Ethylene has historically been the most important petrochemical building block: a highly reactive molecule made by the high temperature cracking of hydrocarbons ranging from ethane to heavy gas liquids. This is actually not a specific process in that it produces a number of other olefins and aromatics in different amounts and concentrations, depending on the hydrocarbon fed to the cracking furnace: mostly ethylene when cracking ethane, a complex mixture of ethylene, propylene, higher olefins and diolefins, benzene and other aromatics when cracking naphthas or gas oils. These “byproducts” of the cracking process are, however, quite valuable as well. And this has been the heart of the petrochemical industry since the 1950’s. Many researchers tried to find a more specific, more “elegant” way to make ethylene but up to recently have been unsuccessful.
Research by the UOP division of Honeywell and by the Chinese has now yielded a brand new way to make ethylene with fewer byproducts and using a non-hydrocarbon feedstock, namely methanol! This so-called MTO (methanol-to-olefin) technology is now commercial and is starting to produce large quantities of ethylene in China. (Chemical and Engineering News, August 31, 2015). And the methanol itself is made from coal, thus helping that country in its quest to be less dependent on importing hydrocarbons for both fuel and chemical uses.
The breakthrough technology that led to making a molecule looking like this C=C from a molecule with the formula CH3OH (methanol) involves the use of silicoaluminum molecular sieves as catalysts and a very complex mechanism. As far as I can determine, the research was done independently in the U.S. and China.
Methanol has been produced from many feedstocks including coal. It involves the production of “synthesis gas” containing hydrogen and carbon monoxide. with carbon dioxide and water as a byproduct. Of interest is the fact that the carbon dioxide comes out of the system in concentrated form, making it easy to recover it for use or storing it in caverns to avoid letting the GHG into the atmosphere.
Making ethylene this way costs more than producing it from hydrocarbons. But that may not be the case in China, depending on how it prices coal versus naphtha and how it treats capital charges.