Liquid-phase Oxidation Toluene To Benzaldehyde With Air

This thesis studied the process for the production of benzaldehyde by liquid-phase oxidation toluene with air in a systematic way. The choices of catalysts and cocatalysts, and the effects of various process parameters, such as the dosage of catalyst and cocatalyst, reaction temperature, reaction pressure, reaction time, rate of air flow, oxidation promoter on the selectivity and yield of benzaldehyde were investigated. The process conditions of liquid-phase oxidation toluene to benzaldehyde with air was optimized by the uniform design method.The results indicated that: (l)the reaction of oxidation toluene to benzaldehyde was in the first order series reaction at 165 C. The reaction rate constant k1 was 0. 001835 min-1 and k2 was 0.01248 min-1; (2) the selectivity and yield of benzaldehyde were high with WULCo as catalyst; (3) BR as cocatalyst could greatly shorten the induction period and increase the selectivity and yield of benzaldehyde; (4 ) the reaction rate was low with too small dosage of catalyst. And when the dosage of catalyst increased, the reaction rate increased. However, if there was too large amount of the catalyst, the selectivity and yield of benzaldehyde were decreased. When the dosage of catalyst range from 1. 5% to 2. 5%(W), the yield of benzaldehyde was high; (5) the reaction rate, the selectivity and yield of benzaldehyde were affected by the ratio of catalyst and cocatalyst. The experiments indicated that when the mole ratio of Br to Co was 1. 5-2. 5, the yield of benzaldehyde was high; (6) the laden factor of the reactor affected the dwell time of air in the reactor directly, and the results of the reactions. When the laden factor was about 0.58, the yield of benzaldehyde was high; (7) the reaction time deeply affected the yield of benzaldehyde. The reaction time was too short, the conversion rate of toluene was low, and the yield of benzaldehyde was low even if its selectivity was high. On the contrary, the reaction time was too long, toluene was oxidized deeply, the yield of benzaldehyde decreased; The experiments indicated that the best range of the reaction time was 120-180min; (8) reaction temperature and pressure affected oxidation reaction. Reaction rate could increased with higher reaction pressure. Whenthe reaction temperature was 160-170 C,and the reaction pressure was 0.6MPa, the yield benzaldehyde was high; (9) the yield of benzaldehyde was high when the average rate of air flow was 1.6-2.0L/min in the whole reaction process.The dosage of WULCo (X1), the mole ratio of Br to Co (X2), the reaction time (X3), and the rate of air flow (X4) were the main factors that affected the reaction. The four factors were investigated by the uniform design method. The regression equation was obtained by calculating and analyzing of the experiment data:The regression equation was optimization calculated. The optimal process conditions were obtained on the basis of the specialized knowledge and the experiments: the dosage of WULCo (X1)2.0%, mole ratio of Br to Co(X2)2.25, reaction temperature (X3)165 C, average rate of air flow (X4)2.0 L/min, reaction pressure 0.6MPa, reaction time 165min. The repeated experiment carried out according to the optimal process conditions. The conversion rate of toluene was 26.8%, and the yield of benzaldehyde was 12.2%. It agreed with the theoretical result.The separation of products and the reuse of the catalyst were studied. The purity of benzaldehyde was more than 98%.