Catalytic synthesis of pyrazine, piperazine, and 1,4-diaza[2,2,2]-bicyclooctane

A study is made of the deamination of diethylenetriamine over acidalkali catalysts, i. e., kaolin and alumina with promoters. Promoters which raise the acidity of the catalyst, affect the formation of triethylene diamine favorably. Increasing the amount of additive increases the amount of triethylenediamine, and cuts the optimum temperature at which it is formed. On kaolin or Al₂O₃+15% B₂O₃, the yield of triethylenediamine amounts to 30% theory. Addition of MoO₃ facilitates dehydrodeamination and hydrogenolysis of the diethylenetriamine. The optimum promoter for preparing pyrazine is MoO₃ along with a small amount of acid oxides. On the Al₂O₃+5% MoO₃+1% P₂O₅, the pyrazine yield is 27.5% theory. Triethylenediamine can be separated from mixtures of it with piperazine by azeotropic distillation with mxylene or a mixture of mesitylene and -memylnaphthalene.     

Enantioselective properties of asymmetric supported Ni and Ni-Co catalysts in the hydrogenation reaction of ethyl acetoacetate

The influence of the metal content on the support, the conditions of the preparation of the catalysts, and the reaction conditions on the enantioselectivity of the liquid-phase hydrogenation reaction of ethyl acetoacetate in the presence of Ni and Ni-Co catalysts supported on Al₂O₃ and SiO₂, and modified by RR(+)-tartaric acid, was investigated. The maximal optical yield (66–76%) was obtained for the 20% Ni/Al₂O₃ catalyst.     

Nonoxidative conversion of methane and <Emphasis Type="Italic">n</Emphasis>-pentane over a platinum/alumina catalyst

Methane adsorption on the Pt–H/Al₂O₃ and Pt/Al₂O₃ catalysts begins at Т = 475°C and is accompanied by the appearance of hydrogen in the reaction medium. At a higher temperature is raised to 550°C, the amount of adsorbed hydrogen increases to 1.1 and 0.8 mol/(mol Pt), respectively. According to the calculated degree of methane dehydrogenation on platinum sites at Т = 550°C, the Н/C ratio is 1.3 (at/at) for the Pt–H/Al₂O₃ catalyst and 1.5 (at/at) for the Pt/Al₂O₃ catalyst. The introduction of n-pentane into the reaction medium increases the yield of aromatic hydrocarbons (benzene and toluene) by a factor of 8.8 over the arene yield observed in individual n-pentane conversion. A mass spectrometric analysis of the arenes obtained with the Pt/Al₂O₃ catalyst has demonstrated that 37.5% of the adsorbed methane is involved in the methane–n-pentane coaromatization yielding benzene and toluene.     

Untersuchungen im System Al3+?WO42−?H2O?H3O+

Investigations in the System Al³⁺? WO₄^2?? H₂O? H₃O⁺ The composition of the tungstoaluminate anion [AlW₁₂O₄₀]^5? was determined by means of the molar ratio and JOB 's method of continuous variations modified by us. The optimum conditions for the complex formation in the system Al³⁺? WO₄^2?? H₂O? H₃O⁺ were determined: 1.33 ≤ acid degree Z ≤ 2.5; 105°C; 2–6h (c = 7.15 · 10^?2–6 · 10^?3 moles · l^?1). The complex formation in dependence on the acid degree Z is complete at Z = 16 H₃O⁺/12 WO₄^2? = 1.33.     

Elucidation of sulfur mobility on Cr, Mo and W-based catalysts in hydrodesulfurization using a35S pulse tracer method

In hydrodesulfurization of radioactive³⁵S-labeled dibenzothiophene catalyzed by CrO₃/Al₂O₃, it was found that sulfur on sulfided CrO₃/Al₂O₃ was more labile than those on MoO₃/Al₂O₃ and WO₃/Al₂O₃, while the amount of sulfur was less than that on MoO₃/Al₂O₃. Dedicated to Professor Pál Tétényi on the occasion of his 70th birthday     

Conversion of ethanol into linear primary alcohols on gold,nickel, and gold–nickel catalysts

The direct conversion of ethanol into the linear primary alcohols C _n H_2n+1OH (n = 4, 6, and 8) in the presence of the original mono- and bimetallic catalysts Au/Al₂O₃, Ni/Al₂O₃, and Au–Ni/Al₂O₃ was studied. It was established that the rate and selectivity of the reaction performed under the conditions of a supercritical state of ethanol sharply increased in the presence of Au–Ni/Al₂O₃. The yield of target products on the bimetallic catalyst was higher by a factor of 2–3 than that reached on the monometallic analogs. Differences in the catalytic behaviors of the Au, Ni, and Au–Ni systems were discussed with consideration for their structure peculiarities and reaction mechanisms.     

The application of differential thermal analysis technique to the study of single,binary and ternary oxide catalyst systems

The authors have reviewed the salient features of the thermal behavior of the following systems:

1. Single oxide systems: (i) Cr₂O₃, (ii) Fe₂O₃, (iii) Al₂O₃, (iv) MnO₂, (v) ZrO₂, (vi) NiO, (vii) ZnO, (viii) TiO₂, (ix) SiO₂, (x) ThO₂.
2. Binary oxide systems: (i) Cr₂O₃-Al₂O₃, (ii) Cr₂O₃-Fe₂O₃, (iii) Cr₂O₃-ZnO, (iv) Al₂O₃-SiO₂, (v) Al₂O₃-Fe₂O₃, (vi) MnO-Cr₂O₃, (vii) Cu-Al₂O₃, (viii) ZrO₂-Cr₂O₃, (ix) NiO-Cr₂O₃, (x) ZrO₂-NiO, (xi) ThO₂-Al₂O₃.
3. Ternary oxide systems: (i) NiO-Cr₂O₃-ZrO₂, (ii) Fe₂O₃-Cr₂O₃-Al₂O₃.
4. Vanadates: (i) tin vanadate, (ii) copper vanadate, (iii) lead vanadate, (iv) cobalt vanadate and (v) silver vanadate.

Excellent correlations have been obtained in most of the systems between the thermal characteristics of the solids, as revealed by DTA, and their specific surface areas and catalytic activity.     

Isothermal gravimetry and magnetic properties of CoOMoO3γAl2O3 catalysts

Isothermal gravimetry and magnetic susceptibility of MoO₃, MoAl₂O₃, CoAl₂O₃ and CoMoAl₂O₃ with/without Na⁺ ions have been studied in order to investigate the reducibility of the systems in H₂ H₂—hydrocarbons and H₂—hydro-carbon—thiophene. These studies have evidenced the formation of metallic cobalt during reduction of cobalt—moly catalysts containing Na⁺ ions in the Al₂O₃ support. This metallic cobalt accelerates the reduction of supported MoO₃. However, in the absence of sodium, cobalt exerts an inhibitory influence on the reduction of MoAl₂O₃. The inhibition is caused mainly due to retention of the water evolved during the process by well-dispersed Co²⁺ ions which are incapable of undergoing reduction. The presence of sulfur also kelps in suppressing the reduction to cobalt metal.     

Solid-State Equilibria in the MoO3 – TeO2 – Al2O3 System

The binary and ternary equilibrium reactions of Al₂O₃ with TeO₂ and MoO₃ were studied by X-ray diffraction methods and the following compatibility ranges were determined in the TeO₂ – MoO₃ – Al₂O₃ system at 750°C in air: TeO₂, Te₂MoO₇, Al₂TeO₆; Te₂MoO₇, MoO₃, Al₂TeO₆; MoO₃, Al₂(MoO₄)₃, Al₂TeO₆; Al₂(MoO₄)₃, Al₂O₃, Al₂TeO₆. Ternary compound formation was not observed in the temperature range investigated (450—750°C). Phasengleichgewichte im System MoO₃—TeO₂—Al₂O₃ .     

Hydrogenolysis of dimethyl disulfide in the presence of bimetallic sulfide catalysts

The hydrogenolysis of dimethyl disulfide in the presence of Ni,Mo and Co,Mo bimetallic sulfide catalysts was studied at atmospheric pressure and T = 160–400°C. At T ≤ 200°C, dimethyl disulfide undergoes hydrogenolysis at the S-S bond, yielding methanethiol in 95–100% yield. The selectivity of the reaction decreases with increasing residence time and temperature due to methanethiol undergoing condensation to dimethyl disulfide and hydrogenolysis at the C-S bond to yield methane and hydrogen sulfide. The specific activity of the Co,Mo/Al₂O₃ catalyst in hydrogenolysis at the S-S and C-S bonds is equal to or lower than the total activity of the monometallic catalysts. The Ni,Mo/Al₂O₃ catalyst is twice as active as the Ni/Al₂O₃ + Mo/Al₂O₃ or the cobalt-molybdenum bimetallic catalyst.     

Ultradeep Hydrodesulfurization of Dibenzothiophene (DBT) Derivatives over Mo-Sulfide Catalysts Supported on TiO2-Coated Alumina Composite

The present paper reviews in detail the different studies now being conducted by our research team concerning the ultradeep hydrodesulfurization (HDS) of dibenzothiophene (DBT) derivatives over Mo/TiO₂ and Mo/TiO₂–Al₂O₃ catalysts. First, a detailed characterization of Mo/TiO₂ (P-25 Degussa, 50 m²/g) catalysts prepared by equilibrium adsorption technique shows that Mo- species are highly and uniformly dispersed on the surface of titania up to 6.6 wt% MoO₃ loading. Above this value, some aggregation of Mo occurs, leading to the formation of bulk MoO₃. Below 6.6 wt% MoO₃ loading, the Raman spectroscopy data of the calcined samples show that the supported Mo-species possess a highly distorted octahedral MoO₆ structure. TiO₂–Al₂O₃ composites were prepared by chemical vapor deposition (CVD) using TiCl₄ as a precursor. Using several characterization techniques, we demonstrated that the support composite presents a high dispersion of TiO₂ over -Al₂O₃ without forming precipitates up to ca. 11 wt% loading. Moreover, the textural properties of the composite support are comparable to those of alumina. Under the present sulfidation conditions (673 K, 5%H₂S/95%H₂), Mo-species supported on TiO₂ are better sulfided than on alumina, as demonstrated using XPS. This can be attributed to the relatively lower interaction between Mo-species and titania. The state of sulfide species supported on the composite support can be considered as a transition state between TiO₂ and Al₂O₃. However, at relatively higher TiO₂ loadings (ca. 11 wt%), Mo/TiO₂–Al₂O₃ catalysts exhibit sulfidability similar to that of Mo/TiO₂. The HDS tests conducted in both the laboratory and in industry show that sulfide catalysts supported on TiO₂–Al₂O₃ (ca. 11 wt% TiO₂) are more active than those supported on TiO₂ or Al₂O₃.     

The influence of the method of addition of Al2O3 to 3YSZ material on its thermal and electrical properties

The properties of tetragonal yttria-stabilized zirconia composites with the small addition of alumina (Al₂O₃?Y₂O₃?ZrO₂ composite) obtained on two ways of synthesis were studied in terms of usability for anode materials in solid oxide fuel cell. Both methods were based on citric synthesis: in the first one, Al₂O₃ was coprecipitated with the tetragonal ZrO₂ in the form of citrate by citric acid, while in the second Al₂O₃ was impregnated in the form of aluminium nitrate precursor on tetragonal ZrO₂ matrix. The obtained materials were analysed by X-ray diffraction, dilatometry and impedance spectroscopy. The results of measurements show that regardless of synthesis method, the addition of Al₂O₃ influences the conductivity of samples by increasing their grain boundaries conductivity as an effect of removing of SiO₂ and decreasing of conductivity activation energy. The impregnation of Al₂O₃ on tetragonal ZrO₂ and sintering of this material above shrinking temperature cause, however, radical decrease of porosity of materials, which disqualifies these samples as anode materials. In the case of samples obtained by coprecipitation the significant decrease of porosity is not observed.     

Preparation of MoO3/g-Al2O3 catalyst by the reaction of a-boehmite with MoO3/H2O slurry - dual role of MoO3 as active phase and texture stabilizer during calcination

Summary Catalyst MoO₃/g-Al₂O₃ was prepared by the reaction of a-boehmite with molybdic acid in slurry MoO₃/H₂O followed by calcination. The deposited MoO₃ functioned as thermal stabilizer and inhibited sintering of Al₂O₃ phase during calcination. After calcination at 550 and 650^oC the surface area of Al₂O₃ obtained from a-boehmite was 207 and 172 m² g^-1, respectively, and of MoO₃/Al₂O₃ obtained from MoO₃/a-boehmite was 323 and 285 m² g^-1, respectively. On the other hand, molybdic acid did not work as peptization agent and the mechanical strength of MoO₃/Al₂O₃ was not higher than of Al₂O₃. The catalyst was sulfided and its activity in thiophene hydrodesulfurization was tested; it exhibited about the same activity as reference industrial MoO₃/Al₂O₃ catalyst.     

Li3Al(MoO4)3, a lyonsite molybdate

Trilithium aluminium trimolybdate(VI), Li₃Al(MoO₄)₃, has been grown as single crystals from α‐Al₂O₃ and MoO₃ in an Li₂MoO₄ flux at 998 K. This compound is an example of the well known lyonsite structure type, the general formula of which can be written as A₁₆B₁₂O₄₈. Because this structure can accomodate cationic mixing as well as cationic vacancies, a wide range of chemical compositions can adopt this structure type. This has led to instances in the literature where membership in the lyonsite family has been overlooked when assigning the structure type to novel compounds. In the title compound, there are two octahedral sites with substitutional disorder between Li⁺ and Al³⁺, as well as a trigonal prismatic site fully occupied by Li⁺. The (Li,Al)O₆ octahedra and LiO₆ trigonal prisms are linked to form hexagonal tunnels along the [100] axis. These polyhedra are connected by isolated MoO₄ tetrahedra. Infinite chains of face‐sharing (Li,Al)O₆ octahedra extend through the centers of the tunnels. A mixed Li/Al site, an Li, an Mo, and two O atoms are located on mirror planes.     

Phase formation in the Ag<Subscript>2</Subscript>MoO<Subscript>4</Subscript>-MgMoO<Subscript>4</Subscript>-Al<Subscript>2</Subscript>(MoO<Subscript>4</Subscript>)<Subscript>3</Subscript> system

The subsolidus region of the Ag₂MoO₄-MgMoO₄-Al₂(MoO₄)₃ ternary salt system has been studied by X-ray phase analysis. The formation of new compounds Ag_{1 ? x} Mg_{1 ? x} Al_{1 + x} (MoO₄)₃ (0 ≤ x ≤ 0.4) and AgMg₃Al(MoO₄)₅ has been determined. The Ag_{1 ? x} Mg_{1 ? x} Al_{1 + x} (MoO₄)₃ variable-composition phase is related to the NASICON type structure (space group R \(\bar 3\) c). AgMg₃Al(MoO₄)₅ is isostructural to sodium magnesium indium molybdate of the same formula unit and crystallizes in triclinic system (space group P \(\bar 1\), Z = 2) with the following unit cell parameters: a = 9.295(7) Å, b = 17.619(2) Å, c = 6.8570(7) Å, α = 87.420(9)°, β = 101.109(9)°, γ = 91.847(9)°. The compounds Ag_{1 ? x} Mg_{1 ? x} Al_{1 + x} (MoO₄)₃ and AgMg₃Al(MoO₄)₅ are thermally stable up to 790 and 820°C, respectively.     

Effect of Mo content in MoO3/g-Al2O3 on the catalytic activity for transesterification of dimethyl oxalate with phenol

The influence of molybdenum content on the catalytic performance in the transesterification of dimethyl oxalate (DMO) with phenol to methyl phenyl oxalate (MPO) and diphenyl oxalate (DPO) was investigated. The results indicated that the MoO₃/Al₂O₃ catalyst with 14 wt% Mo content gave maximal DPO yield with 6.1% and 75.1% DMO conversion. The component, structure and phase of MoO₃/Al₂O₃ catalysts were characterized by means of X-ray diffraction (XRD), BET specific surface area, temperature-programmed desorption of ammonia (NH₃-TPD), and FTIR analysis of adsorbed pyridine. This revised version was published online in June 2006 with corrections to the Cover Date.     

Adhesion of small particles of palladium on Al2O3

The adhesion of small particles of palladium prepared by thermal evaporation onto a substrate of Al₂O₃ was studied. Al₂O₃ was obtained by oxidation of a pollycristalline aluminum strip. The deposit of palladium was observed by Transmission Electron Microscopy which allowed to determine the size and the density of particles according to the average deposition thickness. The adhesion of particles was determined by two methods: the study of particle number density, and the study of the particle shapes.     

Gas-phase conversion of the U(VI), Sr,Mo, and Zr compounds in nitrating atmosphere

The gas-phase conversion of U₃O₈, MoO₃, SrO, and their mechanical mixtures, and also of ZrO₂ into water-soluble compounds in the atmosphere of (NO _x  + vapor H₂O) or HNO₃ (vapor) was studied. In the course of gas-phase conversion, U₃O₈ and SrO transform into water-soluble compounds (nitrates, hydroxonitrates), whereas MoO₃ and ZrO₂ undergo no changes. The principal possibility of separating U from Mo and Zr by gas-phase conversion of the oxides in the atmosphere of (NO _x  + vapor H₂O) or HNO₃ (vapor) was demonstrated.     

Preparation and Characterization of Molybdenum Oxide Thin Films by Sol-Gel Process

This paper presents a new sol-gel process to prepare molybdenum oxide thin films. A molybdenum acetylacetonate sol was prepared by employing the system CH₃COCH₂COCH₃/MoO₃/C₆H₅CH₃/HOCH₂CH₂OCH₃. A molybdenum acetylacetonate gel was prepared by addition of aqueous NH₃. Thermal gravimetry (TG) and differential thermal analyses (DTA) of the gel suggested that crystallization of MoO₃ occurs in a 140 K temperature range around 508°C. MoO₃ films were prepared on fused silica, Si (111) and Al₂O₃ (012) substrates by annealing spin coating films of the sol in oxygen environment at 508°C. X-ray diffraction (XRD) showed that all films crystallize in -MoO₃ structure, and crystallites on fused silica substrate are arbitrarily oriented while those on Si (111) and Al₂O₃(012) substrates oriented in the (010) direction. SEM investigations showed that MoO₃ grains of all films are randomly distributed, with a longitudinal dimension of about 1–5 m and the film thickness is about 1 m.     

Oxidative ammonolysis of 3-picoline on mixed oxide catalysts

The oxidative ammonolysis of 3-picoline has been studied on the following catalysts: V₂O₅ on corundum, V₂O₅ with the addition of 1% of H₂WO₄ on corundum, V₂O₅ + MoO₃ + P₂O₅ (10.350.35) on silica gel, V₂O₅ + Al₂O₃, and a melt of V₂O₅ + TiO₂ (10.22). Mixed catalysts of vanadium and titanium oxides exhibited the highest activity and selectivity. With the passage of 25–45 moles of oxygen (in the form of air), 5–10 moles of ammonia, and 50–70 moles of water per mole of 3-picoline at a temperature of 390–410° C, the amount of nicotinonitrile formed on these catalysts amounted to 85–90% of the theoretically possible amount.Part LXIII of the series Oxidation of organic compounds; for part LXII, see [1].