You could say that the petrochemical world has long wondered when a plant using a catalytic reactor rather than a thermal steam cracker would produce ethylene from ethane. Now, such a plant has been announced for a site in the Marcellus shale region of West Virginia, but questions remain.
Ethylene is the largest volume petrochemical. It has been produced for the last eighty years by pumping a hydrocabon (ethane, propane, naphtha, etc) and steam through the reaction tubes inside a very hot furnace, where the hydrocarbon is “cracked” into different olefins (ethylene, propylene, etc.) and in the case of “heavier” feedstocks, into byproducts like isoprene, butadiene and aromatics. These byproducts often have a higher value than the ethylene, the main product, recovered in distillation units downstream of the furnace. In most parts of the world, naphtha is the most likely and available feedstock.
But in the Middle East and some other regions, now including the U.S., the best feedstock to make ethylene is ethane. Why have all plants up to now used a process equivalent to wielding a sledgehammer on a hydrocarbon molecule rather than a more “elegant” catalytic dehydrogenation process for such plants? The answer is that the reaction would make a certain amount of coke, which would deposit on the catalyst, requiring frequent regeneration, which is a nuisance. Some work over the years has shown that oxidative dehydrogenation may be the answer, though up to recently the yield of ethylene in these experiments has apparently not been high enough to consider this technology for commercialization.
The companies now hoping to build a $ 1.35 billion cracker using a catalytic ethane-to-ethylene process are Aither Chemicals and Mid-Atlantic Technology Research and Innovation (MATRIC) Center in South Charleston, W.Va. MATRIC is a research organization spun out of Dow Chemical/Union Carbide and supported by the state of West Virginia. (It’s interesting to note that Union Carbide in the 1920s was the first U.S. company to produce ethylene – by a thermal reaction.) The technology to be used for the new plant has not yet been disclosed, to my knowledge. Aither claims that its process uses 80% less energy than thermal cracking technology(!). (Chemical Week, Feb. 20, 2012 Page 7)
Reading between the lines, it appears that the consortium is hoping to bring into the deal a company with the ability to finance this very expensive project and to either build or attract plants that will convert the ethylene into commodity products like polyethylene or ethylene glycol.