Hydrogenation of benzene on sulfide catalysts in the presence of thiophene

The principles of benzene hydrogenation have been studied with sulfide catalysts NI/MS₂, Ni/SiO₂, M/SiO₂ and (Ni, M)/SiO₂ (M=Mo, W) obtained via metal complex precursors or by impregnation. In bimetallic catalysts active sites of benzene hydrogenation are formed upon reduction of the active component for thiophene hydrogenolysis.

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Ni/MS₂, Ni/SiO₂, M/SiO₂, (Ni,M)/SiO₂, M=Mo W, , . , .

     

Activity of catalysts in thiophene synthesis from furan and hydrogen sulfide

Thiophene synthesis from furan and H₂S over acid catalysts is reported. Proton donor catalysts are low-active, nonselective, and prone to deactivation. Alumina-supported catalysts having Lewis acid sites, such as alumina-supported catalysts, are more efficient. With these catalysts, the thiophene formation rate per Lewis acid site increases with increasing site strength. It is assumed that the reaction proceeds via the formation of a surface intermediate consisting of an acid site bonded to an α carbon atom of the furan ring and an H₂S molecule nondissociatively adsorbed on a basic site. At atmospheric pressure, T = 250–450°C, initial furan concentrations of 1–20 vol %, and H₂S/furan = 0.4–20 (mol/mol), the thiophene formation reaction is first-order with respect to both reactants and its rate constant increases with increasing temperature. The thiophene formation rate depends on the H₂S/furan molar ratio. Under optimal conditions, the thiophene yield is 95–98 mol % and the thiophene formation rate is high.     

One-step synthesis of 3-dichloromethylpyridine from pyridine in the presence of iron-containing catalysts

3-Dichloromethylpyridine was synthesized by reaction of pyridine with the system MeOH-CCl₄-iron catalyst [FeBr₂, Fe₃(CO)₁₂, or iron(III) naphthenate]. Iron(II) bromide at a FeBr₂-pyridine-CCl₄-MeOH ratio of 1:100:200:200 showed the highest catalytic activity.     

Enhanced radiation crosslinking of carboxymethylated chitosan in the presence of acids or polyfunctional monomers

Carboxymethylated chitosan (CMCt) hydrogels were synthesized by γ-ray radiation-induced crosslinking in the presence of acids or polyfunctional monomers. Compared with that of CMCt hydrogels synthesized without additives, the gel fraction was improved and the gelation dose was decreased obviously after incorporating acids or polyfunctional monomers into CMCt hydrogels. The diffusion behavior of water in the CMCt gels prepared at different conditions was Fickian diffusion, and the swelling of the CMCt gels displayed characteristic pH sensitivity, which was analyzed by fluorescence molecular probes. Preliminary mechanism of radiation-induced crosslinking of CMCt in the presence of acids or polyfunctional monomers was discussed based on the FTIR and sol-gel analysis. Furthermore, it was found that CMCt hydrogels were hydrodegradable with high temperature (>60 °C), and incorporating polyfunctional monomers into the CMCt hydrogels also could improve the thermal stability of the CMCt hydrogels obviously.     

Effect of support on the synergy in HDS of thiophene and HDN of pyridine over Mo sulfide catalysts promoted by Rh

The effect of support (SiO₂-Al₂O₃, Al₂O₃,MgO) of the Rh-Mo(S) sulfide catalysts on the synergy in hydrodesulfurization (HDS) of thiophene and hydrodenitrogenation (HDN) of pyridine was studied. The synergy in HDS was between 7–10 regardless of the kind of support used. The synergy in HDN varied from none over the MgO supported sample to about 3 over SiO₂-Al₂O₃ supported catalyst, in accord with the positive effect of increasing support acidities. This revised version was published online in June 2006 with corrections to the Cover Date.     

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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Competitive free radical 4-nitrophenylation of pyridine and thiophene

Competitive free radical 4-nitrophenylation of pyridine and thiophene shows a relative reactivity of thiophene:pyridine of 1.3:1 as based on product isolation. A three-center reaction is proposed to account for the predominance of alpha substitution in each system. Column chromatography and ¹H nmr are used for separation and identification of products.     

Synthesis of polyfunctional mono- and dipyridines using complex cobalt catalysts

Conclusions Novel polyfunctional ,-mono- and dlpyridines have been synthesized via the reactions of O- and S-containing dinitriles with acetylene in the presence of a Co(2-ethylhexanoate)₂-AlEt₃ catalyst system.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1847–1850, August, 1985.     

Deactivation of nickel catalysts by thiophene in benzene hydrogenation

Kinetic dependences of the catalyst deactivation rates and poison concentrations on the partial pressures of the main reactants have been established. Numerical values for the kinetic constants are given. Poison chemisorption is shown to take place on both unoccupied and occupied active centers and also on the adsorption centers not involved in the main process.

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Synthesis of new thiophene,furan and pyridine substituted 1,2,4,5-oxadiazaboroles

Twenty-two new 3,4,5-trisubstituted 1,2,4,5-oxadiazaboroles were prepared by the cyclocondensation reaction of N-substituted thiophene, furan and pyridine carboxamidoximes with phenylboronic acid in refluxing toluene in good yields. The structures of the new oxadiazaboroles were elucidated by means of spectral measurements (IR, ¹H, ¹³C, ¹¹B NMR, MS, X-ray) and physical data (melting points, elemental compositions by HRMS).     

Anionic polymerization of styrene in the presence of pyridine

An interesting effect of pyridine on the anionic polymerization of styrene in THF is described. Pyridine forms a complex with living polystyrene and greatly slows the polymerization rate without changing the degree of polymerization. From kinetic and spectroscopic studies, it was clear that there exist two active species in this system and the complex between living polystyrene and pyridine was of the 1:1 type, which itself had a weak ability to grow. The formation constant of the complex K was found to be about 4 × 10⁵ l./mole. The effect of substituted pyridine was also studied and the nature of the complex was discussed.     

Extraction of europium from nitrate solutions in the presence of polyfunctional organic compounds

The extraction of europium with benzene solutions of tributyl phosphate (TBP), benzoic acid (BA), and acetylacetone (AA) from nitrate solutions has been studied in the presence of the following polyfunctional organic compounds: acrylamide (AAm), phenanthroline (Phen), Diacetam-5, and Tinuvin-622. Europium distribution data in combination with luminescence spectroscopy of extracts are used to discuss europium complexing with the specified ligands. A feasibility of manufacturing Eu₂O₃ and EuPO₄ films on quartz through the pyrolysis of saturated extracts is demonstrated.     

Synthesis of polyfunctional stable nitrile oxides of the thiophene series and their relative reactivities in 1,3-dipolar cycloaddition with styrene

Stable 2-alkylthio- and 2-alkylsulfonylthiophene-3-carbonitrile oxides that contain various functional groups in the 4 and 5 positions of the thiophene ring (Br, OCH₃, SCH₃, SO₂CH₃) were synthesized. It is shown that the introduction of electron-acceptor substituents into any position of the ring of thiophene-3-carbonitrile oxides gives rise to acceleration of cycloaddition to styrene. The reactivities of o-substituted thiophene-3-carbonitrile oxides of the thiophene series in 1,3-dipolar cycloaddition reactions are determined by the overall effect of the electronic and steric factors of the substituents.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1620–1628, December, 1989.