Cobalt intermetallic catalysts

Zubareva et al. found that some chiral bimetalic Raney Ni-Co catalysts modified with TA in hydrogenation of EAA also produced relatively low enantioselectivities, ee of only 5-8%. It is of interest that intermetallic catalysts (IMC) based on LaNis M M" (see Parts 4.3. and 4.5.), containing additional metals, M and M" and modified with TA, revealed significant enantioselectivities after building the cobalt component into this catalyst. In this case ee increased up to 52%. ... 

Skeletal copper is best made from the CuA12 intermetallic compound which has very close to 50 wt% aluminum in the alloy and gives an active and selective catalyst [27-29], Skeletal nickel is also best made from an alloy of about 50 wt% aluminum [25] however, in this case, the alloy consists of more than one intermetallic phase, the combination of which provides the best activity while maintaining adequate strength in the catalytic residue. The most active skeletal cobalt catalysts are made from an alloy of about 60-65 wt% aluminum, which consists of two intermetallic phases, Co2A19 + Co4A113 [30],... 

As has been alluded to above, the catalysts are extensively transformed when exposed to a mixture of CO and H2 at T > / 225°C. This transformation was first noted by Takeshita, Wallace, and Craig (14) in the use of these materials as synthetic ammonia catalysts. RCo. and RFca, intermetallics were converted into iron or cobalt rare earth nitride. This was established by conventional x-ray diffraction measurements. Coon (16) observed that the RNis compounds were transformed by the CO/H2 mixture into R2O3 and Ni, and a similar transformation also was observed by Elattar et al. (17) for ThNis, UNis, and ZrNis. SEM and EDAX results on ThNis show the formation of nickel nodules 0.5 /un in diameter situated on a Th02 substrate. 

Multicomponent metallic hydrogenation catalysts, based on intermetallic compounds (IMC) of rare-earth elements with nickel, copper, cobalt, and other bimetallic systems. Most studies were devoted to two structural systems LnMs and LnMs, where Ln = La, Sm, Gd, Ce, Pr, and Nd and M = Ni (see Klabunovskii, Konenko s group 183,251,252 Compaiison of LnNis catalysts with Ni catalysts supported on oxides of Ln, show higher activities of the IMC s and their hydrides in hydrogenation of propene (100°C, 1 bar), where LaNis proved to be the most active catalyst... 

Among catalysts derived from intermetallic compounds, titanium-iron systems have received some attention. The precise course of reactions involved is not clear. For example, it is claimed that the catalyst derived from a suitably activated TiFe intermetallic phase is TiN + Fe. The TiN is said to react with molecular hydro-gen. On the other hand, in a series of patents on Fe-Ti systems, covering a range of iron-to-titanium ratios, with or without addition transition elements, it is quite clearly regarded that the titanium is capable of forming hydrides. Whatever the mechanism, such systems appear capable of promoting ammonia synthesis in commercial yields at 300 °C, 80 atm, while some are even claimed to be active at 125 °C and 1 atm. Rare earth metals, in combination with iron, ruthenium, or cobalt, can also function as catalysts. Again, the rare earth metals seem to be... 

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