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Experimental Study On The Process Of Liquid-phase Oxidation Of Toluene To Benzoic Acid And Its Engineering Design

Posted on:2016-06-17Degree:MasterType:Thesis
Country:ChinaCandidate:X Y DuanFull Text:PDF
GTID:2271330461457416Subject:Chemical Engineering and Technology
Abstract/Summary:PDF Full Text Request
Benzoic acid is an important chemicals and widely used in the production of pharmaceutical intermediates, food additives, cosmetics and chemical products. Liquid-phase oxidation of toluene has become the main method in industrial production of benzoic acid, due to having some advantages such as mild reaction conditions, simple production process and high safety. However, expensive petrochemical toluene, low effectivity of reactor and low purity product limit the development of benzoic acid production. Therefore, it is of great importance to explore the method of producing benzoic acid from coking toluene.In this thesis, coking toluene was used as raw material to produce benzoic acid with direct liquid phase oxidation. Experiments on the effects of operating conditions(temperature, pressure, oxygen partial pressure) and catalysts were made. The results show that temperature, pressure and oxygen partial pressure have a great influence on the reaction. Higher reaction temperature and higher pressure lead to higher toluene conversion and lower selectivity of benzoic acid and benzaldehyde. When cobalt naphthenate, or cobalt acetate was employed as the catalysts, the best adding quantity is 0.18%(wt). The optimal operation conditions are that the temperature is 165 ℃, the pressure is 0.65 MPa(G), content of oxygen is 21%, the quantity of initiating additive is 0.1%(wt). The experimental results show that it is feasible to use coking toluene as the raw material to produce benzoic acid.At the present, melt crystallization is the main method to produce the high purity benzoic acid. The experiments on melt crystallization were done to produce high quality benzoic acid with industrial-grade benzoic acid as raw material. The results show that the type of crystallizer has great effect on product qulity. The crystallizing effects of fine-type crystallizer and plate-type crystallizer and the purity of products are better than that of traditional tube crystallizer. The optimal conditions are as follows: Benzoic acid melting temperature is 124 °C, the cooling rate is 0.6 ~ 0.8 °C/min, the optimum crystallization temperature is 119 °C, the content of crystal is controlled between 60% and 65%. The sweating operating time is 50 minutes and terminal sweating temperature is 122 °C.Based on the above experiments, the desin of the engineering process with annual output of 30000 tons of benzoic acid was also made in this thesis, and the technology package was given. The technology package includes improved main equipment, material balance and energy balance for each unit operation, the flow chart of pipeline and instrumentation(PID), equipment selection calculation and the specifications of the main equipment, summary list of the process equipment and typical equipment for the control scheme.
Keywords/Search Tags:Coking toluen, Liquid-phase oxidation, Benzoic acid, Melt crystallization, Technology package
PDF Full Text Request
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