Liquid CO2 as a Safe Solvent for Ozone-facilitated Selective Catalytic Oxidation of Methane and Light Alkanes
A safe method for the direct oxidation of methane and light alkanes to methanol and other oxygenates is disclosed. Selective catalytic oxidation can be a transformative technology for using increasing abundant natural gas, bio-gas and other sources of low value hydrocarbons via gas to liquid process.
Liquid CO2 is used as a solvent for the oxidation of methane and light alkanes by ozone in the presence of a catalyst. When methane is the feed, methanol is the main product. The use of liquid CO2 allows safe operation.
To learn more about the technology, you may view the published US Utility patent application (pdf) by downloading or view it online.
The process coverts low value feedstocks like methane to oxygenated products like methanol. These products can serve as a feedstock for fuels, polymers and other chemicals. Smaller scale plants can be located close to “stranded” hydrocarbon resources
How it works:
Ozone is highly reactive and can directly insert oxygen into highly stable carbon hydrogen bonds like those in methane. The reaction is difficult to control and over oxidation to CO2 and other by-products can occur. The metal catalyst mediates the reaction and approves selectivity. The liquid CO2 is a good solvent for ozone. It can suppress secondary reactions, prevent fires, and serve as a heat sink to reduce heat production in the process.
The key benefit is safe operation of a highly exothermic process involving flammable materials at higher yields than prior direct oxidation processes. A single step direct conversion can replace the currently used two-step process. The direct oxidation process would be more suitable for smaller scale plants.
Why it is better:
Prior efforts to develop direct oxidation processes have been hindered by safety concerns that required operation at very low conversion in dilute systems. The process replaces a complex two-step process with a single step.
The use of CO2 as solvent facilitates the ozonolysis of other chemicals like olelic acids. Ozonolysis is an important synthetic tool in the laboratory. This new technology can facilitate its safe use at larger scales.