Heterogeneously Catalyzed Hydrogenation of Carbon Dioxide to Methane at Increased Reaction Pressures

Abstract

In der vorliegenden Arbeit wurden vor allem Ni‐ und Ru‐haltige Trägerkatalysatoren synthetisiert und für die Hydrierung von Kohlendioxid zu Methan (Sabatier‐Reaktion) geprüft. Im Mittelpunkt der Untersuchungen standen Versuche zum Einfluss von Reaktionstemperatur und ‐druck. Als sehr geeignete Trägermaterialien erwiesen sich ZrO2 und γ‐Al2O3, die im Temperaturbereich von 300 – 400 °C hohe CO2‐ und H2‐Umsätze (70 – 80 %) und Methan‐Selektivitäten über 99 % erlauben. Im Gegensatz dazu führten TiO2‐ und SiO2‐basierte Katalysatoren fast ausschließlich zu CO und scheinen für die Reaktion nicht geeignet. Die Untersuchungen zur Druckabhängigkeit zeigten eindrucksvoll den Einfluss auf die Lage des chemischen Gleichgewichts. Die CO2‐ und H2‐Umsätze lagen an einem Ru/ZrO2‐Katalysator oberhalb 95 % und Methan wurde mit einer Selektivität von > 99,9 % gebildet.

On the kinetics of the methanation of carbon dioxide on coprecipitated NiAl(O)

“…Nevertheless, they are strongly needed for reactor design and optimization and also for a qualified comparison of different catalyst systems. In view of economic feasibility we focused on Ni based systems though Rh [9][10][11], Ru [12][13][14][15][16] and Pd [17,18] have also been reported as catalytically active. Table 1 gives an overview of published models.…”

Carbon Dioxide Reduction with Hydrogen on Carbon‐Nanotube‐Supported Catalysts under Supercritical Conditions

“…The advantage of the catalytic processes under supercritical conditions is the high throughput, i.e., the productivity of the catalyst expressed in terms of grams of CO 2 passed or converted per gram of the catalyst per hour. The gas‐phase tests described in the literature were performed in diluted gas mixtures, with H 2 or N 2 serving as diluents, including one of the best results reported by Martin and coworkers, who tested the Ni‐ and Ru‐containing catalysts (5 wt%) in CO 2 reduction with H 2 at 350–400 °C, 1–20 bar, a molar ratio of H 2 /CO 2 = 4:1, with a gas hourly space velocity 6000 h −1 . Also, the productivity was quite limited (about 0.2 g g −1 h −1 ).…”

“…The gas-phase tests described in the literature were performed in diluted gas mixtures, with H 2 or N 2 serving as diluents, including one of the best results reported by Martin and coworkers, who tested the Ni-and Ru-containing catalysts (5 wt%) in CO 2 reduction with H 2 at 350-400 C, 1-20 bar, a molar ratio of H 2 /CO 2 ¼ 4:1, with a gas hourly space velocity 6000 h À1 . [10] Also, the productivity was quite limited (about 0.2 g g À1 h À1 ). In our tests, the productivity reached 1.54 g g À1 h À1 , which is about 7-8 times higher compared with the literature data.…”

“…[8,9] Martin and coworkers studied Ni-and Ru-containing catalysts in CO 2 hydrogenation at 350-400 C, molar ratio of H 2 /CO 2 ¼ 4:1, with a gas hourly space velocity 6000 h À1 . [10] The Ru/ZrO 2 catalysts (Ru particle size of 4 nm) were much more active than Ni/ZrO 2 catalysts (Ni particle size of 20-30 nm). Methane yields above 70% were obtained at an atmospheric pressure, whereas at higher pressures the yields increased to 93% for Ni and 96% for Ru with the methane selectivity over 99.9%.…”

“…The catalysts of CO 2 methanation were discussed in the literature . Martin and coworkers studied Ni‐ and Ru‐containing catalysts in CO 2 hydrogenation at 350–400 °C, molar ratio of H 2 /CO 2 = 4:1, with a gas hourly space velocity 6000 h −1 . The Ru/ZrO 2 catalysts (Ru particle size of 4 nm) were much more active than Ni/ZrO 2 catalysts (Ni particle size of 20–30 nm).…”