Abstract
The present invention relates to a continuous process for preparing phosgene as well as a production unit for carrying out said process.
Claims
1.-17. (canceled)
18. A continuous process for preparing phosgene, comprising (i) providing a gas stream G1 comprising carbon monoxide (CO) and chlorine (Cl.sub.2); (ii) passing the gas stream G1 into a reaction zone Z1, bringing the gas stream G1 into contact with a catalyst C1 comprised in said reaction zone Z1, obtaining a gas stream GP comprising phosgene and one or more of carbon monoxide and chlorine, and removing the gas stream GP from said reaction zone Z1; (iii) dividing the gas stream GP, obtaining at least two gas streams comprising a gas stream G2 and a gas stream GR, G2 and GR having the same chemical composition as GP, wherein the ratio of the mass flow f(GR) of the gas stream GR relative to the mass flow f(G2) of the gas stream G2, f(GR):f(G2), is in the range of from 0.1:1 to 20:1; wherein during standard operation mode of the continuous process, providing the gas stream G1 according to (i) comprises preparing G1 as a mixture comprising at least two gas streams, said at least two streams comprising the gas stream GR and j gas streams G0(k) with k=1, . . . j, wherein the j gas streams G0(k) in total comprise carbon monoxide (CO) and chlorine (Cl.sub.2) and wherein j is in the range of from 1 to 3.
19. The process of claim 18, wherein j is 1 or 2.
20. The process of claim 18, wherein f(GR):f(G2) is in the range of from 0.2:1 to 10:1.
21. The process of claim 18, wherein during standard operation mode of the continuous process, providing the gas stream G1 according to (i) comprises preparing G1 as a mixture comprising, three gas streams, said three gas streams being the gas stream GR and two gas streams G0(1) and G0(2), wherein the two gas streams G0(1) and G0(2) in total comprise carbon monoxide (CO) and chlorine (Cl.sub.2).
22. The process of claim 18, wherein during standard operation mode of the continuous process, providing the gas stream G1 according to (i) comprises preparing G1, as a mixture comprising three gas streams GR, G0(1) and G0(2), G0(1) comprising carbon monoxide (CO) and G0(2) comprises chlorine (Cl.sub.2), which comprises combining the gas stream G0(1) with the gas stream G0(2) and admixing the gas stream GR with the combined gas streams G0(1) and G0(2).
23. The process of claim 22, wherein admixing the gas stream GR with the combined two gas streams G0(1) and G0(2) according to (i) is performed in a mixing device, wherein the mixing device is an ejector, a static mixer or a dynamic mixer.
24. The process of claim 22, wherein the mole ratio of the amount of chlorine, in mol, to the amount of carbon monoxide, in mol, in the combined gas streams G0(1) and G0(2) is in the range of from 0.6:1 to 0.999:.
25. The process of claim 18, wherein during standard operation mode of the continuous process, providing the gas stream G1 according to (i) comprises preparing G1, as a mixture comprising three gas streams GR, G0(1) and G0(2), G0(1) comprising carbon monoxide (CO) and G0(2) comprises chlorine (Cl.sub.2), which comprises admixing the gas stream G0(1) with the gas stream GR, and combining the gas stream G0(2) with the admixed gas streams G0(1) and GR.
26. The process of claim 18, wherein during standard operation mode of the continuous process, providing the gas stream G1 according to (i) comprises preparing G1, as a mixture comprising three gas streams GR, G0(1) and G0(2), G0(1) comprising carbon monoxide (CO) and G0(2) comprises chlorine (Cl.sub.2), which comprises admixing the gas stream G0(2) with the gas stream GR, and combining the gas stream G0(1) with the admixed gas streams G0(2) and GR.
27. The process of claim 18, wherein the reaction zone Z1 comprises a reactor comprising the catalyst C1, wherein the reactor is a tubular reactor comprising one or more tubes, the catalyst C1 being filled in said one or more tubes.
28. The process of claim 27, wherein the gas stream in the reactor is of at most 450? C. the temperature being measured with a multipoint thermocouple.
29. The process of claim 18, further comprising, after (iii), passing the gas stream GR through a return means R prior to preparing G1 as a mixture comprising at least two streams according to (i), during standard operation mode of the continuous process, in an ejector.
30. The process of claim 18, wherein the catalyst C1 is a carbon catalyst.
31. The process of claim 30, wherein the catalyst C1 comprises a porous material comprising carbon, micropores and mesopores, wherein said micropores have a pore diameter, determined according to DIN 66135-2, of less than 2 nm and wherein said mesopores have a pore diameter, determined according to DIN 66134, in the range of from 2 to 50 nm, wherein the volume of the mesopores of the porous material, determined according to dual-isotherm Nonlocal Density Functional Theoretical (NLDFT) Advanced Pore Size Distribution (PSD) technique, is of at least 0.45 ml/g.
32. The process of claim 18, further comprising (iv) passing the stream G2 into a reaction zone Z2, bringing the gas stream G2 into contact with a catalyst C2 comprised in said reaction zone Z2, obtaining a gas stream GF comprising phosgene, and removing the gas stream GF from said reaction zone Z2.
33. A production unit for carrying out the process according to claim 18, the unit comprising a reaction zone Z1 comprising an inlet means for passing the gas stream G1 into Z1; a catalyst C1; a reaction means for bringing into contact the gas stream G1 with said catalyst C1; an outlet means for removing the gas stream GP from Z1; a stream dividing device S for dividing the gas stream GP in at least two streams comprising a gas stream GR and a gas stream G2; a means for passing the gas stream GP into said device S; at least one means M for preparing G1 as a mixture comprising at least two streams; a return means R for passing the gas stream GR exiting from S to said means M for preparing G1.
34. Use of the production unit according to claim 33 for the continuous production of phosgene.
Description
DESCRIPTION OF THE FIGURES
[0297] FIG. 1a: represents the temperature profile obtained when preparing phosgene with the process of Comparative Example 1 and the process of Example 1.
[0298] FIG. 1b: represents the temperature profile obtained when preparing phosgene with the processes of Example 1 and Example 2.
[0299] FIG. 2a: is a schematic representation of a production unit according to embodiments of the invention. The production unit comprises a reaction zone Z1 comprising an inlet means, such as a pipe, for passing the gas stream G1 into Z1 and a reaction means, a cooled reactor, for bringing into contact the gas stream G1 with a catalyst C1, preferably a carbon containing catalyst not represented on the figure. The cooled reactor is a tubular reactor comprising one or more tubes, preferably more than one tube, preferably a cooled tube-bundle reactor. Such reactor is cooled with a heat transfer/coolant medium, preferably monochlorobenzene. The coolant medium inlet temperature can range between 60 and 100? C. The maximum gas stream temperature in the reactor was set to 400? C.(hot-spot). Further, the reaction zone Z1 comprises an outlet means, for example a pipe, for removing the gas stream GP from Z1. The gas stream GP comprises phosgene and one or more of carbon monoxide and chlorine. At the outlet end of the reaction Z1, 90-100% of chlorine is converted. The production unit further comprises a stream dividing device for dividing the gas stream GP in two streams, a gas stream GR and a gas stream G2, a means, such as a pipe, for passing the gas stream GP into the stream dividing device not represented in this figure. The gas streams G2 and GR have respectively the same chemical composition as GP. The temperature of the gas stream GP, GR and G2 was of 80?5? C. Such temperature could range from 60 to 100? C. The production unit further comprises a means E, preferably an ejector, for admixing the gas stream G0 (G0(1)+G0(2)) with the gas stream GR comprising an inlet means, such as a pipe, for feeding the gas stream G0 into E and a means for feeding the gas stream GR into E. The gas stream G0 consists of CO and Cl.sub.2, with 5% excess of CO. The gas streams G0(1) and G0(2) not represented on the figure were mixed in a static mixer upstream of the ejector E. The recycle ratio is the ratio of the mass flow f(GR) of the gas stream GR relative to the mass flow f(GP) of the gas stream GP, f(GR):f(GP), which is in the range of from 0.2:1 to 0.8:1, preferably in the range of from 0.3:1 to 0.7:1, more preferably in the range of from 0.35:1 to 0.6:1. The production unit further comprises a return means R, a return pipe, for passing the gas stream GR exiting from the stream dividing device to said means E. The phosgene is produced at a surface load of 3 kg/m.sup.2s.
[0300] FIG. 2b: is a schematic representation of a production unit according to embodiments of the invention. The production unit of FIG. 2b comprises the components of FIG. 2a, except that for preparing G1, G0(1) (CO gas stream) drives the ejector E wherein the gas stream GR is admixed and G0(2) is combined downstream of the ejector E.
[0301] FIG. 3: is a schematic representation of a production unit according to embodiments of the invention. The production unit of FIG. 3 comprises the components of FIG. 2 and further comprises a reaction zone Z2 comprising an inlet means, such as a pipe, for passing the gas stream G2 into Z2. The reaction zone Z2 comprises a reaction means, preferably a cooled reactor, for bringing into contact the gas stream G1 with a catalyst C2, preferably a carbon containing catalyst, and an outlet means, such as a pipe, for removing the gas stream GF from Z2. The cooled reactor is a tubular reactor comprising one or more tubes, preferably more than one tube, more preferably a cooled tube-bundle reactor. Such reactor is cooled with a heat transfer/coolant medium, preferably monochlorobenzene. Alternatively, an adiabatic fixed-bed can be used in the reaction zone Z2 as the reaction means. The gas stream GF comprises phosgene. At the outlet end of the reaction zone Z2, more than 99.5% of chlorine was converted. The phosgene is produced at a surface load of about 3 kg/m.sup.2s.
[0302] FIG. 4: is a schematic representation of a production unit according to embodiments of the invention. The production unit comprises a reaction zone Z1 comprising an inlet means, such as a pipe, for passing the gas stream G1 into Z1 and a reaction means, an uncooled reactor, for bringing into contact the gas stream G1 with a catalyst C1, preferably a carbon containing catalyst not represented on the figure. The gas stream G1 has a temperature of 75? C. The uncooled reactor is an adiabatic fixed-bed reactor. The reactor has a diameter of 4.7 m and a length of 3.6 m and was filled with 4mm carbon extrudates (from DONAU CARBON). The maximum gas stream temperature in the reactor was of about 300? C.(hot-spot). Further, the reaction zone Z1 comprises an outlet means, for example a pipe, for removing the gas stream GP from Z1. The gas stream GP comprises phosgene and one or more of carbon monoxide and chlorine. At the outlet end of the reaction Z1, 95% of chlorine is converted. The production unit further comprises a stream dividing device S for dividing the gas stream GP in two streams, a gas stream GR and a gas stream G2, a means, such as a pipe, for passing the gas stream GP into S. The gas streams G2 and GR have respectively the same chemical composition as GP. The temperature of the gas stream GP, GR and G2 was of 300? C. The production unit further comprises a means E, preferably an ejector, for admixing the gas stream G0 and the gas stream GR comprising an inlet means, such as a pipe, for feeding the gas stream G0 (G0(1)+G0(2)) into E and a return means for feeding the gas stream GR into E. The gas stream G0 consists of CO and Cl.sub.2 and has a pressure P0 of 8 bara. The recycle ratio is the ratio of the mass flow f(GR) of the gas stream GR relative to the mass flow f(GP) of the gas stream GP, f(GR):f(GP), which can in the range of from 0.20:1 to 0.95:1, preferably in the range of from 0.50:1 to 0.92:1, more preferably in the range of from 0.70:1 to 0.90:1. In the present case, f(GR):f(GP)=0.86:1. The production unit further comprises a return means R, a return pipe, for passing the gas stream GR exiting from the stream dividing device to said means E and a heat exchanger H. Said return pipe R is cut in two pipes R1 and R2, a pipe R1 exiting the device S toward the heat exchanger H and a pipe R2 exiting said heat exchanger toward an inlet end of the means E. The gas stream GR has a pressure PR of about 4 bara. The temperature of the gas stream G1 is of about 75? C. and the gas stream G1 has a pressure of 4.5 bara. The production unit further comprises a reaction zone Z2 downstream of the device S. Said zone, not shown in this figure, comprises an inlet means, such as a pipe, for passing the gas stream G2 into Z2. The reaction zone Z2 comprises a reaction means, a cooled reactor, for bringing into contact the gas stream G1 with a catalyst C2, preferably a carbon containing catalyst, and an outlet means, such as a pipe, for removing the gas stream GF from Z2. The cooled reactor is a tubular reactor comprising one or more tubes, preferably more than one tube, more preferably a cooled tube-bundle reactor. Such reactor is cooled with a heat transfer medium, preferably mono-chlorobenzene. The gas stream GF comprises phosgene. At the outlet end of the reaction zone Z2, 100% of chlorine is converted. The phosgene is produced at a load of 39 t/h.
[0303] FIG. 5: is a schematic representation of a production unit according to embodiments of the invention. The production unit comprises a reaction zone Z1 comprising an inlet means for passing the gas stream G1 into Z1 and a reaction means, an uncooled reactor R1, for bringing into contact the gas stream G1 with a catalyst C1, preferably a carbon containing catalyst not represented on the figure. The adiabatic bed has a diameter of 4.7 m, a length of 3.6 m and is filled with 4 mm carbon extrudates. The maximum gas stream temperature in the reactor was of at most 400? C.(hot-spot), preferably 300? C. Further, the reaction zone Z1 comprises an outlet means for removing the gas stream GP from Z1. The gas stream GP comprises phosgene and one or more of carbon monoxide and chlorine. The gas stream GP is directly fed into a cooling means, multiple cooling tubes C which are cooled with a coolant medium, such as monochlorobenzene. At the outlet end of said cooling tubes C, a stream dividing device, not shown in the figure, divides the cooled gas stream GP in two streams, a gas stream GR and a gas stream G2. The gas streams G2 and GR have respectively the same chemical composition as GP. The temperature of the gas stream GP, GR and G2 was of about 75? C. The production unit further comprises a means E, preferably an ejector, for admixing the gas stream G0 (G0(1)+G0(2)) and the gas stream GR comprising an inlet means, such as a pipe, for feeding the gas stream G0 into E and a means for feeding the gas stream GR into E. The means E, the reactor R1, the multiple tubes C, all are in one housing. The gas stream G0 consists of CO and Cl.sub.2. The flow rate ratio of the gas stream GR to the gas stream GP is the range of from 0.2:1 to 0.909:1, preferably in the range of from 0.3:1 to 0.7:1, more preferably in the range of from 0.35:1 to 0.6:1. The production unit further comprises a reaction zone Z2. Said zone, not shown in this figure, comprises an inlet means, such as a pipe, for passing the gas stream G2 into Z2. The reaction zone Z2 comprises a reaction means, a cooled reactor, for bringing into contact the gas stream G1 with a catalyst C2, preferably a carbon containing catalyst, and an outlet means, such as a pipe, for removing the gas stream GF from Z2. The cooled reactor is a tubular reactor comprising one or more tubes, preferably more than one tube, more preferably a cooled tube-bundle reactor. Such reactor is cooled with a coolant medium, preferably mono-chlorobenzene. The gas stream GF comprises phosgene. At the outlet end of the reaction zone Z2, 100% of chlorine was converted.
[0304] FIG. 6: is a schematic representation of a production unit according to embodiments of the invention. The production unit of said Figure is as the one of FIG. 2a, except that the cooled reactor comprise a different cooling system, namely with two cooling zones. On the Figure, L represents the length of the cooled tubes of the reactor, L1 represents the length of the first cooling zone of the reactor which runs at higher temperatures and L2 represents the length of the second cooling zone of the reactor for the final cooling. It is preferred that 1 m?L2?1.5 m, more preferably L2=1.3 m. Further, a represents the inlet of the coolant medium used in the first cooling zone, b represents the outlet of the coolant medium used in the first cooling zone, c represents the inlet of the coolant medium used in the second cooling zone, d represents the outlet of the coolant medium used in the second cooling zone. It is believed that this configuration with two zones will permit to save the heat generation which took place in the reaction zone Z1 for production of high worthy steam. The first cooling zone can be for example running on an temperature range of from 200 to 300? C., preferred about 250? C. With a heat transfer oil passing in the first cooling zone, the heat produced from the reaction of the catalyst C1 in a reactor of the reaction zone Z1 could then be removed from the reactor of the reaction zone Z1. The oil recovered from the first cooling zone can thus serve to heat a solvent (such as water) in a other heat exchanger (outside of the production unit for preparing phosgene). The second cooling zone can be running under normal conditions, namely at about 80? C. A reactor with more than one cooling zone can be such as described in WO 03/072237 A1.
[0305] FIG. 7: represents the temperature profile obtained when preparing phosgene with the process of Comparative Examples 2 and 3 and with the process of Example 5.
CITED LITERATURE
[0306] Christopher J. Mitchell et al., Selection of carbon catalysts for the industrial manufacture of phosgene, Hunstman Polyurethanes, Catal. Sci. Technol., 2012, 2109-2115 [0307] WO 2012/092210 A1 [0308] Ullmann's Encyclopedia of industrial chemistry, Chapter, Phosgene 5.sup.th Ed. Vol. A 19, p 413 ff., VCH Verlagsgesellschaft mbH, Weinheim, 1991 [0309] WO 03/072237 A1 [0310] DE 10110847 A1
