Catalyst Considerations

Chapter from the Renewable Fuels Processing Guide.

CATALYST SELECTION FOR RENEWABLE FUELS

Catalyst Options

Catalyst Type	Chemistry	Application	Advantages	Limitations	Vendors	Notes
CoMo/Al2O3	Conventional HDS catalyst	Co-processing, standalone HDO	Widely available, well-understood	Less active for HDN, some DCO	Multiple (Criterion, Albemarle, Haldor Topsoe)	Most common for <20% blend
NiMo/Al2O3	HDN + HDO catalyst	Standalone renewable units, high N feed	Better deoxygenation, handles N	Higher H2 consumption than CoMo	Multiple	Preferred for dedicated units
Pd/C or Pt/C	Noble metal on carbon	Isomerization stage (2nd stage)	Excellent isomerization activity	Expensive, sensitive to S/N	Clariant, Johnson Matthey	Requires low S feed (<10 ppm)
NiW/SiO2-Al2O3	Bifunctional (metal + acid)	Combined HDO + isomerization	Single-stage to iso-paraffins	Complex, less proven at scale	Specialty vendors	Emerging technology
Ni/Al2O3 (reduced)	Supported nickel	DCO pathway preference	Lower H2 consumption	Lower activity, fouling risk	Various	Research/pilot stage for some
Guard bed (HDM)	Large-pore, metal-tolerant	Feed pretreatment, metals capture	Protects main catalyst	No HDO activity	Multiple	Essential for waste fats/oils

Catalyst Deactivation in Renewable Service

Renewable feedstocks present unique catalyst deactivation challenges:

1. Alkali Metal Poisoning:
• Na, K, Ca, Mg from feedstock → deposit on catalyst acid sites
• PERMANENT deactivation — cannot be regenerated
• Prevention: feedstock pretreatment to <1 ppm total metals

2. Phosphorus Deposition:
• Phospholipids in vegetable oils → P deposits on catalyst
• Blocks active sites, increases ΔP
• Prevention: thorough degumming, target <5 ppm P in feed

3. Coking:
• Polymerized triglycerides and free fatty acids → coke precursors
• Higher coking tendency than petroleum at same conditions
• Mitigation: adequate H2 partial pressure, avoid temperature excursions

4. Water Effects:
• Large water production can hydrothermally destabilize alumina support
• Long-term: sintering of active metals, loss of surface area
• Mitigation: operate within catalyst vendor's water tolerance limits

Source: Renewable_Fuels_Processing_Guide_v1.xlsx · sheet “Catalyst Considerations”

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