Copper–Zirconia Catalysts: Powerful Multifunctional Catalytic Tools to Approach Sustainable Processes

Abstract

Copper–zirconia catalysts find many applications in different reactions owing to their unique surface properties and relatively easy manufacture. The so-called methanol economy, which includes the CO2 and CO valorization and the hydrogen production, and the emerging (bio)alcohol upgrading via dehydrogenative coupling reaction, are two critical fields for a truly sustainable development in which copper–zirconia has a relevant role. In this review, we provide a systematic view on the factors most impacting the catalytic activity and try to clarify some of the discrepancies that can be found in the literature. We will show that contrarily to the large number of studies focusing on the zirconia crystallographic phase, in the last years, it has turned out that the degree of surface hydroxylation and the copper–zirconia interphase are in fact the two mostly determining factors to be controlled to achieve high catalytic performances.

Enhanced Direct Dimethyl Ether Synthesis from CO2-Rich Syngas with Cu/ZnO/ZrO2 Catalysts Prepared by Continuous Co-Precipitation

“…The direct process requires two admixed catalysts or a bifunctional catalyst system which catalyses both MeOH formation (reactions (1) and (2)) and MeOH dehydration (reaction (4)) [8]. For the hydrogenation of CO 2 to MeOH, the utilisation of ZrO 2 -modified copper catalysts is well established [9][10][11][12][13][14][15][16][17][18][19][20]. In contrast to the industrially used MeOH catalyst system, Cu/ZnO/Al 2 O 3 (CZA), which is optimised for the selective conversion of CO-rich syngas to MeOH, the Cu/ZnO/ZrO 2 (CZZ) system exhibits a higher tolerance towards water and is therefore favourable for the hydrogenation of CO 2 -rich syngas (reaction (2)) [9].…”

On demand production of ethers or alcohols from furfural and HMF by selecting the composition of a Zr/Si catalyst

“…The acid-base properties depend on the nature and the ratio between the two mother oxides. [94][95][96][97] By FT-IR of adsorbed pyridine it is possible to distinguish between Lewis and Brønsted acid sites, while a weak interaction between the catalyst and the probe molecule (physisorption or hydrogen bonding) can be excluded above 100°C. [98][99][100][101][102] The results, collected at the reaction temperature, namely 120°C, are reported in Fig.…”

Effect of Cu and Cs in the b-Mo2C System for CO2 Hydrogenation to Methanol

“…CO2+4H2  CH4+2H2O ΔH° 298 K = −165 kJ mol −1 (2) CO2+3H2 → CH3 OH+ H2O ΔH° 298 K = -50 kJ mol −1 (3)…”

“…The most studied system is Cu-ZnO for which copper has proven to be critical when it is loaded onto oxides supports such as ceria or alumina. Unfortunately, these catalysts suffer deactivation due to the oxidation and sintering of copper upon reaction conditions [2,3]. Transition metal carbides (TMCs) have received a lot of attention since they display excellent catalytic behavior in transformations such as steam reforming of methanol, dry reforming of methane or CO hydrogenation [4].…”