Ammonia cracking, also called ammonia decomposition, is the catalytic reaction that splits NH3 back into nitrogen and hydrogen gas. It matters because ammonia is far easier to ship and store as a liquid than hydrogen is, so a workable cracking step at the point of use turns ammonia into a practical hydrogen-carrier for shipping fuel, power generation and fuel-cell applications. The patent record in this space is concentrated on the catalyst and reactor design needed to make that release efficient at usable temperatures and pressures.

The filing base includes long-standing industrial catalyst and gas-process companies alongside newer dedicated ammonia-to-hydrogen carrier specialists and combustion-engine developers. Several of the historically largest filers show no activity in the most recent tracked year, while a Japanese engine-and-shipbuilding pairing shows the strongest sustained co-filing relationship in the dataset. Rather than a single dominant leader, the field currently looks like a set of parallel programmes with different technical entry points — catalysis, separation and engine integration.

Filing volume rose sharply from near zero in the mid-2010s to a peak of 70 families in 2024, but the two most recent years in the dataset show lower counts. Because patent publication typically lags filing by around 18 months, that apparent slowdown is at least partly an artefact of the data cut-off rather than a genuine drop in R&D activity. A fair read is that the field grew fast through 2024 and current momentum is still being resolved as more recent filings publish.

Relative to the catalytic cracking reaction itself, which is covered densely under IPC class B01J, the engine and turbine integration codes — covering internal combustion engines, gas turbines and fuel supply systems — carry noticeably fewer filings. Residual ammonia removal downstream of the cracking step, captured partly under separation class B01D, also shows comparatively lighter density than the core catalyst claims. These are reasonable areas to search more granularly before assuming the space is occupied.

US9341111B2, held by Hitachi Zosen, claims an ammonia-engine architecture that places an ammonia oxidizing device between the engine and the cracking device specifically to keep the cracking catalyst hot enough during low-load operation. Anyone designing a similar thermal-management scheme for an ammonia-fuelled engine — using oxidation heat to sustain cracking-catalyst temperature across load conditions — should review this claim scope closely. Alternative approaches, such as electrical pre-heating or exhaust-gas recirculation strategies that do not rely on an intermediate oxidizing device, sit outside its specific claim language.