The successful scale-up of a commercially-ready process for producing fuels from natural gas represents another key milestone in our strategy. We have already demonstrated how our technology can be employed to produce gasoline, an achievement that paves the way for first commercial facilities producing liquid fuels in the 2017 timeframe.

—Siluria CEO Ed Dineen

At commercial scale, Siluria’s process will enable refiners and fuel manufacturers to produce transportation fuels that cost considerably less than today’s petroleum-based fuels, while reducing overall emissions, NO_x, sulfur and particulate matter, the company said.

Fuels made with Siluria’s processes are also compatible with existing vehicles, pipelines and other infrastructure and can be integrated into global supply chains.

Earlier this year, Siluria announced that it will build an OCM demonstration plant at Braskem’s site in La Porte, Texas. Braskem is one of the leading producers of ethylene and plastics in the Americas. Siluria and Braskem have also entered into a relationship to explore commercialization of this technology. The OCM demonstration plant will begin operations later this year. (Earlier post.)

Siluria’s Hayward ETL facility and the La Porte OCM demonstration plant are the last scale-up steps prior to full commercialization of Siluria’s technology platform.

Siluria plans to deploy its technology in a range of commercial settings, including existing ethylene producing plants, at ethylene consuming sites, upstream gas monetization, natural gas midstream plants, as well as world-scale deployments.

Ethylene—a valuable commodity two-carbon chemical that can be oligomerized into transportation fuels—is the most widely produced petrochemical feedstock globally. Siluria believes that its OCM process is the first commercially viable process for the direct conversion of methane to ethylene, potentially enabling natural gas to replace petroleum as the world-wide basis for drop-in fuels, chemicals and plastics.

… methane activation (the splitting of the C-H bonds) requires extreme conditions such as high temperatures (>900 °C), and/or the use of oxidation agents to complete conversion. Catalysts can also be used to reduce the extreme conditions required to activate the C-H bond provided they do so without forming a carbon oxygen bond. Incumbent methane conversion methods are based on an indirect approach using high temperature reforming to synthesis gas (a mixture of H₂ and CO). Partial oxidation, catalyzed partial oxidation, and steam methane reforming are all commonly practiced methods for producing hydrogen-rich syngas. Depending on the downstream processes to convert syngas into a product the ratios of H₂ to CO must generally be adjusted to meet the stoichiometric requirements of the downstream process. The hydrocarbon products that result may have broad product distribution and therefore require significant additional refining/separations and further cost and energy input.

—Weinberger et al.

The oxidative coupling of methane (OCM) converts methane into ethane and ethylene (C₂ hydrocarbons). In the OCM reaction, methane (CH4) is activated on the catalyst surface, forming methyl free radicals (CH₃) which then couple in the gas phase to form ethane (C₂H₆). The ethane subsequently undergoes dehydrogenation to form ethylene and water.

Motivated by the potential economic advantages of OCM, the OCM reaction has attracted significant attention since the fundamental work of Keller et al. in the early 1980’s. This was followed by significant industrial and academic research into the early 1990’s. Despite these efforts, no economically viable OCM process has been put into practice. The difficulties associated with the direct conversion of methane arise from both kinetics and thermodynamics. In particular, the complex nature of a homogeneous / heterogeneous reaction mechanism (involving both surface and gas phase reactions) imposes unique challenges to the catalyst requirements and function. For example, high temperatures are required for activation of methane, but at such conditions radical reactions in the gas phase are dominating favoring the formation of non-selective CO and CO₂ byproducts and also potentially causing severe catalyst deactivation from decomposition or sintering. Additionally, the reaction is highly dependent on the local chemical and electronic environment of the surface oxygen sites of the catalyst, which places additional design constraints for an effective catalyst.

—Weinberger et al.

Siluria’s catalyst synthesis process uses proteins on the surface of a genetically modified bacteriophage as nucleation sites for growing nanoscale wires of catalyst material. By growing the catalyst nanowires on an engineered biological template, Siluria is able to access crystal structures and surface morphologies not formed through conventional crystallization of the material. The novel crystal structures, in turn, give rise to catalyst active sites with unique properties that are critical to achieve the selectivity and yield required for an economically viable OCM process.

Resources

• Sam Weinberger, Erik Scher, and Rahul Iyer (2012) “Natural Gas to Ethylene in One Step Siluria Technologies OCM (Oxidative Coupling of Methane)” (AIChE 2012 Paper Nº 51A)