Changes in surface composition of Fe-Si-Cr-K oxide alkylation catalyst: the marked role of potassium ferrites

The influence of gas-phase methylation of phenol on the state of the Fe-Si-Cr-K oxide catalyst surface was investigated by thermodesorption of K atoms and ions. Changes in potassium desorption energies, as determined from Arrhenius-like plots, varied from 3.07 eV to 1.21 eV for the atoms and from 2.59 eV to 2.89 eV for ion desorption from the active and deactivated samples, respectively. The results were discussed in terms of transformation of the catalyst surface and formation of β-ferrite.     

In situ characterization of an iron catalyst by potassium ion desorption and electron emission measurements

The surface conditions of an industrial iron catalyst were monitoredin situ by work function measurements and measurements of thermal desorption of potassium ions. Changes in activation energy for potassium ion desorption and in work function values during catalyst activation and deactivation are discussed in terms of the potassium coverage and chemical composition of the catalyst surface.     

Double quantization of CP type orbits by generalized Verma modules

It is known that symmetric orbits in g^* for any simple Lie algebra g are equipped with a Poisson pencil generated by the Kirillov-Kostant-Souriau bracket and the reduced Sklyanin bracket associated to the “canonical” R-matrix. We realize quantization of the Poisson pencil CPⁿ type orbits (i.e. orbits in sl(n + 1)^* whose real compact form is CPⁿ) by means of q-deformed Verma modules.     

Effect of constrained donor atom orientations on the stabilities, complexation kinetics, redox potentials, and structures of macrocyclic polythiaether Complexes. Copper(II) complexes with cyclopentanediyl derivatives of [14]aneS4 in 80% methanol

The two ethylene bridges in the macrocyclic tetrathiaether 1,4,8,11-tetrathiacyclotetradecane ([14]aneS(4)) have been systematically replaced by cis- or trans-1,2-cyclopentane to generate a series of new ligands that exhibit differing preferences for the orientation of the sulfur donor atoms while maintaining constant inductive effects. The resulting five dicyclopentanediyl derivatives, along with two previously synthesized monocyclopentanediyl analogues, have been complexed with Cu(II), and their stability constants, formation and dissociation rate constants, and redox potentials have been determined in 80% methanol/20% water (by weight). The crystal structures of the Cu(II) complexes with the five dicyclopentanediyl-[14]aneS(4) diastereomers as well as the structures for a representative Cu(I) complex and one of the free ligands have also been determined. The properties of these complexes are compared to previous data obtained for the corresponding cyclohexanediyl derivatives in an attempt to shed additional light on the influence of sterically constraining substituents upon the properties of macrocyclic ligand complexes.     

In situ monitoring of bare and K-doped Mo2C catalysts surface depassivation based on emission of electrons and K ions

The method for in situ characterization of surface transformations on heterogeneous catalyst is described. The method is based on the measurements of thermal electron and ion emissions from the catalyst surface. It is demonstrated by investigating the depassivation process of undoped and K-doped Mo₂C catalysts exposed to air after synthesis and use to identify characteristic steps of reduction-carburization by flowing CH₄/H₂ gas mixture. The information obtained from thermal emission experiments is consistent with the methane consumption profile, which provided an independent observation of the recarburization step.     

The modifications of copper work function by layer-by-layer deposition of [W(CN)8] – Co bimetallic nanolayers

In the reaction of K₄[W(CN)₈] · 2H₂O and Co²⁺(aq) cations on the polycrystalline or monocrystalline [3 1 1] copper using layer-by-layer deposition, a thin film of the coordination polymer {[{Co(H₂O)₂(μ-CN)₄}₂W] · 4H₂O}_n was formed. The work function of copper and deposited on it bi-layers depended on a number of layers and the concentrations of the deposited precursors. At high complex concentrations work function reached the plateau after several deposition processes, while at low concentrations oscillations in the work function were observed when K⁺ or Co²⁺ cations were present in the outside layer. The changes of the work function were also dependent on Co²⁺ salt used (CoCl₂ · 6H₂O or Co(NO₃)₂ · 6H₂O). This was interpreted in terms of a layer structure resulting from various coordination of external anions to cobalt cations.