阅读说明：本技术 在气相中制备异氰酸酯的方法 (Method for producing isocyanates in the gas phase ) 是由 J.策希林 T.施特滕 于 2018-06-06 设计创作，主要内容包括：本发明涉及通过相应伯胺在气相中的光气化而制备异氰酸酯的方法,其中通过与至少一个骤冷液料流接触而将粗制气态反应产物混合物冷却和部分冷凝,并在进一步冷却后使用冷凝的反应产物混合物的一部分作为所述至少一个骤冷液料流的成分,任选唯一成分,其中所用总骤冷液包含基于其总质量计最多25质量%比例的有机溶剂,其中相对于100质量%的余量由至少要制备的异氰酸酯构成,其中在骤冷液的影响下反应产物混合物的未冷凝的部分也在洗涤塔中脱除异氰酸酯组分,其中获得包含洗涤液和异氰酸酯的液体料流,其具有基于其总质量计0.0质量%至10.0质量%,尤其是0.0质量%至5.0质量%的有机溶剂比例。(The invention relates to a method for producing isocyanates by phosgenation of the corresponding primary amines in the gas phase, wherein a crude gaseous reaction product mixture is cooled and partially condensed by contact with at least one quenching liquid stream, and using a portion of the condensed reaction product mixture, after further cooling, as a component, optionally the only component, wherein the total quench liquid used comprises a proportion of organic solvent of at most 25% by mass, based on its total mass, wherein the balance with respect to 100% by mass is constituted by at least the isocyanate to be prepared, wherein the uncondensed part of the reaction product mixture is also freed of isocyanate components in the washing column under the influence of the quench liquid, wherein a liquid stream comprising washing liquor and isocyanate is obtained which has a proportion of organic solvent of from 0.0 to 10.0 mass%, in particular from 0.0 to 5.0 mass%, based on its total mass.)

1. Process for the preparation of isocyanates by phosgenation of the corresponding primary amines in the gas phase, which comprises the steps of:

(i) providing a gaseous stream of a primary amine;

(ii) providing a gaseous phosgene stream;

(iii) (iii) mixing the primary amine gaseous stream from step (i) and the gaseous phosgene stream from step (ii) in a mixing zone following a stoichiometric excess of phosgene based on primary amino groups to produce a gaseous reaction mixture, and conducting the gaseous reaction mixture thus obtained through a reaction zone to react the primary amine with phosgene to obtain a gaseous reaction product mixture;

(iv) (iv) cooling the gaseous reaction product mixture obtained after passing through the reaction zone from step (iii) by contacting in a quench zone with at least one stream of quench liquid, wherein the total quench liquid used comprises a proportion of organic solvent of at most 25% by mass, based on its total mass, with the balance with respect to 100% by mass consisting of at least the isocyanate to be produced, to obtain a mixture of reaction product mixture and quench liquid;

(v) (iv) introducing the mixture of reaction product mixture obtained in step (iv) and quench liquid into a collection zone for phase separation, wherein a liquid phase comprising isocyanate and a gaseous phase comprising hydrogen chloride, unreacted phosgene and unliquefied isocyanate are withdrawn from the collection zone;

(vi) (vi) cooling a portion of the isocyanate-containing liquid phase withdrawn from the collection zone in step (v) and using the thus obtained cooled, but otherwise unchanged composition, liquid phase in step (iv) as a component of the quench liquid, optionally as its sole component;

(vii) (vi) working up the part of the liquid phase comprising isocyanate which has not been cooled in step (vi) and which is removed from the collection zone in step (v) for step (iv), to obtain isocyanate;

(viii-1) optionally, partially condensing the gaseous phase comprising hydrogen chloride, unreacted phosgene and unliquefied isocyanate obtained in step (v) by cooling to obtain a liquid stream comprising isocyanate and a gaseous stream comprising hydrogen chloride, phosgene and unliquefied isocyanate;

(viii-2)

(viii) when step (viii-1) is carried out, the gaseous stream obtained in step (viii-1) comprising hydrogen chloride, phosgene and unliquefied isocyanate, or

(vi) when step (viii-1) is not carried out, the gas phase obtained in step (v) comprising hydrogen chloride, unreacted phosgene and unliquefied isocyanate

(viii) is introduced into a wash column in which the isocyanate is washed out with wash liquor to obtain a liquid stream comprising wash liquor and isocyanate and a gaseous stream comprising hydrogen chloride and phosgene, and the gaseous stream comprising hydrogen chloride and phosgene obtained there is partially condensed in a condenser downstream of the wash column, wherein the total wash liquor used in step (viii-2) consists of the condensate obtained in the condenser downstream of the wash column and optionally additionally supplied wash liquor, wherein the amount of organic solvent introduced into the wash column by means of the additionally supplied wash liquor is at most such that a proportion of organic solvent of from 0.0 to 10% by mass, based on its total mass, is established in the liquid stream comprising wash liquor and isocyanate obtained in the wash column.

2. A process as claimed in claim 1 wherein in step (iv) the gaseous reaction product mixture is contacted with a quench liquid by injecting the quench liquid into the gaseous reaction product mixture.

3. A process as claimed in claim 2 wherein the contacting of the gaseous reaction product mixture with quench liquid in step (iv) is effected in a single stage.

4. A process as claimed in any one of the preceding claims, wherein the total scrubbing liquid used in step (viii-2) consists of the condensate obtained in the condenser downstream of the scrubbing column and an additional supply of scrubbing liquid, wherein this additional supply of scrubbing liquid is a solvent stream comprising only an organic solvent selected from the group consisting of aliphatic hydrocarbons, halogen-free substituted aromatic hydrocarbons, aromatic hydrocarbons having halogen substitution and mixtures of the abovementioned solvents.

5. A process as claimed in claim 4, wherein the mass flow of scrubbing liquid additionally supplied to the scrubbing column is adjusted so as to be from 20% to 100% of the mass flow of the gaseous stream of primary amine from step (i).

6. A process as claimed in any of the preceding claims, wherein the liquid stream obtained in the wash column comprising wash liquor and isocyanate is passed to the work-up in step (vii).

7. A process as claimed in any one of the preceding claims, which comprises step (viii-1), wherein the quench liquid used in step (iv) comprises the liquid stream comprising isocyanate obtained in step (viii-1) in addition to the cooled, but otherwise unchanged composition of the liquid phase obtained in step (vi).

8. A process as claimed in any one of the preceding claims, wherein the quench liquid used in step (iv) comprises the liquid stream obtained in step (viii-2) comprising washing liquid and isocyanate, in addition to the cooled, but otherwise unchanged composition of the liquid phase obtained in step (vi).

9. A process as claimed in any one of claims 1 to 6 wherein the quench liquid used in step (iv) contains no other components than the cooled, but otherwise compositionally unchanged, liquid phase obtained in step (vi).

10. A process as claimed in any of the preceding claims, wherein, in order to obtain the isocyanate, the liquid phase comprising the isocyanate is subjected to distillative purification in step (vii) without a solvent column located therebetween.

11. The process as claimed in claim 10, wherein the distillative purification is carried out in a single distillation column, which is configured in particular as a dividing wall column.

12. A process as claimed in any one of the preceding claims, wherein each individual quench liquid stream used in step (iv) comprises a proportion of organic solvent of up to 25 mass%, based on its total mass.

13. A process as claimed in any one of the preceding claims wherein said primary amine is selected from the group consisting of toluene diamine, diphenylmethane diamine, xylylenediamine, pentane-1, 5-diamine, hexamethylene-1, 6-diamine, isophorone diamine, diaminodicyclohexylmethane and mixtures of the foregoing.

14. The method as recited in claim 13, wherein the primary amine is toluene diamine.

15. A process as claimed in any of the preceding claims, wherein in step (viii-2) the amount of organic solvent introduced into the wash column via the additionally supplied wash liquor is at most such that a proportion of organic solvent of from 0.0% by mass to 5.0% by mass, based on its total mass, is established in the liquid stream comprising wash liquor and isocyanate obtained in the wash column.

Example (b):