Methacrolein is prepared in a continuous process by a Mannich condensation reaction of formaldehyde with propanal. A methacrolein polymerization inhibitor is introduced during the production process and a part thereof is recycled back into the reactor where the Mannich condensation reaction is carried out.

Methacrolein is prepared in a continuous process by a Mannich condensation reaction of formaldehyde with propanal. A methacrolein polymerization inhibitor is introduced during the production process and a part thereof is recycled back into the reactor where the Mannich condensation reaction is carried out.

Methacrolein is prepared in a continuous process by a Mannich condensation reaction of formaldehyde with propanal. A methacrolein polymerization inhibitor is introduced during the production process and a part thereof is recycled back into the reactor where the Mannich condensation reaction is carried out.

The invention relates to a process for preparing an α-methylene ketone comprising the step of reacting a ketone with formaldehyde in the presence of a catalyst which is an organic compound comprising at least one acid function or the corresponding salt, ester or amide thereof and at least one amine function or the corresponding ammonium salt, or a zwitterion thereof.

The invention relates to a process for preparing an α-methylene ketone comprising the step of reacting a ketone with formaldehyde in the presence of a catalyst which is an organic compound comprising at least one acid function or the corresponding salt, ester or amide thereof and at least one amine function or the corresponding ammonium salt, or a zwitterion thereof.

The invention relates to a process for preparing an α-methylene ketone comprising the step of reacting a ketone with formaldehyde in the presence of a catalyst which is an organic compound comprising at least one acid function or the corresponding salt, ester or amide thereof and at least one amine function or the corresponding ammonium salt, or a zwitterion thereof.

A process can be used for producing optical molding materials on the basis of methyl methacrylate (MMA). The MMA produced by an optimized method and the molding materials feature in particular a very low yellowness index. This MMA has been produced by direct oxidative esterification of methacrolein. An optimized workup of the reactor output from the oxidative esterification of methacrolein can be used for removing particularly discoloring byproducts. This process moreover has the advantage that fewer demands are placed on plant apparatus configuration.

A process can be used for producing optical molding materials on the basis of methyl methacrylate (MMA). The MMA produced by an optimized method and the molding materials feature in particular a very low yellowness index. This MMA has been produced by direct oxidative esterification of methacrolein. An optimized workup of the reactor output from the oxidative esterification of methacrolein can be used for removing particularly discoloring byproducts. This process moreover has the advantage that fewer demands are placed on plant apparatus configuration.

A process can be used for producing optical molding materials on the basis of methyl methacrylate (MMA). The MMA produced by an optimized method and the molding materials feature in particular a very low yellowness index. This MMA has been produced by direct oxidative esterification of methacrolein. An optimized workup of the reactor output from the oxidative esterification of methacrolein can be used for removing particularly discoloring byproducts. This process moreover has the advantage that fewer demands are placed on plant apparatus configuration.

A process and a preparation plant can prepare methacrolein from formaldehyde and propionaldehyde in the presence of a homogeneous catalyst mixture based at least on an acid and a base. For a good workup of the reaction mixture leaving the reactor, with a good energy balance and where the process has simplified apparatus implementation, the liquid reaction mixture under pressure is expanded in an expansion vessel and separated into a first expansion mixture in a gas phase and a second expansion mixture in a liquid phase. The first expansion mixture is condensed in a first condenser and the second expansion mixture is introduced into a first distillation column and separated therein, into a first distillation mixture in a gas phase at the top and a second distillation mixture in a liquid phase at the bottom. The first distillation mixture is condensed in the first condenser.