초록

Crude acrylic acid is purified batchwise by crystallization by a process which comprises at least one purification stage and at least one stripping stage and in which at least the first stripping stage is carried out in a different crystallizer from the first purification stage.

대표청구항 ▼

We claim: 1. A process for the batchwise purification of crude acrylic acid by crystallization, consisting essentially of: at least one purification stage comprising a tubular falling film crystallizer A in which an amount of crude acrylic acid is subjected to crystallization and at least one strip

We claim: 1. A process for the batchwise purification of crude acrylic acid by crystallization, consisting essentially of: at least one purification stage comprising a tubular falling film crystallizer A in which an amount of crude acrylic acid is subjected to crystallization and at least one stripping stage comprising a tubular falling film crystallizer B in which an amount of mother liquor produced in the at least one crystallizer A is subjected to crystallization, said crystallizer A being different from said crystallizer B, wherein, in at least the first stripping stage, mother liquor obtained from crystallization of crude acrylic acid in crystallizer A of the first purification stage is crystallized in crystallizer B and wherein each of the crystallizers A and B is comprised of crystallization tubes. 2. The process as claimed in claim 1, wherein the amount of mother liquor to be purified by crystallization in crystallizer B ranges from 10 to 60% by volume of the amount of crude acrylic acid subjected to crystallization in crystallizer A. 3. The process as claimed in claim 1, wherein the amount of said mother liquor obtained from the first purification stage is smaller than the amount of the crude acrylic acid crystallized in tubular falling-film crystallizer A of the first purification stage. 4. The process as claimed in claim 2, wherein the amount of mother liquor to be purified by crystallization in crystallizer B ranges from 20 to 50% by volume of the amount of crude acrylic acid subjected to crystallization in crystallizer A. 5. The process as claimed in claim 3, wherein the amount of said mother liquor to be purified in crystallizer B ranges from 20 to 40% by volume of the amount of crude acrylic acid to be purified in crystallizer A. 6. The process as claimed in claim 3, wherein the amount of acrylic acid that crystallizes in the first purification stage is up to 30% by weight of the quantity of initial crude acrylic acid placed in crystallizer A. 7. A process for the batchwise purification of crude acrylic acid by crystallization in an apparatus consisting of a tubular falling film crystallizer A and a separate and distinct tubular falling film crystallizer B, each of the crystallizers being comprised of crystallization tubes, comprising, in a batchwise manner: i) passing a volume of crude acrylic acid in an at least one first purification stage to said tubular falling film crystallizer A in which crystals of purified acrylic acid and a mother liquor form; and ii) passing substantially all of said mother liquor, which has a volume ranging from 10 to 60% of the volume amount of the crude acrylic acid that enters crystallizer A in step i), in a first stripping stage to said crystallizer B whose size is proportionately reduced relative to the size of crystallizer A to a degree that is commensurate with the 10 to 60% reduced volume of the mother liquor, thereby forming crystals of acrylic acid as a product in crystallizer B.