Nickel Particles Selectively Confined in the Mesoporous Channels of SBA-15 Yielding a Very Stable Catalyst for DRM Reaction

Abstract

A series of four Ni catalysts supported on SBA-15 and on a high SiO surface area have been prepared by modified impregnation (ImU) and deposition-precipitation (DP) methods. The catalysts have been extensively characterized, including in situ XAS (bulk sensitive) and XPS (surface sensitive) techniques, and their catalytic activities evaluated in the dry reforming reaction of methane (DRM). The combined use of XPS and XAS has allowed us to determine the location of nickel particles on each catalyst after reduction at high temperature (750 °C). Both Ni/SiO-DP and Ni/SBA-15-DP catalysts yield well-dispersed and homogeneous metallic phases mainly located in the mesoporosity of both supports. On the contrary, the Ni/SiO-ImU and Ni/SBA-15-ImU catalysts present a bimodal distribution of the reduced nickel phase, with nickel metallic particles located out and into the mesoporous structure of SiO or the SBA-15 channels. The Ni/SBA-15-DP catalyst was found the most stable and performing system, with a very low level of carbon deposition, about an order of magnitude lower than the equivalent ImU catalyst. This outstanding performance comes from the confinement of small and homogeneous nickel particles in the mesoporous channels of SBA-15, which, in strong interaction with the support, are resistant to sintering and coke deposition during the demanding reaction conditions of DRM.

Elucidating the Promotional Effect of Cerium in the Dry Reforming of Methane

“…Accordingly, an intimate contact between ceria and the active metal phase (coke promoter) should facilitate the process, and this can be addressed by using a high surface support [32–34] . On the other hand, a proper dispersion of the active metal phase has been shown to reduce graphitic coke formation by suppressing methane decomposition (the main source of coke at high temperatures), [35,36] a structure‐sensitive reaction which is favored in larger crystal [37,38] . In this sense, several approaches has been explored to prevent metal aggregation as MgO‐based solid‐solution catalysts, [39–41] mixed metal oxide materials (as perovskites), [42,43] or co‐impregnation with promoter oxides [44–46] …”

Aqueous nickel(II) hydroxycarbonate instead of nickel(0) colloids as precursors of stable Ni-silica based catalysts for the dry reforming of methane

“…In addition, the tomographic study showed that Ni 0 particles in Ni works [31][32], the preparation method described here, for the stabilization of nickel, is simpler (no need of promoters) and leads to smaller Ni NPs resulting in better catalytic performances. It has also to be noted that, among a lot of studies (more than 100 papers) dealing with Ni/silica catalysts in DRM, very few (see Table S1) used Ni silica-based catalysts working with a GHSV ≥ 144 L g -1 h -1 [33][34][35]. Hence, clearly Ni 0 aq.coll/S can be qualified as one of the best Ni/silica-based catalysts.…”

Light‐Driven Dry Reforming of Methane on Metal Catalysts

“…Fine‐size metal nanoparticles can be dispersed on the surface of thermally stable oxide powders to prevent the sintering caused by coalescence of contacting metal nanoparticles at high temperatures, improving the thermal stability of the catalyst. [ 44–46 ] The reduced possibility of sintering is ascribed to the good separation of individual metal nanoparticles on the support oxides and the low mobility of metals in the gaseous phase. Moreover, many oxide supports can exhibit Lewis acidity/basicity and even chemical reactivity to strongly interact with both reactant species and metal catalyst nanoparticles, resulting in a change of the catalytic activity.…”