FCC Catalyst Additives
FCC catalyst additives are functional particles added to the circulating catalyst inventory in small proportions (1-10 wt%) to achieve a specific objective that the base catalyst alone does not provide. The most widely used additive is ZSM-5 for propylene and octane enhancement; others address metals tolerance, SOx emissions, CO combustion, and bottoms cracking.
ZSM-5: The Propylene and Octane Additive
ZSM-5 is the most effective FCC additive for simultaneously increasing propylene yield and gasoline octane without raising reactor severity. Unlike USY and Y zeolites that form the base cracking catalyst, ZSM-5 is used as a separate additive particle at 2-10 wt% of the total FCC catalyst inventory.
How it works: ZSM-5’s 10-MR channels (5.1-5.6 Å) selectively admit low-octane linear and mono-methyl-branched C₇-C₁₂ olefins in the gasoline boiling range while excluding higher-octane branched, cyclic, and aromatic molecules. Inside the channels these gasoline-range olefins are cracked to lighter C₃-C₅ olefins — primarily propylene.
Quantitative impact:
- Propylene yield increase: 2-6 percentage points
- Gasoline research octane increase: 1-3 numbers
- Negligible effect on conversion or coke yield at typical loadings
Recommended grade: ZSM-5 with SiO₂/Al₂O₃ of 20-50 (higher acidity) for maximum propylene response; phosphorus-stabilised ZSM-5 for severe hydrothermal conditions. See ZSM-5 for FCC Additives for full operating data.
Other FCC Additive Types
| Additive Type | Function | Typical Loading |
|---|---|---|
| Metal traps (MgO, rare-earth compounds) | Passivate Ni/V from heavy feed, protect zeolite framework from vanadic acid attack | 1-5 wt% |
| SOx reduction additives | Convert SO₂/SO₃ in regenerator flue gas to H₂S in reactor | 1-3 wt% |
| CO combustion promoters | Complete CO oxidation in regenerator, lower coke burn temperature | 0.1-1 wt% |
| Bottoms cracking additives | Target large-molecule cracking for resid feeds | 1-5 wt% |
ZSM-5 is less susceptible to metal poisoning than FAU zeolites because its smaller pores exclude bulky metal-porphyrin complexes — an additional reason it is frequently used in high-metals operations.
When requesting a sample of FCC additives, specify your base catalyst system, feed metals content, target propylene/octane increase, and regenerator conditions. See the FCC solution hub for zeolite selection guidance.
Request a Sample or Quote
Share your zeolite catalyst product, application, required specification, and quantity so the right TDS, COA, sample, or quotation can be matched to your evaluation.
Request a Sample or Quote