Abstract
Incorporation of Zn atoms into a nanosize Cu lattice is known to alter the electronic properties of Cu, improving catalytic performance in a number of industrially important reactions. However the structural influence of Zn on the Cu phase is not well studied. Here, we show that Cu nano-clusters modified with increasing concentration of Zn, derived from ZnO support doped with Ga3+, can dramatically enhance their stability against metal sintering. As a result, the hydrogenation of dimethyl oxalate (DMO) to ethylene glycol, an important reaction well known for deactivation from copper nanoparticle sintering, can show greatly enhanced activity and stability with the CuZn alloy catalysts due to no noticeable sintering. HRTEM, nano-diffraction and EXAFS characterization reveal the presence of a small beta-brass CuZn alloy phase (body-centred cubic, bcc) which appears to greatly stabilise Cu atoms from aggregation in accelerated deactivation tests. DFT calculations also indicate that the small bcc CuZn phase is more stable against Cu adatom migration than the fcc CuZn phase with the ability to maintain a higher Cu dispersion on its surface.
Highlights
In this work, we have systematically investigated Ga3+ doping into Cu-ZnO by controlling chemical composition and calcination temperature
We were interested to develop these composite materials as effective catalysts for the hydrogenation of dimethyl oxalate (DMO) to ethylene glycol (EG) reaction due to the recent incentive to develop this non-oil based reaction route for chemicals synthesis
This involves the formation of syngas from coal or natural gas, followed by the coupling of CO with methyl nitrite to DMO catalysed by Pd and hydrogenation to EG by Cu11–15
Summary
We have systematically investigated Ga3+ doping into Cu-ZnO by controlling chemical composition and calcination temperature. We were interested to develop these composite materials as effective catalysts for the hydrogenation of DMO to EG reaction due to the recent incentive to develop this non-oil based reaction route for chemicals synthesis. The insecure long-term prospect of petroleum supplies prompts the development of these non-oil based chemical processes This involves the formation of syngas from coal or natural gas, followed by the coupling of CO with methyl nitrite to DMO catalysed by Pd and hydrogenation to EG by Cu11–15. While the coupling reaction is efficiently taken place, one key issue of this new process is the latter catalytic hydrogenation reaction This step has inherent problems with poor stability and short lifetime of the copper-based catalyst during the vapour phase hydrogenation of DMO to EG11,12,15–17. It is believed that this finding can offer a new way to stabilize surface Cu clusters for high activity and stability
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