Magnesium as Promoter of CO₂ Methanation on Ni-Based USY Zeolites

Abstract

CO2 methanation was studied over Ni-Mg-USY zeolite catalysts. Mg was added by incipient wetness impregnation and ion-exchange. Whatever the Mg incorporation method used, Mg is able to improve the performances of the Ni-zeolite catalysts. Magnesium impregnation at lower contents (below 2.5%) over a 5%Ni/zeolite leads to an enhancement of the CO2 conversion into methane of 15% at 350-450ºC, probably due to the induced increase of the Ni particles dispersion, as well as to the possible activation of CO2 on the defects present on the MgO surface. At higher Mg contents, the stronger interaction between Ni and Mg oxides, leading to the formation of NiO-MgO solid solutions, seem to reduce the reducibility of the Ni species, decreasing the amount of nickel active sites available, and, so, the catalytic performances. Furthermore, important improvements of the catalytic performances (CO2 conversion and CH4 selectivity increased around 20% at 350-450ºC) were also found for the Mg-exchanged 5%Ni/zeolite. The results are comparable to those obtained by impregnation, but lower Mg contents are required. The enhanced activation of CO2 on Mg 2+ , the more dispersed Ni particles on the support, as well as the enhanced Ni reducibility when compared to the impregnated catalysts, can explain the observed results. The beneficial effect of the Mg addition both by impregnation and ion-exchange was also observed for samples containing higher amounts of Ni, the best sample remaining stable after 10h under reaction conditions. Thus, Mg could be an interesting promoter for the CO2 methanation over Ni-zeolite catalysts.

Tuning Zeolite Properties towards CO2 Methanation: An Overview

“…Regarding bimetallic catalysts , Bacariza et al . studied the effect of Mg incorporation to Ni/USY zeolites and found out that 1–3 wt.% Mg impregnation over a 5 %Ni/USY zeolite promotes Ni 0 dispersion, CO 2 adsorption and, consequently, CH 4 yields.…”

Ni‐Ce/Zeolites for CO2 Hydrogenation to CH4: Effect of the Metal Incorporation Order

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a] InÞsG raÅa, [b] JosØ M. Lopes, [a] andC arlosH enriques* [a] Introduction CO 2 methanation, as af orm of alleviating CO 2 emissions, has been the focus of much attention in the last few years, with thermal, photocatalytic,e lectrochemical, or even plasma assisted processes being used. [44][45][46][47][48][49] Amongt he different supports used, zeolitesh ave been revealed to be interesting materials, as their properties (e.g.,S i/ Al ratio, compensating cation) can be easily modified to meet the requirements of the reaction.Ni-basedu ltrastable Yz eolites (USY) have been appliedt o the CO 2 methanation reaction, with very promising results. [44][45][46][47][48][49] Amongt he different supports used, zeolitesh ave been revealed to be interesting materials, as their properties (e.g.,S i/ Al ratio, compensating cation) can be easily modified to meet the requirements of the reaction.

Ni-basedu ltrastable Yz eolites (USY) have been appliedt o the CO 2 methanation reaction, with very promising results.

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“…[1][2][3][4][5][6] Ni and Ru-based materials have been commonly used for this reaction, on different supports, such as Al 2 O 3 , [7][8][9][10][11][12][13][14][15] SiO 2 , [16][17][18][19][20] Ce and Zr oxides, [21][22][23][24][25][26][27][28] hydrotalcites and hydrotalcite-derived materials, [21,[29][30][31][32] carbon nanotubes, [33][34][35][36][37] mesoporous materials, [38][39][40][41][42][43] and zeolites. [44][45][46][47][48][49] In these studies, changes to the metal incorporation method (impregn...…”

“…[44][45][46][47][48][49] In these studies, changes to the metal incorporation method (impregnation or ion-exchange), the preparation conditions, the type of compensating cation, and the Si/Al ratio have been investigated to try to obtain an optimized catalyst formulation. [44][45][46][47][48][49] In these studies, changes to the metal incorporation method (impregnation or ion-exchange), the preparation conditions, the type of compensating cation, and the Si/Al ratio have been investigated to try to obtain an optimized catalyst formulation.…”

“…[44,[47][48][49] One of the most favorable promoters used in these catalysts is cerium, in the form of CeO 2 . [44,[47][48][49] One of the most favorable promoters used in these catalysts is cerium, in the form of CeO 2 .…”