Decarbonisation Technology November 2026 issue

Notes: Unreacted methane can be separated from the hydrogen using PSA and recycled to the reactor. The size of the carbon granules is influenced by operating conditions and the residence time of the carbon in the reactor. Heat may be from

Methane

Hydrogen & graphite granules

Hydrogen

Hydrogen & carbon granules

renewable electricity. Methane can be from natural gas or biogas .

Methane

Carbon granules

Hydrogen, carbon granules

Methane

Plasma pyrolysis

Fluidised bed

Moving carbon bed

Molten metal or molten salt

Monolith materials ~95%

TNO or C-Zero

BASF ~92%

Hazer ~92%

Process shown Hydrogen content at reactor outlet

Up to 95%

Carbon black as powder or granules

80 to 95% graphite encapsulating catalyst dust particles

Carbon production

Molten 27% Nickel-73% Bismuth, Molten manganese chloride Indirect heat applied around the reactor or electrodes to heat the melt in a separate vessel Depends on melt, 650 to 1 , 100˚C

Carbon bed

Iron oxide granules

Catalyst required

Direct heating with plasma

Electrodes to heat the carbon bed and indirect heat applied around the reactor

Indirect heat applied around the reactor

Heating mechanism

Reactor temperature

2 , 000˚C

900˚C

1 , 000 to 1 , 400˚C

Reactor pressure

Close to atmospheric pressure

Up to 5 bar

Figure 3 Methane pyrolysis (cracking/splitting) for turquoise hydrogen production

renewable electricity, this is green syngas, ensuring CO 2 circularity. The configuration and mechanical design of the electrolyser stack Twelve has developed looks like a proton exchange membrane (PEM) water electrolyser stack. It can therefore be manufactured at plants that have been set up for PEM electrolyser production to achieve manufacturing synergies and scalability. Twelve has begun to commercialise high-value plastics for branded consumer products derived from circular CO2. At this point on the road to net- zero, where small-scale electrolyser operations are easier to implement than GW-scale projects, focusing on high-value, low-volume plastics must be the right strategy. When renewable power generation has significantly ramped up, there will be sufficient green electrons to produce clean energy vectors. However, until then, Twelve’s focus on polymers and plastics is the better strategy. Solid oxide electrolysis for e-syngas Solid oxide electrolysis is an electrochemical process for the conversion of CO2 to CO. In contrast to the Twelve process, which is a ‘low temperature electrolysis’ process and operates at

less than 100°C, solid oxide is referred to as ‘high temperature electrolysis’ and operates between 600 and 800°C. The higher end of this temperature range is ideal to promote the RWGS reaction, which combines hydrogen and CO2 to yield CO. This reaction is exploited by Sunfire in its co- electrolysis technology. In this case, steam and CO 2 are simultaneously fed to a solid oxide electrolyser stack. The steam is converted to hydrogen, which then reacts with the CO2 to form CO. When an excess of steam is fed to the electrolyser, some of the hydrogen remains, creating e-syngas as the product. Solid oxide electrolysis is also used by Topsoe for electrolytic CO 2 reduction to CO. In its configuration, the solid oxide electrolyser is fed only with CO2 and yields CO through electrochemical reduction. To generate syngas, another solid oxide electrolyser, or any other type of electrolyser, can be fed with steam or water to generate hydrogen. The separate hydrogen and CO streams are then blended at the appropriate ratio to generate e-syngas. Increasing the syngas yield from natural gas Partial oxidation (POx) of natural gas is an alternative to steam methane reforming,