Methanation of CO₂ and CO by (Ni,Mg,Al)-Hydrotalcite-Derived and Related Catalysts with Varied Magnesium and Aluminum Oxide Contents

Abstract

In the present study, the influence of the composition of Lewis basic (Mg,Al)O x mixed oxide supports on CO 2 and CO methanation performance of (Ni,Mg,Al)-hydrotalcite-derived catalysts is investigated. The hydrotalcite-derived and related precursors are synthesized by pH-controlled coprecipitation, calcination, and subsequent reduction. The catalysts with different supports prove suitability for CO 2 and for CO methanation but display significant differences in respect to the temperature sensitivity of the reactions. The influence of the systematically varied support composition was studied by kinetic measurements, X-ray photoelectron spectroscopy (XPS), and in situ diffuse reflectance infrared Fourier transform (DRIFTS). Performance differences between CO 2 and CO methanation were investigated for three different catalyst compositions. Different adsorption patterns in the DRIFTS measurements for these catalysts allow us to assign the increase in performance in the presence of magnesium oxide primarily to the enhancement of CO 2 adsorption on the catalyst support. Temperature-dependent DRIFTS measurements display a correlation between the ratio of formate to carbonyl species on the catalyst surface and the activity of the catalyst in the case of magnesiumcontaining catalysts. The result suggests the role of CO as a key intermediate for CO 2 methanation for magnesium-containing nickel hydrotalcite-derived catalysts. XPS measurements demonstrate that the magnesium content significantly affects the reducibility in the precursor material to generate the active component.

Catalytically transforming cellulose into methane under natural solar irradiation

“…4a), suggesting dehydration during the heating process. 39 There was a negligible vibration band (2300–2400 cm −1 ) belonging to CO 2 during the heating process, indicating that almost no CO 2 was generated in the catalytic system. 40 At about 330 °C, the C–H stretch vibration band at 3020 cm −1 and C–H bending vibration band at 1310 cm −1 appeared, suggesting the generation of alkane hydrocarbons such as CH 4 .…”

“…40 At about 330 °C, the C-H stretch vibration band at 3020 cm −1 and C-H bending vibration band at 1310 cm −1 appeared, suggesting the generation of alkane hydrocarbons such as CH 4 . [39][40][41][42] Along with the increase of temperature, the intensity of the two peaks became stronger, indicating that more alkane gas was generated in the sealed compartment (Fig. 4b).…”

Highly Active Ce- and Mg-Promoted Ni Catalysts Supported on Cellulose-Derived Carbon for Low-Temperature CO2 Methanation

“…These, at the nickel−support interface, can increase the activation of CO* via, e.g., the addition of H* from the support. 58 On the other side, although Mg enhances the activity and stability of the catalyst, 61,62 high amounts of Mg could hinder the NiO reduction as a result of a higher interaction between NiO and MgO, 63 as the TPR results suggest (Figure 3). Anyway, the presence of both O mobile from CeO 2 and OH − species adsorbed on the MgO surface seem to be beneficial to the formation and removal of water during the reaction.…”

Effect of Fe and La on the Performance of NiMgAl HT-Derived Catalysts in the Methanation of CO2 and Biogas

“…Considering that the reduction temperature of Mg-containing HT-derived catalysts is a key parameter that modifies the activity, 27 a preliminary study on the effect of the reduction temperature on the activity and selectivity of the Ni25MgAl catalyst is performed. Different pretreatment temperatures are reported in the literature, e.g., 500−600 °C, 27,30 700 °C, 29,34 up to 900 °C, 23,24 which could be dependent on the composition of the catalyst (i.e., Ni and Mg loading) and the decomposition temperature of HT compounds. In this work, the study is focused on two temperatures: 600 and 750 °C.…”