Phenol separation from cyclohexanol

The reaction product was filtered to remove catalyst and analyzed in GC equipped with an HP5 (30 m X 0.32 mm X 0.25 pm) column. The temperature program used for analysis (31 °C - 35 min - 1 °C/min - 40 °C - 10 °C/min -120 °C) ensured complete separation of the cyclohexanol, cyclohexanone, and phenol peaks. The conversion and selectivity were calculated directly from the area of each peak. 

The separation section receives liquid streams from both reactors. For assessment the residue curve map in Figure 5.7 is of help. The first separation step is the removal of lights. This operation can take place in a distillation column operated under vacuum (200mmHg) with a partial condenser. Next, the separation of the ternary mixture cyclohexanone/cyclohexanol/phenol follows. Two columns are necessary. In a direct sequence (Figure 5.15) both cyclohexanone and cyclohexanol are separated as top products. The azeotrope phenol/cyclohexanol to be recycled is the bottoms from the second split In an indirect sequence (Figure 5.16) the azeotropic phenol mixture is a bottom product already from the first split. Then, in the second split cyclohexanone is obtained as the top distillate, while cyclohexanol is taken off as the bottom product The final column separates the phenol from the heavies. 

Because phenol (CeHsOH) is less acidic than a carboxylic acid, it can be deprotonated by NaOH but not by the weaker base NaHCOa- Using this information, write out an extraction sequence that can be used to separate CeHsOH from cyclohexanol. Show what compound is present in each layer at each stage of the process, and if it is present in its neutral or ionic form. 

The fact that phenols are weakly acidic, whereas alcohols are neutral, provides a convenient way to separate phenols from water-insoluble alcohols. Suppose that we want to separate 4-methylphenol from cyclohexanol. Each is only slightly soluble in water therefore, they cannot be separated on the basis of their water solubility. They can be separated, however, on the basis of their difference in acidity. First, the mixture of the two is dissolved in diethyl ether or some other water-immiscible solvent. Next, the ether solution is placed in a separatory funnel and shaken with dilute aqueous NaOH. Under these conditions, 4-meth-ylphenol reacts with NaOH to give sodium 4-methylphenoxide, a water-soluble salt. The upper layer in the separatory funnel is now diethyl ether (density 0.74 g/cm ), containing only dissolved cyclohexanol. The lower aqueous layer contains dissolved sodium 4-meth-ylphenoxide. The layers are separated, and distillation of the ether (bp 35°C) leaves pure cyclohexanol (bp 161°C). Acidification of the aqueous phase with 0.1 M HCl or another... 

---