Catalyst Recovery

Active Pharmaceutical Ingredient (API) processes use a variety of precious metal catalysts for facilitating the hydrogenation of intermediates. Typically, palladium and platinum catalysts are employed; however, other platinum group metals such as rhodium and ruthenium can also be used. For an API process to be economically feasible and environmentally compliant, these catalysts require efficient removal and recovery. Activated carbon supports are the most commonly used products for catalyst recovery. However, these supports are non-selective and can lead to API yield losses.

Dow has developed a number of different resin chemistries that selectively bind divalent metals, including platinum group metals. These resins are listed below in Table 1, and the structure of the iminodiacetic acid resin is shown in Figure 1 with the reaction mechanism for the aminophosphonic acid resin shown in Figure 2.

Table 1 – Dow Catalyst Recovery Resins

Figure 1 – Structure of Iminodiacetic Acid Resin

Figure 2 - Characteristic Reaction for Aminophosphonic Acid Resin

R-CH2-NH-CH2-PO3Na2 + Mg2+

R-CH2-NH-CH2-PO3Mg + 2 Na+

Our thiouronium resin is particularly selective for platinum group metals. However, it is unstable at high pH and is therefore recommended for only acidic and neutral pH conditions. A full description of recommended conditions for Dow catalyst recovery resins is shown in Table 2.

Table 2 – Recommend pH Conditions for Dow Catalyst Recovery Resins

Limits of Use

For specific pharmaceutical applications, it is recommended that all potential users contact their Dow representative in order to determine the best resin choice and optimum operating conditions.