Recovery of Theophylline in Effluent with 2-Ethylhexanol Extraction Process

Abstract

The 2-ethylhexanol extraction process is developed to recover theophylline in the effluent from the commercial synthesis of theophylline. The extraction of theophylline by 2-ethylhexanol depends on the pH, temperature, and Na2SO4 content in the effluent. The distribution ratio is 0.81 at pH 7 and decreases with increasing pH to near zero at pH > 8. Over 95% of the theophylline in the effluent can be recovered by 4-stage countercurrent extraction with a flow ratio equal to 2. The reciprocating plate column (RPC) was used successfully with a throughput of 3.4 t/h in the commercial process. The scaleup design was based on pilot test data and the Karr correlation. A Davy-McKee mixer-settler with sufficient resident time was used for stripping with 0.2 mol/L NaOH solution and a flow ratio of 10. After stripping, the 2-ethylhexanol was recycled for extraction. The stripping is governed by the molar ratio of NaOH in solution to theophylline in the loaded 2-ethylhexanol and by the contact time of the organic phase with the aqueous phase.