Rectification partly continuous

Separation of head fractions. The head fraction, which is obtained at the first stage of continuous rectification of methylchlorosilanes, from collector 20 self-flows into tank 44. The temperature in the tank in the beginning of the process is maintained at 60-70 °C, and at the end it should be from 90 to 95 °C. Vapours from the tank rise up tower 40 and enter reflux-ers 39, cooled with water and salt solution (-15 °C) from there, part of condensate is returned to reflux tower 40, and the rest is sent through cooler 38 into receptacles 41 and fed into collectors 43. 

From batch boxes 1 and 2 the original reactants in given quantities are sent into agitator 3, where they are mixed with nitrogen, which is fed from container 6, for 10-15 min. Before the installation is launched, reactor 8 is loaded to 2/3 of its volume with reactive mixture and electrically heated. The temperature is raised to 250-260 °C and after it is held for 5 hours, the reactive mixture from apparatus 3 is continuously fed through run-down box 4. The products formed are separated from the lower part of the reactor at 2-2.1 MPa. The products are sent through cooler 10 are sent into separator 11 and collector 72 from there they are sent to rectification. 

The average exit composition of the chlorination products is the following 3-3,5% of methyl(dichloromethyl)dichlorosilane, 11-14% of methyl(chloromethyl)dichlorosilane and 82.5-86% of unreacted dimethyldichlorosilane. The mixture is sent into the middle part of tower 7 for continuous rectification to distill the unreacted dimethyldichlorosilane and steam out the dissolved hydrogen chloride. 

The use of the top part of the packed tower as the chlorinator will also ensure good mass exchange between chlorination and rectification zones this will allow to quickly withdraw chlorination products from the reaction zone and continuously send back the unreacted dimethyldichlorosilane as a result of the rectification of the mixture in the lower part of the tower. However, this chlorination technique can be possible only with chemical initiators, not UV rays, since in the latter case the effect of light will be screened by the head. 

After approx. 48 h of fermentation, the fermented mash shows an alcohol content of approx. 6-10% by vol. When distilled in continuous stills with 3 or more colunms, the alcohol level in the distillate can be enriched up to 96.6% by vol. The purification of the raw distillate is normally carried out in continuous rectification equipment, for which the raw alcohol is usually diluted to approx. 15% by vol. before rectification in order to better separate fusel oil components. The first fractions of the rectified distillate - the so-called head fraction - contain significant quantities of acetaldehyde, methyl alcohol and low-boiling esters the middle part - heart fraction - represents so-called neutral spirits with an alcohol content of approx. 96.6% by vol. The tail fractions contain higher alcohols and higher esters etc. Since head and tail fractions contain organoleptic properties undesirable for neutral alcohol, they usually are employed as technical alcohol or have lately also been isolated and used as starting raw materials for the production of natural aroma components. 

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