How to Prepare APG with Direct Glycosylation
Direct glycosylation is the most widely used method in the industrial production of alkyl polyglucoside.
Alkyl polyglucosides (APG) were produced in the reaction by long chain fatty alcohol and glucose in the catalysis of protonic acid. The reaction equation is expressed as below:
The direct method is to use the fatty alcohol of C8 ~ C16, which reacts with glucose directly to produce APG in a certain temperature and catalyst condition.
In addition to the commonly used catalysts such as sulfuric acid and p-toluene sulfonic acid. Some acidic catalyst such as dodecyl benzene sulfonic acid, dodecyl sulphonic acid, an alkyl naphthalene sulfonic acid. They all have the emulsifying property which is more help indican and also can reduce the generation of chitosan.
The acetalization is reversible. The high carbon alcohol ROH needs to overdose. So the reaction product contains a large amount of high carbon alcohol.
The rest high carbon alcohol reduces the quality of the product. For this reason, it is very necessary to remove excess alcohol after the reaction is completed.
Although alcohol can be removed by using vacuum distillation method, that still need a high temperature (for example, lauryl alcohol boiling point 255 ℃ ~ 259 ℃, stress condition also need to about 160 ℃ ~ 180 ℃ to be removed). The alkyl indican are heat-sensitive material. It will be influenced by an acidic catalyst and colored substance generated in the reaction process. Alkyl polyglucoside is also easy to become black even coking in short of the vacuum distillation temperature. Therefore, dealcoholization should be carried out in a high vacuum and minimize the reaction temperature and shorten the heating time.
The known dealcoholization methods include:
(1) The thin film evaporator is used in high temperature and short stay time.
(2) Add a high boiling solvent containing hydroxyl to dealcohol.
(3) Add high boiling point polar solvent to reduce viscosity, then dealcohol.
(4) By adsorption and separation to purify. The crude products can be absorbed by the adsorption column, then remove the ROH with the deattached agent of ROH, and recycle the deattached agent, and the ROH is used circularly.
At last, the glucoside is eluent with the deattached agent of glycosides, then get glycoside by removing the agent.
(5) Two steps method to dealcohol. The first step is to reduce the alcohol content in the film evaporator directly to about 20% ~ 40%.
The second step is to reduce the alcohol content to 3% ~ 5 % in the short-range evaporator.
Although the application of these methods has improved the effect of alkyl polyglucoside products, it also has raised the cost of production.
Direct glycosylation method has advantages of simple technology, and the products do not exist lower alcohol glycoside. But because of intermiscibility between long chain fatty alcohol and glucose is poor. A lot of higher alcohols will be added in the reaction. Because of high temperature and make the product become a dark brown during distilled off alcohol.
In the process of producing APG, IRO adopted a more advanced method, which did not improve the cost too much, but make the product quality higher.
It is because of IRO strictly control the APG quality. We can be recognized by the global clients so many years.
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