# US 9,040,758 B2 · Washing system for nitroaromatic compounds > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,040,758 B2 - Document ID: US9040758B2 - Status: Granted - Kind: B2 - Application number: 13/388,836 - Filed: 2009-08-18 - Published: 2012-05-31 - Granted: 2015-05-26 - Earliest claimed: 2009-08-18 - Assignees: Noram International Limited - Applicants: Sergio Berretta - Inventors: Sergio Berretta - Web page: https://patentgrep.com/patent/US9040758B2 ## CPC - C07C 201/16: Separation; Purification; Stabilisation; Use of additives - C02F 1/04: by distillation or evaporation - C02F 1/20: by degassing, i.e. liberation of dissolved gases (degasification of liquids in general B01D19/00; arrangement of degassing apparatus in boiler feed supply F22D) - C02F 2101/38: containing nitrogen - C02F 2209/06: pH - C07C: ACYCLIC OR CARBOCYCLIC COMPOUNDS - C02F: TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE (separation in general B01D; special arrangements on waterborne vessels of installations for treating water, waste water or sewage, e.g. for producing fresh water, B63J; adding materials to water to prevent corrosion C23F; treating radioactively-contaminated liquids G21F9/04; regeneration of reactants for recirculation into processes, see the relevant places for the processes) ## Abstract A method of removing alkalinity and salt from a nitroaromatic product downstream of water washing to remove mineral acids and alkaline washing to remove salts of organic acids, comprises washing the product stream with an acidic aqueous solution, prior to the step of removing excess organic reactant, by steam stripping or distillation. Acid removed from the stripper or column is recycled back for use in the acidic washing. The acidic washing is done instead of the neutral washing step of the prior art. It removes residual salt and decreases the level of entrained colloidal water in the nitroaromatic product. ## Claims ### Claim 1 A method of removing impurities from a product stream comprising a nitroaromatic product, comprising the steps of: (a) alkaline washing the nitroaromatic product stream to remove acidic organic by-products; and (b) washing the nitroaromatic product stream from step (a) with an acidic aqueous solution. ### Claim 2 (depends on 1) A method according to claim 1, further comprising the step of water washing the product stream upstream of step (a) to remove mineral acids. ### Claim 3 (depends on 1) A method according to claim 1, further comprising the step of (c) removing residual organic reactant from the product stream from step (b). ### Claim 4 (depends on 3) A method according to claim 3, wherein step (c) comprises one of steam stripping and distillation. ### Claim 5 (depends on 3) A method according to claim 3, wherein step (c) comprises steam stripping and the method further comprises the step of using acid from step (c) in step (b). ### Claim 6 (depends on 3) A method according to claim 3, wherein step (c) comprises distillation and the method further comprises the step of using acid from step (c) in step (b). ### Claim 7 (depends on 4) A method according to claim 4, wherein the acidic aqueous solution of step (b) comprises an acid that is volatile under conditions used in the steam stripping or distillation. ### Claim 8 (depends on 1) A method according to claim 1, wherein the acidic aqueous solution of step (b) comprises nitric acid or nitrous acid. ### Claim 9 (depends on 1) A method according to claim 1, wherein step (b) is carried out at a pH of 6 or less. ### Claim 10 (depends on 1) A method according to claim 1, wherein step (b) is carried out at a pH of 5 or less. ### Claim 11 (depends on 1) A method according to claim 1, wherein step (b) is carried out at a pH in the range of 2 to 5. ### Claim 12 (depends on 4) A method according to claim 4, wherein liquid condensed from the top of a steam stripper or a distillation column comprises one or both of nitric acid solution and nitrous acid solution. ### Claim 13 (depends on 12) A method according to claim 12, wherein the condensed liquid comprising one or both of nitric acid solution and nitrous acid solution is used in step (b). ### Claim 14 (depends on 1) A method according to claim 1, wherein step (b) is done in a single stage. ### Claim 15 (depends on 1) A method according to claim 1, wherein step (b) is done in a plurality of stages having a flow pattern that is one of cross-current, counter-current and co-current. ### Claim 16 (depends on 1) A method according to claim 1, wherein the impurities removed in step (b) comprise alkalinity and salt. ### Claim 17 (depends on 2) A method according to claim 2, wherein the water washing or the alkaline washing, or both, are done in a plurality of stages having a flow pattern that is one of cross-current, counter-current and co-current. ### Claim 18 (depends on 1) A method according to claim 1, wherein the nitroaromatic product is one of mononitrobenzene, nitrotoluene and dinitrotoluene. ### Claim 19 (depends on 1) A method according to claim 1, wherein the nitroaromatic product is mononitrobenzene. ### Claim 20 A method of removing impurities from a product stream comprising a nitroaromatic product, comprising the steps of: (a) washing the nitroaromatic product stream with water to remove mineral acids; (b) washing the nitroaromatic product stream from step (a) with an acidic aqueous solution to remove hydrophilic acids; and (c) removing residual organic reactant from the nitroaromatic product stream from step (b) by one of steam stripping and distillation. ### Claim 21 (depends on 20) A method according to claim 20, wherein step (c) comprises steam stripping and the method further comprises the step of using acid from step (c) in step (b). ### Claim 22 (depends on 20) A method according to claim 20, wherein step (c) comprises distillation and the method further comprises the step of using acid from step (c) in step (b). ### Claim 23 (depends on 20) A method according to claim 20, wherein the acidic aqueous solution of step (b) comprises an acid that is volatile under conditions used in the steam stripping or distillation. ### Claim 24 (depends on 20) A method according to claim 20, wherein the acidic aqueous solution of step (b) comprises nitric acid or nitrous acid. ### Claim 25 (depends on 20) A method according to claim 20, wherein step (b) is carried out at a pH of 6 or less. ### Claim 26 (depends on 20) A method according to claim 20, wherein step (b) is carried out at a pH of 5 or less. ### Claim 27 (depends on 20) A method according to claim 20, wherein step (b) is carried out at a pH in the range of 2 to 5. ### Claim 28 (depends on 20) A method according to claim 20, wherein liquid condensed from the top of a steam stripper or a distillation column comprises one or both of nitric and nitrous acid solution. ### Claim 29 (depends on 28) A method according to claim 28, wherein the condensed liquid is used in step (b). ### Claim 30 (depends on 20) A method according to claim 20, wherein step (b) is done in a single stage. ### Claim 31 (depends on 20) A method according to claim 20, wherein step (b) is done in a plurality of stages having a flow pattern that is one of cross-current, counter-current and co-current. ### Claim 32 (depends on 20) A method according to claim 20, wherein the hydrophilic acids removed in step (b) are used in step (a). ### Claim 33 (depends on 20) A method according to claim 20, wherein the water washing is done in a plurality of stages having a flow pattern that is one of cross-current, counter-current and co-current. ### Claim 34 (depends on 20) A method according to claim 20, wherein the nitroaromatic product is one of mononitrobenzene, nitrotoluene and dinitrotoluene. ### Claim 35 (depends on 20) A method according to claim 20, wherein the nitroaromatic product is mononitrobenzene.