The present invention relates to the oxidative combustion of amine-containing wastewaters, especially in a process for preparing methacrolein. Methacrolein is used in chemical synthesis particularly as an intermediate for preparation of methacrylic acid, methyl methacrylate, or else of active ingredients, odorants or flavorings. More particularly, the present invention relates to an oxidative combustion of the amine-containing wastewaters with only low nitrogen oxide formation.

Provided is a process for preparing dry methacrolein which maximizes capture of methanol. Also provided is a process for producing methyl methacrylate.

Provided is a process for preparing dry methacrolein which maximizes capture of methanol. Also provided is a process for producing methyl methacrylate.

Provided is a process for preparing dry methacrolein which maximizes capture of methanol. Also provided is a process for producing methyl methacrylate.

A novel process can be used for purifying methyl methacrylate (MMA) contaminated with low-boiling components by distillation, where the process involves producing MMA by oxidative esterification, and a crude product containing methyl propionate (MP), methyl isobutyrate (MIB), and methacrolein (MAL) as low-boiling components. The process is compatible with MMA produced from C.sub.2-based methacrolein containing the low-boiling components specified.

A novel process can be used for purifying methyl methacrylate (MMA) contaminated with low-boiling components by distillation, where the process involves producing MMA by oxidative esterification, and a crude product containing methyl propionate (MP), methyl isobutyrate (MIB), and methacrolein (MAL) as low-boiling components. The process is compatible with MMA produced from C.sub.2-based methacrolein containing the low-boiling components specified.

A novel process can be used for purifying methyl methacrylate (MMA) contaminated with low-boiling components by distillation, where the process involves producing MMA by oxidative esterification, and a crude product containing methyl propionate (MP), methyl isobutyrate (MIB), and methacrolein (MAL) as low-boiling components. The process is compatible with MMA produced from C.sub.2-based methacrolein containing the low-boiling components specified.

A process for preparing an aldol ester of the formula (I), wherein at least one carboxylic anhydride of the formula (II) is reacted with at least one aldol of the formula (III) with heating in the presence of a basic catalyst with a pKa of the conjugate acid of at least 8, and the reaction product obtained from the process. The process provides a light-coloured and low-odour reaction product which has a high content of aldol ester content of the formula (I) and can be used, without elaborate purification steps, particularly without overhead distillation of the aldol ester, as a blocking agent for primary amines. The resultant blocked amines have a long storage life together with polymers containing isocyanate groups, and cure rapidly and reliably on contact with moisture to form mechanically high-grade and robust elastomers.

A process for preparing an aldol ester of the formula (I), wherein at least one carboxylic anhydride of the formula (II) is reacted with at least one aldol of the formula (III) with heating in the presence of a basic catalyst with a pKa of the conjugate acid of at least 8, and the reaction product obtained from the process. The process provides a light-coloured and low-odour reaction product which has a high content of aldol ester content of the formula (I) and can be used, without elaborate purification steps, particularly without overhead distillation of the aldol ester, as a blocking agent for primary amines. The resultant blocked amines have a long storage life together with polymers containing isocyanate groups, and cure rapidly and reliably on contact with moisture to form mechanically high-grade and robust elastomers.

A process for preparing an aldol ester of the formula (I), wherein at least one carboxylic anhydride of the formula (II) is reacted with at least one aldol of the formula (III) with heating in the presence of a basic catalyst with a pKa of the conjugate acid of at least 8, and the reaction product obtained from the process. The process provides a light-coloured and low-odour reaction product which has a high content of aldol ester content of the formula (I) and can be used, without elaborate purification steps, particularly without overhead distillation of the aldol ester, as a blocking agent for primary amines. The resultant blocked amines have a long storage life together with polymers containing isocyanate groups, and cure rapidly and reliably on contact with moisture to form mechanically high-grade and robust elastomers.