Effects of Mixing on Adipic Acid Crystallization Susan Philyaw, Kathryn Baker, Randal Nelson, Jessica Moffitt, Joy Sroykum and Dr. Terry Ring

Outline of Talk Introduction- What is Adipic Acid? Background- Purpose for Study. Previous Research- Comparison. Experimental System- Equipment. Experimental Procedure- How we did it. Results- What we found Conclusions

Introduction Adipic acid = 2 Billion tonne /yr. Adipic acid used in Nylon Manufacture WH. Carothers’ at Dupont discovered Nylon in 1930’s Adipic acid is a natural product found in some plants Adipic acid is produced by an oxidation reaction oxidation of cyclo-hexane oxidation of phenol (minor route). Other uses Resins, Polyurethanes, and Plasticizers

Background Purpose of study: Increase Quality Control Adipic acid is crystallized from an aqueous solution by cooling. Aggregation/Agglomeration Advantages: Easy to Filter Challenges: Difficult to control crystal size distribution Adheres to the reactor walls and other parts Aggregates trap impurities/solvent in the voids of particles

Previous Research Rene David’s Paper Stirred tank with cooling Aqueous Adipic Acid Solution S. Derenzo’s Paper Batch with cooling Aqueous Solution of Adipic Acid Ethanol Solution of Adipic Acid A. Meyerson’s Paper Batch with cooling Alcohol Solution of Adipic Acid Tulock’s Paper Batch with cooling Aqueous Adipic Acid Solution Cesar and Ng Batch with cooling Aqueous Adipic Acid Solution Williams-Seton, et. al. Batch with cooling Aqueous Adipic Acid Solution

Experimental System Reactor- Continuous Stirred Tank (CSTR) Volume: liters Operating Condition Impeller RPM: varied 400 to 800 rpm Flow rate: held constant ml/min Reactor Temperature T=15 C. Solution Properties Concentration and Temperature 18.2 gm/liter at 22.0 C.

Solubility

On-Line Analysis – Computer Data Logging Feed Flow Rate Product Flow Rate Reactor Temperature -  Stirrer RPM -  Stirrer Torque -  Heat Balance - 

Tank Internals

Off-line Analysis Steady State Sample Yield Particle Size Distribution Beckman Coulter LS-230 (40 nm to 2000µm) Particle Morphology SEM

Residence Time Measurements Time(min) T,C Time(min) T=(T o -T in )exp(-t/tau)+T in

Residence Time Measurements Pulse Addition to Steady State CSTR Visual – Blue Dye Salt – Conductivity Hot – Temperature Acid – pH converted to H + concentration Done Simultaneously All the results are similar!

GOOD vs BAD MIXING 300 RPM 20 RPM

Mean Residence Time Results V reactor ~ 1280 ml

RDT Variance Results

Experimental Procedure Saturated Solution of Adipic acid feed to CSTR Mean Residence time of 10 minutes Steady state time of 50 minutes Flow rate constant 120 ml/min Rpm of impeller varied - 400, 800 rpm Samples taken at steady state Sample filtered, dried weighed to get yield PSD, Beckman-Coulter LS 230 small volume particle distribution unit Particle Morphology - SEM

Results-2 – 400 rpm

Results rpm 50 micro meters500 micro meters

Results-3 Yield 400 rpm64±5% 800 rpm61 ±5 % Particle Size Distribution

Conclusions Mixing speed must be greater than 200 rpm Ideal Mixing in Stirred Tank Mixing speed controls the aggregate size Smaller aggregates give less impurities Smaller aggregates are more difficult to filter

Acknowledgement DOE/OIT Industries of the Future Research Program