Process Design And Optimization Of Vanillyl Alcohol Crystallization

In this work,solubility,metastable zone width,characterization and optimization of vanillyl alcohol in different solvents were carried out.The solubility of vanillyl alcohol in eight pure solvents was conducted by using a static gravimetric method in the temperature range from293.15K to 343.15 K.It was found that the solubility values increase with the temperature rise.The solubility of vanillyl alcohol in ethanol is the highest while solubility in butyl acetate is the least among all the selected solvents.In addition,the modified Apelblat equation,the?h equation and the Wilson equation were used to correlate the experimental solubility.The thermodynamic properties of vanillyl alcohol in different pure solvents were investigated based on the Wilson equation and the experimental solubility data.Metastable zone widths of vanillyl alcohol in ethanol,2-propanol and acetone were experimentally measured by using a laser power system.Measured Metastable zone widths can be affected by a variety of parameters,such as cooling rate,saturation temperature,agitation rate,and so on.For all the three solvents,the metastable zone widths decrease with saturation temperature,while it increases with cooling rate.Three classical approaches,Nyvlt theory approach,self-consistent Nyvlt-like approach,and classical 3D nucleation theory approach were used to investigate the nucleation kinetics of vanillyl alcohol from the measured metastable zone widths.However,due to the physical significance of the nucleation constant k remains unclear in Nyvlt's approach,self-consistent Nyvlt-like approach and3D classical theory approach was found to be more reasonable.The results suggested that nucleation in ethanol can be regarded as instantaneous and follows poly nuclear(PN)mechanism,while nucleation in 2-propanol or methyl cyanide occurs progressively with high nucleation order.Furthermore,the effect of solvent,temperature,cooling rate,agitation speed,and seeding on crystallization process of vanillyl alcohol was investigated.The role of seeding was inhibition of nucleation so as only growth to occur.To control nucleation and crystal growth,for obtaining crystals of a specific size,both number and size of seed crystals must be optimized.It was found that vanillyl alcohol in ethanol at 60 ~0C with cooling rate of 0.5 ~0C/min,agitation speed of 300rpm,seed mass ratio of 0.1%,and seed size in the range of 150-200?m are optimum conditions.