Syngas to gasoline plus
Syngas to gasoline plus (STG+) is a thermochemical process to convert natural gas, other gaseous hydrocarbons or gasified biomass into drop-in fuels, such as gasoline, diesel fuel or jet fuel, and organic solvents.
This process follows four principal steps in one continuous integrated loop, comprising four fixed bed reactors in a series in which a syngas is converted to synthetic fuels. The steps for producing high-octane synthetic gasoline are as follows:
The STG+ process uses standard catalysts similar to those used in other gas to liquids technologies, specifically in methanol to gasoline processes. Methanol to gasoline processes favor molecular size- and shape-selective zeolite catalysts, and the STG+ process also utilizes commercially available shape-selective catalysts, such as ZSM-5.
According to Primus Green Energy, the STG+ process converts approximately one MMBtu of natural gas into more than five gallons of 90+-octane gasoline. One gallon of gasoline contains 120000 to 125000 BTU, making this process about 60% efficient (40% loss of energy).
As is the case with other gas to liquids processes, STG+ utilizes syngas produced via other technologies as a feedstock. This syngas can be produced through several commercially available technologies and from a wide variety of feedstocks, including natural gas, biomass and municipal solid waste.
Natural gas and other methane-rich gases, including those produced from municipal waste, are converted into syngas through methane reforming technologies such as steam methane reforming and auto-thermal reforming.
Biomass gasification technologies are less established, though several systems being developed utilize fixed bed or fluidized bed reactors.
Other technologies for syngas to liquid fuels synthesis include the Fischer-Tropsch process and the methanol to gasoline processes.
Research conducted at Princeton University indicates that methanol to gasoline processes are consistently more cost-effective, both in capital cost and overall cost, than the Fischer-Tropsch process at small, medium and large scales. Preliminary studies suggest that the STG+ process is more energetically efficient and the highest yielding methanol to gasoline process.
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