Classifications

• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B7/00—Halogens; Halogen acids
  • C01B7/01—Chlorine; Hydrogen chloride
  • C01B7/03—Preparation from chlorides
  • C01B7/04—Preparation of chlorine from hydrogen chloride
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B17/00—Sulfur; Compounds thereof
  • C01B17/69—Sulfur trioxide; Sulfuric acid
  • C01B17/88—Concentration of sulfuric acid
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B17/00—Sulfur; Compounds thereof
  • C01B17/69—Sulfur trioxide; Sulfuric acid
  • C01B17/90—Separation; Purification
  • C01B17/94—Recovery from nitration acids
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B32/00—Carbon; Compounds thereof
  • C01B32/80—Phosgene
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B7/00—Halogens; Halogen acids
  • C01B7/01—Chlorine; Hydrogen chloride
  • C01B7/07—Purification ; Separation
  • C01B7/0743—Purification ; Separation of gaseous or dissolved chlorine
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C263/00—Preparation of derivatives of isocyanic acid
  • C07C263/10—Preparation of derivatives of isocyanic acid by reaction of amines with carbonyl halides, e.g. with phosgene
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C263/00—Preparation of derivatives of isocyanic acid
  • C07C263/18—Separation; Purification; Stabilisation; Use of additives
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C265/00—Derivatives of isocyanic acid
  • C07C265/14—Derivatives of isocyanic acid containing at least two isocyanate groups bound to the same carbon skeleton

Definitions

• the present invention relates to a process for the coupled production of chlorine and isocyanates, wherein the sulfuric acid used for both processes is combined after use, is concentrated together and flows back into one or both processes.
• Chlorine and nitroaromatics are important industrial intermediates used, for example, in the production of polyurethane raw materials, such as, for example, polyurethane.
• Toluylene diisocyanate (TDI) or Methylendiphe- nyldiisocyanat (MDI) are required.
• Chlorine gas is required for the production of phosgene, which is used for the production of isocyanates from amines, wherein the thereby produced as by-product hydrogen chloride (HCl) can be converted to chlorine by various recycling processes again.
• HCl by-product hydrogen chloride
• chlorine is also made from other raw materials such as e.g. Sodium chloride produced by electrolysis.
• the process gas is subjected to a drying step after the reaction and optionally first work-up steps such as the absorption of unreacted HCl, to optionally water contained in subsequent work-up steps, such as For example, the chlorine liquefaction or distillation, or applications may be troublesome to remove.
• concentrated sulfuric acid in the range of 90.0-98.0% by mass of sulfuric acid, based on mass fraction of sulfuric acid and water, is generally used as the drying agent. This produces large amounts of dilute sulfuric acid with a concentration of 70.0 to 89.9% by mass of sulfuric acid based on mass fractions of sulfuric acid and water, which must either be concentrated in energy expenditure in a distillation plant or disposed of.
• JP 2004-269408 and JP 2001-192647 describe methods for chlorine gas drying with sulfuric acid in drying columns with minimization of sulfuric acid losses and recycling of streams of spent sulfuric acid by mixing with highly concentrated fresh sulfuric acid, but without a distillative concentration of used sulfuric acid is described. Furthermore, these two documents do not disclose that the concentrated or dilute sulfuric acid from the process may also be part of the nitrating acid in a nitration reaction.
• Single or double nitrated aromatic compounds selected from the group of nitrobenzene, dinitrobenzene, nitrochlorobenzene, nitrochlorotoluene, nitrotoluene and dinitrotoluene are, with few exceptions, usually prepared by nitration processes in which the starting aromatic compound is selected from the group of benzene, Chlorobenzene and toluene is reacted in a sulfuric acid-catalyzed two-phase reaction with nitric acid to give the desired mono- or di-nitrated aromatic compound.
• process variants such. Isothermal or adiabatic nitration is used. An overview of the various common process and reactor types is described for example in EP-A 0708076.
• the sulfuric acid must be separated from the nitrated product for reuse after the reaction and concentrated by distillation with expenditure of energy.
• concentration of the effluent from the reaction sulfuric acid can, depending on the desired Zielkon- concentration, for example by a multi-stage vacuum distillation as described in US 6,156,288 and DE-A 19 642 328 or by flash evaporation, as described in US 3201201 done.
• Khi- concentration for example by a multi-stage vacuum distillation as described in US 6,156,288 and DE-A 19 642 328 or by flash evaporation, as described in US 3201201 done.
• the sulfuric acid used as a catalyst for reuse after the reaction is also concentrated with high energy expenditure.
• this process removes large quantities of sulfuric acid via the product / wastewater path, which must be replaced by fresh sulfuric acid.
• the sulfuric acid contained in the wastewater of the Chlorher eins- and the nitration process must be neutralized using large amounts of sodium hydroxide solution before the wastewater can be fed to a sewage treatment plant.
• the object of the present invention is therefore to provide a process for the coupled production of chlorine and isocyanates, which makes it possible to work up the dilute sulfuric acid obtained in both processes without high energy costs and investment costs and with the saving of neutralizing agents in a common process so that they both can be attributed to the chlorine production as well as in the nitration reactions, regardless of which method the dilute sulfuric acid was originally obtained.
• nitration of aromatic compounds selected from the group consisting of toluene, halobenzene toluene, benzene and halogenated benzene to the corresponding mono- or di-nitrated aromatic compounds using nitric acid wherein preferably the nitration of each aromatic compound in independent and not with
• the nitration is carried out in the presence of a sulfuric acid with a concentration of 65.0-98.0% by mass of sulfuric acid based on mass fractions of sulfuric acid and water as catalyst, the sulfuric acid being is diluted after nitration and has a concentration which, depending on the amount of sulfuric acid used and the number of nitriding stages, is 0.5 to 25 percentage points lower than the particular sulfuric acid used, ie a concentration of 40-97.5% by weight of sulfuric acid. based on the weight of sulfuric acid and water.
• step b) transferring the dilute sulfuric acid obtained from step a) to a sulfuric acid concentration plant
• step c2) in the case in which the mono- or di-nitrated compound is nitrozole, reaction of the nitrobenzene obtained from step a) with hydrogen to give the corresponding aniline and subsequent reaction of this product with formaldehyde to form the di- and polyamines of the diphenylmethane series,
• step f) recycling of the aqueous dissolved or gaseous hydrogen chloride resulting from the reaction of the amines from step cl) or c2) with phosgene from step d) in step f);
• step d) use of the phosgene obtained from step h) in step d),
• step j) transfer of the dilute sulfuric acid obtained from step g) either into the same sulfuric acid concentration plant of step b) or directly into one or more nitration steps according to step a) and subsequent conversion of these or these Nitrations running, further diluted sulfuric acids in the same sulfuric acid concentration plant according to step b),
• dilute sulfuric acid streams from step b) and g) are combined in the sulfuric acid concentrating plant and increased by one or more vacuum distillation stages to an increased concentration or by removal of partial streams after different
• step k) and subsequent recycling of the concentrated sulfuric acid obtained from step j) either to complete or partial use in step g) and / or step a).
• the process according to the invention is advantageous if the preparation of the chlorine gas according to step f) by the process according to the invention by one or more of the methods selected from the group of NaCl electrolysis, HCl electrolysis by membrane or Diaphragma- methods, HCl electrolysis in Electrolysis cells with oxygen-consuming cathode and catalytic HCl oxidation is carried out with oxygen.
• the process according to the invention is advantageous if the mono- or di-nitrated aromatic compounds are selected from the group consisting of nitrobenzene, dinitrobenzene, nitrochlorobenzene, nitrochlorotoluene, nitrotoluene and dinitrotoluene.
• the process according to the invention is advantageous if the dilute sulfuric acid obtained after process step g) is freed from chlorine and / or HCl residues up to a residual concentration of ⁇ 100 ppm Cl prior to combination in the sulfuric acid concentration plant according to step j).
• the process according to the invention is advantageous if the dilute sulfuric acid obtained after process step g) is freed from chlorine and / or HCl residues up to a residual concentration of ⁇ 10 ppm Cl before combining in the sulfuric acid concentration plant according to step j).
• the process according to the invention is advantageous if either the dilute sulfuric acid obtainable after step a) or only the concentrated sulfuric acid obtainable after step j) of the process according to the invention before being recycled in step k) of the process according to the invention is contaminated by inorganic nitrogen compounds such as nitrosylglycic acid up to a residual concentration of ⁇ 0.3% by weight or by volatile organic Compounds such as dinitrotoluene, nitrobenzene, dinitrobenzene, nitrophenols, nitro cresols, nitrobenzyl alcohols, nitrobenzaldehydes to a residual concentration of ⁇ 50 ppm, or by low-volatile organic compounds such as Hydroxynitrobenzoeklare, nitrobenzoic acids or aliphatic carboxylic acids to a residual concentration of ⁇ 500 ppm or by volatile Sulfur compounds such as SO 2 is released to a residual concentration of ⁇ 30 ppm.
• inorganic nitrogen compounds such as nitrosylglycic acid up
• the process according to the invention is advantageous if toluene is used in step a) and dinitrotoluene is obtained after double nitration in step a), wherein in the first step of the nitration a sulfuric acid having a concentration of 86.0-96.0% by mass of sulfuric acid is used the sum of the mass fractions of sulfuric acid and water is used, which is diluted in the course of the second nitration stage to a concentration of 80.0-85.9% by mass sulfuric acid based on the sum of the mass proportions of sulfuric acid and water, the dinitrotoulol then according to Step cl) is reacted with hydrogen to toluenediamine (TDA), which is then reacted with phosgene according to step d) to toluene diisocyanate (TDI).
• TDA to toluenediamine
• TDI toluene diisocyanate
• the inventive method when the sulfuric acid, which is obtained from the second nitration stage with a concentration of 80.0-85.9% by mass of sulfuric acid based on the mass fractions of sulfuric acid and water, once again in the first nitration stage of the method Step a) is returned and then diluted to a concentration of 70.0-79.9% by mass of sulfuric acid based on the mass fractions sulfuric acid and water, and this sulfuric acid is then passed into the sulfuric acid concentration in accordance with step b).
• the process according to the invention is advantageous if benzene is used in step a) and nitrobenzene is obtained after simple nitration in step a), with sulfuric acid having a concentration of 69.5-72.5% by mass for the nitration, based on the mass fractions of sulfuric acid and water is used, which is diluted in the course of the nitration to a concentration of 66.5-69.4% by mass of sulfuric acid based on the mass fractions sulfuric acid and water, the nitrobenzene is subsequently reacted with hydrogen according to step c2) to aniline, which in turn is reacted with formaldehyde in the presence of an acidic catalyst to give di- and polyamines of the diphenylmethane series, which in turn are subsequently reacted with phosgene in step d) to give the corresponding di- and polyisocyanates of the diphenylmethane series.
• Particularly preferred is the production of chlorine by reaction of HCl gas by gas phase oxidation with oxygen at temperatures in the range of 180 0 C to 500 0 C in a Deacon process or derived from the Deacon process (such as in EP-743277- B1, DE 19734412-A1, DE 19748299-A1, DE 10242400; DE 10244996) to a stationary catalyst comprising at least one elemental or bound metal selected from the group Cu, Ru, Au, Rh, Pd, Pt, Os, Ir, Ag, Re Ce, Bi, Ni, Co, Ga, Fe and Nd where the metals or the metal compounds unsupported or supported on eg metal or semimetal oxides such as alumnium oxides, silicon oxides, titanium oxides, zirconium oxides or tin oxides, on mixed metal oxides, on ceramic Materials may be present on activated carbons, carbon blacks or carbon nanotubes, on metal or semimetal carbides, on metal or semimetal nitrides or on metal or semimetal
• the gaseous hydrogen chloride from the phosgenation process is generally converted into the HCl oxidation process.
• solvent residues such as chlorobenzene or o-dichlorobenzene, chlorinated hydrocarbons, organic and inorganic sulfur or nitrogen compounds or carbon oxides such as CO or CO 2 take place.
• Possible applicable separation or purification operations here are, for example, adsorption, absorption desorption, deep-freezing condensation, compression, pressure distillation or selective oxidation.
• catalytic gas-phase oxidation and work-up of the product gas stream can be described in various variants described in the literature, for example in EP-Bl 743277, US Pat. No. 6,852,667, DE-A 19734412, WO 2005014470, DE-A 10244996, US-A 200411411 and EP-B 767138, be performed
• the nitration process according to step a) contained in the process according to the invention can be used for the preparation of various nitroaromatics selected from the group of nitrobenzene, dinitrobenzene, nitrochlorobenzene, nitrochlorotoluene, nitrotoluene and dinitrotoluene.
• all methods familiar to the person skilled in the art for the respective target product sought are for cyanide-catalyzed nitration, as described for example in EP-A 0708076, can be used.
• the concentration of the acid can be carried out according to all known in the prior art process for the removal of water from sulfuric acid. These are, for example, single-stage or multistage vacuum distillation or flash evaporation, heating with microwaves or electro-membrane techniques. However, the use of single-stage or multistage vacuum distillations and / or flash evaporations is particularly preferred.
• concentrated sulfuric acid is used in the range of 90.0-98.0% by mass of sulfuric acid, based on mass fractions of sulfuric acid and water for chlorine gas drying, and the dilute sulfuric acid in the range of 70.0-90.0% by mass of sulfuric acid Based on mass fractions sulfuric acid and water from the chlorine gas drying in a sulfuric acid aufkon centering unit of a nitration plant, for example for the dinitration of toluene.
• the amount of acid added to the nitration / acid concentration process corresponds in whole or in part to the sulfuric acid losses of the nitration / acid concentration process.
• the sulfuric acid from the chlorine drying process can also be introduced directly into one or more reaction stages of the nitration process and used as a catalyst for the nitration reaction, the resulting dilute sulfuric acid then being fed to an acid concentration.
• the sulfuric acid from the chlorine drying process can also be introduced directly into one or more reaction stages of the nitration process and used as a catalyst for the nitration reaction, the resulting dilute sulfuric acid then being fed to an acid concentration.
• Impurities in the dilute sulfuric acid from the chlorine production process after step g) of the process according to the invention can optionally be separated off before being introduced into a sulfuric acid concentration plant of a nitriding plant or a nitriding process in order to avoid corrosion and chlorine contamination in the nitriding process.
• This purification of the sulfuric acid can be carried out by various methods as described, for example, in DE-A 2 063 592 by adsorption on activated charcoal or as described, for example, in Khorasani et. al., Journal of Bangladesh Academy of Sciences, 1982, 6 (1-2), 205-207, by air stripping.
• Corrosion problems can also be used in the sulfuric acid concentrating plant resistant materials such as special nickel alloys disclosed in JP 2006045610. Preference is given to removal of chlorine residues via stripping.
• the sulfuric acid is freed from chlorine and HCl residue, so that a residual concentration of Cl in the range of ⁇ 1000 ppm, preferably less than 100 ppm, more preferably less than 10 ppm is obtained.
• the dilute sulfuric acid from the chlorine gas drying from step g) and the dilute sulfuric acid from the nitration process according to step b) are combined and processed in a single sulfuric acid concentration plant and the concentrated sulfuric acid is again proportionally incorporated into the nitration process after step a ) and the chlorine drying after step g) or fed to another nitration plant which produces a different aromatic nitro compound than the first nitration plant.
• This particular embodiment of the process allows both chlorine to be dried and dinitrotoluene to be prepared in the first nitriding unit and nitrobenzene in the second nitriding unit with a single sulfuric acid concentrating unit, with the dilute sulfuric acid obtainable from the chlorine drying method, optionally before the concentrating step, for both nitriding units j) can be used as a catalyst in both nitrations.
• This process alternative is advantageous when the diluted amount of sulfuric acid from the chlorine drying exceeds the sulfuric acid losses of one of the nitrations. This in turn reduces the use of fresh sulfuric acid in the chlorine drying step g) by the recycled fraction.
• the sulfuric acid can be concentrated in several stages in order to provide the respectively suitable sulfuric acid concentration in the respective required amounts.
• a sulfuric acid concentration of 86-91% by mass of sulfuric acid relative to mass fractions of sulfuric acid and water may be required while a higher concentration of 96.0-98, which is advantageous for chlorine drying, 0% by mass of sulfuric acid based on mass fractions of sulfuric acid and water, is needed.
• the process according to the invention can be carried out in such a way that in the sulfuric acid concentrating plant the entire stream is concentrated to the concentration required for the nitration and only the partial stream required for the chlorine drying is concentrated further in an additional distillation step. In this way, the goal of reducing the investment costs is achieved in this case, too.
• Purification steps may be used to remove any components which may interfere with the chlorine production process, such as organic nitro compounds, benzoic acids, nitrous gases or nitrosylsulphuric acid prior to recycle of sulfuric acid from a common acid concentration stage to the chlorine gas drying. This can be done by means of adsorption or stripping.
• the process according to the invention is advantageous when toluene or benzene are used as aromatic starting compound.
• dinitro-toluene can be obtained according to step a), which are subsequently reacted with hydrogen to form toluenediamine (TDA) in step c1) according to the processes known from the prior art and then after known in the art with phosgene to tolylene diisocyanate (TDI) according to step d) can be implemented.
• TDA toluenediamine
• TDI phosgene to tolylene diisocyanate
• a sulfuric acid concentration in the range from 86.0 to 96.0% by mass of sulfuric acid, based on mass fractions of sulfuric acid and water is usually employed prior to adding nitric acid.
• This sulfuric acid is then diluted by reaction water formed during the nitration to a concentration of 80.0-85.9 parts by mass of sulfuric acid based on mass fractions of sulfuric acid and water.
• the dilute sulfuric acid obtained from this second nitration stage with the concentration range of 80.0-85.9% by mass of sulfuric acid based on mass fractions of sulfuric acid and water is then used as feed sulfuric acid for the first nitration stage of toluene to mononitrotoluene, during which first nitriding this sulfuric acid used to a concentration of 70.0-79.9% by mass sulfuric acid based on the mass fractions sulfuric acid and water, is diluted.
• nitrobenzene is obtained by simple nitration after step a) of the process according to the invention, which is then reacted with hydrogen to form aniline according to the process known from the prior art in step c2) of the process according to the invention, which in turn is reacted with formaldehyde in Presence of an acidic catalyst to di- and polyamines of the diphenylmethane series according to step c2) is reacted.
• the di- and polyamines can then be reacted according to the processes known from the prior art with phosgene to the corresponding di- and polyisocyanates of the diphenylmethane series according to step d).
• nitric acid which has a concentration in the range of 69.5-72.5% by mass of sulfuric acid based on mass fractions of sulfuric acid and water.
• the nitrate Sulfuric acid obtained a concentration of 66.5-69.4% by mass of sulfuric acid based on mass fractions of sulfuric acid and water.
• Chlorine obtained by the process according to the invention can then be converted by the processes known from the prior art with carbon monoxide to give phosgene according to step h) which is obtainable for the preparation of TDI or MDI from TDA or MDA from step cl) or step c2) , can be used.
• the hydrogen chloride which is formed in turn during the phosgenation of TDA and MDA can then be reacted according to step i) by the methods known from the prior art to give chlorine in accordance with step f).

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• 2006
  • 2006-05-13 DE DE102006022447A patent/DE102006022447A1/de not_active Withdrawn
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  • 2007-05-03 WO PCT/EP2007/003892 patent/WO2007131638A1/de not_active Ceased
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