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
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
  • B01J19/02—Apparatus characterised by being constructed of material selected for its chemically-resistant properties
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J8/00—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes
  • B01J8/02—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with stationary particles, e.g. in fixed beds
  • B01J8/06—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with stationary particles, e.g. in fixed beds in tube reactors; the solid particles being arranged in tubes
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J8/00—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes
  • B01J8/18—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
  • F28F21/00—Constructions of heat-exchange apparatus characterised by the selection of particular materials
  • F28F21/08—Constructions of heat-exchange apparatus characterised by the selection of particular materials of metal
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
  • B01J2219/00049—Controlling or regulating processes
  • B01J2219/00245—Avoiding undesirable reactions or side-effects
  • B01J2219/00247—Fouling of the reactor or the process equipment
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
  • B01J2219/02—Apparatus characterised by their chemically-resistant properties
  • B01J2219/0204—Apparatus characterised by their chemically-resistant properties comprising coatings on the surfaces in direct contact with the reactive components
  • B01J2219/0236—Metal based

Definitions

• the invention is based on a process for carrying out an optionally catalyst-supported hydrogen chloride oxidation process a) by means of oxygen.
• the process comprises the b) one-stage or multi-stage cooling of the process gases and c) separation of unreacted hydrogen chloride and reaction water from the process gas, d) drying of the product gases and e) separation of chlorine from the mixture.
• the invention relates to the lining of the system parts contacted by the reaction mixture.
• a major technical problem with Deacon processes is the selection of the materials to be used in the different plant zones, since the substances involved in the reaction, in particular under elevated pressure, corrosively attack product-contacting parts of the plants.
• the object of the invention is to produce chlorine by HCl oxidation and to ensure long-term operation by using specially adapted materials and to avoid interruption of operation due to premature corrosion.
• the invention by means of which the above object is achieved, is a process for carrying out an optionally catalyst-supported hydrogen chloride oxidation process a) by means of oxygen, b) one-stage or multi-stage cooling of the process gases and c) removal of unreacted hydrogen chloride and reaction water from the process gas d) drying of the product gases and e) separation of chlorine from the mixture, characterized in that
• the hydrogen chloride oxidation a) is carried out in a reactor whose construction parts touched by the reaction mixture are made of nickel or a nickel-containing alloy, the proportion of nickel being at least 60% by weight.
• Nickel alloys with major proportions of independently: iron, chromium and molybdenum are preferred.
• the nickel content is more preferably at least 99.5% by weight.
• materials from the group: Hastelloy ® C-types, Hastelloy ® B types, Inconel ® 600, Inconel 625 ® are particularly preferred.
• the structural parts do not include functional parts such as catalyst material and support or measuring installations.
• the cooling b) of the process gases in a first heat exchanger starting from the reactor outlet temperature to a temperature of 140 to 250 0 C, preferably from 160 to 220 0 C, carried out, wherein the contacted by the reaction mixture construction parts of the heat exchanger Nickel or a nickel-containing alloy, wherein the proportion of nickel is at least 60 wt .-%.
• Nickel alloys with major proportions of independently: iron, chromium and molybdenum are preferred.
• materials are selected from the series: Hastelloy ® C-types, Hastelloy ® B types, Inconel ® 600, Inconel 625 ® are particularly preferred.
• a method which is characterized in that the cooling b) of the process gases in a second heat exchanger, starting from the outlet temperature of the first heat exchanger to a temperature greater than or equal to 100 0 C is carried out further, and wherein at least the Reaction mixture contacted structural parts of the second heat exchanger of a material selected from the series: steel / fluoropolymers (PFA, PVDF, PTFE) and ceramics, in particular silicon carbide or silicon nitride, in particular as a pipe material in each case preferably as a tube in tube sheets made of coated steel.
• the second heat exchanger is designed as a shell-and-tube heat exchanger in which the shell is made of fluoropolymer-coated steel and the tubes of the tube bundle are made of a ceramic material, preferably silicon carbide or silicon nitride.
• Very particularly preferred is a method, characterized in that the second heat exchanger is operated so that the process gas to be cooled is fed into the jacket of the heat exchanger and the cooling medium is passed through the tubes of the heat exchanger.
• the cooling b) of the process gases is further carried out in a third heat exchanger, starting from the outlet temperature of the second heat exchanger to the condensation of liquid hydrochloric acid, in particular to a temperature greater than or equal to 5 ° C, wherein at least touched by the reaction mixture Structural parts of the third heat exchanger of a material selected from the series: fluoropolymers (in particular tetrafluoroethylene-perfluoroalkoxy-vinyl ether copolymer (PFA), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE) or polyvinylidene fluoride tetrafluoroethylene (ETFE)) and ceramics, in particular silicon carbide or silicon nitride, in particular each made as a tube in tube sheets of coated steel.
• fluoropolymers in particular tetrafluoroethylene-perfluoroalkoxy-vinyl ether copolymer (PFA), polyvinylidene
• the process gas is cooled in the cooling b) to less than or equal to 100 0 C and then introduced to remove c) in an HCl absorption, which with water or an aqueous solution of hydrogen chloride of a concentration of bis 30% by weight, and wherein at least the structural parts of the HCl absorption system contacted by the reaction mixture are selected from the group: enamelled steel, graphite, silicon carbide, glass fiber reinforced plastic (GRP), in particular based on polyester resins or polyvinyl ester resins, coated steel or fluoropolymer coated and / or lined steel, in particular steel with a lining of PTFE, optionally additionally coated with PFA or ETFE, are made.
• GRP glass fiber reinforced plastic
• the drying d) of the particular largely HCl-free chlorine and oxygen mixture is preferably in desiccators by means of conc.
• Sulfuric acid carried out in which at least the contact with the reaction mixture structural parts of the drying apparatus of a material selected from the series: Steel type Hastelloy C ® 2000 or Hastelloy ® B, Si-containing non-stainless steels or graphite are made.
• the separation e) of the chlorine from the chlorine and oxygen mixture is particularly preferably carried out in separation apparatuses in which at least the structural parts of the separation apparatuses contacted by the gas mixture are made of carbon steel.
• liquid phase of chlorine obtained from the separation e) of the chlorine from the chlorine and oxygen mixture is evaporated again in an evaporation apparatus in which at least the construction parts of the evaporation apparatus touched by the product Carbon steel are made.
• the hydrogen chloride of the HCl oxidation process is derived from an isocyanate production process and the purified chlorine is recycled to the isocyanate production process.
• An alternative preferred method is characterized in that the hydrogen chloride of the HCl oxidation process comes from a chlorination process of organic compounds of chlorinated aromatics and the purified chlorine is recycled to the chlorination process.
• the new process is particularly preferably operated so that the HCl oxidation process a) takes place at a pressure of 3 to 30 bar.
• a preferred method is characterized in that the HCl oxidation process is a deacon process, i. a catalyzed gas phase oxidation of HCl by means of oxygen.
• phosgene is prepared by reacting chlorine with carbon monoxide.
• the synthesis of phosgene is well known and is, for example, in Ullmann's Encyclopedia of Industrial Chemistry, 3rd Edition, Volume 13, page 494-500 shown.
• phosgene is produced predominantly by reaction of carbon monoxide with chlorine, preferably on activated carbon as a catalyst.
• the highly exothermic gas phase reaction is typically carried out at a temperature of at least 250 0 C to a maximum of 600 0 C usually in tube bundle reactors.
• the reaction heat can be conducted in different ways, for example by a liquid heat exchange medium, as described for example in WO 03/072237 A1, or by evaporative cooling via a secondary cooling circuit with simultaneous use of the heat of reaction for steam generation, as disclosed, for example, in US Pat. No. 4,764,308 ,
• At least one isocyanate is formed by reaction with at least one organic amine or a mixture of two or more amines in a next process step.
• This second process step is also referred to below as phosgenation.
• the reaction takes place with the formation of hydrogen chloride as a by-product, which is obtained as a mixture with the isocyanate.
• isocyanates are also known in principle from the prior art, wherein phosgene is usually used in a stoichiometric excess, based on the amine. Usually, the phosgenation takes place according to the liquid phase, wherein the phosgene and the amine may be dissolved in a solvent.
• Preferred solvents for the phosgenation are chlorinated aromatic hydrocarbons, such as chlorobenzene, o-dichlorobenzene, p-dichlorobenzene, trichlorobenzenes, the corresponding chlorotoluenes or chloroxylenes, chloroethylbenzene, monochlorodiphenyl, ⁇ - or ⁇ -naphthyl chloride, ethyl benzoate, dialkyl phthalate, diisodiethyl phthalate , Toluene and xylenes.
• suitable solvents are known in principle from the prior art. As also known in the art, e.g.
• WO 96/16028 can act as a solvent for phosgene as well as the formed isocyanate itself.
• the phosgenation especially of suitable aromatic and aliphatic diamines, takes place in the gas phase, i. above the boiling point of the amine, instead.
• the gas phase phosgenation is e.g. described in EP 570 799 Al. Advantages of this method over the otherwise usual remplissigphasenphos- gentechnik lie in the energy savings, due to the minimization of a complex solvent and phosgene cycle.
• Suitable organic amines are in principle all primary amines having one or more primary amino groups which can react with phosgene to form one or more isocyanates having one or more isocyanate groups.
• the amines have at least one, preferably two, or optionally three or more primary amino groups.
• suitable organic primary amines are aliphatic, cycloaliphatic, aliphatic-aromatic, aromatic amines, di- and / or polyamines, such as aniline, halogen-substituted phenylamines, for example 4-chlorophenylamine, 1,6-diaminohexane, 1-amino-3 , 3,5-trimethyl-5-amino-cyclohexane, 2,4-, 2,6-diaminotoluene or mixtures thereof, 4,4'-, 2,4'- or 2,2'-diphenylmethanediamine or mixtures thereof, such as also higher molecular weight isomeric, oligomeric or polymeric derivatives of said amines and polyamines.
• aniline halogen-substituted phenylamines
• halogen-substituted phenylamines for example 4-chlorophenylamine, 1,6-diaminohexane, 1-amin
• Preferred amines for the present invention are the amines of the diphenylmethanediamine series (monomeric, oligomeric and polymeric amines), 2,4-, 2,6-diaminotoluene, isophoronediamine and hexamethylenediamine.
• MDI diisocyanatodiphenylmethane
• TDI toluene diisocyanate
• HDI hexamethylene diisocyanate
• IPDI isophorone diisocyanate
• the amines can be reacted with phosgene in a one-step or two-step or possibly multi-step reaction. In this case, a continuous as well as discontinuous operation is possible.
• the reaction is carried out above the boiling point of the amine preferably within a mean contact time of 0.5 to 5 s and at a temperature of 200 to 600 0 C.
• the phosgenation in the liquid phase is usually carried out at a temperature of 20 to 240 0 C and a pressure of 1 to about 50 bar.
• the phosgenation in the liquid phase can be carried out in one or more stages, wherein phosgene can be used in stoichiometric excess.
• the amine solution and the phosgene solution are combined via a static mixing element and then passed, for example, from bottom to top through one or more reaction towers, where the mixture reacts to the desired isocyanate.
• reaction vessels with stirring device can also be used.
• special dynamic mixing elements can also be used. Suitable static and dynamic mixing elements are basically known from the prior art.
• continuous liquid phase isocyanate production is carried out in two stages on an industrial scale.
• the first stage generally at a temperature of at most 220 0 C, preferably not more than 16O 0 C from amine and phosgene, the carbamoyl chloride and amine and split off hydrogen chloride amine hydrochloride formed.
• This first stage is highly exothermic.
• both the carbamoyl chloride is cleaved to isocyanate and hydrogen chloride, and the amine hydrochloride is converted to the carbamoyl chloride.
• the second stage is usually carried out at a temperature of at least 90 ° C., preferably from 100 to 240 ° C.
• the separation of the isocyanates formed during the phosgenation takes place in a third step. This is done by firstly mixing the reaction mixture of the phosgenation into a liquid and a gaseous product stream in a manner which is fundamental to the person skilled in the art. Lich known manner is separated.
• the liquid product stream contains essentially the isocyanate or isocyanate mixture, the solvent and a small amount of unreacted phosgene.
• the gaseous product stream consists essentially of hydrogen chloride gas, stoichiometrically excess phosgene, and minor amounts of solvents and inert gases, such as nitrogen and carbon monoxide.
• liquid stream is then subjected to a work-up, preferably a work-up by distillation, successively phosgene and the solvent for the phosgenation are separated.
• a work-up preferably a work-up by distillation
• successively phosgene and the solvent for the phosgenation are separated.
• the hydrogen chloride obtained in the reaction of phosgene with an organic amine generally contains organic minor components which can interfere with either thermal catalyzed or non-thermal activated HCl oxidation.
• organic constituents include, for example, the solvents used in the preparation of isocyanates, such as chlorobenzene, o-dichlorobenzene or p-dichlorobenzene.
• the separation of the hydrogen chloride is preferably carried out initially by phosgene is separated from the gaseous product stream.
• the separation of the phosgene is achieved by liquefaction of phosgene, for example on one or more capacitors connected in series.
• the liquefaction is preferably carried out at a temperature in the range of -15 to -40 0 C, depending on the solvent used. By this freezing also parts of the solvent residues can be removed from the gaseous product stream.
• the phosgene may be washed out of the gas stream in one or more stages with a cold solvent or solvent-phosgene mixture.
• Suitable solvents for this purpose for example, the solvents used in the phosgenation chlorobenzene and o-dichlorobenzene are.
• the temperature of the solvent or the solvent-phosgene mixture for this purpose is in the range of -15 to -46 ° C.
• the separated from the gaseous product stream phosgene can be fed back to the phosgenation.
• the hydrogen chloride obtained after separation of the phosgene and a portion of the solvent residue may contain, in addition to the inert gases such as nitrogen and carbon monoxide, 0.1 to 1% by weight of solvent and 0.1 to 2% by weight of phosgene.
• a purification of the hydrogen chloride to reduce the proportion of traces of solvent can be done, for example by freezing, by depending on the physical properties of the solvent, the hydrogen chloride is passed, for example, by one or more cold traps.
• the optionally provided purification of the hydrogen chloride two series-connected heat exchanger wherein the separated off solvent is frozen out in response to the fixed point, for example at -40 0 C to be flowed through by the stream of hydrogen chloride.
• the heat exchangers are preferably operated alternately, with the gas stream thawing out the previously frozen-out solvent in the first throughflowed heat exchanger.
• the solvent can be used again for the preparation of a phosgene solution.
• the gas is preferably cooled below the fixed point of the solvent, so that this crystallized out.
• the gas flow and the coolant flow are switched so that the function of the heat exchanger reverses.
• the hydrogen chloride-containing gas stream can be depleted in this way to preferably not more than 500 ppm, particularly preferably not more than 50 ppm, very particularly preferably not more than 20 ppm of solvent content.
• the purification of the hydrogen chloride can preferably be carried out in two series-connected heat exchangers, for example according to US Pat. No. 6,719,957.
• the hydrogen chloride is preferably compressed to a pressure of 5 to 20 bar, preferably 10 to 15 bar, compressed and the compressed gaseous hydrogen chloride at a temperature of 20 to 60 ° C, preferably 30 to 50 0 C, fed to a first heat exchanger.
• the hydrogen chloride with a cold chlorine hydrogen a temperature of -10 to -30 0 C, which comes from a second heat exchanger, cooled. This condense organic components that can be supplied to a disposal or recycling.
• the passed into the first heat exchanger hydrogen chloride leaves this with a temperature of -20 to 0 0 C and is cooled in the second heat exchanger to a temperature of -10 to -30 0 C.
• the resulting in the second heat exchanger condensate consists of other organic components and small amounts of hydrogen chloride.
• the condensate running out of the second heat exchanger is fed to a separation and evaporator unit. This may be, for example, a distillation column in which the hydrogen chloride is expelled from the condensate and returned to the second heat exchanger. It is also possible to return the expelled hydrogen chloride in the first heat exchanger.
• the cooled in the second heat exchanger and freed of organic hydrogen chloride is passed at a temperature of -10 to - 30 0 C in the first heat exchanger. After heating to 10 to 30 0 C leaves the liberated from organic components hydrogen chloride, the first heat exchanger.
• the optionally provided purification of the hydrogen chloride is carried out by organic impurities, such as solvent residues, of active compounds. coal by adsorption.
• organic impurities such as solvent residues, of active compounds. coal by adsorption.
• the hydrogen chloride is passed after removal of excess phosgene at a pressure difference of 0 to 5 bar, preferably from 0.2 to 2 bar, over or through an activated carbon bed.
• the flow rate and residence time are adjusted in a manner known to those skilled in the content of impurities.
• the adsorption of organic contaminants is also possible on other suitable adsorbents, for example on zeolites.
• a distillation of the hydrogen chloride may be provided for the optionally intended purification of the hydrogen chloride from the phosgenation. This takes place after condensation of the gaseous hydrogen chloride from the phosgenation.
• the purified hydrogen chloride is removed as the top product of the distillation, wherein the distillation under known to those skilled, for such a distillation customary conditions of pressure, temperature u.a. he follows.
• the hydrogen chloride separated off and optionally purified according to the above-described process can then be supplied to the HCl oxidation with oxygen.
• the catalytic process known as the Deacon process is used.
• hydrogen chloride is oxidized with oxygen in an exothermic equilibrium reaction to chlorine, whereby water vapor is obtained.
• the reaction temperature is usually 150 to 500 0 C, the usual reaction pressure is 1 to 25 bar. Since it is an equilibrium reaction, it is expedient to work at the lowest possible temperatures at which the catalyst still has sufficient activity.
• oxygen in excess of stoichiometric amounts of hydrogen chloride. For example, a two- to four-fold excess of oxygen is customary. Since no loss of selectivity is to be feared, it may be economically advantageous to work at relatively high pressure and correspondingly at a residence time which is longer than normal pressure.
• Suitable preferred catalysts for the Deacon process include ruthenium oxide, ruthenium chloride or other ruthenium compounds supported on silica, alumina, titania or zirconia. Suitable catalysts can be obtained, for example, by applying ruthenium chloride to the support and then drying or drying and calcining. Suitable catalysts may, in addition to or instead of a ruthenium compound, also contain compounds of other noble metals, for example gold, palladium, platinum, osmium, iridium, silver, copper or rhenium. Suitable catalysts may further contain chromium (i ⁇ ) oxide.
• the catalytic hydrogen chloride oxidation can be adiabatic or preferably isothermal or approximately isothermal, batchwise, but preferably continuously or as a fixed bed process, preferably as a fixed bed process, particularly preferably in tube bundle reactors to heterogeneous catalysts at a reactor temperature of 180 to 500 0 C, preferably 200 to 400 0th C, more preferably 220 to 350 0 C and a pressure of 1 to 25 bar (1000 to 25000 hPa), preferably 1, 2 to 20 bar, more preferably 1, 5 to 17 bar and in particular 2.0 to 15 bar be performed.
• a reactor temperature 180 to 500 0 C, preferably 200 to 400 0th C, more preferably 220 to 350 0 C and a pressure of 1 to 25 bar (1000 to 25000 hPa), preferably 1, 2 to 20 bar, more preferably 1, 5 to 17 bar and in particular 2.0 to 15 bar be performed.
• Typical reactors in which the catalytic hydrogen chloride oxidation is carried out are fixed bed or fluidized bed reactors.
• the catalytic hydrogen chloride oxidation can preferably also be carried out in several stages.
• a further preferred embodiment of a device suitable for the method consists in using a structured catalyst bed in which the catalyst activity increases in the flow direction.
• Such structuring of the catalyst bed can be carried out by different impregnation of the catalyst support with active material or by different dilution of the catalyst with an inert material.
• an inert material for example, rings, cylinders or balls of titanium dioxide, zirconium dioxide or mixtures thereof, alumina, steatite, ceramic, glass, graphite or stainless steel can be used.
• the inert material should preferably have similar external dimensions.
• Suitable shaped catalyst bodies are shaped bodies with any desired shapes, preference being given to tablets, rings, cylinders, stars, carriage wheels or spheres, particular preference being given to rings, cylinders or star strands as molds.
• Ruthenium compounds or copper compounds on support materials are particularly suitable as heterogeneous catalysts, preference being given to optionally doped ruthenium catalysts.
• suitable carrier materials are silicon dioxide, graphite, rutile or anatase titanium dioxide, zirconium dioxide, aluminum oxide or mixtures thereof, preferably titanium dioxide, zirconium dioxide, aluminum oxide or mixtures thereof, particularly preferably g- or d-aluminum oxide or mixtures thereof.
• the copper or ruthenium catalysts for example, by impregnating the support material with aqueous solutions of CuCl or RuCl ⁇ 3 and optionally a promoter for doping, preferably their chlorides in the form can be obtained.
• the shaping of the catalyst can take place after or preferably before the impregnation of the support material.
• the catalysts are suitable as promoters alkali metals such as lithium, sodium, potassium, rubidium and cesium, preferably lithium, sodium and potassium, more preferably potassium, alkaline earth metals such as magnesium, calcium, strontium and barium, preferably magnesium and calcium, particularly preferably magnesium, Rare earth metals such as scandium, yttrium, lanthanum, cerium, praseodymium and neodymium, preferably scandium, yttrium, lanthanum and cerium, more preferably lanthanum and cerium, or mixtures thereof.
• alkali metals such as lithium, sodium, potassium, rubidium and cesium, preferably lithium, sodium and potassium, more preferably potassium, alkaline earth metals such as magnesium, calcium, strontium and barium, preferably magnesium and calcium, particularly preferably magnesium, Rare earth metals such as scandium, yttrium, lanthanum, cerium, praseodymium and neodymium, preferably scandium, yt
• the moldings can then be dried at a temperature of 100 to 400 0 C, preferably 100 to 300 0 C, for example, under a nitrogen, argon or air atmosphere and optionally calcined.
• the moldings are first dried at 100 to 150 0 C and then calcined at 200 to 400 0 C.
• the conversion of hydrogen chloride in a single pass may preferably be limited to 15 to 90%, preferably 40 to 85%, particularly preferably 50 to 70%. After conversion, unreacted hydrogen chloride can be partly or completely recycled to the catalytic hydrogen chloride oxidation.
• the volume ratio of hydrogen chloride to oxygen at the reactor inlet is preferably 1: 1 to 20: 1, particularly preferably 2: 1 to 8: 1, particularly preferably 2: 1 to 5: 1.
• the heat of reaction of the catalytic hydrogen chloride oxidation can be used advantageously for the production of high-pressure steam.
• This can be used for the operation of a phosgenation reactor and / or distillation columns, in particular of isocyanate distillation columns.
• This process gas stream is passed to a first heat exchanger whose product parts of the construction parts made of nickel (purity 99.5 wt .-% Ni) are made.
• the material is partly present as a lining and partly in solid form.
• the process gas is cooled to 250 0 C.
• a second heat exchanger whose product-contacting structural parts are made of silicon carbide. Furthermore, ceramic tubes (made of silicon carbide) are provided, which are connected to PTFE-lined tube plates and constructed as heat exchangers.
• the process gas stream is cooled to 100 0 C, the pressure is 3.15 bar.
• This process gas is passed to an HCl absorption plant to remove hydrogen chloride and water.
• This is structured as follows: HCl and H 2 O in the crude gas are removed in an absorption column. For this purpose, the raw gas is introduced above the sump. At the top of the column, water is given up. HCl and H 2 O are recovered as 25 wt .-% hydrochloric acid in the bottom, the purified crude gas at the top of the column contains O 2 and C 12 and is saturated with water vapor.
• hydrochloric acid is pumped from the bottom to the top of the column.
• the circulated hydrochloric acid is cooled by means of a heat exchanger.
• the wetted parts of the hydrogen chloride absorption system consist of plastic-lined (PVDF) components.
• the hydrogen chloride absorption can be taken from a gas stream having the following composition:
• the temperature is 25 ° C, the pressure 3.0 bar.
• this process gas is dried with sulfuric acid.
• the drying takes place by means of a drying column.
• the saturated with water vapor Cl 2 / O 2 gas mixture is passed above the bottom in the column.
• 98 wt .-% sulfuric acid is abandoned.
• the mass transport of the water vapor into the sulfuric acid takes place.
• the sulfuric acid diluted to about 75-78% by weight is discharged from the bottom of the column.
• the product-contacting construction parts of the drying device are constructed of carbon steel (carbon steel).
• This dried process gas stream is compressed to 11, 9 bar and the chlorine gas therein liquefied.
• the gas is recuperatively cooled to -45 0 C.
• Inert (O 2 , CO 2 ) are stripped off in a distillation column. At the bottom, liquid chlorine is recovered. Chlorine is then evaporated and thereby cools the compressed Cl 2 / O 2 gas mixture.

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• 2006
  • 2006-05-23 DE DE102006024515A patent/DE102006024515A1/de not_active Withdrawn
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