Chemical Synthesis Of O-phenylphenol

Orthophenylphenol(hereinafter abbreviated as OPP), is an industrial chemical with a wide variety of applications as dye intermediate products, photographic chemicals, additives in rubber industry and bactericides of low toxicity.OPP was produced chiefly as a by-product of the alkali hydrolysis of chlorobenzene, or sulfonation fusion for the syntheses of phenol. But those two process routes were complicated and operated in poor working conditions. Especially after that phenol was industrially prepared from cumene, the above two routes were superseded, consequentially the supply of OPP has gradually dried up. So it's urgent for us to research and develop new safety environmental technology. Among all the possible routes of preparing OPP, the condensation and dehydrogenation process from cyclohexanone has the most extensive applied prospect.A method of preparing OPP in a two-stage process from cyclohexanone which comprises the steps of forming o-cyclohexenylcyclohexanone(hereinafter abbreviated as dimer) from the cyclohexanone by condensing, and then dehydrogenating the resulting dimer with dehydrogenation catalyst on which emphasis was laid, was studied. At the same time, the optimal process conditions and methods for condensation and dehydrogenation were also presented, together with the process for industrial production. The product was confirmed by m.p. measure, element analysis, IR, MS, and GC.Effect on condensation of cyclohexanone catalyzed by several catalysts werediscussed, together with selectivity and yield of dimer caused by reaction time and temperature, catalyst amount. The experiments indicated that, the process of cyclohexanone condensation carried out at the temperature of 90 to 100#, for 45 to 50 minutes catalyzed by 50% sulphuric acid, was a simple and effective one. At the end of reaction the phases were separated and the upper organic phase was neutralized with a solution of sodium bicarbonate, then the product was separated by distillation into dimer and cyclohexanone for recycle. The aqueous phase at the end of the reaction contained sulphuric acid and a substantial amount of organic material, which was therefore made up with fresh sulphuric acid and used in the preparation of the next batch.The preparation of dehydrogenation catalyst was the most difficult work among the whole experiments. Ten different lands of supported noble metal catalyst were prepared by the soaking method, and dehydrogenation was conducted with those 10 catalysts, respectively. It was found the Pt-KOH/ Y -Al₂O₃ catalyst was the most effective one, Investigation of changes in composition of the resulting liquid product with the lapse of reaction time revealed that the content of OPP was at least 95% at the beginning and 64% after the lapse of 177.5 hours. And at the same time, the reasons that caused the catalyst deactivation were also investigated, based which the catalyst was improved. The method of reactivation was proved, too.The dehydrogenation was carried out in present of several catalysts at different reaction conditions, respectively, from which it was found that, if the dimer was fed at a flow rate of 30g/hr in a maintained at 340³60#, together with hydrogen and nitrogen supplied at a flow rate of 40ml/min respectively, ideal dehydrogenation products, which were able to crystallize immediately after they left the catalyst bed, were obtained. The content of OPP was 95% and could reach 97.2% after it was recrystallized by petrolic ether. And the fraction-dehydrogenation products were mixed with fresh dimmer, recycling to dehydrogenate.