DE3610580A1 - METHOD FOR SOLVING SULFUR AND PRODUCT FOR CARRYING OUT THIS METHOD - Google Patents

Description

5006 B.301 -U-

description

/ J The invention relates to a method for dissolving sulfur and a product for performing this process. The invention also relates to the regeneration of products which serve to dissolve sulfur. An important field of application of the invention is the dissolution of Sulfur deposits that can occur in lines that are used to transport sulfur-containing materials.

\\ J In certain cases, when treating substances that release elemental sulfur in industry, difficulties are encountered with the transport of these substances as sulfur deposits form on the inner walls of the pipes. These deposits, which initially lead to a reduced flow of the substances to be treated, can reach such an extent that the passage is partially or completely blocked. This problem is of particular concern with sulfur-rich natural gas sources. With these gases with a high concentration of sulfur, the difficulties due to sulfur deposits on the inner walls of the pipelines can lead to complete blockage of the pipelines. Thus, it is necessary to remove the deposited sulfur. The most expedient measure for this, which is currently Commonly used in industry, it consists in dissolving the deposits of this element using a suitable solvent. The dissolution of sulfur deposits has hitherto been carried out with solvents such as carbon disulfide, alkyl sulfides, dialkyl disulfides or aqueous ammonium sulfide solutions. While CSp is an excellent solvent for sulfur, it is expensive. Alkyl sulfides are relatively weak

Dissolving power, while ammoniacal solutions, which do not lead to a simple physical dissolution, but rather form polysulphides, require a complicated and ultimately uneconomical further treatment. The dialkyl disulfides used according to the prior art are quite effective means of removing sulfur deposits when used under certain conditions. According to US Pat. No. 3,846,311, dialkyl disulfides, in particular with Cp-C -..- alkyl radicals, ie the compounds C ₂ H ₅ SSC ₂ H ₅ to C ... H ₂ ^ SSC. ^ H ₂ ^, a strong dissolving power, if they are mixed with an amine, in particular with 10 percent by weight, and then allowed to "age" ^{at 24 ° C. for 30 to 90 days.} According to this prior art, dissolution of up to 564 g of S per 100 g of dialkyl disulfide at 93 ° C. is achieved. According to US Pat. No. 4,239, the rate of dissolution is greatly increased by adding a small amount of elemental sulfur beforehand to the system composed of dialkyl disulfide and amine.

Recently it was also shown that under the action of suitable catalysts, NaSH, sodium salt of thiophenol and mercaptides in the presence of a cosolvent, dimethylformamide (DMF), dimethyl disulfide (DMDS) or mixtures of organic disulfides (referred to as "Merox") with large amounts of sulfur dissolve at particularly high speed (ASR Quaterly Bulletin, Vol. XIX, No. 1, 2, 3, Vol. XX, No. 3). The use of dimethyl disulfide or mixtures of organic disulfides in the presence of appropriate additives is in the course of cleaning lines for the recovery of H _? S and dissolved sulfur-rich gases have been carried out on an industrial scale for some time, but the sulfur deposits observed in the currently exploited natural gas sources are sufficiently slow that a

discontinuous injection of disulfide for cleaning is possible. The disulphide is not recycled and is destroyed after flowing out of the line. On the other hand, when using gases with a very high sulfur content, which _{contain up to 90 percent H 5} S and can carry 50 to 100 g of sulfur per m of gas, this discontinuous procedure can no longer be carried out. Only a continuous injection of the organic disulfide used for cleaning enables the treatment of these sulfur deposits. This results in a considerable consumption of organic disulfides, so that the recycling of this agent is absolutely necessary. However, with continuous injection it is important that the composition of the solvent used remains largely constant.

In fact, the speed and extent depend on the Dissolution of sulfur in an organic disulfide to a considerable extent, depending on the length of the hydrocarbon chain of the disulfide. Disulfide mixtures from refineries (with the designation "Merox") are seldom of constant Composition, this applies to products from the same refinery and even more so to products from different ones Refineries. These mixtures are therefore difficult to use while in a continuous process industrially produced dimethyl sulfide of constant purity and reasonable cost is well suited. In present of an amine and traces of mercaptans or of a mercaptide or of a hydrogen sulfide and of dimethylformamide (DMF) Dimethyl disulfide (DMDS) has a considerable amount Dissolving power for sulfur; namely, it can dissolve up to 7 times its own weight at 80 ° C. However At these temperatures, the effect of dimethyl disulfide on sulfur is not just a simple one

5006 B.301

physical dissolution, but also in a chemical reaction leading to the formation of dimethyl polysulphide mixtures leads. The physical properties, such as density, viscosity and the like, depend largely on the amount of the in solution gone sulfur.

In the context of the present invention, it was found, for example, that when using dimethyl disulfide with a content of 1 percent triethylamine and 0.1 percent mercaptan (methyl or tert-dodecyl mercaptan) and when adding different amounts of sulfur, dimethyl polysulfide mixtures with the following compositions (mol percent at 2O ⁰ C).

^ v ^ mixture 1 mole of DMDS + 1 mole of DMDS + 1 mole of DMDs + Components ^ "^ **» * ^ 1 mole dissolved
sulfur 2 mol ge
solver
sulfur 3 mol ge
solver
sulfur CH ₃ S ₂ CH ₃ 34% 15% 10% CH ₃ S ₃ CH ₃ 39% 30% 24% CH ₃ S ₄ CH ₃ 18% ■ 24% 22% CH ₃ S ₅ CH ₃ 6% 16% 19% ^CH 3 ^S V 6 ^CH 3 3% 15% 26%

According to the invention it was also found that dimethyl polysulfide mixtures themselves can represent solvents for sulfur, provided that their composition is within them moves within certain limits. The DMDS that is used continuously has to be regenerated by breaking down the higher polysulphides unless it is possible to use a dimethyl polysulphide mixture in the pipelines to be cleaned Cycle that can replace DMDS.

BATH ORIGINAL

5006 B-301 - 8 -

This last-mentioned condition is according to the invention in met in an economic and unforeseen way. According to the invention it is namely possible per weight unit to dissolve much more sulfur than this was made possible by the state of the art.

The invention is based on the findings that higher dimethyl polysulfides are excellent solvents for sulfur; that the temperature-related solubility difference of sulfur between the temperatures prevailing at the head of natural gas wells of generally UO to 80 C (where the sulfur separates) and the ambient temperatures (-40 to 20 C) at which the dissolved sulfur precipitates again must be, is considerable; and that it is possible to use dimethylpolysulphides of constant composition and constant physical properties in the course of recirculation after injection into natural gas pipelines for gases with high sulfur content.

Thus, the inventive method is characterized by treating the sulfur at a temperature between 40 and 100 ⁰ C and preferably between 60 and 90 ⁰ C with a Diraethylpolysulfidgemisch containing the following components: 1 to 3 percent by weight dimethyl disulfide, from 35 to 45 weight percent CHLS CH- ,, where χ has a value from 3 to 5, remainder homologous polysulfides in which χ has a value of 6 or more and in particular from 6 to 8.

Preferably, after cooling to 20 ° C. or below, in particular to 20 to -40 ° C., and after the deposition of the precipitated sulfur, the remaining liquid is reused to dissolve the sulfur again.

BATH ORIGINAL

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Preferably, the polysulfide mixture with 2 to 10 percent of an amine, an amide, a mercaptan and / or Mercaptids spiked. The following are expediently used: Liquid lower aliphatic amines, diamines and cyclic ones Amines, e.g. diethylamine, triethylamine, dipropylamine, diisopropylamine, octylamine, dodecylamine, ethylenediamine, propylenediamine, optionally substituted, pyridine, piperidine and the like; Formamide, acetamide, propionamide, dimethylformamide, diethylformamide, Ethylacetamide, dimethylpropionamide and the like; Mercaptans and mercaptides with 2 to 18 carbon atoms and the like. All of these compounds are mentioned by way of example only and are not intended to be limiting.

The process according to the invention is preferably carried out with a mixture which has the following percentages by weight of compounds of the formula CH _Q S CH _Q

j X j

contains:

1.5 to 2.5% for χ = 2

9.5 to 11.5% for χ = 3

13.5 to 15.5% for χ = 4

14 to 16% for χ = 5

19 to 21% for χ = 6

32 to 35% for χ * 7

The lowest temperatures for the solution are between 70 and 90 ⁰ C and for precipitating between 10 and 3O ⁰ C. The solvent mixture preferably contains from 3 to 5 percent amine, amide, mercaptan and / or mercaptide, in particular, dimethylformamide. The sulfur content to be dissolved is set to 1200 to 3000 g and preferably to 1300 to 2600 g for 1000 g of solvent mixture. The composition of the recycled liquid polysulphide is then well constant, and the recycling can be carried out with yields that are very favorable for industrial purposes, for example 50 to

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90 percent, what is operated compared to the discontinuous Prior art methods where the dimethyl disulfide is lost after a single use one represents a significant advantage.

Compared to the prior art mentioned above, in which the DMDS initially ages for several days is subjected, a considerable gain in time can be achieved by the method according to the invention.

It thus follows that in the method according to the invention a new solvent for sulfur is used, which is made from a mixture of polysulfides of the formula CH, S CH_

j X 5

consists and 1 to 3 percent by weight of compounds with χ = and contains 35 to 45 percent by weight of polysulfides with χ = 3 to 5, the remainder of polysulfides with χ 2; 6 and in particular 6 to 8 consists.

The invention also relates to the aforementioned solvent mixtures containing 2 to 10 percent of an amine, of an amide and / or a mercaptan, examples of which are given above, are added.

Products preferred according to the invention contain 1.5 to 2.5 Percent by weight of compounds with χ = 2, 9.5 to 11.5 percent by weight with χ = 3, 13.5 to 15.5 percent by weight with χ = 4, 14 to 16 percent by weight with χ = 5, 19 to 21 percent by weight with χ = 6 and 32 to 35 percent by weight with χ ^ 7. These mixtures preferably also contain 3 to 5 percent by weight of an amine, amide and / or mercaptan, especially dimethylformamide.

The invention is explained in more detail below with the aid of examples.

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example 1

Preparation of the solvent, ie a Dimethylpoly s ulfidgemisohes

890 g of commercially available DMDS, 100 g of dimethylformamide (DMF), 10 g of NaSH as a catalyst and 2000 g of sulfur are placed in a 5 liter reaction vessel equipped with a stirrer and an external heating device. The mixture is heated with continuous stirring at 8O ⁰ C and kept at this temperature is completely dissolved until the sulfur. The reactor contents are then poured into a sedimentation container left ^{at 20 ° C.} The supernatant mixture contains 64 percent of the supplied sulfur and is a mixture of DMF and dimethyl polysulphide with the following composition:

CH ₃ S ₂ CH ₃ = 2 wt%; CH ₃ S ₃ CH ₃ = 10.4 wt%; CH ₃ S ₄ CH ₃ = 15.0 wt%; CH ₃ S ₅ CH ,, = 15.3 wt%; CH ₃ S ₅ CH ₃ = 20.5 wt%; CH ₃ S * _? CH ₃ = 32.8 wt%; DMF = 4% by weight.

The maximum solubility for sulfur this mixture at 8O ⁰ C is 5450 g sulfur per 1000 g of mixture.

Example 2

Use and recycling of the polysulphide mixture from Example 1

The polysulphide mixture obtained according to Example 1 is used in the same device and in the same way as in Example 1 to dissolve sulfur. Here are heated 1000 g of Polysulfidgemisches and 1000 g of sulfur at 8O ⁰ C, is completely dissolved until the sulfur. It is then cooled to 20 ^° C. and the supernatant phase and the precipitated sulfur are obtained. 800 g of the supernatant are then brought into contact with 800 g of sulfur again until the sulfur has completely dissolved. It is then cooled ^{to 20 ° C.} This process will

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5006 B.301

repeated several times in succession, with a certain amount of the supernatant with an equivalent amount by weight of sulfur each heated to 80 ° C and is then cooled to 20 ⁰ C.

The successively obtained supernatants are after each dissolution / precipitation cycle (run-through) analyzed and the amount of supernatant lost with each run is measured.

i 1st run 2nd run 3. Through
run 4. Through
run CH ^ S 2 CH η
CH ₃ S ₃ CH ₃
CH ₃ S ₄ CH ₃
CH ₃ S ₅ CH ₃
CH ₃ S ₆ CH ₃
^CH 3 ^S > / 7 ^CH 3
DMF 1.8%
11 *
15.2%
15.4%
20%
32.5%
4.1% 1.8%
10.2%
14.1%
15.1%
20.5%
34.4%
3.9% 1.6%
10.5%
14.2%
15.5%
20.3%
33.9%
4.0% 1.5%
10.3%
14.0%
15.0%
20.6%
34.8%
3.3% Loss of supernatant 18% 17.8% 18.7% 18% Recycle yield 82% 82.2% 81.3% 82% maximum solubility.
of sulfur in the he
keep surviving ⁵⁴⁷ 9 Schwe
fei pro
1 00g about
was standing . 539g
Per
100 g
Got over 536g
Per
100 g
Got over 539g
oro
roog
Got over

The result is that the dimethyl polysulphide mixture is practically constant with each dissolution / precipitation run Has composition. The solution properties for sulfur remain constant after each run. The maximum

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Dissolving power is in the vicinity of 540 g of sulfur per 100 g at 80 ° C. The erosion
each in the range of 82 percent.

fei per 100 g at 80 ° C. The yield of polysulfides is

Example 3

A dimethyl polysulphide mixture is produced according to Example 1. This mixture thus has the same composition as in Example 1. In the apparatus described above, 1000 g of dimethyl polysulphide and 2000 g of sulfur are stirred at 80 ° C. in the manner described above until the sulfur is completely dissolved. It is then cooled ^{to 20 ° C.} The precipitated sulfur and the supernatant phase are recovered.

800 g of the supernatant is then stirred with 2 times the amount by weight of sulfur at 8O ⁰ C, is completely dissolved until the sulfur. It is then cooled ^{to 20 ° C. again.} This procedure is repeated several times. After each pass, a certain amount of the supernatant phase is stirred with 2 times the amount by weight of sulfur at 80 C and then cooled to 2O ⁰ C. The supernatants obtained after each pass, which consists of dissolving and precipitating the sulfur, are analyzed. It can be seen that their composition remains practically constant and has approximately the following distribution: CH ₃ S ₂ CH ₃ = 1.2%; CH ₃ S ₃ CH ₃ = 10.5%; CH ₃ S ₄ CH ₃ = 14.4%; CH ₃ S ₅ CH ₃ = 15.5%; CH ₃ S ₆ CH ₃ = 19.5%; CH ₃ S ^ ₇ CH ₃ = 34.9%; DMF = 4%.

The mixture is after each pass per 100 g of polysulfides to resolution of approximately 45 g sulfur at 8O ⁰ C in the situation.

The recycling yield of polysulfides is less than in example 1; namely, it is in the region of 73 percent

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During the precipitation, the sulfur absorbs a certain proportion of dimethyl polysulfides, the amount absorbed being higher, the greater the ratio of precipitated sulfur / polysulfide supernatant. If the above recirculation processes are repeated while dissolving at 80 ^° C. with:

(a) 3000 g of sulfur per 1000 g of polysulphide mixture according to Example 2;

(b) UOOO grams of sulfur per 1000 grams of the same mixture;

(c) 5450 g sulfur (saturation) per 100 g precipitation mixture; the following recycling yields of disulfides are found: 51 percent for (a), 33 percent for (b) and V10 percent for (c).

It is therefore not advisable to use the polysulphides when injecting the solvent mixture into the pipe to be cleaned too heavy to load with sulfur.

Example 4 Production of the dimethyl polysulphide mixture

989 g of commercially available DMDS, 1 g of tert-dodecyl mercaptan, 10 g of triethylamine and 2000 g of sulfur are placed in a 5 liter reaction vessel equipped with a stirrer and an external heating device. The mixture is heated to 80 ° C. with continuous stirring until all of the sulfur has dissolved. The contents of the reactor are then poured into a sedimentation container left at 20 ° C. The supernatant contains 60 percent of the sulfur supplied. It consists of a dimethyl polysulfide mixture with the following composition: CH ₃ S ₂ CH = 1.5% by weight; CH ₃ S ₃ CH = 12 wt%; CH ₃ S ₄ CH = 16.7 wt%; CH ₃ S ₅ CH ₃ = 16.9 wt%; CH ₃ S ₆ CH ₃ = 23.1 wt%; CH ₃ S ^ ₇ CH ₃ = 29.8 wt%.

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The maximum solubility of the mixture for sulfur is 560 g per 100 g mixture at 80 ° C.

Example 5 Use and recycling of the solvent from Example 4

In the device of example 1, the dissolution of sulfur in the dimethyl polysulfide mixture prepared in the manner described above is carried out according to example 1. This treatment consists in stirring 100 g of polysulfide mixture and 1000 g of sulfur at 80 ° C. until the sulfur has completely dissolved. After cooling to 20 ^° C., the liquid supernatant and the precipitated sulfur are obtained. ^{800 g of supernatant are heated again to 80 °} C. in the presence of an equivalent amount of sulfur (800 g) until the sulfur has completely dissolved. It is then cooled ^{to 20 ° C. again.} The process is repeated several times, one after the other, with the same amount of sulfur being added to a certain amount of the supernatant solution with each pass. After the sulfur has completely dissolved, the mixture is brought back to 20 ^° C. in each case.

The supernatant solutions obtained in the above-mentioned manner are analyzed after each run. The following Results are obtained.

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5006 B.301

1.
Pass 2.
Pass 3.
Pass 6% 4th
Pass CH ₃ S ₂ CH ₃ 0.8% 0.8% 0, 9% 0.5% ^CH 3 ^S 3 ^CH 3 12.1% 12% 11 4% 11.9% 16.5% 16.6% 16, 1% 16.3% CH ₃ S ₅ CH ₃ 16.9% 17.1% 17, 5% 17.0% CH ^ Sy-CH-j 23.6% 23.5% 23, 4% 23.7% CH ₃ S ^ ₇ CH ₃ 30.1% 30.0% 30, 8th% 30.4% Return from
loot of folysul
fidgeraisch 83.9% 84.2% 83, 556 g
Sulfur.
per 100 g 83.5% maximum solubility
of sulfur in the
obtained polysul-
fidphase 564 s
sulfur
Per
100 g 558 g
sulfur
per 100 g 557 g
sulfur
per 100 g

It should be noted that after several successive recirculations, the polysulphide phase practically changes does not change and retains its solvent power for sulfur. The recycle yield is in the region of 84 percent.

If the above experiment is repeated, but instead of dissolving 1000 g of sulfur in each run, the one below is dissolved listed quantities:

(a) 2000 grams of sulfur per 1000 grams of polysulfides;

(b) 3000 g sulfur per 1000 g polysulphides or

(c) 5500 grams of sulfur (saturation) per 1000 grams of polysulfides;

this results in the following lower recycle yields of polysulfide mixtures: 75 percent for (a), 50 percent for (b) and < 10 percent for (c), since part of the polysulfides is absorbed on the precipitated sulfur.

End of description

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Claims (9)

Claims 1. Method of dissolving sulfur using a liquid Dialkyl polysulphide, characterized in that this solvent consists of a mixture of dimethyl polysulphides with a content of 1 to 3 percent by weight dimethyl disulfide and 35 to 45 percent by weight Compounds of the formula CH “S CH ,, in which χ has a value has from 3 to 5, with the remainder consisting of homologous polysulfides in which χ has a value of 6 and more, especially 6 to 8. - 1 - Munich-Bogenhausen. Poschingerstraße 6 Telegram: Chemindus Munich - Telephone: (089) 98 32 22 Telex: 5 23 992 (abitz d) B.301 - 2 - 2. The method according to claim 1, in which the dissolution takes place at a temperature of 40 to 100 ⁰ C and the precipitated sulfur after cooling to 20 ⁰ C or below is separated from the liquid, characterized in that the liquid for renewed dissolution of sulfur is reused. 3. The method according to claim 2, wherein the polysulfide used with a small proportion, in particular 2 to 10 percent by weight, of an amine, amide, mercaptan and / or Mercaptids is added, characterized in that the recycled polysulfide composition is essentially is the same as the polysulfide used for the first dissolution. 4. The method according to claim 3, characterized in that the aid consists of one or more of the following compounds: liquid lower aliphatic Amines, diamines and cyclic amines, especially diethylamine, triethylamine, dipropylamine, diisopropylamine, Octylamines, dodecylamines, ethylenediamine, propylenediamine, which can optionally be substituted; Pyridine, piperidine, Formamide, acetamide, propionamide, dimethylformamide, diethylformamide, Ethylacetamide, dimethylpropionamide; Mercaptans and mercaptides with 2 to 18 carbon atoms. 5. The method according to any one of the preceding claims, wherein the dissolution of the sulfur at temperatures of 70 to 90 ⁰ C and the precipitation takes place at temperatures of 10 to 30 ⁰ C, characterized in that the polysulfide mixture contains the following proportions of compounds of the formula CH-jS CH- in percent by weight: B.301 -3- ~~ ^ 1.5 to 2.5% by weight for x = 2 9.5 to 11.5% by weight for χ = 3 13.5 to 15.5% by weight for χ = 4 14 to 16% by weight for χ = 5 19 to 21% by weight for χ = 6 32 to 35% by weight for χ -h 7 6. The method according to any one of the preceding claims, characterized in that the proportion of dissolved sulfur set between 1200 and 3000 and preferably between 1300 and 26ΟΟ g per 1000 g of solvent mixture wherein the composition of the recycled liquid polysulfide remains essentially constant. 7. Application of the method according to one of the preceding claims for the removal of sulfur that is in lines, especially in natural gas pipelines. 8. Product for dissolving sulfur, which contains dimethyl disulfide, characterized in that it consists of a liquid mixture of dimethyl polysulfides containing 1 to 3 percent by weight of dimethyl disulfide and 35 to 45 percent by weight of compounds of the formula CH ~ S CH ,,, in which χ has a value of 3 to 5 consists, with the remainder consisting of homologous polysulfides in which χ has a value of 6 and more, in particular 6 to 8, has. 9. Product according to claim 8, characterized in that the polysulfide mixture is 1.5 to 2.5 percent by weight of compounds with χ = 2, 9.5 to 11.5 percent by weight with x = 3, 13.5 to 15.5 percent by weight with χ = 4, 14 to 16 percent by weight with χ = 5, 19 to 21 percent by weight with χ = 6 and 32 to 35 percent by weight with χ i 7 contains, this mixture preferably also 3 to weight percent of an amine, amide and / or mercaptan, especially dimethylformamide.