The invention relates to a preparation method of lilial. The preparation method of lilial comprises the following steps that p-tert.-butyl-
benzaldehyde,
methanol and caustic soda flake solutions having different concentrations are added into a reactor; n-propanal is dropwisely added into the reactor at a certain temperature and undergoes a
condensation reaction and after addition of n-propanal isfinished, the
condensation reaction lasts for 0.5 to 2 hours under the condition of heat preservation; acidic materials are added into the
reaction system to adjust a pH value and to stop the
condensation reaction; after the condensation reaction is finished,
methanol is recovered by
distillation and a condensation product p-tert.-butyl-alpha-methyl phenyl
acrolein is obtained by film
evaporator distillation;
methanol, p-tert.-butyl-alpha-methyl phenyl
acrolein and a hydrogenation catalyst are added into a hydrogenation reactor;
hydrogen is fed into the hydrogenation reactor and the mixture in the hydrogenation reactor undergoes a
hydrogen reaction; and after the
hydrogen reaction is finished, the reaction products are subjected to filter pressing,
solvent removal and rectification so that a finished product lilial is obtained. Lilial obtained by the preparation method is a colorless and transparent liquid, and has a
refractive index (nd20) of 1.504 to 1.506, the
specific gravity (25 DEG C, mg / mL) of 0.942 to 0.946, an
acid value (mgKOH / g) of 2.0(max.), the
GC content (determined by an area normalization method) of m-LLY less than 2.0%, p-LLY great than or equal to 97.0% and m-LLY+p-LLY great than or equal to 98.0%, and the
moisture content less than or equal to 0.25%.