Oxidation of ethane in the presence of heterogeneous catalysts

Conclusions The inhibiting action of Al₂O₃ and KSK silica gel on the homogeneous oxidation of ethane at 320°C is due to the breakdown of formaldehyde, the branching agent for the oxidation reaction, on these catalysts.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 50–55, January, 1978.     

Polyoxometalates-based heterogeneous catalysts in acid catalysis

Acid catalysis,one of the most important industrial processes,suffers from the toxicity,corrosion and recyclability problems of conventional homogeneous acid ca...     

Conversion of N-arylhydroxylamines in the presence of metal complexes and heterogeneous catalysts

Conclusions The nature of the component distribution and the transformations in the catalytic hydrogenation of aromatic nitro compounds are analogous for the use of metal complex, colloidal, and heterogeneous catalysts. The hydrogenation features the formation of amino compounds due to disproportionation of intermediate N-arylhydroxylamines.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2846–2848, December, 1988.The author thanks A. V. Bulatov for providing samples of the metal complex catalyst.     

Epoxidation of propylene with tert-butyl hydroperoxide in the presence of heterogeneous polymeric catalysts

A series of heterogeneous polymeric molybdenum containing catalysts on the basis of weak acid cation exchanger Amberlite IRC-84 in an organic and water medium was prepared. The catalysts activity and selectivity in the epoxidation of propylene with tert-butyl hydroperoxide are compared. Data about the chemical structure of catalytically active molybdenum containing centres of the modified cation exchanger were obtained.

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Reactions of peroxide radicals with the surface of heterogeneous catalysts in homolytic and heterolytic processes

An interrelation between homolytic and heterolytic stages is found for olefin epoxidation by hydroperoxides and cumene hydroperoxide decomposition in the presence of a heterogeneous catalyst (molybdenum selenide). Peroxide radicals that are formed in homolytic decomposition of the hydroperoxide interact with the catalyst surface. As a result, molybdenum atoms are oxidized to the highest valence state, and new reaction sites are created, on which heterolytic reactions occur. It is shown that olefin, as an electron donor, decreases the catalyst activity in the heterolytic reactions. The limited value for the olefin epoxidation rate, which is independent of the amount of the catalyst used, is explained by the disappearance of active sites on the catalyst surface due to their interaction with the neighboring sites containing adsorbed olefin molecules.     

Direct generation of hydrogen peroxide from formic acid and O2 using heterogeneous Pd/gamma-Al2O3 catalysts

Hydrogen peroxide formation is achieved with remarkable productivity at ambient conditions (25 degrees C and atmospheric pressure) in aqueous medium using a heterogeneous catalytic system; formic acid is decomposed in the presence of a continuous flow of O(2) over Pd/gamma-Al(2)O(3) catalyst leading to the generation of hydrogen peroxide; the addition of a negligible amount of bromide ion improves the selectivity of the reaction.     

Reactions of arensulfenamides with olefins in the presence of picric acid

N-(2- and 4-Nitrophenylthio)morpholines in the presence of equimolar amounts of picric acid enter into the reaction of electrophilic sulfenylation of the C=C norbornene bond to give bi- and tricyclic sulfides. With cyclohexene,trans-2-arylthiocyclohexanol are formed. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1661–1663, August, 1998.     

Cyclization of crotyl phenyl sulfide in the presence of acid catalysts

Crotyl phenyl sulfide is converted to 2-ethyl-2,3-dihydrobenzothiophene and 2- and 4-methylthiochromans in the presence of -Al₂O₃ and 5, 10, and 20% ZnCl₂/Al₂O₃ at 300°C and is also isomerized to 1-butenyl- and 3-butenyl phenyl sulfides and cleaved to thiophenol.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1337–1339, October, 1973.     

Alkoxylation and hydration of camphene in the presence of acid catalysts

The alkoxylation of camphene in the presence of various acid catalysts is studied. Alkylisobornyl ethers are obtained in high yields if the heteropolyacidsH ₄ SiW ₁₂O₄₀ andH ₃ PW ₁₂O₄₀ are used as the catalysts. The mechanism of the acid-catalyzed hydration of camphene in aqueous-alcohol solutions is examined. Nizhegorod State Technical University, 603000, Nizhnii Novgorod, ul. Minina, 24, fax (8312) 41 76 62; OAO “Lesosibirskii Rosin-Extraction Plant,” 663131, Krasnoyarsk Territory. Lesosibirsk-4, ul. Privokzalnaya, 2 fax (39145) 2 26 01. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 598–603, September–October, 1999.     

New evidence of the presence of internal electron donors in active sites of heterogeneous Ziegler-Natta catalysts

Poly(propylene) samples produced by heterogeneous Ziegler-Natta catalysts containing different internal electron donors were fractionated by using temperature rising elution fractionation; some key fractions were analyzed with ¹³C NMR. It was found that internal electron donors with different structures can convert aspecific active sites into different isospectrific ones. The employment of bis(2-ethylhexyl) phthalate as internal electron donor leads to chemically inverted structures in the atactic fraction. This suggests that an internal electron donor may also exist in the environment of aspecific active sites.     

Supported molecular catalysts for the heterogeneous CO2 electroreduction

The thorough understanding of homogeneous catalysis has triggered intense research activities on the immobilization of molecular catalysts for the heterogeneous CO₂ electroreduction. Herein, we discuss recent advances in the heterogeneous field with focus on the intrinsic effect coming from the catalyst structure and the extrinsic effect exerted by the catalyst immobilization strategy and support material on the catalytic performance.     

Reactions of alkenesulfenamides with olefins in the presence of POHal3

A new method for the synthesis of ,"-dihaloalkyl vinyl sulfides was proposed. The method is based on reactions of alkenesulfenamides with olefins in the presence of POCl₃ or POBr₃. The reactions with cage olefins (norbornene, norbornadiene, camphene, and dimethyl 5,6-di-endo-norbornenedicarboxylate) afford stable products, while vinylsulfenylation of a conformationally labile olefin (cyclohexene) give products that decompose during their isolation.