A new class of novel catalysts was prepared with high selectivity for the conversion ethane to ethylene. The invented catalyst could enable a new oxidative dehydrogenation process that would waste less carbon and require less energy than current methods of ethylene production.
The catalyst consists of surface-modified transition metal oxide nanorods. The activity and selectivity can be tuned by controlling the amount of modifier. The modifier forms a mesoporous coating without altering the bulk metal oxide structure.
The catalyst coverts a low value feedstock, ethane, to ethylene. Ethylene is one of the most important chemical building blocks with over 200 million tons produced each year. It is used to prepare a wide variety of polymers including polyethylene and polystyrene.
Oxidative dehydrogenation involves the reaction of oxygen with a hydrocarbon under controlled conditions that stop the oxidation before the formation of carbon monoxide and carbon dioxide. In the case of ethane, two hydrogens are removed to produce ethylene, a two-carbon compound that contains a double bond between the carbons. A catalyst is used to allow the reaction to occur at lower temperatures. This limits the undesired production of coke and complete oxidation. The reaction couples the heat producing oxidation of hydrogen with the dehydrogenation of ethane that requires a high input of energy. The use of ethane as a starting material and milder conditions also reduces the number of different bi-products formed simplifying the separation process.
Uncatalyzed steam cracking is currently used to produce over 90% of world's ethylene. Steam cracking is very energy inefficient and results in the loss of carbon as coke and other undesired products. The cracking plants require frequent maintenance. Catalysts for the oxidative dehydrogenation reaction are of great interest since this process is more selective and requires less energy input.
The doped catalysts are highly selective and produce less carbon oxides than other oxidative dehydrogenation catalysts. The catalysts are made using low cost metals and are more stable than other high selectivity catalysts.
The doped metal oxides can catalyze other selective oxidation reactions. The modification method should be adaptable to other metal oxide catalysts.