Alkali and Alkali-Earth Metals Incorporation to Ni/USY Catalysts for CO2 Methanation: The Effect of the Metal Nature

• Published in: Processes Vol. 9; no. 10; p. 1846
• Main Authors: Bacariza, M. Carmen, Grilo, Cláudia, Teixeira, Paula, Lopes, José M., Henriques, Carlos
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01.10.2021
• Subjects: Adsorption; Alkali metals; Bimetals; Calcium carbonate; Carbon dioxide; Catalysts; Earth; Magnesium; Metal compounds; Metal oxides; Metals; Methanation; Methane; Mixed oxides; Nickel; Sensors; Spectrum analysis; Structural damage; Zeolites
• ISSN: 2227-9717; 2227-9717
• DOI: 10.3390/pr9101846

CO2 methanation is typically carried out using Ni-supported catalysts containing promoters such as alkali or alkali-earth metals to improve their properties. In this work, bimetallic Ni-based USY zeolite catalysts containing alkali (Li, K and Cs) and alkali-earth (Mg, Ca) metal compounds were prepared using the same conditions (15 wt% of metals; co-impregnation), characterized by N2 sorption, XRD, TGA, CO2 adsorption–desorption, DRS UV-Vis and H2-TPR, and finally applied in CO2 methanation reaction (86,100 mL h−1 g−1, PCO2 = 0.16 bar, H2:CO2 = 4:1). For each group, the effects of the second metal nature on the properties and performances were assessed. Alkali metals incorporation induced considerably low catalytic performances (CH4 yields < 26%), attributed to their negative impact on zeolite structure preservation. On the contrary, alkali-earth metal-containing catalysts exhibited lower structural damage. However, the formation of Ni-Mg mixed oxides in Ni-Mg/USY catalyst and CaCO3 during the reaction in Ni-Ca/USY sample could explain their performances, similar or lower than those obtained for Ni/USY catalyst. Among the studied metals, calcium was identified as the most interesting (CH4 yield of 65% at 415 °C), which was ascribed to the slight improvement of the Ni0 dispersion.