초록

A process for transferring heat to a liquid mixture comprising at least one (meth)acrylic monomer in an indirect heat exchanger, wherein a quaternary ammonium salt, a tertiary amine or a salt thereof with a Brønsted acid is added to the liquid mixture to reduce fouling.

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The invention claimed is: 1. A process for transferring heat to a fluid mixture comprising at least one (meth)acrylic monomer with the aid of an indirect heat exchanger which is flowed through on its primary side by a fluid heat carrier and on its secondary side simultaneously by the fluid mixture

The invention claimed is: 1. A process for transferring heat to a fluid mixture comprising at least one (meth)acrylic monomer with the aid of an indirect heat exchanger which is flowed through on its primary side by a fluid heat carrier and on its secondary side simultaneously by the fluid mixture comprising at least one (meth)acrylic monomer, wherein the fluid mixture comprising at least one (meth)acrylic monomer comprises at least one added active compound other than (meth)acrylic monomers from the group consisting of tertiary amines, the salts formed from a tertiary amine and a Brønsted acid, and quaternary ammonium compounds, with the proviso that none of the tertiary and quaternary nitrogen atoms in the at least one active compound bears a phenyl group but at least one of the tertiary and quaternary nitrogen atoms in the at least one active compound bears at least one alkyl group. 2. The process according to claim 1, wherein the at least one (meth)acrylic monomer is acrylic acid and/or methacrylic acid. 3. The process according to claim 1, wherein the at least one (meth)acrylic monomer is at least one monomer from the group consisting of hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, glycidyl acrylate, glycidyl methacrylate, methyl acrylate, methyl methacrylate, n-butyl acrylate, isobutyl acrylate, isobutyl methacrylate, n-butyl methacrylate, tert-butyl acrylate, tert-butyl methacrylate, ethyl acrylate, ethyl methacrylate, 2-ethylhexyl acrylate and 2-ethylhexyl methacrylate. 4. The process according to any of claims 1 to 3, wherein the at least one active compound is a tertiary amine of the general formula where R1*, R2* and R3* are each independently an alkyl group which has from 1 to 8 carbon atoms, or an alkyl group which has from 1 to 8 carbon atoms and in which one or more hydrogen atoms are replaced by at least one of the groups —OH, —NH2, —NHCH3 and —N(CH3)2 and/or the carbon chain is interrupted at least once by an oxygen atom, or a cycloalkyl group which has from 1 to 8 carbon atoms and in which one or more hydrogen atoms are replaced by at least one of the groups —OH, —NH2, —NHCH3 and —N(CH3)2 and/or the cyclic carbon chain is interrupted at least once by an oxygen atom, or is the salt of such a tertiary amine and a Brønsted acid. 5. The process according to any of claims 1 to 3, wherein the at least one active compound is a derivative of 1,3-diazole which derives therefrom in that the hydrogen on the nitrogen in the 1-position has been replaced by an alkyl group R4 having from 1 to 8 carbon atoms and/or the nitrogen of the 1,3-diazole in the 3-position has been alkylated with an alkyl group R5 having from 1 to 8 carbon atoms. 6. The process according to any of claims 1 to 3, wherein the at least one active compound is the salt of a quaternary ammonium ion, where the quaternary ammonium ion is one of the general formula where R1*, R2* and R3* are each independently, and independently of R6, an alkyl group which has from 1 to 8 carbon atoms, or an alkyl group which has from 1 to 8 carbon atoms and in which one or more hydrogen atoms are replaced by at least one of the groups —OH, —NH2, —NHCH3 and —N(CH3)2 and/or the carbon chain is interrupted at least once by an oxygen atom, or a cycloalkyl group which has from 1 to 8 carbon atoms, or a cycloalkyl group which has from 1 to 8 carbon atoms and in which one or more hydrogen atoms are replaced by at least one of the groups —OH, —NH2, —NHCH3 and —N(CH3)2 and/or the cyclic carbon chain is interrupted at least once by an oxygen atom, and R6, independently of R1*, R2* and R3*, is an alkyl group having from 1 to 8 carbon atoms. 7. The process according to claim 1, wherein the molar mass of the at least one active compound is ≦600 g. 8. The process according to claim 1, wherein the fluid mixture comprises an addition of from 0.01 to 10% by weight of its weight of the at least one active compound. 9. The process according to claim 1, wherein the fluid mixture comprises ≧0.5% by weight of its weight of the at least one (meth)acrylic monomer. 10. The process according to claim 1, wherein the temperature with which the fluid mixture leaves the indirect heat exchanger is from 50 to 350° C. 11. The process according to claim 1, wherein the indirect heat exchanger is a tube bundle heat transferer. 12. The process according to claim 1, wherein the fluid heat carrier is steam. 13. The process according to claim 1, wherein the fluid mixture has been withdrawn from the bottom of a separating column comprising separating internals, into which, in a thermal separating process, at least one stream comprising at least one (meth)acrylic monomer is fed and at least one stream which differs therefrom and comprises at least one (meth)acrylic monomer is withdrawn. 14. The process according to claim 13, wherein the fluid mixture, after leaving the indirect heat exchanger, is recycled into the separating column. 15. The process according to claim 13 or 14, wherein the at least one stream fed in is the acrylic acid-comprising bottom product of a fractional condensation of the product gas mixture of a heterogeneously catalyzed gas phase partial oxidation of a C3 precursor compound to acrylic acid in a condensation column, and the thermal separating process is the stripping of the acrylic acid from this bottom product.