Chromium ions incorporation

A novel method has been developed for hydrothermal synthesis of zeolite beta with high chromium content and low aluminum content under static conditions. The crystalline phase and spectroscopic property of this material were characterized by means of XRD, XRF, IR, UV-Vis DRS, ESR and SEM. The results revealed that part of the chromium ions were incorporated into the zeolite framework during crystallization. Using tris(acetylacetonato) chromium(III), [Cr(C5H702)3], as a chromium source, Cr/Si molar ratio can be up to 1/48 in the calcined and ion-exchanged sample. The chromium aluminosilicate exhibited a high oxidative activity in the presence of dilute H2O2. 

If the composite coating would be defined as the combinadOTi film of two or more substances, it would be incorporated into the category of an alloy film. In this chapter, however, we would like to restrict the composite film as a dispersitMi type film in a matrix as shown in Fig. 9 schematically [5], As an example, we have already mentioned (in chapter What Is Environmentally Friendly Surface Finishing ), a silane based film with some dispersed nano-metallic powders. However, other systems have been proposed for the hexavalent chromium ion free process. 

As a result, it was possible to incorporate chromium ions into... 

Cr-ZSM-5 catalysts prepared by solid-state reaction from different chromium precursors (acetate, chloride, nitrate, sulphate and ammonium dichromate) were studied in the selective ammoxidation of ethylene to acetonitrile. Cr-ZSM-5 catalysts were characterized by chemical analysis, X-ray powder diffraction, FTIR (1500-400 cm 1), N2 physisorption (BET), 27A1 MAS NMR, UV-Visible spectroscopy, NH3-TPD and H2-TPR. For all samples, UV-Visible spectroscopy and H2-TPR results confirmed that both Cr(VI) ions and Cr(III) oxide coexist. TPD of ammonia showed that from the chromium incorporation, it results strong Lewis acid sites formation at the detriment of the initial Bronsted acid sites. The catalyst issued from chromium chloride showed higher activity and selectivity toward acetonitrile. This activity can be assigned to the nature of chromium species formed using this precursor. In general, C r6+ species seem to play a key role in the ammoxidation reaction but Cr203 oxide enhances the deep oxidation. 

The production of corrosion-resistant materials hy alloying is well established, hut the mechanisms are noi lull) understood. It is known, of course, that elements like chromium, mckcl. titanium, and aluminum depend for their corrosion resistance upon a tenacious surface oxide layer (passive film). Alloying elements added for the purpose of passivation must be in solid solution. The potential of ion implantation is promising because restrictions deriving from equilibrium phase diagrams frequently do not applv li e., concentrations of elements beyond tile limits of equilibrium solid solubility might he incorporated). This can lead to heretofore unknown alloyed surfact-s which are very corrosion resistant... 

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