Advanced Hydrotreating & MaxFlux: Unlocking Clean Hydrocarbons from Pyrolysis Oil

Introduction

Pyrolysis oils distilled from mixed plastic waste offer a potential goldmine for circularity, but only if they are upgraded to meet the stringent purity demands of modern chemical plants and refineries. This essential upgrade step hydrotreating is delivered at its most effective by Sulzer’s advanced MaxFlux technology.

Why Hydrotreat Pyrolysis Oil?

• Unpurified pyrolysis oil contains high levels of sulfur, nitrogen, halogens (like chlorine), oxygenates, and metals.

• These impurities pose risks of catalyst poisoning, corrosion, and regulatory non-compliance in downstream processes.

• Only ultra-clean hydrocarbons (<1 ppmw of critical contaminants) are accepted in steam crackers, polymer units, or as chemical feedstock.

  
  

How MaxFlux Hydrotreating Outperforms

Key Process Features

• High Liquid Flux Design:Unlike trickle-bed reactors, MaxFlux® dissolves hydrogen directly in the liquid phase, eliminating the need for a large hydrogen gas recycle loop. This means:

  • Enhanced impurity removal

  • Lower energy use

  • Simplified unit design and integration

• Superior Mixing & Temperature Control:Hydrodynamic internals ensure efficient hydrogen/feed mixing, distributing flow across the catalyst bed and stabilizing temperatures. This:

  • Prevents hot spots (exotherms)

  • Minimizes over-cracking and unwanted side reactions

• Extended Catalyst Life:Maximized contact and lower coking rates mean fewer shutdowns, longer maintenance intervals, and reduced operational costs.

  
  

Step-by-Step MaxFlux Process

1. Feed Preparation:Pyrolysis oil is passed through adsorbent and guard beds to trap harmful trace elements and protect main catalysts.

2. Hydrotreating Reactor:Hydrogen is intimately mixed with the oil; contaminants (S, Cl, N, O, metals) are converted and removed across one or more catalyst beds. Temperature is regulated for stability.

3. Product Separation:Cleaned oil is separated from off-gases and byproducts in strippers or fractionators; streams like naphtha are drawn off, ready for chemical industry use.

4. Recycling as Needed:Effluent can be partially recycled for optimized yield and process efficiency.

   
   

Table: MaxFlux vs. Conventional Hydrotreating

Feature	MaxFlux	Conventional Trickle-Bed
Hydrogen utilization	Dissolved in liquid (no recycle loop)	Gas phase with recycle loop
Impurity removal	<1 ppmw S, N, Cl, O, metals	Typically higher
Energy & OPEX	Lower—no large recycle compressors	Higher—compressors required
Catalyst life	Longer, less coking & better thermal control	Shorter, more frequent coking
Integration	Modular, flexible for retrofits or new plants	Complex, less flexible

Why Sulzer for Your Pyrolysis Oil Upgrade?

• Lowest CAPEX and OPEX:

  Efficient operation, fewer moving parts, and minimal required utilities.

• Proven Technology:

  Operating at major plants integrating plastics recycling into mainstream refineries and chemical value chains.

• Modular Engineering:

  Fast installation, easy expansion, and adaptation to both greenfield and brownfield sites.

  
  

Conclusion

Sulzer’s MaxFlux hydrotreating is at the heart of converting contaminated pyrolysis oil into specification-grade hydrocarbons making the circular plastics economy not just possible, but practical and profitable. By efficiently removing all key contaminants and protecting catalyst life, Sulzer empowers recyclers and producers to meet both economic and environmental targets.