Method for preparing isocyanates
AssigneeCovestro Deutschland AG
InventorsSarmilan Santhakumaran, Lukas Grave, Pascal Scherpian, Manfred Kobylka, Tevfik Topal Hasan, Mark Jacob, Christian Jens, Michael Merkel, Franz-Josef Niemeyer, Christian Toffel
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Abstract
The invention relates to a method for preparing isocyanates by reacting corresponding amines with phosgene. The invention further relates to an apparatus for separating exhaust gas flows from a phosgenation reaction.
Claims18
The process of claim 1, wherein the target value for the second phosgene content is in the range from 20% by weight to 70% by weight.
The process of claim 1, wherein, in normal operation, the second phosgene content is controlled by adjusting the mass flow M1 to the predefined target value and, if the threshold value for the first phosgene content is exceeded, there is a deviation from normal operation, and the mass flow M1 is increased.
The process of claim 1, wherein the at least one amine is a diamine.
The process of claim 1, wherein the reaction of the at least one amine or salt thereof with phosgene is carried out in the presence of a solvent.
The process of claim 1, wherein the reaction of the at least one amine or salt thereof with phosgene is carried out in the condensed phase.
The process of claim 1, wherein the reaction of the at least one amine or salt thereof with phosgene is carried out in a batchwise manner.
The process of claim 1, wherein the reaction in step A) is a base phosgenation of at least one amine with phosgene.
The process claim 1, wherein chlorobenzene, o-dichlorobenzene or mixtures of these two solvents is used as the absorbent step B).
The process of claim 1, wherein the absorption device comprises a gas scrubber selected from the group consisting of packed columns with a random packing, packed columns with a structured packing, and tray columns, preferably consisting of packed columns with a random packing and packed columns with a structured packing.
A device for separating offgas streams from a phosgenation reaction, comprising
- at least one absorption device for contacting a first process offgas stream comprising hydrogen chloride and phosgene with an absorbent M1, producing a phosgene-depleted second offgas stream having a first phosgene content and a first phosgene solution having a second phosgene content,
- an apparatus, associated with the absorption device, for determining the first phosgene content in the second offgas stream or an apparatus, associated with the absorption device, for determining the second phosgene content of the first phosgene solution,
- an apparatus for altering the absorbent mass flow M1 with which the absorbent is introduced into the absorption device,
- and a computer for closed-loop control of the separation, wherein the computer is set up for the control of the process of claim 1.
The process of claim 2, wherein the target value for the first phosgene content is in the range from 0.01% by volume to 1.00% by volume.
The process of claim 2, wherein the target value for the first phosgene content is in the range from 0.02% by volume to 0.2% by volume.
Dependencies are inferred from the claim text.