| Propionic acid, as an essential organic chemical material, is widely used in many fields. In this paper, the kinds of properties and the production developing status of propionic acid are expanded; the three synthetic methods of propionic acid are introduced; among which the oxidation process of propionaldehyde to propionic acid is perfect and it has mostly used to produce propionic acid in the world. The output of propionic acid by this process accounts for 90% of the total in America now. Moreover the oxidation reaction mechanism of propionaldehyde is studied, which confirm that oxidation reaction is first-order reaction with respect to lower concentration of propionaldehyde; the reaction forming side product-acetic acid is parallel to main reaction. The effect of catalyst, reaction condition and two-stage reaction on conversion and selectivity in continuous oxidation process is explored. The results indicate the oxidation reaction for forming propionic acid is fast. The catalyses of the various third period transition metal carboxylates are similar each other, but the use of catalyst can reduce the oxidation selectivity. The gas-liquid oxidation process without catalyst is simple and can be operated smoothly. The research on continuous reaction shows the over 95% conversion and the over 98% selectivity are reached at 60~65, 0. 3~0. 5Mpa and excess 10% oxygen for one-stage reactor. And for two-stage reactor , in the second reactor temperature may improve 10~15, n(oxygen) :n(propionaldehyde) should be in 0. 7~0. 9 , then the total conversion is over 99% and the selectivity is over 97% .The safety of discharge of waste gas and decomposition of peroxide is also examined. The lowest concentration of nitrogen in waste gas is 85% and the maximum permissible concentration of oxygen is 9. 5%. The product is separated by a packed distillation column with triangle spire packings, which possesses 19 equilibrium-stages per meter. The acetic acid and volatile components are extracted from the top of column and the content of propionic acid is over 99.5% at bottom. For making the color of product lighten, the qualified product could be obtained by condensing effluent stream from the reboiler of column. The separation process of two columns is also tested for promoting product purity; theequilibrium-stage of the second column is 5. The simulation calculation by means of ASPEN PLUS shows the number af the equilibrium-stage of column (abbr. N) is 20. The calculation results measure up to ones of the test. The analysis shows the properties of final product as follows: purity of propionic acid 99. 5%, non-volatile residue<0. 01%, aldehyde (based on propionaldehyde) 0.05%, heavy metal (based on Pb) 0.00005%,color and lustre (Pt-Co) 15, content of water<1000PPM.On basis of techno-economic analysis, the interior yield of lOkt/a propionic acid production plant founded on the technology developed from this study will be 17% by taxation, thus the better profits can be gained.
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