Melt crystallization of isomeric long-chain aldehydes from hydroformylation

• Melt crystallization is a method of choice for separating isomeric long-chain aldehydes.
• Separation problem caused by chemical instability of aldehydes solved with stabilizers.
• Isomeric aldehydes with chain lengths of C11 to C13 form eutectic solid-liquid equilibria.
• Measurement of growth rates and purities in a lab-scale layer crystallizer.
• Precise mathematical description of sweating by improving a method from literature.

This work evaluates comprehensively the potential of melt crystallization for the separation of the commercially important isomeric long-chain aldehydes. This was investigated with aldehydes of different chain lengths. A broad range of physical parameters was determined and related phase-equilibria were measured and modeled. Achievable growth rates and the corresponding purities were studied in static layer-melt crystallization experiments as function of chain length, cooling rate and concentration. Since aldehydes are highly reactive compounds, two methods were evaluated to guarantee chemical stability during crystallization. Furthermore, the efficiency of sweating was experimentally investigated and mathematically modeled as a function of chain length, temperature, crystal purity and crystalline layer thickness in high accordance to the experimental data.