Effects of Cu Precursor Types on the Catalytic Activity of Cu/ZrO₂ toward Methanol Synthesis via CO₂ Hydrogenation

Abstract

This paper presents the influence of different types of copper precursors on CO2-to-methanol hydrogenation over copper nanoparticles on amorphous ZrO2. Here, we chose copper nitrate hydrate, copper acetate hydrate, and a copper ammine complex as the precursor. A copper-acetate-based catalyst, which was precalcined at 350 °C, was more active and selective toward methanol than were the other catalysts. Regardless of the different copper precursors, after calcining a mixture of a copper precursor and amorphous ZrO2 at 350 °C, surface-dispersed Cu2+ species ([CuO4] square planes) were partly formed on amorphous ZrO2. The Cu2+ species was reduced by H2 to form Cu0 nanoparticles (<5 nm). This paper reports that using copper acetate monohydrate as a copper precursor leads to the greater number of active sites (Cu0a-ZrO2 interfacial sites) compared with the other precursors.

Dimethyl Ether Synthesis from CO₂–H₂ Mixture over Cu/Amorphous-ZrO₂ Mixed with FER-type Zeolite

“…The methanol yield of CZ (9 mmol h -1 g-Cu -1 ) was higher than that of MDC (7 mmol h -1 g-Cu -1 ), and the methanol selectivity of CZ (64.0 %) was higher than that of MDC (29.6 %). Therefore, CZ catalyst was more specific for CO2-to-methanol hydrogenation than MDC, consistent with our previous report 27) . The formation rates of CH3OH and DME over CZ FER (6 mmol h -1 g-Cu -1 ) were approximately three-fold higher than those over MDC FER (2 mmol h -1 g-Cu -1 ) despite the same F/W (ca.…”

“…The gel was dried at 110 °C overnight and calcined at 350 °C for 5 h in an elec-tric furnace. According to our previous research 25) 27) , copper cations in the catalyst were doped into the amorphous ZrO2. Cu/ZnO/Al2O3 (MDC-7 supplied by Clariant K.K.…”

“…Transmission electron microscopy (TEM) images of the mixed catalysts of CZ FER and MDC FER were collected using a JEM-2100F (JEOL Ltd.) operated at 200 kV. The exposed surface areas of metallic copper of the CZ and the MDC were measured by an N2O titration technique, according to our previous study 27) . We previously reported that the interaction between copper and a-ZrO2 prevents N2O molecules from oxidizing the metallic copper surface, which hinders the accurate measurement of the surface area of metallic copper 27) .…”

“…The exposed surface areas of metallic copper of the CZ and the MDC were measured by an N2O titration technique, according to our previous study 27) . We previously reported that the interaction between copper and a-ZrO2 prevents N2O molecules from oxidizing the metallic copper surface, which hinders the accurate measurement of the surface area of metallic copper 27) . Therefore, the space velocity and catalytic activity for the reaction test were normalized by the copper amount rather than by the copper surface area.…”

CO2 hydrogenation to methanol: the structure–activity relationships of different catalyst systems

“…Hence, the complexes built from Cu cations and oxygen vacancies preferentially on t-ZrO 2 were proposed as the active site for the methanol synthesis reaction. Tada et al (2019) demonstrated the importance of the interfacial area and surface basicity on the catalytic activity for Cu/ZrO 2 catalysts. Utilizing a Cu nitrate precursor resulted in residual nitrogen that bound to basic sites of the ZrO 2 support, which reduced the activity of the catalysts.…”