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The purpose of this work was the preparation and characterization of two new catalysts POSS-ATZAc-[Mo(η 3 -C 3 H 5 )Br(CO) 2 ] (POSS-Mo-I) and POSS-ATZAc-[Mo(CO) 3 Br 2 ] (POSS-Mo-II). The new heterogeneous catalysts were characterized by several techniques and used as catalysts for the epoxidation of olefins, presenting high catalytic activity. To study and optimize the syntheses of the heterogeneous catalysts, immobilization experiments of the [Mo(η 3 -C 3 H 5 )Br(CO) 2 (NCMe) 2 ] and [Mo(CO) 3 Br 2 (NCMe) 2 ] organometallic complexes on the modified polyhedral oligomeric silsesquioxane were performed. The sorption properties of the modified silsesquioxane showed to be dependent of the contact time, concentration and temperature. Catalysts were tested in the epoxidation of six olefins and compared with homogeneous species [Mo(η 3 -C 3 H 5 )Br(CO) 2 (ATZAc)] (Mo-I) and [Mo(CO) 3 Br 2 (ATZAc)] (Mo-II). To the best of our knowledge, this paper is the first that has reported the preparation and characterization of two new heterogeneous catalysts, as well as the comparison with homogeneous species for catalytic epoxidation of olefins. [ABSTRACT FROM AUTHOR]

Abstract: Steam cracking of hydrocarbons has been the major source of light olefins for more than half a century. The recent studies have reported that ethylene and propylene can also be produced through the cracking of hydrocarbons over modified ZSM-5 zeolites in a considerable amount. This paper highlights the important current ideas about acid-catalyzed hydrocarbon cracking that has resulted in high yield of ethylene and propylene. Light olefin production via catalytic cracking of various industrial feedstocks, ranging from heavy hydrocarbons to ethane, over modified ZSM-5 zeolites, has been reviewed in the present paper. Furthermore, the influence of various employed promoters, i.e., alkali and alkaline earth, transition, rare earth elements, and phosphorus, on the chemical properties of the modified ZSM-5 and the performance of resulting catalyst in enhancing the selectivity to light olefins, have been addressed. Moreover, the influences of different factors, including the zeolite acidity, Si/Al ratio and the temperature, on the light olefin production and the reaction scheme have been specified. The role of incorporated element in the catalytic cracking mechanism is also summarized. [Copyright &y& Elsevier]

Carbosilylation is a straightforward procedure to install both silyl and organic functional groups onto organic molecules. For example, allylsilylation of alkenes with allylsilanes affords 5-silyl-1-pentene derivatives. In this review paper, catalytic allylsilylations and arylsilylations of alkenes, alkynes, and cyclic acetals are summarized. Specific catalyses of Lewis and Brønsted acids, such as HfCl4 and proton-exchanged montmorillonite, will be discussed. Intramolecular reactions as well as intermolecular allyl- and arylsilylations have been achieved. In the case of the Brønsted acid catalyst, cationic Si species generated and acted as catalytically active species. The structure of the cationic Si species depends on the type of Brønsted acid used. A disilyl cation was proposed as the catalytically active site for carbosilylations of alkenes and alkynes, while a monomeric Si species was active for allylsilylation of cyclic acetals. [ABSTRACT FROM AUTHOR]

Abstract: This paper describes a kinetic investigation of the ethene tetramerization catalyst system comprising CrCl3(THF)3, a bis(diphenylphosphino)isopropylamine Ph2PN( i Pr)PPh2 as ligand and MAO as catalyst activator. The main focus of the experimental study lied on the influence of the ligand to chromium molar ratio on the catalyst performance and the selectivity towards 1-octene. It was found that a sub-stoichiometric ligand/Cr ratio leads to a Schulz–Flory product distribution, while unusual odd-numbered 1-olefins as by-products were formed. [Copyright &y& Elsevier]

The front cover artwork for Issue 18/2017 is provided by the Fritz-Haber-Institut der Max-Planck-Gesellschaft, Department of Inorganic Chemistry, Berlin (Germany). The image shows the proposed network of consecutive and parallel reactions in oxidation of propane over vanadium oxide catalysts. Detailed understanding of the complex system is necessary to advance catalyst and process design in terms of high selectivity to desired olefins and oxygenates, prevention of CO2 formation, and sustainable use of resources. See the Full Paper itself at . [ABSTRACT FROM AUTHOR]