Patent DE-102009027401-A1 (DE)
Title: Separating acrylic acid comprises cooling product gas mixture of partial gas phase oxidation of three carbon precursor compound in cooler and providing cooled product gas mixture with (non)evaporated cooling liquid into absorption column
Inventor: BLUM TILL
IPC: C07C57/07
Filed: 2009-07-01
Abstract: Separating acrylic acid from the product gas mixture of a heterogeneously catalyzed partial gas phase oxidation of at least one 3C-precursor compound to acrylic acid comprises: (a) cooling the product gas mixture in a direct cooler by directly cooling with a finely sprayed cooling liquid, where a portion of the cooling liquid is evaporated and (b) providing the cooled product gas mixture together with evaporated and non-evaporated cooling liquid into an absorption column of a sump region. Method for separating acrylic acid from the product gas mixture of a heterogeneously catalyzed partial gas phase oxidation of at least a 3C-precursor compound to acrylic acid, where the mixture, in addition to acrylic acid, comprises water vapor, glyoxal, low boiling, average boiling, high boiling and highly condensable compounds that are different from the above, as by-products, comprises: (a) cooling the product gas mixture in a direct cooler by directly cooling with a finely sprayed cooling liquid, where a portion of the cooling liquid is evaporated; (b) providing the cooled product gas mixture together with evaporated and non-evaporated cooling liquid into an absorption column of a sump region, where between the absorption room of the absorption column a chimney plate having at least one chimney, is present and connected; (c) providing the cooled product gas mixture and evaporated cooling liquid into the soil absorption column through the chimney of the chimney plate, which forms descending high-boiling absorption medium, where the chimney plate contains a absorbate, which absorbs acrylic acid; (d) removing the acrylic acid from the absorbate; (e) contacting one portion of absorbate filled in the absorption column to the sump room of the absorption column for forming a sump fluid in the sump region, optionally cooling another portion of the absorbate and recycling the chimney plate into the absorption column; (f) contacting the residual quantity in the absorbate or the absorbate in a rectification column with reinforcing and stripping section; (g) enriching the stripping section of the rectification column with the absorbate and feeding out the stripping section of absorption agent with an acrylic acid weight portion of >= 1 wt.%; (h) enriching the rectification section of the rectification column with acrylic acid and feeding out the reinforcing section of a raw acrylic acid, where the weight portion of the acrylic acid is = 90 wt.%; (i) extracting the obtained sump liquid from the sump region of the absorption column, feeding one portion of the obtained sump liquid, as cooling liquid, into the direct cooler and feeding the remaining portion of the liquid into the bottom of a distillation unit comprising a distillation column and a circulating heat exchangers; (j) separating the sump liquid in the distillation column of the distillation unit in exhaust vapors, whose weight portion in the absorption agent is greater than the weight portion of the sump fluid at absorption agent, and into liquid concentrate, whose weight portion is high, when the absorption agent of the boiling components is greater than the high boiling components of the sump liquid; (k) recycling water vapor, possibly its cooling and/or condensation in an indirect heat exchanger and above the chimney plate in the absorption column; (l) leading out a mass flow from the bottom of the distillation column in the standing height of the liquid concentrate with the temperature T 1>from the distillation column; (m) discharging a partial stream of the mass flow from the procedure of the separation of acrylic acid from the product gas mixture; and (n) recycling the residual stream of the mass flow over the circulation heat exchanger with a temperature (T 2>>= T 1>) of absorbed mass flow from the distillation column, into the distillation column; where the average retention time of the components of the partial stream in the distillation unit is = 40 hours.