Tungsten silicate is a tungsten heteropoly acid, its appearance is white or pale yellow deliquescent crystal, soluble in water and alcohol, soluble in crystal water itself.
When heated, it has decomposition when under 600~650°C. Tungsten heteropoly acid is often used as a catalyst, so as tungsten silicate.
Octyl acetate exist in citrus oil, green tea leaf oils and so on, it also exist in fruit. Octyl acetate is identified as non-toxic food by FEMA (the flavor and Extract Manufacturers Association). The preparation of octyl acetate can not be separated from the strong acid catalyst. Due to the oxidation and strong dehydration of concentrated sulfuric acid, the esterification rate is reduced, the quality of ester is poor, and the equipment is seriously corroded. A lot of waste liquid is produced in the post-treatment process, which pollutes the environment and so on.
Tungsten heteropoly acid is a kind of green environmental friendly catalyst, in recent years, in the food additives industry, it is widely used to replace traditional acid catalyst, it is efficient and environmentally friendly. Phosphotungstic acid and tungsten silicate is that kind of catalyst.
Method for preparing octyl acetate is that a certain amount of acetic acid, octyl alcohol and tungsten silicate in three bottles, oil bath is heated to a certain temperature, after stirring, reflux, and cooling down the reaction liquid, filtering to remove the catalyst, filtrate analysis by gas chromatography, to test the alcohol conversion rate and selectivity of octyl acetate. The optimum conditions for the preparation and esterification of the catalyst were determined by changing the amount of catalyst, the time of calcination, the molar ratio of acetic acid to octanol, the amount of catalyst, the reaction temperature and time. Through a series of evaluation we conclude that the suitable conditions for the catalytic esterification of tungsten silicate is that ratio of acid to alcohol is 1.3:1, the amount of catalyst 0.2g/0.1mol octanol, reaction time for 1H, reaction temperature is 100~118°C. Under this condition, the esterification rate can reach 99.30%.
Tungsten silicate has good catalytic activity in the synthesis of octyl acetate, it has short reaction time, high esterification rate, no waste acid discharge, simple process, the catalyst can be reused, therefore, tungsten silicate is an excellent catalyst for the synthesis of octyl acetate, it has a good prospect of industrial application.
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