DE4207960A1 - Sepg. or reducing oxygen@, nitrite and/or nitrate content contained in water - by treating with hydrogen@, using catalyst comprising palladium, rhodium or copper - Google Patents

Abstract

Process comprises treating the water with H2 and contacting it with a catalyst comprising Pd and/or Rh or Pd and a metal of the Cu gp., impregnated in a carrier. The carrier consists of Al2O3 of ''theta'' and ''kappa'' modifications with no or only a small amt. of ''alpha'' modification, and free from ''gamma'' and ''delta'' modifications; the carrier has either a pore dia. monomodal distribution showing one max. in the 700-1500 (800-1250) Angstroms range. For treating water contaminated only with nitrite the catalyst comprises metal components from Pd and/or Rh, and if the water also contains metals, then the metal components comprise Pd and a Cu gp. metal or Rh and opt. Pd, or a mixt. of these catalysts. The pH value of the value is at most 8 and the process is repeated until oxygen, nitrite and/or nitrate contents are nil or of tolerable value. USE/ADVANTAGE - The catalyst/carrier is abrasion resistant

Description

The present invention relates to removal or Reduction of the oxygen, nitrite and / or nitrate content in water.

The in ground and surface water in the Federal Republic Nitrite and / or nitrate contents found in Germany has increased significantly in recent years. They fluctuate significant by location and may be partially tolerable Exceed maximum limits. For drinking water is in the new most EC guidelines, a permissible limit of 50 mg nitrate recommended per liter and a limit of 0.1 mg / l for nitrite. The increasing nitrite and nitrate levels in many basic and Surface waters are increasingly making processes Nitrite and nitrate removal as part of drinking water treatment tion necessary.

For removing nitrite and nitrate from drinking water biological processes and physical / chemical measures in Area of water desalination. Known After parts of these processes are possible contamination with Bak teries or their metabolic products or the mere publishers problem.

The removal of oxygen from water (the given if it can also be free of nitrite or nitrate) is in many Cases desirable. So it is known that oxygen in water the corrosion of metallic components such as cooling systems different. In areas of food production, for example  in the field of the production of beverages such as fruit juices or Alcoholic beverages will preferably be low in oxygen or acidic substance-rich water used.

From European patent application EP-A-03 59 074 (= US-A 49 990 266) is a continuously feasible catalytic reduction process for removal or min change in the nitrite and / or nitrate content known. According to the The process described there is in the nitrite or nitrate water introduced hydrogen gas and that with water substance-laden water contacted with a metal catalyst. The metal catalyst used is one with a Palla catalyst dium and / or rhodium or of palladium and a metal of Copper group existing metal component impregnated porö sen carrier. The Ge hold on possibly contained oxygen reduced.

The object of the present invention is to improve tes, catalytically operating process for the removal of To provide oxygen, nitrite and / or nitrate from water. In particular, it is an object of the invention to provide an improved to develop catalytic process, which in the case of Water treatment usual conditions is feasible, and at which the oxygen, nitrite and / or nitrate content forming harmless products, especially water or Nitrogen is removed without the water being immersed desired amounts of ammonium is loaded.

It has now, starting from that in EP-A-03 59 074, a improved, continuously feasible catalytic re found production process with which oxygen, nitrite and / or nitrate can be removed from water to form of non-toxic reaction products, mainly water or Nitrogen and largely avoiding the formation of Ammonium ions, and which especially when processing  of nitrite and / or nitrate contaminated groundwater, river water sern, spring water or industrial waste water, for example as part of the production of industrial water for the food industry tel or beverage industry or of drinking water and ent removal of nitrite and / or nitrate from drinks such as mineral water or fruit juices or from water used to manufacture of beverages such as mineral water, fruit juices or alcoholic beverages are determined, as well as for the removal of oxygen from the ge named waters can be used.

The invention relates to a continuous Process to remove or reduce the acid substance content, the nitrite and / or nitrate content of acid water containing substances and / or nitrite and / or nitrate with selective nitrogen formation, being acidic in the Water containing substances containing nitrite and / or nitrate introduces material gas and the water loaded with hydrogen contacted a catalyst, which is formed from a with a palladium and / or rhodium or from palladium and a metal component of the copper group impregnated porous support, the support made of aluminum oxide of the modifications "theta" and "kappa" and the Modification "alpha" not or at most in minor Amounts are present and the carrier is free of aluminum oxide Modifications "gamma" and "delta", and either a monomodal Distribution of pore diameters with a maximum in the range between 700 Å and 1500 Å, or a bimodal distribution pore diameter with two maxima in the range of 100 has up to 1500 Å, the average pore diameter between is 300 and 500 Å, and one for the treatment of only nitrite-contaminated water a catalyst, the metal compo nente consists of palladium and / or rhodium and, if that too treating water also contains nitrate, a catalyst that Sen metal component of palladium and a metal of copper  group consists of rhodium and optionally palladium, or a mixture of a catalyst, the metal component consists of palladium and a metal from the copper group, and a catalyst whose metal component consists only of palladium exists, begins, and does not exceed the pH of the water pH 8 can rise and the process if necessary as often performed in succession until the oxygen content, the Nitrite content and / or the nitrate content of the water removed or is reduced to a tolerable value.

The modification "alpha" should not exceed 10% by weight in Carrier available.

This process is therefore even more effective than that from the EP-A-03 59 074 known method because the special Alu supported minium oxide catalyst with high selectivity very is firm and has a longer service life. Additional advantages are connected to the implementation in the fluidized bed what will be explained later.

In the context of the present invention, oxygen term or nitrite or nitrate contaminated water and aqueous Lö solutions of any origin, provided they are free of substances that are known as poisons for Palla Kata containing dium, rhodium or metals of the copper group lysators can act or attack the carrier material. In In the present application, the term "water" denotes the like water and aqueous solutions. Contains what needs to be cleaned Water under the reaction conditions of the invention Other substances that can be reduced in the process are also used reduced. If it appears desirable, remove it to clean such reducible other substances beforehand from the the water.  

The nitrite and / or nitrate content as well as the oxygen content, which is removed with the method according to the invention or can be reduced to a tolerable level vary over a wide range. So with the invent Process according to the invention water with a nitrate and / or Nitrate levels between 0.1 mg / l and a few grams per liter to treat. The present method is particularly suitable to remove the nitrite and / or nitrate content from water with a low nitrite and / or nitrate load, for example example in the range of 0.1 to 20 mg / l nitrite and / or about 5 to 600 mg / l nitrate.

It is clear to the person skilled in the art that the ver drive to remove oxygen from water whoever applied can that contains neither nitrite nor nitrate. The Ver Can of course also drive to remove nitrite and / or Nitrate from water can be applied, which does not contain oxygen contains. Finally, one can follow the procedure according to a broad Ren variant also for the removal of nitrite and / or nitrate use water containing oxygen at the same time. In this In addition to nitrite or nitrate, oxygen is also removed distant.

In particular, the inventive method for loading act of water, which is in its purity degree corresponds to water, which is a natural filter tion has gone through. Such water can be water soluble Substances, e.g. B. inorganic salts, in orders of magnitude, such as they can be found in the groundwater, e.g. B. up to some Contain grams per liter. Examples of the invention Processes to be treated according to water are e.g. B. groundwater, Well water, spring water or bank filtrates or already ent speaking pre-treated other wastewater z. B. industrial Waste water, for example from flue gas washes, in which the Content of oxygen, nitrite and / or nitrate can be reduced  can. More examples of water with the erfindungsge be treated like mineral beverages water, lemonades and fruit juices as well as water used for provision of beverages such as mineral water, lemonades, fruit juices or alcoholic beverages, e.g. B. used for beer production should be.

The method is suitable, for example, for use in Within the framework of drinking water treatment and the treatment of Water or industrial water for food or beverage Industry as well as for other purposes where an oxygen, Nitrite and / or low or low nitrate water is required.

If you want to treat water according to the invention, which only Contains oxygen, is used with a supported catalyst Palladium and / or rhodium and optionally a copper metal as a metal component. As a metal component Palladium and / or rhodium used if only nitrite (as well oxygen if necessary) is to be removed from the water. If the water also contains nitrate, Palla is preferred Use dium in combination with a metal from the copper group det. However, rhodium as a metal component is also suitable. Copper are particularly suitable as metals of the copper group and silver, preferably copper.

The proportion of the metal component in the overall catalyst can between 0.1 and 10% by weight, preferably between 0.5 and 6 and in particular between 0.5 and 4 wt .-%.

A palladium content of 0.5 to has proven to be favorable 5 wt .-%, in particular 0.5 to 3 wt .-%, based on the Ge total weight of the catalyst. Is a metal component Combination of palladium with copper is used Weight ratio of palladium to copper preferably between between 2: 1 and 8: 1, especially between 3: 1 and 5: 1 a weight ratio of 4: 1 is particularly favorable.  

For the treatment of nitrate or nitrate and Nitrite-contaminated water can advantageously also be a catalyst system of only containing palladium as the metal component Catalyst particles and palladium and a metal of copper group, in particular containing copper as the metal component Supported catalyst particles are used. The weight ver Ratio of palladium-containing to palladium / copper-containing Catalyst particles can vary depending on the nitrate and nitrite content of water and the amount and composition of the metal compo nenten of the catalysts vary and can be between 1: 5 and 5: 1, preferably between 1: 2 and 2: 1. The difference Lichen particles are suitably separate. Man only then leads the water to be treated through the palladium / Particles containing copper group metal and then through the only Palladium-containing particles, preferably each in the Fluidized bed.

The diffusion in the aqueous medium should be sufficient go quickly. This is an essential requirement to avoid ammonium formation. This requirement meet the requirements to be used in the process according to the invention Catalysts from the specified alumina modifi cations "theta" and "kappa" exist and the specified ver division of the pore diameter. Particularly advantageous are catalysts with a support, which is a monomodal Distribution of pore diameters with a maximum in the range has between 800 Å and 1250 Å, in particular between 800 Å and 1050 Å.

The BET surface area of the supports having the structure described above is preferably in the range from about 41 to 50 m ² / g. The pore volume is advantageously between 0.35 ml / g and 0.60 ml / g. The weight ratio of the modifications "theta" and "kappa" is preferably between 30:70 and 10:90.

It is preferably used in the process according to the invention spherical supported catalysts as they are a vortex layering processes are particularly suitable. Other shapes can but can also be used, e.g. B. supported catalysts in Shape of cylinders, hollow cylinders, hollow spheres, compacts, Extrusions etc. Of course, you can also wear straps in mono use lithen form. For the particularly preferred version form of the process according to the invention as a fluidized bed, Suspension or fixed bed reactions become spherical supports catalysts with a particle size of at least 0.1 mm, for example 0.1 mm to 20 mm used. As particularly good suitable for implementation as a fluidized bed process catalyst particles with a diameter of 0.1 to 1 mm, preferably 0.3 to 0.8 mm.

In the treatment of nitrite and / or nitrate-containing water according to the invention, an amount of hydroxyl ions equivalent to the reduced amount of nitrite or nitrate is released. This leads to an increase in the pH of the treated water depending on the amount of nitrite and nitrate to be reduced or the hydrogen available for the reduction. The pH of the water is appropriately regulated so that the reaction-related increase does not lead to values above pH 8. The pH can be adjusted, for example, by adding an aqueous solution of an acid, preferably a dilute organic acid, such as hydrochloric acid or CO ₂ .

Introducing the hydrogen gas into the water and one if necessary, pH regulation may be required take place while the water is in contact with the catalyst is. However, the hydrogen gas is expedient in a sepa advise fumigation containers placed in the water before this is contacted with the catalyst. If you want, you can regulate the pH of the water to be treated that the subsequent pH increase remains in the desired range.  

The pH of the water to be treated should be in a range from about 2 to 8, in particular 4 to 8.

Usually contains water, its nitrite and / or Nitrate content reduced with the inventive method oxygen is also to be dissolved. For complete removal The nitrite and / or nitrate content of the water is there a total of such a quantity of hydrogen gas is required at least that to reduce the oxygen content and Nitrite and / or nitrate content of the water stoichiometric necessary amount corresponds. So are for the reduction of 100 mg Nitrate theoretically requires about 9 mg of hydrogen to ent Removal of 8 mg oxygen about 1 mg hydrogen. If that water to be treated only small amounts of nitrite and / or Contains nitrate, it proves to be appropriate, such Initiate amount of hydrogen, which at least the stoichio metrically calculated amount and at most a 20% over shot corresponds to this calculated amount.

The gassing of the water with hydrogen is preferred depending on the type of gas permeation. Here is the Gas entry into the water through a solid membrane, for example wise a silicone rubber membrane. Are particularly well suited Membranes with an integral-asymmetrical structure and in particular Composite membranes. These membranes comprise a porous thing ser resistant carrier structure and at least one layer water-resistant, non-porous polymer on which the gas to be fumigated Liquid is passed. This non-porous layer, e.g. B. made of silicone polymer, is very thin, for example a thickness of 0.5 to 10 microns. Such membranes who those described in EP-A 2 91 679 (US-A 49 33 085).

The inventive method can at normal pressure or slight overpressure, e.g. B. up to 10 atmospheres or more The solubility of the hydrogen gas in the water is  at normal pressure and temperatures between 10 and 25 ° C below 2 mg / l and is also ver when the pressure is doubled double. Where to reduce higher nitrite and / or nitrate correspondingly larger quantities of hydrogen are required , it is therefore recommended to fumigate under pressure to take. When treating water that contains only oxygen holds, working at ambient pressure is very possible.

The contact time between the catalyst and the handle the water should expediently not significantly above that the time required for the transfer of Nitrite and / or nitrate to nitrogen is necessary. Longer Contact times can potentially reduce the formation Nitrogen beyond the zero level to ammonium increase. If necessary, you can carry out a few manual tests ren.

The process according to the invention is preferably operated as Fluid bed, suspension or fluid bed. This embodiment is therefore preferred because, surprisingly, germs the catalyst particles with possible reduction in the cataly activity. It is therefore not necessary dig, if it is of course also possible to disinfect for example by UV light or other measures.

With a high content of oxygen, nitrite or nitrate can if necessary, the method according to the invention is repeated several times perform each other until a sufficient reduction z. B. also tolerable values for drinking water or a complete Distance is reached. You can do part of the already Return treated water to the reactor or you can see several reaction units with gassing tank and reactor in front. About the amount of hydrogen used or multiple Be The water can be treated with any residual concentration the original content of oxygen or nitrite or Adjust nitrate in the treated water.  

The temperature during the treatment can be between 5 ° C and 95 ° C, preferably 10 ° C and 25 ° C.

The nitrite and / or nitrate degradation performance may vary depending on the Nitrite and / or initial nitrate concentration, the pH of the Hydrogen gas concentration or gassing rate and the tempe vary. With a palladium catalyst with 2% by weight Palladium and a maximum of the pore diameter at 850 Å can, for example, nitrite mining performances of over 20 mg Nitrite per hour and gram of catalyst can be achieved. With a catalyst doped with palladium and copper 2% by weight of palladium and 0.5% by weight of copper on aluminum oxide a maximum of the pore diameter at 850 Å can, for example Wise nitrate breakdown of 15 mg and more nitrate per Hour and grams of catalyst can be achieved.

In the following, the manufacture of the one to be used is new like supported catalyst described. The production of the Supported catalyst is characterized in that amorphous Alumina (modification "chi") with alumina hydrate with Exception of beta aluminum monohydrate in weight ratio 33.69: 20.5 to 44.21: 7.17, if necessary with the addition of water, mixed together, brings into the desired shape, 4.5 to For 6.5 hours at a temperature of 1045 to 1055 ° C cal coated, impregnated with the metal component and calcined.

It applies that the maximum of the pore diameter and the average pore diameter shifted to higher values be, the higher the calcination temperature and calcination takes longer. The BET surface area decreases the higher the calcining temperature and the longer the calcining tion continues.

The amorphous aluminum oxide used as the starting material is advantageously in finely divided form, for. B. in the form of particles with a diameter below 1 micrometer. It can, as described in EP-A-01 76 476, be produced by flash drying of fine-grained aluminum hydroxide. Its water content is between 3 and 8% by weight. Amorphous aluminum oxide with the designation HLS® from Martinswerk GmbH, Bergheim, has proven to be particularly useful. This is a rehydratable amorphous alumina with an alumina content of 96%. The sodium oxide content is between 0.2 and 0.35%, the water content is approx. 4%. It is very finely divided, 99% of the particles have a diameter of less than 1 micrometer. The specific surface is about 200 m ² / g.

The other aluminum oxide starting material, preferably alpha-aluminum oxide monohydrate (boehmite, pseudoboehmite) is expediently in the form of particles with a diameter of less than half of 100 micrometers. The commercial products PURAL NF® and PURAL SB® from Condea Chemie, Brunsbüttel and the commercial product CATAPAL B® from Vista Chemical Company have proven to be particularly suitable. PURAL NF® is a boehmite (alpha aluminum monohydrate) with 70% aluminum oxide, maximum 0.005% sodium oxide. The specific surface after activation for three hours at 550 ° C is at least 160 m ² / g. At least 99% of the particles have a diameter of less than 100 microns. The commercial product PURAL SB® typically consists of 75% aluminum oxide, and the sodium oxide content is typically a maximum of 0.002%. PURAL SB® is also a boehmite, its surface after three hours of activation at 550 ° C is typically 250 m ² / g. At least 90% of the particles have a particle size of less than 90 microns. The commercial product CATAPAL B® consists of small boehmite crystallites, which are often referred to as pseudoboehmites. It typically consists of 70.7% aluminum oxide, the sodium oxide content is typically 273 m ² / g. CATAPAL B® is particularly well suited for the production of catalyst supports with a bimodal pore structure.

According to a preferred variant of the carrier, the Modifications "theta" and "kappa" in a weight ratio of 25:75 to 15:85, in particular 30: 70 to 10: 90. For the production Such a carrier is mixed with amorphous aluminum oxide and Alumina hydrate in a weight ratio of 37.90: 50.17 to 42.11: 9.83.

As far as the shape of the catalyst carrier is concerned, one can bring the starting material into any form in which one kera mixed carrier material usually brings. So you can too form a monolithic support. You can also put it in bulk Bring good shapes, for example in cylinder, extrusion Ling, cube, hemisphere, hollow sphere shape and others. Prefers you bring it in spherical shape. This is conveniently done after Method of "build-up granulation". This method is used in Ver publication by W. Peach in "Processing Technology" 4 (1966), Pages 177 to 191 and in EP-A-01 76 476 (US-A 46 37 908) described.

First a mixture of amorphous aluminum is created oxide and aluminum oxide hydrate, preferably alpha aluminum oxide monohydrate, and subject the mixture to water on a turntable of a build-up granulation. It is an advantage sticky, undersize and crushed oversize from a previous one Add granulation as a nucleating agent. That through construction Spherical alumina is then produced expediently aged by standing and the desired frak sifted tion. The undersize and, after appropriate chopping The oversized grain can also be used as a nucleating agent in the granulation can be recycled. This is due to the build-up granulation material obtained is then dried and as described above calcined and transferred into the catalyst support material.  

The for setting the desired properties important parameters calcination time and calcination temperature ture depending on the output used material fluctuate slightly. If you want you can Determine the ideal process parameters through a few preliminary tests. For example, you increase the temperature and increase it Share in "theta" and "kappa" modification at the expense of any Shares in "delta" or "gamma" modifications. Is the share too large an "alpha" modification, so you lower the calcine temperature. To the pore maxima or the middle You can move the pore diameter to higher values Increase the calcination temperature or ver prolong. In the opposite case, the calcina is reduced tion temperature or shortens the calcination time. Ever because of the part of the modifications one can X-ray spectro determine the specific surface, the pore volume and the pore distribution are determined by mercury Porosimetry. The maxima of the pore diameter and the mean Pore diameters can be determined from this.

If desired, you can put the alumina in front of the calci pre-temper kidneys, e.g. B. up to several hours. So can one for 2 to 6 hours at temperatures between 550 and Pre-heat 650 ° C.

An advantage of the build-up granulation process is that the aluminum oxide into particles with a very variable diameter can roll. So the diameter z. B. from 0.1 to 20 mm wear. Rolling to spherical particles is preferred a diameter of 0.1 to 1.0 mm, in particular 0.3 to 0.8 mm. The grain spectrum shows a very ge with the method ring spread, the largest and the smallest particles vary in diameter by no more than 0.2 mm. Naturally you can still in the particles in the course of the manufacturing process divide special fractions, e.g. B. by sieving.  

The calcined supports can be converted into the supported catalysts in a manner known per se. For example, salts or complex compounds of palladium, rhodium or the element of the copper group can be applied to the support material in the impregnation process, spraying process or precipitation process and, if desired, reduced after drying and subsequent calcination. The carrier material can, for example, be soaked or sprayed and dried with a solution or suspension of metal salts or complex metal compounds in water or an organic solvent, for example a lower alcohol such as ethanol or ketone, or mixtures thereof. After drying, they can, if desired, also be calcined at temperatures up to 600 ° C, for example between 300 and 600 ° C. If desired, a reduction with a metal-free reducing agent, preferably hydrogen or, if appropriate, also another reducing agent such as NaBH ₄ , LiAlH ₄ , hydrazine, formaldehyde, carbon monoxide or methane under thermal treatment at temperatures in the range up to 550 ° C., for example between approx. 100 and 550 ° C, then connect.

The supported catalyst to be used in the process is so stable that the method z. B. for oxygen removal too in extreme conditions, e.g. B. Temperatures up to 120 ° C and more and a pressure of up to 40 bar and more can be led.

A continuously feasible fixed bed process and a system that can be used for this purpose is described in EP-A-03 59 074 described. The water is first placed in a dosing tank passed in which the pH can be measured, then through a disinfection device, finally via a pump by one or more reaction units made of hydrogen Fumigation container and fixed bed reactor. The system can still include further measuring devices, for example flow measurement  devices, pressure measuring devices, pH measuring devices, temperature measuring devices. The treated water can then be subjected to pH adjustment will.

For carrying out the method according to the invention in the fluidized bed or suspension layer is as follows described system particularly well suited. It includes one Pressure booster with liquid inlet and liquid outlet in which the untreated water is pressurized can be hit. The pressure booster is with connected to a hydrogen entry device, the one Has hydrogen inlet. Be with the hydrogen entry direction is a fluidized bed, suspension bed or flow bed reactor connected to the special described above Has supported alumina catalyst. This reactor points also a liquid inlet and liquid outlet for the water on. The system components described above are connected by pipelines to transport the water. Before preferably, the system has 2 filter devices that before the pressure increasing device or after the reactor are. The system can also have a pH measuring and dosing container Have control device, the front and / or behind the printer elevation device is arranged. If desired, in the pipelines or the system parts still measuring points Determination of analytical data of the water should be appropriate for example, pressure measuring devices, flow measuring devices and / or temperature measuring devices.

A disinfection device can be provided. Before the plant has no disinfection device.

The gassing unit preferably has a permeation membrane for hydrogen entry, e.g. B. a silicone hose. Permeation membranes are also very suitable porous, water-resistant polymer formed support structure grasp and at least one layer of water-resistant,  pore-free polymer, the water to be treated on the Side of the layer made of water-resistant, non-porous polymer is in contact with the membrane. Are very suitable for for example integral asymmetric membranes, e.g. B. made of poly ethamide. Membranes that are particularly suitable additionally with water-resistant, hydrophobic, non-porous poly mer, preferably silicone polymer, are coated. Such mem Branches are known as composite membranes. The fumigation Unit can be designed, for example, as a hollow fiber module. Such a hollow fiber module has a large number, for example dozens or hundreds of hollow threads. For example, 100 up to 500 hollow threads in the form of composite membranes in one hollow thread module can be summarized. The hollow threads are over one Distributor with a supply line for the water to be treated and via a collector with a discharge for the fumigated water connected. The water is passed through the hollow threads. The pressure-tight lockable module also has a supply line for the hydrogen gas in the surrounding the hollow filaments Space is pressed and then through the wall of the hollow fibers in the Water to be fumigated diffuses and entered there without bubbles becomes.

The method according to the invention has some surprising ones Advantages on. Due to the high selectivity of the use the supported catalysts do not cause any pollution By-products, due to the high mechanical stability and Abrasion resistance of these catalysts can the fiction moderate process over a long period of time without loss of catalyst activity and without the need to exchange kata lysators are described. Particularly advantageous both in The through is economical as well as hygienic implementation of the method according to the invention when using a spherical supported catalyst in the fluidized bed. It is completely surprising that bacterial contamination of the catalyst could affect its catalytic activity and also in Hygienic is not desirable, even without additional disinfection is effectively suppressed.  

The following examples are intended to further illustrate the invention explain, but without restricting its scope.

Examples

General:
The catalyst supports, the production of which is described in the following examples, were subjected to a test which compared the relative abrasion resistance of different supports. This determination of the relative abrasion resistance was carried out as follows: 1.0 g in each case of the material to be examined was weighed into a 10 ml snap-lid glass (45 × 22 mm) and rinsed twice with 5 ml of deionized water (demineralized water) to remove any remove sticking dust. The superficially adhering water was sucked off with a capillary so that only the water in the pores remained in the material. 5 ml of demineralized water were then added again and the sealed glass was shaken for 1 minute on a test tube shaker (Heidolf, Reax 1R) at 2400 revolutions per minute. 2 ml of the supernatant solution were then immediately transferred into a 10 mm cuvette and the extinction value E was measured several times after repeated shaking at λ = 500 μm (spectral photometer CADAS 100, company Dr. Lange). With E values that are greater than 1, the sample must be diluted accordingly, where the linearity of the measured values is given.

Mechanically stable and therefore abrasion-resistant carrier or catalytic converter gates show E values in the loading under these test conditions range from 0.1 to 0.7.

Examples 1 to 7: Preparation of the carrier material example 1

Manufacture of aluminum oxide supports with monomodal pore ver division, maximum pore diameter at 850 Å.

The method of build-up granulation was used. 140 kg Nucleating agent (undersize from an earlier build-up granulation with 70 wt% alumina and 30 wt% water, particle size less than 0.5 mm) were sprayed with 3 l of water.

Then 105 kg of an alumina mixture were produced provides by amorphous, highly disperse alumina (commercial product HLSR® from Martinswerk, Bergheim) and aluminum oxide from Boehmite type (commercial product Condea Pural SB® from Condea, Brunsbüttel) in a weight ratio of 40: 12.5 to each other were mixed. This alumina mixture was put together placed in a turntable with the 140 kg nucleating agent. The rotating mass were approximately 4 hours 32.6 kg of water sprayed.

Then again 132 kg of those described above Alumina mixture with the specified weight ratio of amorphous alumina and boehmite-type alumina added to the mass in the turntable. In the course of Then another 2.5 kg of rotating water was added for 2.5 hours Mass sprayed. Then the mass was added for another 20 minutes rolls and aged for 16 hours in the stationary turntable.

With the addition of 3 kg of water, the aged mass was still rolled once in the turntable for 15 minutes and then sieved. Undersize (particle diameter less than 0.5 mm) and Oversize (particle diameter greater than 0.68 mm) after crushing were used as nucleating agents in a later build-up granulation guided.  

The fraction with a particle size of 0.5 to 0.68 mm was then dried at 150 ° C for 16 hours.

Yield:
188 kg dry material of the composition 85 wt .-% aluminum oxide, residual water.

10 kg of material were then removed from the pre-dried material, which is predried for 4 hours at 600 ° C and then calcined at 1050 ° C for 5 hours.

Yield:
8.5 kg of spherical aluminum oxide, consisting of the modifications "theta" and "kappa" with traces of the modification "alpha". The material was free from the "gamma" and "delta" modifications.

Maximum pore diameter:
850 Å. The diameter of the pores is in a range between about 60 Å and 1800 Å
Relative abrasion number: 0.63
Specific surface area, measured according to the mercury porosimetry method: 45 m ² / g,
Pore volume: 0.40 ml / g
Average pore diameter: 356 Å.

Example 2

Production of a monomodal carrier with a maximum of Pore diameter at 950 Å.

10 kg of the starting material prepared according to Example 1 were first predried at 600 ° C. for 4 hours and then calcined at 1050 ° C for 6 hours.  

Yield:
8.5 kg spherical alumina. It consisted of the modifications "theta" and "kappa", the modification "alpha" was only detectable in traces.

Maximum pore diameter:
950 Å. The diameter of the pores is in a range between 80 and 1800 Å
Relative abrasion number: 0.64
Specific surface area: 35 m ² / g,
Pore volume: 0.39 ml / g.
Average pore diameter: 446 Å.

Example 3

Production of a monomodal carrier with a maximum of Pore diameter at 850 Å.

Example 1 was repeated in place of the alumina The Pural SB® brand became the commercial product as aluminum oxide Pural NF® (also a boehmite) from Condea-Chemie used.

10 kg of the dry material produced analogously to Example 1 were used as starting material. The material was back first predried at 600 ° C for 4 hours, and then Calcined at 1050 ° C for 5 hours.

Yield:
8.5 kg spherical alumina. It consisted of the modifications "theta" and "kappa", the modification "alpha" was only detectable in traces.

Maximum pore diameter:
850 Å. The diameter of the pores is in a range between 80 and 1400 Å
Relative abrasion number: 0.44
Specific surface area: 46 m ² / g
Pore volume: 0.39 ml / g
Average pore diameter: 339 Å.

Example 4

Production of a monomodal carrier with a maximum of Pore diameter at 1000 Å.

10 kg of the starting material prepared in Example 3 were predried for 4 hours at 600 ° C and then Calcined at 1050 ° C for 6 hours.

Yield:
8.5 kg spherical alumina. It consisted of the modifications "theta" and "kappa", the modification "alpha" was only detectable in traces.

Maximum pore diameter:
1000 Å. The diameter of the pores is in a range between 100 and 1800 Å.
Relative abrasion number: 0.69
Specific surface area: 33 m ² / g,
Pore volume: 0.42 ml / g
Average pore diameter: 509 Å.

Example 5

Production of a bimodal carrier with maxima of the pores knife at 115 and 1400 Å.

First, starting material was prepared analogously to Example 1. Instead of the aluminum oxide PURAL SB®, CATAPAL B® became the Vista Chemical Company used.  

10 kg of the dry material produced as in Example 1 as off Initial material was first pre-4 hours at 600 ° C. dries and then calcined at 1050 ° C for 5 hours.

Yield:
8.5 kg spherical alumina. It consisted of the modifications "theta" and "kappa", the modification "alpha" was only detectable in traces.

Maxima of the pore diameter:
150 Å and 1400 Å. The diameter of the pores is in a range between 80 and 4000 Å
Relative abrasion number: 0.50
Specific surface area: 41 m ² / g, pore volume: 0.46 ml / g
Average pore diameter: 449 Å.

Example 6: (comparative example)

10 kg of the starting material prepared according to Example 1 was pre-dried for 4 hours at 600 ° C and then Calcined at 900 ° C for 2 hours.

Yield:
8.5 kg spherical alumina. It consisted of the modifications "delta" and "kappa", the modification "gamma" was detectable in small proportions.
Maximum pore diameter: 220 Å
Relative abrasion number: 1.03.

Example 7: (comparative example)

10 kg of the starting material prepared in Example 1 were predried for 4 hours at 600 ° C and then Calcined at 1100 ° C for 4 hours.  

Yield:
8.5 kg spherical alumina. It consisted of the modification "alpha", the modifications "theta" and "kappa" were detectable in small proportions.
Maximum pore diameters: 1260 Å and 110,000 Å
Relative abrasion number: 1.9.

From Examples 1 to 7 it can be seen that the rela tive abrasion number as a measure of the abrasion resistance has valid values (i.e. below 0.7) if one When calcining, make sure that the "delta" modification not and the "alpha" modification at most in minor Share in the carrier arises.

Figs. 2 to 8 give the distribution of the pore diameter in the support material of Examples 1 to 7 again.

Examples 8 to 15

Manufacture of supported catalysts

Example 8

Preparation of a supported catalyst containing Pd and Cu with Maximum pore diameter at 850 angstroms.

The carrier mat produced according to Example 1 was used rial. It became a particularly favorable fraction with a grain size range of 400 to 680 microns, the an upper or lower grain fraction of less than 3% each pointed, used. The grain size distribution within the Be 400 to 680 microns followed the normal distribution.

The catalysts were produced by applying the catalytically active metal compounds on the support material, one of the following methods was used.

• a) In 219 ml of an aqueous tetraammonium palladium (II) - Hydroxide solution with a palladium content of 2.74 g / l, d. H. a total content of 0.6 g palladium, were in one 250 ml round-bottom flask 30 g of that prepared according to Example 1 Carrier material of the above-mentioned fraction introduced. The solution was at 60 ° C for 2 hours and 30 mbar evaporated to dryness, the obtained imp gnierte carrier dried at 110 ° C for 1 hour and the dried carrier calcined at 550 ° C for 0.5 hours.

The application of Copper. To prepare the copper salt solution, 0.47 g Copper (II) acetate monohydrate (corresponding to 0.15 g copper) in 100 ml of deionized water dissolved. The impregnated support was then dried at 110 ° C for 2 hours. To the Reduk tion of the metals was the impregnated and dried Trä 8 hours at 350 ° C in an externally heated quartz tube exposed to a hydrogen atmosphere.

According to the analysis, the finished catalyst had a palladium content of 2.0 ± 0.05% by weight and a copper content of 0.5 ± 0.02% by weight. The relative abrasion number corresponded to the abrasion Number of substrates.

• b) In a solution of 1.68 g of palladium dichloride, which corresponds 1.0 g palladium, in 11.75 ml 1 molar hydrochloric acid and 22.7 ml Acetone was in a 250 ml round bottom flask according to 50.42 g Example 1 prepared carrier material of the above Fraction introduced. The solution was on for 30 minutes closed on a rotary evaporator, stirred. The Lö agents were added over a period of 60 minutes 60 ° C and 50 mbar evaporated. The one impregnated with palladium The carrier was then dried at 150 ° C for 1 hour and Calcined at 550 ° C for 0.5 hours. To apply the Copper was the carrier impregnated with palladium in a  Solution of 0.79 g copper (II) acetate monohydrate, the ent speaks 0.25 g of copper, placed in 30 ml of water and as before described in the rotary evaporator. The then impregnated with palladium and copper Dried at 100 ° C for 1 hour and finally how described under a), reduced.

The analysis corresponded to that obtained by method a) Values.

Example 9

Production of a supported catalyst containing only palladium tors with a maximum pore diameter at 850 angstroms.

Analogously to Example 8, the one obtained according to Example 1 was obtained Carrier impregnated with palladium. The impregnated with palladium gnierte carrier was dried at 110 ° C for 1 hour, at Calcined at 550 ° C and reduced with hydrogen.

The finished catalyst had a palladium content of 2.0 + 0.05% by weight. Relative abrasion number, distribution of the pores knife, specific surface area, pore volume and average Pore diameters corresponded to the values of the carrier material.

Example 10

Production of a support catalyst containing palladium and copper analyzer with a maximum pore diameter at 950 Å.

Example 8 was repeated analogously. This time, however, that was in Example 2 produced carrier material used. The received one Supported catalyst had a palladium content of 2.0 ± 0.05% by weight Palladium and 0.5 ± 0.02 wt .-% copper. Abrasion number, distribution of pore diameter, specific surface, Pore volume and average pore diameter corresponded to that Carrier material values.  

Example 11

Production of a support catalyst containing palladium and copper analyzer with a maximum pore diameter at 850 Å.

Example 8 was reworked analogously. This time, however the carrier material obtained in Example 3 is used. The Palladium content was 2.0 ± 0.05% by weight of palladium, the copper content 0.5 ± 0.02% by weight, abrasion number, distribution of the pores diameter, specific surface area, pore volume and average Pore diameters corresponded to the values of the carrier used materials.

Example 12

Production of a support catalyst containing palladium and copper analyzer with a maximum pore diameter at 1000 Å.

Example 8 was followed up analogously, but this time was the carrier material produced in Example 4 is used. The The supported catalyst obtained had a palladium content of 2.0 ± 0.05% by weight and a copper content of 0.5 ± 0.02% by weight. Abrasion number, distribution of pore diameters, specific surface area, pore volume and average pore diameter corresponded the values of the carrier material used.

Example 13

Preparation of a bimodal containing palladium and copper Supported catalyst with maxima of the pore diameter at 115 and 1400 Å.

Example 8 was followed up analogously, but this time was the carrier material obtained in Example 5 is used. The he supported catalyst had a palladium content of 2.0 ± 0.05% by weight and a copper content of 0.5 ± 0.02% by weight.  

Abrasion number, distribution of pore diameters, specific surface area, pore volume and average pore diameter correspond Chen the values of the carrier material.

Example 14: (comparative example)

Production of a supported catalyst with a maximum of Pore diameter at 220 Å.

Example 8 was reworked analogously. This time it was in accordance Example 6 prepared carrier material used. The finished one Catalyst contained 2.0 ± 0.05% by weight of palladium and 0.5 ± 0.02% by weight Copper. Abrasion number, distribution of pore diameter, specific surface area, pore volume and average Pore diameters corresponded to the values of the carrier used materials.

Example 15: (comparative example)

Example 8 was reworked analogously. This time it was in accordance Carrier material produced in Example 7 is used. The finished one Catalyst contained 2.0 ± 0.05% by weight of palladium and 0.5 ± 0.02% by weight Copper. Abrasion number, distribution of pore diameters, specific surface area, pore volume and medium pores diameter corresponded to the values of the carrier material used rials.

Examples 16 and 17: Use of supported catalysts for Nitrate reduction Example 16

Use of the palladium produced according to Example 8 and Support catalyst containing copper to remove Oxygen and nitrate from water in the fluidized bed.  

Equipment used:
A raw water pipe led first into a suspended matter filter and then into a pressure increasing device. A line led from the pressure increasing device into a gassing reactor. In this gassing reactor, hydrogen could be introduced into the water via silicone membranes. The gassing reactor was connected to a reactor which carried out the catalytic oxygen and nitrate degradation. This reactor contained 22 kg of the supported catalyst prepared according to Example 8 using the support material of Example 1 and containing palladium and copper. An outlet line for the treated water leading out of the reactor led into a suspended matter filter. The water leaving the suspended matter filter could then be fed to the respective application as pure water.

Carrying out the experiment:
The test was carried out over a period of over 9 weeks in a waterworks in Lower Saxony. The nitrate content of the raw water (groundwater) fluctuated between 40 mg and 60 mg per liter. The oxygen content was 4.2 mg / l. The temperature of the raw water was 11 ° C.

The raw water was first passed through the suspended matter filter and then brought to a water pressure of 5 bar in the pressure increasing device. The water was gassed with hydrogen in the gassing reactor. The hydrogen-laden water was passed through the reactor at a flow rate of 2000 liters per hour, in which the supported catalyst material was kept in the fluidized bed. Both the nitrate content of the nitrate-contaminated groundwater to be treated and the nitrate content of the treated groundwater were recorded over a period of more than 9 weeks. Of FIG. 1 Kgs NEN nitrate concentrations of the untreated or the be treated groundwater that were determined over a plurality of measurements are taken. The nitrate degradation performance could be determined at 3.5 g of nitrate per kilogram of catalyst per hour. As shown in FIG. 1, the catalyst is stable for months and provides consistently good results even with fluctuating amounts of nitrate.

Some analysis data of the untreated and treated reason water are summarized in the following table.

Table 1: Analysis data of the untreated or treated groundwater

The supported catalyst prepared according to Examples 9 to 13 gates also proved to be stable over the long term. Your selekti Nitrate depletion was very good.

The Trä prepared according to Comparative Examples 14 and 15 On the other hand, catalytic converters showed neither with regard to Ab rub resistance with regard to the selectivity at Nitrate degradation has satisfactory properties.  

Example 17

Implementation of the removal method according to the invention of oxygen and nitrate from water in one batch liche stirred reactor.

The reaction was carried out in a batch mode Stirred reactor carried out, which a 250 ml containing reactor with a magnetic stirrer, in which Hydrogen at the bottom with a porous plastic hose Needle valve for setting the hydrogen volume flow could be directed. The apparatus was also with one Provide pH measuring and control unit, whose are in the reactor Liche pH measuring electrode that takes place during the reaction Measure the deviation of the pH value from the initial pH value and over a metering device to change the pH by adding can balance from aqueous dilute hydrochloric acid solution. The acid volume metered in to keep the pH constant, which is proportional to the amount of nitrate converted has been determined recorded on a chart recorder.

240 ml of water with a nitrate content of 50 mg / l and a pH of 6.0 and 2.0 g of the acc given game 8 supported catalyst. The tempera tur in the reactor was set to 10 ° C, and it was with Fumigated hydrogen with a gassing rate of 30 l / h. To The nitrate was completely degraded in 68 minutes. The specific Nitrate degradation performance of the catalyst up to the complete change Set of 50 mg of nitrate in 240 ml of water was on for 1 hour and 1 g of catalyst calculated.

Specific nitrate degradation performance:
5.5 mg nitrate / h × g catalyst.

Claims (13)

1. Continuous feasible removal process reduction or reduction of the oxygen content, the nitrite and / or nitrate content of oxygen-containing and / or nitrite and / or nitrate contaminated water under selective Nitrogen formation, whereby one into the oxygen-containing, nitrite and / or nitrate-contaminated water introduces hydrogen gas and that water loaded with hydrogen contact with a catalyst tiert, which is formed from a palladium and / or rhodium or of palladium and a metal of Copper group existing metal component impregnated porö sen carrier, the carrier made of alumina of the Modification "theta" and "kappa" and the modification "alpha" is not present or at most in small quantities and the Carrier is free of aluminum oxide of the "gamma" modifications and "delta" and either a monomodal distribution of the pores diameter with a maximum in the range between 700 Ä and 1500 Å, or a bimodal distribution of the pores knife with two maxima in the range from 100 to 1500 Å, the average pore diameter being between 300 and 500 Å carries, and one for the treatment of only nitrite contaminated water a catalyst, the metal component of palladium and / or rhodium and, if the water to be treated also contains nitrate, a catalyst whose metal component from palladium and a metal from the copper group or from Rho dium and optionally palladium, or a mixture from a catalyst, the metal component of palladium and a metal of the copper group, and a catalyst sator, whose metal component consists only of palladium sets, and the pH of the water does not exceed 8 can rise and the process behind as often as necessary each other until the oxygen content, the nitrite content  and / or the nitrate content of the water removed or on one tolerable value is reduced. 2. The method according to claim 1, characterized in that one uses a supported catalyst, the specific BET surface area, measured by the mercury porosimetry method, is between 41 and 50 m ² / g. 3. The method according to claim 1 or 2, characterized net that one uses a catalyst, which is a monomo dale distribution of pore diameters with a maximum of Pore diameter in the range between 800 Å and 1250 Å points. 4. The method according to any one of the preceding claims characterized in that a spherical support catalyst verator with a particle size between 0.1 mm and 1.0 mm ver turns. 5. The method according to claim 1, characterized in that Palladium and as metals of the copper group copper or silver, preferably copper, can be used as the metal component. 6. The method according to claim 1, characterized in that the proportion of the metal component in the total catalyst between 0.1 and 10 wt .-%. 7. The method according to claim 6, characterized in that the catalyst has a palladium content of 0.5 to 5, preferably as 0.5 to 3 wt .-%, based on the total weight of the kata contains lysators. 8. The method according to claim 1, characterized in that a catalyst impregnated with palladium and copper is set.   9. The method according to claim 8, characterized in that the weight ratio of palladium to copper between 2: 1 and 8: 1, preferably 3: 1 and 5: 1. 10. The method according to claim 1, characterized in that one uses a catalyst system which consists of catalyst Particle is formed, part of which with palladium and a metal from the copper group, in particular copper and a other part is only impregnated with palladium. 11. The method according to claim 1, characterized in that such an amount of hydrogen is introduced into the water, which is at least that to reduce the predetermined content of stoichiometric oxygen and nitrite and / or nitrate manoeuvrable amount of hydrogen and at most a 20 wt .-% Excess corresponds to this amount. 12. The method according to claim 1, characterized in that that you use water containing 0.1 to 20 mg / l nitrite and / or 5 to 600 mg / l nitrate is loaded. 13. The method according to any one of the preceding claims, since characterized in that you go through it in the fluidized bed leads.