Filing activity in this space is concentrated: the top 5 of 38 ranked assignees together hold 146 of 187 records in scope, or 78.1%. The single leading assignee alone holds 48 records, well ahead of the fifth-ranked filer at 12. This means a small group of refining technology licensors and majors controls most of the documented claim space, and any competitive or freedom-to-operate analysis should start there before widening to the full ranked list.

Afterburn refers to uncontrolled combustion of carbon monoxide occurring after the main catalyst regeneration reaction, typically in the dilute phase above the catalyst bed or in the cyclones and flue gas lines. It is a specific engineering problem covered directly in the dataset's search terms, and representative filings such as US6776607B2 address it through steam injection into the dilute phase to promote controlled CO combustion before gas reaches the cyclone train. Because this is a well-established failure mode, expect dense prior art around gas-injection and combustion-control approaches specifically.

The trend points to a slowdown rather than continued growth: filings rose from 2 in 2017 to a peak of 10 in 2018, then eased to 3 by the 2022 midpoint, and every leading assignee tracked shows 0 filings in the most recent year. That said, publication typically lags filing by around 18 months, so the last one to two years in this dataset understate true filing activity and should not be read as a hard stop. A re-check in twelve months would give a clearer picture of whether the slowdown is real or a lag artefact.

The most-cited records in this dataset, drawing 163 and 121 citations respectively, both concern FCC feed contacting with a catalyst recycle reactor and have shaped the mechanical geometry that later filings build on. High citation counts inside a searched corpus favour older filings, so these numbers reflect long-standing influence rather than current enforceability, but the underlying contacting and recycle-reactor concepts remain reference points that new filings are typically drafted to distinguish from rather than repeat.

The smaller IPC clusters in this dataset — F28D heat-exchange apparatus at 4.8% of 187 records, B04C cyclone separators at 2.1%, and B03C magnetic or electrostatic separation at 1.1% — carry far fewer filings than the core C10G and B01J classes. This can indicate genuine under-claimed sub-areas such as regenerator heat-balance instrumentation or fines separation by non-mechanical means, though it may also simply reflect the narrowness of this specific search string. Either way, these branches warrant a dedicated search before assuming they are open.