DE890498C - Process for the slow oxidation of sulfur compounds - Google Patents

Description

Process for the slow oxidation of sulfur compounds The process according to the invention relates to the oxidation of easily oxidizable sulfur compounds with an oxygen-containing gas in the presence of a small amount of certain Oxidation catalysts. Easily oxidizable substances on which the process of the invention are applicable to those with mild oxidizing agents for example slowly but not spontaneously (i.e. with combustion or explosion) at room temperature can be oxidized, whereby predominantly different products form than the normal ones Oxides of the elements that make up the substance, such as carbon dioxide, water, sulfur dioxide etc. The substances to be oxidized should have a relatively low oxidation potential have (cf. Creighton & Koehler, "Electrochemistry", 3rd ed., Vol. I [1g35], P. 243ff.), D. H. the oxidation potential of the substances to be oxidized must be lower than the oxidation potential of the catalyst used or, in other words, the catalyst must have a higher oxidation potential than the substance to be oxidized own. Otherwise the catalyst would be preferred to that to be oxidized Substance to be oxidized.

The oxidizable substances can be inorganic or organic and include, for example, compounds of the following type: sulfhydrils (compounds, which contain the group - S H), such as hydrogen sulfide, methyl, ethyl, propyl, Butyl mercaptans etc., thiophenols and the corresponding salts, inorganic Polysulfides, such as sodium or calcium polysulfides, hyposulfites, such as Na2S204.

The products of oxidation of these substances are as follows: Hydrogen sulphide or its salts to free sulfur, mercaptans and thiophenols to the corresponding Disulfides, polysulfides to free sulfur and their corresponding thiosulfates, Hyposulfites to the corresponding thiosulfates.

The oxidation reactions are carried out in the liquid state, i.e. H. the substance to be oxidized is either in liquid form or dissolved or suspended in a suitable liquid medium, preferably in an alkaline one liquid medium. The catalyst is dissolved or in this liquid phase suspended.

The temperatures used in the oxidation are proportionate mild, d. H. they are below the decomposition temperature of the catalyst or the Evaporation temperature of the liquid phase, whichever is lower.

Atmospheric pressure is usually used, but if desired higher or lower pressures can also be used.

To accelerate the reaction, one or more catalysts are used polynuclear aromatic compounds that have multiple hydroxyl groups attached to the nucleus or the kernels contain bound or the appropriate quinones or tannin are used. Examples are: di- and trioxybenzenes and their corresponding quinones, which, preferably in the benzene ring, may contain other groups, e.g. B. alkyl, alicyclic, Aryl (condensed or not), carboxyl, amino, nitro, sulfonyl, phosphonyl and additional hydroxyl and / or oxy radicals or halogens. At least two the various hydroxyl groups should be in ortho or para positions to one another stand. If the hydroxyl groups are exclusively in the meta position, the is Compound less effective as a catalyst. Except for the amino substituent Metadirecting substituents are preferable because they help stabilize the core tend. In an aminopolyoxybenzene, a hydrogen atom can be in one or more the amino radicals can be substituted by a hydrocarbon or acyl radical.

Some preferred catalysts are: A. Polyoxy compounds hydroquinone, Catechol, resorcinol, pyrogallol, oxyhydroquinone, phloroglucinol, 2, 4, 6-trioxy-r-methyl-benzene, 2, 4, 6-Trioxy-z-ethyl-benzene, 2, 4, 6-Trioxy-i, 3-dimethyl-benzene, z, 2, 4, 5-tetraoxybenzene, i, 2, 3, 4-tetraoxybenzene, z, 2, 3, 5-tetraoxybenzene, pentaoxybenzene, hexaoxybenzene, 2,3-dioxynaphthalene, z, 2, 4-trioxynaphthalene, z, 6, 7-trioxynaphthalene; B. polyoxycarboxylic acids: 4,5-Dioxybenzoic acid, gallic acid, pyrogallol carboxylic acid, protocatechuic acid, caffeic acid; C. Quinones: Para- and ortho-benzoquinone, polyporic acid (2, 5-diphenyl-3, 6-dioxybenzoquinone), Antromentin (2, 5- (di-p-oxydiphenyl) -. 3,6-dioxybenzoquinone); D. Tannins: tannins can be divided into two groups of compounds: tannins of the ester type, which are usually derived from gallic acid, e.g. B. Chinese tannin, Turkish tannin, Hamamelitannin, etc., condensed tannins, which are not esters, but rather their kernels. held together by carbon bonds, like catechins, Tannins from the bark or wood of the oak or horse chestnut, quebracho bark, Quinotannic acid from Peruvian (fever) bark, etc.; E. Lignin compounds, which contain a polyoxyaromatic core; F. Substitution Products and Derivatives of the aforementioned compounds.

As mentioned above, the catalysts can also, for example, sulfur in the form of a sulfonyl group and represent easily oxidizable substances. When using the process according to the invention, a catalyst must also be used in this case and the substance to be oxidized may be different.

The amount of the catalyst in the liquid reaction mixture is ordinary less than the amount of substance to be oxidized. In addition, as already mentioned, the catalyst has a higher oxidation potential than the substance to be oxidized.

The amount of catalyst used can vary between about 0.5 and 5 percent by weight, preferably between 0.5 and 3 percent by weight, of the alkaline solution.

Within these limits require larger amounts of the catalyst faster oxidation of substances in a given solution. It is usually desirable to regulate the oxidation so that between about o, z and z percent by weight of the to be oxidized Substance together with the catalyst remain unoxidized in the liquid phase, to protect the catalyst against oxidation. This is especially important in the Regeneration of used alkaline treatment solutions, as described later will.

A specific embodiment of the present invention includes the following Measures; i. Extraction of hydrogen sulfide and / or Mercaptans from hydrocarbon mixtures containing these compounds with an aqueous alkaline solution, which - if necessary, a solubility promoter for the hydrogen sulfide or the mercaptans may contain; Separating the resulting aqueous alkaline solution phase which contains dissolved sulfhydrils; 3. Treat this separated solution with an oxidizing agent in the presence of one of the above Catalysts to precipitate free sulfur and / or organic disulfides; q. Removing these precipitated, neutral sulphides and 5. recycling the regenerated, aqueous alkaline solution obtained for the extraction of further sulfhydrils from further amounts of hydrocarbons.

The sulfhydrils can be any natural or synthetic Source. So contain petroleum or coal tar derivatives, such as natural or coke oven gas, natural gas and other gasoline, kerosene, etc. (both in the case of the direct distilled as well as the cracked products), usually hydrogen sulfide and / or mercaptans.

The sulfhydrils are oxidized in an alkaline solution, and therefore at least a portion of the sulfhydrils are in the form of their metal sulfides or Merkaptide.

Various alkaline treatment solutions can be used. If hydrogen sulfide is to be oxidized, the alkaline treating solution can be included : Alkali or alkaline earth hydroxides, phosphates, carbonates, phenolates, borates, arsenates, organic amines, such as alkanolamines or alkylenediamines, piperidine, piperazine, diazine, Pyridine, quinolines, picolines etc. If mercaptans are to be oxidized, the alkaline treatment solution consist of aqueous alkaline hydroxide solutions, which, if desired, can contain solubility promoters for mercaptans.

Solubility promoters promote the solubility of sulfhydrils in aqueous alkaline solutions. Suitable solubility promoters are, for example, lower, monohydric and polyhydric alkanols, lower aliphatic polyamines, alkanolamines, oxy or amino ethers, fatty acids with 2 to 6 carbon atoms, naphthenic acids and aliphatic dicarboxylic acids with 5 to II carbon atoms, phenols with up to 15 carbon atoms, etc. The preferred Solubility promoters are fatty acids with 3 to 5 carbon atoms and phenols.

A preferred method of oxidizing sulfhydrils to neutral Sulfur substances consist in simply blowing air through them at temperatures between about 15 and g5 °, preferably not above 65 °.

Neutral sulfur substances, which are produced by the oxidation of the sulfhydrils are, for example, free sulfur (oxidized from hydrogen sulfide) and organic disulfides (oxidized from mercaptans, mercaptides and thiophenols), which form solid or liquid precipitates in aqueous and alkaline solutions. These precipitates can easily be removed by decanting, settling, filtering or the like. The rate of deposition of sulfur substances in aqueous, consumed Solutions can be increased by diluting. In certain alkaline solutions, for Example those that contain a solubilizer that have a high content of organic constituents, organic disulfides can be quite soluble so that they can be treated with suitable solvents, such as liquid hydrocarbons, need to be extracted.

When the hydroxyl form of the catalyst is weak even in the process is oxidized, the quinone analogs formed are replaced by the sulfhydrils slightly reduced to their original form. So long in the aqueous treatment solution a considerable amount of mercaptan sulfur or of inorganic sulphide sulfur is present, most of the catalyst is not continuously oxidized. But when If the content of such sulfur falls very sharply, the oxidation of the catalyst begins beyond the quinone stage. To prevent this from happening, a protective amount of this must be used Kind of sulfur can be left in the treatment solution, taking the protection required minimum content varies depending on the nature of the catalyst. An easy one oxidizable catalyst requires a relatively large amount of this type of Sulfur, while a more permanent catalyst, can be obtained from a smaller amount is effectively protected. The catalysts according to the invention generally require no more than about 0.1 to 0.2 weight percent mercaptan sulfur to make them protection.

The remaining mercaptan sulfur in the regenerated treatment solution determines their so-called transfer value, d. H. the amount of mercaptan which is present in a hydrocarbon distillate is transferred when this is in contact with the regenerated treatment solution brings. If the transfer value is too high, the hydrocarbon distillate cannot be deacidified by extraction with regenerated solution, so it is essential that that the remaining mercaptan sulfur content and the resulting transfer value are as low as possible. The catalyst according to the present invention enables the achievement of a very low transmission value.

The following examples explain the invention in more detail: Example i A sample of a used alkaline solution, which contains 1.5 percent by weight of free NaOH, 0.2 percent by weight of chemically pure tannin and mercaptans extracted from gasoline, was alternately with the help of a fritted gas distributor with carbon dioxide-free air blown at 20 ° and reloaded with new mercaptans made from the same gasoline. After each extraction and each oxidation, the percentage of inorganic sulphide sulfur and mercaptan sulfur was determined. Number of weight Ahead- gone treatment percent percent Treat- sulfide- mercaptan lungs sulfur sulfur o Loaded with RSH .............. o, 6o 0.77 Blown with air for 2 hours .... 0.43 0.00 2 reloaded with RSH ....... 0.27 i, oi Blown with air for 4 hours .... 0.15 0.00 6 reloaded with R SH ....... 0.00 1.03 Blown with air for 12 hours ... 0.00 0.00 The total time of blowing was 52 hours. A mercaptan sulfur content of zero was achieved seven times. At the end of this treatment period the catalyst still had some effectiveness. Example 2 Some samples of sodium hydroxide solution used in the treatment of gasoline containing sulfur were each treated and tested as listed below. Added o weight weight Na catalyst air blown through / o OH percent percent in solution sulfide mercaptan in percent by weight temperature I duration sulfur sulfur no ................ not o, 67 # o, 6o 0.77 no ..., .......... 27 ° 16 hours i, ig- 0.37 0.35 0.20 / () Quebracho- tannin ........ 50 ° 4 hours 1.63 0.51 0.00 o, i ° / o Quebracho- tannin ........ 27 ° 5.5 hours - - 0.0o 0.1l) /, pyrogallol ..... 50 ° 2 hours - 0.40 0.00 o, i ° / o pyrogallol ..... 27 ° 5 hours - 0.44 0.00 The increase in the NaOH content is due to the conversion of sodium mercaptides to disulfides and free alkali.

Example 3 An approximately 5 weight percent aqueous, alkaline solution of pure Nag S - 9 Hz O, which contains less than 1 percent by weight of pyrogallol as an oxidation catalyst was blown with air at about 27 ° for about 4 hours. The blown solution was then examined and found to be sodium thiosulfate, various Thionates and a trace of sodium sulfite, but practically no sodium sulfide or sodium sulfate contained.

A sodium disulfide solution was prepared in a similar manner in the presence of Pyrogallol treated, with proportionally more sodium thiosulphate was formed.

Hydroquinone, resorcinol, tannin and lignin were also in one Sodium sulfide solution as an oxidation catalyst with a similar result with formation used by sodium thiosulfate. Tannin was found to be more effective when the solution heated to about 65 ° while blowing air.

Example 4 A sample of an aqueous sodium hydroxide solution which had been contaminated by treating a sulfur-containing gasoline with the final boiling point of 93 ° was mixed with 0.24 percent by weight of pyrogallol and blown with air at room temperature. The investigation gave the following results Duration of weight percent weight percent Bubble mercaptan sulfur sulphide bug none ........ 1.24 135 1/2 hour .. 0.00 o, io i1 / 2 hours. . 0.00 0.07 2 hours . . 0.00 0.00 Example 5 A sample of an aqueous sodium hydroxide solution which had been consumed by treating a sulfur-containing gasoline with a final boiling point of 93 ° was mixed with 0.38 % by weight of pure tannin and blown with air at about 82 °. Examination result: Duration of weight percent weight percent Bubble mercaptan sulfur sulfide sulfur none ........ 1,, 83 0.89 1/2 hour .... less than 0.05 0.0 Example 6 An aqueous solution of Nag S-9 H20 (30 g per liter), which contained o.20 /, hydroquinone, was blown with air for 1/2 hour at temperatures between about 65 and 82 °. As a result, it was found to be practically free from sulfide sulfur.

Example 7 An approximately 5 percent by weight pure, aqueous sodium hydroxide solution containing 0.4 percent by weight n-butyl mercaptan was mixed with 0.3 percent by weight pyrogallol and blown with air at room temperature for 1/2 hour. The investigation revealed; that it then contained less than 1/10 percent by weight n-butyl mercaptan.

Example 8 Two samples of an aqueous sodium hydroxide solution which had been consumed by treating gasoline containing sulfur were each mixed with 0.3% by weight of the tannins given below and blown with air at about 65 ° for 21/2 hours. The investigation resulted in the following values: Tannin weight percent weight percent Mercaptan sulfur Sulphide sulfur none (unbleached this solution) o, 8o 1.00 chemically pure Tannic acid 0.00 0.00 hydrolyzed Quebracho- extract .... 0.4 0.51, Example 9 A sample of an aqueous sodium hydroxide solution which had been consumed by treating a sulfur-containing butane butylene fraction was brought to a specific gravity of 34.4 ° B6 by adding an aqueous sodium hydroxide solution of 40 ° B6, then mixed with 0.24% by weight of pyrogallol and blown with air at room temperature. The investigation revealed: Duration of weight percent weight percent Bubble mercaptan sulfur sulfidsch-, vefel none ........ 1.83 0.89 1 / z hour .... o, o6 0.49 i hour .... 0.00 0.36 Example 10 A sample of an aqueous sodium hydroxide solution which had been consumed by treating a sulfur-containing gasoline produced by cracking with the final boiling point 93 ° and which contained 1.36 percent by weight of NaOH, 1.35 percent by weight of mercaptan sulfur and 1.45 percent by weight of sulfide sulfur, - was rated 0 , 24 weight percent pyrogallol mixed and blown with air at room temperature for 4 hours. When the blown solution was examined, it was found to be virtually free of mercaptan and sulfide sulfur.

Example ii Some small bottles were filled about halfway with a clear sodium hydroxide solution which had been consumed by treating a sulfur-containing gasoline with a final boiling point of 93 °. The bottles were shaken vigorously for about 15 seconds in the presence of less than 1 percent by weight of the catalysts listed in the table below. They were then allowed to sit down for about an hour. The following results were found Catalyst I appearance Pyrogallol ..... Formation of an oily top film layer of insoluble organic cic disulfides Hydroquinone ... Pyrocatechol .. the same. chemically pure Tannic acid. the same Resorcinol ...... only very little reaction solid- to deliver By using catalysts of the type described above, many advantages are achieved in the regeneration of the aforementioned spent alkaline treatment solutions. Some of these advantages reside in the high effectiveness and high stability of the catalysts, whereby an efficient oxidation of the sulfhydrils is brought about at relatively low temperatures, whereby the amount of heat required to be supplied, if any, is reduced and the corrosion of the equipment is reduced. Since the process is simple, effective and easy to carry out, the cost of the equipment and the amount of chemicals required to operate it are relatively low. Another advantage is that the catalysts described are themselves solubilizers for mercaptans. Another advantage can be seen in the fact that a gasoline which has been deacidified with an alkaline treatment solution which has been regenerated according to the method according to the present invention has an increased lead sensitivity and a low mercaptan sulfur content.

Claims (3)

PATENT CLAIMS: i. Process for the slow oxidation of sulfur compounds, in which other compounds than the normal oxides are formed, especially the slow ones Oxidation of hydrocarbons obtained from the extraction of sulphurous hydrocarbons Solutions of sulfhydrils, characterized in that the sulfur compounds in alkaline solution in the presence of a mononuclear or polynuclear catalyst acting as a catalyst aromatic Compound which contains several hydroxyl groups bound to the core or the cores, a corresponding quinone or tannin, the catalyst being a higher Must have oxidation potential than the sulfur compound to be oxidized, by means of an oxygen-containing gas, expediently air, in particular by introducing a such gas are slowly oxidized. 2. The method according to claim r, characterized in that that a mercaptan is subjected to oxidation. 3. The method according to claim z or 2, characterized in that the amount of the catalyst is o, z to 5, preferably 0.5 to 3 percent by weight of the alkaline solution. q .. Process for regenerating used, aqueous alkaline solutions which contain hydrosulfides extracted from sulfur-containing hydrocarbons, characterized in that the used solution is in the presence of a small amount of a mononuclear or polynuclear aromatic compound which binds several hydroxyl groups to the core or the cores contains or a corresponding quinone or is oxidized by tannin as an oxidation catalyst in order to convert the hydrosulfides mentioned into neutral sulfur substances.