Green Synthesis of Ni–Nb oxide Catalysts for Low‐Temperature Oxidative Dehydrogenation of Ethane

Abstract

The straightforward solid-state grinding of a mixture of Ni nitrate and Nb oxalate crystals led to, after mild calcination (T<400 °C), nanostructured Ni-Nb oxide composites. These new materials efficiently catalyzed the oxidative dehydrogenation (ODH) of ethane to ethylene at a relatively low temperature (T<300 °C). These catalysts appear to be much more stable than the corresponding composites prepared by other chemical methods; more than 90 % of their original intrinsic activity was retained after 50 h with time on-stream. Furthermore, the stability was much less affected by the Nb content than in composites prepared by classical "wet" syntheses. These materials, obtained in a solvent-free way, are thus promising green and sustainable alternatives to the current Ni-Nb candidates for the low-temperature ODH of ethane.

Optimizing Both Catalyst Preparation and Catalytic Behaviour for the Oxidative Dehydrogenation of Ethane of Ni–Sn–O Catalysts

“…A similar trend has been also proposed in the case of the promoted-or supported-NiO catalysts [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18], with NiO as the main crystalline phase, in which low variations in the selectivity to ethylene with the ethane conversion is observed (at least at ethane conversions lower than 30%). Moreover, a strong influence of the addition of various promoters on the nature of active sites has been observed where only few metal oxides have shown a positive promoter effect.…”

“…In fact, nickel oxide presents a low selectivity to ethylene (from 10 to 30% at conversion lower than 30%), depending on catalyst preparation procedure [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. Moreover, promoted [1][2][3][4][5][6][7][8][9][10][11][12][13] or supported [14][15][16][17][18] nickel oxide changes the catalytic behavior in terms of activity and selectivity. A clear example is observed in the case of Ni-W-O in which the reaction network for ethane ODH strongly changes depending on Ni/W atomic ratio [5]: i) parallel and consecutive reactions takes place (with the formation of ethylene, CO and CO2, and with overoxidation of ethylene) are observed over Ni-poor catalysts (in which Ni-tungstate is mainly observed); and ii) parallel reaction (with the formation of ethylene and CO2, and without overoxidation of ethylene) are observed over Ni-rich catalysts (in which NiO is mainly observed).…”

Ni–Ta–O mixed oxide catalysts for the low temperature oxidative dehydrogenation of ethane to ethylene

“…Compared with the SG synthesis, the SS method we report herein provides a simpler and faster preparation of the Ni-Ta oxide catalysts [16]. Solid-state mixing followed by calcination of the resulting mixture of nickel nitrate, tantalum ethoxide, and oxalic acid at 300°C yields the Ni-Ta oxide catalysts.…”

“…NiO is known to be very reactive and capable of activating ethane at moderate temperature (below 400°C) [13,14]. Furthermore, the physical and chemical properties of NiO can be modified and improved by doping with transition metals, such as Nb [15][16][17][18][19][20], Zr [21,22], W [23], the main group element Sn [24] or by supporting it on SiO 2 , Al 2 O 3 , ZrO 2 , and MgO [25][26][27][28][29]. The resulting NiO based materials deliver increased ethylene yield.…”

“…The authors prepared the Ni-Ta oxide catalysts by an evaporation method and did not vary the preparation despite the poor performance of this group of catalysts. Our recent study showed that the method of preparation of niobium doped nickel oxides as well as their Nb content had a critical impact on the resulting ethane ODH catalytic properties [15,16]. With this key information on the impact of catalyst preparation on performance, we decided to investigate the impact of various modes of preparation of Ni-Ta-O mixed metal oxides on ethane ODH performance.…”