# US 11,028,046 B2 · Toluene diisocyanate purification method > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,028,046 B2 - Document ID: US11028046B2 - Status: Granted - Kind: B2 - Application number: 16/463,972 - Filed: 2017-12-12 - Published: 2020-12-03 - Granted: 2021-06-08 - Earliest claimed: 2016-12-15 - Assignees: Hanwha Chemical Corporation - Applicants: Hanwha Chemical Corporation - Inventors: Hyun Cheol Ryu; Kee Do Han; Seong Ho Park; Chang Mo Chung - Web page: https://patentgrep.com/patent/US11028046B2 ## CPC - C07C 263/20: Separation; Purification - B01D 3/009: {in combination with chemical reactions} - B01D 3/141: {where at least one distillation column contains at least one dividing wall} - B01D 3/322: {Reboiler specifications} - B01D 5/006: {with evaporation or distillation} - C07C: ACYCLIC OR CARBOCYCLIC COMPOUNDS - B01D: SEPARATION (separating solids from solids by wet methods B03B, B03D; by pneumatic jigs or tables B03B; by other dry methods B07; magnetic or electrostatic separation of solid materials from solid materials or fluids, separation by high-voltage electric fields B03C; centrifuges, vortex apparatus B04; presses per se for squeezing-out liquid from liquid-containing material B30B9/02; treatment of water C02F, e.g. softening by ion-exchange C02F1/42; {arrangements of air intake cleaners in gas turbine plants F02C7/05} ; arrangements or mounting of filters in air-conditioning, air-humidification or ventilation F24F13/28) ## Abstract The present invention relates to a toluene diisocyanate purification method enabling acquisition of a product having a small amount of dimers in a final product by means of using a reactive dividing wall column during toluene diisocyanate preparation. More particularly, according to the present invention, in order to obtain a product having a small amount of dimers in accordance with a reversible reaction of a monomer and a dimer, a purification procedure is designed by means of applying the temperature, pressure, time of stay and the like of a reactive dividing wall column as appropriate particular conditions, a reboiler having short time of stay and high heat transfer rate is used, and thus a dimerization reaction is inhibited and the purity and yield of the product are enhanced. Therefore, high-purity toluene diisocyanate can be purified and obtained. ## Claims ### Claim 1 A toluene diisocyanate purification method comprising: separating and purifying toluene diisocyanate by feeding a mixture containing toluene diisocyanate as a main component to a reactive dividing wall column equipped with a condenser and a reboiler, wherein a pressure of the condenser is maintained at 50 torr or less, and a temperature of the condenser is maintained at 130° C. or less, a total pressure difference in the reactive dividing wall column is maintained at 40 torr or less, a retention time of the reaction mixture in the reactive dividing wall column is maintained within 10 seconds to 150 seconds, and a pressure of the reboiler is maintained at 30 torr or less, and a temperature of the reboiler is maintained at 160° C. or less. ### Claim 2 (depends on 1) The toluene diisocyanate purification method of claim 1, wherein: the mixture containing toluene diisocyanate as a main component includes toluene diisocyanate, a toluene diisocyanate dimer, a low-boiling component, and a high-boiling component, and the mixture containing toluene diisocyanate as a main component is obtained by separating unreacted materials and a solvent from a mixture in which phosgene and toluenediamine are reacted in the solvent. ### Claim 3 (depends on 2) The toluene diisocyanate purification method of claim 2, wherein: the mixture containing toluene diisocyanate as a main component includes 92 to 96 wt % of toluene diisocyanate, 0.01 to 1 wt % of the toluene diisocyanate dimer, 0.1 to 2 wt % of the low-boiling component, and 2 to 10 wt % of the high-boiling component, based on a total weight of the entire mixture. ### Claim 4 (depends on 1) The toluene diisocyanate purification method of claim 1, wherein: the condenser is maintained at a pressure of 9 to 50 torr and a temperature of 10 to 130° C. ### Claim 5 (depends on 1) The toluene diisocyanate purification method of claim 1, wherein: the total pressure difference in the reactive dividing wall column is maintained at 9 to 40 torr. ### Claim 6 (depends on 1) The toluene diisocyanate purification method of claim 1, wherein: the retention time of the reaction mixture in the reactive dividing wall column is maintained within 10 seconds to 60 seconds. ### Claim 7 (depends on 1) The toluene diisocyanate purification method of claim 1, wherein: a retention time in the reboiler is maintained within 1 minute to 3 minutes. ### Claim 8 (depends on 1) The toluene diisocyanate purification method of claim 1, further comprising: after the separating and purifying of toluene diisocyanate, quenching the purified toluene diisocyanate using a quencher at a temperature of 40° C. or less. ### Claim 9 (depends on 8) The toluene diisocyanate purification method of claim 8, wherein: the quencher is connected to a side part of the reactive dividing wall column. ### Claim 10 (depends on 1) The toluene diisocyanate purification method of claim 1, wherein: the separated and purified toluene diisocyanate product comprises 2000 ppm or less of a toluene diisocyanate dimer. ### Claim 11 (depends on 1) The toluene diisocyanate purification method of claim 1, wherein: the reactive dividing wall column includes at least one condenser, a main column having a dividing wall, and at least one reboiler, and the main column includes a fractionation zone having a dividing wall that vertically divides the mixture containing toluene diisocyanate as a main component including toluene diisocyanate, a toluene diisocyanate dimer, a low-boiling component, and a high-boiling component into a preliminary fractionation zone and a main fractionation zone; a top zone for removing the low-boiling component; a feed zone for feeding the mixture containing toluene diisocyanate as a main component; a side draw zone for effusing the separated and purified toluene diisocyanate; and a bottom zone for removing the high-boiling component. ### Claim 12 (depends on 11) The toluene diisocyanate purification method of claim 11, wherein: the side draw zone is positioned at an intermediate stage between the top zone and the bottom zone. ### Claim 13 (depends on 11) The toluene diisocyanate purification method of claim 11, wherein: the fractionation zone represents 20% to 80% of the theoretical stages relative to total column stages of the main column.