Novel Process Enhances Thermal Conversion of Shale Gas to Diesel

Achievement date: 

CISTAR-ERCresearchers have discovered a novel process for enhancing thermal, free-radical conversion of olefins to diesel fuels in studies funded by the Center for Innovative and Strategic Transformation of Alkane Resources (CISTAR), an NSF-funded Engineering Research Center (ERC) based at Purdue University.

While methane is the largest component in shale gas, there are also significant amounts of ethane and propane, which could potentially be converted to transportation fuels that are currently produced from petroleum. Ethane and propane are first converted to olefins, which are subsequently futher reacted to locally produce transportation fuels. The new CISTAR process can expand the use of shale gas by conversion of ethylene and propylene to high cetane diesel fuel. The new process operation requires less capital investment and lower energy use when compared to existing technologies.

Several U.S. refineries in the 1920s and 1930s used thermal, non-catalytic conversions of light olefins in the production of motor fuels. However, the resulting fuels had relatively low octane levels and required harsh operating conditions, ultimately giving way to solid-acid catalytic processes.

CISTAR researchers at Purdue have demonstrated at the laboratory scale a thermal olefin conversion process selective for linear terminal olefin products for the second step of a two-step process operation needed to convert abundant US shale hydrocarbons to liquid transportation fuels. Thermal, non-catalytic, free-radical ethylene oligomerization at temperatures between 300oC and 500 oC and at pressures from 1.5 bar to 45 bar produced linearly terminal olefin products with only minor yields of side-products and coke. This process can be potentially applied to both large- and small-scale applications near the shale gas wellhead. As natural gas production increases, there is a potential $20 billion market for conversion of ethane, propane, and butane to liquid fuels. A patent on this technology has been licensed by one of the CISTAR industrial partners.