Gemini - Oxidative coupling of methane (OCM) Linde Engineering together with Siluria Technologies delivers disruptive solutions for single-step production of ethylene from methane.

For the downstream petrochemical industry, ethylene is one of the most important building blocks, with annual consumption of around 160 million metric tonnes and this is growing at a rate of 3 to 4% p.a. For example, polymers (plastics) such as polyethylene (PE) are produced by polymerisation of ethylene.

The predominant process route for ethylene production is steam cracking of C2+ hydrocarbons. However, methane (C1) as a cheap, alternative feedstock from abundant conventional (e.g. natural gas) or growing unconventional (e.g. shale gas) resources cannot be converted by steam cracking.

The production of ethylene from methane using a multi-step process combining synthesis gas generation, methanol production and MTO (= Methanol-To-Olefins, i.e. ethylene and propylene) entails significant challenges due to the tremendous capital investment requirements and resulting in unfavourable project economics.

Over the last decades, significant efforts were made in research and industry globally to enable a direct, catalytic conversion of methane to ethylene in the presence of oxygen, known as Oxidative Coupling of Methane (OCM).

Developed catalysts did not meet the minimum requirements for commercial-scale applications.

Keen to resolve this challenge, Siluria Technologies, a US startup company based in San Francisco, developed a unique, economically viable OCM catalyst and related reaction technology that overcomes the limitations of formerly failed developments.

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Gemini is the first commercial process to directly convert natural gas into ethylene, a key building block for the global petrochemicals industry.

In 2014, Linde Engineering and Siluria teamed up to commercialise OCM.

Building on Linde’s excellent, long-standing technological expertise and superior track record in designing and building ethylene plants, Linde integrated Siluria’s OCM technology into competitive, commercial-scale applications including also Linde’s proprietary ethylene separation and purification processes.

Since 2014, Siluria has been operating an OCM demonstration plant with a capacity of approx. 400 tonnes of ethylene per year at Braskem’s facilities in La Porte (US).

The plant has successfully proven safe and sustainable process performance since its initial start-up in late 2014.

Highest value creation: Oxidative Coupling of Methane (OCM) pilot plant in La Porte, USA.

In the first reactor section, the two main reactants, methane and oxygen, are uniformly distributed through a proprietary mixer to an adiabatic fixed-bed with Siluria's OCM catalyst, where mainly ethylene is formed.

The heat of the highly exothermic OCM reactions is then utilised in the second reactor section for thermal cracking of ethane to ethylene (PBC = Post Bed Cracking).

Ethane is formed as a by-product in the first reactor section and needs to be recycled from the separation part of the plant. Fresh ethane (and/or propane^*) can be additionally introduced into the process as co-feedstock for conversion in the PBC section.

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^* Post bed cracking of propane co-feedstock to be finally confirmed in demo plant.

• Licensing  
• Engineering and supply of proprietary equipment  
• EPC services  
• Fully fledged EPC turnkey as needed
  

The OCM product portfolio covers: 

• Stand-alone plants
• Add-on applications for steam cracker/olefin plants
  
  • New/grassroots plants
    
  • Revamp solutions
    
• Small scale (< 100 kta ethylene) to world scale (> 600 kta ethylene)