Experimental Research And Process Development For The Synthesis Of Methacrolein By Condensation Of Propanal With Formaldehyde

Methacrolein(MAL)is an important chemical intermediate,which is mainly used in the production of methyl methacrylate(MMA).At present,MAL was mainly produced by oxidation of isobutene which mainly comes from petroleum.Study on the production of MAL by condensation of propanal with formaldehyde can lay a foundation for producing MMA with coal as raw material(propanal was produced by hydroformylation of ethylene;ethylene,synthetic gas,formaldehyde and methanol can be produced from coal),by which the production cost of MMA can be significantly reduced.In this work,the experimental device for batch condensation of propanal with formaldehyde was built,the reaction behavior of condensation of propanal with formaldehyde was preliminary invesgated through a series of batch condensation reactions,and a relatively superior reactive condition was acquired.On the basis of batch condensation results,an experimental device with a micro tubular reactor for continuous condensation process was designed and constructed based on the reaction mechanisms and characteristics of condensation of propanal with formaldehyde,and a short mean residence time was acquired.Both high conversion of propanal and high selectivity to MAL were acquired by reducing the side reactions through optimizing the feed preheating temperature and the concentration of catalysts.The condensation reaction was carried out in a micro tubular adiabatic reactor,always occurred in liquid phase.Diethylamine and acetic acid aqueous solution was used as catalysts for the reaction.The results of continuous condensation indicated that the reaction rate and selectivity were heavily influenced by the concentration of the catalysts and the feed preheating temperature.When the feed preheating temperature was about 132?,the mass concentration of diethylamine was about 6%,the reaction pressure was 4.5~5.0MPa,and the mean residence time varied from 4.5s to 5.5s,high conversion of propanal(99.9%)and high selectivity to methacrolein(98.7%)were acquired.High catalytic activity was maintained after the catalysts had been recycled for six times,the conversion of propanal and the selectivity to MAL were at least 98.3% and 93.7%,respectively.The production process of producing methacrolein by condensation of propanal with formaldehyde was developed based on the experimental research data,and the process simulation was finished with the use of chemical process simulation software(Aspen Plus).The works provide basic data for the development and design of the industrial production plant of producing MAL by condensation of propanal with formaldehyde.