Patent DE-102010001228-A1 (DE)
Title: Separating acrylic acid from a product gas mixture of heterogeneously catalyzed partial gas phase oxidation of a precursor compound to acrylic acid comprises cooling product gas mixture and adding cooled mixture into absorption column
Inventor: BLUM TILL
IPC: C07C57/07
Filed: 2010-01-26
Abstract: Separating acrylic acid from a product gas mixture of heterogeneously catalyzed partial gas phase oxidation of at least 3C-precursor compound to acrylic acid comprises cooling the product gas mixture, adding the cooled product gas mixture with evaporated and unevaporated cooling liquid into an absorption column, flowing the cooled product gas mixture and evaporated cooling liquid through absorption area, adding a partial quantity of the absorbate A to the absorption column under the formation of a bottom liquid and optionally cooling the partial quantity of the absorbate A. Separating acrylic acid from a product gas mixture of heterogeneously catalyzed partial gas phase oxidation of at least 3C-precursor compound to acrylic acid, where the product gas mixture comprises, in addition to acrylic acid, water vapor, glyoxal, and low boiling-, medium boiling-, high boiling and heavily condensable components, as minor components, comprises: cooling the product gas mixture in a direct cooler by directly cooling with finely atomized cooling liquid, where the partial quantity of the cooling liquid is evaporated; adding the cooled product gas mixture with evaporated and unevaporated cooling liquid into a bottom chamber of an absorption column on which separation-active internals are arranged, where the absorption areas of the absorption column are bounded by a chimney tray having a chimney located between the two areas; flowing the cooled product gas mixture and evaporated cooling liquid through the absorption area by the chimney of chimney tray, where a high-boiling absorbent is flowed in a counter current manner, and the absorbent containing absorbate A, in which the acrylic acid absorbed, is flowed on the chimney tray; adding a partial quantity of the absorbate A from the absorption column to the bottom chamber of the absorption column under the formation of a bottom liquid in the bottom chamber, and optionally cooling the partial quantity of the absorbate A and recycling to the chimney tray; stripping the low-boiling components from the balance quantity of the absorbate A from the absorption column optionally in a stripping unit and producing low-boiling components depleted absorbate A1; supplying the balance quantity of absorbate A or absorbate A1 to a rectification column with rectifying and stripping section; enriching the absorbent in the stripping section of the rectification column and leading out the absorbent with an acrylic acid content of = 1 wt.% from the stripping section of the absorption column; enriching the acrylic acid in the rectifying section of the rectification column and leading out a crude acrylic acid with an acrylic acid content >= 90 wt.% from the rectifying section; extracting the bottom liquid containing absorbent from the bottom chamber of the absorption column; adding a partial quantity of extracted the bottom liquid as cooling liquid to the direct cooler, and supplying the balance quantity of the extracted bottom liquid to a distillation unit comprising a distillation column and a circulation heat exchangers; separating the bottom liquid into vapor by the distillation unit, where the weight of absorbent is greater than the weight of the bottom liquid of the absorbent; recycling a stream of the vapor to the chimney tray, optionally after indirect heat exchanger cooling and/or condensation of it; flowing a liquid concentrate with a mass flow M and a standing height S at the lower end of the distillation column at a temperature T1; discharging a partial quantity of the mass flow M from the separation process of acrylic acid from the product gas mixture; and recycling the balance quantity of mass flow M by the circulation heat exchanger with a temperature T2>= T1 into the distillation column, where the average retention time (tv) of the components of the partial quantity of mass flow M in the distillation unit is = 40 hours.