Application of vacuum control in cyclohexane separation and purification

The temperature and vacuum used during separation and purification are important setting parameters during the use of a rotary evaporator. The saturated vapor pressure of a substance is a reference standard for temperature and vacuum control (see attached table).
* What is saturated vapor pressure?
Whether it is liquid or solid, there is evaporation (sublimation) and condensation at all times, and the gas molecules after gasification will exert pressure on the surface of the material. Vapor pressure refers to the vapor of the substance present on the surface of a liquid or solid, the pressure exerted on the surface of the liquid or solid.
Saturated vapor pressure refers to the vapor pressure of a substance at that time when the evaporation (sublimation) of the substance and the condensation are in a dynamic equilibrium state in a closed condition, at a certain temperature and pressure.
Taking common water as an example (pure water), in a closed container, the air is pumped away, and the water will evaporate continuously. The saturated vapor pressure formed by the vapor will vary with temperature. If the temperature is stable at 100 ° C, the vapor will continue to form until the vapor pressure reaches 101.32 kPa, which is the saturated vapor pressure of the water at that time. At this time, if the temperature is no longer raised, the vapor pressure of 101.32 kPa, and then the steam continues to be produced, but at the same time there will be an equal amount of steam re-condensed into water, forming a balance, the pressure no longer rises; if the temperature is 30 °C, then the vapor pressure of water vapor will not exceed 4.2455kPa; at 20 °C, the saturated vapor pressure is 2.3388kPa.
* Vacuum control and rotary distillation Separation and purification of the rotary evaporator in the process of separation and purification, taking into account the degradation of the target product at high temperatures or molecular structure damage. Therefore, it is necessary to carry out separation and purification at a lower temperature. The saturated vapor pressure of the separation reagent is formed at a lower temperature, and it is necessary to evacuate by means of a vacuum pump. By controlling the degree of vacuum, the mixed solvent can be rapidly separated and purified below the safe temperature at which the target product is denatured.


* WIGGENS anti-corrosion vacuum controller WIGGENS DVR480 anti-corrosion vacuum controller, dedicated to the vacuum control of rotary steaming. The lowest controllable vacuum is 0.1mabr, supports up to 5 segments of programming control, and enables efficient and automatic recovery of multiple solvents. The contact gas materials are all PTFE or high performance ceramics, which are resistant to acids, bases, and various organic solvent gases. Digital display, button control, USB digital interface, and analog input and output interface. It can be connected to the pump power supply control to temporarily shut down the pump power supply after reaching a stable vacuum level, which is energy-saving and environmentally friendly; it can also work in the normally open state of the pump.

* Schedule: Vacuum required for saturated vapor pressure (40 ° C) of common organic solvents

Solvent	Molecular formula	Saturated vapor pressure (mbar) at 40 ° C (104 ° F)	Molar mass (g/mol)
water	H2O	74	18.0
Carbon tetrachloride	CCl4	285	153.8
Trichloromethane	CHCl3	477	119.4
Formic acid	CH2O2	114	46.0
Dichloromethane	CH2Cl2	~atm.	84.9
Methanol	CH4O	352	32.0
Tetrachloroethylene (PCE)	C2Cl4	53	165.8
Trichloroethylene	C2HCl3	191	131.4
Pentachloroethane	C2HCl5	14	202.3
Trans-1,2-dichloroethylene	C2H2Cl2	777	96.9
Cis-1,2-dichloroethylene	C2H2Cl2	488	96.9
1,1,2,2-tetrachloroethane	C2H2Cl4	19	167.8
1,1,1-trichloroethane	C2H3Cl3	307	133.4
Acetonitrile	C2H3N	229	41.1
Acetic acid	C2H4O2	47	60.0
1,2-dichloroethane	C2H4Cl2	214	99.0
Ethanol	C2H6O	178	46.1
acetone	C3H6O	563	58.1
Dimethylformamide (DMF)	C3H7NO	13	73.1
N-propanol	C3H8O	70	60.1
Isopropanol	C3H8O	136	60.1
Tetrahydrofuran (THF)	C4H8O	402	72.1
Butanone	C4H8O	265	72.1
(1,4-) dioxane ring	C4H8O2	102	88.1
Ethyl acetate	C4H8O2	251	88.1
N-butanol	C4H10O	25	74.1
Isobutanol	C4H10O	42	74.1
Tert-butanol	C4H10O	140	74.1
Ether	C4H10O	>atm.	74.1
Diethylamine	C4H11N	581	73.1
Pyridine	C5H5N	60	79.1
N-pentane	C5H12	>atm.	72.2
N-pentanol	C5H12O	11	88.2
Methyl tert-butyl ether	C5H12O	597	88.2
Isoamyl alcohol	C5H12O	14	88.2
chlorobenzene	C6H5Cl	34	112.6
benzene	C6H6	236	78.1
Cyclohexane	C6H12	250	84.2
Butyl acetate	C6H12O2	35	116.2
Hexane	C6H14	373	86.2
Diisopropyl ether	C6H14O	372	102.2
Toluene	C7H8	77	92.1
N-heptane	C7H16	124	100.2
Xylene	C8H10	27	106.2