Synthesis Of Benzaldehyde

Hydroxybenzaldehyde has three kinds of isomers,such as P-Hydroxybenzaldehyde(PHB),O-Hydroxybenzaldehyde(OHB)and M-Hydroxybenzaldehyde(MHB),which is the key to chemical intermediate,is widely used in industry fields.However,the production technology is not perfect,and can’t meet the needs of the market.Integrated point of the Hy droxybenzal dehy de synthesis methods’ overview,the preparation method for catalytic oxidation which used cresol as raw materials,is operating convenience,higher yield and pollution free.It has a good prospect.However,the method also has the problem of excessive use of alkali and the explosion of the reaction system.Therefore,there are production pollution and security risks in the actual industrial.The paper selected the methanol solution as solvent,pure oxygen as oxidizing agent,cobalt salt as catalyst,and then catalytic oxidized the cresol in the alkaline solution of sodium hydroxide by inflating oxygen intermittently,which can improve safety by avoiding explosion.The catalytic oxidation experiments of benzaldehyde were carried out by single factor method.Got the optimum extraction conditions,so as to improve the conversion rate of reaction to a certain extent,and the yield of target product.The reaction process was optimized,the reaction of liquid and toluene was used to solve the problem of pollution emission in the separation phase.Firstly,in this paper,we confirm the feasibility of using nitrogen gas to realize the safe production.Furthermore,the process conditions were studied,got the best conditions of the reaction as followed:temperature is 75℃,reaction time is 8h,the molar ratio of sodium hydroxide and p-cresol is 3:1,and the molar ratio of methanol and p-cresol is 13:1.In this conditions,the conversion of p-cresol is 93.64%,the yield of p-hydroxybenzaldehyde is 87.21%.The recovery and reuse of sodium hydroxide and the purification of product were studied in the separation phase.The recovery rate of sodium hydroxide was obtained by the method of toluene azeotrope,and the feasibility of sodium hydroxide was proved by comparing the experimental results with 82.25%.In addition,the purification of the product was studied and optimized,got the best conditions of the purification:operating temperature 10℃,operating time 12 h,toluene as solvent,and attapulgite as adsorbent.Under this condition,the purity of the product can reach 97.87%.On the basis of the above research,the above process was extended to the catalytic oxidation of o-cresol,got the best conditions of reaction as followed:temperature is 70℃,reaction time is 9 h,Co(OAc)2 used as catalyst,Cu(OAc)2 used as cocatalyst,and the quality ratio of methanol and o-cresol is 5:2:100.In this conditions,the conversion of o-cresol is 90.84%,the yield of o-hydroxybenzaldehyde is 85.36%.And got the best conditions of the purification:operating temperature 5℃,operating time 12 h,toluene as solvent,and active carbon as adsorbent.Under this condition,the purity of the product can reach 97.54%.Equally,the above process was extended to the catalytic oxidation of m-cresol,and got the best conditions as followed:temperature is 70℃,reaction time is 8 h,CoCl2 used as catalyst,CuCl2 used as cocatalyst,and the quality ratio of methanol and m-cresol is 5:2:100.In this optimum reaction conditions,the conversion of m-cresol is 91.53%,the yield of m-hydroxybenzaldehyde is 84.29%.And got the best conditions of the purification:operating temperature 10℃,operating time 8 h,toluene as solvent,and attapulgite as adsorbent.Under this condition,the purity of the product can reach 97.03%.