Oxidative dehydrogenation of ethane: A study over the structure and robustness of Ni–W–O catalysts

• The preparation method influences the behavior of Ni–W–O catalysts.
• NiO + WOx nanocrystals are responsible for the high selectivity to ethylene.
• The presence of NiWO4 is detrimental as it involves the overoxidation of ethylene.
• In the absence of O2, NiO reduces to Ni0 and the catalytic performance changes.
• The reduced catalyst can be almost completely regenerated by air.

The robustness of one selected Ni–W–O catalyst has been studied in the oxidative dehydrogenation of ethane. This catalyst initially deactivates for the first 10 h online decreasing 15% of its catalytic activity compared to its initial stable catalytic activity. However from 10 to 60 h online the catalytic activity keeps almost stable. On the other hand, it has been shown that the Ni–W–O catalyst cannot tolerate an oxygen-free atmosphere (C2 and He) as nickel oxide is transformed into metallic nickel. Methane and hydrogen as well as abundant coke were formed on the surface of the catalyst in these O-free conditions. However a re-calcination in air leads to the removal of coke, the catalytic performance in the oxidative dehydrogenation of ethane being almost completely restored.Ni–W–O catalysts are active and selective in the oxidative dehydrogenation of ethane. However, their catalytic performance highly depends on the catalyst composition. At the present paper we have prepared Ni–W–O catalysts with an optimal W/(Ni + W) ratio using different procedures. It will be shown that the preparation method employed determines the Ni- and W-species formed in the catalysts and consequently the catalytic performance.