Ing. Químico

2012 International Conference on Solid State and Materials Lecture Notes in Information Technology, Vol.22

Production of Benzaldehyde by Liquid-phase Catalytic Oxidation of Toluene Ge Peng
Ningbo University of Technology, China Email: gepengv@hotmail.com Keywords: Benzaldehyde; Catalytic oxidation; Toluene

Abstract. MC （Mid-Century Company） method is one of the most important process inthe field of petrochemical industry, in which hydrocarbons are oxidized to aldehydes and acids using organic acid as solvent in the presence of catalysts consisting of cobalt acetate, manganese acetate and bromine compound. The liquid phase catalytic oxidation of toluene is discussed in this paper. The experiments are carried out in both pure toluene and solvents. During the process of liquid-phasecatalytic oxidation in pure toluene, the catalytic efficencies of different catalysts were not significantly different. The addition of bromine improved the catalytic efficency significantly. The rates of toluene oxidation in solvents were significantly higher than that in pure toluene, and the yield of benzaidehyde is improved. 1. Introduction Benzaldehyde, also known as benzoic aldehyde, is oneof the most important aromatic alcohols in modern industry. Rhone-Poulenc Company in France obtained phenylmethanol, benzaldehyde and benzenecarboxylic acid by liquid-phase air oxidation of toluene in the 1960s. The transformation rate of toluene was about 20% and the selectivity of benzaldehyde was 30%-50%. Many scholars argue now that the homogeneous catalytic oxidation of toluene follows themechanism of free radical reaction. Firstly toluene is transformed into peroxide and then decomposed into free radicals with catalysts, in the meantime, metal ions can realize the oxidation reduction cycle and function in transporting electrons and accomplishing electron transfer1, 2. Currently available references 3-9 mainly focus on the effects of catalysts on the oxidation of toluene, thoughsome achievements have been obtained, the yield of benzaldehyde was still relatively low. The present work was carried out to investigate the production of benzaldehyde by liquid-phase catalytic oxidation of toluene. The optimal reaction conditions were obtained to provide reference for industrial design and implementation process by firstly exploring the effects of different catalysts in puretoluene and catalyst concentration on toluene oxidation, and then comparing the difference between pure toluene oxidation and toluene oxidation in different solvents. 2. Experimental The experiment was carried out in different lots. First, the reaction raw materials, solvents and catalysts were prepared into 300 ml solution at certain proportion. The solution was added into the reactor and the air inthe reactor was exhausted by introducing nitrogen gas after tight sealing. Pressurization was carried out with nitrogen gas to a final pressure at about 1 MPa. The inlet valve and the outlet valve were shut off. The power supply was switched on for heating. The
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valve for cooling water in the end gas condensation tube was switched onat the same tim e, and the stirring was started. Nitrogen gas was continuously introduced during the process to increase temperature so as to guarantee the synchronized increase of pressure and temperature. After the temperature and the pressure were increased to the preset values, the heating power was adjusted in order to maintain the temperature constant in the reactor. The stirring speed wasadjusted to 900～950 rpm. Finally the nitrogen gas was switched to the air and the reaction was triggered. Sampling was carried out periodically during the reaction, and the ingredients in the sample were determined by using a HP6890-MS5973 gas chromatograph-mass spectrometer. Quantitative analysis was carried out by using a Shimazu GC-9A gas chromatograph. The chromatographic column was a SE-54...