Effect of low loading of yttrium on Ni-based layered double hydroxides in CO2 reforming of CH4

Abstract

Ni/Al/Mg layered double hydroxides (LDHs) modified with low loading of yttrium (0.2 and 0.4 wt%) were used in dry reforming of methane at 700 °C. Physicochemical characterization, such as: X-ray fluorescence, N2 sorption, X-ray diffraction, temperature programmed reduction in H2, temperature programmed desorption of CO2, H2 chemisorption, thermogravimetry analysis coupled by mass spectrometry and Raman spectroscopy, showed that the introduction of low loadings of yttrium lead to a smaller Niº crystallite size, a decrease in reducibility of the nickel, and a decreased number of basic sites in the modified Ni/LDHs catalysts. The doping with 0.4 wt% of Y improves catalytic activity resulting in higher CH4 and CO2 conversions at 700 °C, i.e. ca. 84 % and ca. 87 %, respectively with no clear deactivation observed after 5 h run. The increase in CO2 conversion and a decrease of H2/CO ratio indicates that side reactions occurs during DRM.

On the effect of yttrium promotion on Ni-layered double hydroxides-derived catalysts for hydrogenation of CO2 to methane

“…The calculated M 2+ /M 3+ atomic ratios were fairly close to those assumed during the materials synthesis, indicating that the composition of LDHs may be easily controlled as reported before [74]. There are no significant difference regarding to BET surface area and pore volume of Ni-containing double-layered hydroxides-derived catalyst when the loading of yttrium is low (≤0.4%) compared with Y-free sample, only the average pore size decreases as the increase of yttrium at low loading of yttrium [44,47]. As described in the section before, the structural parameters showed that the yttrium loading up to 2.0 wt.% could result in the introduction of this metal into the periclase-like structure.…”

“…36.7, 43 and 62.5° are observed, which corresponds to mixed oxides obtained after thermal treatment of double-layered hydroxides [44,45,47]. Fig.…”

“…Another advantage of double layered hydroxides is that the incorporated cations are usually homogenously distributed due to their random arrangement in the brucite-like layers. Moreover, such materials exhibit basic properties, which are of great interest when used as catalysts for the reaction of CO 2 methanation [35,44,[46][47][48][49][50][51].…”

“…Yttrium had been reported in the literature as a promising dopant in methane dry reforming reaction (CO 2 + CH 4 = 2H 2 + 2CO) [44,47,[61][62][63][64][65][66]. The increased activity of the Ni-containing hyrotalcites was attributed to the enhanced dispersion of the active phase in comparison with the un-promoted materials [44,47,64].…”

“…Yttrium had been reported in the literature as a promising dopant in methane dry reforming reaction (CO 2 + CH 4 = 2H 2 + 2CO) [44,47,[61][62][63][64][65][66]. The increased activity of the Ni-containing hyrotalcites was attributed to the enhanced dispersion of the active phase in comparison with the un-promoted materials [44,47,64]. The stability of the Zr-containing catalysts in DRM reaction was also enhanced by the introduction of Y, which was assigned to the formation of a solid-solution ZrO 2 -Y 2 O 3 , leading to the increased reducibility of bulk NiO [45].…”