The core of Siluria’s technology is its novel bio-templated catalyst that enables the OCM reaction to convert methane into ethylene, the most common and versatile chemical intermediate. Siluria then combines these ethylene molecules to produce long-chain hydrocarbons that form drop-in liquid fuels such as gasoline, diesel, or jet fuel. In March, Siluria unveiled a development unit for producing such liquid fuels from natural gas based on its OCM and ethylene-to-liquid (ETL) technologies. (Earlier post.)

The OCM reaction—which converts C1s (i.e., CH₃, methane) into C2s (i.e., ethylene (C₂H₄)—has been known for years, but has yet to be successfully commercialized due to the challenging chemistry. The basic OCM reaction (which is exothermic) is:

2CH₄ + O₂ → C₂H₄ + 2H₂O

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.

However, methane is extremely stable and symmetric, with strong C-H bonds and no functional group, magnetic moment, or polar distribution to facilitate chemical activation. In a paper presented at AIChE’s 2012 Spring National Meeting, Siluria scientists explained that:

… 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 Technologies has combined 3 major recent scientific advances that were unavailable to earlier researchers in this chemistry:

1. Biomaterial Templating - the use of genetically engineered biomaterials to influence the structure of inorganic catalysts grown on these templates;

2. Nanowire Catalyst Design - a synthetic method that permits the influencing of catalyst properties by changing the active sites, and which can be made under commercially scalable synthetic conditions; and

3. High-throughput Screening – that allows for measuring gas-to-gas reactions orders of magnitude faster than in traditional reactors.

There are a number of potential benefits to the use of an economically viable OCM process for the conversion of methane to fuels, Siluria notes:

• Reduced reliance on petroleum
• The potential for lower fuel prices to consumers
• An efficiency that could enable viable small-scale plants in diverse locations
• Lower emissions than traditional processes

Siluria has created a growing portfolio of process configurations with applications in upstream, midstream gas processing, downstream chemicals production and refining operations.

Recently, Siluria announced a partnership with The Linde Group, a world leading gases and engineering company, to offer an integrated package combining Siluria’s technology with Linde’s separations and recovery systems for licensing to the petrochemical industry at existing ethylene plants or for new world scale ethylene plants. (Earlier post.)