Interaction of hydrogen with model Cu-Zn methanol synthesis catalyst prepared by decomposition of mixed hydroxicarbonate is studied by inelastic neutron scattering, in situ FTIR/MS, and thermal analysis. Reduced (Cu _0.08,Zn_0.92)O mixed oxide accumulates 6H/Cu, mainly as hydride, hydroxyl and formate species. The reduction of copper in the (Cu,Zn)O mixed oxide occurs via a reversible redox interaction with H₂ and absorption of protons as OH^--groups with ν = 3250 cm^-1 and δ ≈ 1430-1480 cm^-1. Kinetic and thermodynamic parameters of this process are evaluated. The weight loss during the reduction is due to the decomposition of the residual carbonate groups to CO₂ via formate intermediates, which occurs in the presence of hydrogen. Exposure of (Cu,Zn)O to air prior to the reduction strongly affects the kinetic parameters of the reduction process.

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Two-line ferrihydrite (2L-FH) is a metastable, heavily disordered, partially hydrated Fe(III) oxide. The catalyst prepared by heat treatment of 2L-FH promoted with chromium ions (̃9 at %) and copper ions (4-7 at %) is much more active in the water gas shift (WGS) reaction at low temperatures (<350°C) than the conventional Fe-containing catalysts. According to XAFS spectroscopy data, the copper cations in 2L-FH are in the Cu2+ state and are in a tetragonally distorted octahedral environment, while under the WGS conditions at <350° C, copper is in the reduced state, specifically, in the form of ultrafine (<2 nm) Cu0 particles. It is due to these particles that the catalyst is very active below 350°C. Above 400°C, the Cu0 parti-cles are deactivated under the reaction conditions and the catalytic activity is only due to iron active sites, whose number is proportional to the specific surface area of the catalyst. The specific activity of the catalyst at these temperatures is close to the activity of the conventional (hematite-based) WGS catalysts. The high activity of the 2L-FH-based catalyst at <350°C makes it possible to reduce the starting temperature of the adiabatic high-Temperature WGS reactor.@en

The chapter reviews the data on the 2-line ferrihydrite structure and texture, methods for its preparation, and catalytic properties of 2LFH-based catalysts. Since 2-line ferrihydrite is metastable, the necessity and possibility of inhibiting its crystallization to hematite is discussed and new data on the kinetics of crystallization process are reported, including the effect of Al3+, Cr3+, and Cu2+ promotion. During discussion, particular attention is paid to the potential of 2LFH in catalytic application.@en

The anionic composition, structural parameters, optical properties and reduction behavior of Cu-MgO solid solution in hydrogen dramatically change after exposure to air. The air-exposed Cu-Mg oxide contains a lot of CO 3 2- and OH- anions. Its reduction proceeds via two stages: (1) diffusion of Cu2+ to the surface and (2) chemical interaction of Cu2+ with hydrogen. The effective activation energy gradually increases from that of the chemical step (65 kJ/mol) to that of the transport step of Cu2+ diffusion (130 kJ/mol). This behavior follows the "compensation effect", which is close to those reported earlier for CuO reduction. On the contrary, reduction of Cu2+ from the Cu-Mg oxide sample, which was not exposed to air after thermal pretreatment in the inert gas, proceeds in one step at 120-160°C with the effective activation energy of 19 kJ/mol, which is manifold less than the reported effective activation energies for various Cu-oxide systems. Water molecules eliminate from the sample slowly along with further heating up to 450°C.@en