Influence of the composition of perovskites based on SrMnO<Subscript>3</Subscript> on their catalytic properties in the oxidative coupling of methane

The oxidative coupling of methane (OCM) in a periodic regime over the SrMnO₃ and its derivatives has been investigated. It has been established that partial replacement of the strontium ion by alkali metal ions leads to an increase in both catalytic activity and in selectivity with respect to higher hydrocarbons. Comparison of the results obtained in the present work with those obtained earlier for catalysts based on SrCoO₃ led to the conclusion that the Co-containing catalysts were preferable to the Mn-containing catalysts for carrying out oxidative coupling of methane in a periodic regime.__________Translated from Teoreticheskaya i Éksperimentalnaya Khimiya, Vol. 41, No. 1, pp. 30–34, January–February, 2005.     

Synthesis of heliannuol D, an allelochemical from Helianthus annus

A synthesis of heliannuol D 1 is described involving regioselective oxidation of the benzoxabicyclo[3.2.1]octanone 20 followed by hydrogenolysis to generate the benzoxepane ring system of 1.     

CO2氧化异丁烷制异丁烯用Pd/V2O5-SiO2催化剂

 利用表面化学反应改性法制备了不同V2O5负载量的V2O5-SiO2表面复合物载体,进而采用等体积浸渍法制备了负载型Pd催化剂. 用N2吸附、 X射线衍射、透射电镜、 X射线光电子能谱、程序升温脱附、化学吸附-红外光谱和微反技术对系列Pd/V2O5-SiO2催化剂的比表面积、晶相结构、价态、异丁烷的化学吸附性能和CO2部分氧化异丁烷制异丁烯的催化性能进行了研究. 结果表明, Pd/V2O5-SiO2催化剂中的钒以V5+形式存在, V5+在催化剂表面形成活性位V=O, 其中 V=O 晶格氧与 i-C4H10分子的-CH3 和-CH 中的H产生化学吸附作用; 催化剂中金属Pd与V4+协同作用使CO2在催化剂上产生了卧式吸附态; 晶格氧参加了催化氧化反应,催化剂中 V5+←→V4+ 的变化构成了催化反应的氧化还原过程. 在525 ℃, CO2/i-C4H10体积比为1和空速为 1200 h-1的条件下,以Pd/25%V2O5-SiO2为催化剂时异丁烷转化率为22.8%, 异丁烯选择性为89.1%.     

Dehydrogenation of isobutane in the presence of carbon dioxide over supported vanadium oxide catalysts

Summary The dehydrogenation of isobutane to isobutene in the presence of carbon dioxide was carried out over supported vanadium oxide catalysts. The influence of the support on the catalytic performance was investigated. The isobutane conversion and isobutene selectivity in the presence of carbon dioxide were compared with the results obtained during the dehydrogenation reaction in the presence of helium (inert gas). The catalysts were characterized by temperature-programmed techniques (TPR, TPD-NH₃, TPD-CO₂).     

Oxidative Coupling in a Series of Derivatives of 4a,9-Diaza-1,2,4a,9a-tetrahydrofluorene. 6. Reactions with Substituted 2-Aminoethanols

Oxidative coupling of derivatives of 4a,9-diaza-1,2,4a,9a-tetrahydro-9H-fluorene with 2-ethyl-, 2,2-dimethyl-, and 2-hydroxymethyl-2-methylaminoethanol in the presence of MnO₂ led to the selective formation of the corresponding mono- and di(hydroxymethyl)quinonediimines, subsequent cyclization of which gave the products of 6,7-annelation. Coupling with 2,2-di(hydroxymethyl)aminoethanol gave the annelation products directly.     

Carbocyclic and nitrogen-containing fused CH-acids with an annelated indenyl fragment. Thermogravimetric and X-ray structural analysis of 6H-indeno[1,2-b]quinoline

Based on thermogravimetric characteristics first obtained for the model 6H-indeno [1,2-b]quinoline, the scheme of thermal conversions of this compound in the temperature range 20–700 °C has been proposed, and the limit of its thermal stability (300 °C) has been determined. This temperature is recommended as the optimum for synthesizing fused benzoaza(diaza)fluorenes. Based on the results of X-ray structural analysis, the molecules of the studied indenoquinoline form centrosymmetric pairs, which are arranged in (110) layers. The molecules are orientationally disordered. The observed self-association of these molecules is similar to the - association of fused heterocyclic systems with-excessive and ****- deficient fragments. It has been suggested that interferon-inducing and antitumor compounds with an annelated indenyl fragment have a common mechanism of action according to the intercalation model of stacking structures.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 703–709, April, 1995.     

Spectrophotometric methods for the determination of labetalol hydrochloride in pure and dosage forms

Simple and sensitive Spectrophotometric methods for the determination of labetalol hydrochloride are described. The first two are based on the oxidative coupling reaction of labetalol hydrochloride withp-N,N-dimethyl-phenylenediamine dihydrochloride (method A, _max 685 nm) and 3-methyl-2-benzothiazolinone hydrazone hydrochloride (method B, _max 545 nm) in the presence of sodium hypochlorite and eerie ammonium sulphate as oxidants, respectively. The third depends on the formation of an ion-association complex of labetalol hydrochloride with suprachen violet 3B at pH 1.3, which is extracted into chloroform (method C, _max 565 nm). The methods obey Beer's law and the precision and accuracy of the methods were checked against the B.P. reference method and the relative standard deviations were in the range 0.35–0.52%. These methods are applied to the determination of labetalol in dosage forms.     

The properties of supported rhenium catalysts in the dehydrogenation of cyclohexane

The 2 % Re/sibunite catalyst is more active than 2 % Re/-Al₂O₃ and 2 % Re/-Al₂O₃ catalysts in the dehydrogenation of cyclohexane into benzene (T = 350 °C,w = 0.5 h–1). The substitution of NH₄ReO₄ by HReO₄ in the preparation of the catalyst enhances its activity by a factor of 1.3. Treatment with HNO₃ or oxalic acid increases the selectivity by a factor of 1.2 and 1.35, respectively, the overall conversion of cyclohexane being 32–40 %.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 2119–2121, August, 1996.     

K2O对Pt—Sn／Al2O3催化剂表面酸性及MCH脱氢稳定性的影响

利用吡啶吸附－ＩＲ，ＮＨ３吸附－脱附，原位热重积炭，ＤＳＣ等技术并结合甲基环己烷（ＭＣＨ）脱氢活性试验，研究了Ｋ２Ｏ对工业Ｐｔ－Ｓｎ／Ａｌ２Ｏ３催化剂的表面酸性及ＭＣＨ脱氢稳定性的影响，结果表明，Ｋ２Ｏ能有效地调变催化剂的表面酸性，降低其表面酸中心特别是强酸中心的数目；ＭＣＨ脱氢反应的积炭量随Ｋ２Ｏ含量的增加而减少，但催化剂的高温脱氢稳定性与Ｋ２Ｏ含量并不完全呈顺变关系，Ｋ２Ｏ含量应严格控制，当Ｋ     

Miscible blends through hydrogen bonding: effects on polymer properties

Miscible blends through hydrogen bonding have been intensively studied. The effects of a variety of miscible hydrogen bonded polymer blends on properties such as thermal and thermal oxidative stability, moisture sensitivity, modulus and glass transition temperature are discussed. In addition, the preparation of semi-interpenetrating polymer networks (IPNs) and studies of the effect of crosslinking on the miscibility in hydrogen bonded polymer blends are reviewed.