Hydrogenation of Carbon Dioxide over Co–Fe Bimetallic Catalysts

Abstract

A series of Co–Fe bimetallic catalysts was prepared, characterized, and studied for the hydrogenation of carbon dioxide. The catalyst precursors were prepared via an oxalate coprecipitation method. Monometallic (Co or Fe) and bimetallic (Co–Fe) oxalate precursors were decomposed under a N2 flow at 400 °C and further pretreated under a CO flow at 250 °C. The catalysts (before decomposition of the oxalates or after activation) were characterized by BET, TGA-MS, X-ray diffraction, CO-TPR, SEM, HR-TEM, and Mössbauer spectroscopy techniques. The hydrogenation reaction of CO2 was performed using Co–Fe bimetallic catalysts pretreated in situ in a fixed-bed catalytic microreactor operating in the temperature range of 200–270 °C and a pressure of 0.92 MPa. With increasing Fe fraction, the selectivity to C2–C4 for Co–Fe catalyst increased under all operating conditions. The alcohol selectivity was found to increase with increasing iron content of the Co–Fe catalyst up to 50%, but then it dropped with further addition of iron. Among the three different activation conditions, the CO pretreated Co–Fe (50Co50Fe) catalyst exhibited a much lower selectivity for methane. Addition of 1 wt % Na or 1.7 wt % K to 50Co50Fe catalyst increases its olefinic (C2–C4) and oxygenate selectivities.

Hydrogenation of Carbon Dioxide over K‐Promoted FeCo Bimetallic Catalysts Prepared from Mixed Metal Oxalates

“…In the current context, a significant drop in the conversion of hydrogen was observed with K addition. This is consistent with our earlier proposed mechanism on FeCo bimetallic catalysts, in which potassium may take part in the catalytic cycle for the formation of acetic acid from CO 2 .…”

“…Potassium shifts the product distribution of C 2 oxygenates from CO 2 towards acetic acid. A synergistic effect by potassium (that is, possible involvement in the catalytic cycle, as proposed in our previous work), along with a decrease in the hydrogenation function of the Fe catalyst, likely prevents ethanol formation from the intermediate.…”

“…Iron(II) sulfate heptahydrate 98 %, cobalt(II) nitrate hexahydrate 98 %, potassium nitrate (99.9 %), and oxalic acid dihydrate 99 % were purchased from Sigma–Aldrich Co. and used without further purification. The preparation of cobalt‐containing iron bimetallic oxalates (90 Fe:10 Co) is described elsewhere . Typically, oxalic acid (37.821 g, 0.3 mol) was dissolved in deionized water (250 mL) with constant stirring at T =35 °C.…”

“…They correlated this with weaker adsorption of hydrogen on the metal surfaces. In a recent study, we showed that FeCo bimetallic catalysts offer advantages for CO 2 hydrogenation over monometallic catalysts (Fe or Co) for the production of higher C 2 + hydrocarbons . In a continuation of this vein of research, in this work, the effect of potassium on FeCo‐catalyzed CO 2 hydrogenation was explored.…”

Nanoalloy Materials for Chemical Catalysis

“…A Ga‐doped CuZn/ZnGa 2 O 4 nanocatalyst formed by hydrogen reduction exhibits remarkable catalytic performance in CO 2 hydrogenation . NaBH 4 and hydrazine have also been used as powerful reductants to get NiFe, CoFe, CuNi, FeNi, Sn‐based BMNAs, etc …”