Study On Polymerization Reasons Of Acetaldehyde And Countermeasures Of Preventing Polymerization

This paper is the major part of YANGZI PETROCHEMICAL COMPANYLIMITED development project — — Study on Polymerization Reasons ofAcetaldehyde and Countermeasures of Preventing Polymerization. The purpose is tofind why pressure and temperature of the tank raised while acetaldehyde was filled tosale, and raise the method of solution. Study determined the system analytical method of the experiment, used thegaseous phase chromatogram to analyse, the chromatographic column is capillarywhich is 30 meters long, SE-30 stationary liquid smeared inside; Chromatogramoperational conditions had been determined: vaporization temperature 160 ℃ ,detection temperature 160℃, column temperature 110℃, the pressure of carrier gas0.06MPa, air pressure 0.10MPa, hydrogen pressure 0.06MPa. Using areanormalization method, correction factor relatively of acetaldehyde and paraldehyde indifferent contents of acetaldehyde and paraldehyde was measured as 1.17. According to low boiling point of acetaldehyde and heat liberation characteristicof acetaldehyde polyreaction, the stainless steel micro-reactor with special structurehad been designed, it is able to resistance pressure, and it is easy to controltemperature, while it is convenient to sampling, to stop reaction and to cool, and soon. Above all, experiments observed and determined that pure acetaldehyde couldnot polymerize from -5℃ to 80℃. According to the impurities that may be broughtinto acetaldehyde in production, store and transportation, the influence of about 40kinds of chemicals on polymerization of acetaldehyde had been studied in detail. Theresults show that, hydrochloric acid, sulfuric acid, methane acid, oxalic acid,palladium chloride, ironic chloride, hydrogen chloride and chlorine have remarkablecatalysis to polymerization of acetaldehyde. According to the fact of acetaldehyde instore and transportation, study determined experiment conditions: reactiontemperature 30℃, sampling time 1 hour. Study observed detailedly catalysis law ofcatalysts to polymerization of acetaldehyde at different quantities, the minimum mass i南京工业大学硕士论文fraction that the chemicals cause the acetaldehyde to polymerize had been confirmed,the minimum mass fraction of hydrochloric acid, sulfuric acid, methane acid, oxalicacid, palladium chloride, ironic chloride is 1.0×10-5, 1.0×10-5, 0.02, 0.05, 1.0×10-5 and1.30×10-4; The minimum volume ratio (v/v) of hydrogen chloride and chlorine is0.0250 and 0.0100. Through exploration, four kinds of chemicals have been found, they can restrainacetaldehyde efficiently to polymerize, they are ammonium acetate, tri-ammoniumcitrate, hexamethylene tetramine and triethy lamine. The inhibition laws of fourchemicals to polymerization of acetaldehyde have been studied in detail, results showthat, all the four kinds of organic amines can prevent above-mentioned catalysts toacetaldehyde, and the effect of triethy lamine is best. On the basis of above-mentioned researches, equilibrium concentrations ofparaldehyde were determined when acetaldehyde polymerized and reachedequilibrium at different temperatures, and relational expression of reactionequilibrium constant and temperature was established, reaction heat that acetaldehydepolymerizes to paraldehyde was calculated as -78.663 kJ/mol, which is consistentbasically with document value and value that estimated through thermodynamics. Thedifferent concentration solution saturated steam pressures of acetaldehyde andparaldehyde had been measured, and according to the intermittence model reactor,research analog calculated maximum temperature and pressure when acetaldehydepolymerizes in the tank. The analog results show that, the maximum temperature is76℃, the maximum pressure is 0.477MPa (absolute pressure), the initial temperatureof material affects mostly on systematic temperature, pressure and conversion rate ofa...