Reaction And Separation Process Research Of Glyoxal Produced With Acetaldehyde

Glyoxal is a kind of important chemical material and intermediate with a widerange of applications in printing and dyeing textile, medicine, paper making et al.Especially with the development of pharmaceutical industry, there is an increasingdemand for high-purity glyoxal gradually. At present, the industrial manufactureprocess suffered from severe pollution, lower purity, high energy consumption, lowyields and tends to explode et al.. While the production process of glyoxal fromacetaldehyde has merits of higher quality product and lower power consumption etc..The reaction mechanism, synthesis and separation process of the method of nitric acidoxidizing acetaldehyde were investigated intensively in this paper. And the researchcontents are as follows:Ion-exclusive chromatography analysis was selected to analyze glyoxal solution.Qualitative analysises of each component in glyoxal solution were obtained with theapplication of differential refraction detector, column aminex HPX-87H and dilutesulphuric acid as the mobile phase. Quantitative analysis of glyoxylic acid, glycollicacid, oxalic acid, formic acid and acetic acid et al. was estabilished by externalstandard method. Then the rapid and accurate analysis for the oxidation solution wasachieved.The possible formation mechanism of the principal product and byproduct in thereaction system of the glyoxal preparation with the method of nitric acid oxidizingacetaldehyde were deduced by means of oxidation process analysis. It can beconsidered that the reactions were conducted in term of free radical mechanism. Theformation kinetics of glyoxal, formic acid and acetic acid were researchedexperimentally and the kinetic models of the three reactions were concluded.Nitric acid separation using electrodialysis technique was researchedexperimentally. The experiments were conducted in electrodialysis equipmentequipped with membrane J-1-18. The mass transfer equation was established and themass transfer model was obtained. The effects of membrane stack voltage, the initialconcentration of nitric acid et al. on separation process were investigated. Theresearch results show that nitric acid can be removed effectively at low-voltage.Experimental study about the separation of acetaldehyde with the method ofgas-stripping was researched. A non-equilibrium model for describing the GS process was proposed and solved with a Newton-Homotopy method. This model is verifiedby the comparison of simulation results with experimental results. The steady-stateperformance of GS process, such as the influence of liquid-gas ratio, feedingtempearure and theoretical plate was investigated systematically using the model. Theresearch results show that the acetaldehyde in the solution can be removed effectivelywith the application of GS technique. Furthermore, the separation temperature can belowered to the level of avoiding the metachromatism of the glyoxal solution athigh-temperature.Acetic acid separation using EDI technique was studied experimentally. Theexperiments were conducted in electrodialysis equipment packed with membraneJ-1-18and macroporous ion-exchange resin. The mass transfer equation wasestablished and the mass transfer model was obtained. The effects of differentoperation conditions on acetic acid separation were investigated. The research resultsshow that the deep deacidification of glyoxal solution can be obtained.