Abstract
The catalytic efficiency of double metal cyanide (DMC) has been shown to be very effective in heterogeneous catalysis. The catalytic activity of the outer divalent cations (Mn, Co, Ni, and Cu) of a family of hexacyanocobaltates was examined in the oxidation reaction of styrene, as a model molecule, using tert Butyl Hydroperoxide (TBHP, Luperox®) as an oxidizing agent. The most electronegative outer cations showed the best conversions, with 95% for copper, followed by nickel with 85% conversion of the monomer at atmospheric pressure and temperature of 75 °C. The evidence showed that the catalytic activity and selectivity towards oxidized products are strongly linked to the accurate choice of the outer cation in the DMC together with the oxidizing agent.
Highlights
Double metal cyanides (DMCs) are coordination complexes formed from the assembly of two transition metals by cyanometal structures [M’(CN)n ]
The variations in the outer cation within the M–CN–M' chain, but since the Co is always the internal metal, the outer one frequency of the C≡N bond-stretching band for the Co–C≡N–M bridge are associated with the nature will be responsible for the modification in physicochemical behaviour
We supposed that the kinetic equation was equal to r = k[styrene]α [TBHP]β [catalyst]δ for the oxidation of styrene, and we considered that the reaction was pseudo first-order, according to what is reported with similar materials [19]
Summary
Double metal cyanides (DMCs) are coordination complexes formed from the assembly of two transition metals by cyanometal structures [M’(CN)n ]. In heterogeneous catalysis the size and shape-dependent factors are closely related to the surface chemistry of the catalyst, which essentially determines the catalytic performance In this sense, as the hexacyanocobaltates have well defined cubic structures, in the present study the outer cation is changed, adding own characteristics to each material and it will be this cation that must differentiate the catalytic performance predominantly. Co–Co, Ni–Co, and Cu–Co have crystallite sizes together to Vp values relatively proportional among them, so it is not justified that these parameters are a determining factor in their catalytic performance In this sense, we consider that it is the nature of the outer cation in direct interaction with an oxidizing agent, such as TBHP (highly polarizable), that dictates its performance
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