Catalytic Hydroxylation Of Phenol With CuTHPP/γ-Al₂O₃ As Catalysts

Metalloporphyrin is the organic with the special structure similar to cytochrome P450. It has been used in biomimetic catalytic reaction, they play an important role in areas of biomimetic oxidation. Dihydroxybenzenes are an important class of chemicals used as chemical intermediates and other purposes which are still largely abroad-supplied. their efficient preparation has been an urgent problem and catalytic hydroxylation of phenol to prepare dihydroxybenzenes affords a clean and efficient production technology. At present,metalloporphyrins for catalytic oxidation of alkanes and alkenes are widely studied, while their catalysis for the reaction of phenol hydroxylation is still rarely reported. Therefore, the thesis explores the availability of copper porphyrin to catalysis phenol hydroxylation reaction for speeding up the development of advanced hydroquinone preparation technology.Cu THPP/γ-Al₂O₃ catalyst was prepared by impregnation and identified by means of 1H NMR、 FT-IR、 UV-vis、 EDX、 XRD、BET and TG. The characterization results demonstrated that Cu THPP was physical-adsorbed on the surface of γ-Al2O3. With the phenol hydroxylation as a model reaction, the highest conversion of phenol reached to 36.8% and the highest selectivities to catechol and hydroquinone 7.3:1 at proper condition. The 5 times reusability experiments of catalyst illustrated its stable activity.The cylinder-shaped catalyst were prepared by extruding process with guar gum as adhesive and used for hydroxylation of phenol in fixed-bed rector. The activity of the shaped Cu THPP/γ-Al₂O₃ catalyst for phenol hydroxylation was evaluated. The effect of reaction condition on the activity of catalyst were investigated,The optimal reaction condition was determined as follows: the reaction temperature is 60 ℃, the space-time speed 4.0 h-1, phenol and hydrogen peroxide（mass fraction 30%） molar ratio of 3:1, in such conditions, the conversion of phenol was 25.2%, catechol and hydroquinone selectivity were 79.2% and 19.8% respectively. In order to determine whether the catalyst has a long time catalytic activity, experiments was also conducted to investigate the activity change of the catalyst within 24 h. The results showed that the activity of shaped Cu THPP/γ-Al₂O₃ catalyst shows minor change within 24 h, indicating good activity stability.