Synthesis of Ethanol via Syngas on Cu/SiO₂ Catalysts with Balanced Cu⁰–Cu⁺ Sites

Abstract

This paper describes an emerging synthetic route for the production of ethanol (with a yield of ~83%) via syngas using Cu/SiO(2) catalysts. The remarkable stability and efficiency of the catalysts are ascribed to the unique lamellar structure and the cooperative effect between surface Cu(0) and Cu(+) obtained by an ammonia evaporation hydrothermal method. Characterization results indicated that the Cu(0) and Cu(+) were formed during the reduction process, originating from well-dispersed CuO and copper phyllosilicate, respectively. A correlation between the catalytic activity and the Cu(0) and Cu(+) site densities suggested that Cu(0) could be the sole active site and primarily responsible for the activity of the catalyst. Moreover, we have shown that the selectivity for ethanol or ethylene glycol can be tuned simply by regulating the reaction temperature.

A copper-phyllosilicate core-sheath nanoreactor for carbon–oxygen hydrogenolysis reactions

“…As shown in Fig. 2b, the presence of the dOH vibration at 670 cm À 1 in the calcined sample and the overall spectra being almost the same as that of chrysocolla (spectra from the RRUFF database) 5,25 suggest the existence of the structure of copper phyllosilicate after calcination 5 . Figure 2c shows the XRD pattern of copper phyllosilicates after calcination.…”

“…Copper-based catalysts have been intensively explored for hydrogenation reactions, as the copper sites account for the selective hydrogenation of carbon-oxygen bonds and are relatively inactive for the hydrogenolysis of carbon-carbon bonds [4][5][6] .…”

“…Metallic copper is believed to be an active phase because the activity was frequently found to be proportional to copper-surface area 3,5,16,17 . However, other researchers were not able to establish a linear correlation between activity and coppersurface area relationship and suggested that a synergy between copper and the oxide components also influenced activity.…”

“…However, other researchers were not able to establish a linear correlation between activity and coppersurface area relationship and suggested that a synergy between copper and the oxide components also influenced activity. Earlier work on understanding the active sites of copper catalysts for the hydrogenation of dimethyl oxalate (DMO) 5 , furfural 4 and CO 2 17 indicated that both Cu 0 and Cu þ species were crucial to the activity of copper-based catalysts. It has been suggested that Cu þ acts as the stabilizer of the methoxy and acyl species and could also function as electrophilic or Lewis acidic sites to polarize the C-O bond via the electron lone pair in oxygen.…”

“…The rich porous structures and tunable composition of silicates make them rather appealing for encapsulation of metallic NPs in catalysis 21 . We have demonstrated that copper phyllosilicates [Cu 2 Si 2 O 5 (OH) 2 ] with a lamellar structure could produce stable Cu þ species on its surface in the hydrogenation reaction 5 . The structures with a strong metal-oxide and metal-support interaction make the copper species (particularly for Cu þ species) very stable when the hydrogenation reaction temperature is below 673 K.…”