Continuous process for preparing menthol in pure or enriched form
a technology of menthol and continuous process, applied in the field of continuous process for preparing racemic or optically active menthol, can solve the problems of high yield loss of known processes, and achieve the effects of low apparatus complexity, high yield loss, and high purity
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example 1
[0085]A laboratory dividing wall column was constructed from five glass sections, each of length 1.2 m, with internal diameter 64 mm. A dividing wall made of sheet metal was inserted into the three middle sections. Above and below the dividing wall region, laboratory packings (Sulzer CY) were installed and, in the dividing wall region, metal fabric rings made of stainless steel with diameter 5 mm. In separating performance measurements which were performed with xylene isomer mixtures at a top temperature of 60 mbar, an overall separating performance of 100 theoretical plates over the entire column and about 55 theoretical plates in the dividing wall region was measured. The total number of theoretical plates present was thus about 155. The column was equipped with an oil-heated thin film evaporator (0.1 m2) and a condenser cooled with cooling water.
[0086]Temperatures at different levels in the column and the top pressure and the pressure drop over the column were measured by means o...
example 2
[0092]In the middle of the column at a height of 331 cm, 900 g / h of liquid L-menthol of synthetic origin were fed to the dividing wall column in the feed section of the dividing wall, which had been obtained by catalytic hydrogenation of L-isopulegol over a nickel catalyst, and comprised 99.39 GC area % L-menthol, 0.29 GC area % isopulegol, 0.25 GC area % neomenthol and 0.011 GC area % isomenthol, and also 0.044 GC area % neoisomenthol. The column was operated at top pressure 50 mbar and a return rate of 3.0 kg / h. A pressure drop of about 35 mbar (±1 mbar) was established. At the top of the column, a temperature of 120° C. was measured, and in the bottom a temperature of 135° C. (±0.5 K). The column was operated without a bottom draw and the distillate withdrawal was adjusted by means of a balance control system to 15 g / h (±1 g / h). The reflux ratio was thus about 200:1. The condenser of the column was at a temperature of 40° C. in order to prevent solids formation.
[0093]The liquid w...
example 3
[0095]A further laboratory dividing wall column was constructed from three glass sections with internal diameter 43 mm. The middle column section with a total length of 105 cm was provided with a glass dividing wall of thickness about 1 mm which had been fused in a fixed manner. In the region of the dividing wall, the column is equipped with 1 m of Sulzer DX packing on the feed side and 0.9 m of DX packing on the withdrawal side. Above and below the dividing wall, glass sections of length 50 mm were used, each of which was equipped with 33 cm of Sulzer DX packings.
[0096]In separating performance measurements which were carried out with xylene isomer mixtures at a top pressure of 60 mbar, a total separating performance of about 32 theoretical plates over the entire column and about 18 theoretical plates in the dividing wall region was measured. The total number of theoretical plates present was thus about 50. The column was equipped with an oil-heated thin film evaporator (0.1 m2) an...
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Abstract
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