Low Temperature Partial Oxidation of Methane over Bimetallic Nickel‐f Block Element Oxide Nanocatalysts

Abstract

The partial oxidation of methane (POM) was studied over bimetallic nickel-f block element oxide nanocatalysts prepared by a modified sol-gel method. They proved to be active (conversion of methane, 50-70%) at a relatively low temperatures (550 and 650 8C) and highly selective towards synthesis gas production (selectivity, H 2 60-90% and CO 50-80%). The activity and selectivity depend on the surface basicity and size of the bimetallic oxide nanoparticles: lower particle size and higher basicity, enhanced activity and selectivity to synthesis gas. Catalysts reducibility seems as well to promote their activity and selectivity. The bimetallic nickel-gadolinium and nickel-thorium oxide nanocatalysts proved to be more active and selective towards synthesis gas production than a commercial platinum supported catalyst (5 wt% Pt/Al 2 O 3 ) or other bimetallic nickel oxide catalysts obtained by a different high temperature preparation route, which stresses the advantage of the preparation method. The bimetallic nickel-f block element oxide nanocatalysts present also remarkable long-term stability and an unusual low deposition of carbon, which is a major advantage, especially when compared to other nickel-based catalysts reported for POM. Such a behavior was attributed to the lanthanide or actinide oxide phases that appear to play an important role on the catalysts stability. A number of Ni-based catalysts, for example, NiO-MgO, [7] NiO-CaO, [8] NiO-lanthanide oxides [9] or nickel-lanthanum-based catalysts, [10] NiO/ Al 2 O 3 [11] and nickel actinides [12] showed to be as attractive as the noble metal catalysts due to their lower cost and higher activity and selectivity. However, Ni-based catalysts suffer deactivation due to low metal sintering and carbon deposition (coke formation through Boudouard reaction), as its major problem. [5c,13]

Methanation of CO2 Over Bimetallic Ni–5f Block Element (Th, U) Oxides

“…It is known from the literature that the addition of rare earth oxides inhibits catalysts deactivation. This fact can explain our nickel catalysts enhanced stability …”

“…In our group, the synthesis of bimetallic oxides containing f ‐block elements (lanthanide and actinides) with other metals such as copper, nickel or calcium and the pursuit of catalytic applications to the valorization of primary pollutants are important goals that continue to be studied . In particular, nickel‐5 f elements oxides proved to be very active for the partial oxidation of methane (POM) and formation of syngas, whereas those containing calcium were very active for the formation of C 2 hydrocarbons (ethane, ethylene) , , , . Bimetallic oxides nickel‐based catalysts containing 4 f or 5 f block elements show also an unusual long stability in the gaseous stream that is a considerable advantage .…”

Synthesis of Terephthalic Acid by p‐Cymene Oxidation using Oxygen: Toward a More Sustainable Production of Bio‐Polyethylene Terephthalate

“…The good activity of Mn/Fe/O is in agreement with our previous study, in which we demonstrated that a mixture of Mn III and Mn IV coexists with a hematite phase. Also, as already reported, the surface basicity improved the catalyst oxidant behavior (Figure ) . Moreover, charge‐transfer transitions between iron d electrons and the manganese oxide conduction or valence bands were evidenced in the UV/Vis spectra by the redshift of the high energy band for Mn/Fe/O compared with that for Mn 2 O 3 (Figure S3).…”

Selective oxidation of 5-hydroxymethyl furfural over non-precious metal heterogeneous catalysts

“…Recent achievements emphasized that the surface basicity improve the catalyst's oxidant strength [53]. In order to confirm this, the catalysts basicity has been determined and correlated to the catalytic performances.…”