Batch Rectification of Rye Agricultural Distillates: Effect of Initial Ethanol Concentration on Volatile Congener Distribution

Batch rectification of agricultural distillates is a process in which the separation of volatile compounds depends both on their physicochemical properties and the composition of the purified mixture. The aim of this study was to assess the impact of initial ethanol concentration on the separation of selected congeners during batch rectification of rye agricultural distillates. Three agricultural distillates were rectified at initial ethanol contents of 40, 45, 50, 55, and 60% v/v, with four independent processes conducted for each variant and seven successive fractions collected. The content of volatile compounds was determined by the GC-FID method, and their distribution was assessed based on concentrations, recoveries, and their share in individual fractions. The effect of initial ethanol concentration varied among compounds and distillates. Acetaldehyde and ethyl acetate were recovered mainly in the head fractions, while C4 and C5 alcohols were shifted towards later rectification fractions. Methanol was present in all collected fractions and its total recovery was close to 100%, while 2-propanol stayed mostly in the main heart fraction. In all variants, the recovery of 1,1-diethoxyethane exceeded 100%, indicating that physical separation alone could not explain its behaviour. None of the initial ethanol concentrations tested in the still pot were the most favourable for the separation of all analysed volatile compounds across all three agricultural distillates.