Rapid and continuous synthesis of methacrolein with high selectivity by condensation of propanal with formaldehyde in laboratory

Abstract

AbstractAn experimental device with a micro‐tubular reactor for continuous reaction process was designed and constructed based on the reaction mechanisms and characteristics of condensation of propanal with formaldehyde, a short mean residence time (a few seconds) for the reactive mixture was acquired to increase selectivity to methacrolein (MAL) by reducing the side reactions. Diethylamine and acetic acid aqueous solution was used as catalysts for the reaction. The reactor temperature ranged between 100 and 210 °C. The reactor pressure was set at 4.5–6.0 MPa to make sure that the reaction can be carried out in liquid phase. The results indicated that the reaction rate was heavily influenced by the concentration of the catalysts and the feed preheating temperature. When the feed preheating temperature was about 132 °C, the mass concentration of diethylamine was about 6 %, the reaction pressure was 4.5–5.0 MPa, and the mean residence time varied from 4.5 to 5.5 s, high conversion of propanal (99.9 %) and high selectivity to MAL (98.7 %) were acquired. High catalytic activity and high selectivity were maintained after the catalysts had been recycled six times.