A Fresh Look at Ni-Based Catalysts for the Oxidative Dehydrogenation of Ethane

As shale oil deposits continue to yield large amounts of light paraffins, technologies must account for how to obtain routes for the production of light olefin feedstocks previously obtained through steam pyrolysis or cracking. A very important feedstock is ethylene, which has a market need of 150 million tons/year. Standard operating reaction conditions for obtaining ethylene often require enormous amounts of energy with operating temperatures higher than 900°C. Low temperature oxidative dehydrogenation not only operates at temperatures of 500°C or lower, but also introduces oxygen as a co-reagent for the conversion of ethane to ethylene.

Although many catalysts are viable for the oxidative dehydrogenation process, the most promising are metal-based oxides. Nickel based catalysts have shown great promise at low temperatures for conversion. These catalysts are sensitive to the structure of the nickel at the surface and metal-support interactions as well as the physical properties of the supports. We have also found that the amount of metal in the catalyst and the preparation method make a difference in yield of ethylene. Accepted conversion rates for ethane to ethylene are 1 kg ethylene/kg catalyst-hour. We aim to improve this conversion rate by optimizing the nickel based catalyst and finding new pathways for decreasing energy costs for the reaction.

In this study, we report the optimization of nickel based catalysts through i) support properties ii) dopants and additives and iii) operating parameters for the reaction. Our findings deconvolute the effect of support surface area and pore volume from acid/base properties. We also report on the effect of additives in light of the oxygen storage capacities of the catalysts. All reaction conditions for oxidative dehydrogenation were performed in the temperature range of 300-500°C. We also discuss the role and effect of co-feeds such as CO₂ as an additive for these reactions using a Ni-based catalyst. At higher temperatures, over-oxidation to CO₂ outcompetes the rate of ethylene formation, however, we can offset this through further catalyst optimization.