Exchange over transition metal oxides

Alkene oxidation over transition metal exchanged zeolites has been of recent interest. Yu and Kevan have studied the partial oxidation of propene to acrolein over Cu2+ and Cu2+/alkali-alkaline earth exchanged zeolites.33 In both... 

Destmctive reaction of Cl-containing compounds with transition metal oxides supported on MgO or CaO has been smdied (12-14). The order of activity found for transition metals (V > Mn > Co > Fe > Ti > ) is similar to that for typical oxidation reactions. Another interesting finding by the same group was that the transition metals catalyze the exchange reaction between chloride and oxide ions (14). An intermediate metal chloride such as VClx may migrate over the MgO nanocrystal to assist the exchange of Cl with O. ... 

Shimizu K,Akahane H,KodamaT and Kitayama Y (2004), Selective photo-oxidation of benzene over transition metal-exchanged BEA zeolite , Appl Catal A Gen, 269,75-80. 

Seiyama T, Arakawa T, Matsuda T, Yamazoe N, Takita Y (1975) Catalytic Reduction of Nitric-oxide with Ammonia over Transition-metal Ion-exchanged Y-zeolites. Chem Lett 4... 

The oxidation of intracrystalline ammonium cations has been reported 3, 65), but most oxidations over zeolites featuring molecular oxygen-hydrocarbon systems have featured transition metal zeolites. The oxidative dehydrogenation of ethylbenzene to styrene and selective oxidation of benzyl alcohol to benzaldehyde over MnY at 250°-370°C were reported earlier 62). Propylene has been oxidized to formaldehyde, COo, and minor quantities or acrolein and acetaldehyde over Cu( II)-exchanged Y-type zeolite (39). 

Copper-exchanged zeolite ZSM-5 have received considerable attention of researchers over last several years because of their ability to promote both the total oxidation of alkanes and the decomposition of NOj [1 - 12]. However, little is known about the possibility of the CuH-ZSM-5 system modification as a result of the introduction of ions of the second active transition metal. A high and stable catalytic activity of Co/H-ZSM-5 in total oxidation of CH, was demonstrated recently [13]. Therefore, the mutual influence of two active components stabilized by H-ZSM-5 matrix is of interest. 

The remainder of this section will focus on true SBMs, which have been the subject of vigorous research. Despite the electron deficiency of early transition metal, lanthanide, and actinide complexes, several groups reported that some of these d f" complexes do react with the H-H bond from dihydrogen and C-H bonds from alkanes, alkenes, arenes, and alkynes in a type of exchange reaction shown in equation 11.32. So many examples of SBM involving early, middle, and late transition metal complexes have appeared in the chemical literature over the past 20 years that chemists now consider this reaction to be another fundamental type of organometallic transformation along with oxidative addition, reductive elimination, and others that we have already discussed. 

For a better understanding of the first steps of the reaction of NO over Cu-ZSM-5 and Fe-ZSM-5 zeolites the following measurements were performed (i) the products of the gas phase interactions were followed by MS, (ii) the valence state and coordination of transition metal ions in zeolites by ESR spectroscopy. Catalysts were prepared both by conventional and solid-state ion-exchange methods and pretreated in vacuum, in oxidative and in reductive atmosphere. The conventional ion-exchanged samples are more active in NO decomposition than the solid-state exchanged ones. Over the reduced catalysts the first step consists in N2O formation and the oxidation of Cu Cu (Fe Fe ) followed by N2O reduction to N2 (in these conditions O2... 

New methods of micro heterogeneous super loaded ZnO/FAU systems synthesis were developed which allow to control oxide phases state. Their formation and properties were studied by TG-DTA, XRD and IR spectroscopy. High ZnO dispersion, which is provided by a decomposition of Zn salts on ion exchanged FAU, is favorable for catalytic conversion of CH3OH to water-free CH2O over these systems. Suggested methods can be used for a preparation of systems containing oxide phases of one or several transition metals which, due to their unusual properties, may find various applications in adsorption and catalysis. 

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