Method for removing acrolein from the process gas of a heterogeneously catalysed oxidation of propene
First Claim
1. Continuous process for preparing acrolein, wherein the following are carried outA) gas-phase oxidation of propene by air over a heterogeneous catalyst in the presence of a diluent gas in one reaction stageB) capture of the acrolein-containing gas stream A) in a quenching stage consisting of bottom, middle and top sections for separating off by-products in the presence of water and an organic phase containing sparingly water-soluble organic solventC) capture of the acrolein-containing gas stream from the quenching stage B) in an absorption stage consisting of bottom, middle and top sections in the presence of water and an organic phase containing sparingly water-soluble organic solvent to obtain an aqueous acrolein solution which contains organic phase, and an incondensable gas streamC1) at least partial recirculation of the incondensable gas stream from C) as diluent gas to the reaction stage A)D) separation of the acrolein by distillation from the aqueous acrolein solution which contains organic phase from C) in a distillation stagewhere the remaining aqueous solution which contains organic phase and has been freed of acrolein is discharged from the distillation stage D) so as to form an organic phase II which is separated from the associated aqueous fraction II (phase separation II), the organic phase II is introduced into the bottom section of the quenching stage B) from which the organic phase II is separated off together with an aqueous fraction via the top section by distillation and/or stripping so as to form an organic phase I which is separated from the associated aqueous fraction I (phase separation I) and introduced into the bottom section of the absorption stage C).
2 Assignments
0 Petitions
Accused Products
Abstract
The invention relates to a process for separating acrolein from the process gas of a heterogeneously catalyzed oxidation of propene by means of atmospheric oxygen, wherein high boilers (including acrylic acid) are firstly separated off from the process gas by means of quenching and technical-grade acrolein having small proportions of low boilers is then obtained by means of absorption and subsequent distillation. Small amounts of a solvent by means of which, in particular, oligomers formed are separated off and the tendency for foam to be formed in the apparatuses or columns is reduced is added in the columns and heat exchangers in the work-up process. The solvent is, according to the invention, separated off and recycled in the form of an organic phase in-situ within the existing process.
8 Citations
23 Claims
-
1. Continuous process for preparing acrolein, wherein the following are carried out
A) gas-phase oxidation of propene by air over a heterogeneous catalyst in the presence of a diluent gas in one reaction stage B) capture of the acrolein-containing gas stream A) in a quenching stage consisting of bottom, middle and top sections for separating off by-products in the presence of water and an organic phase containing sparingly water-soluble organic solvent C) capture of the acrolein-containing gas stream from the quenching stage B) in an absorption stage consisting of bottom, middle and top sections in the presence of water and an organic phase containing sparingly water-soluble organic solvent to obtain an aqueous acrolein solution which contains organic phase, and an incondensable gas stream C1) at least partial recirculation of the incondensable gas stream from C) as diluent gas to the reaction stage A) D) separation of the acrolein by distillation from the aqueous acrolein solution which contains organic phase from C) in a distillation stage where the remaining aqueous solution which contains organic phase and has been freed of acrolein is discharged from the distillation stage D) so as to form an organic phase II which is separated from the associated aqueous fraction II (phase separation II), the organic phase II is introduced into the bottom section of the quenching stage B) from which the organic phase II is separated off together with an aqueous fraction via the top section by distillation and/or stripping so as to form an organic phase I which is separated from the associated aqueous fraction I (phase separation I) and introduced into the bottom section of the absorption stage C).
Specification