Crystallization Design Of Ethyl Vanillin

Ethyl vanillin is an artificially acquired organic compound which when industrially synthesized tends to return thin plate-like or needle-like crystals thereby causing a number of processing challenges including long isolation times,agglomeration,and poor flow and handling properties.This thesis provides experimental results based on crystallization design approaches incorporating thermodynamic and kinetic considerations as well as the physical properties important to the product performance of ethyl vanillin.The results from both the X-ray powder diffraction and the differential scanning calorimetry signify stability and the nonexistence of polymorphism in the investigated material.The solubility of ethyl vanillin was measured in the temperature range from 0 to 35 °C at atmospheric pressure via the conventional polythermal method employing a novel Turbidity Monitoring Technique which was validated by a gravimetric method.The dissolution enthalpy and entropy of ethyl vanillin are then computed from the solubility data using van't Hoff equation.At a mole fraction solubility of 0.0978 and an agitation speed of 400 rpm,the effects of different heating and cooling rates on the dissolution and nucleation temperatures were also determined.It is evident that the dissolution temperature is not significantly affected by the rate of heating whereas the nucleation temperature varies considerably when the cooling rate is varied.In the evaluation of the nucleation kinetics from the measured metastable zone width data,two approaches are utilized;the self-consistent Nyvlt-like approach and the approach based on 3D nucleation.Furthermore,the measured metastable zone width slightly decreases with increasing agitation rate.In optimizing the crystal shape and particle size,new solvents,thermal digestion,and sonication were found to have a considerable impact on both parameters.Two approaches are used in establishing the shapes and sizes of the product crystals.Microscopic images are used for observing the resulting crystal habits while the particle size distribution(% volume)approach is used in quantifying the sizes of the crystals.Pure acetone as solvent coupled with sonication shows the most significant change in particle size,yielding a thick blade crystal habit.At 8 cycles of thermal digestion,the binary solvent of isopropanol and water gives the targeted prismatic habit which was confirmed by use of in situ microscopy.Some crystallization design requirements of ethyl vanillin still remain unaddressed.However,the kinetic and crystal structural approach used in this thesis can lead to an improved fundamental understanding of the crystallization processes.