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US-12617685-B2 - Process, reaction mixture and catalyst for the production of phosgene

US12617685B2US 12617685 B2US12617685 B2US 12617685B2US-12617685-B2

Abstract

The invention relates to a process for the production of phosgene comprising a gas phase reaction of carbon monoxide and chlorine in the presence of a carbon catalyst in a multi-tubular reactor, wherein the carbon catalyst comprises an amount of mesopores having a pore diameter in the range of from 2 to 50 nm of at least 0.45 ml/g of the total pore volume and the use of a carbon catalyst comprising an amount of mesopores having a pore diameter in the range of from 2 to 50 nm of at least 0.45 ml/g of the total pore volume, for the production of phosgene and a reaction mixture for preparing phosgene, the mixture comprising a catalyst for preparing phosgene comprising a porous material comprising carbon, micropores and mesopores, wherein said micropores have a pore diameter of less than 2 nm and wherein said mesopores have a pore diameter in the range of from 2 to 50 nm, wherein the volume of the mesopores of the porous material is of at least 0.45 ml/g, and a gas stream G comprising carbon monoxide (CO) and chlorine (Cl 2 ).

Inventors

  • Gerhard Olbert
  • Jim BRANDTS
  • Benjamin Kron
  • Jochen Gauer
  • Jens Ferbitz
  • Torsten Mattke
  • Kai Thiele
  • Peter van den Abeel
  • Koenraad Vandewalle
  • Kirill Bramnik

Assignees

  • BASF SE

Dates

Publication Date
20260505
Application Date
20210510
Priority Date
20200520

Claims (17)

  1. 1 . A process for the production of phosgene comprising a gas phase reaction of carbon monoxide and chlorine in the presence of a carbon catalyst in a multi-tubular reactor, wherein the carbon catalyst comprises an amount of mesopores having a pore diameter in the range of from 2 to 50 nm of at least 0.45 ml/g of the total pore volume, wherein the volume fraction, of the mesopores having a pore diameter from 2 to 50 nm, is in the range of from 50% to 90% of the total pore volume.
  2. 2 . The process according to claim 1 , wherein the total pore volume of the carbon catalyst is at least 0.5 ml/g measured by nitrogen adsorption.
  3. 3 . The process according to claim 1 , wherein the total pore volume of the carbon catalyst is in the range of from 0.5 ml/g to 2 ml/g measured by nitrogen adsorption.
  4. 4 . The process according to claim 1 , wherein the BET surface of the carbon catalyst is at least 500 m 2 /g.
  5. 5 . The process according to claim 1 , wherein the BET surface of the carbon catalyst is in the range of from 500 m 2 /g to 2500 m 2 /g.
  6. 6 . The process according to claim 1 , wherein the carbon catalyst is a pyrolyzed carbon aerogel.
  7. 7 . The process according to claim 6 , wherein the carbon catalyst is an activated pyrolyzed carbon aerogel.
  8. 8 . The process according to claim 1 , wherein the carbon catalyst has a total impurity content of elements having atomic numbers ranging from 11 to 92 as measured by total reflection x-ray fluorescence (TXRF) of less than 500 ppm.
  9. 9 . The process according to claim 1 , wherein the reaction takes place in a tube-bundle reactor with catalyst filled inside the tubes.
  10. 10 . The process according to claim 1 , wherein a cooling media on a shell side is liquid or a boiling liquid.
  11. 11 . The process according to claim 1 , wherein a feed stream has a stoichiometric excess of carbon monoxide to chlorine of 0.0001 to 50 mol %.
  12. 12 . The process according to claim 1 , wherein the reaction takes place at a pressure of 1 to 10 bara.
  13. 13 . The process according to claim 11 , wherein the feed stream is supplied with an absolute pressure in the range of 0.5 to 20 bar.
  14. 14 . The process according to claim 1 , wherein the reaction is carried out at a surface load of 0.5 to 6 kg phosgene/m 2 s.
  15. 15 . The process according to claim 1 , wherein the contact tubes are passed by at least one fluid heat carrier in separate cooling zones.
  16. 16 . The process according to claim 15 , wherein as a fluid heat carrier a liquid heat carrier is used.
  17. 17 . The process according to claim 15 , wherein the least one fluid heat carrier is used to produce directly or indirectly steam.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a national stage application (under 35 U.S.C. § 371) of PCT/EP2021/062268, filed May 10, 2021, which claims benefit of European Application Nos. 20175603.8, filed May 20, 2020, and 21169639.8, filed Apr. 21, 2021, all of which are incorporated herein by reference in their entirety. The invention relates to a process for the production of phosgene by gas phase reaction of carbon monoxide and chlorine in the presence of a catalyst, in particular in the presence of a specifically designed carbon catalyst and a reaction mixture for preparing phosgene comprising a catalyst, a catalyst for preparing phosgene comprising a porous material, and to the use of said mixture and a catalyst for preparing phosgene. Further, the present invention relates to a process for preparing said catalyst. Phosgene is an important excipient in the production of intermediate and end products in almost all branches of chemistry. In particular phosgene represents a widely used reagent for industrial carbonylation, for example in the production of isocyanates or organic acid chlorides. The largest field of use in terms of volume is the production of diisocyanates for polyurethane chemistry, in particular toluene diisocyanate or 4,4-diisocyanate diphenylmethane. Phosgene is produced in large-scale in a catalytic gas phase reaction of carbon monoxide and chlorine in the presence of a catalyst, for example, an activated carbon catalyst, according to the reaction equation: CO+Cl2⇄COCl2 The reaction is strongly exothermic with a reaction enthalpy ΔH of −107.6 kJ/mol. To remove the reaction heat the reaction is normally carried out in tube-bundle reactors with catalyst filled inside the tubes (see Ullmann's Encyclopedia of industrial chemistry, Chapter “Phosgene” 5th Ed. Vol. A 19, p 413 ff., VCH Verlagsgesellschaft mbH, Weinheim, 1991). Generally, granular catalyst with a grain size in the range of from 3 to 5 mm is used in pipes with a typical inner diameter between 35 and 70 mm, typically between 39 and 45 mm. The reaction starts at temperatures of 40 to 50° C., but the temperature within the pipes increases up to 400° C. or even higher. In the reaction, carbon monoxide is usually used in excess to ensure that all chlorine is converted, and largely chlorine-free phosgene is produced, since chlorine can lead to undesirable side reactions in the subsequent use of phosgene. The reaction can be carried out without pressure but is usually carried out at an overpressure of 200-600 kPa (2-6 bar). In this pressure range, the formed phosgene can be condensed after the reactor with cooling water or other heat carrier, for example organic heat carrier can be used, so that the condenser can be operated more economically. Heat management within the reactor is one of the main challenges in phosgene production necessary for performing a safe and economic process. In general, different methods are available to handle the reaction heat. The main influence on the heat management are a specific reactor design and catalyst selection or design, allowing for a fast removal of the resulting reaction heat by reducing heat and mass transport limitations. In the prior art a broad variety of reactor designs is described. Generally, the contact tubes of the tube bundle reactor are rinsed by a heat carrier, which dissipates the resulting reaction heat from the reactor. It has been shown that a transverse flow of the contact tubes improves the heat dissipation. To achieve this, usually deflection plates are installed in the reactor, which allow by a meander-shaped flow of the heat carrier a transverse flow to the contact tubes of the heat carrier. For example, a typical large-scale reactor for the production of phosgene is described in the international patent application WO 03/072237 A1. The throughput of the reactor can be specified by the so-called surface load or phosgene load of the reactor, which is defined as the amount of converted phosgene per unit of time (usually expressed in kg/s), based on the cross-sectional area of the catalyst, i.e. the sum of the inner cross-sectional surfaces of the catalytic contact tubes (usually specified in m2). In order to control the reaction heat, therefore, surface loads between 0.5 and 2 kg of phosgene/m2s are usually applied in the prior art. The phosgene surface load is thus essentially determined on the assumption of a complete conversion of the component, which is not in excess, i.e. in the case of excess carbon monoxide by the chlorine feed. The term “reactor” in the present application covers all parts of a plant in which the chemical conversion of carbon monoxide and chlorine gas to phosgene takes place. Often, a reactor in this sense is a single component defined by a reactor vessel. However, a reactor within the meaning of the present application may also comprise two or more components with separate reactor tanks, which are arranged, for example, one afte