Effect of Sm Doping on CO₂-to-Methanol Hydrogenation of Cu/Amorphous-ZrO₂ Catalysts

Abstract

A series of 14 wt % Cu/Sm2O3/a-ZrO2 (a-: amorphous) catalysts for CO2-to-methanol hydrogenation were prepared by a coimpregnation method. When the Sm loading was 5–6 mol %, the CO2 conversion reached the maximum value (10.1% for 5 mol % catalyst and 9.4% for 6 mol % catalyst). In contrast, methanol selectivity decreased monotonically from 79% to 67% as the Sm loading increased from 0 to 7 mol %. Among the prepared catalysts, the 5–6 mol % Sm-doped Cu/a-ZrO2 catalyst exhibited the highest methanol production rate of 3.7 mmol gcat –1 h–1, which was ca. 20% greater than that with no Sm dopant (3.1 mmol gcat –1 h–1), at 1.0 MPa and 230 °C with a space velocity = 6 L­(STP) gcat –1 h–1. When we took into consideration the results of temperature-programmed reduction by H2, X-ray diffraction, and X-ray photoelectron spectroscopy, doping Sm species into Cu/a-ZrO2 increased the number of surface-dispersed Cu2+, resulting in the high dispersion of Cu nanoparticles, as well as an increase in the number of the active sites (interfacial sites between Cu and a-ZrO2). Furthermore, according to the temperature-programmed desorption of CO2, Sm doping promoted CO2 adsorption on the catalysts and simultaneously activated CO2. The negative effect of Sm doping is a drop in methanol selectivity. In other words, it results in an improvement in methanol decomposition to CO. An excess amount of Sm led to Cu sintering. The main active sites (Cu-ZrO2 interface) are expected to be destroyed by sintering the Cu particles, in other words, losing the interaction between Cu and a-ZrO2. Therefore, since the above-mentioned positive effect and negative effect coexist, there is an optimum value for the amount of Sm doping.

Adsorption of CO2 on Amorphous and Crystalline Zirconia: A DFT and Experimental Study

“…The experimental results of CO 2 -TPD showed a broad peak at ca. 140 °C (Table ), which corresponds to the adsorption energy of 1.2 eV according to the Redhead equation . The previous experimental study also reports a slightly smaller yet similar value of 95 kJ/mol = 0.99 eV for the am -ZrO 2 surface, which are closer to our theoretical result.…”

“…3,4 One of the most important applications is methanol synthesis by CO 2 hydrogenation for the reuse of CO 2 to reduce greenhouse gas emissions. To control the absorption and reactivity of CO 2 , morphology dependence is crucial, 1,5,6 and experimental preparations can control the morphology of zirconia. For example, the dehydration of amorphous (am)-Zr(OH) 4 results in amorphous zirconia (am-ZrO 2 ).…”

“…Zirconium oxides, ZrO 2 , and zirconium hydroxides, Zr­(OH) 4 , also called hydrous zirconia, are important materials for various scientific and industrial applications, such as catalysts , and adsorbents. , One of the most important applications is methanol synthesis by CO 2 hydrogenation for the reuse of CO 2 to reduce greenhouse gas emissions. To control the absorption and reactivity of CO 2 , morphology dependence is crucial, ,, and experimental preparations can control the morphology of zirconia. For example, the dehydration of amorphous ( am )-Zr­(OH) 4 results in amorphous zirconia ( am -ZrO 2 ).…”

Active Sites on ZnxZr1–xO2–x Solid Solution Catalysts for CO2-to-Methanol Hydrogenation

“…Methanol has been proposed as a building block molecule in C1 chemistry. Cu-based catalysts (reaction temperature: approximately 250 °C and reaction pressure: 3–5 MPa) have been studied for CO 2 -to-methanol hydrogenation. − Methanol conversion to valuable fuels and chemicals, such as olefins and aromatics, proceeds over solid acid catalysts at > 400 °C . It is assumed that the abovementioned reactions are carried out in the corresponding reactors, leading to CO 2 conversion to fuels and chemicals.…”

Adsorption of CO2 on Amorphous and Crystalline Zirconia: A DFT and Experimental Study

“…3,4 One of the most important applications is methanol synthesis by CO2 hydrogenation for the reuse of CO2 to reduce greenhouse gas emissions. To control the absorption and reactivity of CO2, morphology dependence is crucial, 1,5,6 and experimental preparations can control the morphology of zirconia. For example, the dehydration of amorphous (am)-Zr(OH)4 results in amorphous zirconia (am-ZrO2).…”