DE2538463A1 - Vanadium-phosphorus (V) catalyst for thermal treatment of wastes - contg. halogens, hydrogen halides, carbon and heavy organic matter - Google Patents

Abstract

Wastes from chemical processes contg. halogens and/or hydrogen halides and elemental carbon and/or a heavy organic residue and opt. water are reacted with oxygen or an O2-contg. gas at 300-700 degrees C in the presence of a catalyst system comprising V2O5 and an oxygen-contg. cpd. of P(V) on an inorganic carrier (having a specific surface area of 250-600 m2/g). The halogens and/or the hydrogen halides are sepd. from the gaseous reaction prods. by condensation or absorption in water. CO2 is released to the atmos. Complete combustion of carbon is achieved. The economy of the process is good because the fuel consumption is less than in the known processes.

Description

Process for the processing of water-containing mixtures, the halogens and / or contain hydrogen halides. The present invention relates to a method for the work-up of optionally water-containing mixtures, in addition to halogens and / or hydrogen halides, carbon and / or non-volatile organic residues contain by catalytic combustion with oxygen or containing oxygen Gases, in numerous chemical processes, e.g. B. in the photosynthesis of N-nitroso-N-cyclohexylamine-potassium waste water occurs which, in addition to halogens and / or hydrogen halides, is elementary Carbon and / or organic compounds that cannot be defined in detail, which have practically no vapor pressure, such wastewater can because of their Content of toxic halogens or hydrogen halides for environmental reasons can be discarded without further ado, but these substances must be removed beforehand, A currently common method of cleaning such mixtures is incineration in the open flame or in the muffle at temperatures of over 10000C. The halogens or hydrogen halides are then recovered by absorption with water. C02 is released into the atmosphere as a combustion product.

Since these waste mixtures usually contain little carbon, must the high temperatures required in these processes through the combustion of auxiliary fuels such as methane, petrol, etc. are produced. Due to the increasing price of Fuels, however, these processes are becoming less and less economical.

In U.S. Patent 3,453,073 there is a method of recovery of hydrogen chloride from chlorinated hydrocarbons, in particular lower hydrocarbons with 1 to 2 carbon atoms described therein consists of a gaseous mixture of the chlorinated hydrocarbons, water and oxygen through a bed of acidic oxidation catalyst at temperatures conducts from 300 to 600ob and the hydrogen halide formed in the process from the exhaust gases separates. Supported catalysts can be used as catalysts, which as active mass oxides of aluminum, silicon, phosphorus, vanadium, molybdenum and chromium contain. A mixture of molybdenum trioxide is used as the preferred catalyst Phosphoric acid called, which is applied to activated carbon as the preferred carrier. It has been shown that the catalysts mentioned are not suitable for a complete combustion of the carbon or the organic residues in the To achieve the aforementioned aqueous mixtures and that these catalysts continue lose their activity quickly.

The object of the present invention was to provide a method for working up optionally water-containing mixtures, the halogens and / or Hydrogen halides in addition to elemental carbon and / or non-volatile organic compounds Contain residues, to provide a complete incineration of carbon achieved.

It has been found that this object can be achieved in that the mixtures together with oxygen or gases containing oxygen Temperatures of 300 to 700 ° C. in the presence of a supported catalyst with one another converts, the halogens and / or from the gaseous reaction products formed Separates hydrogen halides, with the proviso that a support catalyst is used used, the active mass of vanadium pentoxide in combination with oxygen compounds of pentavalent phosphorus.

As a carrier material PUr the catalysts are advantageous per se known inorganic materials such as aluminum oxide, silica, aluminum silicate, Magnesium silicate with a large surface, e.g. B. with 250 to 600 m2 / g, used. For application the active mass are the carriers with solutions of vanadium salts, e.g. B. Solutions of ammonium vanadate, which are used to increase solubility Oxalic acid has been added, as well as with phosphoric acid or its aqueous solutions soaked, then dried and at elevated temperatures of 300 to 60o0c in an oxygen-containing gas stream, e.g. Bo air, or oxygen, into the active Form transferred. Here the vanadium is converted into the oxide form and the phosphoric acid converted into phosphorus pentoxide, which also at least partially with the carrier material or the vanadium can be present in the form of mixed oxides.

The supported catalysts contain appropriately, based on the support 1 to 30 percent by weight vanadium, calculated as V205 and 1 to 25 percent by weight Phosphorus calculated as P205.

A particularly suitable silica carrier can be gelled from gravel produce. For the production of the gel one goes, for example,

of solutions of sodium silicate solution with a density of 1.10 up to 1.25 vcp, allows this to react with a mineral acid with thorough mixing, z. B. 20 to 35 weight percent sulfuric acid, with a pH of 7 not is exceeded, This is a silica gel via the intermediate stage water-rich silicic acid hydrogel prepared, the appropriate with ammoniacal Water, e.g. B. 0.1 to 0.2 weight percent ammonia solution is washed. That So largely desalinated hydrogel is then with 2 to 10 weight percent of a peptizer, z. B. a mineral acid such as sulfuric acid, hydrochloric acid, but also phosphoric acid even, moistened, the advantageous 5 to 15 percent by weight, based on the too treating hydrogel, oxalic acid may be added. The mixture is 1 to 2 hours treated in the mill or another device that generates shear forces, where peptization occurs. The peptized mass thus obtained is then in one 300 to 60o0c hot gas stream, z. In a flue gas stream, sprayed and then, as described above, applied to the active mass. However, it is also possible to introduce the active mass during the manufacture of the carrier, e.g. B. by that the peptization is carried out with phosphoric acid and the hydrogel mass before or add the required amount of yanadin even after spraying.

The inventive method can be used both with an arrangement of the Catalyst in a fixed bed, as well as particularly advantageous in a fluidized bed of the catalyst are carried out, the z. B, through the oxygen-containing gases is operated. The catalysts for the fixed bed reaction can take the form of spheres, Have strands with diameters of 2 to 10 mm, for implementation in one In a fluidized bed, particles are expediently placed, e.g. B. in the form of balls, with grain diameters from 60 to 1000 / u.

The process according to the invention can be used for work-up of aqueous mixtures containing chlorine or hydrogen chloride or bromine or hydrogen bromide contained in dissolved form0 In the case of bromine, mixtures can also be processed that contain are anhydrous or largely anhydrous.

Oxygen is stoichiometric in relation to the carbon content Amount up to a four-fold excess over the stoichiometrically required amount used.

The halogen or hydrogen halide is turned on from the exhaust gases known way, e.g. B. by condensation and subsequent absorption of the not recovered condensed portion in water, while that formed in the reaction Carbon dioxide can be released into the atmosphere.

Example 1 To produce a supported catalyst, 1000 ml a water glass solution with a density of 1.25 g / cm3 with 500 ml of sulfuric acid mixed, whereby the pH does not rise above 7.0. The resulting silica gel is largely desalinated with 0.1X ammoniacal water, then under Addition of 31 ml of phosphoric acid 98%, ground in a mill for one hour. the The resulting mass is sprayed into a stream of flue gas at 5000C, whereby silica particles are produced with an average grain diameter of 50 to 1000 / u.

1 kg of the powder produced in this way is mixed with a solution of 25.7 g Ammonium vanadate and 50 g of oxalic acid soaked in 2 liters of water, then dried and activated at 5000C for three hours in an air stream.

The finished catalyst contains 10 percent by weight, based on the support P, calculated as P205 and 2 percent by weight V, calculated as V20 e In in the scheme shown apparatus are from a template (1) via a metering pump (2) 250 g per hour of a contaminated 36 percent strength by weight aqueous hydrochloric acid with a C content of 3 percent by weight laterally in a fluidized bed consisting of 300 ml of a supported catalyst, the preparation of which has been described above, which is located in the reactor (3), supplied. The temperature is determined by the electrical Outside heating kept at 5000C. At the same time are over a frit every hour 50 liters of oxygen supplied.

The gas stream leaving the reactor is in a subsequent Condenser (4) cooled to 200C, a 20 percent by weight condenses aqueous hydrochloric acid, which is collected in template I (5). The not condensed Gases are in a downstream column loaded with packing (6) in countercurrent freed from gaseous HC1 with a 20 percent strength by weight hydrochloric acid. It will so much 20 percent by weight hydrochloric acid fed to the column that 36 percent by weight Hydrochloric acid is obtained at the outlet of the column. Carbon dioxide leaves at the head of the Column the apparatus.

The hydrochloric acid obtained is colorless to pale yellow, contains less than 0.1% C and can be reused without further purification.

Example 2 The procedure is as in Example 1, but a catalyst is used one made as described above, however no Contains phosphoric acid. The hydrochloric acid obtained after the oxidation is colored yellow, still contains 0.8% by weight of organically bound carbon and can be used in this form can no longer be used.

Example 3 In the apparatus described in Example 1, every hour 60 ml of a mixture with 95% by weight of bromine, some of which is elemental and some as hydrogen bromide and is partly organically bound, which is contaminated by 2.6% organic C is, remainder water, 300 ml of catalyst, which in contrast to Example 1 with 10 Ges.% V 0 and 10 wt. P, calculated as P205, is loaded, supplied.

25 An hourly 30 liters of O 2 are introduced into the fluidized bed from below. The temperature is kept at 3000C. The gas stream leaving the reactor is cooled to OOC in a condenser cooled with brine, which condenses in the process Main part of the bromine. The uncondensed gases that still contain bromine will in a downstream column in countercurrent with water or an organic one Liquid washed out.

The carbon content of the bromine purified in this way is c 0.02% by weight.

99% of the bromine is elemental in the oxidate, 1% is HBr certainly.

Example 4 The procedure is as described in Example 3, but sets a phosphoric acid-free catalyst with 10 wt.% V205. That after the oxidation The bromine obtained still contains 0.4% by weight of organically bound carbon. Through V205 alone, only 85% of the carbon is oxidized.

Example 5 Proceed as in Example 1, but set a V205-free one Catalyst with 10 wt% P, calculated as P205. The one obtained after the oxidation Hydrochloric acid is dark in color and still contains 80% by weight of the originally present Carbon.

Claims (6)

Claims 1. Process for working up mixtures containing halogens and / or Hydrogen halides in addition to elemental carbon and / or non-volatile organic compounds Contain residues and optionally water, characterized in that one the aqueous mixtures together with oxygen or oxygen-containing gases at temperatures from 300 to 7000C in the presence of a supported catalyst with one another converts, the halogens and / or from the gaseous reaction products formed Separating hydrogen halide, with the proviso that a supported catalyst is used, the active mass of vanadium pentoxide in combination with oxygen compounds of the contains pentavalent phosphorus. 2. The method according to claim 1, characterized in that as Supports inorganic supports with a surface area of 250 to 600 m2 / g. 3. The method according to claims 1 to 2, characterized in that that a silica is used as the carrier, which is obtained by peptizing a silica gel and then spraying into a heated gas stream. 4. The method according to claims 1 to 3, characterized in that that the supported catalyst, based on the support, 1 to 20 percent by weight of vanadium, calculated as V205, and contains 1 to 25 percent by weight of phosphorus, calculated as P205. 5. Process according to claims 1 to 4, characterized in that that the oxygen, based on the carbon content in the aqueous mixture, in the stoichiometric amount up to a four-fold excess over the stoichiometric required amount. 6. The method according to claims 1 to 5, characterized in that that the reaction is carried out in a fluidized bed of the supported catalyst. Sign. Blank page