Trimethylolpropane → 2-Ethyl-2-(hydroxymethyl)propane-1,3-diol;2-methylprop-2-enoic acid

Participants

Reaction Conditions

Reaction Steps

775 kg of trimethylolpropane, 1018 kg of methyl methacrylate (MMA) and also 1433 kg of recycled MMA from Comparative Example 1, 0.123 kg of hydroquinone monomethyl ether as inhibitor and a mixture of 10 kg of calcium oxide and 2.5 kg of lithium chloride as catalyst are combined in a 6 m3 stirred tank reactor provided with agitator, steam heating, distillation column and condenser and the mixture is stirred while passing in air. To stabilize the column, a total of 151 kg of MMA containing 0.12 kg of hydroquinone monomethyl ether and 0.016 kg of 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl in dissolved form are introduced into the column runback during the course of the reaction. The apparatus is heated to a temperature at the bottom of 100° C., with the column initially being operated under total reflux. As soon as the temperature at the top of the column drops below 70° C., the methanol/MMA mixture is taken off at a reflux ratio of 4:1. The MMA stock in the reactor is supplemented by introduction of equal parts of fresh MMA per part of methanol/MMA mixture taken off. A total of 1414 kg of MMA are in this way introduced over a period of 5 hours. Over a period of 8 hours, the reflux ratio is adapted to the decreasing formation of methanol to 27:1. A total of 1410 kg of methanol/MMA mixture are discharged. Above a temperature at the top of the column of 85° C., the methanol/MMA mixture is low in methanol and is collected in a separate vessel for reuse as raw material in the next batch. At a temperature at the bottom of 115° C., the reaction is complete and excess MMA is taken off under reduced pressure, with the pressure gradually being reduced to 100 mbar. When no more MMA distills off, the vacuum is broken. The contents of the tank, which comprise the catalyst-containing trimethylpropane trimethacrylate, are admixed with 18 kg of bleaching earth and 12 kg of aluminium silicate (Perlite) as filter aid and freed of the catalyst by washcoat filtration. The filtrate is fed into a continuous evaporator (area: 3.5 m2) having a rotating wiper system at a pressure of 18 torr and an evaporator temperature of 134° C. A total of 1830 kg of trimethylolpropane trimethacrylate are obtained from the bottom product.

Provenance & Evidence