The remarkable activity and stability of a highly dispersive beta-brass Cu-Zn catalyst for the production of ethylene glycol

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.

CO2 Hydrogenation to Methanol over Catalysts Derived from Single Cationic Layer CuZnGa LDH Precursors

“…4athat CZG samples display a complex and broadened reduction peak accompanied by shoulders in the temperature range of 150-270 o C. This indicates that some reduced Cu species exist in heterogeneous chemical environments (variation in size and structure), thus leading to different peak maxima at different reduction temperatures. The reduction range of 150-200 o C (low temperature shoulder) matches with that of Cu2O but its content in CZG samples diminishes at higher Ga loading25,37 . The higher temperature main peak is attributed to the broad reduction of CuGa2O4 and CuO phases of different sizes.…”

“…At the Ga concentrations of 30 or 40 mol%, zinc-containing malachite phase of (Cu,Zn)2(CO3)(OH)2 is preferably formed. The formation of these two hydroxyl-carbonate phases has been widely reported in the literature using similar co-precipitation preparation method 7,30,[37][38][39][40] . The peak broadening in the XRD patterns with the increase in Ga concentration provides evidence of the use of Ga to reduce the crystal size of aurichalcite phase.…”

Intercalating lithium into the lattice of silver nanoparticles boosts catalytic hydrogenation of carbon–oxygen bonds

“…Compared with monometallic catalysts, bimetallic catalysts can give tunable electronic structures and show more unique catalytic properties. Our group has conducted in-depth research in the field of bimetallic catalysts for selective hydrogenation of C–O bonds, such as Au–Ag, 45 Ag–Ni, 59,60 Cu–Ag, 61 Cu–Au, 62 Cu–La, 63 Cu–Zn, 64 etc. Also, smaller size reduced Li, B and C can also form bimetallic Pd compounds but with the added atoms in the interstitial sites when high reduction temperature and catalytic Pd are used.…”

Copper-Based Catalysts Confined in Carbon Nanocage Reactors for Condensed Ester Hydrogenation: Tuning Copper Species by Confined SiO2 and Methanol Resistance

“…Increasing the Cu content can increase the density of active sites but only up to a loading at which the agglomeration of Cu decreases the exposure of metal sites. − Another challenge is that Cu may be mobile because of its low Hüttig temperature (134 °C), which is much lower than the ester hydrogenation temperature (higher than 200 °C generally). This leads to catalyst deactivation by growing the Cu particles . Responding to these challenges, many groups have focused on stabilizing supported Cu particles.…”