EP0250748A1 - Process for the dehalogenation of hydrocarbon oils - Google Patents

Abstract

Hydrocarbon oils contaminated with organic halogen compounds are dehalogenated at 120 to 400 ° C. by treatment with alkali or alkaline earth metal alcoholates, which are soluble in these oils under the reaction conditions.

Description

The invention relates to a process for the dehalogenation of hydrocarbon oils. These can be used lubricating oils, for example, which can be used again in a resource-saving and environmentally friendly manner for the production of secondary raffinates, or also aromatic heat transfer oils, which in this way remove the corrosiveness emanating from organochlorine compounds.

Lubricating oils accumulate metal abrasion, degradation and oxidation products of their components and fuel components during their use. Nonetheless, used lubricating oils are not considered waste products, since they can be processed through various operations, such as filtration, distillation, refining with concentrated sulfuric acid or oleum and treatment with bleaching earth, to the extent that full lubricants are formed after additional additives. Although the measures mentioned return a perfect base oil in terms of lubrication technology, they are unable to remove some impurities which are considered to be very harmful from an environmental toxicological point of view. These contaminants include some polychlorinated aromatics, some of which have been mixed with the used lubricating oils through negligence, but sometimes also deliberately or through technical breakdowns. Particularly noteworthy are the polychlorinated biphenyls (PCB), which are widely used because of their non-flammability as hydraulic oils in mining, but also as insulating oils and dielectrics for transformers and capacitors. Not only because of their accumulation in food chains analogous to the DDT, but also because of the possibility that far more dangerous substances - namely polychlorinated dibenzodioxins or dibenzofurans - can be generated at combustion temperatures below 1000 ° C, a problem that has been considered with concern for years The fear that such conditions may occasionally also exist in internal combustion engines ten, leads to the conclusion that PCB-contaminated waste oils can only be used for high-temperature combustion instead of secondary use if it is not possible to dechlorinate them with reasonable effort. It is therefore an urgent task, for reasons of environmental protection and the saving of raw materials, to develop processes which make waste oils economically usable for reuse.

An obvious way to remove halogen-containing compounds is to heat the oil with dispersed alkali metals. This route is followed, for example, in GB-PSS 2 063 908 and 2 081 298 and US Pat. No. 4,465,590. Although it gives satisfactory results, it requires large excesses of metal because of the reaction that only takes place at the metal / oil interface, the later elimination of which also poses safety problems.
Another method, described in US Pat. Nos. 4,284,516, 4,326,090 and 4,447,667, uses naphthalene sodium as a dechlorinating agent in homogeneous solution, but this can only be achieved by using an additional solvent. Tetrahydrofuran is primarily used as an additional solvent. A rapid reaction takes place even at low temperatures, but the high solvent expenditure makes the process unsuitable for economical execution on an industrial scale. A high excess of dechlorinating agents is also required here. In addition, the auxiliary naphthalene as an aromatic hydrocarbon is itself an environmental risk.

Processes for hydrogenating dechlorination are also known. They require high investments because of the necessary pressure equipment. Therefore, they only pay off with larger capacities.

Processes for dechlorinating organochlorine compounds with chemical reducing agents have also been described. According to WH Dennis, Jr. et al., Bull. Environ, Contam. Toxicol. 22 (6), 750-753 (1979) with nickel chloride and sodium boranate in isopropanol, according to US Pat. No. 4,400,566 with nickel chloride, a triarylphosphine and zinc dust in dimethylformamide or according to JP PS 74-61143 with Dechlorinate hydrazine hydrate on activated carbon in the presence of a palladium catalyst. The very nature of the auxiliary reagents used is prohibitive for the large-scale use of these methods, since new disposal problems for the residues are raised. Apart from that, the auxiliary reagents are by no means cheap.

Also in the processes in which a mixture of alkali hydroxide and polyethylene glycol in the absence (US Pat. No. 4,351,718) or in the presence of oxidizing agents (DE-OS 30 33 170, US Pat. No. 4,400,552 and 4,337,368 and EP-PS 0 118 858) are reacted with the contaminated oil, large amounts of reagents are consumed.

In EP-PS 0 021 294 the dechlorination of toxic organic aromatic chlorine compounds is described, mainly production residues from the production of 2.4.5-trichlorophenol being treated.

The products are used together with alkali metal alcoholates of monohydric alcohols with 1 to 5 C atoms or of polyoxyalkylene glycols with 4 to 20 C atoms or of polyols with 2 to 5 C atoms and 2 to 3 hydroxyl groups or of monoalkyl ethers from these latter polyols and Alcohols with 1 to 4 carbon atoms in the presence of 0.5 to 1 equivalent of the free alcohol, based on organically bound halogen, heated. Alternatively, mixtures of these alcohols with alkali metal hydroxides or carbonates can be used. In general, dechlorination is carried out with sodium glycolate / ethylene glycol. If sodium methylate / methanol is used instead, high pressures have to be accepted.

The process is used for the total destruction of such production residues and, due to the disclosed reaction conditions, is not suitable for refining large quantities of only slightly contaminated oils and for further use of certain oils. It also exhibits heterogeneous reactions and is therefore difficult to integrate into continuous production processes.

The object of the present invention is to provide a process for the dehalogenation of hydrocarbon oils contaminated with organic halogen compounds, which
- runs quickly and completely,
- Requires small amounts of inexpensive auxiliary reagents and
- does not pose any safety and environmental problems when disposing of the residues.

The object is achieved in that the hydrocarbon oils contaminated with organic halogen compounds are treated at 120 to 400 ° C. with alkali or alkaline earth metal alcoholates with 6 to 25 carbon atoms. This creates alkali or alkaline earth halides, which precipitate out and can be removed by filtration, washing out or as part of a distillation residue. Excess reagent can be converted into insoluble inorganic salts by the slight addition of acids or acidic salts or can be filtered off bound to bleaching earth. They are not a new threat to the environment.

Hydrocarbon oils such as heat transfer oils, insulating oils, hydraulic oils, heavy oils, lubricating oils, neutral oils, waste oil fractions, paraffin oils or organic hydrocarbon intermediates can be used for the process according to the invention.

It is important in this process that the alcoholate used is soluble in the hydrocarbon oils under the reaction conditions. The conditions of solubility are fulfilled by all alcoholates with straight-chain, branched and cyclic alkyl radicals with at least 6 carbon atoms. An upper limit of 25 carbon atoms is determined less by the effectiveness than by the availability of the associated alcohols. However, the proportion of the active alcoholate group is small in the case of large alkyl residues. Alcoholates with alkyl radicals with 8 to 20 C atoms are technically interesting, with a particularly favorable compromise for alkyl groups with 8 to 14 C atoms, where good solubility and availability are combined with a still favorable proportion of active groups.

The alcohols suitable for the preparation of the dehalogenating agents according to the invention include, for example, hexanol-1, -2 and -3, heptanol-1, -2, -3 and -4, octanol-1, -3 and -4, nonanol-1, 2, -3, -4 and -5, decanol-1, -2, -3, -4 and -5, undecanol-1, -2, -3, -4, -5 and -6, dodecanol-1, -2, -3, -4, -5 and -6, tridecanol-1, -2, -3, -4, -5, -6 and -7, tetradecanol-1, -2, -3, -4, -5, -6 and -7 (myristyl alcohol), pentadecanol-1, -2, -3, -4, -5, -6, -7 and -8, heptadecanol-1, -2, -3, -4, -5, -6, -7, -8 and -9, octadecanol-1 (stearyl alcohol), -2, -3, -4, -5, -6, -7, -8 and -9, nonadecanol-1, -2, -3, -4, -5, -6, -7, -8, -9 and -10 and eicosanol-1, -2, -3, -4, -5, -6, -7, - 8, -9 and -10, their higher homologues and their branched isomers, cyclohexanol, cycloheptanol, cyclooctanol, cyclononanol, cyclodecanol, cycloundecanol, cyclododecanol, cyclotridecanol, cyclotetradecanol, cyclopentadecanol, cyclohexadecanol, cycloheptadecanol, cyclooctadecanol and cyclooctadecanol Cycloeicosanol and its alkylated and arylated derivatives, hydrogenated naphthols, benzyl alcohol, alpha and beta-phenylethanol, undecen- (1) -ol-11, oleyl alcohol, cinnamon alcohol, benzhydrol, 2-hydroxymethyl-bicyclo [2.2.1] -heptane and others .

Numerous representatives of these suitable alcohols are accessible on a petrochemical or native basis by reactions such as hydrogenation of esters, hydroformylation or hydration of olefins, Guerbet reaction of lower alcohols, oxidation and subsequent hydrolysis of higher aluminum alkyls and by other reactions on an industrial scale. Particularly preferred are the branched alcohols with 8 to 14 carbon atoms that are usually used in the production of plasticizers for PVC, such as 2-ethylhexanol-1, "isononanol", "isodecanol", "isotridecanol" (hydroformylation products of dimerbutene, trimer propene, trimerbutene or Tetramer propene) because their alcoholates have particularly good solubility in hydrocarbon oils.

As the dehalogenating agent, the alcoholates formed by the above alcohols with alkali and / or alkaline earth metals can be used, among the alkali alcoholates preferably those of sodium and potassium, among the alkaline earth alcoholates that of magnesium and calcium. Alkali alcoholates are particularly preferably used.

The alcoholates can be prepared in all known ways, i. H. by reacting metal or metal hydride with alcohol with the formation of hydrogen, by reacting lower alcoholate with higher alcohol while distilling off the lower alcohol, and from metal hydroxide and alcohol with azeotropic removal of the water in equilibrium. The representation can also take place in situ in the presence of the substrate to be dehalogenated. It is not necessary to use the alcoholate in the presence of excess alcohol, but a small excess does not interfere.

The stoichiometrically required amount is calculated from the chlorine content, taking into account the moisture content and the acid and ester groups that also react with alcoholate. The amount of reagent used is 0.5 to 5 times the stoichiometrically required amount. Although higher surpluses do not hurt either, they are avoided for procedural and cost reasons. Amounts of reagent which correspond to 1.5 to 5 times the stoichiometric amount are preferably used. Small excesses are usually sufficient if you work in the upper part of the temperature range.

Temperatures of 120 to 400 ° C are suitable for dehalogenation. The response time can be up to 10 hours at the lower limit and a few seconds at the upper limit. Temperatures of 180 to 380 ° C are preferred, a temperature range of 220 to 350 ° C is particularly advantageous.

Temperatures in the ranges mentioned occur in the course of conventional waste oil processing anyway in distillation stages, so that additional reactors are unnecessary if they are skillfully inserted into the process. On the other hand, individual smaller batches can also be batch-dehalogenated in a conventional reaction kettle.

The process can therefore be used both for small discontinuous batches and can be integrated into fully continuous processes.

Since hydrocarbon-soluble alcoholates are used, the dehalogenation can be carried out in a homogeneous phase without solvents. This enables minimal chemical consumption and short reaction times. In addition, the residues arising during disposal do not pose any safety and environmental problems.

The invention is illustrated by the following examples:

example 1

Dechlorination reagent: 18 g of sodium and 130 g of 2-ethylhexanol-1 are stirred under nitrogen for 6 hours at 150 ° C. and for one hour at 200 ° C., a clear liquid being formed:

148 g of 80% Na ethyl hexoxide

Hydrocarbon oil: A recycled waste oil is used that is not readditivated.

The theoretically required stoichiometric amount is then:

3.1 g Na ethyl hexoxide / kg oil

Dechlorination: 500 g of reprocessed waste oil are mixed with 7.9 g of 80% Na ethyl hexoxide and then stirred at 350 ° C for 30 minutes. A sample is taken in which, after filtration of precipitated NaCl, organically bound chlorine is determined by Wickbold combustion. The analysis results are shown in Table 2.

The waste oil is cooled to room temperature. Excess Na ethyl hexoxide is concentrated by. Sulfuric acid destroyed. After filtration of the inorganic salts, the waste oil is distilled under vacuum.

Examples 2 to 10

The procedure is as in Example 1. The hydrocarbon oils used are summarized in Table 1.

The results of the dechlorination tests are shown in Table 2.

Example 11 (Dechlorination of a Crude Dibenzyltoluene)

500 g of a dibenzyltoluene isomer mixture to be used as heat transfer oil contain 1,200 ppm chlorine.

The theoretically required stoichiometric amount of alcoholate is:

5.1 g Na ethyl hexoxide / kg oil

The chlorine content is reduced to 4 ppm by two distillation at normal pressure and 360 ° C above 5 times the stoichiometric amount of Na ethyl hexoxide.
93% by weight of the crude product used is obtained as the distillate.

Claims (9)

1. Process for the dehalogenation of hydrocarbon oils,
characterized,
that the hydrocarbon oils are treated in a homogeneous phase with alkali or alkaline earth metal alcoholates, the alkyl groups of which have 6 to 25 carbon atoms, at 120 to 400 ° C. and the alkali metal or alkaline earth metal halides formed are separated off after the reaction. 2. The method according to claim 1,
characterized,
that one uses alcoholates with alkyl groups with 8 to 20 carbon atoms. 3. The method according to claims 1 and 2,
characterized,
that alcoholates of sodium and potassium are used. 4. The method according to claims 1 to 3,
characterized,
that one uses sodium and potassium alcoholates with 8 to 14 carbon atoms. 5. The method according to claims 1 to 4,
characterized,
that the dehalogenation is carried out at 180 to 380 ° C. 6. The method according to claim 5,
characterized,
that the dehalogenation temperature is 220 to 350 ° C. 7. The method according to claims 1 to 6,
characterized,
that one uses 0.5 to 5 times the theoretically required amount of alcoholate. 8. The method according to claim 7,
characterized,
that you use 1.5 to 5 times the theoretically required amount of alcoholate. 9. The method according to claims 1 to 8,
characterized,
that is dehalogenated with the sodium alcoholate of 2-ethylhexanol-1.