EP1951650A1 - Procede de production d'acroleine, d'acide acrylique ou d'un melange de ceux-ci a partir de propane - Google Patents

Procede de production d'acroleine, d'acide acrylique ou d'un melange de ceux-ci a partir de propane

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Publication number
EP1951650A1
EP1951650A1 EP06778269A EP06778269A EP1951650A1 EP 1951650 A1 EP1951650 A1 EP 1951650A1 EP 06778269 A EP06778269 A EP 06778269A EP 06778269 A EP06778269 A EP 06778269A EP 1951650 A1 EP1951650 A1 EP 1951650A1
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EP
European Patent Office
Prior art keywords
gas
reaction zone
reaction
propane
volume
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Application number
EP06778269A
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German (de)
English (en)
Inventor
Otto Machhammer
Klaus Joachim MÜLLER-ENGEL
Martin Dieterle
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BASF SE
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BASF SE
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Publication date
Priority claimed from DE102005056377A external-priority patent/DE102005056377A1/de
Priority claimed from DE200510057197 external-priority patent/DE102005057197A1/de
Application filed by BASF SE filed Critical BASF SE
Publication of EP1951650A1 publication Critical patent/EP1951650A1/fr
Withdrawn legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C45/00—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds
    • C07C45/27—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by oxidation
    • C07C45/32—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by oxidation with molecular oxygen
    • C07C45/33—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by oxidation with molecular oxygen of CHx-moieties
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C45/00—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds
    • C07C45/27—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by oxidation
    • C07C45/32—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by oxidation with molecular oxygen
    • C07C45/33—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by oxidation with molecular oxygen of CHx-moieties
    • C07C45/34—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by oxidation with molecular oxygen of CHx-moieties in unsaturated compounds
    • C07C45/35—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by oxidation with molecular oxygen of CHx-moieties in unsaturated compounds in propene or isobutene
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
    • C07C51/16—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation
    • C07C51/21—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen
    • C07C51/215—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen of saturated hydrocarbyl groups
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
    • C07C51/16—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation
    • C07C51/21—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen
    • C07C51/25—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen of unsaturated compounds containing no six-membered aromatic ring
    • C07C51/252—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen of unsaturated compounds containing no six-membered aromatic ring of propene, butenes, acrolein or methacrolein

Definitions

  • the present invention relates to a process for the preparation of acrolein, or acrylic acid, or their mixture of propane, wherein
  • reaction gas A A) - a first reaction zone A with the formation of a reaction gas A at least two gaseous, propane-containing feed streams, of which at least one fresh propane contains, in the reaction zone A, the reaction gas A through at least one catalyst bed leads, in which by partial heterogeneously catalyzed dehydrogenation of the propane molecular hydrogen and propylene are formed, which supplies molecular oxygen to reaction zone A, which oxidizes molecular hydrogen present in reaction zone A in reaction gas A to water vapor, and removes product gas A from reaction zone A, which contains molecular hydrogen, water vapor, propylene and propane,
  • reaction zone B product gas B leads and separates from the same in a first separation zone I contained target product, water and heavier than water boiling secondary components to leave a residual gas I, the unreacted propane, carbon dioxide, molecular hydrogen, lighter than water contains boiling secondary components and in the reaction zone B optionally unreacted propylene and optionally unreacted molecular oxygen,
  • Acrylic acid is an important basic chemical which is used, inter alia, as a monomer for the preparation of polymers which are used, for example, in disperse distribution in an aqueous medium as binder.
  • Another field of application of acrylic acid polymers are superabsorbents in the hygiene sector and other fields of application.
  • Acrolein is a significant intermediate, for example, for the preparation of glutaric dialdehyde, methionine, 1,3-propanediol, 3-picoiin, folic acid and acrylic acid.
  • the heat of reaction is different from the oxydehydrogenation endothermic (as a subsequent step, an exothermic hydrogen combustion in the reaction zone A be included) and is formed at the at least intermediate free molecular hydrogen This usually requires different reaction conditions and different catalysts than for oxydehydrogenation.
  • reaction zone A proceeds in the reaction zone A as necessary under ⁇ -development. Since the molecular hydrogen thus developed in reaction zone A is not a reactant of the target reaction which takes place in reaction zone B, it does not naturally absorb itself in the relevant cycle gas process. It is therefore the decision of the operator to determine where and in what form the molecular hydrogen formed in the reaction zone A (optionally added to the reaction zone A) should be discharged again in the described cycle gas process (ideally, in the reaction zone A) formed propylene molecule, a hydrogen molecule formed).
  • the prior art also proposes a process variable in which the total amount of molecular hydrogen which is formed in the reaction zone A is also carried as such until after the separation zone I. It is then recommended to separate off the propane and propylene contained in the residual gas I from all other constituents of the residual gas I, including the molecular hydrogen, and to recirculate only the thus separated stream of C 3 -hydrocarbon hydrocarbons into the reaction zone A.
  • a disadvantage of this process variant is that it involves the necessity of initially converting the total amount of C 3 -hydrocarbons into the condensed phase to the full extent and then returning them from the same to the gas phase.
  • DE-A 33 13 573 includes the possibility of completely oxidizing the molecular hydrogen formed in the reaction zone A to water in the reaction zone A by means of added molecular oxygen, and either at least part of the water formed before the reaction zone B to condense and separate in this way, or to carry the same in the entire amount formed in the reaction zone B. Both are disadvantageous. On the one hand Condensation of water requires cooling of the product gas A to temperatures well below the temperatures required in the reaction zone B.
  • this temperature reduction must be carried out from a very high temperature level, since combustion of the molecular hydrogen provides about twice the amount of heat that is consumed for its formation as part of the dehydrogenation.
  • the object of the present invention was to provide a method according to the preamble of the present specification which at most still has the described disadvantages in a reduced form.
  • reaction zone A A) - a first reaction zone A with the formation of a reaction gas A at least two gaseous feed streams containing propane, of which contains at least one fresh propane, in the reaction zone A, the reaction gas A through at least one catalyst bed leads, in which by partial heterogeneously catalyzed dehydrogenation of the propane molecular hydrogen and propylene are formed, - the Reaktäonszone A molecular oxygen supplies, which oxidizes in the reaction zone A contained in the reaction gas A molecular hydrogen to water vapor, and the reaction zone A takes product gas A containing molecular hydrogen, water vapor, propylene and propane,
  • reaction zone B in a reaction zone B, the product gas A withdrawn from the reaction zone A with supply of molecular oxygen for charging at least one O xidationsreaktors with a molecular hydrogen, water vapor, propane, propylene and molecular oxygen containing reaction gas B used and contained in the same propylene heterogeneous catalyzed partial gas phase oxidation to Acroiei ⁇ , or acrylic acid, or their mixture as the target product, unreacted propane, molecular hydrogen, water vapor, by-product carbon dioxide and other lighter and heavier than water-boiling secondary components containing product gas B subjects,
  • Water-boiling secondary components leaving a residual gas I separated containing unreacted propane, carbon dioxide, molecular hydrogen, lighter than water-boiling secondary components and in the reaction zone B optionally unreacted propylene and optionally unreacted molecular oxygen,
  • Residual gas I washes out carbon dioxide which may optionally still be condensed in residual gas I, - omits a partial amount of residual gas I as aftertreatment measure 2, optionally as aftertreatment measure 3 in a third separation zone IM via a separating membrane contained in residual gas I molecular hydrogen and optionally as a post-treatment measure 4 chemically reduced molecular oxygen contained in residual gas I,
  • an amount M of molecular hydrogen is oxidized to water vapor which is at least 5 mol% but not more than 95 mol% of the total amount of molecular hydrogen produced in the reaction zone A and optionally fed to the reaction zone A.
  • the amount M (always in a corresponding manner) is preferably at least 10 mol%, but not more than 90 mol%. More preferably, the amount of M is at least 15 mol% but not more than 85 mol%. Even better, the amount of IVI is at least 20 mol%, but not more than 80 mol%. Most preferably, the amount M is at least 25 mol%, but not more than 75 mol%. More preferably, the amount M is at least 30 mol% and at most 70 mol%.
  • an amount M of at least 35 mol% % and at most 65 mol%. More preferably, the amount M is at least 40 mol% but not more than 60 mol%. Most preferably, the amount M is at least 45 mol%, and not more than 55 mol% M 50 mol% is quite particular in the present invention advantageous.
  • a significant advantage of the procedure according to the invention is then that the propane remains predominantly in the gaseous state of matter in the course of its entire circulation, that is, the condensed liquid phase does not have to be transferred. This is advantageous not least because propane is a comparatively non-polar molecule whose condensation is comparatively complicated
  • reaction gas B necessarily contains molecular hydrogen in an amount limited according to the invention.
  • the reaction gas B necessarily contains molecular hydrogen in an amount limited according to the invention.
  • the advantageous property that it behaves chemically inert in the reaction zone B. That is, at least 95 mol%, usually even at least 97 mol% or at least 99 mol% of the molecular hydrogen fed to the reaction zone B remains chemically unchanged when passing through the reaction zone B.
  • fresh propane is understood to mean propane which has not yet participated in dehydrogenation in reaction zone A. As a rule, it is used as a constituent of crude propane (which is preferably the specification according to US Pat
  • a feed of fresh propane exclusively into the reaction zone A preferably occurs as a constituent of the feed gas mixture for the reaction zone A.
  • partial quantities of the fresh propane can also be introduced into the feed gas mixtures of the first and / or second oxidation stage of the reaction zone B for reasons of explosion safety be supplied.
  • reaction gas B 1 with which the reaction zone B is charged satisfies in this document in an expedient manner likewise the specification recommended in DE-A 102 46 119 and DE-A 102 45 585. Furthermore, a mechanical separation operation according to DE-A 103 16 039 is appropriately connected between reaction zone A and reaction zone B according to the invention
  • the load can also be related to only one component of the reaction gas. Then it is the amount of this component in Nl / l * h, which is passed through one liter of the catalyst bed per hour (pure inert matrasses are not counted to the fixed catalyst bed). If the catalyst bed consists of a mixture of catalyst and inert diluent bodies, the load, insofar as this is mentioned, may also relate only to the volume unit of catalyst contained.
  • an inert gas should generally be understood to mean a reactant gas constituent which essentially behaves as chemically inert under the conditions of the corresponding reaction, and more than 95 mol%, preferably more than 97 mol, of each inert constituent of the reaction gas per se -% or more than 99 mol% remains chemically unchanged.
  • Typical reaction gases B with which the reaction zone B can be charged in the process according to the invention, have the following contents:
  • Reaction gases B preferred according to the invention have the following contents:
  • Very particularly preferred reaction gases B according to the invention for the aforementioned feed have the following contents:
  • the molar ratio Vi of propane contained in reaction gas B to propylene contained in reaction gas B is 1 to 9 (ie, according to the invention, a propane / propene separation according to WO 04/094041 can advantageously be dispensed with ). Furthermore, it is advantageous within the aforementioned composition grid if the ratio V 2 of molecular oxygen contained in reaction gas B to propylene contained in reaction gas B is 1 to 2.5. Furthermore, it is within the meaning of the present invention within the aforementioned composition grid advantageous if the ratio V 3 of propylene contained in the reaction gas B to molecular hydrogen contained in the reaction gas B is 0.5 to 20. It is also advantageous within the aforementioned composition grid if the molar ratio V 4 of water vapor contained in the reaction gas B to the total molar amount of propane and propylene contained in the reaction gas B is 0.005 to 10.
  • Vi in the reaction gas B used for charging the reaction zone B (in the reaction gas B starting mixture) is 1 to 7 or up to 4 or 2 to 6 and particularly favorably 2 to 5 or 3.5 to 4.5.
  • V2 is 1.2 to 2.0 or 1.4 to 1.8.
  • V 3 is from 0.5 to 15, or from 0.5 to 10, or from 0.5 to 1.5, respectively.
  • V 4 in the reaction gas B starting mixture is preferably from 0.01 to 5, better still from 0.05 to 3, advantageously from 0.1 to 1 and particularly advantageously from 0.1 to 0.5 or even 0.3.
  • Non-explosive reaction gas B starting mixtures are preferred according to the invention.
  • the mixture should be called explosive here. If not spread, the mixture in this document is classified as non-explosive.
  • reaction gas starting mixture of a partial oxidation according to the invention is not explosive, this also applies to the latter formed during the partial oxidation of the same
  • molecular oxygen As source for the molecular oxygen not contained in the product gas A required in the reaction zone B, molecular oxygen as such, or a mixture of molecular oxygen and one (or a mixture of such inert gases) may be chemically inert in the reaction zone B.
  • Gas eg noble gases such as argon, molecular nitrogen, water vapor, carbon dioxide, etc.
  • the molecular oxygen is preferably fed as gas which is not more than 30% by volume, preferably not more than 25% by volume, advantageously not more than 20% by volume, particularly advantageously not more than 15% by volume. %, more preferably not more than 10% by volume, and most preferably not more than 5% by volume of other gases (other than mofeclean oxygen).
  • reaction zone B is supplied with the molecular oxygen to be supplied in its pure form.
  • the abovementioned applies in principle in the same way for the molecular oxygen to be supplied in the process according to the invention of the reaction zone A via the molecular oxygen optionally present in the after-treated residual gas I recycled to the reaction zone A.
  • the oxygen demand in the reaction zone A is a comparatively lower, but also a use of air as an oxygen source for the oxygen demand in the reaction zone A in the process according to the invention is particularly favorable for reasons of economy.
  • the aftertreated residual gas I recycled to the reaction zone A will still contain molecular oxygen still remaining in the reaction zone B and in principle this oxygen content of the aftertreated residual gas I recycled to the reaction zone A can also be such that it exceeds that no further supply of molecular oxygen into the reaction zone A is required in the process according to the invention.
  • the post-treated residual gas I recycled into the reaction zone A does not necessarily have to contain oxygen, and in many cases according to the invention, an additional oxygen supply is required in the reaction zone A.
  • gas eg., N2, H 2 O, noble gases and / or CO2
  • it is preferably carried out as a gas which is not more than 30% by volume, preferably not more than 25% by volume, advantageously not more than 20% by volume, more preferably not more than 15% by volume, better not more than 10% by volume and more preferably not more than 5% by volume or not more than 2% by volume of other gases other than molecular oxygen.
  • a gas which is not more than 30% by volume, preferably not more than 25% by volume, advantageously not more than 20% by volume, more preferably not more than 15% by volume, better not more than 10% by volume and more preferably not more than 5% by volume or not more than 2% by volume of other gases other than molecular oxygen.
  • the total content of the starting reaction gas B mixture of constituents other than propylene, molecular hydrogen, water vapor, propane and molecular oxygen is usually ⁇ 40% by volume, or ⁇ 35% by volume, or ⁇ 30% by volume, or ⁇ 25% by volume, or ⁇ 20% by volume, in many cases ⁇ 15% by volume, frequently ⁇ 10% by volume.
  • Such total ⁇ 5 vol .-% total contents are difficult to achieve within the scope of the procedure according to the invention.
  • up to 80% by volume of ethane and / or methane may be present.
  • Such contents will be, above all, carbon oxides (CO 2 , CO) and noble gas, but also Nebe ⁇ kompone ⁇ tenoxygenate such as formaldehyde, benzaldehyde, methacrolein, acetic acid, propionic acid, methacrylic acid, etc ..
  • ethylene, isobutene, n-butane, n-butenes and molecular nitrogen also belong to these possible other constituents of the reaction gas B starting mixture.
  • an advantage (see EP-A 293 224) of the procedure according to the invention is in principle that the reaction gas B starting mixture contains 0.1 to 30% by volume, or 1 to 25 or 20% by volume, often 5% may contain up to 15% by volume of CO 2 .
  • the CO content will normally be ⁇ 5% by volume, or ⁇ 4% by volume, or ⁇ 3% by volume, or ⁇ 2% by volume, usually ⁇ 1% by volume. Usually, however, it contains ⁇ 20% by volume, preferably ⁇ 15% by volume, more preferably ⁇ 10% by volume, and most preferably ⁇ 5% by volume of N 2 .
  • reaction zone A all known heterogeneously catalyzed partial dehydrogenations of propane are considered in reaction zone A, as described, for example, in US Pat. from the documents WO 03/076370, WO 01/96271, EP-A 1 17 146, WO 03/011804, EP-A 731 077, US-A 3,161,670, WO 01/96270, DE-A 33 13 573, DE-A 102 45 585, DE-A 103 16 039.
  • DE-A 10 2005 009 891, DE-A 10 2005 013 039, DE-A 10 2005 022 798, DE-A 10 2005 009 885, DE-A 10 2005 010 1 11, DE-A 10 2005 049 699 as well as from the German application DE-A 10 2004 032 129 are previously known.
  • the reaction zone A can be designed isothermally by targeted heat exchange with outside of the reaction zone A guided fluid (ie, liquid or gaseous). However, it can also be carried out adiabatically with the same reference base, ie essentially without such a targeted heat exchange with heat carriers conducted outside the reaction zone A. In the latter case, based on the one-time passage of the propane supplied to the reaction zone A through the reaction zone A, by taking measures recommended in the above references and to be described below, the gross thermal tone may be both endothermic (negative) or authotermic (substantially zero) ) or exothermic (positive).
  • the catalysts recommended in the abovementioned publications can be used in the process according to the invention.
  • the heterogeneously catalyzed propane dehydrogenation regardless of whether adiabatically or isothermally operated, both in a fixed bed reactor and in a moving bed, fluidized bed or fluidized bed reactor (the latter is due to its backmixing in particular for heating the reaction gas A starting mixture to the reaction temperature in the reaction zone A by hydrogen combustion in the reaction gas A, when the cycle gas I contains molecular oxygen) feasible.
  • the heterogeneously catalyzed partial dehydrogenation of propane to propylene requires comparatively high reaction temperatures. The achievable conversion is usually limited by the thermodynamic equilibrium.
  • Typical reaction temperatures are from 300 to 800 ° C or 400 to 700 0 C. per molecule of propane dehydrogenated to propylene is generated a molecule of hydrogen.
  • the working pressure in the reaction zone A is typically 0.3 to 5 or 3 bar. According to the invention, the working pressure in the reaction zone A is preferably 2 to 5 or 4 bar. But it can also be up to 20 bar.
  • reaction zone A is operated at very high pressures (eg> 5 or 10 to 20 bar) and burnt in it at least one amount of hydrogen corresponding to at least 50 mol% of the total amount of produced in the reaction zone A molecular hydrogen is It is advantageous to relax the product gas A by expansion in an expansion turbine, and with the work done to co-drive the compressor for the remainder I in advance of its CO ⁇ scrubbing. At the same time, the product gas A cools down to the temperature required for further use in the reaction zone B. High temperatures and removal of the reaction product H2 favor the equilibrium position in the reaction zone A in the sense of the target product.
  • very high pressures eg> 5 or 10 to 20 bar
  • the conversion can be increased by lowering the partial pressure of the dehydrogenation products.
  • This can be achieved in a simple manner, for example, by dehydration under reduced pressure (although carrying out at elevated pressure is generally advantageous for the catalyst service life) and / or by admixing substantially inert diluent gases, such as, for example, steam Dehydration reaction in the normal case! represents an inert gas.
  • substantially inert diluent gases such as, for example, steam Dehydration reaction in the normal case! represents an inert gas.
  • a dilution with water vapor as a further advantage, as a rule, a reduced coking of the catalyst used, since the water vapor reacts with coke formed according to the principle of coal gasification.
  • the heat capacity of the water vapor can also compensate for part of the dehydrogenation endotherm.
  • the amount of water vapor supplied to the reaction zone A in the same way, but usually> 1 vol .-%, often> 2 vol .-%, or> 3 vol .-% and often> 5 vol .-% be.
  • Further diluent suitable for heterogeneously catalyzed propane dehydrogenation! are, for example, nitrogen, noble gases such as He, Ne and Ar, but also compounds such as CO, CO 2 , methane and ethane. All diluents mentioned can be used either alone or in the form of different mixtures.
  • the process of the invention requires an outlet in an appropriate amount, which is why a corresponding fresh gas feed is less preferred according to the invention.
  • a substantially constant amount of a diluent gas can be circulated in the process according to the invention and any losses associated with it can be freshly supplemented.
  • dehydrogenation catalysts known in the art are suitable for the heterogeneously catalyzed propane dehydrogenation. They can be roughly divided into two groups. Namely in those that are oxidic in nature (for example
  • Chromium oxide and / or aluminum oxide and into those which consist of at least one deposited on a, usually oxidic, carrier, usually comparatively noble, metal (for example, platinum).
  • a, usually oxidic, carrier usually comparatively noble, metal (for example, platinum).
  • all dehydrogenation catalysts which can be used in WO 01/96270, EP-A 731077, DE-A 10211275, DE-A 10131297, WO 99/46039, US-A 4,788,371, US Pat EP-A-0 705 136, WO 99/29420, US Pat. No. 4,220,091, US Pat. No. 5,430,220, US Pat. No.
  • dehydrogenation catalysts comprising 10 to 99.9 wt .-% zirconia, 0 to 60 wt .-% alumina, silica and / or titanium dioxide and 0.1 to 10 wt .-% of at least one element of the first or second Main group, a third subgroup element, an eighth subgroup element of the periodic table of the elements, lanthanum and / or tin, with the proviso that the sum of the percentages by weight gives 100% by weight.
  • the dehydrogenation catalysts may be catalyst strands (diameter typically 1 to 10 mm, preferably 1 to 5 to 5 mm, length typically 1 to 20 mm, preferably 3 to 10 mm), tablets (preferably the same dimensions as in the strands) and or catalyst rings (outer diameter and length in each case typically 2 to 30 mm or up to 10 mm, wall thickness expediently 1 to 10 mm, or to 5 mm, or up to 3 mm) act.
  • catalyst strands diameter typically 1 to 10 mm, preferably 1 to 5 to 5 mm, length typically 1 to 20 mm, preferably 3 to 10 mm
  • tablets preferably the same dimensions as in the strands
  • catalyst rings outer diameter and length in each case typically 2 to 30 mm or up to 10 mm, wall thickness expediently 1 to 10 mm, or to 5 mm, or up to 3 mm
  • Fluidized bed or moving or moving bed
  • the dehydrogenation catalysts are such that they can both the dehydrogenation of propane and the combustion of Hydrogen combustion proceeds much faster in comparison with the dehydrogenation of propane in the case of a competition situation on the catalysts.
  • dehydrogenation processes useful in this invention also includes Catalytica® Studies Division, Oxidative Dehydrogenation and Alternative Dehydrogenation Processes, Study Number 4192 OD, 1993, 430 Ferguson Drive, Mountain View, California, 94043-5272, U.S.A.
  • Characteristic of the partial heterogeneously catalyzed dehydrogenation of propane is, as already stated, that it proceeds endothermically. That is, the heat required for the adjustment of the required reaction temperature and the heat required for the reaction (energy) must either be supplied to the reaction gas A in advance and / or in the course of the heterogeneously catalyzed dehydrogenation. Optionally, the reaction gas A must escape the required heat of reaction itself.
  • Another possibility of eliminating deposited carbon compounds is to treat the dehydrogenation catalyst from time to time at elevated temperature with an To flow through oxygen-containing gas (expedient in the absence of hydrocarbons) and thus quasi burn off the deposited carbon.
  • oxygen-containing gas expedient in the absence of hydrocarbons
  • some suppression of the formation of carbon deposits is also possible by adding molecular hydrogen to the heterogeneously catalyzed propane to be dehydrogenated before passing it over the dehydrogenation catalyst at elevated temperature.
  • reaction zone A In order to form a reaction gas A to be led through the at least one catalyst bed (also called feed gas mixture of reaction zone A or reaction gas A starting mixture in this document), only fresh propane and recycle gas I can be fed to reaction zone A in the simplest case.
  • the latter may already contain the amount of molecular oxygen that is required to cause the hydrogen combustion required in the reaction zone A according to the invention. This is due to the fact that in the reaction zone B relative to the reaction stoichiometry molecular oxygen is preferably used in excess, which normally remains largely in the recycle gas I in the process according to the invention.
  • the circulating gas I will also regularly contain just enough water vapor to be able to develop its advantageous properties for the overall process together with the water vapor formed in the reaction zone A during the hydrogen combustion.
  • the supply of further gaseous streams in the reaction zone A is not required in the case described above.
  • the reaction desired in the reaction zone A takes place in the simple passage of the reaction gas A through the same.
  • water vapor and / or molecular hydrogen can also be fed to form the reaction gas A to be led through the at least one catalyst bed in order to develop its advantageous effect described in this document.
  • the molar ratio of molecular hydrogen to propane in the feed gas mixture of the reaction zone A is generally ⁇ 5.
  • the molar ratio of water vapor to propane can in the feed gas mixture of the reaction zone A z. B.> 0 to 30, advantageously 0, 1 to 2 and preferably 0.5 to 1.
  • the feed gas mixture for the reaction zone A can be supplied with extra molecular oxygen (in pure form and / or as a mixture with inert gas) and / or extra inert gas as required.
  • the desired reaction in the reaction zone A can then again in a simple Passage of the reaction gas A (the Beschick ⁇ ngsgases the reaction zone A) by the same take place without along the reaction path, a supply of other gaseous streams takes place.
  • the reaction path in the reaction zone A is to be understood in this document as the flow path of that propane through the reaction zone A as a function of the dehydrogenative conversion (the conversion in the heterogeneously catalyzed dehydrogenation) of this propane, which is the reaction gas A before its first passage through at least one catalyst bed the reaction zone A is supplied.
  • a suitable reactor form for such a heterogeneously catalyzed propane dehydrogenation with a single pass of the feed gas mixture through the reaction zone A and without intermediate gas feed is z. B. the fixed bed tube or tube bundle reactor.
  • the dehydrogenation catalyst is in one or in a bundle of reaction tubes as a fixed bed.
  • the reaction tubes will advantageously be heated from the outside (of course they can also be cooled if necessary). This can be z. B. take place in that the space surrounding the reaction tubes a gas, for. As a hydrocarbon such as methane, is burned.
  • a typical Dehydrierrohrbündelreaktor comprises 300 to 1000 or more reaction tubes.
  • the temperature in the reaction tube interior is in the range of 300 to 700 0 C, preferably in the range of 400 to 700 0 C.
  • the reaction gas is A starting mixture fed to the tube reactor preheated to the reaction temperature. It is possible that the product gas (mixture) A leaves the reaction tube with a temperature 50 to 100 0 C lower.
  • this starting temperature can also be higher or at the same level, in the context of the aforementioned procedure, the use of oxidic dehydrogenation catalysts based on chromium and / or aluminum oxide is expedient.
  • the dehydrogenation catalyst is usually used undiluted. Industrially, one can operate several such tube bundle reactors in parallel and use their product gases A mixed to feed the reaction zone B. Optionally, only two of these reactors may be in dehydrogenation operation, while in the third reactor the catalyst feed is regenerated.
  • reaction zone A of the process according to the invention may also consist of two sections. Such a construction of the reaction zone A is particularly recommended if the feed gas for the reaction zone A does not comprise any molecular oxygen (this may for example be the case if the cycle gas I contains no molecular oxygen).
  • the actual heterogeneously catalyzed dehydrogenation can take place in the first section and in the second section, after an intermediate supply of molecular oxygen and / or a mixture of molecular oxygen and inert gas, the heterogeneously catalyzed hydrogen combustion required according to the invention.
  • the reaction zone A will advantageously be operated such that, based on a single pass through the reaction zone A,> 5 mol% to ⁇ 60 mol%, preferably> 10 mol% to ⁇ 50 mol% , Particularly preferably> 15 mol% to ⁇ 40 mol%, and very particularly preferably> 20 mol% to ⁇ 35 mol% of the total reaction zone A propane fed in the reaction zone A dehydrating be implemented.
  • Such a limited conversion in the reaction zone A is erfindun ⁇ gshack normally adequate because the remaining amount of unreacted propane in the subsequent reaction zone B essentially acts as a diluent gas and in the course of the procedure according to the invention largely lossless can be recycled to the reaction zone A.
  • the advantage of a procedure with low propane conversion is that with a single pass of the reaction gas A through the reaction zone A, the heat required for the endothermic dehydrogenation is comparatively low and relatively low reaction temperatures are sufficient to achieve the desired conversion.
  • the feed gas mixture for the reaction zone A is usually first heated to a temperature of 500 to 700 0 C (or from 550 to 65O 0 C) (for example, by direct firing of the surrounding wall).
  • a single adiabatic passage through a catalyst bed will then be sufficient to achieve both the desired dehydrogenative conversion and the hydrogen combustion required according to the invention, the reaction gas heating up grossly depending on the quantitative ratio of endothermic dehydrogenation and exothermic hydrogen combustion , cool or thermally neutral behavior.
  • an adiabatic mode of operation is preferred in which the Cooling reaction gas at about 30 to 2Q0 ° C in a single pass.
  • hydrogen formed in the course of the dehydrogenation in a second section of the reaction zone A can be subjected to heterogeneous catalysis with intermediate molecular oxygen fed in. This combustion can also be carried out adiabatically.
  • a single shaft furnace reactor is sufficient as a fixed bed reactor, in particular in adiabatic operation, which flows through the reaction gas A axially and / or radially.
  • this is a single closed reaction volume, for example a container whose inside diameter is 0.1 to 10 m, possibly also O 1 S to 5 m, and in which the fixed catalyst bed is placed on a support device (for example a Grate) is applied.
  • the catalyst-charged reaction volume which is substantially thermally insulated in adiabatic operation, is thereby flowed through axially with the hot propane-containing reaction gas A.
  • the catalyst geometry can be both spherical and annular or strand-shaped. Since in this case the reaction volume can be realized by a very cost-effective apparatus, all catalyst geometries which have a particularly low pressure loss are to be preferred.
  • the reactor may for example consist of two in a Ma ⁇ telhülle, concentric nested, cylindrical see gratings and the catalyst bed be arranged in their Ringspait. In the adiabatic case, the metal shell would possibly be thermally insulated again.
  • catalyst feedstocks for a heterogeneously catalyzed propane dehydrogenation are the catalysts disclosed in DE-A 199 37 107, in particular all catalysts disclosed by way of example, and mixtures thereof with geometrical shaped bodies which are inert with respect to the heterogeneously catalyzed dehydrogenation.
  • the aforementioned catalysts can be easily regenerated, for example, by reacting at an inlet temperature of 300 to
  • the catalyst (bed) loading with regeneration gas can be eg 50 to 10,000 h- 1 and the oxygen content of the regeneration gas 0.1 or 0.5 to 20 vol .-%.
  • regeneration gas eg air
  • air can be used as regeneration gas under otherwise identical regeneration conditions.
  • inert gas for example N2
  • This loading with reaction gas A can be, for example, 100 to 40,000 or up to 10,000 Ir 1 , frequently 300 to 7,000 h- 1 , which is often about 500 to 4,000 hr -1 .
  • the heterogeneously catalyzed propane dehydrogenation in the reaction zone A (in particular in the case of propane conversions of from 15 to 35 mol% based on a single pass) can be realized in a tray reactor.
  • the catalyst bed number may be 1 to 20, preferably 2 to 8, but also 3 to 6. With increasing Horden number can be increasingly easier to achieve increased propane conversions.
  • the catalyst beds are preferably arranged radially or axially one behind the other. In terms of application technology, the catalyst fixed bed type is used in such a tray reactor.
  • the fixed catalyst beds are arranged in a shaft furnace reactor axially or in the annular gaps of centrically nested cylindrical gratings.
  • the reaction gas A on its way from a catalyst bed to the next catalyst bed, for example, by passing over heated with hot gases heat exchanger surfaces (eg ribs) or by passing heated with hot fuel gases pipes, in the Horde ⁇ reaktor an inter-heating (at Demand can be done in a similar manner, an intermediate cooling).
  • the tray reactor is otherwise operated adiabatically, it is sufficient for propane conversions ⁇ 30 mol%, especially when using the catalysts described in DE-A 199 37 107, in particular the exemplary embodiments, the reaction gas mixture to a temperature of 450 to 550 0 C (preferably 450 to 500 0 C) preheated to lead into the dehydrogenation reactor and keep within the Horde reactor in this temperature range.
  • the entire propane dehydrogenation is to be realized at extremely low temperatures, which proves to be particularly favorable for the lifetime of the fixed catalyst beds between two regenerations.
  • the reaction gas mixture is conducted into the dehydrogenation reactor preheated to higher temperatures (these can be up to 700 0 C) and maintained within the tray reactor in this elevated temperature range.
  • reaction gas A is either already enriched in the first catalyst bed (eg as a constituent of cycle gas I) (then the reaction gas A starting mixture should advantageously contain molecular hydrogen added) and / or moiekular oxygen is added between the subsequent catalyst beds to a limited extent ,
  • the limited combustion of molecular hydrogen contained in the reaction gas A and formed in the course of the heterogeneously catalyzed propane dehydrogenation and / or added to the reaction gas A can be effected in a particularly targeted and controlled manner (typically catalyzed by the dehydrogenation catalysts).
  • catalyst beds in the reactor reactor which are charged with catalyst which catalyzes (specifically) selectively (selectively) the combustion of hydrogen
  • catalyst beds may be used in an alternating manner to form beds containing dehydrogenation catalyst in U.S. Patent Nos. 4,886,928, 5,530,209, 5,530,171, 5,527,979 and 5,563,314; Horde ⁇ reaktor be housed, these catalysts are also suitable for the already described Wass erstoffverbrennung in a second section of the reaction zone A).
  • the heat of reaction thus released thus makes possible a total of exothermic or altogether autothermal (depending on the amount of molecular hydrogen burned) (the gross atomic value is substantially zero) or an overall endothermic mode of operation of the heterogeneously catalyzed propane dehydrogenation.
  • an oxygen feed as described above should be carried out so that the oxygen content of the reaction gas A, based on the amount of molecular hydrogen contained therein, is 0.5 to 50 or 30, preferably 10 to 25,% by volume.
  • the molecular oxygen is preferably fed as gas which is not more than 30% by volume, preferably not more than 25% by volume, advantageously not more than 20% by volume, particularly advantageously not more than 15% by volume. more preferably not more than 10% by volume, and more preferably not more than 5% by volume.
  • the advantageousness of the process according to the invention is not only significant if, in the reaction zone A, a quantity of hydrogen of about 50 mol% of the molecular hydrogen formed in the reaction zone A is burned. Rather, this advantage is already evident even if, in the reaction zone A, a hydrogen amount of 5 to 95 mol%, preferably 10 to 90 mol%, particularly preferably 15 to 85 mol%, very particularly preferably 20 to 80 more preferably 25 to 75 mol%, more preferably 30 to 70 mol%, still more preferably 35 to 65 mol%, and most preferably 40 to 60 mol% or 45 to
  • an oxygen feed as described above should be carried out so that the oxygen content of the reaction gas A, based on the amount of propane and propylene contained therein, is 0.01 or 0.5 to 3% by volume.
  • the isothermal nature of the heterogeneously catalyzed propane dehydrogenation can be further improved by attaching closed internals (eg tubular) in the space between the catalyst beds in the tray reactor, but preferably not necessarily evacuated prior to their filling. Such fittings can also in respective catalyst bed are provided. These internals contain suitable solids or liquids that evaporate or melt above a certain temperature, consuming heat and condense where it falls below that temperature, releasing heat.
  • closed internals eg tubular
  • One way to heat the charge gas mixture for the heterogeneously catalyzed propane dehydrogenation in the reaction zone A to the required reaction temperature is also to burn a portion of the propane and / or H 2 contained therein by means of molecular oxygen contained in the feed gas mixture entering the reaction zone A.
  • the heating to the desired temperature for the dehydrogenation reaction (such a procedure is (as already mentioned) in particular in a fluidized bed reactor advantageous).
  • reaction zone A of the method according to the invention as described in DE-A 10 2004 032 129 and DE-A 10 2005 013 39, but with the difference that as a feed gas mixture of the reaction zone A is a mixture of water vapor .
  • the reaction zone A is realized as a (preferably adiabatic) tray reactor in which catalyst beds (preferably fixed beds) are arranged radially or axially one behind the other.
  • catalyst beds preferably fixed beds
  • the number of Katalysatorbetthorden in such a tray reactor is three.
  • the heterogeneously catalyzed partial propane dehydrogenation is carried out autothermally.
  • the feed gas mixture of the reaction zone A is added behind the first catalyzer (solid) bed and, between the catalyst beds (fixed) following in the flow direction of the first catalyst bed, a limited amount of molecular oxygen or a mixture containing such with inert gas ,
  • a limited combustion of hydrogen formed in the course of the heterogeneously catalyzed propane dehydrogenation (and optionally at most small amounts of propane and / or propylene) are effected whose exothermic heat of reaction substantially preserves the dehydrogenation.
  • the partial heterogeneously catalyzed dehydrogenation of the propane is expediently distributed essentially over the three catalyst hordes in such a way that the conversion of the propane fed into the reactor, based on a single reactor pass, is about 20% by mass (of course it can be used in the process according to the invention but also 30 mol .-%, or 40 mol .-%, or 50 mol .-%).
  • the achieved selectivity of the propylene formation is regularly at 90 mol .-%.
  • the maximum revenue contribution of a single horde migrates with increasing operating time in the flow direction from the front to the back.
  • the catalyst charge is regenerated before the third in the direction of flow Horde provides the maximum contribution to revenue.
  • the regeneration takes place when the coking of all hordes has reached an identical extent.
  • the charge gas mixture for reaction zone A in the above-described heterogeneously catalyzed partial propane dehydrogenation in the tray reactor consists only of fresh propane and recycled from the partial oxidation in the dehydrogenation cycle gas I, resulting from the partial oxidation usually a sufficient amount of
  • a disadvantage of the process described above is that virtually all catalyzers which catalyze the dehydrogenation of propane also catalyze the combustion (complete oxidation of propane and propylene to carbon oxides and water vapor) of propane and propylene with molecular oxygen and, as already stated, Normally, molecular oxygen is contained in the recycled in the heterogeneously catalyzed partial dehydrogenation of the propane recycle gas I from the partial oxidation.
  • the dehydrogenating gas circulation will be realized expediently according to the jet pump principle (it is also referred to as a loop procedure). Furthermore, in this document, the possibility is mentioned, the feed gas mixture for the reaction zone A additionally add molecular hydrogen as further oxidation protection. About the requirement, the molecular Adding hydrogen into the motive jet for the jet pump in a specific supply hierarchy is described in DE-A 10 2005 049 699.
  • DE-A 10 2004 032 129 and DE-A 10 2005 013 039 it is advantageous not to recycle a molecular gas containing molecular oxygen containing from the heterogeneously catalyzed partial oxidation into the charge gas mixture for the heterogeneously catalyzed partial propane dehydrogenation , Rather, this recirculation will advantageously take place only after a certain dehydrogenation conversion into the reaction gas A of the reaction zone A. It is also proposed in DE-A 10 2004 032 129, in advance of this recirculation, preferably to additionally add external molecular hydrogen to the feed gas mixture of the reaction zone A. Furthermore, also in DE-A 10 2004 032 129 the loop procedure for the dehydrogenation is propagated. Propulsion jet is transferred to the procedure of the invention exclusively recycled from the partial oxidation in the dehydrogenation cycle gas I.
  • the feed gas mixture for the same is composed of circulating gas I 1 from fresh propane, from external molecular hydrogen, from a minimum amount of external water vapor and recycle gas recirculated from the dehydrogenation itself (the external water vapor could also be dispensed with).
  • the propulsion jet used is a mixture of fresh propane, external molecular hydrogen, recycle gas I from the partial oxidation and external water vapor.
  • cycle gas I generally contains not only molecular oxygen and water vapor, but also molecular hydrogen, carbon monoxide and carbon dioxide. That is, it usually also contains CO. According to the invention, cycle gas I preferably contains from 5 to 15% by volume of CO 2 .
  • the product gas A withdrawn from the reaction zone A advantageously has the following contents in the process according to the invention:
  • the temperature of the product gas A is typically 400 to 70O 0 C, preferably 450 to 650 0 C.
  • the pressure of the product gas A leaving the reaction zone A is preferably 2 to 4 bar according to the invention. But it can also, as already mentioned, be up to 20 bar.
  • the product gas A is now used without further secondary component removal for feeding the at least one oxidation reactor in the reaction zone B with reactant gas B.
  • the product gas A it is sufficient to add to the product gas A that amount of molecular oxygen which is necessary for obtaining the objective in the reaction zone B.
  • This addition may in principle be pure oxygen or as a mixture (eg air) of molecular oxygen and one or more gases chemically inert in reaction zone B (eg N 2, H 2 O, noble gases, CO 2 ) ,
  • it is preferably carried out as a gas which is not more than 30% by volume, preferably not more than 25% by volume, advantageously not more than 20% by volume, more preferably not more than 15% by volume, better not contains more than 10% by volume and more preferably not more than 5% by volume or not more than 2% by volume of other gases other than molecular oxygen.
  • pure oxygen is not more than 30% by volume, preferably not more than 25% by volume, advantageously not more than 20% by volume, more preferably not more than 15% by volume, better not contains more than 10% by volume and more preferably not more than 5% by volume or not more than 2% by volume of other gases other than molecular oxygen
  • the amount of molecular oxygen supplied is such that in the feed gas for the reaction zone B (in the starting reaction gas B mixture), the molar ratio of molecular oxygen to propylene contained is> 1 and ⁇ 3.
  • the product gas A erfi ⁇ dungshunt suitably to a temperature in the range of 250 to 350 0 C, preferably in the range of 270 to 320 ° C from.
  • This cooling is advantageous according to the invention by indirect heat exchange (preferably in countercurrent operation, this statement applies quite generally to indirect heat exchange in this document, unless explicitly stated otherwise).
  • the cooling agent used here is preferably the reaction gas A starting mixture for reaction zone A, which in this way is simultaneously brought to the reaction temperature desired in reaction zone A (in principle, however, cooling can, as already mentioned, also be carried out by expansion in an expansion turbine if the outlet pressure is sufficiently high in this respect).
  • the supply of molecular oxygen-containing gas to the product gas A, cooled as described above can be accomplished by operating a jet pump with the product gas A as a motive jet, comprising a motive nozzle, a mixing section, a diffuser, and a suction nozzle Direction of conveyance through the motive nozzle via the mixing section and the diffuser relaxed jet of fuel into the inlet of the at least one oxidation reactor in the reaction zone B and the suction of the suction nozzle in the direction of the source of the molecular oxygen-containing gas and thereby by the negative pressure generated in the suction sucks the suction of the molecular oxygen gas at transported simultaneous mixing with the propulsion jet through the mixing section via the diffuser and the resulting reaction gas B starting mixture in the inlet of the second reaction zone B, or in the inlet of at least one oxidation reactor of the second reaction zone B releases.
  • the above variant is particularly applicable when the product gas A has a pressure of 2 to 5 or more, or up to 4 bar.
  • the gas containing the molecular oxygen can also be mixed in a conventional manner with the product gas A to the sample gas mixture for the reaction zone B (reaction gas B starting mixture).
  • reaction gas B starting mixture reaction gas B starting mixture
  • a mechanical separation operation according to DE-A 103 16 039 can be connected between reaction zone A and reaction zone B expediently.
  • the heterogeneously catalyzed gas-phase partial oxidation of propylene to acrylic acid with molecular oxygen basically proceeds in two successive steps along the reaction coordinate, of which the first leads to the acrolein and the second from acrolein to acrylic acid.
  • the process according to the invention is carried out up to the predominant formation of acrylic acid, it is advantageous according to the invention for the process to be carried out in two stages, ie. H. in two consecutively arranged oxidation stages, expediently in each of the two oxidation states to be used fixed catalyst bed and preferably also the other reaction conditions, such.
  • the temperature of Katatysa- torfestbetts be adapted in an optimizing way.
  • the multimetal oxides containing the elements Mo, Fe, Bi which are particularly suitable for the catalysts of the first oxidation state (propylene ⁇ acrolein), also catalyze, to some extent, the second oxidation state (acrolein ⁇ acrylic acid), the second oxidation state can be used for the second oxidation state usually preferred catalysts whose active composition is at least one element containing Mo and V-containing multimetal.
  • reaction gas B produced according to the invention is used as reaction gas starting mixture for the first reaction stage (propylene to acrolein).
  • reaction gas starting mixture for the first reaction stage (propylene to acrolein).
  • the procedure is the same as in the exemplary embodiments of the cited documents (in particular the fixed catalyst beds and reactant loading of the fixed catalyst beds).
  • the amounts of oxygen in the reaction zone B are dimensioned so that the product gas B contains unreacted molecular oxygen (advantageously ⁇ 0.5 to 6% by volume, advantageously 1 to 5% by volume, preferably 2 to 4% by volume).
  • unreacted molecular oxygen advantageously ⁇ 0.5 to 6% by volume, advantageously 1 to 5% by volume, preferably 2 to 4% by volume.
  • Multimetalloxidkatalysatoren are often previously described and well known to the skilled person.
  • EP-A 253 409 on page 5 refers to corresponding US patents.
  • DE-A 44 31 957, DE-A 10 2004 025 445 and DE-A 44 31 949 also disclose advantageous catalysts for the particular oxidation state. This applies in particular to those of the general formula I in the two above-mentioned prior art
  • the Mo, Bi and Fe-containing multimetal oxide catalysts suitable for this reaction stage are those described in Research Disciosure No. 497012 of 29.08.2005, DE-A 100 46 957, DE-A 100 63 162, DE-C 3 338 380, DE -A 199 02 562, EP-A 15 565, DE-C 2 380 765, EP-A 8 074 65, EP-A 27 93 74, DE-A 330 00 44, EP-A 575897, US-A 4438217, DE-A 19855913, WO 98/24746, DE-A 197 46 210 (those of the general formula II), JP-A 91/294239, EP-A 293 224 and EP-A 700 714 are disclosed. This applies in particular to the exemplary embodiments in these documents, among which those of EP-A 15 565, EP-A 575 897, the
  • DE-A 197 46 210 and DE-A 198 55 913 are particularly preferred.
  • a catalyst according to Example 1c from EP-A 15 565 and a catalyst to be prepared in a corresponding manner, the active composition has the composition M ⁇ i2Ni6,5Zn2Fe2BiiPo, ooe5Ko, o6 ⁇ x * 10Si ⁇ 2. Also to be highlighted are the example with the running No.
  • these hollow cylinders have a geometry of 5.5 mm ⁇ 3 mm ⁇ 3.5 mm, or 5 mm ⁇ 2 mm ⁇ 2 mm, or 5 mm ⁇ 3 mm ⁇ 2 mm, or 6 mm ⁇ 3 mm ⁇ 3 mm, or 7 mm x 3 mm x 4 mm (each outer diameter x height x inner diameter).
  • Other possible catalyst geometries in this context are strands (eg 7.7 mm in length and 7 mm in diameter, or 6.4 mm in length and 5.7 mm in diameter).
  • a multiplicity of the multimetal oxide active compositions which are suitable for the step of propylene to acrolein and, if appropriate, acrylic acid can be obtained under the general formula IV
  • X 2 thallium, an alkali metal and / or an alkaline earth metal
  • X 3 zinc, phosphorus, arsenic, boron, antimony, tin, cerium, lead and / or tungsten,
  • X 4 silicon, aluminum, titanium and / or zirconium
  • n a number which is determined by the valence and frequency of the elements other than oxygen in IV,
  • active compounds can be prepared by reacting an intimate, preferably feinteiiiges composition corresponding to the stoichiometry dry mixture and calcining, from suitable sources of their elemental constituents at temperatures from 350 to 650 0 C of the general formula IV in a simple manner.
  • the Caicination can be carried out both under inert gas and under an oxidative atmosphere such. As air (mixture of fnertgas and oxygen) as well as under reducing atmosphere (eg., Mixture of I ⁇ ertgas, NH3, CO and / or H2) take place.
  • air mixture of fnertgas and oxygen
  • reducing atmosphere eg., Mixture of I ⁇ ertgas, NH3, CO and / or H2
  • the Calcinatio ⁇ sdauer can be a few minutes to a few hours and usually decreases with the temperature.
  • Suitable sources of the elemental constituents of the multimetal oxide active compositions IV are those compounds which are already oxides and / or those compounds which can be converted into oxides by heating, at least in the presence of oxygen.
  • suitable starting compounds are in particular halides, nitrates, formates, oxalates, citrates, acetates, carbonates, amine complexes, ammonium salts and / or hydroxides (compounds such as NH 4 OH, (NH 4 ) 2 CO 3, NH 4 NO 3, NH 4 CHO 2 , CH3COOH, NH4CH3CO2 and / or ammonium oxalate, which can disintegrate and / or decompose into gaseous escaping compounds at the latest during later calcining, can be additionally incorporated into the intimate dry mixture).
  • the intimate mixing of the starting compounds for the preparation of Multimetalloxidtagenmassen IV can be done in dry or wet form. If it takes place in dry form, the starting compounds are expediently used as finely divided powders and subjected to the calcination after mixing and optionally compacting. Preferably, however, the intimate mixing takes place in wet form.
  • the starting compounds are mixed together in the form of an aqueous solution and / or suspension. Particularly intimate dry mixtures are obtained in the described mixing process when starting exclusively from sources of the egg cement constituents present in dissolved form.
  • the solvent used is preferably water.
  • the resulting aqueous composition is dried, wherein the drying process is preferably carried out by spray-drying the aqueous mixture with outlet temperatures of 100 to 150 0 C.
  • the multimetal oxide active compounds of the general formula IV can be used for the step "propylene ⁇ acrolein (and optionally acrylic acid)" shaped both in powder form and to specific catalyst geometries, wherein the shaping can take place before or after the final Caicination.
  • solid catalysts can be prepared from the powder form of the active composition or its uncalcined and / or partially calcined precursor composition by compacting to the desired catalyst geometry (for example by tableting, extruding or extrusion molding) be optionally with aids such.
  • graphite or stearic acid as lubricants and / or molding aids and reinforcing agents such as microfibers of glass, asbestos, silicon carbide or potassium titanate can be added.
  • Suitable Vollkatalysatorgeometrien are z.
  • the full catalyst may also have spherical geometry, wherein the ball diameter may be 2 to 10 mm.
  • a particularly favorable hollow cylinder geometry is 5 mm ⁇ 3 mm ⁇ 2 mm (outer diameter ⁇ length ⁇ inner diameter), in particular in the case of solid catalysts.
  • the shaping of the pulverulent active composition or its pulverulent, not yet and / or partially calcined, precursor composition can also be effected by application to preformed inert catalyst supports.
  • the coating of the carrier body for the production of the coated catalysts is usually carried out in a suitable rotatable container, as it is z. B. from DE-A 29 09 671, EP-A 293 859 or from EP-A 714 700 is known.
  • the applied powder mass is moistened for coating the carrier body and after application, for. B. mitteis hot air, dried again.
  • the layer thickness of the powder mass applied to the carrier body is expediently chosen to be in the range 10 to 1000 ⁇ m, preferably in the range 50 to 500 ⁇ m and particularly preferably in the range 150 to 250 ⁇ m.
  • carrier materials it is possible to use customary porous or non-porous aluminum oxides, silicon dioxide, thorium dioxide, zirconium dioxide, silicon carbide or silicates, such as magnesium silicate or aluminum silicate. As a rule, they are essentially inert with respect to the target reaction subject to the process according to the invention.
  • the carrier bodies may be regularly or irregularly shaped, with regularly shaped carrier bodies having a distinct surface roughness, e.g. As balls or hollow cylinders, are preferred. Suitable is the use of substantially non-porous, surface roughness, spherical supports made of steatite whose diameter is 1 to 10 mm or up to 8 mm, preferably 4 to 5 mm.
  • the use of cylinders as carrier bodies whose length is 2 to 10 mm and whose outer diameter is 4 to 10 mm is also suitable.
  • the wall thickness is usually from 1 to 4 mm.
  • annular carrier body have a length of 2 to 6 mm, an outer diameter of 4 to 8 mm and a wall thickness of 1 to 2 mm.
  • Particularly suitable according to the invention are rings of the geometry 7 mm ⁇ 3 mm ⁇ 4 mm (outer diameter ⁇ length ⁇ inner diameter) as the carrier body.
  • the fineness of the material applied to the surface of the carrier Of course, the catalytically active oxide masses to be applied per se are adapted to the desired shell thickness (see EP-A 714 700).
  • Multimetalioxidin are also compounds of general formula V,
  • Y 1 only bismuth or bismuth and at least one of the elements tellurium, antimony,
  • Y 2 molybdenum, or tungsten, or molybdenum and tungsten
  • Y 3 an alkali metal, thallium and / or samarium
  • Y 4 an alkaline earth metal, nickel, cobalt, copper, manganese, zinc, tin, cadmium and / or mercury
  • Y 7 a rare earth metal, titanium, zirconium, niobium, tantalum, rhenium, ruthenium, rhodium, silver, gold, aluminum, gallium, indium, silicon, germanium, lead,
  • a ' 0.01 to 8
  • b' 0, 1 to 30,
  • c ' 0 to 4
  • d 0 to 20, e'> 0 to 20,
  • f 0 to 6
  • g ' O to 15,
  • h ' 8 to 16
  • x', y ' numbers determined by the valency and frequency of the non-oxygen elements in V
  • p, q numbers whose ratio p / q is 0.1 to 10 .
  • Y 1 a ⁇ 2 b'Gy comprising three-dimensionally extended areas of chemical composition Y 1 a ⁇ 2 b'Gy, delimited by their local environment due to their different compositions from their local environment, whose largest diameter (longest direct link between two on the surface (interface) of the area located) is 1 nm to 100 ⁇ m, frequently 10 ⁇ m to 500 nm or 1 ⁇ m to 50 or 25 ⁇ m.
  • suitable multimetal V are those in which Y 1 is bismuth.
  • Z 2 molybdenum, or tungsten, or molybdenum and tungsten
  • Z 4 thallium, an alkali metal and / or an alkaline earth metal
  • Z 5 phosphorus, arsenic, boron, antimony, tin, cerium and / or lead,
  • Z 6 silicon, aluminum, titanium and / or zirconium
  • Z 7 copper, silver and / or gold
  • suitable multimetal oxide compositions V are present in the form of three-dimensionally extended regions of the chemical composition Y 1 a Y 2 b O X '[B i a ZVO X -] which are differentiated from their local environment because of their chemical composition different from their local environment whose largest diameter is in the range of 1 nm to 100 microns.
  • the statements made with respect to multimetal oxide compositions V catalysts include the statements made in the case of the multimetal oxide compositions IV catalysts.
  • the preparation of multimetal oxide compositions V-active materials is z. As described in EP-A 575 897 and in DE-A 198 55 913.
  • inert support materials come i.a. also as inert materials for dilution and / or delimitation of the corresponding fixed catalyst beds, or as their protective and / or the gas mixture aufmelende inflow into consideration.
  • the heterogeneously catalyzed gas phase partial oxidation of acrolein to acrylic acid come, as already said, in principle all Mo and V containing multimetal oxide as active compositions for the required catalysts into consideration, for. B. those of DE-A 100 46 928.
  • X 1 W, Nb, Ta, Cr and / or Ce
  • X 2 Cu, Ni, Co, Fe, Mn and / or Zn,
  • X 3 Sb and / or Bi
  • X 4 one or more alkali metals
  • X 5 one or more alkaline earth metals
  • X 6 Si, Al, Ti and / or Zr
  • n a number which is determined by the valence and frequency of the elements other than oxygen in VII,
  • Embodiments of the invention within the active multimetal oxide VI1 are those which are covered by the following meanings of the variables of general formula VII:
  • X 2 Cu, Ni 1 Co and / or Fe
  • X 5 Ca, Sr and / or Ba
  • X 6 Si, A! and / or Ti
  • n a number that is determined by the valence and frequency of elements other than oxygen in VtI
  • multimetal oxides VII according to the invention are those of the general formula VIII 1
  • VlII a number determined by the valency and frequency of oxygen-different elements in VlII is determined
  • suitable Multimetalloxidgenmassen (VII) are known per se, z. For example, in DE-A 43 35 973 or in EP-A 714 700 disclosed way available.
  • suitable Multimetalloxiditmassen in a simple manner be prepared by suitable sources of their elemental constituents a possibly intimate, preferably finely divided, their stoichiometry correspondingly assembled, dry mixture and this calcined at temperatures of 350 to 600 0 C.
  • the calcination can be carried out both under inert gas and under an oxidative atmosphere such.
  • air mixture of inert gas and oxygen
  • a reducing atmosphere eg., Mixtures of inert gas and reducing gases such as H, NH 3 , CO, methane and / or acrolein or said reducing acting gases per se
  • Suitable sources of the elemental constituents of the multimetal oxide active compounds VII are those compounds which are already oxides and / or those compounds which can be converted into oxides by heating, at least in the presence of oxygen.
  • the intimate mixing of the starting compounds for the preparation of bulk metal oxide VII can be carried out in dry or wet form. If it takes place in dry form, then the starting compounds are expediently used as feinteiiige powder and subjected to the mixing and optionally compacting the calcination. Preferably, however, the intimate mixing takes place in wet form.
  • the starting compounds are mixed together in the form of an aqueous solution and / or suspension. Particularly intimate dry mixtures are obtained in the described mixing process when starting exclusively from sources of the elementary constituents present in dissolved form.
  • the solvent used is preferably water.
  • the resulting aqueous composition is dried, wherein the drying process is preferably carried out by spray-drying the aqueous mixture with outlet temperatures of 100 to 150 0 C.
  • the resulting multimetal oxide compositions in particular those of the general formula VII, can be used for the acrolein oxidation both in powder form (eg in a fluidized bed reactor) and shaped to specific catalyst geometries, wherein the shaping can take place before or after the final calcination.
  • solid catalysts can be prepared from the powder form of the active composition or its uncalcined precursor composition by compacting to the desired catalyst geometry (for example by tableting, extruding or extrusion molding). if necessary aids such.
  • graphite or stearic acid as lubricants and / or molding aids and reinforcing agents such as microfibers of glass, asbestos, silicon carbide or potassium titanate can be added.
  • Suitable Vollkatalysatorgeometrien are z. B, solid cylinder or hollow cylinder with an outer diameter and a length of 2 to 10 mm. In the case of Hohlzyiinder a wall thickness of 1 to 3 mm is appropriate.
  • the unsupported catalyst may also have spherical geometry, wherein the ball diameter may be 2 to 10 mm (eg, 8.2 mm or 5, 1 mm).
  • the shaping of the powdered active composition or its powdery, not yet calcined precursor composition can also be effected by application to preformed inert catalyst supports.
  • the coating of the carrier body for the preparation of the coated catalysts is usually carried out in a suitable rotatable container, as z. B. from DE-A 2 909 671, EP-A 293 859 or from EP-A 714 700 is known,
  • the applied powder mass is moistened for coating the carrier body and after application, for. B. by means of hot air, dried again.
  • the layer thickness of the powder mass applied to the carrier body is expediently chosen to be in the range 10 to 1000 ⁇ m, preferably in the range 50 to 500 ⁇ m and particularly preferably in the range 150 to 250 ⁇ m.
  • carrier materials it is possible to use customary porous or non-porous aluminum oxides, silicon dioxide, thorium dioxide, zirconium dioxide, silicon carbide or silicates, such as magnesium silicate or aluminum silicate.
  • the carrier bodies may be regularly or irregularly shaped, with regularly shaped carrier bodies having a distinct surface roughness, e.g. B. balls or Hohlzyiinder with chippings, are preferred.
  • Suitable is the use of substantially nonporous, surface rough, spherical steatite supports whose diameter is 1 to 10 mm or 8 mm, preferably 4 to 5 mm. That is, suitable ball geometries may have diameters of 8.2 mm or 5.1 mm.
  • cylinders as support bodies whose length is 2 to 10 mm and whose outer diameter is 4 to 10 mm.
  • the wall thickness is usually 1 to 4 mm.
  • annular carrier body Preferably to be used annular carrier body have a length of 2 to 6 mm, an outer diameter of 4 to 8 mm and a wall thickness of 1 to 2 mm.
  • the fineness of the catalytically active oxide masses to be applied to the surface of the carrier body is, of course, adapted to the desired shell thickness (cf EP-A 714 700).
  • Suitable multimetal oxide active materials to be used for the step "acrolem ⁇ acrylic acid" are furthermore compounds of the general formula IX,
  • Z 2 Cu, Ni, Co, Fe, Mn and / or Zn
  • Z 3 Sb and / or Bi
  • Z 4 Li 1 Na 1 K, Rb, Cs and / or H
  • Z 5 Mg, Ca, Sr and / or Ba
  • Z 6 Si, Al, Ti and / or Zr
  • Z r Mo 1 W, V, Nb and / or Ta, preferably Mo and / or W
  • starting material 1 in finely divided form vor description (starting material 1) and then the preformed solid starting material 1 in an aqueous solution, an aqueous suspension or in a finely divided dry mixture of sources of elements Mo, V, Z 1 , Z 2 , Z 3 , Z 4 , Z 5 , Z 6 , which the aforementioned elements in Stochiomet ⁇ e D
  • Mo 12 V a Z 1 b Z 2 c Z 3 d Z 4 e Z 5 f Z 6 g (D), contains (starting material 2), incorporated in the desired ratio p: q, which optionally dry resulting aqueous mixture, and the dry precursor material thus calcined prior to or after drying to the desired Kataiysator- geometry at temperatures of 250 to 600 0 C.
  • multimetal oxide compositions IX Preference is given to the multimetal oxide compositions IX in which the incorporation of the preformed solid starting material 1 into an aqueous starting material 2 takes place at a temperature ⁇ 70 ° C.
  • a detailed description of the preparation of multimetal oxide compositions Vl catalysts contain, for. For example, EP-A 668 104, DE-A 197 36 105, DE-A 100 46 928, DE-A 197 40 493 and DE-A 195 28 646.
  • suitable multimetal oxide catalysts are also those of DE-A 198 15 281, in particular with multimexloxidgenmassen the general formula I of this document.
  • full catalyst rings are used and for the step from acroie to acrylic acid, shell catalyst rings are used.
  • the reaction pressure is usually in the range from 1 to 3 bar and the total space loading of the fixed catalyst bed with reaction gas B is preferably 1500 to 4000 or 6000 N / l-h or more.
  • the propylene load (the propylene load of the fixed catalyst bed) is typically 90 to 200 Nl / l-h or 300 Nl / l-h or more.
  • the single-zone multiple contact tube fixed bed reactor is supplied with the feed gas mixture from above.
  • a heat exchange agent is suitably a molten salt, preferably consisting of 60 wt .-% potassium nitrate (KNO 3 ) and 40% by weight of sodium nitrite (NaNO 2 ), or of 53% by weight of potassium nitrate (KNO 3 ),
  • molten salt and reaction gas mixture can be conducted both in cocurrent and countercurrent.
  • the molten salt itself is preferably guided meander-shaped around the catalyst tubes.
  • a bed of inert material (Section A), which is preferably chosen so that it causes the lowest possible pressure loss.
  • section C is undiluted.
  • the aforementioned feed variant is particularly useful if, as catalysts, those according to Research Disclosure No. 497012 of 29.08.2005, or according to Example 1 of DE-A 100 46 957 or according to Example 3 of DE-A 100 46 957 and as inert material rings made of steatite with the geometry 7 mm x 7 mm x 4 mm (outside diameter x height x inside diameter) can be used.
  • inert material rings made of steatite with the geometry 7 mm x 7 mm x 4 mm (outside diameter x height x inside diameter) can be used.
  • the salt bath temperature what has been stated in DE-A 4 431 957 applies.
  • Carrying out the partial oxidation in the reaction zone B, from propylene to acrolein (and, if appropriate, acrylic acid), can also be carried out with the catalysts described, for example.
  • the achieved With simple passage normally at values> 90 mol%, or:> 95 mo!% and the selectivity of acrolein formation at values:> 90 mol%.
  • the partial oxidation of propene according to the invention to acrolein, or acrylic acid or a mixture thereof is carried out as described in EP-A 1 159 244 and very particularly preferably as described in WO 04/085363 and in WO 04/085362.
  • reaction zone B a partial oxidation of propylene to acrolein (and optionally acrylic acid) to be carried out in reaction zone B can be carried out particularly advantageously on a fixed catalyst bed with increased propylene loading, which has at least two temperature zones.
  • the implementation of the second step in the case of a two-stage partial oxidation of propylene to acrolein, namely the partial oxidation of acrolein to acrylic acid, can be carried out with the described catalysts z.
  • a two-stage partial oxidation of propylene to acrolein namely the partial oxidation of acrolein to acrylic acid
  • Reaction gas mixture and heat transfer medium can be conducted in direct current over the reactor.
  • the product gas mixture of the preceding propylene partial oxidation according to the invention to give acrolein is basically as such (optionally after intermediate cooling (this can be done indirectly or directly by, for example, secondary oxygen (or less preferably secondary air) addition) thereof ), ie, without Maukomponentenabtrennung, in the second reaction stage, ie led to the acrolein partial oxidation.
  • the molecular oxygen required for the second step, the acrolein partial oxidation can already be present in the reaction gas B starting mixture for the propylene partial oxidation to the acrolein. However, it can also be partially or completely added directly to the product gas mixture of the first reaction stage, ie the propylene partial oxidation to acrolein (this can be in the form of secondary air, but preferably in the form of pure oxygen or mixtures of inert gas and oxygen (preferably ⁇ 50) Vol .-%, or ⁇ 40 Vol .-%, or ⁇ 30 Vol .-%, or ⁇ 20 Vol .-%, or ⁇ 10 Vol .-%, or ⁇ 5 Vol .-%, or ⁇ 2 Vol. -% respectively)).
  • the feed gas mixture (the reaction gas starting mixture) of such a partial oxidation of the acrolein to acrylic acid advantageously has the following contents: 3 to 25 vol.% Acroiein,
  • the aforementioned reaction gas starting mixture preferably has the following contents:
  • reaction gas starting mixture has the following contents:
  • the nitrogen content in the abovementioned mixtures is generally ⁇ 20% by volume, preferably ⁇ 15% by volume, more preferably ⁇ 10% by volume and very particularly preferably ⁇ 5% by volume.
  • the ratio of the molar amounts of O 2 and Acroiein, O 2: Acroiein present in the feed gas mixture for the second oxidation stage is advantageously in accordance with the invention generally> 0.5 and ⁇ 2, frequently> 1 and ⁇ 1.5.
  • the CO 2 content of the feed gas mixture for the second oxidation stage may be 1 to 40, or 2 to 30, or 4 to 20, or often 6 to 18, volume%.
  • the reaction pressure in the second reaction stage is usually in the range from 1 to 3 bar, and the total space load of the catalyst fixed bed with reaction gas (starting) mixture is preferably from 1500 to 4000 or 6000 Nl / l * h or more.
  • the acrolein load (the acrolein loading of the fixed catalyst bed) is typically 90 to 190 Nl / l'h, or to 290 Nl / lh or more.
  • Acroleinlasten above 135 Nl / l * h, or> 140 Nl / i * h, or> 150 Nl / lh, or> 160 Nl / lh are particularly preferred since the reaction gas starting mixture to be used according to the invention also causes favorable hot spot behavior due to the presence of propane and molecular hydrogen.
  • the Acroieinumsatz based on a single pass of the reaction gas mixture through the fixed catalyst bed of the second oxidation stage, is expedient normally> 90 mol% and the concomitant selectivity of acrylic acid formation> 90 mol%.
  • the single-zone multiple contact tube fixed bed reactor is also supplied with the feed gas mixture from above.
  • a salt melt preferably from 60% by weight of potassium nitrate (KNO 3 ) and 40% by weight of sodium nitrite (NaNO 2 ) or of 53% by weight of potassium nitrate (KNO 3 ) is expediently also used in the second stage. 40 wt .-% sodium nitrite (NaNO 2 ) and 7 wt .-% sodium nitrate (NaNO 3 ) consisting used.
  • molten salt and reaction gas mixture can be conducted both in cocurrent and countercurrent.
  • the molten salt itself is preferably guided in a meandering manner around the catalyst tubes.
  • a bed of inert material (section A), which is preferably selected so that it causes the lowest possible pressure loss.
  • section C is undiluted.
  • section B may also consist of two consecutive catalyst dilutions (for the purpose of minimizing hotspot temperature and hotspot temperature sensitivity). From bottom to top, first with up to 30 (or 20)% by weight of inert material and subsequently with> 20% by weight to 50% to 40% by weight of inert material. The section C is then preferably undiluted.
  • the aforementioned feed variant is particularly useful if, as catalysts, those according to Preparation Example 5 of DE-A 100 46 928 or those according to DE-A 198 15 281 and as inert material rings of steatite with the geometry 7 mm x 7 mm x 4 mm or 7 mm x 7 mm x 3 mm (in each case outside diameter x height x inside diameter) are used.
  • the statements made in DE-A 443 19 49 apply. It is usually chosen so that the achieved acro leinumsatz in simple passage is normally> 90 mol%, or> 95 mol% or> 99 mol%.
  • the execution of the partial oxidation of acrolein to acrylic acid can also be carried out with the catalysts described z.
  • the second reaction stage of a two-stage propylene partial oxidation to acrylic acid is also true for the acrolein conversion in a two-zone Vieicardrohr- fixed bed reactor is to produce the feed gas mixture (reaction gas starting mixture) expedient directly the product gas mixture of the first step (propylene ⁇ acrolein) directed partial oxidation (optionally after indirect or direct (eg., By supplying Seku ⁇ sarsstoff
  • the intermediate oxygen required for the acrolein partial oxidation is preferably as pure molecular oxygen (but optionally also as air or as a mixture of molecular oxygen and an inert gas m with an inert gas content of preferably ⁇ 50% by volume, particularly preferably ⁇ 40% by volume, or ⁇ 30% by volume, or ⁇ 20% by volume
  • the salt bath temperature of multi-contact tube reactors for the first step of the two-stage partial oxidation of propylene to acrylic acid is generally from 300 to 400.degree.
  • the Saizbad- temperature of Dahlmindrohrreaktoren for the second step of the partial oxidation of propylene to acrylic acid, the partial oxidation of acrolein to acrylic acid is usually 200 to 350 0 C.
  • the heat exchange agents preferably molten salts
  • both steps of the partial oxidation of propylene to acrylic acid but also as described in DE-A 101 21 592 can be carried out in a reactor on a feed.
  • part of the reaction gas B starting mixture for the first step can be residual gas I coming from separation zone I and residual gas I aftertreated according to the invention.
  • the abovementioned residual gases I are recirculated exclusively as recycle gas I into the heterogeneously catalyzed propane dehydrogenation in the reaction zone A and this expediently exclusively as constituent of the reaction gas A starting mixture.
  • both the feed gas mixture for the first oxidation stage and the feed gas mixture for the second oxidation stage or just one of both additional fresh propane can be added. It is not preferred according to the invention, but may optionally be expedient in order to exclude an ignitability of the feed gas mixtures.
  • a tube bundle reactor within which the catalyst feed along the individual contact tubes changes correspondingly upon completion of the first reaction step (such two-stage propylene partial oxidations in the so-called "Si ⁇ gle Reactor" are taught, for example, by EP-A 91 1 313, EP-A 979 813 EP-A 990 636 and DE-A 28 30 765) represent the simplest form of realization of two oxidation states for the two steps of the partial oxidation of propylene to acrylic acid
  • the charging of the catalyst tubes by catalyst is interrupted by an ion-exchange charge.
  • the two oxidation stages are realized in the form of two tube bundle systems connected in series. These can be in a reactor are located, wherein the transition from one tube bundle to the other tube bundle is formed by a not accommodated in the contact tube (suitably walkable) bed of Inertmateriai. While the contact tubes are generally lapped by a heat transfer medium, this does not reach an inert material charge as described above.
  • the two catalyst tube bundles are therefore advantageously accommodated in spatially separate reactors.
  • an intercooler is located between the two tube bundle reactors in order to reduce any possible acrolein afterburning in the product gas mixture leaving the first oxidation zone.
  • the reaction temperature in the first reaction stage is generally from 300 to 450 0 C, preferably at 320 to 390 ° C.
  • the reaction temperature in the second reaction stage is generally 200 to 370 0 C, often 220 to 33O 0 C.
  • the reaction pressure in both oxidation zones is suitably 0.5 to 5, preferably 1 to 3 bar.
  • the load (Nl / l » h) of the oxidation catalysts with reaction gas in both reaction stages is often 1500 to 2500 Nl /! « H or up to 4000 Nl / ih.
  • the loading with propylene or acrolein can be 100 to 200 or 300 and more liters per hour.
  • the two oxidation states in the process according to the invention can be designed as described, for.
  • DE-A 198 37 517 DE-A 199 10 506, DE-A 199 10 508 and DE-A 198 37 519 is described.
  • an excess of molecular oxygen relative to the amount required by the reaction stoichiometry advantageously has an effect on the kinetics of the respective gas phase partial oxidation and on the catalyst lifetime.
  • the heterogeneously catalyzed gas-phase partial oxidation of propylene to acrylic acid to be carried out according to the invention can also be carried out as follows, even in a single single-tube bundle reactor. Both reaction steps take place in an oxidation reactor which is charged with one or more catalysts whose active material is a multimetal oxide containing the elements Mo, Fe and Bi which is capable of catalyzing the reaction of both reaction steps. Of course, this catalyst feed can also change continuously or abruptly along the reaction coordinate.
  • a two-stage partial oxidation of propylene to acrylic acid in the form of two series-connected oxidation stages from the first oxidation stage leaving the product gas mixture contained selbigem in the first oxidation stage as a by-product, carbon monoxide and water vapor, if necessary, before forwarding in the second oxidation stage are partially or completely separated.
  • the product gas mixture contained selbigem in the first oxidation stage as a by-product, carbon monoxide and water vapor, if necessary, before forwarding in the second oxidation stage are partially or completely separated.
  • one will choose a procedure which does not provide such a separation.
  • sources of an oxygen feed between both oxidation stages are both pure molecular oxygen and inert gas such as CO 2 , CO, noble gases, N 2 and / or saturated Hydrocarbons diluted molecular oxygen into consideration.
  • the oxygen source preferably contains ⁇ 50% by volume, preferably ⁇ 40% by volume, more preferably
  • vol .-% ⁇ 30 vol .-%, most preferably ⁇ 20 vol .-%, better ⁇ 10 vol .-% or
  • the partial oxidation of acrolein to acrylic acid takes place as described in EP-A 1 159 246, and very particularly preferably as described in WO 04/085365 and in WO 04/085370.
  • a reaction gas starting mixture which is the product gas mixture of a first-stage partial oxidation of propylene to acrolein according to the invention which was optionally supplemented with sufficient secondary air that the ratio of molecular oxygen to acrolein in the resulting reaction gas starting mixture in in each case 0.5 to 1.5.
  • the documents EP-A 1 159 246, WO 04/08536 and WO 04/085370 are considered to be an integral part of this document.
  • the partial oxidation of acrolein to acrylic acid according to the invention can be advantageously carried out on a fixed catalyst bed with increased acrolein loading, which has at least two temperature zones.
  • a two-stage partial oxidation of propylene to acrylic acid is preferably carried out as described in EP-A 1 159 248 or in WO 04/085367 or WO 04/085369.
  • the product gas B leaving the inventive partial oxidation contains essentially acrolein, or acrylic acid, or their mixture as the target product, unreacted propane, molecular hydrogen, (by-produced product and / or diluent gas) Water vapor, optionally unreacted molecular oxygen (in view of the lifetime of the catalysts used, it is usually favorable if the oxygen content in the product gas mixture of both partial oxidati- onkilln z. B.
  • water vapor and heavy boiling water as secondary components are converted into the condensed phase and thus separated (according to the invention, a preferred amount of water vapor in the converted condensed phase, the at least 70 mol%, preferably at least 80 mol%, more preferably at least 90 mol% and particularly preferably at least 95 mol% of the formed in the reaction zone B (or particularly preferably the total contained in the product gas B) Amount of water vapor is.
  • aqueous solutions and / or organic solvents eg., Mixtures of diphenyl and diphenyl ether or of diphenyl, diphenyl ether and o-Dimethyiphthaiat
  • a residual gas which does not condense into the condensed phase normally remains, which comprises the components of the product gas B which are comparatively difficult to condense (lighter than water) usually especially those components whose boiling point at normal pressure (1 bar) ⁇ -30 0 C (their total content of the residual gas is usually> 60 vol .-%, often> 70 vol .-%, often> 80 vol.
  • These include primarily unreacted propane, molecular hydrogen, carbon dioxide, optionally unreacted propylene, optionally unreacted molecular oxygen and other secondary components which boil more easily than water, such as, for example, CO 2, but usually ⁇ 90% by volume.
  • the residual gas may also be acrylic acid, acro lein and / or H 2 O are contained According to the invention, the residual gas preferably contains ⁇ 10% by volume, advantageously ⁇ 5% by volume and with particular advantage ⁇ 3% by volume. -% Steam.
  • This aforementioned residual gas forms (based on the amount of propane contained therein) normally at least the main amount (usually at least 80%, or at least 90%, or at least 95% or more) of the residual gas formed in the first separation zone I and is in this document referred to as (main) residual gas I.
  • this unreacted propane and, optionally, propylene are usually recovered as a constituent of at least one further gas phase and in this document as (by the way) residual gas I denotes.
  • the sum of (main) residual gas I and (secondary) residual gas I forms the total amount of residual gas I. If no (minor) residual gas I is present in separation zone I, the (main) residual gas I is automatically the total amount Residual gas I (also called (total) residual gas I).
  • the conversion of the target product from the product gas B into the condensed phase preferably takes place by fractional condensation. This especially if the target product is acrylic acid. Basically, however, for target product separation z. All of the processes described in DE-A 102 13 998, DE-A 22 63 496, US Pat. No.
  • EP-A 1 388 533 and EP-A 1 388 532 DE -A 102 35 847, EP-A 792 867, WO 98/01415, EP-A 1 015 41 1, EP-A 1 015 410, WO 99/50219, WO 00/53560, WO 02/09839, DE-A 102 35 847, WO 03/041833, DE-A 102 23 058, DE-A 10243 625, DE-A 103 36 386, EP-A 854 129, US-A 4,317,926, DE-A 198 37 520, DE-A 196 06 877, DE-A 190 50 1325, DE-A 102 47 240, DE-A 197 40 253, EP-A 695 736, EP-A 982 287, EP-A 1 041 062, EP-A 1 171 46 DE-A 43 08 087
  • An acrylic acid removal can also be carried out as described in EP-A 982 287, EP-A 982 289, DE-A 103 36 386, DE-A 101 15 277, DE-A 196 06 877, DE-A 197 40 252, DE-A 196 27 847, EP-A 920 408, EP-A 1 068 174, EP-A 1 066 239, EP-A 1 066 240, WO 00/53560, WO 00 / 53561, DE-A 100 53 086 and EP-A 982 288 are made.
  • WO / 0196271 or as described in DE-A 10 2004 032 129 and their equivalent industrial property rights.
  • the aforementioned separation method is (as already mentioned) that z. B. at the top of the respective separating internals containing separation column, in the lower part of the product gas B, usually after prior direct and / or indirect cooling of the same, for. B. is fed, normally a stream of residual gas I remains, which contains mainly those components of the product gas B, whose boiling point at atmospheric pressure (1 bar) is lower than that of water and usually ⁇ -30 0 C (ie, the hardly condensable or volatile constituents). Residual gas I but z. B. also contain components such as water vapor and acrylic acid.
  • the heavier volatile constituents of the product gas B normally accumulate in the condensed phase.
  • Condensed aqueous phase is usually removed via side draw and / or sump.
  • (main) residual gas I contains the following contents:
  • the content of acrolein and acrylic acid is generally ⁇ 1 vol .-% in each case.
  • the inventors of the invention it is now necessary for the residual gas I obtained in the separation zone I to undergo certain after-treatment measures. It is invented According to the essential that the respective post-treatment measure does not necessarily have to be carried out on the total amount of residual gas I. D. h., It may be appropriate according to the invention, the Nachbehandlu ⁇ gsdorf ⁇ ahme only at a subset (eg., Only on (main) residual gas I) of the total amount of the residual gas! perform.
  • the sum of the untreated subset of the total amount of the residual gas I and of the residual gas remaining after the aftertreatment measure has been carried out on the other subset of the total amount of the residual gas I forms the total amount of residual gas I after-treated (the "new" Residual gas I) which can be subjected in a corresponding manner to further aftertreatment according to the invention (the abovementioned subsets may also have different chemical compositions.)
  • Total amount of (post-treated) unreacted propane remaining after completion of all aftertreatment measures deemed necessary in the respective case Residual gas I, according to the invention, at least one subset is recycled as at least one of the at least two propane-containing feed streams in the reaction zone A.
  • Another subset may gegeb If necessary, be recycled to the first and / or second oxidation stage of the reaction zone B, there to make as part of the respective feed gas, the explosion behavior of the reaction gas advantageous.
  • the amount of inventively post-treated residual gas I recycled to the reaction zone A as at least one of the at least two propane feeds is advantageously such that it is at least 80 mol%, preferably at least 85 mol%, better at least 90 mol%. %, or at least 92 mole%, or at least 94 mole%, or at least 96 mole%, or at least 98 mole% of the propane fed out from the reaction zone B with the product gas B.
  • this recycling does not necessarily take place at one and the same point of the reaction zone A. Rather, this can also be done via several different distributed over the reaction zone A supply points.
  • the sequence of the after-treatment measures carried out on residual gas I is arbitrary according to the invention. That is, instead of initially exhausting a partial amount of residual gas I and then subjecting the remaining amount of a CCb scrubbing, z. B. also be done first CCh scrubbing and from the thus washed residual gas ⁇ a subset be omitted.
  • the subsequent sequence of after-treatment measures will be adhered to (they relate in particular to the aftertreatment of the (main) residual gas I).
  • a partial amount of residual gas I will be discharged (the outlet is especially required to discharge inert components introduced with the supply of molecular oxygen to the overall process).
  • This discharged amount (usually the omitted amount of residual gas I is supplied to an exhaust gas combustion) can have the same composition as the residual gas I itself.
  • ⁇ 5 mol% and very particularly preferably ⁇ 3 mol% or ⁇ 1 mol%.
  • the outlet can also be carried out such that the propane present in the amount of residual gas I to be omitted and, if appropriate, propylene, beforehand the outlet from the outlet quantity separates, so thus separated propane and optionally propylene remains part of inventively post-treated residual gas I.
  • a simple way for the aforementioned separation is z. B. therein, the corresponding amount of residual gas I with a (preferably high-boiling) organic solvent (preferably a hydrophobic, eg., Tetradekan or mixtures of C 8 -C 2 o-AJkanen) in which propane and propylene (compared to the other Constituents of the residual gas I are expediently preferred) to bring into contact (for example by simply passing through).
  • a (preferably high-boiling) organic solvent preferably a hydrophobic, eg., Tetradekan or mixtures of C 8 -C 2 o-AJkanen
  • propane and propylene compared to the other Constituents of the residual gas I are expediently preferred
  • the propane and (optionally) recovered propylene and added to the post-treated residual gas I By subsequent desorption (under reduced pressure), distillation and / or stripping with a non-interfering in the reaction zone A gas (eg., Water vapor, molecular hydrogen, molecular oxygen and / or other Inerigas (eg., Air)) the propane and (optionally) recovered propylene and added to the post-treated residual gas I.
  • a gas eg., Water vapor, molecular hydrogen, molecular oxygen and / or other Inerigas (eg., Air)
  • the propane and (optionally) recovered propylene and added to the post-treated residual gas I In detail, it is possible to proceed as in the analogous absorptive separation of propane from product gas A as described in DE-A 10 2004 032 129. If the separation described above, which is less preferred according to the invention, is carried out in the process according to the invention, it will always extend only to a partial amount of residual gas I and thus only to a
  • the CO 2 scrubbing is carried out at elevated pressure (typically 3 to 50 bar, more preferably 5 to 30, preferably 8 to 20, particularly preferably 10 to 20 or 15 bar) and, according to the invention, expediently by means of a basic (in Brönsted ' sense) liquid.
  • organic amines such as monoethanol amine
  • aqueous solutions of organic amines such.
  • aqueous solutions come z.
  • solutions of K 2 CO 3 in water, or of K 2 CO 3 and KHCO 3 in water or of K 2 CO 3 , KHCO 3 and KOH in water are examples of solutions of K 2 CO 3 in water, or of K 2 CO 3 and KOH in water.
  • Such an aqueous potassium carbonate solution advantageously has a solids content of from 10 to 30 or 40% by weight, particularly preferably from 20 to 25% by weight.
  • alkali metal hydroxide eg KOH
  • the aqueous alkali carbonate solution may additionally be made alkaline prior to washing in order to neutralize optionally present carboxylic acids (eg acetic acid, formic acid, acrylic acid) in the residual gas I.
  • carboxylic acids eg acetic acid, formic acid, acrylic acid
  • Cheap aqueous washing solutions are also those which contain dissolved KHCO 3 and K 2 CO 3 in a weight ratio of about 1: 2, where you
  • Solid content with advantage 20 to 25 wt .-% is. Taking up CO 2 and water, a molar unit of K 2 CO 3 is converted into two molar units of KHCO 3 (K 2 CO 3 + H 2 O + CO 2 ⁇ 2 KHCO 3 ) during the wash.
  • the CO 2 scrubbing z. B. also under CO 2 clathrate formation according to the teaching of EP-A 900 121 performed.
  • the CO 2 scrubbing is carried out in a scrubbing column and in a countercurrent flow.
  • the residual gas I to be washed generally flows from the bottom to the top in the scrubbing column and the scrubbing liquid from above to below.
  • the scrubbing column contains internals which increase the exchange surface area. These can be fillers, mass transfer trays (eg sieve trays) and / or packings.
  • the washed residual gas I is advantageously omitted and from the bottom of the wash column z.
  • the aqueous, predominantly containing potassium hydrogen carbonate solution or an aqueous solution of CO2 Clathrat
  • the sump solution may contain KHCO3 and K2CO3 dissolved in a weight ratio of 2.5: 1.
  • the bicarbonate By introducing hot steam into the aqueous potassium bicarbonate solution, the bicarbonate can be split back thermally (in carbonate and CO2, H2O) and the released CO2 can be expelled.
  • the aqueous potassium carbonate solution thus recovered can, as a rule after evaporation of water vapor condensed in the course of the cleavage, be recycled to the CO 2 scrubber to be carried out as described.
  • the evaporation of the condensing water vapor can also be operated continuously by evaporators integrated in the column.
  • the above cleavage is also carried out in an expedient manner in a column containing the insert surface enlarging the exchange surface (eg (sieve) tray column, packed column and / or packed column).
  • An advantage here too is the countercurrent operation.
  • the hot steam is advantageously supplied in the lower part of the column and the aqueous potassium carbonate solution is advantageously abandoned on Kolo ⁇ enkopf.
  • the bicarbonate cleavage is preferably carried out at elevated temperatures.
  • the cleavage is carried out appropriately by means of steam having a temperature of 130 to 16O 0 C, preferably from 140 to 150 0 C.
  • the gurzuspaltende aqueous solution is expedient abandoned at a temperature of 80 to 120 0 C, particularly preferably from 90 to 1 10 0 C.
  • the residual gas I according to the invention advantageously at a temperature of 60 to 90 ° C, more preferably 70 to 8O 0 C in the wash column, and the washing liquid at a temperature of 70 to 9O 0 C, preferably 75 to 85 ° C, abandoned ,
  • the residual gas I ver ⁇ Tren ⁇ zone I in the process according to the invention with a pressure of> 1 bar and ⁇ 2.5 bar, preferably ⁇ 2.0 bar.
  • the heterogeneously catalyzed dehydrogenation in the reaction zone A is advantageously carried out at a pressure of> 2 to ⁇ 4 bar, preferably> 2.5 to ⁇ 3.5 bar.
  • the reaction zone B is inventively operated at a pressure of> 1 bar and ⁇ 3 bar, preferably> 1, 5 and ⁇ 2.5 bar.
  • the preferred working pressures for the CO 2 scrubbing are 3 to 50 bar, or 5 to 30 bar, or 8 to 20 bar, preferably 10 to 20 or to 15 bar.
  • turbocompressor radial compressor, eg of the type MH4B, the company Mannesmann DEMAG, DE
  • recycle gas I compressor a compression of the residual gas I to the working pressure in the reaction zone A carried out (eg , 2 to 3.2 bar).
  • the residual gas I compressed as described is expediently divided into two aliquots of identical composition.
  • the quantitative fractions can be z. B. amount to 70 to 30% of the total amount.
  • the subset that is not to be subjected to the CO ⁇ wash is ready to be returned to the reaction zone A.
  • Such a heat exchange can also be applied before the first expansion.
  • condensation of water vapor which may also be present therein may occur in the residual gas I.
  • the aforementioned expansions are advantageously carried out in (advantageously also multi-stage) expansion turbines (this serves to recover compaction energy).
  • the difference between input and output pressure z. B. 2 to 10 bar In general, at least 50 mol%, usually at least 60 mol%, or at least 80 mol% and often at least or more than 90% by volume of the CO contained in the residual gas I are washed out in the separation zone II.
  • the washed-out CO 2 amount corresponds to the total amount of CO 2 formed in the reaction zones A and B.
  • CCV-washed residual gas still contains 1 to 20, often 5 to 10% by volume of CO 2 .
  • suitable separation membranes are z.
  • the hydrogen permeation rate for H2 at 6O 0 C for this membrane is 0.7 * 10 3 [STP * cc / cm 2 * sec * cm Hg].
  • the C ⁇ 2 -washed residual gas I can be passed over the membrane, which is usually designed to form a tube (but it is also possible to use a plate or a wound module) which is permeable only to the molecular hydrogen.
  • the thus separated molecular hydrogen can be used in the context of other chemical syntheses or z. B. together with discharged in the context of the process according to the invention residual gas I combustion. In this combustion, the released CO 2 (it can also be easily released into the atmosphere) and the aqueous condensates formed in the separation zones I and II can be included.
  • the aforementioned combustion the separated in the Tre ⁇ nzone I high boilers can be supplied.
  • the combustion takes place under air supply.
  • the execution of the combustion can, for. B. as described in EP-A 925 272.
  • the membrane separation of molecular hydrogen is preferably also carried out under high pressure (eg 5 to 50 bar, typically 10 to 15 bar).
  • tubular membranes are particularly suitable for hydrogen separation.
  • Your inner diameter can z. B. a few microns to a few mm.
  • Analogous to the tubes of a tube bundle reactor is z. B. cast a bundle of such tubular membranes at the two hose ends in each case a plate. Outside the tube membrane there is preferably a reduced pressure ( ⁇ 1 bar).
  • the residual gas I which is under elevated pressure (> 1 bar), is guided against one of the two plate ends and forced through the tube interior to the hose outlet located at the opposite end of the plate. Along the flow path predetermined in the interior of the tube, molecular hydrogen is released to the outside via the H ⁇ -permeable membrane.
  • the residual gas i treated as described (sum of aftertreated partial amount and, if appropriate, not post-treated partial amount) can be recycled as required into the reaction zone A as one of the feed streams containing at least two gaseous propane.
  • the total amount of residual gas I aftertreated according to the invention is preferably fed to the reaction gas A starting mixture (to the feed gas mixture of the reaction zone A).
  • a method according to the invention preference is given to a method according to the invention in which the highest working pressure level is present in the process step of the CO 2 scrubbing of the residual gas I.
  • This allows, as described, the implementation of the method according to the invention with the concomitant use of only one compressor (preferably a multistage centrifugal compressor), which is to be positioned between the formation of residual gas I and CCV scrubbing of residual gas I.
  • the process of the invention does not necessarily require the concomitant use of another compressor, as shown.
  • a further compressor can be integrated into the method according to the invention.
  • reaction gas A feed mixture fed to the reaction zone A naturally contains molecular hydrogen which protects the hydrocarbon contained in this starting mixture from combustion with molecular oxygen present in this mixture at the same time. Based on converted fresh propane, this results in comparatively high target product selectivities.
  • a basis of the method according to the invention is that the non-inert secondary components which are formed during the course of the process according to the invention or introduced into the same, their outlet in a natural manner in the in the separation zones I and II of the erfi ⁇ - inventive method have formed condensates.
  • recycle gas recirculated to reaction zone A contains i:
  • polymerization inhibitors are added both in the separation zone I a and in the separation zone II whenever condensed phases occur.
  • basically all known process inhibitors come into consideration.
  • According to the invention are particularly suitable for.
  • phenothiazine and the methyl ether of hydroquinone As phenothiazine and the methyl ether of hydroquinone. The presence of molecular oxygen increases the effectiveness of the polymerization inhibitors.
  • Acrolein produced by the process of the present invention can be converted into the acrolein products mentioned in US-A-6,166,263 and US-A-6,118,793.
  • Exemplary acrolein derivatives are 1, 3-propanediol, methionine, glutaraldehyde and 3-picoline.
  • the reactor consisted of a doppelwa ⁇ digen cylinder made of stainless steel (cylindrical guide tube, surrounded by a cylindrical outer container).
  • the wall thicknesses were anywhere from 2 to 5 mm.
  • the inner diameter of the outer cylinder was 91 mm.
  • the inner diameter of the guide tube was about 60 mm.
  • the contact tube 400 cm total length, 26 mm inner diameter, 30 mm outer diameter, 2 mm wall thickness, stainless steel
  • the heat exchange medium salt melt consisting of 53% by weight potassium nitrate, 40% by weight sodium nitrite and 7% by weight sodium nitrate
  • the heat exchange medium was enclosed in the cylindrical container.
  • the heat exchange medium was circulated by means of a propeller pump.
  • the temperature of the heat exchange could be controlled to the desired level. Otherwise, there was air cooling.
  • Reactor Charge Viewed over the first stage reactor, the molten salt and charge gas mixture of the first stage reactor were passed in cocurrent. The feed gas mixture entered the bottom of the first stage reactor. It was in each case conducted into the reaction tube at a temperature of 165 0 C.
  • the salt melt stepped down to a temperature T e ⁇ in the cylindrical guide tube and a top having a temperature of T from the cylindrical guide tube, which was 0 C above T in up to the second
  • T e ⁇ n was adjusted so that always resulted in the output of the first oxidation stage, a propylene conversion of 97.8 ⁇ 0.1 mol% in a single pass.
  • Section A 90 cm in length
  • Section B 100 cm in length
  • Section D 10 cm in length
  • the product gas mixture leaving the first fixed bed reactor was passed through a connecting tube (40 cm length, 26 mm inner diameter, 30 mm outer diameter, 2 mm wall thickness, stainless steel wound with 1 cm insulating material), centered on a length of 20 cm, charged with an inert bed of steatite rings of geometry 7 mm ⁇ 3 mm ⁇ 4 mm (outer diameter ⁇ length ⁇ inner diameter) and flanged directly onto the first-stage contact tube.
  • a connecting tube 40 cm length, 26 mm inner diameter, 30 mm outer diameter, 2 mm wall thickness, stainless steel wound with 1 cm insulating material
  • the product gas mixture always entered with a temperature of> T ei ⁇ (first stage) in the connecting pipe and left it with a temperature above 200 0 C and below located 270 0 C temperature.
  • molecular oxygen present at the pressure level of the product gas mixture was metered into the cooled product gas mixture.
  • the resulting gas mixture (charge gas mixture for the second oxidation stage) was led directly into the second-stage contact tube, to which the above-mentioned connecting tube with its other end was likewise flanged.
  • the amount of molecular oxygen metered in was such that the molar ratio of O 2 present in the resulting gas mixture to acrolein 1, 3 in the resulting gas mixture was.
  • a contact-tube fixed-bed reactor was used, which was identical to that for the first oxidation stage. Saizschmelze and feed gas mixture were viewed over the reactor viewed in DC. The molten salt entered at the bottom, the feed gas mixture also. The inlet temperature T of a Saizschmelze was adjusted so that the output of the second oxidation stage is always an acrolein Turnover of 99.3 ⁇ 0.1% mono-passage yielded. T from the molten salt was up to 2 0 C above T ei ⁇ .
  • the contact tube charge (from bottom to top) was:
  • Section A 70 cm in length
  • Section B 100 cm in length
  • Section D 30 cm in length
  • composition of the feed gas mixture for the first oxidation stage was essentially:
  • T is a (second oxidation stage): 268 0 C.
  • T is a (first oxidation stage): 330 0 C.
  • composition of the feed gas mixture for the first oxidation stage was essentially:
  • T is a (first oxidation stage): 324 0 CT ei ⁇ (second oxidation stage): 276 ° C
  • the reaction zone A consists of a designed as Horde ⁇ reaktor and adiabatic shaft furnace reactor having three arranged in the flow direction one behind the other fixed catalyst beds.
  • the dehydrogenation catalyst is a Pt / Sn alloy containing the elements Cs, K and La in oxidic form. 6 mm, diameter: 2 mm) in the elemental stoichiometry (average length (gauss distributed in the range of 3 mm to 12 mm with maximum at about 6 mm): 6 mm, diameter: 2 mm) (Mass ratio including support) Pto, 3Sno, 6La3, oCso, 5Ko, 2 (ZrO2) s8,3 (SiO 2) 7, i is applied (catalyst precursor preparation and activation to the active catalyst as in Example 4 of DE-A 102 19 879) ).
  • the heterogeneously catalyzed partial propane dehydrogenation is carried out in the described tray reactor in a straight pass.
  • the load of the total amount of catalyst (calculated without inert material) of all hordes with propane is 1500 Nl / l « h.
  • the condensate which has cooled down can be used further in the separation zone I for acid water condensation (for example in the context of direct cooling as a coolant).
  • the steam is available at a temperature of 152 ° C and 5 bar.
  • the bed height of the first catalyst bed through which the reaction gas A starting mixture flows is such that the reaction gas A of this catalyst bed at a temperature of 549 ° C. and a pressure of 2.91 bar gives the following contents: Propane 59.0 vol.%,
  • the maximum temperature in the first catalyst bed is 592 ° C.
  • the leaving amount is 63392 Nm 3 / h. 986 Nm 3 / h of molecular oxygen (purity> 99% by volume) are metered into the reaction gas A behind the first catalyst bed.
  • the oxygen is preheated to 176 ° C. It is throttled at a pressure of 3.20 bar located, so that the resulting pressure of the resulting reaction gas A was still 2.91 bar,
  • the bed height of the second catalyst bed is such that the reaction gas A leaves the second catalyst bed at a temperature of 566 ° C. and a pressure of 2.90 bar with the following contents:
  • the maximum temperature in the second catalyst bed is 595 0 C.
  • the bed height of the third catalyst bed is such that the reaction gas A leaves the third catalyst bed as product gas A with a temperature of 581 ° C. and a pressure of 2.88 bar with the following contents: Propane 47.19 Vol .-%,
  • the maximum temperature in the third catalyst bed is 612 ° C.
  • the leaving quantity is 68522 Nm 3 / h.
  • the product gas A is cooled to a temperature of 290 ° C.
  • the first oxidation stage is a two-zone multi-tube reactor.
  • the reaction tubes are as follows: V2A steel; 30 mm outer diameter, 2 mm wall thickness, 26 mm inner diameter, length: 350 cm. From top to bottom, the reaction tubes are charged as follows:
  • Section 1 50 cm in length
  • Length x inner diameter as a feed.
  • Section 2 140 cm in length
  • Section 3 160 cm in length
  • Catalyst charge with annular (5 mm ⁇ 3 mm ⁇ 2 mm outer diameter ⁇ length ⁇ inner diameter) unsupported catalyst according to Example 1 of DE-A 100 46 957 (stoichiometry: [Bi 2 W 2 ⁇ 9x 2 W 0 3 ] o, 5 [M ⁇ i 2 Co 5 , 5 Fe 2 94Sii, 59Ko, o8 ⁇ ] i).
  • the first 175 cm are thermostated by means of a salt bath A pumped in countercurrent to the reaction gas B.
  • the second 175 cm are thermostated by means of a salt bath B pumped in countercurrent to the reaction gas B.
  • the second oxidation stage is also a multi-tube reactor having two temperature zones.
  • the reaction tubes are charged from top to bottom as follows:
  • Section 1 20 cm in length
  • Length x inner diameter as a feed.
  • Section 2 90 cm in length
  • Section 3 50 cm in length
  • Section 4 190 cm in length
  • the first 175 cm are thermostated by means of a salt bath C pumped in countercurrent to the reaction gas.
  • the second 175 cm are thermostated by means of a salt bath D pumped in countercurrent to the reaction gas.
  • a shell-and-tube heat exchanger cooled by salt bath, with which the product gas of the first oxidation stage can be cooled.
  • a valve for the supply of molecular oxygen purity> 99 vol .-%).
  • the propylene loading of the catalyst feed of the first oxidation stage is selected to be 145 Nl / lh.
  • the salt melts (53% by weight of KNO 3 , 40% by weight of NaNO 2 , 7% by weight of NaNO 3 ) have the following entering temperatures:
  • the product gas mixture of the first oxidation stage is metered in as much molecular oxygen (17 ° C., 3.20 bar) that the molar ratio of O 2: acrolein in the resulting feed gas mixture for the second oxidation stage is 1.25.
  • the acrolein loading of the catalyst charge of the second oxidation stage is 140 Nl / lh.
  • the pressure at the inlet of the second oxidation stage is 1.61 bar.
  • the reaction gas leaves the intercooler at a temperature of 260 0 C and the inlet temperature of the feed gas mixture in the second oxidation stage is 258 0 C.
  • the product gas mixture of the first oxidation state has the following contents:
  • the temperature of the product gas of the first oxidation stage before entry into the aftercooler is 335 ° C.
  • the product gas mixture of the second oxidation stage (the product gas B) has a temperature of 27O 0 C and a pressure of 1, 55 bar and the following contents:
  • the product gas B is fractionally condensed as described in WO 2004/035514 in a tray column (separation zone I).
  • the residue combustion is fed as the first fuel 1 18 kg / h of high boilers (polyacrylic acids (Michael adducts), etc.).
  • the amount of acid water condensate withdrawn from the third collecting tray above the feed of the product gas B into the condensation column and not returned to the co-condensation column is 18145 kg / h, has a temperature of 33 ° C. and has the following contents:
  • residual gas I The residual amount of the residual gas I (hereinafter linguistically simplified still called “residual gas I") are compressed in the first compressor stage of a multistage radial compressor from 1.20 bar to 3.20 bar, the temperature of the residual gas I rises to 92 0 C.
  • the residual gas I is then divided into two halves of identical composition: one half directly forms a subset of the recycle gas I returned to the reaction zone A.
  • the other half of the residual gas I is compressed from 3.20 bar to 5.80 bar in a second compressor stage It heats up to 127 ° C. In an indirect heat exchanger, it is cooled to 78 ° C.
  • the residual gas cooled without condensation from 78 ° C to 54 ° C.
  • the residual gas I is compressed from 5.80 bar to 12.0 bar, wherein it is heated from 54 ° C to 75 ° C.
  • the residual gas I thus compressed is fed into the lower part of a packed column (separating zone II).
  • separating zone II At the top of this wash column 18000 kg / h of an aqueous K 2 C ⁇ 3 solution are introduced, which has a temperature of 82 ° C and contains phenotiazion as a polymerization inhibitor.
  • CO 2 - washed residual gas I At the top of the wash column escapes CO 2 - washed residual gas I, which has the following contents at a pressure of 12.00 bar and a temperature of 85 0 C:
  • the residual gas I (24461 Nm 3 / h) is now expanded from 12.00 bar to 4.25 bar and cooled from 85 ° C to 42 ° C.
  • the CO 2 -washed and H2 depleted residual gas heats up! from 42 ° C to 97 ° C and is recycled together with the other half of the fractional condensation of the product gas B remaining (not CO 2 -washed) residual gas I as recycle gas I into the reaction gas A-starting mixture for Reaktio ⁇ szone A.
  • the permeate stream (67.2 Nm 3 / h) has the following contents:
  • the escaping CO 2 is fed as the fifth fuel of the common Verbren ⁇ ungsstrom. From the outlet of the back-column (32968 kg / h) 14968 kg / h of water are evaporated. The remaining amount is (optionally post-neutralized with KOH) as a washing solution recycled to the top of the CO 2 - scrubbing column.
  • the fuels 1 to 5 are burned together with the addition of air (17674 Nm 3 / h) in an incinerator.

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
  • Low-Molecular Organic Synthesis Reactions Using Catalysts (AREA)

Abstract

L'invention concerne un procédé de production d'acroléine ou d'acide acrylique ou d'un mélange de ceux-ci, en tant que produit cible, à partir de propane. Selon ce procédé, du propane est partiellement soumis à une déshydrogénation catalytique hétérogène dans une zone de réaction A, l'hydrogène moléculaire formé étant en partie brûlé en eau, puis le produit gazeux A formé dans la zone de réaction A est utilisé, sans séparer les constituants secondaires, pour alimenter une zone de réaction B dans laquelle le propylène contenu dans le produit gazeux A est en partie oxydé afin d'obtenir le produit cible. Le produit cible est séparé du produit gazeux B formé dans la zone de réaction B, puis le gaz résiduaire restant I est ramené à la zone de réaction A après avoir été soumis à un traitement ultérieur comprenant un lavage au CO<SUB>2</SUB> et une évacuation partielle.
EP06778269A 2005-11-24 2006-08-17 Procede de production d'acroleine, d'acide acrylique ou d'un melange de ceux-ci a partir de propane Withdrawn EP1951650A1 (fr)

Applications Claiming Priority (5)

Application Number Priority Date Filing Date Title
DE102005056377A DE102005056377A1 (de) 2005-11-24 2005-11-24 Verfahren zur Herstellung von Acrolein, oder Acrylsäure, oder deren Gemisch aus Propan
US73942205P 2005-11-25 2005-11-25
US74028405P 2005-11-29 2005-11-29
DE200510057197 DE102005057197A1 (de) 2005-11-29 2005-11-29 Verfahren zur Herstellung von Acrolein, oder Acrylsäure, oder deren Gemisch aus Propan
PCT/EP2006/065416 WO2007060036A1 (fr) 2005-11-24 2006-08-17 Procede de production d'acroleine, d'acide acrylique ou d'un melange de ceux-ci a partir de propane

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EP1951650A1 true EP1951650A1 (fr) 2008-08-06

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DE102007055086A1 (de) 2007-11-16 2009-05-20 Basf Se Verfahren zur Herstellung von Acrylsäure
DE102007004960A1 (de) 2007-01-26 2008-07-31 Basf Se Verfahren zur Herstellung von Acrylsäure
DE102010048405A1 (de) 2010-10-15 2011-05-19 Basf Se Verfahren zum Langzeitbetrieb einer heterogen katalysierten partiellen Gasphasenoxidation von Proben zu Acrolein
WO2018003289A1 (fr) * 2016-06-30 2018-01-04 東亞合成株式会社 Procédé de production d'acide acrylique
EP3770145A1 (fr) 2019-07-24 2021-01-27 Basf Se Processus de production continue soit d'acroléine soit d'acide acrylique comme produit cible à partir de propène
WO2023006503A1 (fr) 2021-07-28 2023-02-02 Basf Se Procédé de production d'acide acrylique

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CA1217502A (fr) * 1982-04-14 1987-02-03 Sargis Khoobiar Conversion d'alkenes en aldehydes insatures
JP3348109B2 (ja) * 1992-01-02 2002-11-20 コノコ・インコーポレーテッド 水酸化ナトリウムで陽イオン交換樹脂からアルカノールアミンを選択的に再生するためのモニターおよび制御システム
DE59603316D1 (de) * 1995-03-10 1999-11-18 Basf Ag Verfahren zur Herstellung von Acrolein, Acrylsäure oder deren Gemisch aus Propan
JP2001342164A (ja) * 2000-03-30 2001-12-11 Mitsubishi Chemicals Corp アルデヒド類の製造方法
DE10028582A1 (de) * 2000-06-14 2001-12-20 Basf Ag Verfahren zur Herstellung von Acrolein oder Acrylsäure oder deren Gemischen aus Propan
GB0020523D0 (en) * 2000-08-18 2000-10-11 Bp Chem Int Ltd Process
JP2003261465A (ja) * 2002-03-06 2003-09-16 Mitsubishi Heavy Ind Ltd 有機ハロゲン化物処理設備
DE10246119A1 (de) * 2002-10-01 2004-04-15 Basf Ag Verfahren zur Herstellung von wenigstens einem partiellen Oxidations- und/oder Ammoxidationsprodukt des Propylens
DE10245585A1 (de) * 2002-09-27 2004-04-08 Basf Ag Verfahren zur Herstellung von wenigstens einem partiellen Oxidations- und/oder Ammoxidationsprodukt des Propylens
DE102006000996A1 (de) * 2006-01-05 2007-07-12 Basf Ag Verfahren der heterogen katalysierten Gasphasen-Partialoxidation wenigstens einer organischen Ausgangsverbindung
EP2004578B1 (fr) * 2006-03-30 2014-09-03 Basf Se Procédé de déshydrogénation partielle par catalyse hétérogène d'au moins un hydrocarbure à déshydrogéner

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JP5260300B2 (ja) 2013-08-14

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