Search

Dual function materials (DFMs) for CO 2 capture and conversion couple the endothermic CO 2 desorption step of a traditional adsorbent with the exothermic hydrogenation of CO 2 over a catalyst in a unique way; a single reactor operating at an isothermal temperature (320 °C) and pressure (1 atm) can capture CO 2 from flue gas, and release it as methane upon exposure to renewable hydrogen. This combined CO 2 capture and utilization eliminates the energy intensive CO 2 desorption step associated with conventional CO 2 capture systems as well as avoiding the problem of transporting concentrated CO 2 to another site for storage or utilization. Here DFMs containing Rh and dispersed CaO have been developed (>1% Rh 10% CaO/γ-Al 2 O 3 ) which have improved performance compared to the 5% Ru 10% CaO/γ-Al 2 O 3 DFM (0.50 g-mol CH 4 /kg DFM) developed previously. Ruthenium remains the catalyst of choice due to its lower price and excellent low temperature performance. The role of CO 2 adsorption capacity on the final methanation capacity of the DFM has also been investigated by testing several new sorbents. Two novel DFM compositions are reported here (5% Ru 10% K 2 CO 3 /Al 2 O 3 and 5% Ru 10% Na 2 CO 3 /Al 2 O 3 ) both of which have much greater methanation capacities (0.91 and 1.05 g-mol CH 4 /kg DFM) compared to the previous 5% Ru 10% CaO/γ-Al 2 O 3 DFM. [ABSTRACT FROM AUTHOR]

Kinetics of CO 2 hydrogenation over a 10% Ru/γ-Al 2 O 3 catalyst were investigated using thermogravimetric analysis and a differential reactor approach at atmospheric pressure and 230–245 °C. The data is consistent with an Eley–Rideal mechanism where H 2 gas reacts with adsorbed CO 2 species. Activation energy, pre-exponential factor and reaction orders with respect to CO 2 , H 2 , CH 4 , and H 2 O were determined to develop an empirical rate equation. Methane was the only hydrocarbon product observed during CO 2 hydrogenation. The activation energy was found to be 66.1 kJ/g-mole CH 4 . The reaction order for H 2 was 0.88 and for CO 2 0.34. Product reaction orders were essentially zero. This work is part of a larger study related to capture and conversion of CO 2 to synthetic natural gas. [ABSTRACT FROM AUTHOR]

The accumulation of CO 2 emissions in the atmosphere due to industrialization is being held responsible for climate change with increasing certainty by the scientific community. In order to prevent its further accumulation in the atmosphere, CO 2 must be captured for storage or converted to useful products. Current materials and processes for CO 2 capture are energy intensive. We report a feasibility study of dual function materials (DFM), which capture CO 2 from an emission source and at the same temperature (320 °C) in the same reactor convert it to synthetic natural gas, requiring no additional heat input. The DFM consists of Ru as methanation catalyst and nano dispersed CaO as CO 2 adsorbent, both supported on a porous γ-Al 2 O 3 carrier. A spillover process drives CO 2 from the sorbent to the Ru sites where methanation occurs using stored H 2 from excess renewable power. This approach utilizes flue gas sensible heat and eliminates the current energy intensive and corrosive capture and storage processes without having to transport captured CO 2 or add external heat. [ABSTRACT FROM AUTHOR]

[Display omitted] • NiRu/CeO 2 -Al 2 O 3 and NiRu/Ce 0.5 Zr 0.5 O 2 were tested in three CO 2 gas-phase reactions. • NiRu/CeAl showed better coke resistance in dry reforming of methane (DRM). • Equilibrium CO 2 conversion was reached at 350 °C for NiRu/CeAl in CO 2 methanation. • NiRu/CeAl exhibited impressive stability in CO 2 hydrogenation reactions and DRM. Advanced catalytic materials able to catalyse more than one reaction efficiently are needed within the CO 2 utilisation schemes to benefit from end-products flexibility. In this study, the combination of Ni and Ru (15 and 1 wt%, respectively) was tested in three reactions, i.e. dry reforming of methane (DRM), reverse water–gas shift (RWGS) and CO 2 methanation. A stability experiment with one cycle of CO 2 methanation-RWGS-DRM was carried out. Outstanding stability was revealed for the CO 2 hydrogenation reactions and as regards the DRM, coke formation started after 10 h on stream. Overall, this research showcases that a multicomponent Ni-Ru/CeO 2 -Al 2 O 3 catalyst is an unprecedent versatile system for gas phase CO 2 recycling. Beyond its excellent performance, our switchable catalyst allows a fine control of end-products selectivity. [ABSTRACT FROM AUTHOR]