overlying porous TiO₂ ceramic layer and a ceramic titanium carbide membrane are examined. The membrane surfaces have been modified by the alkoxide method using colloidal organic solutions of metal complex precursors. Producing a tetragonal single-phase ZrO₂/Y₂O₃ coating on the cermet surface increases the abrasion strength of the ceramic layer. CO oxidation and the oxidative conversion of methane into synthesis gas and light hydrocarbons can be markedly intensified by modifying the membrane channels with Cu_0.03Ti_0.97O_2±δ and La + Ce/MgO catalysts, respectively. A method has been developed for depositing, onto the geometrical surface of a membrane, a film of the new single-phase oxide P_0.03Ti_0.97O_2±δ with an anatase structure and uniform pores of mean diameter 〈d〉 ～ 2 nm. Blocks of zeolite-like silicalite can be formed on the surface of the phosphorus-titanium oxide film. The resulting hybrid membrane is characterized by an anisotropic permeability depending on the flow direction. This property has an effect on conversion and selectivity in the nonoxidative dehydrogenation of methanol.     

Vacuum phase transition at nonzero baryon density

It is argued that the dominant contribution to the interaction of quark–gluon plasma at moderate T?Tc$T?T_c$ is given by the nonperturbative vacuum field correlators. Basing on that nonperturbative equation of state of quark–gluon plasma is computed and in the lowest approximation expressed in terms of absolute values of Polyakov lines for quarks and gluons Lfund(T),Ladj(T)=(Lfund)^9/4$L_{\mathrm{fund}}(T),L_{\mathrm{adj}}(T)={(L_{\mathrm{fund}})}^{9/4}$ known from lattice and analytic calculations. Phase transition at any μ   is described as a transition due to vanishing of one of correlators, DE(x)$D^E(x)$, which implies the change of gluonic condensate ΔG₂$\mathrm{\Delta }{G}_2$. Resulting transition temperature Tc(μ)$T_c(\mu )$ is calculated in terms of ΔG₂$\mathrm{\Delta }{G}_2$ and Lfund(Tc)$L_{\mathrm{fund}}(T_c)$. The phase curve Tc(μ)$T_c(\mu )$ is in a good agreement with lattice data. In particular Tc(0)=0.27$T_c(0)=0.27$; 0.19; 0.17 GeV$0.17\text{ GeV}$ for nf=0,2,3$n_f=0,2,3$ and fixed ΔG₂=0.0035 GeV⁴$\mathrm{\Delta }{G}_2=0.0035{\text{ GeV}}^4$.