DE1162018B - Process for the regeneration of aqueous alkali hydroxide solutions that were used in the refining of sulfur-containing hydrocarbon mixtures - Google Patents

Description

Process for the regeneration of aqueous alkali metal hydroxide solutions which were used in the refining of sulfur-containing hydrocarbon mixtures The invention relates to a method for the regeneration of aqueous alkali hydroxide solutions, which were used in the refining of sulfur-containing hydrocarbon mixtures.

It is known to remove acidic impurities, for example sulfur compounds, by extraction with sodium hydroxide or potassium hydroxide solutions from hydrocarbons, such as acidic gasolines including cracked gasoline, heavy gasoline, jet fuel, luminous oil, lubricating oil, gas oil and normally gaseous fractions. In general, aqueous solutions containing from about 5 to about 50 percent by weight of alkali metal hydroxide are used, and solubilizers such as alcohols, phenols, cresols or butyric acid can optionally be added to the solution.

The extraction of the acidic constituents takes place in such a way that the Hydrocarbon initially brought into intimate contact with the alkaline solution and then separating the treated hydrocarbon from the alkaline solution will. As a rule, the alkaline solution is then regenerated.

The used alkaline solutions are regenerated in usually by evaporation at high temperature or by oxidation with air or other gas containing free oxygen. Both measures are costly and unsatisfactory. The catalysts used for regeneration with air decomposed more or less quickly.

It has been found that phthaloeyanine catalysts are very stable. According to the invention, used alkali hydroxide solutions that are used in refining sulfur-containing hydrocarbon mixtures were used, thereby regenerated, that the sulfur-containing compounds dissolved in these alkaline solutions with a free oxygen-containing gas, preferably air, in the presence of a phthalocyanine catalyst oxidized. Both metal-free phthalocyanines and metal phthalocyanines are effective and stable catalysts, the latter being preferred.

The use of a phthalocyanine has proven to be particularly expedient proven to contain at least one of the metals cobalt, vanadium, iron or copper. But also other metal phthalocyanines, such as magnesium, zinc, titanium, hafnium, Thorium, tin, lead, niobium, tantalum, antimony, bismuth, chromium, molybdenum, nickel, Palladium, platinum, silver and mercury phthalocyanine are suitable. The metal phthalocyanines can be used alone or in admixture with one another.

Since the phthalocyanines themselves are generally alkaline in water Solutions are sparingly soluble, it is advisable to use soluble derivatives thereof, z. B. Metallphthaloeyaninsulfate or carboxylates, with the cobalt in particular and preserve the vanadium phthalocyanine sulfonate.

The phthalocyanines can be used as such or on a solid support applied. Sometimes the carrier can also have a catalytic effect. The carrier can be made of charcoal.

The phthaloeyanine compound can be applied to the carrier in solution will; suitable solvents are methanol, ethanol, propanol, butanol, acetone, Methyl ethyl ketone, diethyl ether and diethyl ether.

The used alkali metal hydroxide solution can be regenerated batchwise or continuously. In continuous processes, the solution with air or oxygen is continuously introduced into a regeneration zone which contains the phthalocyanine catalyst or into which the phthalocyanine catalyst is also introduced. The amount of catalyst depends on the concentration of the acidic impurities and can be 0.0001 to 200 / or more, based on the solution used. The regeneration can take place at normal or higher temperatures, but not above 95 ° C. The mercaptides are oxidized to disulfides. These can then by skimming or by extraction with a suitable solvent, e.g. B. mineral spirits are removed. The disulfides can also be extracted with the fresh hydrocarbon treated with the regenerated alkali hydroxide solution. The regenerated alkali hydroxide solution is withdrawn from the regeneration zone and returned continuously or in batches to the treatment zone. Carrier particles interfere in the hydrocarbon distillate, which is why the regenerated alkali metal hydroxide solution has to be filtered or decanted. The used alkali metal hydroxide solution can also be passed over a fixed support bed of coke. If the catalyst is used in solution as phthaloeyanine sulfate, it can be dissolved and kept in solution in an amount of 0.0001 to 5 percent by weight in the alkali metal hydroxide solution. The solution is circulated through both the treatment and regeneration zones.

The metal phthalocyanines are stable and do not give the metal free. They differ significantly from the metal helates that are found among the Decompose regeneration conditions releasing metals.

A liquid which is immiscible with this and is able to dissolve organic disulfides can also be added to the alkali hydroxide solution. Petroleum fractions to be treated often contain thiophenol, which is absorbed by the alkali hydroxide solution. The oxidation of thiophenol on the surface of the solid catalyst leads to the formation of solid diphenyl sulfide, which occludes the catalyst and reduces its activity. By adding a small amount of a hydrocarbon to the alkali hydroxide solution, the diphenyl disulfide is dissolved and the catalyst is made active again. When the regenerated alkali hydroxide solution has settled, the oil is poured off.

The following examples illustrate the process of the invention.

Example 1 By mixing liquid n-butyl mereaptane with 50% strength aqueous potassium hydroxide solution, an approximately 0.4 percent strength by weight mereaptane solution (calculated as - SH) was prepared. 0.01 mol of copper phthaloeyanine disulfonate per liter of potassium hydroxide-mercaptan solution was then added to the solution.

The alkaline solution containing mercaptan and phthalocyanine and a comparison solution without phthaloeyanine were then vigorously stirred in open air. The amount of mercaptan still present in each solution was determined after fixed contact times by titration with silver nitrate solution and are given in the following table: Table 1 ', Residual mercaptan Time in minutes reference solution solution 1 with copper phthalo- without phthaloeyanine 1 cyanine disulfonate 0 100 100 10 84 43 20 77 21 30 65 4 Example 2 The experiment given in Example 1 was repeated, except that a 300% strength potassium hydroxide solution was used. The results obtained are shown in the following table: Table 11 Residual mercaptan i solution Time in minutes for comparison solution without phthalocyanine with copper phthalo- cyanine disulfonate 0 100 IN 10 98 77 20 95 42 30 89 21 Example 3 The catalyst used in this example consisted of iron phthalocyanine on a carbon support. The experiment was repeated as described in Example 1 , but the effectiveness of the catalyst was tested in four different solutions which contained various acidic sulfur compounds, namely n-butyl mercaptan, sec-butyl mercaptan, thiophenol and hydrogen sulfide. The test solutions were prepared by adding the sulfur compounds to 200 cms of aqueous KOH solutions (5 to 120%). The catalyst contained 0.02% iron phthalocyanine on charcoal and was prepared by evaporating a 0.10% iron phthaloeyanine solution in methanol with an appropriate amount of charcoal on a steam bath. The catalyst was added to the solutions in an amount of 0.1 % by weight , which corresponds to a concentration of 0.2 parts of iron per 1 million parts of solution. The results of these tests are compiled in the following table. Again, the amounts of mercaptan-sulfur determined after the treatment are given (0 /, RSH). A stands for comparison solution and B solution containing catalyst. Table III solution 2 1 3 4 KOH Time in minutes 5 070 5010 1 4 " o 1201! O Sulfur compound n-butylmereaptane sec.-butylmereaptane 'miophenol hydrogen sulfide (0.3 "(o) (0.3% (0.3%) (0, lol, '0) A B A A B A B 0 100 100 100 100 100 100 100 100 15 100 47 68 7, 5 100 66 100 59 30 87 4 45 0 100 55 WO 22 Example 4 In this example, commercial cobalt phthaloeyanine disulfonate was used to regenerate 100% sodium hydroxide solutions which contained various sulfur compounds. In each case 200 cm3 of solution were vigorously stirred in the presence of air at 25 ° C. as in the earlier examples. A again denotes the comparison solutions and B denotes the solutions containing the catalyst. The catalyst concentration in the solutions was 1 ppm in the case of the n-butyl mercaptan-containing solution and 10 ppm in the case of the other solutions. Table IV Sulfur compound Time in n-butyl tert-butyl thio sulfur Minutes mercaptan mercaptan phenoi hydrogen (0.30 / 0) (0.3%) (0.30 / 0) (0.10 / 0) A 1 B A 1 BB IB 5 95 80 90 50 83 10 90 69 77 24 0 73 15 86 60 66 14 65 30 71 36 36 0 40 50 10 10 10 Example 5 This example compares the effectiveness of cobalt phthalocyanine with a known catalyst, namely cobalt disalicylalethylenediamine. A 100% sodium hydroxide solution was used which contained 0.2 percent by weight of n-butyl mercaptan. The cobalt phthalocyanine dissolved in the sodium hydroxide solution easily in a concentration of 50 parts per 1 million parts of solution without formation of a precipitate on. When the cobalt disalieylalethylelidiamine was added to a 100% strength sodium hydroxide solution containing 0.2 percent by weight of n-butylmereaptane, a red precipitate separated out which, as an analysis showed, contained cobalt. The same precipitate was formed when the mereaptane was added to the solution after the catalyst had dissolved. The stability of the metal phthalocyanine results from this.

Each catalyst was then introduced into a concentration of 50 parts per 1 million parts of solution in various portions of a 100 / sodium hydroxide solution containing 0.12 percent by weight of n-butyl mercaptan, and each solution was then intimately contacted at ambient temperature in contact with air. The sample containing cobalt phthaloeyanine turned sweet after 4 minutes . H. free of mercaptary sulfur. The sample containing cobalt disalicylethylenediamine had to be treated for more than 140 minutes to become sweet.

Example 6 In this example, a cobalt phthalocyanine catalyst and a metal-free phthalocyanine catalyst were compared. The metal-free catalyst was prepared by dissolving a commercially available metal-free phthalocyanine powder in methanol, adding charcoal to the mixture and evaporating to deposit the phthalocyanine on the charcoal. The finished catalyst contained 2.2 percent by weight phthalocyanine. The second catalyst containing 2.5 weight percent cobalt phthalocyanine on charcoal was prepared in the same way. These catalysts were each added in such amounts to 200 cm3 of a 100% sodium hydroxide solution that the concentration was 250 parts of phthalocyanine per 1 million parts of solution. Each solution was then shaken at room temperature with 500 cc of a jet fuel containing 0.049 weight percent mercaptan sulfur. Samples were taken and analyzed at various time intervals. The following results were obtained: Table V catalyst Time in minutes. Cobalt phthalomethane-free cyanine phthalocyanine 0 /, RSH 0 0.049 0.049 5 0.012 6 0.015 12 0.008 15 0.004 20 0.003 30 0.002 A control experiment without a catalyst showed practically no reduction in the mercaptan sulfur content.

Example 7 The used sodium hydroxide solution used in this example had a specific gravity of 1.151 at 15 ° C. and contained 2.84 percent by weight of mercaptan sulfur, 14.2 percent by weight of total phenols and 8.5 percent by weight of thiophenols.

Different amounts of this solution were passed per unit time with different amounts of air at 66 ° C. under 7.8 atmospheric pressure in an upflow over a layer of 100 ml (15 g) of a supported cobalt phthaloeyanine monosulfonate catalyst. The catalyst was prepared by impregnating 15 g of charcoal with an aqueous solution containing 0.15 g of cobalt phthalocyanine monosulfonate and then drying. The following table VI shows the dependence of the decrease in the mercaptan sulfur content on the feed rate and the amount of air supplied, which were continuously changed. Table VI Flow multiple Experimental speed- "/ 0 mercaptand stoichio- duration in 1, -eit of the sulfur metric Hour solution lack of air in nil / hour 1 100 0.2232 2.0 2 100 0.7533 2.0 3 100 1.0602 2.0 4 100 1.0423 2.0 Table VI (continued) Flow multiple Test speed 0.19 mercaptander stoichio- duration of the sulfur metric Hour solution air volume in ml / hour 5 66 0.7812 3.1 6 66 0.6975 3.1 7 50 0.1535 4.1 8 30 0.0837 6.8 9 55 0.3348 3.7 10 60 0.3348 3.4 11 50 0.2232 4.1 12 22 <0.00279 9.3 14 25 0.00140 8.2 20 28 0.00140 7.3 30 25 0.00140 8.2 34 25 0.00250 8.2 36 25 0.00250 8.2 42 25 0.00194 8.2 EXAMPLE 8 The spent caustic solution used in this example was derived from a petroleum refinery (specific gravity 1.13 at 15'c) had a content of 11, 1 percent by weight NaOH, an inorganic sulphide content of 2.81 weight percent sulfur, a Mercaptidgehalt of 0, 83 percent by weight sulfur, a content of 7.6 percent by weight of total phenols and about 1.7 percent by weight of thiophenols.

Using the catalyst described in Example 7 , 150 ml of spent caustic soda solution and 21 to 36 liters of air per hour were passed upwards through 150 ml of supported catalyst which was kept at room temperature and air pressure. The results obtained with a flow rate of the caustic soda solution as the hourly liquid space velocity equal to 1 show in Table VII, inter alia, the partial oxidation of the sodium sulfide. Table VII Total air over- l`O Na, S "1" Mer- Trial hours shot times as captan color No. in stoich. Sulfur sulfur Testing crowd 1 0.33 1.0 0.44 0.14 dark blue 2 0.67 1.0 1.1 0.23 dark blue 3 1.00 1.0 1.2 0.31 Light blue 4 1.33 1.0 1.2 0.42 Light blue 5 3.33 1.7 0.85 * - Green-gray 6 4.50 1.7 0.98 0.22 Green-gray 7 5.25 1.7 1.1 0.17 Green-gray * Probably in the form of sodium polysulfide. Tests carried out in a similar manner at 66 ° C. and 2.7 atm pressure in the presence of the same cobalt phthaloeyanine monosulfonate charcoal catalyst, in which 50 and 100 ml of the same spent caustic liquor per hour and 9.78 liters of air per hour were passed through 100 ml of catalyst, led to the results given in Table VIII. Table VIII Total flow room air flow hour speed- shot times 0/0 Na2S 0 / " Mer- Verkeit the Schwinstöch. as S captan search solution amount of sulfur * duration in ml / hour 0.5 100 1.0 0.68 1.36 0.28 1 100 1.0 0.68 1.39 0.68 1.5 100 1.0 0.68 1.83 0.73 2 100 1.0 0.68 2.01 0.75 3 50 0.5 1.3 1.69 0.73 4 50 0.5 1.3 1.75 0.68 5 50 0.5 1.3 1.42 0.62 9 50 0.5 1.3 1.50 0.68 21 50 0.5 1.3 1.70 0.68 * Probably in the form of sodium polysulfide. Example 9 A part of the same used caustic soda solution as in Example 8 was blown through at 90 ° C. in the presence of 25 and 50 parts per million cobalt phthaloxyanine disulfonate. The results shown in Table IX were obtained.

Table IX Oxidation of spent caustic soda solution at 90 ° C. Apparatus: Three-necked alkylation flask equipped with a water-cooled reflux condenser, thermometer, heating mantle and porous glass distribution tube for air. Cobalt phthaloeyanine disulfonate Hours at 25 ppm 50 ppm Experiment 0 / " Wet Mercaptan- % Na, S, 0 /" Mer- as sulfur as S captan- sulfur initially 2.81 0.83 2.81 8.83 1.2 268 0.60 2.35 0.77 2.5 1:86 0.74 2.12 0.68 4.0 1.38 0.65 0.85 0.45 5.5 1.10 0.54 0.30 0.51 6.0 - - 0.17 0.34 7.0 0.58 0.48 0.0 0, lo * 830 0.20 9.0 0.0 <0.006 10.5 0.0 <0.006 This material showed the following analytical data: Liquid portion (approx. 99 %, sample). 3.3 percent by weight Na, .S.0, as sulfur. <0.1 percent by weight Na2S0, as sulfur 3.2 %, total phenols (U.V. ). 0.040 / " thiophenols (U.V. ). Solids (about 10/0 of the sample) contained 29.04 0 / " Sulfur.

Claims (2)

Claims: 1. A process for the regeneration of aqueous alkali hydroxide solutions which were used in the refining of sulfur-containing hydrocarbon mixtures, characterized in that the sulfur-containing compounds dissolved in these alkali lyes are oxidized with a free oxygen-containing gas, preferably air, in the presence of a phthalocyanine catalyst. 2. The method according to claim 1, characterized in that the phthalocyanine catalyst consists of a metal phthalocyanine and contains at least one of the metals cobalt, vanadium, iron and copper. 3. The method according to claim 2, characterized in that the catalyst consists of a metal phthalocyanine sulfonate or carboxylate, such as cobalt or vanadium phthaloeyanine disulfonate. 4. The method according to claim 1 to 3, characterized in that the phthalocyanine catalyst is applied to a solid support such as charcoal. Documents considered: German Patent No. 1 041 960; Ber. d. D. Chem. Ges., Vol. 72, 1939, S. Ilff .; Nature, Vol. 149, 1942, p. 602, r. Sp .; Journ. of the Chem. Soc. (London), 1938, pp. 1774ff .; K arrer, apprentice d. Organ. Chemie, 13th edition, 1959, p. 846.