The Role of Alkali and Alkaline Earth Metals in the CO2 Methanation Reaction and the Combined Capture and Methanation of CO2

Abstract

CO2 methanation has great potential for the better utilization of existing carbon resources via the transformation of spent carbon (CO2) to synthetic natural gas (CH4). Alkali and alkaline earth metals can serve both as promoters for methanation catalysts and as adsorbent phases upon the combined capture and methanation of CO2. Their promotion effect during methanation of carbon dioxide mainly relies on their ability to generate new basic sites on the surface of metal oxide supports that favour CO2 chemisorption and activation. However, suppression of methanation activity can also occur under certain conditions. Regarding the combined CO2 capture and methanation process, the development of novel dual-function materials (DFMs) that incorporate both adsorption and methanation functions has opened a new pathway towards the utilization of carbon dioxide emitted from point sources. The sorption and catalytically active phases on these types of materials are crucial parameters influencing their performance and stability and thus, great efforts have been undertaken for their optimization. In this review, we present some of the most recent works on the development of alkali and alkaline earth metal promoted CO2 methanation catalysts, as well as DFMs for the combined capture and methanation of CO2.

Bimetallic Ni-Based Catalysts for CO2 Methanation: A Review

“…The activity of Ni-based catalysts can be further improved via modification of the metal oxide supports. For example, alkali and alkaline earth metals [13], transition metals [6] and rare-earth metals [14] can be used as promoters that modify the physicochemical properties of metal oxide supports. In some cases, these ions can enter the lattice of the metal oxide supports (e.g., Ca 2+ ions in CeO 2 and ZrO 2 lattices) [15], or form segregated metal oxide phases supported on the support surface (e.g., La 2 O 3 , CeO 2 and MnO x in Al 2 O 3 ) [16].…”

“…Such modifications can lead to an increase in support basicity, so that the initial step of CO 2 chemisorption step is accelerated, or to an increase in the active metal dispersion [17]. In most cases, the low-temperature activity and stability of Ni-based catalysts is enhanced following modification of the metal oxide supports [13,14,16].…”

Adsorption of Hydrogen Sulfide at Low Temperatures Using an Industrial Molecular Sieve: An Experimental and Theoretical Study

“… 3 − 7 Biogas upgrading for increasing its calorific value involves specific steps, starting with H 2 O condensation, desulfurization (e.g., removal of toxic and corrosive H 2 S), and CO 2 sequestration based on different universally established and commonly used technologies including physisorption and/or chemisorption, membrane or cryogenic separation, and by chemical or biological treatment. 3 , 8 − 10 …”

The Active Sites Engineering of Catalysts for CO2 Activation and Conversion

“…[ 13 ] Some alkaline earth metals have been used to promote the CO 2 hydrogenation to methane due to their features of low cost, abundant source, and effective facilitation. [ 111 ] Cimino et al investigated the roles of alkaline metals (Li, Na, and K) and precursor salts on 1%Ru/Al 2 O 3 for CO 2 methanation. Among these catalysts with different alkaline metals, Li−Ru/Al exhibited the best CO 2 hydrogenation activity.…”