One assignee leads the ranked field with 37 records, well ahead of the rest of the 15 companies in the ranking, where fifth place holds only 3 records and tenth place holds 2. This gap indicates a portfolio built up over sustained large-scale plant engineering work rather than a recent surge of filings. The remaining ranked assignees are a mix of universities, national research bodies and smaller process-technology firms, each with single-digit record counts, so competitive pressure outside the leader is comparatively light.

Filing volume peaked at 10 records in 2022 and the tracked 2021-to-2024 window shows a decline from 8 to 4 records, a 50% drop over three years. However, publication typically lags filing by around 18 months, so the 2025 and 2026 figures in this dataset are still incomplete and should not be read as confirming a continued decline. The safest reading is that filing has pulled back from a 2022 peak, with the most recent trend still unresolved.

Liquid hydrogen naturally contains a mix of ortho and para spin isomers, and if the para fraction is not raised before storage the gas continues converting after liquefaction, releasing heat that causes boil-off losses. Patents in this space cover the catalysts and process stages used to drive that conversion during liquefaction rather than after it. In this dataset, catalyst and materials-related claims (IPC class C09K) appear in 31.0% of the 71 records, a much smaller share than the 91.5% covering the core liquefaction cycle itself, suggesting catalyst-specific claims are less crowded than cycle-configuration claims.