WO2005123683A1 - Procede pour purifier de l'acide nicotinique - Google Patents

Procede pour purifier de l'acide nicotinique Download PDF

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WO2005123683A1
WO2005123683A1 PCT/EP2005/006403 EP2005006403W WO2005123683A1 WO 2005123683 A1 WO2005123683 A1 WO 2005123683A1 EP 2005006403 W EP2005006403 W EP 2005006403W WO 2005123683 A1 WO2005123683 A1 WO 2005123683A1
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nicotinic acid
gas
solid
desublimation
cooling
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PCT/EP2005/006403
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German (de)
English (en)
Inventor
Thomas Grassler
Hartmut Gihr
Martin Karches
Hans-Ulrich PRÖBSTLE
Frank Rosowski
Jochen Petzoldt
Matthias Rauls
Andrea Magin
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Basf Aktiengesellschaft
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Publication of WO2005123683A1 publication Critical patent/WO2005123683A1/fr

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    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07D—HETEROCYCLIC COMPOUNDS
    • C07D213/00—Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members
    • C07D213/02—Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members having three double bonds between ring members or between ring members and non-ring members
    • C07D213/04—Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members having three double bonds between ring members or between ring members and non-ring members having no bond between the ring nitrogen atom and a non-ring member or having only hydrogen or carbon atoms directly attached to the ring nitrogen atom
    • C07D213/60—Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members having three double bonds between ring members or between ring members and non-ring members having no bond between the ring nitrogen atom and a non-ring member or having only hydrogen or carbon atoms directly attached to the ring nitrogen atom with hetero atoms or with carbon atoms having three bonds to hetero atoms with at the most one bond to halogen, e.g. ester or nitrile radicals, directly attached to ring carbon atoms
    • C07D213/78—Carbon atoms having three bonds to hetero atoms, with at the most one bond to halogen, e.g. ester or nitrile radicals
    • C07D213/79—Acids; Esters
    • C07D213/80—Acids; Esters in position 3

Definitions

  • the present invention relates to a process for the purification of nicotinic acid produced by gas phase oxidation, the nicotinic acid-containing gaseous reaction product of the gas phase oxidation being subjected to at least one pre-cooling step and then at least one desubiimation step to desublimate the nicotinic acid.
  • the nicotinic acid content of the solid desublimated in the desubiimation step is higher than the nicotinic acid content in the gaseous reaction product.
  • Nicotinic acid (pyridine-3-carboxylic acid) is an economically important heterocyclic carboxylic acid. It is widely used in the fields of medicine and agriculture as a B vitamin and as an intermediate for pharmaceutical products and for plant growth regulators.
  • nicotinic acid An important large-scale manufacturing process for nicotinic acid is the oxidation of 3-methyl-pyridine with nitric acid in the liquid phase.
  • Nicotinic acid can also be produced industrially by catalytic gas phase oxidation of 3-methyl-pyridine in tube bundle reactors.
  • the starting material is a mixture of a gas containing molecular oxygen, for example air, water vapor and the 3-methyl-pyridine to be oxidized.
  • the mixture is usually passed through a multiplicity of tubes arranged in a reactor (tube bundle reactor), in which there is a bed of at least one oxidation catalyst.
  • the nicotinic acid is present in gaseous form in the product gas stream.
  • By-products are generally formed in the production of nicotinic acid.
  • the by-product spectrum of the gas phase oxidation of 3-methylpyridine to nicotinic acid is essentially determined by the composition of the starting product and the reaction conditions to which the starting products are subjected.
  • the reaction product of the production of nicotinic acid usually contains components with both higher and lower phase transition temperatures, based on the nicotinic acid, the phase transition temperature being understood as the melting or boiling or sublimation temperature.
  • Processes for working up solid crude nicotinic acid ie for largely removing the solid acid from these by-products, are known from the prior art.
  • EP-A 870 525 describes a process for the simple recovery of sublimable material such as nicotinic acid.
  • the solid, sublimable material is evaporated in a reaction chamber and then on as a crystal layer deposited one wall of this chamber.
  • the wall is then cooled so that a temperature difference between the crystal layer and the wall arises, which leads to the crystal layer breaking away. In this way, for example, melting of the crystal layer is no longer necessary to obtain the product.
  • JP 49 121 782 describes a method for accelerating the sublimation of nicotinic acid by making the crude nicotinic acid thermoplastic resins such as e.g. Low molecular weight polyethylene can be added. This process does not achieve an increased purity.
  • JP 49 124 070 describes a process for the purification of solid nicotinic acid, wherein sublimed crude nicotinic acid is passed through layers of adsorber material, for example Al 2 O 3 , at temperatures below the production temperature. In one example, this achieves a purity of over 99%.
  • JP 49 062 475 describes a process for the purification of solid nicotinic acid, in which nicotinic acid is first sublimed and then passed over fused corundum at temperatures between 100 and 200 ° C. and deposited there. The purity is increased to over 99%.
  • JP 49 100 087 describes a combined process from sublimation and crystallization of the solid crude nicotinic acid.
  • Water-alcohol mixtures are used for the crystallization.
  • colorless nicotinic acid is obtained in a yield of 82.3% and a purity of 99.8%.
  • JP 49 100 086 describes a combined process from sublimation and crystallization.
  • alcohol and then water with activated carbon are used as solvents in two steps, the order of the steps being decisive for the discoloration of the nicotinic acid.
  • the yield of nicotinic acid is only 66.7%.
  • RU 2 152 932 describes a process for the purification of solid crude nicotinic acid by washing with water. Water flows through layers of nicotinic acid.
  • JP 49 049 966 describes a process for the purification of solid crude nicotinic acid by heating it together with alumina at 220 ° C. for 10 hours and then treating it with activated carbon in water. The yield is 68.3% with 99.9% purity.
  • US 2,916,494 describes a process for separating nicotinic acid from non-volatile organic and inorganic contaminants.
  • the solid raw Nicotinic acid overflows with an inert gas containing water vapor, sublimates and is entrained by the gas.
  • the gas containing nicotinic acid is then brought into contact with water and the pure nicotinic acid is obtained from the aqueous nicotinic acid slurry by filtration.
  • the aqueous nicotinic acid slurry is treated with activated carbon and then filtered and cooled, the nicotinic acid crystallizing out. Yields of approx. 92% and purities of over 99% are described.
  • GB 855819 describes a process for the purification of solid crude nicotinic acid, in which the nicotinic acid heated to at least 200 ° C. is first sublimed by passing hot inert gas over it and entrained in the gas stream, and then dissolved by bringing the gas into contact with a solvent and by cooling the solution thus obtained to be precipitated.
  • CH 543 510 describes a process for the preparation of nicotinic acid by gas phase oxidation of 3-methylpyridine. A method for purifying the crude nicotinic acid after the oxidation is not described.
  • German published patent application DE 2647 712 describes a process for the preparation of niacin by gas phase oxidation of alkylpyridines on a solid catalyst mass with air and water vapor. A method for purifying the crude nicotinic acid after the oxidation is not described.
  • DE 19839 559 -A describes a process for the preparation of niacin by gas phase oxidation of ⁇ -picoline. It is also described that the synthesized product can be separated in high purity at 100 to 230 ° C. A process for the purification of nicotinic acid, which comprises at least one pre-cooling step before desublimation, is not described.
  • CN 12960 04 describes a process for the production of nicotinic acid by gas phase oxidation of 3-methylpyridine. A method for purifying nicotinic acid immediately after the oxidation is not described.
  • Another object of the invention was to provide a process for the purification of nicotinic acid produced by gas phase oxidation, which makes it possible to adjust the size of the nicotinic acid particles in a targeted manner.
  • Another object of the invention was to provide a process for the purification of nicotinic acid produced by gas phase oxidation, which enables access to largely colorless nicotinic acid.
  • a process for the purification of the gaseous reaction product of the oxidation of 3-methylpyridine to nicotinic acid in which a desired purity of the nicotinic acid is achieved and the yield of nicotinic acid is as high as possible, was provided by the process for the purification of Nicotinic acid produced by gas phase oxidation, characterized in that the gaseous reaction product containing nicotinic acid is subjected to the gas phase oxidation at least one pre-cooling step and then at least one desubiimation step for desublimation of the nicotinic acid.
  • the process according to the invention increases the nicotinic acid content of the solid sublimed in the desubiimation step compared to the nicotinic acid content in the gaseous reaction product.
  • the gaseous reaction product of the gas phase oxidation containing nicotinic acid is therefore first pre-cooled and then the purity of the nicotinic acid in the solid formed in this step is increased by at least one desubiimation step compared to the gaseous reaction product.
  • the relative nicotinic acid content of the desublimed solid is higher, i.e. nicotinic acid is more pure after desublimation.
  • the concentration of nicotinic acid and other gaseous by-products in the gaseous reaction product of the gas phase oxidation corresponds to a certain partial pressure (measure, for example, mbar) depending on the operating pressure of the system in which the reaction product is located.
  • a certain partial pressure measure, for example, mbar
  • the saturation temperatures of the components can be determined at a given operating pressure at a certain partial pressure (Fig. 1).
  • nicotinic acid When the saturation temperature of nicotinic acid falls below, ie when the product gas cools down, nicotinic acid begins to desublimate, since the product gas contains nicotine acid is saturated. At temperatures above the saturation temperature one speaks of under-saturation of the gas, there is no desublimation.
  • Desublimation of nicotinic acid can be done in several ways.
  • the product gas enters the apparatus in which the desublimation takes place at a temperature which is lower than the temperature of the gas immediately after the gas phase oxidation.
  • This inlet temperature is in the range from 250 ° C. to 380 ° C., preferably from 270 to 350 ° C., particularly preferably from 290 to 340 ° C. and in particular from 300 to 330 ° C.
  • the product gas is precooled in a further apparatus before entering the apparatus in which the desublimation takes place.
  • the deposition of nicotinic acid during desublimation can take place on surfaces whose temperature is below the saturation temperature, so-called cold surfaces.
  • Such cold surfaces occur, for example, in heat exchanger tubes or heat exchanger plates.
  • the temperature of the cold surfaces lies between the respective saturation temperatures of the nicotinic acid and the highest-boiling, lower-boiling component.
  • the temperature of the cold surfaces is advantageously at the same time as far as possible below the saturation temperature of nicotinic acid and as close as possible above the saturation temperature of the highest-boiling, low-boiling component.
  • the temperature of the cold surfaces is preferably 10 ° C., in particular 5 ° C., above the saturation temperature of the highest-boiling, lower-boiling component.
  • the solid nicotinic acid deposited on such cold surfaces can be removed from the surfaces by mechanical action, falling due to gravity, melting, sublimation, gas shock or other suitable methods.
  • the nicotinic acid can also be desublimated by mixing the product gas with cooling gas.
  • the precooled product gas is, in a preferred embodiment of the invention, mixed by mixing the product gas with a cooling gas whose temperature is below the saturation temperature of nicotinic acid. re is cooled below the saturation temperature so that the nicotinic acid is obtained as a powdery solid in the gas stream.
  • the cooling gas and product gas are preferably mixed in such a way that the nicotinic acid is obtained in the desired particle size, the greatest possible purity and the highest possible yield and that the apparatus has the highest possible system availability.
  • the highest possible system availability is achieved, for example, if the amount of deposits on the apparatus walls (caking) is kept as low as possible. For example, it is advantageous if the system can be used for more than 8,000 hours per year.
  • the proportion of secondary components in the desublimated nicotinic acid-containing solid is preferably less than 2, particularly preferably less than 1 and in particular less than 0.5% by weight, based on the solid.
  • the nicotinic acid separates from the gas phase preferably by more than 80, particularly preferably by more than 90 and in particular by more than 95% by weight.
  • Desublimation of nicotinic acid by mixing the product gas with cooling gas is therefore a direct heat exchange, since the cooling medium comes into direct contact with the product gas stream.
  • the apparatus used for the desubiimation step is called the desublimator. The location of the solid formation depends on the design of the desublimator.
  • the temperature of the cooling gas lies between the respective saturation temperatures of the nicotinic acid and the highest-boiling, lower-boiling component.
  • the temperature of the cooling gas is advantageously at the same time as far as possible below the saturation temperature of nicotinic acid and as close as possible above the saturation temperature of the highest-boiling, lower-boiling component.
  • the temperature of the cooling gas is preferably 10 ° C., in particular 5 ° C., above the saturation temperature of the highest-boiling, lower-boiling component.
  • Lighter-boiling substances are understood to mean all components whose partial pressure at the melting point of nicotinic acid is 235-237 ° C higher than the partial pressure of nicotinic acid.
  • Such components contained in the product gas of the gas phase oxidation of 3-methylpyridine to nicotinic acid are, for example, 3-formylpyridine, 3-methylpyridine and pyridine.
  • a particularly preferred type of desublimation is the deposition of the solid on inert particles in the fluidized bed.
  • This type of desublimation is preferred from an economic point of view, since no cooling gas and consequently no cooling gas blower are required.
  • the inflowing product gas ensures the necessary swirling of the belbettp
  • the cooling of the product gas to temperatures below the saturation temperature required for desublimation takes place by cold inert particles, which are cooled, for example, by the jacket of the desublimator or by internal heat exchanger elements. Tube bundle heat exchangers, spiral heat exchangers, plate heat exchangers and all other types of heat exchangers known to the person skilled in the art can be used as heat exchangers.
  • the product gas can be introduced into the desublimator at various points, preferably through the bottom of the fluidized bed or additionally through lateral injection points.
  • the spatial distance between the heat exchanger elements and the injection points of the product gas is preferably selected such that as little solid as possible is deposited on the cold heat exchanger elements.
  • this distance is at least 0.2 m, preferably 0.5 m and particularly preferably 1 m.
  • inert particles Common materials for the inert particles are glass, sand, alumina, fused aluminum oxide and Al 2 O 3 , preferably glass and sand.
  • the product of value from the inert particles can be separated, for example, by mechanical stress such as is generated by the fluidized bed itself.
  • the nicotinic acid falling off from the inert particles can then be separated off at the outlet of the fluidized bed, for example by gas filters. It is preferred to separate the product of value from the inert particles by sublimation in the same or in a further apparatus.
  • a further, particularly preferred embodiment of the invention is to dissolve the product of value from the inert particles using a liquid solvent in the same or in a further apparatus.
  • desublimation are the deposition of the product of value on solid nicotinic acid in a fluidized bed, in a circulating fluidized bed or in a thin gas-solid flow such as pneumatic conveying.
  • Another object of the invention is the separation of the solid nicotinic acid obtained in the desubiimation step in a fluidized bed, the particles of the fluidized bed consisting of nicotinic acid.
  • the deposition on nicotinic acid in the fluidized bed is particularly advantageous since neither a cooling gas is required nor a solid which is foreign to the process has to be used for the inert particles.
  • the cooling of the nicotinic acid particles takes place like the cooling of the inert particles already described.
  • the desublimating nicotinic acid is deposited on the existing nicotinic acid particles and particle growth occurs.
  • the nicotinic acid particles in the fluidized bed it is advantageous to keep the nicotinic acid particles in the fluidized bed until a desired size is reached.
  • the particle size available at the individual times of desublimation can be checked via a screening discharge using on-line analytical methods such as laser diffraction or also off-line analytical methods such as sieving.
  • additional nozzles can be installed through which the product gas flows at high speed (50 m / s, preferably 150 m / s, particularly preferably 200 m) / s) flows in and the particles of the fluidized bed are crushed by grinding.
  • the height of the fluidized bed is accordingly chosen so that the nicotinic acid is largely completely separated with the lowest possible pressure loss.
  • the technique of desublimation by deposition of the product of value on solid nicotinic acid can be used for each of these desubiimation steps.
  • this type of desublimation for the last desubiimation step, since the desired particle size for the end product can then be set in a targeted manner.
  • the use of only one desublimation step is generally advantageous if the product gas originating from the gas phase oxidation contains, in addition to nicotinic acid, essentially or exclusively lower boiling substances or substances with lower phase transition temperatures in relation to the nicotinic acid. In the desubiimation step described, these components remain in the gas phase and are therefore largely separated from the nicotinic acid.
  • a container with a circular base is suitable, for example, as an apparatus for desublimation (Fig. 2 and 3). It is preferably a cylindrical container, the diameter of which can change in the direction of the cylinder axis.
  • product gas and cooling gas can be introduced separately at different points in the desublimator through nozzles.
  • the gases can be introduced at the top, side or bottom of the apparatus.
  • the nozzles can be simple nozzles or also multi-component nozzles (e.g. annular gap nozzle), so that cooling and product gas can be introduced into the de-sublimation space at different times or simultaneously at different or the same place.
  • multi-component nozzles e.g. annular gap nozzle
  • the cooling gas nozzles can be distributed over the height and circumference of the desublimator. By adding the cooling gas in different positions of the desublimator, the particle formation, particle agglomeration and particle growth can be specifically controlled by deliberately reducing the nicotinic acid supersaturation in the product gas stream. This enables targeted control of the particle size of the nicotinic acid powder.
  • the product gas is added in the upper half of the desublimator.
  • the resulting solid falls down and due to the longer dwell time and falling distance in the cooled gas compared to a reaction gas supply in the lower half of the container, particles are formed whose average diameter is generally greater than 20 ⁇ m (measured with a commercially available particle size measuring device based on the principle of laser diffraction). Unwanted dusty particles with diameters of less than 20 ⁇ m are largely avoided. If larger particles are desired, it is particularly advantageous if the supply points for product and cooling gas are as far apart as possible. If finer particles are to be obtained, the use of a multi-component nozzle, such as an annular gap nozzle, is advantageous, so that cooling gas and product gas are mixed at one point almost immediately after exiting the nozzle.
  • the containers can either be connected in parallel or in series, ie the product gas flows largely simultaneously into the n containers or, after leaving the container ni, flows into a container n 2 .
  • Product gas from which nicotinic acid has already been removed is particularly suitable for use as a cooling gas. All components that may not have been removed, such as, for example, lower-boiling components, accumulate in the product gas, which is reused as cooling gas.
  • product gas freed from nicotinic acid If product gas freed from nicotinic acid is used as the cooling gas, it must first be cooled. When the cooling gas is cooled indirectly in a heat exchanger, by-products contained in the product gas cause caking on the heat exchanger surfaces. Due to the caking that insulates the surfaces of the heat exchangers, the performance of the heat exchangers decreases. As a result, the cooling gas flow is no longer cooled down sufficiently, which in turn leads to a decrease in the amount of product. In order to ensure continuous operation, these cakes must be removed at regular intervals.
  • Liquid heat transfer media are preferably used as the refrigerant for generating cooling gas in both internal and external heat exchangers. Commercial heat transfer media, for example, are suitable for this. These are - often stabilized against decomposition - synthetic or mineral oils. Glycols and glycol ethers and their derivatives can also be used as coolants. The glycols are preferably mixed with water. Water is also suitable as a coolant. When water is used, the heat to be removed can be used directly to generate steam, otherwise the heat is removed again by cooling in a further heat exchanger and used, for example, to heat a cold process gas stream. In addition to cooling with liquid heat transfer media, it is also possible to generate the cooling gas with gaseous coolant. The advantage of liquid coolants is the higher heat capacity compared to gaseous coolants.
  • Tube heat exchangers, spiral heat exchangers, plate heat exchangers and all other types of heat exchangers known to those skilled in the art can be used as heat exchangers.
  • the gaseous reaction product of the gas phase oxidation containing nicotinic acid is subjected to at least one pre-cooling step before the at least one desubiimation step to desublimate the nicotinic acid (FIG. 4).
  • Pre-cooling of the gaseous reaction product before the at least one desubiimation step to desublimate the nicotinic acid is of particular economic interest, since in the desubiimation step that follows, a smaller amount of energy which arises during the formation of solids has to be dissipated.
  • the energy generated in the desubiimation step in a fluidized bed desublimator is dissipated via the apparatus jacket and optionally additionally via heat exchanger bundles installed in the apparatus.
  • the area required for heat transfer is proportional to the amount of heat to be dissipated. Accordingly, as the amount of heat decreases, only a smaller exchange area is required, which in turn leads to equipment downsizing and thus to increased efficiency.
  • the gaseous reaction product of the gas phase oxidation is cooled below the saturation temperature by adding colder gas.
  • the amount of cooling gas required for this is therefore smaller, the smaller the difference between the product gas and the saturation temperature.
  • a reduction in the amount of cooling gas required allows the use of less powerful fans, which in turn leads to lower investment and operating costs.
  • Another advantage of the pre-cooling of the product gas is that energy can be obtained from the reprocessing process at a higher temperature level than is the case for energy generation in the desubiimation step.
  • the energy to be dissipated during pre-cooling can be converted into steam, for example. At a higher temperature, higher vapor pressure levels can be achieved.
  • the gaseous reaction product of the gas phase oxidation is precooled to a temperature of 20 ° C., preferably 10 ° C. and in particular 5 ° C. above the saturation temperature of the nicotinic acid during the pre-cooling.
  • Suitable apparatuses for gas-solid separation are, for example, cyclones and gas filters. Furthermore, all apparatus from the prior art such as, for example, in Perry's Chemical Engineers' Handbook, Sixth Edition, McGraw-Hill Book Company, New York, 1984, chap. 18, p. 71 ff., Can be used to separate gas and solid.
  • the gas separated by the gas-solid separation can either be released directly into the environment or is processed, for example, in the form of thermal afterburning.
  • Nicotinic acid which is obtained as a solid in the desubiimation step, may have to be cooled further. This can be done, for example, with the aid of cooling screws, and all other state-of-the-art apparatus suitable for cooling solids can be used (Perry's Chemical Engineers' Handbook, Sixth Edition, McGraw-Hill Book Company, New York, 1984, chap. 11 , P. 43 ff.). Separation of the heavier boiling components
  • Another embodiment of the invention is a process for purifying nicotinic acid produced by gas phase oxidation, wherein before the at least one desubiimation step for desublimation of nicotinic acid and after the at least one pre-cooling step, a step is carried out to separate those components whose partial pressure at the melting point of nicotinic acid is lower than the partial pressure of nicotinic acid (Fig. 5).
  • the temperature at which the higher-boiling component is separated off is as little as possible above the saturation temperature of nicotinic acid. It is preferably about 20 ° C, particularly preferably about 10 ° C, in particular about 5 ° C above the saturation temperature of nicotinic acid.
  • the pre-cooling can take place at a temperature which lies between the temperature of the product gas immediately after the gas phase oxidation when it emerges from the oxidation reactor and the temperature of the step for separating off the higher-boiling component.
  • precooling of the product gas and removal of the higher-boiling component can also be carried out at approximately the same temperature.
  • the separation can be done in a container with a gas filter.
  • the residence time of the gas is selected so that the higher-boiling components separate out from the gas phase as a solid or liquid at a temperature above the saturation temperature of the nicotinic acid. If heavier boiling components occur as a solid in this process step, it is advantageous to clean the gas filters at equidistant intervals or depending on the amount separated and, if necessary, to regenerate them depending on the pressure loss, for example by flushing with water or steam.
  • Another object of the invention is to carry out the method according to the invention in an at least partially continuous manner. It is preferred to carry out the process in a completely continuous manner.
  • containers for the separation of the higher-boiling components which contain solids which can physically and / or chemically adsorb the components which separate out.
  • the heavier-boiling components which pass from the gas phase into the liquid or solid phase can be deposited on solids made of glass, sand, metal, Al 2 O 3 , fused alumina, alumina etc. by physical and / or chemical interactions.
  • containers which contain porous solids, which the absorbed components can absorb, to separate the heavier boiling components.
  • the heavier boiling components are bound in the pores of the material through interactions.
  • Suitable materials are absorbers known to those skilled in the art, such as activated carbon, zeolites, ion exchange resins, etc.
  • the nicotinic acid produced by gas phase oxidation may still be contaminated with unwanted components that have similar partial pressures even after the heavy boiling components have been separated off and after a desubiimation step.
  • similar partial pressures means that the difference between the partial pressure of the substance and the partial pressure of nicotinic acid is less than 100 mbar and in particular less than 50 mbar at the same temperature and the same total pressure.
  • the nicotinic acid can still be contaminated with small amounts of further components to which the aforementioned condition of partial pressures does not apply.
  • Small amounts are understood to mean less than 5% by weight, preferably less than 2% by weight, in particular less than 1% by weight.
  • a further embodiment of the invention is a process for the purification of nicotinic acid produced by gas phase oxidation, with a sublimation step and a second step for desublimation of the nicotinic acid taking place after the pre-cooling and the at least one step to desublimate the nicotinic acid (FIG. 6).
  • the sublimation process step at least partially converts the solid obtained from the first desubiimation step back into the gas phase in order to be separated from the gas phase again by a second desubiimation step.
  • This procedure is advantageous if the purity of nicotinic acid achieved by the first desubiimation step is to be improved further.
  • the sublimation and subsequent second desublimation free the product gas from those lower-boiling components which were obtained in the first desubiimation step as a solid together with the nicotinic acid.
  • the heavy boiling components which may still be present largely remain in the apparatus in which the sublimation step is carried out (sublimator). Since the process according to the invention is preferably carried out in a continuous manner, it is necessary that the higher-boiling components are removed from the sublimator continuously or at regular time intervals.
  • the sublimator can be designed, for example, as a fluidized bed.
  • the solid is transported into the sublimator after the first desublimation and the gas-solid separation. This can be done by conveying methods known to the person skilled in the art, such as pneumatic conveying or mechanical conveying with screw conveyors.
  • Auxiliary gas air, nitrogen, carbon dioxide, etc.
  • additional heat can also be can be introduced over the walls of the sublimator or via internal heat exchanger bundles.
  • inert solid particles such as glass balls, sand, alumina, molten coal, Al 2 O 3 , elastomer particles etc. can be introduced into the sublimator.
  • Such measures are advantageous because the space-time yield is increased by faster sublimation and smaller size of the apparatus.
  • the sublimator can also be designed as a hot surface, for example as a heat exchanger, heating screw or rotary tube.
  • the sublimation takes place in such a way that the auxiliary gas sweeps over the surfaces and the sublimating nicotinic acid heated on these surfaces picks up and carries it away.
  • Solid cooling is carried out by customary methods known to the person skilled in the art, as described, for example, in Perry's Chemical Engineers' Handbook, Sixth Edition, McGraw-Hill Book Company, New York, 1984, chap. 11, p. 43 ff.
  • nicotinic acid-containing solid obtained after the last desubiimation step is particularly preferred to subject the nicotinic acid-containing solid obtained after the last desubiimation step to at least one crystallization step, which may be preceded by an additional purification step (FIG. 7).
  • a process for purifying nicotinic acid produced by gas phase oxidation is preferred, which is characterized in that the gaseous reaction product containing nicotinic acid is subjected to the gas phase oxidation by a combination of desublimation, sublimation, solution and crystallization steps.
  • the solid containing the nicotinic acid is brought into solution in a suitable solvent at the dissolving temperature corresponding to the concentration or above.
  • the dissolution temperature depends on the solvent used and the concentration of the solid.
  • the dissolving temperature is reached when the minimum necessary temperature is reached when the mixture is heated so that there is no longer any undissolved portion.
  • solvents in which nicotinic acid is soluble to at least 1% by weight under normal conditions are generally suitable as solvents.
  • Preferred solvents are selected from water, monohydric and polyhydric alcohols, preferably ROH, where R is C 1 -C 4 -alkyl, particularly preferably methanol, ethanol, furthermore ethers, preferably tetrahydrofuran, amides, with dimethylacetamide being preferred, N-methylpyrrolidone and mixtures thereof.
  • the particularly preferred solvents are water, methanol, ethanol and mixtures thereof, with water being the most preferred.
  • This solution is preferably subjected to a conventional single-stage or multi-stage suspension crystallization.
  • the product is converted into the solid phase by cooling the mixture or by partial evaporation of the solvent or by a combination of cooling and evaporation.
  • the solid and liquid phases are separated in the usual way, for example by filtration, decanting, suction filtering, centrifuging, etc.
  • crystallization processes suitable for the process according to the invention are known to the person skilled in the art (for example from Crystallization Technology Handbook, ed. A. Mersmann, Marcel Dekker Inc., New York, 1995, whole book, in particular pp. 54-75) and can be carried out continuously or discontinuously Kind of be done.
  • the crystallization is carried out as a continuous suspension crystallization (Crystallization Technology Handbook, ed. A. Mersmann, Marcel Dekker Inc., New York, 1995, pp. 54-75).
  • the heat released during crystallization is preferably dissipated through cold apparatus walls or through partial evaporation of the crystallizing solution.
  • Such a multi-stage crystallization can be a combination of crystallization stages which are connected in series or a fractional crystallization.
  • the individual stages are preferably operated at different temperatures (FIG. 8).
  • the number of crystallization stages used is not subject to any restrictions. In particular, it is determined by the composition of the starting mixture, the desired purity of the nicotinic acid and the desired yield.
  • the fractional crystallization is preferably carried out with at least one stripping stage and at least one cleaning stage.
  • Fig. 9 shows a two-stage fractional crystallization.
  • the solid containing nicotinic acid may, for example, still be contaminated by a coloring component after the last desubiimation step.
  • impurities can be largely removed by pre-cleaning the mixture prior to crystallization. An extraction or absorption is preferred as pre-cleaning.
  • the pre-cleaning of the solution is preferably carried out at temperatures in the range from 70 ° C. to 140 ° C. when water is used as the solvent. It is advantageous to work at the highest possible temperature at which the coloring component is largely adsorbed.
  • the solids concentration is from 3 to 40% by weight, based on the mass of the solution. Crystallization is started at temperatures from 50 ° C to 150 ° C, preferably from 100 to 150 ° C.
  • nicotinic acid is obtained by cooling the solution to a temperature of from -20 ° C. to 50 ° C., preferably from 5 ° C. to 25 ° C., or by evaporating the solvent from the mixture at a temperature of 150 ° C. to 20 ° C, preferably 100 ° C to 40 ° C converted into the solid phase.
  • Vapor usage means that the vapor produced in the warmer stage is used to evaporate the solvent in the colder stage.
  • the solution is then subjected to suspension crystallization.
  • it is advantageous to remove as much solvent until the solids content of the suspension is 15 to 35% by weight. If it is desired to remove additional solvents because of the need for higher yields, saturated mother liquor can be returned from the filtration step to the crystallization stage.
  • the solid After separation from the liquid phase, the solid can be washed, filtered and dried for additional purification.
  • the product gas for the gas-phase oxidation of 3-methylpyridine to nicotinic acid was gradually cooled in four desublimator containers of approx. 420 ml volume each connected in series.
  • the temperature of the gas when it entered the first apparatus was approximately 320 ° C.
  • the gas composition was approximately 0.8% by volume of nicotinic acid, 35% by volume of water, 4% by volume of oxygen and 59% by volume of nitrogen, and various secondary components of a total of 1.2 vol%.
  • the temperature of the gas when leaving the last desublimator tank (starting temperature) was approx. 110 ° C. Crystals were deposited on the cold surfaces of the desublimator containers. After 8 hours, about 42 g of solid nicotinic acid had settled in the desublimator containers.
  • the nicotinic acid obtained had a purity of 97.3% by weight, determined by HPLC (High Pressure Liquid Chromatography).
  • Example 1 The product gas described in Example 1) was passed into the apparatus shown schematically in FIG. Nitrogen at a temperature of 70 ° C was introduced into the apparatus at spatially different locations (cooling gas 1: example 2; cooling gas 2: example 3; cooling gas 3: example 4) so that the temperature of the gas after flowing through the filter (5) was 115 ° C. Solid crystals were deposited on and to the side of the filter.
  • the grain size of the crystals was influenced by the location of the cooling gas mixture. Finer product, i.e. smaller grain sizes were obtained when only cooling gas 1 was introduced.
  • the purity of the nicotinic acid, determined by HPLC, was 98.4% by weight for example 2.
  • the product gas described in Example 1) was passed into a cylindrical fluidized bed (diameter 100 mm, height 40 cm), which was filled with glass balls with a grain size of 40 to 80 ⁇ m (Fig. 7).
  • the jacket of the fluidized bed was cooled to about 80 ° C., so that a temperature in the area of the moving solid Set at 108 ° C.
  • the experiment was ended after 14 hours and the purity of the nicotinic acid was determined to be 98.7% by weight
  • Example 5 was repeated, the glass balls in the fluidized bed being replaced by nicotinic acid particles in a particle size range between 50 and 120 ⁇ m (FIG. 7).
  • the nicotinic acid particles used had a purity of 99.5% by weight.
  • the temperature in the desublimation room was set to approximately 108 ° C. by jacket cooling. After a trial period of 36 hours, an increase in mass of 227 g was found. The purity of the nicotinic acid deposited was 98.9%.
  • Example 6 was repeated, the fluidized bed being in a double-jacketed glass vessel with a height of 3 m and an inner diameter of 300 mm. The height of the fluidized bed was 1.8 m. A yield of 87.3% by weight with a purity of 99.1% by weight was achieved for the nicotinic acid.
  • Desublimated solid containing nicotinic acid was used to prepare a 6% by weight solution in water at 80 ° C. and the solution was mixed with 3% by weight activated carbon based on the solution. After 180 min, the activated carbon loaded with the undesired secondary component was removed by filtration at 80 ° C. The filtered solution was then subjected to evaporation crystallization at about 1 bar and evaporated to 27% by weight of its weight. The suspension thus obtained was fed to a second evaporative crystallization at 35 ° C. under the same pressure and concentrated to 24% by weight, based on the original weight of the solution. After the solid had been separated off from the mother liquor, the solid was washed for further purification and dried.
  • Cooling crystallization of the desublimed solid Solid containing desublimated nicotinic acid was prepared at 80 ° C, a 6 wt .-% solution in water and the solution with stirring with 3 wt% activated carbon based on the solution. After 180 min, the activated carbon loaded with the undesired secondary component was removed by filtration at 80 ° C.
  • the filtered solution was then subjected to cooling crystallization at a cooling rate of 10 K * h "1 and cooled to room temperature, the solid precipitating out of the solution.
  • the solid was washed and dried after separation from the mother liquor for further purification.
  • the nicotinic acid purified in this way is colorless and has a purity of 99.7% by weight.
  • Figure 1 The concentration of nicotinic acid and other gaseous by-products in the gaseous reaction product of the gas phase oxidation (for example, mol / m 3 ) corresponds to a certain partial pressure (for example, mbar), which is dependent on the operating pressure of the system in which the reaction product is located.
  • a certain partial pressure for example, mbar
  • the saturation temperatures of the components can be determined at a known operating pressure at a certain partial pressure.
  • nicotinic acid saturation temperature falls below, i.e. when the product gas cools down, nicotinic acid begins to desublimate because the product gas is oversaturated with nicotinic acid.
  • nicotinic acid saturation temperature falls below, i.e. when the product gas cools down, nicotinic acid begins to desublimate because the product gas is oversaturated with nicotinic acid.
  • temperatures above the saturation temperature one speaks of under-saturation of the gas, there is no desublimation.
  • Example: 2.23 mol / m 3 nicotinic acid correspond to a partial pressure of approx. 50 mbar at an operating pressure of the gas cooler of 1 bar.
  • FIG. 2 shows schematically an apparatus for desublimation with cooling gas.
  • the product gas (201) is introduced, for example, into the upper part of the container (200).
  • the cooling gas can be introduced into the container at various points (202, 203, 204).
  • the solid (206) consisting mainly of nicotinic acid separates in the vicinity of the filter (205), the gas largely freed from nicotinic acid exits through the filter (205) from the desublimator as exhaust gas (207) and can be recycled and fed back into the process.
  • Figure 3 shows schematically an apparatus (200) for fluid bed desublimation.
  • Product gas (201) enters the fluidized bed of solid nicotinic acid particles (206), which are cooled by the heat exchanger (208), from below.
  • the desublimating nicotinic acid separates from the product gas on the particles.
  • the gas largely freed of nicotinic acid exits the desublimator as exhaust gas (207) through the filter (205).
  • FIG. 4 schematically shows the method according to the invention with pre-cooling and a desubiimation step.
  • the product gas (201) originating from the gas phase oxidation enters the precooler (3) for cooling. It then flows into the desublimator (205), where nicotinic acid separates.
  • the separation of gas and solid (206) follows, the exhaust gas (202) is discharged and can be used again if necessary.
  • the nicotinic acid is cooled (208) and discharged from the solid cooler (213).
  • Figure 5 The product gas (201) originating from the gas phase oxidation enters the precooler (203) for cooling.
  • the components that boil heavier than nicotinic acid are separated from the gas that has been pre-cooled in this way (204).
  • the gas freed from the components boiling heavier than nicotinic acid is then subjected to desublimation in the desublimator (205) and the solid which forms is separated from the gas (206).
  • the exhaust gas is removed (211), the nicotinic acid cooled (208) and recovered from the solid cooler (213).
  • FIG. 6 The product gas (201) originating from the gas phase oxidation enters the precooler (203) for cooling.
  • the pre-cooled gas is then subjected to a first desublimation in the desublimator (205) and the solid which forms is separated from the gas (206).
  • the exhaust gas is discharged (211).
  • the solid is sublimed with auxiliary gas (212) in the sublimator (207) and then subjected to a second desublimation in the desublimator (205).
  • the solid that forms is separated from the gas (206).
  • the exhaust gas is removed (211), the nicotinic acid is cooled (208) and isolated from the solid cooler (213).
  • Figure 7 The product gas (201) originating from the gas phase oxidation enters the precooler (203) for cooling.
  • the precooled gas is then subjected to a first desublimation in the desublimator (205) and the solid which forms is separated from the gas (206).
  • the exhaust gas is discharged (211).
  • the solid is then dissolved (209), the crystallization (210) and the crystallized nicotinic acid isolated (213).
  • Figure 8 shows schematically the crystallization process with successive crystallization stages.
  • the desublimate (801) is brought into contact with solvent (807) and dissolved (809).
  • This solution is subjected firstly to a first crystallization (810a) and then to a second crystallization at a lower temperature (810b), the vapors (802 and 803) formed in each case being separated off.
  • the liquid and solid phases are then separated (811), the solid being washed with solvent (806) and the moist crystals (804) and optionally the mother liquor (805) being discharged. It is also possible to recycle the mother liquor at least partially to the individual stages of dissolving (809) and crystallization (810a and 810b).
  • FIG. 9 schematically shows the crystallization process of the two-stage fractional crystallization.
  • the desublimate (801) is brought into contact with solvent (807) and dissolved (809).
  • This solution optionally with the addition of mother liquor from the subsequent crystallization (805), is subjected to the first crystallization step (810).
  • Fresh solvent (807) can be added.
  • the vapor is separated (802).
  • the mixture is then subjected to a solid-liquid separation (811), the moist crystals (804) and the mother liquor (805) are discharged if necessary.
  • the mother liquor (805) is then at least partially subjected to a second crystallization (810), again vapors (802) being separated off.
  • the mother liquor is separated off, the crystals are combined with dissolved desublimate (809) and again fed to the crystallization (810).

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Abstract

L'invention concerne un procédé pour purifier de l'acide nicotinique produit par une oxydation en phase gazeuse. Le procédé de l'invention est caractérisé en ce que le produit de la réaction gazeuse de l'oxydation en phase gazeuse qui contient de l'acide nicotinique, à au moins une étape de pré-refroidissement, puis à une étape de sublimation destiné à désublimer l'acide nicotinique.
PCT/EP2005/006403 2004-06-22 2005-06-15 Procede pour purifier de l'acide nicotinique WO2005123683A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE102004030163.8 2004-06-22
DE200410030163 DE102004030163A1 (de) 2004-06-22 2004-06-22 Verfahren zur Reinigung von Nicotinsäure

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WO2005123683A1 true WO2005123683A1 (fr) 2005-12-29

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS4962475A (fr) * 1972-10-20 1974-06-17
JPS49100087A (fr) * 1973-01-29 1974-09-20
EP0747359A1 (fr) * 1994-01-26 1996-12-11 Institut Kataliza Imeni G.K. Boreskova Sibirskogo Otdelenia Rossiiskoi Akademii Nauk Procede d'obtention d'acide nicotinique
EP0870525A1 (fr) * 1997-04-07 1998-10-14 Nippon Shokubai Co., Ltd. Procédé de récupération de matière sublimable
DE19839559A1 (de) * 1998-09-01 2000-03-02 Degussa Verfahren zur Herstellung von Nikotinsäure

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS4962475A (fr) * 1972-10-20 1974-06-17
JPS49100087A (fr) * 1973-01-29 1974-09-20
EP0747359A1 (fr) * 1994-01-26 1996-12-11 Institut Kataliza Imeni G.K. Boreskova Sibirskogo Otdelenia Rossiiskoi Akademii Nauk Procede d'obtention d'acide nicotinique
EP0870525A1 (fr) * 1997-04-07 1998-10-14 Nippon Shokubai Co., Ltd. Procédé de récupération de matière sublimable
DE19839559A1 (de) * 1998-09-01 2000-03-02 Degussa Verfahren zur Herstellung von Nikotinsäure

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
DATABASE WPI Section Ch Week 197443, Derwent World Patents Index; Class B03, AN 1974-74972V, XP002347665 *
DATABASE WPI Section Ch Week 197504, Derwent World Patents Index; Class B03, AN 1975-06502W, XP002347662 *

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