ChemInform Abstract: Mössbauer and X‐Ray Photoelectron Spectroscopic Evidence for the Structure of Supported Bimetallic Catalysts: FeRu, FeRh, FePd, FeIr, and FePt on SiO₂.

Abstract

Mit Ausnahme von FePd/SiO2 enthalten die reduzierten Titelkatalysatoren das Edelmetall als M°, während Fe nur teilweise zu Fe° reduziert wird.

Pd-Fe/SiO2 Catalysts in the Hydrogenation of 2,4-Dinitrotoluene

“…In accordance with similar results reported elsewhere (21,33), over a limiting quantity of iron, the effect of palladium in promoting the reduction of iron appears to be significantly diminished. The fact that a-Fe XRPD peaks sometimes appear in catalysts with a relatively high iron content is probably due to the presence of large particles, the cores of which were not completely oxidized during the passivation process.…”

“…By means of various structural techniques (especially Móssbauer spectroscopy) several authors (21,25,33,34) found in Pd-Fe bimetallic supported catalysts the formation of Pd,Fe,-, alloys having different composi- tions. In particular, in the paper by Liefz et al (21) the composition of the Pd,Fe,-, alloys on silica was estimated in the range 0.67 ( x ( 0.80 for catalysts containing about 2 wtVo of Pd, as in our case.…”

Structure and Reactivity of Bimetallic FeIr/SiO2 Catalysts after Reduction and during High-Pressure CO Hydrogenation

“…3d) indicates that a carbide phase forms from the α-Fe, and that part of the Fe 3+ is reduced to Fe 2+ . Conversion of Fe 3+ to Fe 2+ has also been observed after adsorption of CO on bimetallic FeM catalysts at room temperature (10)(11)(12). The in situ spectrum recorded during reaction at 270 • C (Fig.…”

“…The models can be divided in two types, which assume either full reduction of the metal (6), or the presence of an iron oxide phase in addition to an alloy (7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22); incidentally, unalloyed metals may be present as has been observed in FePd/SiO 2 (17,18).…”

“…Indeed, recent work by Schuenemann et al (23) confirms that zerovalent iron in the surface of FeRh alloys can have a similar isomer shift and quadrupole splitting as high-spin trivalent iron has. However, several studies have shown that at least a substantial part of the doublet should be assigned to Fe 3+ (9)(10)(11)(12)14). Niemantsverdriet et al (11) discuss three possible arrangements (Figs.…”