Co-Mo Hydrogenation Catalyst

What Is a Co-Mo Hydrogenation Catalyst?

Key Takeaways:

• Dual-Active Efficiency: Utilizes a synergistic CoO/MoO₃ system on a γ-Al₂O₃ support for superior hydrodesulfurization (HDS) activity.
• Low Light-Off Temperature: Highly active from 200°C, reducing energy consumption and thermal stress during deep desulfurization.
• Versatile Feed Compatibility: Highly effective on lighter fractions (naphtha, kerosene, diesel) and gas streams (natural gas, syngas).
• Refractory Sulfur Removal: Effectively converts difficult sulfur species to meet stringent ULSD (IMO 2020/Euro VI) standards.

A cobalt-molybdenum (Co-Mo) hydrogenation catalyst is one of the most widely used catalyst systems in petroleum refining and gas processing. It consists of cobalt oxide (CoO) and molybdenum trioxide (MoO₃) impregnated on a high-surface-area γ-alumina (γ-Al₂O₃) support. Upon presulfiding, the active metals are converted to their sulfide forms — molybdenum disulfide (MoS₂) promoted by cobalt sulfide (Co₉S₈) — forming the catalytically active Co-Mo-S phase that drives hydrodesulfurization (HDS) and hydrodenitrogenation (HDN) reactions.

Co-Mo catalysts are particularly effective for removing sulfur from lighter petroleum fractions (naphtha, kerosene, diesel) and gaseous feeds (natural gas, refinery gas, synthesis gas). They operate at relatively low temperatures (starting from 200°C) compared to Ni-Mo systems, making them energy-efficient for applications where deep desulfurization of lighter feeds is required.

The catalyst is available in multiple extrudate geometries — cylindrical, trilobe, and quadrilobe — each offering different mass transfer characteristics and pressure drop profiles. The choice of shape depends on the specific reactor design, feed composition, and desired space velocity.

For a deeper look at how the Co-Mo-S active phase forms and why it's chosen over Ni-Mo systems, see our guide: What is a Co-Mo Hydrogenation Catalyst? Active Phase & Applications Explained.

Active Phase Chemistry

The catalytic activity of Co-Mo catalysts is directly linked to the formation of the Co-Mo-S active phase during presulfiding:

Oxide form (as shipped):

• Active metals: CoO (2-5 wt.%) + MoO₃ (12-16 wt.%)
• Support: γ-Al₂O₃ (balance)
• The oxide form is stable for storage and transport

Sulfide form (after presulfiding):

• Active phase: MoS₂ crystallites promoted by Co₉S₈ at the edges
• The Co-Mo-S structure creates highly active sites for C-S bond cleavage
• Cobalt acts as a promoter, increasing the number of active edge sites on MoS₂ slabs compared to unpromoted MoS₂

Why Co-Mo (vs. Ni-Mo or Ni-W)?

• Co-Mo offers the best balance of HDS activity and selectivity for lighter feeds (naphtha, diesel, gas)
• Lower hydrogen consumption compared to Ni-Mo for equivalent sulfur removal
• Better olefin saturation selectivity — removes sulfur without excessive hydrogenation of valuable olefins
• More economical for applications that don't require the higher hydrogenation activity of Ni-based systems

Key Reactions

The Co-Mo hydrogenation catalyst drives multiple simultaneous reactions in a single catalytic bed:

• Thiol hydrogenolysis: RSH + H₂ → RH + H₂S
• Sulfide hydrogenolysis: R₁SR₂ + 2H₂ → R₁H + R₂H + H₂S
• Disulfide hydrogenolysis: R₁SSR₂ + 3H₂ → R₁H + R₂H + H₂S
• Thiophene hydrogenolysis: C₄H₄S + 4H₂ → C₄H₁₀ + H₂S
• Benzothiophene HDS: C₈H₆S + 3H₂ → C₈H₁₀ + H₂S
• Dibenzothiophene HDS: C₁₂H₈S + 3H₂ → C₁₂H₁₂ + H₂S
• COS hydrogenolysis: COS + H₂ → CO + H₂S
• CS₂ hydrogenolysis: CS₂ + 4H₂ → CH₄ + 2H₂S
• Olefin hydrogenation: CₙH₂ₙ + H₂ → CₙH₂ₙ₊₂
• Hydrodenitrogenation (HDN): R-NH₂ + H₂ → RH + NH₃

How It Works

The hydrodesulfurization process using Co-Mo catalyst operates as follows:

1. Presulfiding Stage: The catalyst is shipped in oxide form and must be converted to the active sulfide phase before introducing feed. This is typically done by adding a sulfiding agent (DMDS or CS₂) to a hydrogen stream at controlled temperature ramp rates (200-350°C). Complete sulfidation is critical — incomplete presulfiding leads to permanently reduced activity.
2. Hydrotreating Stage: Sulfur-containing feedstock is mixed with hydrogen and passed over the catalyst bed at 200-450°C and 1.5-5.0 MPa. Organic sulfur compounds undergo catalytic hydrogenolysis, breaking C-S bonds and releasing H₂S. Simultaneously, nitrogen compounds are converted to NH₃ (HDN), and olefins are saturated to paraffins.
3. H₂S Removal Stage: The generated H₂S is separated from the product stream, typically by amine scrubbing (MDEA, DEA) for liquid feeds or by a ZnO guard bed for gaseous feeds. The desulfurized product meets specification (e.g., < 10 ppm S for ULSD, < 0.1 ppm S for synthesis gas).

Presulfiding Requirement

Complete and controlled presulfiding is essential for achieving full catalytic activity:

Common presulfiding methods:

• Gas-phase presulfiding: DMDS or CS₂ is injected into a hydrogen/nitrogen stream. Temperature is ramped from ambient to 300-350°C over 8-24 hours. H₂S breakthrough is monitored to confirm sulfidation progress.
• Liquid-phase presulfiding: DMDS is added directly to the light hydrocarbon feed (e.g., naphtha) during reactor warm-up. This method is common in refinery hydrotreaters.
• Ex-situ presulfiding: Some suppliers offer pre-sulfided catalysts that eliminate the need for on-site presulfiding, reducing startup time and complexity.

Key presulfiding parameters:

• Temperature ramp rate: Controlled to prevent thermal shock and ensure uniform sulfidation throughout the catalyst bed
• H₂S concentration: Must be maintained above a minimum threshold in recycle gas throughout the sulfiding period
• Sulfur uptake: Typically 8-15% of catalyst weight at end of presulfiding, depending on CoO and MoO₃ loading
• Endpoint confirmation: Sulfidation is complete when H₂S concentration in the effluent stabilizes and no further sulfur uptake is observed

Operating Conditions

Typical operating conditions vary by application:

• Naphtha HDS: 280-380°C, 2.0-4.0 MPa, LHSV 2.0-6.0 h⁻¹, H₂/HC 150-300
• Diesel HDS (ULSD): 320-400°C, 3.0-5.0 MPa, LHSV 1.5-3.0 h⁻¹, H₂/HC 300-500
• Kerosene HDS: 300-360°C, 2.0-4.0 MPa, LHSV 2.0-5.0 h⁻¹, H₂/HC 150-300
• Gas-phase HDS: 250-380°C, 1.5-4.0 MPa, GHSV 1,000-3,000 h⁻¹, H₂/HC 50-100
• Synthesis gas cleaning: 250-350°C, 2.0-5.0 MPa, GHSV 1,000-2,500 h⁻¹, H₂/HC 50-80

These are typical industry reference ranges for this catalyst class. Actual operating conditions depend on your specific feed composition and reactor design — please contact us with your process data for a tailored recommendation.

Deactivation Mechanisms & Prevention

Co-Mo catalysts can lose activity over time through several mechanisms:

• Coke Deposition: Carbonaceous deposits block active sites and pores, especially at higher temperatures or with feeds containing high concentrations of olefins or aromatics. This is partially reversible through regeneration.
• Metal Poisoning: Trace metals (arsenic, lead, silicon) in the feed can irreversibly poison active sites. For feeds with high metal content, a guard bed or pretreatment step is recommended.
• Sulfation / Over-oxidation: Exposure to oxygen or water at high temperatures can convert active sulfide phases back to less active oxide or sulfate forms. Strict control of feed quality and reactor atmosphere is essential.
• Thermal Sintering: Prolonged operation above the maximum design temperature causes sintering of MoS₂ crystallites and loss of active surface area. Temperature monitoring and control systems are critical.
• Mechanical Damage: Thermal cycling, pressure surges, or improper catalyst loading can cause particle breakage, increasing pressure drop and creating channeling. Proper loading procedures and stable operation minimize mechanical damage.

Best practices for maximizing catalyst life:

• Maintain feed quality within design specifications (sulfur, nitrogen, metals, water content)
• Avoid temperature excursions above the maximum rated temperature
• Ensure complete presulfiding before introducing feed
• Monitor pressure drop across the bed — sudden increases indicate fouling or particle breakage
• Use a guard bed or particulate filter upstream if feed contains suspended solids
• Plan regeneration cycles based on activity monitoring, not fixed time intervals

Regeneration & Service Life

When activity declines due to coke deposition, the catalyst can be regenerated through controlled oxidative burn-off:

Regeneration process:

1. Stop feed and purge the reactor with inert gas (N₂)
2. Introduce controlled amounts of air into the inert gas stream at low oxygen concentration (initially < 1% O₂)
3. Gradually increase oxygen concentration while closely monitoring bed temperature to prevent runaway exotherm
4. Complete regeneration when CO₂ evolution ceases, indicating all coke has been burned off
5. Resulfidation is required before reintroducing feed

Service life expectations:

• Typical on-stream life: 3-5 years per cycle (depending on feed severity and operating conditions)
• Regeneration cycles: 1-3 regenerations possible, depending on the extent of irreversible deactivation
• Total useful life: 6-15 years with proper management
• Off-site regeneration by specialized service companies can achieve higher activity recovery through precise temperature control and advanced techniques

Packaging & Shipping

We offer flexible packaging and shipping options to suit your project scale and logistics requirements.

Standard Packaging:

• 25 kg drums (moisture-proof, suitable for trial orders and small batches)
• 150 kg steel drums (standard bulk packaging for industrial orders)
• 500 kg super sacks (most popular for industrial bulk orders)
• 1000 kg jumbo bags (for large-scale projects)
• Custom packaging available on request

Minimum Order Quantity (MOQ):

• 1 ton (entry-level orders accepted — perfect for first-time customers)
• 5+ tons (standard bulk orders)
• Container-level supply for long-term partnerships

Container Loading Capacity:

• 20'GP container: 18-20 tons (palletized)
• 40'GP container: 22-24 tons (palletized)
• 40'HQ container: 24-26 tons

Loading Ports: We ship from major Chinese ports based on your requirements: Shanghai, Qingdao, Tianjin, Ningbo, and Shenzhen.

Lead Time:

• Stock orders: 7-15 days from payment confirmation
• Made-to-order: 20-30 days

Shipping Terms: FOB / CIF / CFR / EXW — flexible based on your destination and preferences.

Storage & Handling: Store in cool, dry conditions. Protect from moisture, chemical contamination, and physical impact. Avoid exposure to oxidizing atmospheres. Shelf life exceeds 5 years when stored properly in original packaging. Use appropriate personal protective equipment (PPE) when handling — catalyst dust may cause respiratory irritation.

Documents & Certificates

We provide complete documentation for every order:

📄 Technical Data Sheet (TDS) — Confirmed with you during product selection, ensuring exact specifications match your application requirements.

📄 Safety Data Sheet (SDS) — Provided before shipment, meeting all international transportation and handling standards.

📄 Certificate of Analysis (COA) — Issued for each production batch, delivered with your shipment for full quality traceability.

Additional documents available on request: Certificate of Origin (COO), Packing List, Commercial Invoice, Third-party Inspection Report (SGS / BV), Form E (for Middle East destinations with applicable tariff benefits).

FAQ

Q1: What's the difference between Co-Mo and Ni-Mo hydrogenation catalysts? Co-Mo catalysts are optimized for HDS of lighter feeds (naphtha, diesel, gas) with lower hydrogen consumption and better olefin selectivity. Ni-Mo systems are generally preferred when higher hydrogenation activity or hydrodenitrogenation performance is needed for heavier feeds.

Q2: Does the catalyst need presulfiding before use? Yes. The catalyst ships in oxide form and must be converted to the active Co-Mo-S sulfide phase through presulfiding (gas-phase, liquid-phase, or ex-situ) before introducing feed. Incomplete presulfiding permanently reduces activity.

Q3: How long does the catalyst last in service? Typical on-stream life is 3-5 years per cycle, with 1-3 regeneration cycles possible depending on feed severity and deactivation extent — giving a total useful life of 6-15 years with proper management.

Q4: What's the minimum order quantity? MOQ starts from 1 ton for trial orders, with 5+ tons as our standard bulk order and container-level supply available for long-term partnerships.

Need a Custom Solution?

For bulk pricing and grade recommendation, please send your feedstock composition & reactor conditions to us. Our technical team will get back to you within 24 hours with a tailored solution.

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