E. Tempesti

Heterogenized boron(III)-molybdenum(VI) mixed oxo derivatives as new bimetallic catalysts for cyclo-hexene liquid-phase epoxidation

Abstract The catalytic epoxidation of cyclohexene has been studied in the liquid phase using as catalysts molybdenum-boron mixed oxo derivatives supported on new polymeric resins. The binary system catalysts, in which the formation of B-O-Mo chemical bonds is suggested on the basis of spectral data, retain constant activity when recycled. Relative to conventional homogeneous molybdenum catalysts, no chemical degradation is observed.

Bimetallic boron(III)-molybdenum(VI) catalysts as new model compounds in the epoxidation of cyclohexene

Abstract The epoxidation of cyclohexene has been kinetically investigated in the presence of bimetallic boron(III)-molybdenum(VI) model compounds in order to determine with respect to conventional catalysts the influence of boron in terms of oxygen transfer and catalyst deactivation.

Hydrogenation of co over ZrO2-supported Rh catalysts : kinetic aspects

Abstract To characterize the nature of the species present on a Rh/ZrO2 catalyst during CO absorption, TPD and IR spectroscopic studies were conducted. The results have been used to satisfactorily account for the experimental rate equations determined for ethanol and methane formation by using CO and H2 partial pressure dependence. The form of the rate expressions obtained for each product is explained in terms of a mechanism for the synthesis of both products.

Heterogenized phosphorus(V)-molybdenum(VI) mixed OXO derivatives as bimetallic catalysts for cyclohexene liquid-phase epoxidation

Abstract Some physicochemical properties of an Mo-fixed catalyst obtained by ready reaction between molybdic acid and the surface phosphoric acid groups of a newly commercialized resin have been investigated by SEM, TG and IR methods. The differences between the surface properties of the fixed catalyst and conventional impregnation catalysts are discussed. The catalytic activity of the mixed P V -Mo VI catalyst has been evaluated in the epoxidation of cyclohexene relative to the behaviour of conventional Mo VI homogeneous catalysts or B III -Mo VI catalysts heterogenized using the same procedure.

New Polydentate Mo(vi) - Grafted Poly(Amido Amine) Resins as Heterogeneous Epoxidation Catalysts

Abstract New heterogeneous oxygen-transfer catalysts have been prepared by Mo(VI) grafting on suitably functionalized poly(amido amine) resins containing units derived from carboxylic aminoacids. One of these catalysts prepared starting from N,N′-ethylene-diaminoacetic acid proved particularly successful in typical liquid-phase oxidation reactions.

Heterogenized B(III)-Mo(VI) Mixed OXO Derivatives as New Bimetallic Catalysts for Liquid-Phase Oxygen-Transfer Reactions to Olefins

Abstract New molybdenum containing dihydroxyboryl-substituted resins have been prepared and some of their properties studied. SEM was used to assess the effect of the grafting procedure on the textural morphology of the resins. Additional informations were obtained by using an image analyzer coupled with an optical microscope. The catalytic properties of these materials have been evaluated by using cyclohexene epoxidation as a test with respect to conventional molybdenum peroxo complexes stabilized by picolinato and pyridine-2,6-dicarboxylato ligands.

Molybdenum Catalyzed Oxygen-Transfer Reactions. Heterogenization of Homogeneous Catalysts by Using New Dihydroxyboryl-Substituted Resins

Conventional molybdenum catalysts have been heterogenized by using new dihydroxyboryl-substituted resins. The specific activity of the grafted catalyst increases with increasing protonation of the grafted complex. The optimum molar ratio of molybdenum to boronic groups of the support is equal to one. No degradation of the catalyst is observed.

Thermal stability of polymer-supported boronic acids functionalized with molybdenum derivatives

Abstract Two novel molybdenum-containing dihydroxyboryl-substituted resins (used as catalysts for oxygen-transfer reactions) have been prepared and thermally analyzed. Simultaneous TG-DTA experiments were run to assess the effect of the grafting procedure on their thermal behaviour. Additional information concerning the structural modifications observed was obtained by infrared spectroscopy.

Thermal stability of substituted poly-xylylenes

The insertion of meta units in the chain of poly-p-xylylene decreases both the onset temperature of oxidative degradation and the rate of decomposition.Functionalization of the polymer with chlorine and sulphonic groups makes the chain more resistant to high temperature treatments, notwithstanding the low stability of the substituent groups.ZusammenfassungDie Einführung von Metaeinheiten in die Kette von Poly-p-xylen setzt sowohl die Einsetztemperatur des oxydativen Abbaues als auch die Zersetzungsgeschwindigkeit herab. Die Einführung von Chlor und Sulfogruppen erhöht trotz der geringen Stabilität der Substituenten die Temperaturbeständigkeit der Kette.РезюмеВведение мета-замест ителей в поли-п-ксилен приводит к уменьшени ю температуры окислительного расп ада и скорости разлож ения. Наличие в полимере су льфогруппы и хлора делает цепь более сто йкой к высокотемпера турной обработке, несмотря н а низкую устойчивост ь таких заместителей.

New Covalent Boron(Iii) - Molybdenum(Vi) Mixed Oxo Model Compounds As Eligible Hetero Bimetallic Catalysts For Propylene Epoxidation

New boron(III)-molybdenum(VI) mixed covalent oxo compounds have been tested in order to assess the possibility of modifying the electronic requirements for hydroperoxide activation through its coordination to the metal centre prior to the oxygen-transfer step.