EP0642809A1 - Environment friendly degradation and elimination of heteroatome containing compounds - Google Patents

Abstract

Process for the environmentally compatible degradation of chemical compounds which contain one or more heteroatoms X, X denoting F, Cl, Br, I, N, O or S, by cleavage of the C-X carbon-heteroatom bonds, characterized in that the chemical compounds or articles in which the chemical compounds are contained are treated with steam in the presence of an aluminium catalyst at 300-600 DEG C.

Description

Heteroatom-containing compounds, such as halogenated hydrocarbons or heterocycles, such as triazine compounds, are used in many areas. For example, halogenated hydrocarbons are used as solvents, as blowing agents, in the cleaning sector or as flame retardants. Other areas of application for heteroatom-containing compounds are, for example, the plastics industry or the agricultural sector.
Among other things, triazine compounds such as melamine and its secondary products, such as melamine-formaldehyde resins, are processed to a large extent to plastic objects or in the coating of wood fiber boards.
Since one day these compounds or objects or formulations containing these compounds also have to be disposed of again, their environmentally friendly disposal is of great importance.
Although it is known that the pyrolytic treatment of many heteroatom-containing compounds produces toxins, such as hydrocyanic acid, dicyan, isocyanic acid, no environmentally friendly disposal method has been found to date.

EP-A-0 051 156 describes that traces of melamine from exhaust gases in the presence of steam and copper and / or iron oxide-containing catalysts at 205 to 280 ° C up to about 90%, in the presence of aluminum catalysts from about 30 to at most 70% can be removed. However, according to EP-A-0 051 156, it is not possible to dispose of a large number of heteroatom-containing compounds, in particular triazine compounds, in an environmentally compatible and as complete a manner as possible.

It was an object of the present invention to find a process which ensures the most environmentally friendly and complete disposal possible for a large number of different compounds which have carbon-heteroatom bonds.

It has now been found, unexpectedly, that a wide variety of compounds having carbon-heteroatom bonds, such as halogenated hydrocarbons or heterocycles, in particular triazine compounds, can be degraded in an environmentally friendly manner if they are treated with steam at temperatures from 300 to 600 ° C. in the presence of an aluminum catalyst. Through this invention it is possible that in particular triazine waste can be completely and environmentally friendly.

The present invention accordingly relates to a process for the environmentally friendly degradation of chemical compounds which have one or more heteroatoms X, where XF, Cl, Br, J, N, O or S, by cleaving the CX carbon-heteroatom bonds, which thereby is characterized in that the chemical compounds or articles in which the chemical compounds are contained are treated with steam in the presence of an aluminum catalyst at 300-600 ° C.

In the process according to the invention, CX carbon-heteroatom bonds are split from chemical compounds which have one or more heteroatoms X. X means F, Cl, Br, J, N, O or S.
CX carbon heteroatom bonds include bonds from the group CF, C-Cl, C-Br, CJ, C-NH₂, C-NHR₁, C-NR₁R₂, C-NH-C, C-NR₁-C, C = NC, C-SH, CSC, CSSC, C = S, COC, C-OR₃, COOR₃ or C = O to understand. R₁, R₂ can be the same or different and represent an alkyl radical, preferably with 1 - 10 carbon atoms. R₃ can be H or an alkyl radical with 1 - 10 carbon atoms. Compounds which contain one or more of the above-mentioned CX bonds are therefore suitable as the chemical compound. These are, for example, aliphatic compounds which are substituted with one or more radicals from the group -F, -Cl, -Br, -J, -NH₂, - NHR₁, -NR₁R₂, -SH, = S, -OR₃, = O, -OOR₃ are. Aliphatic compounds are saturated, mono- or polyunsaturated, linear, branched or cyclic hydrocarbons such as alkanes, alkenes, alkynes, cycloalkanes, -alkenes, -alkynes. The hydrocarbons also include hydrocarbons which, optionally in combination with the above-mentioned substituents, contain CX bonds from the group C-NH-C, C-NR₁-C, C = NC, CSC, CSSC, COC in the hydrocarbon chain.
In addition to the substituents already mentioned, the compounds can have further substituents such as a phenyl radical.
Examples of these are trichloromethane, methylene chloride, dichloroethane, butyl iodide, dimethyl methane, butyl chloride, chlorocyclohexane, bromundecane, benzyl chloride, etc.
The chemical compounds which can be used by the process according to the invention also include aromatic compounds which are substituted by one or more radicals from the group F, Cl, B, J, NH₂, NR₁, NR₁R₂, OR₃ or SH. Aromatic compounds are preferred with aromatic hydrocarbon rings 5 - 14 carbon atoms, such as a benzene, naphthalene, indene, fluorene or anthracene ring.
In addition to the substituents already mentioned, the aromatics can also have further substituents, such as alkyl radicals.
Heterocyclic compounds can also be used as chemical compounds. Heterocyclic compounds are understood to mean rings with one or more heteroatoms from the group N, O or S, where the heterocycle can be, for example, a monocyclic, bicyclic or multiply condensed system. The heterocyclic compounds have CX bonds from the group C = NC, CSC, C-NH-C, C-NR₁-C, COC, in the cycle. Examples of heterocyclic compounds are pyrrole, pyridine, thiophene, indole, thionaphthene, pyrazole, benzimidazole, thiazole, triazoles and triazines.
The heterocyclic compounds can be substituted with one or more heteroatoms X and thus one or more bonds from the group CF, C-Cl, C-Br, CJ, C-NH₂, C-NHR₁, C-NR₁R₂, C-SH, C = S, COR₃, COOR₃ have. If appropriate, the heterocyclic compounds can also be substituted by additional radicals, such as alkyl radicals. Preferred heterocyclic compounds are triazine compounds.
The triazine ring is a benzene nucleus in which three carbon atoms are replaced by nitrogen atoms. Preferred triazine compounds contain 1,3,5-triazine. The 1,3,5-triazine is contained, for example, in cyanuric acid and its derivatives, of which in particular the cyanuric triamide, known under the name melamine, has gained great industrial importance. Polycondensation with aldehydes, in particular with formaldehyde, gives rise to the important melamine resins which are used to a large extent, for example for the manufacture of electrical insulators, articles of daily use, such as plates, cups or for coating materials, in particular wood fiber boards. 1,3,5-triazines are also found in agricultural chemicals such as atrazine and fire protection compounds. An item that contains triazine compounds also includes, for example, field formulations that contain atrazine or fire protection compositions that are to be destroyed. The process for the environmentally friendly removal of melamine-formaldehyde resin, agricultural chemicals which contain the triazine ring or for removal of the melamine-formaldehyde resin from a waste product which contains such a resin is preferably used.

Objects which contain the chemical compounds and which can be disposed of by the process according to the invention are therefore, for example, plastics, Agricultural chemicals, fire protection compounds, clamping plates and coated objects.
The CX bonds of the above-mentioned chemical compounds are cleaved by the process according to the invention in the presence of an aluminum catalyst.

Aluminum catalyst is to be understood as a catalyst which contains an aluminum compound such as aluminum oxide, AlOOH, aluminosilicate, spinels as an active ingredient. In addition, the catalyst can also contain other metals, such as silver, copper, iron, cobalt, nickel, titanium, manganese, chromium or mixtures thereof, preferably in the form of their oxides. A catalyst which consists of aluminum oxide or which contains aluminum oxide as the main component is very preferred. The catalyst can be used in the usual form, for example in the form of tablets, pellets, particles, spheres, rings as such, or applied to an inert support such as silicon, aluminum, aluminum silicate, ceramic oxides, alumina or alumina hydrates, zinc oxide. Furthermore, the support can also be a monolithic support made of ceramic, steel, glass, on which the aluminum catalyst is fixed. If an inert support is used, the catalyst should contain about 0.1 to 50% by weight of catalytically active aluminum. However, the aluminum catalyst is preferably used as such.
The optimal amount of catalyst, which is not decisive for the reaction itself, but only for the reaction rate, depends essentially on the volume flow of the reaction gas and thus on the reaction arrangement. It can easily be determined for each reaction arrangement by preliminary tests with different quantitative ratios. Experiments have shown that a weight ratio of chemical compound: aluminum of approximately 50: 1 to 1:10, preferably of 20: 1 to 1: 5, shows good results with regard to the reaction rate. Since the catalyst remains highly active over long periods of time, smaller amounts of catalyst can also be used, with a longer contact time being accepted under certain circumstances.

For the hydrolysis of the chemical compound, at least the theoretical amount of water must be used, which is necessary to cleave all CX bonds, taking into account possible additional substituents. In general, however, water is used in an excess of at least 10% of the stoichiometrically necessary amount, but usually in an even greater excess. In the case of melamine, for example, there are at least 6 moles per mole, in the case of melem use at least 12 moles of water. About 1.1 to 10 moles of water are preferably used per mole of chemical compound. The optimal amount of water can be determined by simple preliminary tests for each case.

The reaction temperatures are from 300 to 600 ° C, preferably from 350 to 500 ° C, particularly preferably from 380 to 450 ° C.

To carry out the process according to the invention, the chemical compounds or articles which contain the chemical compounds can, if appropriate, be comminuted, introduced together with the aluminum catalyst and water in a reaction apparatus and heated to the reaction temperature. However, the water can also only be introduced when the reaction temperature has been reached. However, it is also possible to add the catalyst with or without water and to add the chemical compounds without or with water, if desired, continuously. This procedure is advantageously carried out in a fluidized bed apparatus. As usual, water can be introduced into the reaction apparatus in liquid form, by moistening the chemical compounds, by water saturation of the carrier gas or by spraying or in gaseous form. Depending on its nature, the chemical compound can be added solid, as a melt or dissolved in a suitable solvent. However, the chemical compound can also be added in gaseous form if the sublimation temperature is in a suitable temperature range. For this purpose, the chemical compounds are preheated, whereupon the sublimation gases formed are optionally passed over the aluminum catalyst at reaction temperature using a carrier gas which is inert under the reaction conditions.
When the chemical compounds come into contact with the water vapor and the aluminum catalyst, the substituents are split off and rings or chains containing a heteroatom X are broken up and broken down.
Depending on the type of heteroatoms or CX bonds, different degradation products are formed. CX bonds from the group CF, C-Cl, C-Br and CJ are split, for example, into an alcohol which can be further broken down by dehydration and into a hydrogen halide. CX bonds from the group C-NH₂, C-NHR₁, C-NR₁R₂, C-NH-C, C-NR₁-C, C = NC are cleaved in CO₂ and NH₃ or NHR₁ or NR₁R₂, the amines by deamination can be further split.
Furthermore, additional degradation products, such as dehydrogenation products of possible side chain groups and Side chain rearrangement products such as hydrogen and acetonitrile occur. If a chemical compound has halogen substituents and CN bonds at the same time, ammonium halide, for example, ammonium chloride, which is obtained as a white powder in the condensation zone, can form.
Thus, when atrazine, a trianzine ring which is substituted by a chlorine atom, an ethylamine group and an iso-propylamine group, was degraded according to the invention, side chain groups such as ethylamine, deamination products of the side chain groups such as ethylene, isopropyl, dehydrogenation products of the side chain groups and side chain rearrangement products such as hydrogen were present in the reaction gases and acetonitrile. Ammonium chloride was also formed, which was found as a white powder in the condensation zone.

The resulting reaction gases are removed, if necessary with the aid of a carrier gas, and the ammonia and CO₂ contained therein are separated in the customary manner, for example in accordance with AT 360.447, and recycled.
Other gases, liquids, such as alcohols, or solids, which can occur as degradation products in the process according to the invention, are isolated as usual according to the prior art.
Helium, argon, nitrogen or air can be used as carrier gas.
The process can be carried out continuously or batchwise and is preferably carried out continuously.

In a preferred embodiment, the chemical compounds or articles containing such compounds are, if appropriate after mixing or melting, mixed with an aluminum catalyst and treated with steam at temperatures from 380 to 500 ° C. The reaction gases are removed with the help of helium as carrier gas and separated in the usual way, further degradation products are also separated and isolated in the usual way.

In a particularly preferred embodiment, aluminum oxide is placed in a fluidized bed reactor together with the chemical compounds and, by flowing in an inert carrier gas, a fluidized bed is built up, into which water vapor is introduced at temperatures of 300 to 600.degree. However, it is also possible to build up a fluidized bed in which there is only aluminum oxide, into which, preferably continuously, the chemical compound in solid form or in the form of sublimation gases and water vapor, if appropriate together with one of the Reaction conditions inert carrier gas, are introduced. The reaction gases are removed from the reactor as usual and separated as usual.

Chemical compounds which have one or more heteroatoms X are disposed of in an environmentally friendly manner in the manner described. The process is therefore an enrichment of technology.

Example 1:

40 ml (0.49 mol) CHCl₃ (ρ = 1.47) and 40 ml (2.22 mol) H₂O were dosed at 15 ml / h dosing speed over 160 min in an evaporator at 200 ° C. The evaporated feedstocks were then run with an N₂ stream preheated to 200 ° C (220 l / h) in an Al₂O₃ fluidized bed contact furnace at 370 ° C. The gas mixture obtained from the contact furnace was first passed through a water cooler, then through a cold trap cooled with liquid nitrogen and finally through 700 ml of a NaOH receiver. The content of conc. NaOH was precisely determined before and after the reaction and the consumption was converted to the HCl content.

The condensed gas mixture from the reflux condenser and the cold trap were combined and a phase separation was carried out. The HCl content of the aqueous phase was determined by titration with 1N NaOH solution.
With the HCl content of the NaOH template and the HCl content of the aqueous phase, a conversion of 30.6% was calculated.

Analogous to Example 1, further tests were carried out at the same temperature, the parameters and results are summarized in Table 1.

The following abbreviations have been used.
Input material: EZ
Molar ratio: EZ: H₂O
Total response time: RZ Table 1 E.g. EZ EZ: H₂O EZ / H₂O (ml) RZ (min) N₂ (l / h) %Sales 2nd CHCl₃ ρ = 1.47 0.61: 2.8 50/50 203 225 34.8 / cl 3rd 12-dichloroethane ρ = 1.25 0.63: 2.8 50/50 200 225 33.1 / cl 4th Benzyl chloride ρ = 1.10 0.395: 2.77 50/50 205 235 69.1 / cl 5 Butyl iodide ρ = 1.61 0.44: 2.8 50/50 200 235 53.1 / y 6 Butyl iodide ρ = 1.61 0.44: 2.8 50/50 215 230 57.1 / y 7 1-Br-undecane ρ = 1.05 0.22: 2.77 50/50 215 235 51.5 / Br 8th n-Br-undecane ρ = 1.05 0.205: 2.55 46/46 185 230 59.6 / Br 9 Chlorocyclohexane ρ = 1.00 0.396: 2.61 47/47 200 226 78.7 / cl 10th Chlorocyclohexane ρ = 1.00 0.42: 2.77 50/50 205 226 86.1 / cl 11 Di-Br-ethane ρ = 2.18 0.534: 2.55 46/46 188 226 42.0 / Br 12th Di-Br-ethane ρ = 2.18 0.39: 1.88 34/34 140 226 33.6 / Br 13 Butyl chloride ρ = 0.88 0.475: 2.77 50/50 210 240 63.7 / cl 14 Chlorobenzene ρ = 1.104 0.49: 2.77 50/50 220 235 * 20.0 / cl * Air was used instead of N₂

As a comparison experiment, an experiment with 47 ml (0.58 mol) of CHCl₃ was carried out without the use of water vapor analogously to Example 1, a conversion of only 6.48% being achieved.

Example 15:

100 g of melamine (0.8 mol) were placed in a fluidized bed reactor. A fluidized bed was built up with the aid of nitrogen and heated to 380.degree. The melamine sublimated. The sublimation gases were passed over a catalyst layer of aluminum oxide with 22 g of water (1.2 mol) at 320 ° C. in the course of 2 hours using a stream of nitrogen gas.
The composition of the reaction gases was determined by mass spectrometry, only ammonia, CO₂ and nitrogen being found.
The majority of the reaction gases were introduced into water, and no melamine was found in the solution.

Example 16:

Was carried out as in Example 15, but using 130 g of water (7.2 mol) and a reaction temperature of 380 ° C., whereby the same results as described in Example 1 were obtained.

Example 17

10 mg melamine-formaldehyde resin with a weight ratio of melamine: formaldehyde equal to 1: 1.7 were mixed with 100 mg Al₂O₃ and heated to 400 ° C in a water-saturated helium gas stream. The reaction gases were examined by mass spectrometry, whereby only ammonia CO₂ and water were found.

Example 18

In a heatable reaction tube, which was divided into two chambers with the aid of glass wool, 1 mg of melem were introduced in chamber 1 and 20 mg of aluminum oxide in chamber 2. The tube was heated to 400 ° C, passing a water-saturated helium gas stream. The examination of the reaction gases showed that only ammonia and CO₂ appeared as reaction products.

Example 19

50 mg of atrazine and 50 mg of aluminum oxide at a distance of 80 to 100 mm were introduced into a heatable reaction tube with a diameter of 4 mm. The tube was heated to 450 ° C. and charged with a stream of helium and water vapor (30 ml per minute, water vapor partial pressure = 32 mbar). The atrazine sublimed and the sublimation gases were passed into the catalyst zone with the aid of the gas stream. The hydrolysis was complete after one hour.
The reaction gas was analyzed by mass spectrometry. Ammonia, CO₂, ethylamine, ethylene, isopropylene and small amounts of hydrogen were found. In the colder zone of the reaction tube, 12 mg of a white powder was found, which was identified as ammonium chloride.

Example 20

was carried out as Example 19, but the reaction temperature was 500 ° C instead of 450 ° C. In the reaction gas, ammonia, CO₂, ethylene, isopropylene, acetonitrile and higher proportions of hydrogen were found than in Example 5. In the colder zone of the reaction tube, 12 mg of a white powder was found, which was identified as ammonium chloride.

Example 21

In a heatable reaction tube with a diameter of 4 mm, 100 mg Al₂O₃ were introduced. The tube was heated to 400 ° C and charged with a stream of helium saturated with water and diethylamine (30 ml / min).
After the hydrolysis had ended, the reaction gas was analyzed by mass spectrometry, and ammonia, acetonitrile and traces of HCN were found.

Example 22

Was carried out analogously to Example 21, the reaction temperature was 480 ° C. Ammonia, hydrogen, ethylene and traces of HCN were found in the reaction gas.

Example 23

As a comparative experiment, diethylamine was decomposed without water analogously to Examples 21 and 22, with no reaction occurring at 400 ° C. and the proportions of acetonitrile, HCN and hydrogen being very large at 480 ° C. and only a small proportion of ammonia being found.

Example 24

Analogously to Example 21, dimethylamine was hydrolyzed. After hydrolysis at a reaction temperature of 400 ° C, methylamine, trimethylamine, CO and traces of HCN and acetonitrile were found in the reaction gas. The turnover was 14%. At a reaction temperature of 460 ° C, ammonia, methylamine, trimethylamine, CO and traces of ethylenediamine and acetonitrile were found in the reaction gas after hydrolysis. The turnover was 42%.
At a reaction temperature of 520 ° C, the proportion of ammonia in the reaction gas rose sharply, the conversion was 84%.

Claims (10)

Process for the environmentally friendly degradation of chemical compounds which have one or more heteroatoms X, where XF, Cl, Br, J, N, O or S, by cleaving the CX carbon-heteroatom bonds, characterized in that the chemical compounds or objects, in which the chemical compounds are contained, are treated with steam in the presence of an aluminum catalyst at 300 - 600 ° C. A method according to claim 1, characterized in that the chemical compounds one or more carbon heteroatom bonds from the group CF, C-Cl, C-Br, CJ, C-NH₂, C-NHR₁, C-NR₁R₂, C-NH-C , C-NR₁-C, C = NC, C-SH, CSC, CSSC, C = S, COC, C-OR₃, COOR₃ or C = O, where R₁ and R₂ may be the same or different and represent an alkyl radical and R₃ can be H or an alkyl radical. A method according to claim 1, characterized in that the chemical compounds are aliphatic hydrocarbons which with one or more radicals from the group -F, -Cl, -Br, -J, -NH₂, -NHR₁, -NR₁R₂, -OR₃, - OOR₃, = O or -SH are substituted, or that they are hydrocarbons, optionally in combination with the radicals mentioned, in the hydrocarbon chain CX bonds from the group C-NH-C, C-NR₁-C, C = NC, CSC, CSSC, COC included. A method according to claim 1, characterized in that the chemical compounds are aromatic hydrocarbons which with one or more radicals from the group -F, -Cl, -Br, -J, -NH₂, -NHR₁, -NR₁R₂, -OR₃ or - SH are substituted. A method according to claim 1, characterized in that the chemical compounds are heterocycles which have one or more CX bonds from the group C = NC, CSC, C-NH-C, C-NR₁-C, COC in the cycle and optionally with one or more radicals from the group -F, -Cl, -Br, -J, -NH₂, -OR₃, -NHR₁, -NR₁R₂ or -SH are substituted. A method according to claim 1, characterized in that the chemical compounds are triazine compounds. A method according to claim 6, characterized in that the triazine compounds are melamine or compounds derived therefrom. A method according to claim 1, characterized in that the triazine compounds are melamine-formaldehyde resins. Process according to Claim 1, characterized in that aluminum oxide is used as the catalyst. Process according to Claim 1, characterized in that the aluminum catalyst is placed in a fluidized bed apparatus and a fluidized bed is built up with the aid of a carrier gas which is inert under the reaction conditions, into which water vapor and the chemical compound are introduced, whereupon the reaction gases and other decomposition products are produced in the usual manner and Be dissipated and separated.