EP1202799A1 - Zinc oxide-based dehydrogenating catalysts - Google Patents

Zinc oxide-based dehydrogenating catalysts

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Publication number
EP1202799A1
EP1202799A1 EP00951346A EP00951346A EP1202799A1 EP 1202799 A1 EP1202799 A1 EP 1202799A1 EP 00951346 A EP00951346 A EP 00951346A EP 00951346 A EP00951346 A EP 00951346A EP 1202799 A1 EP1202799 A1 EP 1202799A1
Authority
EP
European Patent Office
Prior art keywords
catalyst
catalysts
particularly preferably
dehydrogenation
sodium
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.)
Withdrawn
Application number
EP00951346A
Other languages
German (de)
French (fr)
Inventor
Heinz Peter Meier
Bernd Pennemann
Andreas Schulze-Tilling
Jörg Dietrich JENTSCH
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Bayer AG
Original Assignee
Bayer AG
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Bayer AG filed Critical Bayer AG
Publication of EP1202799A1 publication Critical patent/EP1202799A1/en
Withdrawn legal-status Critical Current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
    • C07C45/002—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by dehydrogenation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/06—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of zinc, cadmium or mercury
    • B01J35/30—
    • B01J35/612—
    • B01J35/613—
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/0009—Use of binding agents; Moulding; Pressing; Powdering; Granulating; Addition of materials ameliorating the mechanical properties of the product catalyst

Definitions

  • the present invention relates to dehydrogenation catalysts based on zinc oxide as an active component and their use in the dehydrogenation of secondary alcohols to the corresponding ketones.
  • DE-A-19626587 discloses a process for the preparation of cyclohexanone by dehydrogenation over a catalyst containing Cu as the active component and Al 2 O 3 as the carrier. Such catalysts generally allow lower reaction temperatures than those without copper.
  • EP-A-0204 046 describes a process for the preparation of cyclohexanone in which a catalyst consisting of copper, zinc oxide and an alkali metal compound, preferably sodium carbonate, is used for the dehydrogenation.
  • a catalyst consisting of copper, zinc oxide and an alkali metal compound, preferably sodium carbonate.
  • the selectivities of such catalysts are often low, but this is due to suitable ones
  • the reaction temperature is regularly associated with a significantly accelerated aging of the catalysts due to sintering of the copper, which leads to uneconomically short lifetimes for the catalysts used in this way.
  • DE-A-1443462 describes catalysts for the dehydrogenation of cyclohexanol which are prepared by precipitation of zinc salt solution with basic precipitation agents. No information is given on the Na content of the catalysts.
  • DE-A-19609954 describes a process for the dehydrogenation of secondary ones
  • Alcohols known at elevated temperature in the gas phase As a catalyst a mixture of zinc oxide and calcium carbonate is used. The catalyst is obtained by precipitating zinc and calcium nitrate with sodium carbonate, filtering off, washing free of nitrates and drying the filter cake. The product is then calcined and pressed into shaped articles.
  • a selectivity that enables the economical use of this method is only obtained when the in the
  • Dianon is an undesirable by-product in all known processes of the prior art.
  • the object of the present invention was therefore to find a catalyst for a process in which secondary ketones, preferably cyclohexanone, can be obtained with high selectivities and high conversions.
  • the catalyst should have a sufficient service life.
  • secondary alcohols are dehydrated in the presence of a catalyst which consists of zinc oxide with 0.1 to 0.6% by weight sodium, at elevated temperature in the gas phase.
  • cycloaliphatic alcohols and secondary aliphatic alcohols, preferably cyclohexanol can be used as alcohols.
  • Catalysts which contain 0.1 to 3, preferably 0.1 to 0.6% sodium are preferred.
  • Catalysts with 0.15 to 0.4% sodium are particularly preferred.
  • the specific BET surface area is preferably between 5 and 30 m 2 / g, particularly preferably 8 to 20 m 2 / g.
  • a catalyst according to the invention can be obtained by precipitation of a sparingly soluble zinc compound from water-soluble zinc compounds with a base and subsequent processing of the precipitate in a manner familiar to the person skilled in the art.
  • a preparation according to the invention consists, for example, in using aqueous sodium carbonate solution and adding zinc sulfate.
  • the precipitate is filtered off, washed, dried and then not calcined above 650 ° C.
  • the product obtained is optionally ground up and pressed to give shaped articles, for example by mixing it with a tabletting aid and tableting on a tablet machine.
  • aqueous zinc salt solutions For example, zinc sulfate, zinc nitrate, zinc chloride or zinc acetate can be used as zinc salts. Zinc sulfate and zinc chloride are preferred.
  • water-soluble sodium salts such as sodium hydroxide, sodium hydrogen carbonate or sodium carbonates can be used for the precipitation, sodium carbonate and sodium hydroxide being preferred.
  • One of the two salts preferably the base
  • a preparation is described, for example, in DE-A-3900243.
  • the temperature is usually selected in the range from 20 to 90 ° C., preferably from 50 to
  • both salt solutions are metered into a vessel at the same time, the addition being controlled in such a way that a constant pH value is established in the vessel.
  • a pH value during the precipitation of 6 to 9 is preferred.
  • the precipitate is filtered off, washed and dried. The washing is preferably carried out in a continuous manner in such a way that still in the calcined catalyst precursor
  • washable sodium particularly preferably 0.15 to 0.4% washable sodium are contained.
  • the amount of sodium which can be washed out is determined by determining the Na content before and after washing the catalyst precursor with 100 l of distilled water per kg of catalyst precursor. When washing the catalyst precursor, care should be taken to completely wash out the anion of the zinc salt used, since these can adversely affect the selectivity of the catalyst according to the invention.
  • the amount of sodium is added to the processed powder in a targeted manner, for example by pasting the precipitated product obtained with the base solution, for example a sodium carbonate solution, and then drying it.
  • the concentration of the solution is chosen so that the catalyst has the sodium content according to the invention.
  • the washing step is particularly important since it is possible to influence the sodium content of the catalyst, which is easily accessible to those skilled in the art, for example, through elemental analysis.
  • the powder obtained can optionally be pre-calcined, preferably in a spray dryer.
  • the powder is then subjected to a shaping step and the product is calcined, the calcining conditions and, in particular, the temperature being selected such that the resulting catalyst has a BET specific internal surface area of at least 5 and at most 30 m 2 / g, particularly preferably 8 up to 20 m 2 / g.
  • the higher the calcination temperatures and / or the longer the calcification times the smaller the specific surface area. If necessary, the order of shaping and calcining can also be reversed.
  • calcination is carried out, the product obtained is mixed with 0.1 to 5% by weight, preferably 1 to 5% by weight, particularly preferably 2 to 5% by weight of auxiliaries, and the product obtained is pressed to give shaped articles , such as tablets, asterisks, rings, split, wagon wheels, balls, preferably tablets.
  • Graphite is preferred as a tabletting aid, synthetic graphite being particularly preferred because of its higher purity, as one should avoid contamination of the catalyst at all during the processing steps. In general, care should be taken not to allow any metal oxides which the person skilled in the art is aware of to have acidic properties to get into the catalyst. This includes, for example, activated aluminum oxide. They are calcined Tablets so that the BET specific internal surface area of at least 5 and at most 30 m 2 / g, particularly preferably 8 to 20 m 2 / g, is achieved. Catalysts whose lateral compressive strength is 20 to 500 N, particularly preferably 40 to 100 N, are particularly preferred. These compressive strengths can be set by customary measures in the field of tableting, for example setting the stamp pressure and measuring, for example, on an Instron Mini 44, stamp diameter 8 mm.
  • the alcohol can be evaporated in an evaporator and passed through a heated flow tube which contains a catalyst bed.
  • the amount of alcohol added per unit of time is preferably chosen to be 0.5 to 3, particularly preferably 1 to 2 kg of cyclohexanol per liter of catalyst bed and hour, for other alcohols according to their molecular weight in relation to cyclohexanol.
  • a method is particularly preferred in which the product obtained from the cyclohexane oxidation and subsequent purification, a mixture of cyclohexanol and cyclohexanone, is used.
  • the reaction temperature is preferably between 200 to 500 ° C, particularly preferably 300 to 450 ° C, without being unacceptable
  • the temperature is selected so that a conversion of the secondary alcohol of preferably 60% to 90%, particularly preferably 65% to 80%, is obtained. This results in the particularly preferred range of the reaction temperature of 300 to 450 ° C.
  • the product obtained is usually condensed from
  • the catalyst according to the invention has a high selectivity with a long service life and sufficiently high activity.
  • Cyclohexanone produced according to the invention is an important precursor for polyamide 6 and polyamide -6.6.
  • the mixture is stirred for 30 minutes and then left to stand for 30 minutes, the supernatant solution is suctioned off, the suspension is distributed over three suction filters, filtered off and washed with a total of 72 l of distilled water.
  • the filter cake is spread over several trays and dried in a convection oven at 125 ° C overnight. 3570 grams of product are obtained, which are then heated in a standing oven to 400 ° C. and for one
  • the product obtained is ground, mixed with 4% by weight, based on the total solids, of a synthetic graphite (average particle diameter 44 ⁇ m) and compressed in a tablet machine to give tablets of 5 mm in diameter and 3 mm in height.
  • the tablets are annealed in a laboratory oven at 500 ° C for 4 h.
  • the catalyst has a side fracture hardness of
  • a zinc salt solution which consists of zinc sulfate and zinc chloride in a molar ratio of 1: 2.
  • a solution of sodium carbonate and sodium hydroxide in a molar ratio of 40:60 is used as the base. Both solutions are dosed into the container at the same time, the pumping speeds being regulated so that a pH of 8 is established. The product obtained is filtered. Then you wash on Nutsche. Otherwise the procedure is as in Example 1.
  • the finished catalyst has a Na content of 0.39%, a side fracture hardness of 45 N and a BET specific surface area of 9 m 2 / g.
  • Example 2 The procedure is as in Example 2, but the catalyst tablets are not calcined at the end of the preparation. This resulted in a specific BET surface area of 64 m 2 / g. The sodium content of the catalyst was 0.39% and its side hardness was 48 N.
  • Shaped bodies are produced as in Example 2.
  • the resulting catalyst has a sodium content of 0.022%, a side fracture hardness of 35 N and a BET specific internal surface area of 10 m 2 / g.
  • the catalysts obtained were tested in a flow tube of 55 mm in inner diameter and in length.
  • the reaction tube is heated electrically, the volume of the catalyst bed is in each case 2 l. 3 kg of a mixture of 94% cyclohexanol and 6% cyclohexanone per hour are fed to the reactor via an evaporator.
  • the catalysts are run over a period of about 7 to 10 days and the reaction temperature is gradually raised to such an extent that the product contains a cyclohexanone content of 73-75%. Then the dianone content of the product, determined by gas chromatography, and the necessary reaction temperature were used to assess the catalysts. In the catalyst according to Example 3, the conversion was not raised above 63%; Comparable measured values from Example 1 and Example 2 are given.

Abstract

The invention relates to zinc oxide based dehydrogenating catalysts as active components having a defined sodium content and a specific surface. The invention also relates to the utilization of said catalysts in the dehydrogenation of secondary alcohols to obtain the corresponding ketones.

Description

DEHYDRΓERKATALYSATOREN AUF BASIS VON ZΓNKOXΓD DEHYDRATE CATALYSTS BASED ON ZΓNKOXΓD
Die vorliegende Erfindung betrifft Dehydrierkatalysatoren auf Basis Zinkoxid als Aktivkomponente und deren Verwendung bei der Dehydrierung von sekundären Alkoholen zu den entsprechenden Ketonen.The present invention relates to dehydrogenation catalysts based on zinc oxide as an active component and their use in the dehydrogenation of secondary alcohols to the corresponding ketones.
Aus DE-A-19626587 ist ein Verfahren zur Herstellung von Cyclohexanon durch Dehydrieren an einem Katalysator, enthaltend Cu als Aktivkomponente und Al2O3 als Träger bekannt. Derartige Katalysatoren ermöglichen in der Regel niedrigere Reaktionstemperaturen als solche ohne Kupfer.DE-A-19626587 discloses a process for the preparation of cyclohexanone by dehydrogenation over a catalyst containing Cu as the active component and Al 2 O 3 as the carrier. Such catalysts generally allow lower reaction temperatures than those without copper.
EP-A-0204 046 beschreibt ein Verfahren zur Herstellung von Cyclohexanon, bei dem ein Katalysator bestehend aus Kupfer, Zinkoxid und einer Alkalimetallverbindung, bevorzugt Natriumcarbonat, für die Dehydrierung eingesetzt wird. Oft sind die Selektivitäten derartiger Katalysatoren gering, was jedoch durch geeigneteEP-A-0204 046 describes a process for the preparation of cyclohexanone in which a catalyst consisting of copper, zinc oxide and an alkali metal compound, preferably sodium carbonate, is used for the dehydrogenation. The selectivities of such catalysts are often low, but this is due to suitable ones
Herstellungsweise sowie günstige Kombinationen von Wirkstoff und Träger behoben werden kann. Zusätzlich müssen dem Reaktionsgemisch oft Zusätze wie Wasser beigemengt werden, um eine akzeptable Selektivität zu erhalten. Nicht beseitigt werden kann der vergleichsweise niedrige Umsatz, der aus der bei niedriger Reaktions- temperatur ungünstigeren Lage des Gleichgewichts resultiert. Eine Anhebung derProduction method and cheap combinations of active ingredient and carrier can be remedied. In addition, additives such as water often have to be added to the reaction mixture in order to obtain an acceptable selectivity. The comparatively low conversion, which results from the less favorable position of the equilibrium at a low reaction temperature, cannot be eliminated. An increase in
Reaktionstemperatur ist bei diesen Katalysatoren regelmäßig mit einer deutlich beschleunigten Alterung der Katalysatoren infolge Sinterung des Kupfers verbunden, was zu unwirtschaftlich kurzen Lebenszeiten der so eingesetzten Katalysatoren fuhrt.In these catalysts, the reaction temperature is regularly associated with a significantly accelerated aging of the catalysts due to sintering of the copper, which leads to uneconomically short lifetimes for the catalysts used in this way.
Diese Nachteile vermeiden Verfahren, die kupferfreie Katalysatoren einsetzen.These disadvantages avoid processes that use copper-free catalysts.
In DE-A- 1443462 werden Katalysatoren für die Dehydrierung von Cyclohexanol beschrieben, die durch Fällung von Zinksalzlösung mit basischen Fällungsmitteln hergestellt werden. Über den Na-Gehalt der Katalysatoren werden keine Angaben ge- macht. Aus der DE-A- 19609954 ist ein Verfahren zur Dehydrierung von sekundärenDE-A-1443462 describes catalysts for the dehydrogenation of cyclohexanol which are prepared by precipitation of zinc salt solution with basic precipitation agents. No information is given on the Na content of the catalysts. DE-A-19609954 describes a process for the dehydrogenation of secondary ones
Alkoholen bei erhöhter Temperatur in der Gasphase bekannt. Als Katalysator wird ein Gemisch aus Zinkoxid und Calciumcarbonat verwendet. Der Katalysator wird erhalten, indem man Zink- und Calciumnitrat mit Natriumcarbonat fällt, abfiltriert, nitratfrei wäscht und den Filterkuchen trocknet. Anschließend wird das Produkt kalziniert und zu Formkörpern verpreßt. Eine den wirtschaftlichen Einsatz dieses Verfahrens ermöglichende Selektivität wird jedoch erst erhalten, wenn dem in denAlcohols known at elevated temperature in the gas phase. As a catalyst a mixture of zinc oxide and calcium carbonate is used. The catalyst is obtained by precipitating zinc and calcium nitrate with sodium carbonate, filtering off, washing free of nitrates and drying the filter cake. The product is then calcined and pressed into shaped articles. However, a selectivity that enables the economical use of this method is only obtained when the in the
Reaktor strömenden Gas Wasserstoff zugesetzt werden wird. Dies ist ein gravierender Nachteil des Verfahrens, da der Zusatz von Wasserstoff den Umsatz der Reaktion sowohl durch die ungünstigere Lage des Gleichgewichts der Reaktion als auch infolge verringerter Verweilzeit des Gasgemisches im Reaktor vermindert. Die Raum- Zeit- Ausbeute dieses Verfahrens betrug ausweislich der Beispiele 0,46 g Cyclohexanon pro g Katalysator und Stunde.Reactor flowing gas hydrogen will be added. This is a serious disadvantage of the process, since the addition of hydrogen reduces the conversion of the reaction both because of the less favorable position of the equilibrium of the reaction and because of the reduced residence time of the gas mixture in the reactor. According to the examples, the space-time yield of this process was 0.46 g of cyclohexanone per g of catalyst and hour.
In allen bekannten Verfahren des Standes der Technik ist Dianon ein unerwünschtes Nebenprodukt.Dianon is an undesirable by-product in all known processes of the prior art.
Die Aufgabe der vorliegenden Erfindung bestand daher darin, einen Katalysator für ein Verfahren zu finden, bei dem sekundäre Ketone, bevorzugt Cyclohexanon mit hohen Selektivitäten bei hohen Umsätzen erhalten werden können. Darüber hinaus soll der Katalysator eine ausreichende Lebensdauer aufweisen. Bei dem erfindungs- gemäßen Verfahren dehydriert man sekundäre Alkohole in Gegenwart eines Katalysators, der aus Zinkoxid mit 0,1 bis 0,6 Gew% Natrium besteht, bei erhöhter Temperatur in der Gasphase. Als Alkohole kann man erfindungsgemäß cyclo- aliphatische Alkohole sowie sekundäre aliphatische Alkohole, bevorzugt Cyclo- hexanol einsetzen.The object of the present invention was therefore to find a catalyst for a process in which secondary ketones, preferably cyclohexanone, can be obtained with high selectivities and high conversions. In addition, the catalyst should have a sufficient service life. In the process according to the invention, secondary alcohols are dehydrated in the presence of a catalyst which consists of zinc oxide with 0.1 to 0.6% by weight sodium, at elevated temperature in the gas phase. According to the invention, cycloaliphatic alcohols and secondary aliphatic alcohols, preferably cyclohexanol, can be used as alcohols.
Gegenstand der Anmeldung ist demnach ein Katalysator , der aus Zinkoxid als aktiver Verbindung besteht. Bevorzugt werden dabei Katalysatoren, die 0,1 bis 3 bevorzugt 0,1 bis 0,6 % Natrium enthalten. Besonders bevorzugt sind Katalysatoren mit 0,15 bis 0,4 % Natrium. Die spezifische BET-Oberfläche liegt vorzugsweise zwischen 5 und 30 m2/g, besonders bevorzugt werden 8 bis 20 m2/g. Ein erfindungsgemäßer Katalysator ist durch Ausfällen einer schwerlöslichen Zinkverbindung aus wasserlöslichen Zinkverbindungen mit einer Base und anschließende Verarbeitung des Fällprodukts in einer dem Fachmann geläufigen Weise zugänglich. Eine erfindungsgemäße Herstellung besteht beispielsweise darin, wäßrige Natrium- carbonatlösung einzusetzen und dazu Zinksulfat zu geben. Man filtriert das Fällprodukt ab, wäscht es, trocknet es und kalziniert es anschließend nicht über 650°C. Das erhaltene Produkt wird gegebenenfalls aufgemahlen und zu Formkörpern verpreßt, beispielsweise indem man es mit einem Tablettierhilfsmittel vermischt und auf einer Tablettenmaschine tablettiert.The application accordingly relates to a catalyst which consists of zinc oxide as an active compound. Catalysts which contain 0.1 to 3, preferably 0.1 to 0.6% sodium are preferred. Catalysts with 0.15 to 0.4% sodium are particularly preferred. The specific BET surface area is preferably between 5 and 30 m 2 / g, particularly preferably 8 to 20 m 2 / g. A catalyst according to the invention can be obtained by precipitation of a sparingly soluble zinc compound from water-soluble zinc compounds with a base and subsequent processing of the precipitate in a manner familiar to the person skilled in the art. A preparation according to the invention consists, for example, in using aqueous sodium carbonate solution and adding zinc sulfate. The precipitate is filtered off, washed, dried and then not calcined above 650 ° C. The product obtained is optionally ground up and pressed to give shaped articles, for example by mixing it with a tabletting aid and tableting on a tablet machine.
Üblicherweise geht man von wäßrigen Zinksalzlösungen aus. Als Zinksalze kann man beispielsweise Zinksulfat, Zinknitrat, Zinkchlorid oder Zinkacetat verwenden. Bevorzugt ist Zinksulfat und Zinkchlorid. Zur Fällung kann man beispielsweise wasserlösliche Natriumsalze wie Natriumhydroxid, Natriumydrogencarbonat oder Natriumcarbonate einsetzen, bevorzugt sind Natriumcarbonat und Natriumhydroxid.Usually one starts from aqueous zinc salt solutions. For example, zinc sulfate, zinc nitrate, zinc chloride or zinc acetate can be used as zinc salts. Zinc sulfate and zinc chloride are preferred. For example, water-soluble sodium salts such as sodium hydroxide, sodium hydrogen carbonate or sodium carbonates can be used for the precipitation, sodium carbonate and sodium hydroxide being preferred.
Man wird dabei eines der beiden Salze, bevorzugt die Base, als Lösung in einem Behälter vorlegen und die wäßrige Lösung des anderen Salzes zulaufen lassen, bis der gewünschte pH- Wert erreicht ist. Bevorzugt fällt man bis zu einem pH von 6 bis 9. Eine solche Herstellung ist beispielsweise in DE-A-3900243 beschrieben. Die Temperatur wählt man üblicherweise im Bereich 20 bis 90°C, bevorzugt 50 bisOne of the two salts, preferably the base, is initially introduced as a solution in a container and the aqueous solution of the other salt is run in until the desired pH is reached. It is preferred to drop to a pH of 6 to 9. Such a preparation is described, for example, in DE-A-3900243. The temperature is usually selected in the range from 20 to 90 ° C., preferably from 50 to
80°C. In einer anderen Variante des Verfahrens dosiert man beide Salzlösungen gleichzeitig in ein Gefäß, wobei die Zugabe so gesteuert wird, daß sich ein konstanter pH- Wert in dem Gefäß einstellt. Bevorzugt ist ein pH- Wert während der Fällung von 6 bis 9. Man filtriert den Niederschlag, wäscht und trocknet. Bevorzugt führt man die Wäsche im Durchlauf so durch, daß in dem kalzinierten Katalysatorvorläufer noch80 ° C. In another variant of the process, both salt solutions are metered into a vessel at the same time, the addition being controlled in such a way that a constant pH value is established in the vessel. A pH value during the precipitation of 6 to 9 is preferred. The precipitate is filtered off, washed and dried. The washing is preferably carried out in a continuous manner in such a way that still in the calcined catalyst precursor
0,1 bis 0,6 % auswaschbares Natrium, besonders bevorzugt 0,15 bis 0,4 % auswaschbares Natrium enthalten sind. Dabei ermittelt man den Gehalt auswaschbaren Natriums durch Bestimmung des Na-Gehalts vor und nach Wäsche des Katalysatorvorläufers mit 100 1 destilliertem Wasser pro kg Katalysatorvorläufer. Bei der Wäsche des Katalysatorvorläufers achte man darauf, das Anion des verwendeten Zinksalzes vollständig auszuwaschen, da diese die Selektivität des erfindungsgemäßen Katalysators ungünstig beeinflussen können. In einer anderen bevorzugten Verfahrensweise setzt man dem verarbeiteten Pulver gezielt die Menge an Natrium zu, etwa in dem man das erhaltene Fällprodukt mit der Basenlösung, beispielsweise einer Natriumcarbonatlösung, anteigt und anschließend trocknet. Die Konzentration der Lösung wählt man so, daß der Katalysator den erfindungsgemäßen Natrium-Gehalt aufweist. Dadurch ist der Waschschritt besonders wichtig, da man hierbei den Natriumgehalt des Katalysators, der beispielsweise durch Elementar- analyse für den Fachmann leicht zugänglich ist, beeinflußen kann.0.1 to 0.6% washable sodium, particularly preferably 0.15 to 0.4% washable sodium are contained. The amount of sodium which can be washed out is determined by determining the Na content before and after washing the catalyst precursor with 100 l of distilled water per kg of catalyst precursor. When washing the catalyst precursor, care should be taken to completely wash out the anion of the zinc salt used, since these can adversely affect the selectivity of the catalyst according to the invention. In another preferred procedure, the amount of sodium is added to the processed powder in a targeted manner, for example by pasting the precipitated product obtained with the base solution, for example a sodium carbonate solution, and then drying it. The concentration of the solution is chosen so that the catalyst has the sodium content according to the invention. As a result, the washing step is particularly important since it is possible to influence the sodium content of the catalyst, which is easily accessible to those skilled in the art, for example, through elemental analysis.
Das erhaltene Pulver kann man gegebenenfalls vorkalzinieren, bevorzugt in einem Sprühtrockner. Anschließend wird das Pulver einem Formgebungsschritt unterzogen und das Produkt kalziniert, wobei man die Kalzinierbedingungen und dabei insbe- sondere die Temperatur so wählt, daß der resultierende Katalysator die spezifische innere Oberfläche nach BET von mindestens 5 und höchstens 30 m2/g, besonders bevorzugt 8 bis 20 m2/g aufweist. Dabei gilt für erste orientierende Versuche, daß die spezifische Oberfläche umso kleiner wird, je höhere Kalzinierungstemperaturen und/oder je länger die Kalzimerungszeiten gewählt werden. Gegebenenfalls kann man die Reihenfolge von Formgebung und Kalzinierung auch umkehren.The powder obtained can optionally be pre-calcined, preferably in a spray dryer. The powder is then subjected to a shaping step and the product is calcined, the calcining conditions and, in particular, the temperature being selected such that the resulting catalyst has a BET specific internal surface area of at least 5 and at most 30 m 2 / g, particularly preferably 8 up to 20 m 2 / g. For initial orientation tests, the higher the calcination temperatures and / or the longer the calcification times, the smaller the specific surface area. If necessary, the order of shaping and calcining can also be reversed.
In einer bevorzugten Ausführungsform kalziniert man vor, vermischt man das erhaltene Produkt mit 0,1 bis 5 Gew.-%, bevorzugt 1 bis 5 Gew.-%, besonders bevorzugt 2 bis 5 Gew.-% Hilfsmittel und verpreßt das erhaltene Produkt zu Formkörpern, wie Tabletten, Sternchen, Ringen, Split, Wagenrädern, Kugeln, bevorzugt Tabletten.In a preferred embodiment, calcination is carried out, the product obtained is mixed with 0.1 to 5% by weight, preferably 1 to 5% by weight, particularly preferably 2 to 5% by weight of auxiliaries, and the product obtained is pressed to give shaped articles , such as tablets, asterisks, rings, split, wagon wheels, balls, preferably tablets.
Bevorzugt als Tablettierhilfsmittel ist Graphit, wobei synthetischer Graphit aufgrund seiner höheren Reinheit besonders bevorzugt ist wie man überhaupt bei den Verarbeitungsschritten die Verunreinigung des Katalysators vermeiden sollte. Ganz allgemein sollte man darauf achten, keine solchen Metalloxide in den Katalysator ge- langen zu lassen, von denen dem Fachmann bekannt ist, daß sie saure Eigenschaften besitzen. Hierzu gehört beispielsweise aktiviertes Aluminiumoxid. Man kalziniert die Tabletten, so daß die spezifische innere Oberfläche nach BET von mindestens 5 und höchstens 30 m2/g, besonders bevorzugt 8 bis 20 m2/g erreicht wird. Besonders bevorzugt sind dabei Katalysatoren, deren Seitendruckfestigkeit 20 bis 500 N, besonders bevorzugt 40 bis 100 N beträgt. Diese Druckfestigkeiten lassen sich durch übliche Maßnahmen auf dem Gebiet der Tablettierung einstelllen, so zum Beispiel den Stempeldruck einstellen und beispielsweise auf einem Instron Mini 44, Stempeldurchmesser 8 mm messen.Graphite is preferred as a tabletting aid, synthetic graphite being particularly preferred because of its higher purity, as one should avoid contamination of the catalyst at all during the processing steps. In general, care should be taken not to allow any metal oxides which the person skilled in the art is aware of to have acidic properties to get into the catalyst. This includes, for example, activated aluminum oxide. They are calcined Tablets so that the BET specific internal surface area of at least 5 and at most 30 m 2 / g, particularly preferably 8 to 20 m 2 / g, is achieved. Catalysts whose lateral compressive strength is 20 to 500 N, particularly preferably 40 to 100 N, are particularly preferred. These compressive strengths can be set by customary measures in the field of tableting, for example setting the stamp pressure and measuring, for example, on an Instron Mini 44, stamp diameter 8 mm.
Bei Verwendung des Katalysators in dem erfmdungsgemäßen Verfahren bringt man den Dampf des zu dehydrierenden sekundären Alkohols mit dem Katalysator inWhen using the catalyst in the process according to the invention, the vapor of the secondary alcohol to be dehydrogenated is brought in with the catalyst
Kontakt. Hierzu kann man beispielsweise den Alkohol in einem Verdampfer verdampfen und durch ein beheiztes Strömungsrohr, das eine Katalysatorschüttung enthält, leiten. Im Fall von Cyclohexanol wählt man die Menge an pro Zeiteinheit aufgegebenem Alkohol bevorzugt zu 0,5 bis 3, besonders bevorzugt 1 bis 2 kg Cyclo- hexanol pro Liter Katalysatorschüttung und Stunde, bei anderen Alkoholen entsprechend ihrem Molgewicht im Verhältnis zu Cyclohexanol. Besonders bevorzugt ist eine Verfahrensweise, bei der man das aus der Cyclohexan-Oxidation und anschließender Reinigung erhaltene Produkt, ein Gemisch aus Cyclohexanol und Cyclohexanon einsetzt. Die Reaktionstemperatur beträgt dabei bevorzugt zwischen 200 bis 500°C, besonders bevorzugt 300 bis 450°C, ohne daß es zu inakzeptablenContact. For this purpose, for example, the alcohol can be evaporated in an evaporator and passed through a heated flow tube which contains a catalyst bed. In the case of cyclohexanol, the amount of alcohol added per unit of time is preferably chosen to be 0.5 to 3, particularly preferably 1 to 2 kg of cyclohexanol per liter of catalyst bed and hour, for other alcohols according to their molecular weight in relation to cyclohexanol. A method is particularly preferred in which the product obtained from the cyclohexane oxidation and subsequent purification, a mixture of cyclohexanol and cyclohexanone, is used. The reaction temperature is preferably between 200 to 500 ° C, particularly preferably 300 to 450 ° C, without being unacceptable
Veränderungen in der Katalysatorlebensdauer kommt. In einer bevorzugten Verfahrensweise wählt man die Temperatur so, daß sich ein Umsatz des sekundären Alkohols von bevorzugt 60 % bis 90 %, besonders bevorzugt 65 % bis 80 % einstellt. Dabei ergibt sich dann der besonders bevorzugte Bereich der Reaktionstemperatur von 300 bis 450°C. Das erhaltene Produkt wird üblicherweise kondensiert, vonChanges in catalyst life is coming. In a preferred procedure, the temperature is selected so that a conversion of the secondary alcohol of preferably 60% to 90%, particularly preferably 65% to 80%, is obtained. This results in the particularly preferred range of the reaction temperature of 300 to 450 ° C. The product obtained is usually condensed from
Wasserstoff befreit und destillativ aufgearbeitet.Free hydrogen and worked up by distillation.
Der erfindungsgemäße Katalysator weist eine hohe Selektivität bei langer Lebensdauer und ausreichend hoher Aktivität auf. Erfindungsgemäß hergestelltes Cyclohexanon ist eine wichtige Vorstufe für Polyamid 6 und Polyamid -6.6. The catalyst according to the invention has a high selectivity with a long service life and sufficiently high activity. Cyclohexanone produced according to the invention is an important precursor for polyamide 6 and polyamide -6.6.
BeispieleExamples
Beispiel 1 (Katalysatorherstellung)Example 1 (catalyst preparation)
Man legt in einem 60 1-Behälter 18 1 destilliertes Wasser sowie 18 1 einer 18 %igen18 liters of distilled water and 18 liters of 18% strength are placed in a 60 liter container
Natriumcarbonatlösung vor, erhitzt diese auf 60°C und läßt unter Rühren etwa 20 1 einer auf 60°C erhitzten Zinksulfatlösung enthaltend 100 g Zink/1, erhalten durch Auflösen von Zinksulfathydrat (ZnSO *7 H2O) in destilliertem Wasser und Ansäuern mit Schwefelsäure bis pH = 4,1, binnen 60 Minuten zulaufen. Man beendet den Zulauf der Zinksulfatlösung bei Erreichen eines pH-Wertes im Gefäß von 7,0.Sodium carbonate solution before, heated to 60 ° C and leaves with stirring about 20 1 of a zinc sulfate solution heated to 60 ° C containing 100 g zinc / 1, obtained by dissolving zinc sulfate hydrate (ZnSO * 7 H 2 O) in distilled water and acidifying with sulfuric acid up to pH = 4.1, run in within 60 minutes. The feed of the zinc sulfate solution is stopped when the pH in the vessel reaches 7.0.
Man rührt 30 Minuten nach und läßt anschließend 30 Minuten stehen, saugt die überstehende Lösung ab, verteilt die Suspension auf drei Nutschen, filtriert ab und wäscht mit insgesamt 72 1 destilliertem Wasser. Der Filterkuchen wird auf mehrere Bleche verteilt und in einem Umluftofen über Nacht bei 125°C getrocknet. Man erhält 3570 Gramm Produkt, das anschließend in einem Standofen auf 400°C erhitzt und für eineThe mixture is stirred for 30 minutes and then left to stand for 30 minutes, the supernatant solution is suctioned off, the suspension is distributed over three suction filters, filtered off and washed with a total of 72 l of distilled water. The filter cake is spread over several trays and dried in a convection oven at 125 ° C overnight. 3570 grams of product are obtained, which are then heated in a standing oven to 400 ° C. and for one
Stunde kalziniert wird. Das erhaltene Produkt wird gemahlen, mit 4 Gew.-%, bezogen auf den gesamten Feststoff, eines synthetischen Graphits (mittlerer Partikeldurchmesser 44 μm) gemischt und in einer Tablettiermaschine zu Tabletten von 5 mm Durchmesser und 3 mm Höhe verpreßt. Die Tabletten werden in einem Labor- ofen bei 500°C für 4 h getempert. Der Katalysator besitzt eine Seitenbruchhärte vonHour is calcined. The product obtained is ground, mixed with 4% by weight, based on the total solids, of a synthetic graphite (average particle diameter 44 μm) and compressed in a tablet machine to give tablets of 5 mm in diameter and 3 mm in height. The tablets are annealed in a laboratory oven at 500 ° C for 4 h. The catalyst has a side fracture hardness of
104 N, eine spezifische innere Oberfläche nach BET von 11 m2/g , einen Natrium- Gehalt von 0,20 % und einen Sulfatgehalt von 0,02 %.104 N, a BET specific internal surface area of 11 m 2 / g, a sodium content of 0.20% and a sulfate content of 0.02%.
Beispiel 2 (Katalysatorherstellung)Example 2 (catalyst preparation)
Entsprechend DE 3900243 verwendet man eine Zinksalzlösung, die aus Zinksulfat und Zinkchlorid in einem molaren Verhältnis von 1:2 besteht. Als Base verwendet man eine Lösung von Natriumcarbonat und Natriumhydroxid in einem molaren Verhältnis von 40:60. Beide Lösungen dosiert man gleichzeitig in den Behälter, wobei man die Zupumpgeschwindigkeiten so regelt, daß sich ein pH von 8 einstellt. Man filtriert das erhaltene Produkt. Anschließend wäscht man auf Nutschen. Ansonsten verfährt man wie in Beispiel 1. Der fertige Katalysator hat einen Na-Gehalt von 0,39 %, eine Seitenbruchhärte von 45 N und eine spezifische innere Oberfläche nach BET von 9 m2/g.According to DE 3900243, a zinc salt solution is used which consists of zinc sulfate and zinc chloride in a molar ratio of 1: 2. A solution of sodium carbonate and sodium hydroxide in a molar ratio of 40:60 is used as the base. Both solutions are dosed into the container at the same time, the pumping speeds being regulated so that a pH of 8 is established. The product obtained is filtered. Then you wash on Nutsche. Otherwise the procedure is as in Example 1. The finished catalyst has a Na content of 0.39%, a side fracture hardness of 45 N and a BET specific surface area of 9 m 2 / g.
Beispiel 3 (Vergleichsbeispiel)Example 3 (comparative example)
Man verfährt wie Beispiel 2, jedoch werden die Katalysatortabletten am Ende der Herstellung nicht kalziniert. Daraus resultierte eine spezifische innere Oberfläche nach BET von 64 m2/g. Der Natrium-Gehalt des Katalysators betrug 0,39 %, seine Seitenbruchhärte 48 N.The procedure is as in Example 2, but the catalyst tablets are not calcined at the end of the preparation. This resulted in a specific BET surface area of 64 m 2 / g. The sodium content of the catalyst was 0.39% and its side hardness was 48 N.
Beispiel 4 (Vergleichsbeispiel)Example 4 (comparative example)
Man verfährt wie Beispiel 2, jedoch werden 5,0 kg des Fällproduktes zusätzlich auf einer Vakuumnutsche mit 530 1 destilliertem Wasser gewaschen. Die Herstellung derThe procedure is as in Example 2, but 5.0 kg of the precipitate are additionally washed with 530 l of distilled water on a vacuum filter. The manufacture of the
Formkörper erfolgt wie in Beispiel 2. Der resultierende Katalysator hat einen Natrium-Gehalt von 0,022 %, eine Seitenbruchhärte von 35 N und eine spezifische innere Oberfläche nach BET von 10 m2/g.Shaped bodies are produced as in Example 2. The resulting catalyst has a sodium content of 0.022%, a side fracture hardness of 35 N and a BET specific internal surface area of 10 m 2 / g.
Beispiel 5 (Vergleichsbeispiel)Example 5 (comparative example)
Man teigt 4 kg ZnO-Pulver Typ "Zinkweiß Pharma 8" der Fa. Grillo mit Wasser an, trocknet das Produkt in einem Labortrockenschrank bei 125°C über Nacht, bricht den erhaltenen Kuchen und siebt mit einer Siebmaschine die Fraktion 1,5 bis 3 mm Partikelgröße ab. Das resultierende Korn ist sehr weich, besitzt eine spezifische innere Oberfläche nach BET von 7,5 m2/g und einen Natrium-Gehalt von 12 ppm.4 kg of ZnO powder, type "Zinkweiß Pharma 8" from Grillo, are mixed with water, the product is dried in a laboratory drying cabinet at 125 ° C. overnight, the cake obtained is broken and the fraction 1.5 to 3 is sieved using a sieving machine mm particle size. The resulting grain is very soft, has a BET specific internal surface area of 7.5 m 2 / g and a sodium content of 12 ppm.
Beispiel 6 (Test der Katalysatoren)Example 6
Die erhaltenen Katalysatoren wurden in ein Strömungsrohr von 55 mm Innendurchmesser und Im Länge getestet. Die Beheizung des Reaktionsrohres erfolgt elektrisch, das Volumen der Katalysatorschüttung beträgt jeweils 2 1. Über einen Verdampfer werden dem Reaktor 3 kg eines Gemisches aus 94 % Cyclohexanol und 6 % Cyclohexanon pro Stunde zugeführt. Die Katalysatoren werden über einen Zeitraum von etwa 7 bis 10 Tagen gefahren und dabei die Reaktionstemperatur schrittweise soweit angehoben, daß sich ein Cyclohexanon-Gehalt im Produkt von 73-75 % ergab. Dann wurde der gaschromatographisch ermittelte Dianongehalt des Produkts sowie die notwendige Reaktionstemperatur für die Beurteilung der Katalysatoren herangezogen. Bei dem Katalysator nach Beispiel 3 wurde der Umsatz nicht über 63 % angehoben; vergleichbare Meßwerte von Beispiel 1 und Beispiel 2 sind angegeben.The catalysts obtained were tested in a flow tube of 55 mm in inner diameter and in length. The reaction tube is heated electrically, the volume of the catalyst bed is in each case 2 l. 3 kg of a mixture of 94% cyclohexanol and 6% cyclohexanone per hour are fed to the reactor via an evaporator. The catalysts are run over a period of about 7 to 10 days and the reaction temperature is gradually raised to such an extent that the product contains a cyclohexanone content of 73-75%. Then the dianone content of the product, determined by gas chromatography, and the necessary reaction temperature were used to assess the catalysts. In the catalyst according to Example 3, the conversion was not raised above 63%; Comparable measured values from Example 1 and Example 2 are given.
Arbeitet man nach dem Beispiel 1 der DE 14 43 462, so erhält man einen Katalysator mit 3,67 Gew.-% Natrium.If you work according to Example 1 of DE 14 43 462, you get a catalyst with 3.67 wt .-% sodium.

Claims

Patentansprtiche Patentansprtiche
1. Dehydrierkatalysator enthaltend Zinkoxid, dadurch gekennzeichnet, daß zwischen 0,1 und 3 Gew.-% und 0,1 bis 0,6 Gew% Natrium bezogen auf die gesamte Masse mit einer spezifischen inneren Oberfläche nach BET von 5 bis1. Dehydrogenation catalyst containing zinc oxide, characterized in that between 0.1 and 3 wt .-% and 0.1 to 0.6 wt% sodium based on the total mass with a specific inner surface according to BET from 5 to
30 m2/g.30 m 2 / g.
2. Dehydrierkatalysator nach Anspruch 1, dadurch gekennzeichnet, daß zwischen 0,1 und 1 Gew.-%, besonders bevorzugt zwischen 0,1 und 0,6 Gew.-% ganz besonders bevorzugt zwischen 0,15 und 0,4 Gew.-% Natrium bezogen auf die gesamte Masse des Katalysators enthalten ist.2. Dehydrogenation catalyst according to claim 1, characterized in that between 0.1 and 1 wt .-%, particularly preferably between 0.1 and 0.6 wt .-% very particularly preferably between 0.15 and 0.4 wt .-% % Sodium based on the total mass of the catalyst is contained.
3. Dehydrierkatalysator nach Anspruch 1 und/oder 2, dadurch gekennzeichnet, daß die innere Oberfläche nach BET zwischen 8 und 20 m2/g beträgt.3. Dehydrogenation catalyst according to claim 1 and / or 2, characterized in that the inner surface according to BET is between 8 and 20 m 2 / g.
4. Dehydrierkatalysator nach mindestens einem Anspruch 1 bis 3, dadurch gekennzeichnet, daß zusätzliche Hilfsmittel, bevorzugt zum Tablettieren, in Mengen zwischen 0,1 bis 5 Gew.-% , bevorzugt 1 bis 5 Gew.-%, besonders bevorzugt 2 bis 5 Gew.-% enthalten sind, ganz besonders bevorzugt Graphit.4. dehydrogenation catalyst according to at least one of claims 1 to 3, characterized in that additional auxiliaries, preferably for tableting, in amounts between 0.1 to 5% by weight, preferably 1 to 5% by weight, particularly preferably 2 to 5% by weight .-% are contained, very particularly preferably graphite.
5. Formkörper enthaltend einen der Dehydrierkatalysatoren nach den Ansprüchen 1 bis 4, dadurch gekennzeichnet, daß er eine Seitendruckhärte zwischen 20 N und 500 N bevorzugt 40 N bis 100 N aufweist.5. Shaped body containing one of the dehydrogenation catalysts according to claims 1 to 4, characterized in that it has a side pressure hardness between 20 N and 500 N, preferably 40 N to 100 N.
6. Formköφer nach Anspruch 5, dadurch gekennzeichnet, daß er eine Tablette ist.6. molded article according to claim 5, characterized in that it is a tablet.
7. Verfahren zur Herstellung von sekundären Ketonen durch Dehydrierung sekundärer Alkohole in Gegenwart eines Katalysators nach mindestens einem Anspruch 1 bis 4 und/oder einem Formköφer der Ansprüche 5 oder 6 in der7. A process for the preparation of secondary ketones by dehydrogenation of secondary alcohols in the presence of a catalyst according to at least one of claims 1 to 4 and / or a molded article of claims 5 or 6 in the
Gasphase bei erhöhter Temperatur, bevorzugt zwischen 200 und 500°C besonders bevorzugt zwischen 300 und 450°C. Gas phase at elevated temperature, preferably between 200 and 500 ° C, particularly preferably between 300 and 450 ° C.
EP00951346A 1999-07-19 2000-07-06 Zinc oxide-based dehydrogenating catalysts Withdrawn EP1202799A1 (en)

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DE1211629B (en) * 1962-08-14 1966-03-03 Basf Ag Process for the dehydrogenation of cyclohexanol
DE1443462A1 (en) * 1962-12-18 1969-08-14 Basf Ag Process for the dehydration of primary or secondary alcohols
FR1543933A (en) * 1966-11-28 1968-10-31 Inst Francais Du Petrole Process and catalyst for the manufacture of cyclic ketones by catalytic dehydrogenation of cyclic alcohols
DE3200483A1 (en) * 1982-01-09 1983-07-21 Bayer Ag, 5090 Leverkusen MOLDED BODIES CONTAINING SILICA, METHOD FOR THE PRODUCTION THEREOF AND THEIR USE
JPS59204145A (en) * 1983-05-02 1984-11-19 Toa Nenryo Kogyo Kk Production of carbonyl compound
DE3513568A1 (en) * 1985-04-16 1986-10-16 Basf Ag, 6700 Ludwigshafen PROCESS FOR WORKING UP CYCLOHEXANOL, CYCLOHEXANONE AND CYCLOHEXYL HYDROPEROXIDE CONTAINING REACTION MIXTURES
US4670605A (en) * 1985-05-31 1987-06-02 Industrial Technology Research Institute Process and catalyst for the conversion of cyclohexanol to cyclohexanone
US4918239A (en) * 1988-12-27 1990-04-17 National Science Council Method of producing cyclohexanone from cyclohexanol through oxidative dehydrogenation
JPH04164813A (en) * 1990-10-30 1992-06-10 Mitsubishi Materials Corp Production of zinc oxide powder
JPH04164816A (en) * 1990-10-30 1992-06-10 Mitsubishi Materials Corp Production of acicular zinc oxide powder by submerged synthetic method
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