EP0091047B1 - Fuel for a carburettor engine - Google Patents

Description

The invention relates to a method for producing a low-benzene, environmentally friendly gasoline from light coal oil. The conversion of coal to gasoline (gasoline) is preferably done in two stages. In the first stage, the bottom phase, the coal is converted into an intermediate product (medium oil and crude gasoline) in the presence of finely divided catalysts using hydrogen under suitable pressure and temperature, which is then converted into gasoline fuel in subsequent stages using further catalysts. Carburetor fuels obtained in this way are highly aromatic because of the molecular structure of the coal from condensed aromatics. Depending on the process conditions in the reformer, the benzene content in particular is between 10 and 20% by weight. This high benzene content is undesirable because of the toxic properties of benzene. In some countries, the benzene content in carburetor fuels is or is being striven for. For example, the benzene content in gasoline in the Federal Republic of Germany should be limited to 5 percent by weight.

Measures to lower the benzene content boil down to the fact that the concentration of benzene is reduced by blending with low-gasoline gasoline. This presupposes that low-gasoline gasoline, mostly of mineral oil origin, is available, which will not be the case with a self-sufficient coal liquefaction plant.

The invention has for its object to produce a low-benzol gasifier fuel from light coal oil, which is independent of the availability of low-benzol admixture components.

According to the invention this is achieved in that a core fraction of the boiling point 145-185 ° C., preferably via a packed column, is distilled off from the crude light coal oil. The fraction contains the majority of the phenol contained in the coal oil. The phenol can be separated from this core fraction and extracted by extraction with aqueous sodium hydroxide solution or sodium phenolate solution, preferably in a three-stage mixer-settler extractor. The remaining phenol-free raffinate of the core fraction is mixed with the portion of light coal oil, boiling up to 145 ° C, and by refining z. B. pressure 60 bar, temperature 410 ° C load 1.5 kg oil / kg cat. H) prepared for reformer application specification. Reforming (e.g. pressure 15 bar, temperature 480 ° C, load 1.5 kg oil / kg cat. H) results in a low-gasoline gasoline fuel with a high octane number.

In the process according to the invention, a valuable chemical raw material (phenol) is advantageously obtained at the same time, which is used on a large scale in the plastics industry.

As a result of the procedure described, the benzene content of the reformate is reduced to approximately 5% by weight and the process stages of refining and reformer are relieved in terms of quantity. In addition, since the phenol is not converted into worthless water and benzene by the hydrogenation reactions or, depending on the degree of hydrogenation, into cyclohexane, valuable hydrogen is saved in this stage.

The block diagram according to FIG. 1 shows the procedure of the method according to the invention.

Examples 1 to 3 give experimental data on how the benzene content is reduced in the process according to the invention, the quantity of product flow in the refining and in the reformer is relieved and how the hydrogen consumption is reduced for the hydrogenating removal of the phenols while simultaneously hydrogenating the benzene to cyclohexane.

example 1

According to the flow diagram shown in FIG. 2, 45 parts of a core fraction in the boiling range 145-185 ° C., which contains the majority of the phenol present in the light coal oil, are distilled off from 100 parts of crude light coal oil by refractionation. This core fraction is de-phenolized by 3-stage extraction with 69 parts of 12% aqueous NaOH in a mixer-settler extractor and the fraction freed from phenol is then mixed again with the light coal oil (boiling point - 145 ° C). The phenol-free light coal oil is processed by refining and reforming on gasoline. The procedure described lowers the benzene content of the gasoline fuel to 2.6% by weight. If the light coal oil is not de-phenolic before processing in the refiner and reformer, the benzene content in the gasoline is 17.1% by weight.

Example 2

100 parts of light coal oil, which contain 16% by weight of phenol, are broken down into two fractions - boiling from the beginning of boiling to 145 ° C, 55 parts or 45 parts from 145 to 185 ° C. In the core fraction 145 to 185 ° C, the phenol is enriched to 35% by weight. After the raffinate from the extraction has been combined with the fraction at the beginning of boiling at 145 ° C., the feed oil for the refiner / reformer still contains 0.8% by weight of phenol. Due to the extraction of the phenol, only 84 parts of the original 100 parts of light coal oil have to be processed in the refiner / reformer, ie this system is relieved in terms of quantity. The hydrogen consumption in refining is reduced by 130 I / kg feed oil compared to processing of the crude, non-de-phenolic light coal oil, since the phenol has been removed and thus the hydrogen requirement for the hydrogenating phenol removal is eliminated.

Example 3

From 100 parts of crude light coal oil with 16 parts of phenol, 45 parts of a phenol-rich fraction at 145-185 ° C. are boiled by distillation. The phenol content in this fraction is enriched to 35% by weight by distillation. Phenol is extracted from this core fraction by extraction with 12% sodium hydroxide solution and the previously extracted phenols, that is 15 parts of phenol, are released by acidification with stoichiometric amounts of dilute sulfuric acid. Based on light coal oil, this is 94% by weight of the phenol present in the raw light coal oil.

According to FIG. 3, a 3-stage mixer-settling extraction apparatus is used to remove phenols from light coal oil using aqueous sodium hydroxide solution.

In stage I, fresh sodium hydroxide solution is introduced into the mixer zone by means of a metering pump and pre-extracted light coal oil via a forced flow in stage 11.

By intensive stirring, the mass transfer between the two, almost insoluble, phases into each other is brought about until the phase equilibrium is reached, i.e. H. The phenols contained in the coal oil dissolve in the aqueous sodium hydroxide solution. In the middle section of the extractor, the inhomogeneous mixture separates into the lighter, organic raffinate (de-phenolic carbon oil) and the heavy extract (phenol-containing sodium hydroxide solution) due to different densities. The two phases are subtracted separately. The upper phase is the target, phenol-free raffinate, the lower phase flows to stage 11.

In stage II, the simply pre-extracted light coal oil from stage 111 is extracted with the stage 1 extract, which is partially loaded with phenols.

In stage III, the raw coal light oil is conveyed by means of a metering pump and pre-extracted with the extract (phenol-containing sodium hydroxide solution) from the first two stages. The lighter, organic phase is led to stage 11. The heavy phase is removed from the process as a phenol-containing extract to recover the phenols.

According to FIG. 4, the light coal oil to be refined is introduced into the reaction system by means of a metering pump 1. Compressed make-up hydrogen is metered in before the preheater 2, in which the components are heated to a temperature slightly below the reaction temperature. The implementation takes place in a fixed bed reactor, which is electrically heated by a heating jacket with several control loops. On the catalytic converter, all organic sulfur, nitrogen and oxygen compounds contained in the oil are converted into hydrogen sulfide, ammonia, water and hydrocarbons, and gaseous decomposition products are also formed. After cooling 4, the product stream leaving the reactor is separated into gas and liquid phases in high-pressure separator 5. The gas phase is expanded via a gas expansion valve 8. It mainly consists of excess hydrogen, hydrogen sulfide and small amounts of C _i -C ₄ gases.

The liquid phase flows through an expansion valve 6 into a water-oil separating container 7. Here, the raffinate separates from the water of reaction due to the density differences, and also small amounts of dissolved gases are released as stripping gas.

The system according to FIG. 4 includes control loops with mass measurement WIR, volume measurement FIR, pressure measurement PI, temperature measurement TIRC, maintenance LIRC and pressure control PRC. Since, when the refined light coal oil is reformed, the reformer contact is quickly deactivated by oxygen and excessive water vapor partial pressure, the feed oil according to FIG. 5 is pumped through a deoxidizer 11 and dryer 12 by means of a pump 10. Subsequently, compressed hydrogen is added before a preheater 13, which heats the mixture to the reaction temperature. The following fixed bed reactor 14 must be heated from the outside to maintain the reaction. In the reforming, aromatics are formed from paraffinic and naphthenic hydrocarbons with the evolution of hydrogen.

After cooling the reaction mixture in a cooler 15, the oil separates from the gas phase in the high-pressure separator 16.

After expansion, the oil is pumped into a stabilizing column 18 by means of expansion valve 17, in which low-boiling hydrocarbons are removed by distillation. The associated pump is designated 19. The distillation sump is the aromatic-rich reformate. The gaseous phase from the high-pressure separator is freed of organic constituents under system pressure in a gas scrubber and gas dryer 20 and is returned as a cycle gas by means of a cycle gas compressor 21. The hydrogen formed during the reforming leaves the process via a valve 22 as excess gas.

The control devices belonging to the system according to FIG. 5 have the same designations as the control devices according to FIG. 4.

Claims (3)

1. Process for the preparation of a low benzene content, environmentally-acceptable petrol derived from carbonaceous light oil, characterised in that a core fraction boiling at 145-185 °C is distilled off from the crude carbonaceous light oil, the phenol in the core fraction is separated out, the separation is conducted by extraction using aqueous soda lye or sodium phenolate lye, and the phenol-free raffinate of the core fraction is mixed with the portion of the carbonaceous light oil boiling at up to 145 °C and worked up by raffination and reforming to give a low benzene content petrol having an increased octane number.

2. Process according to claim 1, characterised in that a packed column is used for distillation.

3. Process according to claim 1, characterised in that the extraction is conducted in a 3-phase mixer-settler-extractor.

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