EP0904336B1 - Method of preparing low-sulphur aliphatic compounds - Google Patents

Abstract

Low-sulfur aliphatic compounds are obtained from olefin-rich starting materials contaminated with organic sulfur compounds.

Description

The invention relates to a process for the production of low sulfur aliphatic compounds and in particular a method for Desulphurization of olefin-rich hydrocarbons by liquid-liquid extraction.

Olefin-rich hydrocarbon mixtures are available in large quantities available from cracker plants. In particular, so-called Vacuum residue oils in thermal crackers (Visbreaker, Coker) converted to low-boiling fractions, which are characterized by are characterized by a high olefin content. These products are e.g. in catalytic processes such as fluid catalytic cracking (FCC) or hydrocracking, processed into fuels.

Another example of the large-scale use of this Hydroformylation is an olefin-rich hydrocarbon mixture for the production of higher aldehydes and / or alcohols Reaction with hydrogen and carbon monoxide in the presence of a Catalyst. The resulting alcohols serve e.g. as a solvent or are e.g. for the production of plasticizers used. It turns out, as is common with many processes for the catalytic processing of olefin-containing hydrocarbon mixtures, the high sulfur content of these mixtures is a problem, since the sulfur compounds contained are often used as catalyst poisons Act. This applies in particular to thermal Cracking heavy residual oil-rich olefin Hydrocarbon mixtures that have an undesirably high sulfur content may have, the sulfur impurities in essentially as aromatic compounds, such as in particular thiophene, available.

Methods are known from US-A-4,711,968 and US-A-4,922,028 direct hydroformylation of sulfur-containing, olefin-rich hydrocarbon mixtures from thermally cracked petroleum streams known, but only certain, minimal sulfur concentrations having distillation fractions are used.

The desulfurization of hydrocarbon mixtures is carried out after State of the art catalytically predominantly under hydrogenation / dehydrogenation conditions carried out, e.g. in Ullmann's Encyclopedia of Industrial Chemistry, 5th ed., 1991, vol. A18, pp. 65-67. The catalytic hydrogenation, the so-called Hydrotreating, the sulfur compounds contained in Converted hydrogen sulfide and then with a suitable Washed out solvent. The catalysts used however, also cause the partial hydrogenation of the Olefins, which with regard to further processing, e.g. by Hydroformylation is disadvantageous.

Describes as an alternative to the catalytic hydrogenation process EP-A-653 477 desulfurization of light oils by liquid-liquid extraction with nitrogen-containing heterocycles or acid amides, preferably N-methylpyrrolidone and 1,3-dimethyl-2-imidazolidinone be used. The big disadvantage of this The process consists in the low selectivity of the used Extracting agent compared to the starting hydrocarbons, so that also in this process the content of desired olefins is reduced.

Selective liquid-liquid extraction process for the extraction of aromatic Hydrocarbon mixtures from aromatic-non-aromatic Mixtures as e.g. incurred during the naphtha workup, are in Ullmann's Encyclopedia of Industrial Chemistry, 5th ed., 1985, vol. A3, pp. 491-496. Some of the ones there mentioned solvents (furfural, sulfuran, dimethyl sulfoxide, Diethylene glycol) were described in EP-A-653 477 for comparison purposes used for desulphurization by liquid-liquid extraction. However, they have proven unsuitable for this purpose.

DE-A-20 40 025 describes a process for the separation of high-purity aromatics from hydrocarbon mixtures by liquid-liquid extraction with downstream extractive distillation, where morpholine and / or N-substituted morpholines in combination be used with water as a solvent. This method finds practical application in the Krupp-Koppers morphylan process, who is also in Ullmann's Encyclopedia of Industrial Chemistry, 5th ed., 1995, vol. A3, pp. 491-496. The DE-A-20 40 025 does not deal with the problem of selective Removal of sulfur contaminants from olefin-rich Starting products and the subsequent catalytic processing of desulfurized products.

The present invention is therefore based on the object a process for the preparation of low-sulfur aliphatic compounds from olefin-rich intermediate products without significant reduction to provide the olefin content.

a) das schwefelhaltige olefinreiche Ausgangsprodukt einer ein-oder mehrstufigen flüssig-flüssig-Extraktion mit einer morpholinhaltigen Extraktionsflüssigkeit unterzieht,

b) das Extraktionsmittel und die darin enthaltenen Schwefelverbindungen abtrennt und gegebenenfalls

c) das schwefelarme aliphatische Produkt weiterverarbeitet.

Surprisingly, it has now been found that this object is achieved by providing a process for the preparation of low-sulfur aliphatic compounds from olefin-rich starting products contaminated with organic sulfur compounds

a) subjecting the sulfur-containing olefin-rich starting product to a single-stage or multi-stage liquid-liquid extraction with a morpholine-containing extraction liquid,

b) the extractant and the sulfur compounds contained therein, and if appropriate

c) the low-sulfur aliphatic product is further processed.

According to the invention, olefins which are olefin-rich starting products are Olefin mixtures or olefin-rich hydrocarbon mixtures in Question with organic and especially aromatic sulfur compounds are contaminated. Preferred source products however, are olefin-rich hydrocarbon mixtures, just like them e.g. in the petrochemical industry for thermal cracking processes (Visbreaker, Coker). These hydrocarbon mixtures have a high content of organic, mainly aromatic Sulfur compounds. Because of the high olefin content such hydrocarbon mixtures are ideal starting products for the catalytic conversion to secondary products, such as Aldehydes and alcohols. The invention now surprisingly enables desulphurization of these mixtures with high selectivity, so that poisoning for the subsequent reactions necessary catalysts, e.g. Nickel catalysts at the Alcohol production, is avoided.

According to the invention, the selective desulfurization surprisingly succeeds in that an extracting agent containing morpholine used that at a pressure of about 1 atm and a temperature of about 25 ° C a relative depletion ratio of aromatic Sulfur contamination to olefin greater than about 10, such as. from about 10 to 30.

The relative depletion ratio is a measure of the selectivity of the extractant used. It is the bigger, ever more aromatic sulfur compounds and the less olefin in the extractant phase are transferred.

The depletion ratio can be for a particular extractant reliable, for example by extracting coker gasoline fractions, be determined because of their sulfur contamination consists mainly of aromatic sulfur compounds. The relative depletion ratio is defined by the quotient from percentage decrease in sulfur content, determined by X-ray fluorescence spectroscopy, and percentage decrease in Olefin content, determined according to DIN 51774.

The morpholine-containing extraction liquid used according to the invention is preferably selected from morpholine and morpholine derivatives which can carry a C ₁ -C ₇ -acyl or C ₁ -C ₇ -alkyl radical on the nitrogen atom, which is optionally substituted by hydroxylamino or mercapto groups or in the alkyl part carries a heteroatom selected from O, N and S, or mixtures thereof, optionally in combination with water or a liquid miscible with the morpholine compound contained. These include ketones of nitrogen heterocycles, such as, for example, pyrrolidones, imidazolidinones, pyrimidinones, piperidones, pyrazolidinones and piperazinones, certain acid amides, such as, for example, dimethylformamide, diethylformamide and dimethylacetamide, sulfur-containing solvents, such as, for example, tetrahydrothiophene dioxide and, for example, ethylene and dimethyl sulfoxide, such as ethylene glycol and dimethyl sulfoxide.

Suitable N-substituted morpholine compounds are in particular NC ₁ -C ₇ alkyl and NC ₁ -C ₇ acylmorpholine compounds. Examples include N-methyl, N-ethyl, Nn-propyl, Nn-butyl, Nn-pentyl, Nn-hexyl, Nn-heptyl, N-formyl, N-acetyl, , N-propionyl, N-butyryl, N-valeryl, N-hexanoyl or N-hetpanoylmorpholine.

The amount of morpholine or N-substituted morpholine compounds can vary in a wide range. Generally is the weight ratio of morpholine or morpholine compound to hydrocarbon mixture at least 1: 1. It is particular in the range from 2: 1 to 5: 1. Temperature and pressure at which the extraction is done are not critical. in the generally one works at ambient temperature and normal pressure. However, higher temperatures and pressures can also be used come.

The liquid-liquid extraction is carried out in the usual way. Suitable apparatus and procedures are known to the person skilled in the art known and e.g. described in Ullmann, 3rd ed., 1951, Vol. 1, pp. 409-428. Examples are the use of sieve tray columns, Extraction columns with mixing and rest areas, e.g. Stirring columns, and extraction batteries, e.g. Mixer-settler equipment. It is preferred to carry out the extraction in countercurrent. The extractant is preferably recycled.

The desulfurized products obtained have essentially one unchanged olefin content and at least 60%, in particular at least 80% and preferably at least 90% reduced Sulfur content.

The desulfurized product produced according to the invention can either a single olefin, a mixture of olefins or an olefin rich Be hydrocarbon mixture and as such its intended use be fed. The method according to the invention comprises thus only process steps a) and b) and thus represents a pure desulfurization process.

However, the desulfurized product may also be desirable to process them in a subsequent step. Procedural step c) can, for example, the distillative workup of the prepared olefin mixtures or olefin-rich hydrocarbon mixtures include. However, according to the invention, especially such Sulfur compounds are removed that act as catalyst poisons are known, e.g. Thiophenes, will be obtained desulfurized olefin mixtures, preferably in catalytic processes, such as. hydroformylation, to higher alcohols or Aldehydes processed.

The invention also relates to the use of the above morpholine-containing extracting agent for desulfurization of olefins, olefin mixtures or olefin-rich hydrocarbon mixtures.

The invention is illustrated by the following, not limiting Examples and comparative examples explained.

As a starting hydrocarbon mixture for liquid-liquid extraction became a coker gasoline fraction with a sulfur content (determined by X-ray fluorescence spectroscopy) of 6200 up to 7100 ppm used. The olefin content was in the form of the bromine number determined according to DIN 51 774 T1-3, Aug. 1975 and was 64 to 71 g / 100 g.

Example 1

The starting hydrocarbon mixture was according to the invention liquid-liquid extraction in a one-step stirring test treated with N-formylmorpholine (NFM) as an extractant.

The following conditions have been set:

relationship NFM / hydrocarbon mixture 3/1 (kg / kg) print 1.013 bar temperature 25 ° C

The following results were achieved:

Decrease in olefin content (%) 3rd Decrease in sulfur content (%) 66 Depletion ratio 22

Comparative Example 1

The starting hydrocarbon mixture was by liquid-liquid extraction in a one-step stirring test using N-methyl-2-pyrrolidone (NMP) as an extractant among the same Conditions treated as in Example 1.

The following results were achieved:

Decrease in olefin content (%) 25th Decrease in sulfur content (%) 78 Depletion ratio 3.1

Example 2

The starting hydrocarbon mixture was according to the invention liquid-liquid extraction in a six-stage mixer-settler system treated.

The following conditions have been set:

Extraction agent
relationship N-formylmorpholine (NFM) NFM / KW mixture 3.5 / 1 (( ^{kgh -1} ) / ( ^{kgh -1} )) print 1.013 bar temperature 25 ° C

The following results were achieved:

Decrease in olefin content (%) 7 Decrease in sulfur content (%) 95 Depletion ratio 13.5

The comparison between Example 1, Comparative Example 1 and Example 2 shows that it is using NFM as an extractant is possible to use olefin-rich hydrocarbon mixtures in the desulfurize substantially without reducing the olefin content.

When using a six-stage mixer-settler apparatus the sulfur is broken down almost quantitatively.

Comparative Example 2

The starting hydrocarbon mixture was according to the state of the Technique catalytically treated under dehydrogenation conditions.

The following conditions have been set:

catalyst CoMo / Al ₂ O ₃ print 1.013 bar WHSV 1.0 kg / (lh) H ₂ / hydrocarbon mixture 2/1 (mol / mol) temperature 500-600 ° C

The following results were achieved:

temperature (0 ° C) 500 550 600 Decrease in olefin content (%) 57 49 33 Decrease in sulfur content (%) 66 52 20th Depletion ratio 1.2 1.2 0.6

Comparative Example 3

The starting hydrocarbon mixture was according to the state of the Technology catalyzed under hydrogenation conditions.

The following conditions have been set:

catalyst Ag / Al ₂ O ₃ print 20 bar WHSV 0.25 kg / (lh) H ₂ / KW mixture 2/1 (mol / mol) temperature 140-220 ° C

The following results were achieved:

Temperature (° C) 180 220 Decrease in olefin content (%) 13 62 Decrease in sulfur content (%) 70 69 Depletion ratio 5.4 1.1

The comparison between Example 2 and Comparative Examples 2 and Figure 3 shows that it is contrary to the method of the invention to the hydrogenation and dehydrogenation processes corresponding to the prior art is possible, olefin-rich hydrocarbon mixtures to desulfurize selectively without reducing the olefin content.

Claims (11)

1. A process for producing low-sulfur aliphatic compounds from olefin-rich starting materials contaminated with organic sulfur compounds, which comprises

   a) subjecting the sulfurous olefin-rich starting material to a single- or multi-stage liquid-liquid extraction with a morpholinic extractant,

   b) removing the extractant and the sulfur compounds comprised therein, and optionally

   c) subjecting the low-sulfur aliphatic product to further processing.
2. A process as claimed in claim 1, wherein the morpholinic extractant used provides a relative depletion ratio of aromatic sulfur contamination to olefin of greater than about 8 at a pressure of about 1 atm and a temperature of about 25°C.
3. A process as claimed in either of the preceding claims, wherein the morpholinic extractant is selected from morpholine and morpholine derivatives which are N-substituted by an unsubstituted or hydroxyl-, amino- or mercapto-substituted C₁-C₇-acyl or C₁-C₇-alkyl radical with or without a hetero atom selected from the group consisting of oxygen, nitrogen and sulfur in the alkyl moiety, or mixtures thereof, optionally in combination with water or with a liquid which is miscible with the morpholine compound present therein.
4. A process as claimed in any of the preceding claims, wherein the extractant is an N-C₁-C₇-acylmorpholine.
5. A process as claimed in any of the preceding claims, wherein the extractant is N-formylmorpholine.
6. A process as claimed in any of the preceding claims, wherein the extractant and the sulfurous olefin-rich starting material are present during the extraction step in a weight ratio of from about 1:1 to about 5:1.
7. A process as claimed in any of the preceding claims, wherein the olefin-rich starting material to be desulfurized is an olefin mixture from the thermal cracking of residue oil.
8. A process as claimed in any of the preceding claims, wherein stage b) affords a desulfurized product comprising an olefin mixture which is further separated in stage c).
9. A process as claimed in any of the preceding claims, wherein stage b) affords a desulfurized product which is subjected to a catalytic conversion reaction in stage c).
10. A process as claimed in claim 9, wherein the catalytic conversion reaction is an olefin hydroformylation with subsequent catalytic reduction of the carbonylation product to the corresponding alcohol.
11. The use of a morpholinic extractant as defined in any of claims 2 to 5 for desulfurizing olefins, olefin mixtures or olefin-rich hydrocarbon mixtures.