EP0257260B2 - Process for the hydrogenation treatment of mineral oils contaminated by chlorobiphenyls - Google Patents

Abstract

Halogen-containing oils and hydrocarbons are treated on an industrial scale whereby the mineral base oils comprising the main component of the oils hydrocarbons can be reused. The oils are subjected to a high pressure hydrogenation under typical conditions of liquid phase hydrogenation or of combined liquid-phase and gas-phase hydrogenation, at hydrogen pressures of 20-325 bar, temperatures of 250 DEG -500 DEG C., and gas/oil ratios of 100-300 m3 per metric ton at STP.

Description

The invention relates to a process for the hydrogenating treatment of mineral oils contaminated with multiply chlorinated biphenyls (PCBs), and to distillation residues of such mineral oils.

In the present context, the multiply chlorinated biphenyls, often also referred to as PCBs, must be examined with regard to the possibilities for their safe disposal. These compounds, for which meanwhile MAK values of 0.5 to 1.0 mg / m ^{3 have been} set depending on the chlorine content and for the manufacture and further use of which extensive official restrictions have been imposed, have been adopted because of their thermal and chemical stability and their dielectric properties used as insulating and cooling liquids in the construction of high-voltage capacitors, transformers and rectifiers, as plasticizers for coating resins and plastics, sealing liquids, impregnating agents for seals, hydraulic oils and heat transfer agents (see Römpps Chemielexikon, 8th edition, page 715).

Because of their low degradability and because of the need to safely remove the chlorobiphenyls and related other chlorinated hydrocarbons, there is a need for a suitable industrially feasible process.

In particular, PCB-containing liquids or PCB-containing liquids mixed with oil residues after their use are to be regarded as hazardous waste, which must be recorded, properly handled and disposed of or safely disposed of.

For the removal of chlorobiphenyls are thermal combustion processes, adsorption processes or processes for solvent extraction, processes for catalytic treatment with hydrogen in the presence of organic solvents, chlorolysis processes under treatment with chlorine in the vapor phase. Process for dehalogenation using sodium or sodium-organic substances, microwave plasma process, ozonization process, process for reaction with a reagent prepared in the presence of oxygen from sodium metal and polyethylene glycols. Processes for the cleavage of the PCB molecule in biphenyl and chlorine as well as processes for the direct oxidation of chlorobiphenyls with air or oxygen in the aqueous phase in the presence of acids at elevated temperatures have been developed (cf. DG Ackerman et al "Distruction and Disposal of PCBs by Thermal and Non-Thermal Methods ", Noyes Data Corporation, Park Ridge, New Jersey, USA, 1983).

None of the listed methods can be regarded as suitable for all applications and can be used without restrictions. The thermal incineration processes therefore require extensive precautions to control and possibly treat the resulting exhaust gases and, if necessary, also to treat and landfill any solid residues that may occur. Still, thermal combustion processes are the most developed and widely used. The rest of the processes are only partially developed on a laboratory scale or on a semi-industrial scale.

As an example, see the studies by W. L. Kranich et al, "Process for Hydrodechlorination of Polychlorinated Hydrocarbons", 1977. Presented at the American Chemical Society Div. of Pesticides Chemistry, 194th National Meeting, Chicago, Illinois. Hydrogen pressures of 30 to 50 bar, nickel on diatomaceous earth or palladium on a carbon support as catalyst and temperatures in the range of approximately 100 to 120 ° C. have been mentioned for this process. NaOH in ethanol is used as solvent. Such processes require extensive solvent refluxes and solvent workups. For this reason, large-scale implementation has not yet become known.

EP-0 178 001 A describes a further process for working up by refining and / or eliminating halogen, nitrogen and / or sulfur-containing compounds which are difficult to biodegrade in hydrocarbon feed streams. The feed stream is first passed together with hydrogen gas over a pre-column filled with an absorbent and then over a fixed bed contact preferably made of nickel or cobalt plus molybdenum on a support.

The object of the invention is to provide a further process which can be used on an industrial scale for working up PCB-containing waste oils. This process enables multi-chlorinated biphenyls to be broken down to values of up to 1 ppm and below. The mineral base oils contained as the main component can be reused without being lost, for example, by incineration or other mining processes.

According to the invention, this object is achieved in that the above-mentioned feed hydrogen pressurization under the typical conditions of a sump phase hydrogenation or a combined sump / gas phase hydrogenation at hydrogen pressures of 20 to 325 bar. Temperatures from 250 to 500 ° C and gas-oil ratios of 100 to 3000 Nm ³ t are subjected to, wherein 0.5 to 5 wt .-% of a hollow surface-containing suspended solid are used in the bottom phase hydrogenation. This method is particularly suitable for waste oils containing PCB or with drilling oils, cutting oils, transformer oils, hydraulic oils and the like. Work up mixed used oils in a sump or combined sump / gas phase hydrogenation.

The feed oils are preferably used as such or in a mixture with residual oils, heavy oils or finely ground coal in the bottom phase hydrogenation, with the use of coal providing a step for preparing the mixture of finely ground coal and the oil components. It is advantageous to add 30 to 95% by weight, preferably 50 to 95% by weight of residual oil or heavy oil to the bottoms hydrogenation.

Depending on the desired degree of conversion and the tendency of the oils used to form coke, an amount of between 0.5 and 5% by weight of a finely divided carbon-containing surface-rich suspended material (additive), which can optionally be impregnated with heavy metal salts, in particular iron (II) sulfate , added as a single-use catalyst in the mixture preparation. The feed mixture then goes through a compression stage and is charged with hydrogen-containing cycle gas and fresh hydrogen. After passing through heat exchangers, in which heat is exchanged with product streams to heat the feed mixture, the mixture passes through a so-called preheater and enters the bottom phase reactor from below. They are generally vertical tubular reactors without internals. The hydrogenation reaction takes place at elevated pressure, at hydrogen pressures between 20 and 325 bar, and at elevated temperature, between 250 and 500 ° C and at gas-oil ratios of 100 to 3,000 Nm ³ / t, with the gas is the hydrogen-containing hydrogenation gas. The desired degree of conversion and the required limit for the degradation of the chlorobiphenyls, for example, determine the flow rate of the feed products. Typical values are 0.4 to 1.0 t / m ³ h. In the case of the joint use of oil components and coal or the presence of an additive or other residues, e.g. B. from drilling chips, the reaction products are expediently passed over a hot separator operated at reaction pressure and at a temperature which is preferably 20 to 50 ° C. lower than the reaction temperature. Here, the uncondensed hydrocarbons are removed overhead and the bottom products containing residues at the bottom. Distillable heavy oil components can be separated in a downstream stripper and can be further processed by combining with the top product of the hot separator. The residue behind the stripper can be used to generate hydrogen or energy.

A gas phase hydrogenation for further processing of the uncondensed reaction products, which have been drawn off at the top of the hot separator, can be directly coupled to the previously described bottom phase hydrogenation without reheating or depressurization. The further hydrogenation, stabilization and removal in the gas phase hydrogenation, for example of heteroatoms such as sulfur or nitrogen, to obtain feedstocks with reformer feed specification or middle distillate takes place on fixed bed catalysts using commercially available catalysts. After passing through the gas phase hydrogenation, the product streams are condensed and cooled by intensive heat exchange and separated into a liquid phase and a gas phase in a high-pressure cold separator. After the liquid phase has been let down, it is usually fed to a stabilizing column in order to remove the C ₄ products and to obtain a stabilized syncrude. The gaseous products pass through a gas scrubber to remove, among other things, H ₂ S and NH ₃ . Part of the purified hydrogen-rich gas is recycled as cycle gas into the bottom phase hydrogenation. The separation is then carried out in an atmospheric distillation, depending on the determination of the boiling cuts in naphtha, middle distillate and vacuum gas oil. If coal and feed oil are used together, the ratio is preferably 1:20 to 1: 1, in particular 1: 5 to 4: 5.

However, a cold separator stage with subsequent expansion and separation of the liquid products into an aqueous phase and a mineral oil-containing phase and atmospheric distillation of the oil-containing phase can also directly follow the bottom phase hydrogenation.

In particular, the suspended lignite coke from shaft and hearth furnaces, lignite coarse, soot from the gasification of heavy oil, hard coal are additives. Lignite or hydrogenation residues and activated coke, petroleum coke and dusts from the Winkler gasification and high-temperature Winkler gasification of coal, ie materials with a large inner surface and with a pore structure for demetallization and deasphalting and for taking up coke precursors when carrying out the phase-phase hydrogenation, are suitable . Red masses, Bavarian masses, iron oxides and electrostatic filter dust and cyclone dust from metal / ore processing can also be used with advantage. The proportion of these additives is preferably 0.5 to 5% by weight and, if carbon-containing additives are used, these can be mixed with salts of metals from subgroups 1 to 8 and 4. Main group of the periodic system of the elements, preferably iron, cobalt, nickel, vanadium, molybdenum, for example Fe (II) sulfate.

It is preferred to add 0.5 to 5, but also 0.01 to 5% by weight of a compound which forms salts with hydrogen halide, in particular hydrogen chloride, by neutralization or which releases hydroxide ions in aqueous solution, to the bottom phase hydrogenation feedstocks or these compounds together with Water in the effluent from the bottom phase reactor, e.g. B. inject the feed lines of the cold separator. For this purpose, preferably 0.5 to 5, but also 0.01 to 5% by weight of an alkali metal hydroxide, alkali metal carbonate, alkali metal acetate, alkali metal alcoholate, alkali metal sulfide, corresponding ammonium compounds, insofar as they exist in bulk or in aqueous solution, or mixtures of the abovementioned compounds .

When ammonium compounds or ammonia-water mixtures are added, due to the tendency of ammonium chloride to sublimate, suitable precautionary measures must be taken to avoid clogging, for example of the product lines of the cold separator. Alkaline earth compounds can also be used to neutralize the hydrogen halide and form water-soluble salts. The sodium compounds, for example sodium sulfide, are preferred.

example 1

A used motor oil with 1 100 ppm polychlorobiphenyl (PCB) is contacted in a continuous hydrogenation system at 430 ° C and a pressure of 280 bar with 1500 Nm ³ t hydrogen. Before the reaction, 1% by weight of Fe-containing (Fe ₂ O ₃ ) dust from iron ore processing and 0.2% by weight of Na ₂ S are added to the oil. After a dwell time of 1.5 hours in the hydrogenation reactor, the PCBs are broken down below the analytical detection limit of 1 ppm, while the waste oil undergoes a shift in the boiling point according to the following tables. Waste oil Raffinate IBP (start of boiling) ° C 256 98 <100 ° C% by weight - - 100 - 300 ° C% by weight 2nd 24th 300 - 500 ° C% by weight 76 70 > 500 ° C% by weight 22 5 FBP (end of boiling point) ° C 570 529

The lubricating oil fraction in the raffinate (Frakt. 300 -500 ° C) has a viscosity index of 120, it is therefore a base oil component for the production of a quality motor oil.

example 2nd

15% by weight of a used industrial oil with a chlorine content of 10,000 ppm is added to a vacuum residue from Bachaquero crude oil with a residue content> 500 ° C. of 6% by weight. This mixture is hydrogenated after the addition of 1.8% activated coke and 0.2% Na ₂ S at 450 ° C. and 220 bar in the bottom phase reactor. The vacuum residue is converted to 91% into low-boiling components and gaseous substances, whereby the liquid products generated are PCB-free, ie below the gas chromatographic detection limit. The table shows the distribution of use and products. commitment Products 15% by weight industrial oil <500 ° C 5% by weight H ₂ S, NH ₃ , H ₂ O 5.1% by weight vacuum gas oil 350 - 500 ° C, atm. print 8% by weight of C ₁ -C ₄ 79.9% by weight residue> 500 ° C 21% by weight C ₅ - 200 ° C petrol 2% by weight of brown coal coke + Na ₂ S 34% by weight 200-350 ° C middle distillate 3% by weight of hydrogen 28% by weight 350-500 ° C 9% by weight residue> 500 ° C (including solids)

With regard to the practically complete degradation of PCBs, the proposed process is therefore much more economical than the thermal combustion process for waste oils containing PCBs, which is also carried out on an industrial scale, and it also avoids the problems associated with combustion of the formation of non-harmless secondary products of the combustion of chlorinated hydrocarbons or Oils containing chlorobiphenyls.

Claims (10)

1. Process for the hydrogenating treatment of mineral oils contaminated with polychlorinated biphenyls (PCBs) and of distillation residues of such mineral oils for the purpose of degradation of the polychlorinated biphenyls (PCBs) to values of down to 1 ppm and below, characterized in that the abovementioned stock substances are subjected to a pressure hydrogenation under the typical conditions of a semi-solid-phase hydrogenation or of a combined semi-solid-phase/gas-phase hydrogenation at hydrogen pressures of 20 to 325 bars, temperatures from 250 to 500°C and gas/oil ratios of 100 to 3000 Nm³/t, 0.5 to 5% by weight of a carbon-containing, large-surface-area suspended solid being used in the semi-solid-phase hydrogenation.
2. Process according to Claim 1, characterized in that the semi-solid-phase hydrogenation is carried out in a mixture containing residue oil, heavy oil or finely ground coal.
3. Process according to Claim 2, characterized in that 30 to 95% by weight, preferably 50 to 95% by weight, of residue oil or heavy oil are added.
4. Process according to Claim 2, characterized in that coal and stock oil are used in a ratio by weight of 1:20 to 1:1, preferably 1:5 to 4:5.
5. Process according to Claim 1, characterized in that lignite cokes from shaft and open-hearth furnaces, soots from the gasification of heavy oil, coal, hydrogenation residues, lignite and the active cokes produced therefrom, petrocoke, dusts from the Winkler gasification of coal are used.
6. Process according to Claim 5, characterized in that the carbon-containing additives used are impregnated with metal salts of groups IB to VIII and of group IV of the periodic system of elements, preferably iron, cobalt, nickel, vanadium, molybdenum.
7. Process according to Claim 1, characterized in that 0.5 to 5% by weight of red sludges, iron oxides, electrostatic filter dusts and cyclone dusts from metal/ore processing are used.
8. Process according to Claim 1, characterized in that 0.01 to 5% by weight of a compound which forms salts with hydrogen halide by neutralization or splits off hydroxide ions in aqueous solution are added to the stock products.
9. Process according to Claim 8, characterized in that 0.01 to 5% by weight of an alkali-metal hydroxide, alkali-metal carbonate, alkali-metal acetate, alkali-metal alcoholate, alkali-metal sulphide, corresponding ammonium compounds, provided they exist in substance or in aqueous solution, or of mixtures of the abovementioned compounds are added.
10. Process according to Claim 8 or 9, characterized in that added compound to be added is sprayed together with water into the discharge flow of the semi-solid-phase reactor.