Key Parameters Impacting the Crystal Formation in Antisolvent Membrane-Assisted Crystallization.

Area of Science:

• Chemical Engineering
• Crystallization Science
• Materials Science

Background:

• Antisolvent crystallization is vital for heat-sensitive compounds like active pharmaceutical ingredients.
• Membranes enhance control over antisolvent mass transfer, preventing local supersaturation and improving crystal quality.
• Optimization of operating conditions is crucial for membrane-assisted antisolvent crystallization.

Purpose of the Study:

• To investigate the impact of solution velocity, antisolvent composition, temperature, and gravity on membrane antisolvent crystallization.
• To evaluate the effectiveness of polypropylene flat sheet membranes in controlling crystal properties.
• To establish correlations between operating conditions, transmembrane flux, and crystal characteristics using glycine as a model system.

Main Methods:

• Utilized glycine-water-ethanol as a model system for antisolvent crystallization.
• Employed polypropylene flat sheet membranes to control antisolvent addition.
• Varied operating parameters including solution velocity, antisolvent composition, temperature, and gravity.
• Analyzed crystal size distribution (CSD), crystal shape, and polymorphic form.

Main Results:

• Membrane crystallization consistently yielded a narrow CSD (CV 0.5-0.6) compared to batch methods (CV 0.7).
• Glycine crystal shape was generally maintained, with minor edge smoothing at 35 °C.
• Mean crystal size (23-40 µm) increased with higher temperature or gravity resistance, correlating with antisolvent transmembrane flux (0.0002-0.001 kg/m²·s).
• The monoclinic form of α-glycine was preserved under all tested conditions.

Conclusions:

• Membrane antisolvent crystallization provides a robust method for achieving consistent crystal properties.
• Optimal operating conditions are key to maximizing the benefits of this technique.
• The control over mass transfer offered by membranes leads to superior crystal characteristics compared to conventional methods.