Downstream Processing using Rotating Bed Reactors and Metal Scavengers

Transition-metal catalysis is commonly used in pharmaceutical industry. There is a risk that a small amount of the metal catalyst is leaching into the solution during the reaction.

A good method to remove the often toxic heavy metal ions from the reaction product is a metal scavenging resin. The selection of heterogeneous scavengers is good, ranging from neutral to ion exchange resins, organic to inorganic backbone, and more general to more specific.

Perhaps less common in use, there are scavengers for selected organic compounds based on complementary electrophilic-nucleophilic reactivity, e.g. aldehyde-amine and Michael acceptor-thiol.

Adjusting pH during workup is a very common procedure and ion exchange beads are an option for doing this, also offering a way to produce less salt in the vessels during workup.

We would like to include treatment of waste streams in the context of downstream processing. It may make environmental and/or economical sense to treat your own waste streams locally before discharge or destruction. At the production site, the waste streams are contained, concentrated, and this is likely where the most knowledge about the content is found. Where large, costly, or specialised treatment equipment is needed, it may make more sense transport to a common waste treatment site. Whether the waste stream contains excess dye from clothing/textile manufacture or active pharmaceutical ingredient (API) precursors from pharmaceuticals production, a simple activated carbon treatment may be sufficient to make the waste stream acceptable for discharge.

Best case scenario environmentally and financially, successfully treating the waste stream whether it is water or organic solvent, will allow it to be re-used in the process.

Ideally, the waste streams can be turned into a resource by extracting residual amounts of valuable components.

Two examples comes from the pharmaceutical industry;

  1. Scavenging and re-use of transition metals (e.g. palladium, ruthenium or iridium) from reaction waste after chemical transition metal-catalysis

  2. Recovery of API:s and precursors to API:s in small, residual concentrations from reaction waste or purification step waste.

In both examples, the transition metal and API precursor is likely to be toxic in the wrong place (e.g. aquatic life) but valuable when recovered in pure form.

Metal scavengers are typically added into the bulk liquid and then filtered off in the next step. Some use columns packed with the metal scavenger or adsorbent/absorbent of choice. Both these operations might be tedious and associated with work health issue handling these chemicals. 

Another option would be to use a rotating bed reactor (RBR) filled with the solid phase of choice and operated in the existing vessel or in an external waste storage vessel. 

LP downstream processingBefore and after the downstream processing of a palladium containing API using metal scavenger in a RBR.

 

Have a look at the SpinChem RBR Starter kits to learn more about the lab scale units available or for larger scale operations the ProRBR series might be the solution for you. 

Above mentioned metal scavengers, either silica based or polymeric resins could be purchased from these suppliers;

  1. Biotage supplies both silica and polymeric resins with a great variety of functionalities.

  2. Johnson Matthey supplies irregular and spherical silica and also polymeric backbones.

  3. Phosphonics supplies silica based metal scavengers.

  4. Silicycle also focuses on silica based scavengers.

  5. Purolite supplies all sorts of polymeric resins for metal scavenging.

 

 

If you have problems with contamination or pollution related impurities please contact us for a meeting. We can offer complete solutions, from lab scale to process scale. Read more about our services here or contact us below. 

 

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