Micronization of vanillin by rapid expansion of supercritical solutions process

Uniform microparticles of vanillin were precipitated by the Rapid Expansion of Supercritical Solution (RESS) process and this reduced the commercial particle size by a factor of one hundred. A design of experiments full factorial at two levels was performed. The effects that pressure, temperature, contact time and nozzle diameter had on the particle size and yield of the RESS precipitation were evaluated. Pressure and temperature were the factors that had the most marked effects on particle size and yield. The use of higher pressure and temperature is recommended to obtain the smallest particle size and the highest yield. However, at lower pressure the temperature is a crucial factor in that the use of a lower temperature led to considerably smaller particles and good yields whereas a higher temperature gave the highest particle size and the lowest yield. A higher contact time and smaller nozzle diameter led to slight improvements in the vanillin particle size and yield according to the results of the design. The crystallinity of the RESS-processed vanillin was unaltered when compared to the unprocessed material.