SUSTAINABILITY
Figure 2 - Packed bed column reactor set-up
the void volume of the column was measured to be 120 ml .
A flow rate of 6 ml / min was used to trial the process , giving the solvent a residence time of 20 minutes inside the packed column . The process was then carried out continuously over 200 hours on a sample containing 0.85 % ECH and 4.8 % IPA .
Over this period , approximately 70 L of waste THF solution was processed , and no pressure drop across the column was observed . In that time , the temperature of the packed bed column was varied between 60 ° C and 90 ° C to determine the optimal minimum temperature for the process . It was found that running the process at 70 ° C removed all ECH from the waste stream . Running it at 60 ° C and 65 ° C gave results within specification for incineration , with only trace amounts remaining .
The catalyst showed no sign of deactivation or poisoning after 200 hours of continuous use , so more work was carried out to determine catalyst lifetime . The process was then restarted and run for another 530 hours . The catalyst showed no significant decrease in activity after
730 hours of operation , and in that total time , 250 litres of solvent was treated , with the addition of 12.5 L of IPA , giving an efficiency of 1.42 L of waste treated / gram of catalyst .
Future plans
The flow method has multiple potential benefits to Sterling , both from a sustainability standpoint and economically . The method results in THF that does not contain water , which allows full recovery and could provide virgin-specification solvent . Subject to confirmation , this solvent could then potentially be recycled and reused in the manufacturing process .
The current target for the pilot is to process 7,000 L in 72 hours , which would use 53 kg of catalyst packed in an 80L column . However , based on these trials , it would suggest that this process is a viable alternative to previous batch treatments , and a longer continuous process run is planned imminently to confirm this , as well as the potential lifetime of the catalyst , and also whether the catalyst can be regenerated if necessary .
The method will be scaled up in the main plant to investigate the longer- term consistency of the catalyst , and the efficiency of processing greater volumes of solvent in a larger column . Any cost savings will come from the balance of the expense of the catalyst and flow process against the potential recyclability or reusability of the solvent , removing waste contractor costs and freeing up of batch vessels to generate alternative revenue streams .
To date , the experience has demonstrated the value of looking at the application of technology to improve efficiency and increase sustainability of Sterling ’ s manufacturing processes . The company has identified a number of other potential waste streams that could be evaluated in a similar manner . ●
* - Nafion is a trademark of Sigma-Aldrich
Mark Muldowney
HEAD OF TECHNOLOGY & INNOVATION
STERLING PHARMA SOLUTIONS k + 44 191 250 0471 J enquires @ sterlingpsl . com j www . sterlingpgharmasolutions . com
JAN / FEB 2024 SPECCHEMONLINE . COM
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