Promotional effect of magnesium oxide for a stable nickel-based catalyst in dry reforming of methane

Abstract

The generation of synthesis gas (hydrogen and carbon monoxide mixture) from two global warming gases of carbon dioxide and methane via dry reforming is environmentally crucial and for the chemical industry as well. Herein, magnesium-promoted NiO supported on mesoporous zirconia, 5Ni/xMg-ZrO 2 (x = 0, 3, 5, 7 wt%) were prepared by wet impregnation method and then were tested for syngas production via dry reforming of methane. The reaction temperature at 800 °C was found more catalytically active than that at 700 °C due to the endothermic feature of reaction which promotes efficient CH 4 catalytic decomposition over Ni and Ni-Zr interface as confirmed by CH 4-TSPR experiment. NiO-MgO solid solution interacted with ZrO 2 support was found crucial and the reason for high CH 4 and co 2 conversions. The highest catalyst stability of the 5Ni/3Mg-ZrO 2 catalyst was explained by the ability of CO 2 to partially oxidize the carbon deposit over the surface of the catalyst. A mole ratio of hydrogen to carbon monoxide near unity (H 2 /CO ~ 1) was obtained over 5Ni/ZrO 2 and 5Ni/5Mg-ZrO 2 , implying the important role of basic sites. Our approach opens doors for designing cheap and stable dry reforming catalysts from two potent greenhouse gases which could be of great interest for many industrial applications, including syngas production and other value-added chemicals. The production of syngas (a mixture of H 2 and CO) through dry reforming of methane is an excellent strategy to reduce the global warming effects of carbon dioxide (CO 2) and methane (CH 4). Noble metals such as palladium (Pd), platinum (Pt), and ruthenium (Ru) have been used for this purpose, but costly precursors and instability of catalyst, at high reaction temperature around 800 °C, have limited their application 1. On the other hand, costeffective nickel (Ni) metal, supported on an appropriate supports such as alumina 2 , mesoporous silicates 3-7 , and zirconia 8-10 , has been found to withstand at this reaction temperature (800 °C). In this context, many researchers have followed the surface modification methodology to optimise the catalyst performance because Ni-based catalyst is also prone to deactivation. The first series of modifications were carried out over alumina supports

Role of Ca, Cr, Ga and Gd promotor over lanthana‐zirconia–supported Ni catalyst towards H2‐rich syngas production through dry reforming of methane

“…A deep literature report on a series of the catalyst system in terms of CH 4 conversion, CO 2 conversion, H 2 /CO ratio on different reaction conditions is shown in Table 12,15,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47 . Potassium (K) promotional addition was marked for increasing the mesoporosity and reducibility of the catalyst, 41 Na addition for raising the basicity as well as the formation of strong interacting Ni species (NiO x H y ), 42 Ba addition for the formation of barium zirconate which stabilizes the NiO x species strongly over the surface against agglomeration 43 and Mg addition for increasing the basicity as well as reducible NiO‐MgO solid solution in favour of DRM 48 44 Al and Mn (1:1) had optimized Ni size, high basicity and high adsorbed oxygen species 45 .…”

“…12,15,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47 Potassium (K) promotional addition was marked for increasing the mesoporosity and reducibility of the catalyst, 41 Na addition for raising the basicity as well as the formation of strong interacting Ni species (NiO x H y ), 42 Ba addition for the formation of barium zirconate which stabilizes the NiO x species strongly over the surface against agglomeration 43 and Mg addition for increasing the basicity as well as reducible NiO-MgO solid solution in favour of DRM. 48 Mg-Al (4:1) promoter brought dispersed small size NiO, strong metal-support interaction, high reducibility and high surface area, 44 Al and Mn (1:1) had optimized Ni size, high basicity and high adsorbed oxygen species. 45 Chromium was found to enhance CO 2 absorption over the surface.…”

Barium-Promoted Yttria–Zirconia-Supported Ni Catalyst for Hydrogen Production via the Dry Reforming of Methane: Role of Barium in the Phase Stabilization of Cubic ZrO2

“… 13 Furthermore, the addition of a promoter over supported Ni catalysts had brought about major physiochemical changes over the catalyst surface in favor of DRM. In brief, Mg incorporation added alkalinity to the catalyst system, 2 , 14 − 17 Sr boosted Lewis basicity, 18 Yb brought about a high edge of reducibilty, 19 Sc induced basicity and a metal–support interaction, 20 W stabilized the NiO phase and modified the redox behavior, 8 , 21 , 22 Ce or Y advanced lattice ion mobility together with reducibility, 23 − 39 and B or La induced carbon gasification (through B–OH species and La 2 O 2 CO 3 formation, respectively). 40 − 46 Likewise, the addition of Sm, Gd, or Mn–Al (equal proportions) optimized the Ni size and enhanced the metal–support interaction.…”

“…In this context, the dry reforming of methane (DRM) is a potential and viable option because it yields hydrogen from the conversion of two major greenhouse gases (i.e., CH 4 and CO 2 ). Catalysts based on noble metals have been reported to be effective for DRM. − The total methane dissociation energy among the transition metals was found to follow the order Ni < Pd = Pt, so the experimental order of methane conversion was observed to be Ni > Pd = Pt . Among Ni and Co, Gallego et al found that the electronic configuration of Ni in Ni–CH 4 is s 0.54 d 9.42 (with respect to the d 8 s 2 electronic configuration of metallic Ni), indicating smaller steric repulsion between a closed shell of Ni and CH 4 .…”

Optimizing MgO Content for Boosting γ-Al2O3-Supported Ni Catalyst in Dry Reforming of Methane

“…They found that the potent interaction of NiO-MgO solid solution with the ZrO2 support was essential for obtaining high conversions of both methane and carbon dioxide. Furthermore, over their mixture of metal oxides, carbon dioxide functioned as a soft oxidizing for surface coke, entailing the stability of catalytic performance [16]. Karam et al found the optimum loading of MgO was in the range of 5-10 wt.…”