Improving Operator Safety in API Catalyst Recovery

The Separation Technology

The method by which the catalyst is removed from the pharmaceutical intermediate is dependant on the form of catalyst. They are typically divided into either heterogeneous or homogeneous form. In this case study we are dealing with heterogeneous catalysts that can be removed by physical filtration.  

Heterogeneous catalysts are solid catalysts used in reactions where the reactants are in a different phase, typically liquid. These are favoured due to the relative ease of separation from the reaction mixtures.

• Palladium on Carbon (Pd/C) : Widely used for hydrogenation reactions
• Platinum on Carbon (Pt/C) : Employed in hydrogenation and oxidation processes
• Rhodium on Alumina (Rh/Al₂O₃) : Used in hydroformylation reactions
• Ruthenium on Carbon (Ru/C) : Applied in various hydrogenation reactions

The Problem

Once used in the synthesis, the catalyst needs to be removed for subsequent disposal or recycling in a safe and efficient way. Spent palladium catalyst can pose a number of health and safety risks such as 

• Toxicity of palladium compounds 
  • palladium salts and complexes can be toxic if inhaled or ingested
• Exposure to organic solvents
  • Palladium catalysts are often used in solvent based reactions e.g. toluene / THF / dichloromethane. 
• Dust and Particulate inhalation
  • Spent catalyst can be in the form of fine dust 
• Fire and Explosion risk
  • Pd/C is pyrophoric ( can self combust with exposure to air) Catalyst should be kept damp with with water purge or in residual solvent
  • residual solvents and reactants may present additional flammability risk
• Reactivity Hazards 
  • Improper neutralisation or containment could result in thermal runaways 
• Waste Handling and Contamination
  • Handling of spent catalyst must adhere to hazardous waste protocols
  • Potential for operator exposure

Traditional methods for recovering or capturing spent catalysts include, but are not limited to, manual plate filters, filter presses, bags or lenticular cell filters.

The main problem with these technologies is potential operator exposure once the catalyst has been captured. So how do you capture the catalyst and remove it from the process while minimising or eliminating operator exposure?

Customer Application Details

This particular process used a Palladium on Carbon (Pd/C) catalyst (5 % wt. loading on an activated carbon matrix). This is supplied wet (50% water), then mixed with Methanol for use in the reaction vessel. 

The customer traditionally used filter bags to capture the catalyst, but this method had inherent associated health and safety issues. Filter change outs increased the risk of operator exposure and made subsequent re-packaging for off-site processing complicated. 

The SupaClean Advantage

The SupaClean system provides an elegant solution to improve the health and safety of catalyst removal.

1. Following filtration of the catalyst slurry low pressure compressed nitrogen can be introduced via the integral tapping on the side of the SupaClean housing. This collapses the internal flexible containment bag and purges out residual carrier solvent.
2. The SupaClean filter inlet and outlet connections are then capped off securely ensuring the catalyst remains 'wet' in the filter to prevent any risk of combustion as the catalyst is pyrophoric.
3. The SupaClean housing can be supplied in a customised 'cradle' that allows the housing to pivot to further improve health and safety with respect to manual handling.
4. The SupaClean filter system can accommodate any of the Amazon Filters range of cartridges. This ensures the required filtration efficiencies can be matched to the size of the catalyst particle size.
5. The flexible bag used in the SupaClean filter is available in various materials to ensure chemical compatibility.
6. Feedback from companies recovering the palladium or other rare metal from the catalyst say that the SupaClean format also substantially simplifies health and safety implications at their own facilties.
   

For more detailed information on the product click here SupaClean.