Study On The Synthesis Of P-phenylphenol

P-phenylphenol (PPP for short) is an important intermediate and it is starting material for manufacture of pharmaceuticals and dyes, etc. But at present, the manufacture of p-phenylphenol in China is unsatisfactory with low yield and high pollutions.The synthesis of p-phenylphenol was investigated and improved in this paper. The first step: In aqueous hydrochloric acid, phenol and cyclohexanone were condensed to give 1,1-bis(4-hydroxyphenyl)cyclohexane. The second step: In the presence of Pd/C catalyst, reaction of 1,1-bis(4-hydroxyphenyl)cyclohexane give p-phenylphenol by heating the reaction system to 200°C -350°C.Many factors which affect the reaction step 1 and 2, such as reaction temperature, reaction time, ratio of phenol to cyclohexanone, the dosage of hydrochloric acid (the first step); reaction temperature, reaction time, catalyst, inert gas (the second step) have been studied. The optimal reaction conditions are that, for step 1: the reaction temperature is about 60°C and the reaction time is 8h, the volume of phenol is 88mL, the volume of cyclohexanone is 13mL, the amount of hydrochloric acid (37%) is 20mL-40mL; For step 2: the reaction temperature is about 250°C and the reaction time is about 5h, the amount of 1,1-bis(4-hydroxyphenyl)-cyclohexane is 10g, the amount of 5% Pd/C is 0.5g; inert gas preferred is hydrogen(the second step). Under the optimal condition, the selectivity of p-phenylphenol was up to 90%.