UV spectra of vinyl chalcogenides: Correlation with the photoelectron spectra

The electron absorption spectra of alkylvinyl chalcogenides (CH₂=CHEAlk, E = S, Se, Te) were analyzed with consideration of the photoelectron spectroscopic data. The following sequence of electronic transitions was found in their UV spectra:

EPR and magnetic studies on the regeneration of cobalt-molybdenum catalysts for coal liquefaction

Changes in composition and structure occurring in cobalt promoted and unpromoted Mo/Al₂O₃ catalysts during several subsequent cycles of activation and regeneration have been studied. Regeneration does not lead to the initial oxide form of the catalysts completely. The changes in the oxide catalyst composition increase with increasing number of activation-regeneration cycles.

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, Mo/Al₂O₃ . . -.

     

The catalytic activity of Ni?V oxide catalysts

The activity and selectivity of Ni–V oxide catalysts in relation to the phase composition were investigated. The catalytic activity was measured in the oxidative dehydrogenation of methanol to formaldehyde and in the oxidation of SO₂ to SO₃.The oxide with the atom ratio gives the highest yield of formaldehyde and the slowest rate of SO₂ oxidation. The above phase, as shown by X-ray and IR measurements, has a specific structure characterized by a weakened V=O double bond.

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Ni–V . SO₂ SO₃. SO₂. , , , V=O

     

Solid aluminiumalkyl-based isomerization catalysts. Surface acidity and catalytic activity

Isomerization catalysts with high activity and selectivity were prepared by chemical anchoring of aluminiumethyldichloride on the surface of inorganic oxides. Surface acidity was studied by calorimetric and IR spectroscopy methods, and was found to correspond well with catalytic activity for m-xylene isomerization.

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Ir spectra of catalysts and adsorbed molecules. 37 The pentasil-aluminum oxide catalytic composite

For previous communication, see [1].     

Lewis-type catalytic activity of direct incorporated Zr- and Sn-SBA-16 catalysts

Metal incorporation into nanoporous materials could give Lewis acid sites through the framework substitution of silica matrix, which are supposed to be in tetrahedral substitution of silica. In this work, Zr- and Sn-incorporated SBA-16 were directly synthesized by the microwave synthesis method. These microwave synthesized Zr- and Sn-incorporated mesoporous silica materials were applied in activation of ketones by Lewis acid sites to catalyze Meerwein-Ponndorf-Verly reduction of cyclohexanone and Baeyer-Villiger oxidation of adamantanone, respectively. Optimum incorporated Zr- and Sn-species gave almost 100% selectivity with high activity onto corresponding alcohol and lactone, respectively.     

Synthesis of siloxy-modified second generation Hoveyda-Grubbs catalysts and their catalytic activity

Efficient syntheses of the first ruthenium alkylidene complexes bearing siloxide ligands are described. Second generation Hoveyda-Grubbs catalyst is shown to undergo efficient functionalization with a number of potassium silanolates to give disiloxy derivatives. The complexes obtained are found catalytically active in selected metathesis transformations.     

Correlation between phase composition and activity of complex oxide catalysts

Correlation between the catalytic activity in oxidation of carbonaceous materials and a change in the phase composition of the La_1?x Cs _x VO_4±y and Ce_1?x Pr _x O_2?d catalysts was studied. The activity values obtained by iso- and polythermal methods are close.     

Correlation between oxygen binding energy and catalytic activity of oxides

Oxygen binding energy is suggested as a measure for the ability of oxide cations to enter into weak chemical interactions with reactant molecules, which is a necessary prorequisite for the adsorbability and catalytic activity of oxides.

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负载金催化剂上CO氧化反应活性与金属氧化物载体中金属-氧结合能之间的关系

讨论了金属氧化物载体(MOx)对其负载纳米金催化剂(Au/MOx)上CO氧化反应的影响。采用典型的共沉淀法和沉积-沉淀法在完全相同的焙烧条件下制备了一系列MOx负载金催化剂,以CO氧化转化50%时的反应温度(T1/2)定量评价了MOx载体和Au/MOx催化剂的催化活性。进一步将MOx载体与相应Au/MOx催化剂的T1/2值之差对MOx载体的金属-氧结合能做曲线进行关联,发现二者呈明显的火山型关系。这一结果表明,采用具有适当金属-氧结合能(300–500 atom O)的MOx可大大提高沉积于其上的Au纳米颗粒的催化活性。     

Bi-Mo-Nb复合氧化物的结构与对丙烯氧化的催化活性

本文用XRD, IR, Raman, SEM和ESR等方法研究了系列氧化物Bi~2Mo~3-3XNb~2xO~12-4X(X=0.00, 0.02, 0.05, 0.10, 0.15, 0.20, 0.25) 的结构和对丙烯氧化的催化活性。结果表明, 在X<0.25范围内, 催化剂基本保持典型的α-Bi~2Mo~3O~12结构, 少量Nb^5+的掺杂, 可取代晶格中的Mo^6+, 产生氧空位,无序分布的氧空位的浓度先随X值的增加而增加, 当X=0.15时达到最大值, 催化剂对丙烯氧化的催化活性与这种氧空位的浓度成正比, 反应遵循Redox机理。     

Preparation and catalytic activity for ammonia synthesis of several ruthenium supported catalysts

Ruthenium supported catalysts were prepared from RuCl₃ · 3H₂O and K₄[Ru(CN)₆] · 3 H₂O solutions, upon several acid/base pretreated γ-Al₂O₃ samples, using water and acetone as solvents. Metallic adsorption was found to be dependent on solvent and precursor used. An increasing final ruthenium content of the catalysts with increasing acid site content of the support is observed, when K₄[Ru(CN)₆] · 3 H₂ is used as a precursor. The catalytic activity was followed at atmospheric pressure and 593 K (N₂/H₂ = 1/3). Catalysts prepared from K₄[Ru(CN)₆] · 3 H₂O were about ten fold more active than those prepared from RuCl₃ · 3 H₂O. The catalytic activity of catalysts prepared from K₄[Ru(CN)₆] · 3 H₂O was found to be sensitive to the acid-pretreatment of γ-Al₂O₃, while the activity of those prepared from RuCl₃ · 3 H₂O was not sensitive to the pretreatment of the support.     

Acidity and catalytic activity of polyfunctional zeolite catalysts in the benzene-propene-diisopropylbenzene system

Studies on the effect of the acidity of polyfunctional zeolite catalysts on their activity in benzene alkylation by propene and its transalkylation by diisopropylbenzene (DIPB) have revealed that alkylation and transalkylation of aromatics proceed on catalytic centers of different acidity.

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UV spectra of N-vinylpyrroles

Chemistry of Heterocyclic Compounds - The effect of the structure and the medium on the position and intensity of the absorption bands in the UV spectra that attest to the presence of a single...     

Conversion of synthesis gas into alcohols on supported cobalt-molybdenum sulfide catalysts promoted with potassium

The use of transition metal sulfides as catalysts for the synthesis of alcohols can solve the problem of catalyst resistance to sulfur. Catalysts based on molybdenum sulfide of different compositions (promoted with Co and K) were synthesized with the use of various supports (aluminum oxide, aluminum oxide modified with silicon oxide, Sibunit, and titanium silicate) and tested in the reactions of alcohol synthesis and the hydrofining of a mixture of thiophene with n-1-hexene. The dependence of catalyst activity in the synthesis of alcohols on support pore size was demonstrated. It was found that an increase in the potassium content of the active phase of a catalyst increased its activity in the synthesis of alcohols and decreased it in hydrodesulfurization and hydrogenation reactions. Transmission electron microscopy data made it possible to quantitatively evaluate the effect of a potassium additive on the morphology of the active phase; the hypothesis that potassium was intercalated between the layers of molybdenum sulfide was proposed.     

Correlation between the surface acidity and activity of bismuth tungstate catalysts

The surface acid strength distribution in bismuth tungstate catalysts with Bi/W ratios of 2/3, 1/1, 2/1 and 6/1 has been investigated. The results are interpreted attributing higher acidities to W–O–W bonds and lower acidities to W=O bonds. An apparent correlation is observed between the surface acidities of the catalysts and their activities in the oxidation and ammoxidation of propylene and 1-butene.

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Bi/W, 2/3, 1/1, 2/1 6/1. , W–O–W W=O. 1-.

     

载体效应对Pt催化剂在一甲胺湿式氧化中的催化性能影响研究

采用浸渍法制备了Pt/AC,Pt/ZrO2,Pt/Al2O3催化剂,并研究了其对一甲胺湿式氧化(CWAO)反应的催化性能.结果表明:载体对Pt的催化活性具有十分明显的影响,当Pt负载到活性炭(AC)载体表面时具有最佳的催化活性,其次是氧化锆,而当Pt负载到氧化铝载体表面时,其催化活性最低.一甲胺在Pt/AC,Pt/ZrO2,Pt/Al2O3催化剂表面被矿化所需最低温度分别为200,250和280℃.Pt/AC催化剂优异的催化活性主要归因于Pt与载体间的弱相互作用、活性炭的大比表面积以及载体自身具有一定的催化活性.