DE1667763A1 - Process for the oxidation of soluble sulphide compounds - Google Patents

Description

The invention relates to a process for the catalytic conversion of a soluble sulfide compound to a higher oxidation state, such as elemental sulfur, sulfite, biaulfite, ") ithionate, thiosulfate, sulfate or the like. In particular, the invention relates to a catalytic process in which controlled amounts of oxygen be used in conjunction with a solid T.Ifjtallsulf Ldkatalyaator to a transformer ■ vi.orung in the OxydationsatuCe a soluble SuIEndverbindung • / .n effect. an important aspect of eggs invention is to thee Gewinn'r.f ^r "'u element -rern sulfur from a solution which contains a sulphide compound. Another important face

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bath

point involves treating a solution of a sulfide compound, like a waste water flow generated in the course of a chemical process to meet its biological oxygen demand reduce so that he can safely enter Streams or 'receiving waters can be drained.

Part of the cost of a modern industrial society are to be paid, concern the large amounts of solution of sulphide compounds which are obtained from various industrial sources arise and need to be eliminated. In particular, aqueous solutions with hydrogen sulfide are undesirable By-product of many economically important industrial processes in the chemical, petrochemical and steel industries. For example, in the petroleum industry, large quantities of sulphide solutions are obtained by processes such as hydrofining, Hydrocracking, reforming and the like. Indeed, a common feature of all these processes is that they produce a petroleum fraction, a shale oil, process a coal tar oil or the like that inevitably

contain at least trace amounts of organic sulfur compounds. In the course of these processes, these organic sulfur compounds are generally converted into hydrogen sulfide and converted to corresponding hydrocarbons. To a large extent, these are aqueous alkaline solutions ^ and their elimination is due to their possible biological oxygen demand due to the presence of sulfide ions poses a problem. In one pail of particular interest, namely hydrofining of petroleum distillates, large quantities are used

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Ammonia and hydrogen sulfide are generated and these are generally absorbed in an aqueous solution which is withdrawn from the proceedings. In a similar way, the treatment of natural gas with a suitable scrubbing liquid leads to like monoethanolamine also to a sulphide solution «,

This sulfide compound in these solutions is generally found as a salt of a strong base, such as ammonium sulfide, Sodium sulfide, potassium sulfide and the like suggest that too can be ionized to various degrees. In addition, the sulfide compound may be in the same kind of polar association present, which characterizes, for example, hydrogen sulfide solutions in bioethanolamine. In this regard, it is important to remember that hydrogen sulphide, because of its polar nature, is to a certain extent even in aqueous solutions Absence of a suitable solubility-increasing agent is soluble · At 20 ° and 1 ata, for example Dissolve about 2.5 ml of hydrogen sulfide (as vapor) in 1 ml of water.

It is understandable, therefore, that in recent years attention has been paid to means for converting these sulfide compounds has been directed in forms that have a lower oxygen requirement and, if necessary, too in a form that has significant economic value. There has now been a method of converting this Sulphide compounds either in valuable elemental sulfur, if desired, or instead in sulfur compounds

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found of decreased oxygen demands so that they can be drained into receiving waters and streams when sulfur production is not economically viable.

Accordingly, the invention aims to provide a process for the production of elemental sulfur from a Solution of a sulfide compound. A simultaneous task is to reduce the biological oxygen demand an aqueous solution of a sulphide compound and also in the purification of sulphide-containing wastewater streams, see above that they can be reused if desired.

Yet another general objective is regulation or Preventing water pollution from the chemical, petrochemical and similar industries.

Accordingly, the invention provides a method for oxidizing a soluble sulfur compound which consists in that a solution of the sulfide compound with an oxygen-containing Gas in the presence of a solid catalyst consisting of the sulphides of nickel, iron and cobalt or mixtures treated from this »

In a preferred embodiment of the invention, a aqueous ammoniacal hydrogen sulfide solution thereby oxidized that they with an oxygen-containing gas in Presence of a solid nickel sulfide catalyst in

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_ 5 Association treated with alumina »

There is a particular advantage of the invention in the fact that ea works in a liquid phase. This allows processing on the streams that are generally due industrial processes of the type mentioned above are available. Also, this feature makes it easier if necessary the recovery of sulfur.

As has already been mentioned, the solution to be introduced into the method according to the invention contains a suIf! Compound. This solution can come from any industrial plant such as chemical plants, sewage treatment plants and the like. The solvent used can be water, alcohol, or any other suitable organic solvent. The solution is expediently aqueous and as such is usually referred to as wastewater. In some cases it is advisable to convert the sulphide compound contained in the waste water into the corresponding sulphite, thiosulphate, sulphate, dithionate, etc., which have a lower oxygen requirement because of their more highly oxidized state. On the other hand, it can be useful to convert the sulphide into elemental sulfur. In any case, the invention can bring about the desired transformation. Furthermore, the sulfide compound is generally present in small concentrations of, for example, less than 5% by weight of the solution, although the invention can just as well process a solution having a high sulfide concentration. aside from that

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the solution usually contains other ingredients that increase the solubility of the sulfide in the solution. Examples include ammonia, metal salts of weak acids such as sodium carbonate, ITatriumphosphat and the like, organic bases such as methylamine, iithylamin, A ^J thanolamin, propanolamine and the like and other substances known in the art. As mentioned above, a particularly important class of solutions consists of ammoniacal aqueous solutions of hydrogen sulphide.

Another essential reaction component for the present process is oxygen. This can be present in any suitable manner, either alone or in admixture with other gases in any suitable amount. In the embodiment of the invention in which elemental sulfur is to be produced, oxygen is preferably used in approximately the stoichiometric amount required to carry out this conversion, ie from about 0.25 to about 1 mole of oxygen per mole of sulfide. If instead it is desirable to reduce the oxygen demand of the solution to allow around its discharge into streams of oxygen is preferably in an excess amount over the stoichiometric M _e length for the conversion of sulfide to sulfate before, that is, in an amount greater than about 2, 0 moles of oxygen per mole of sulfide.

Another advantageous feature of the invention is the use of the catalyst in solid form. This allows one Operation without the problem of catalyst recovery »

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like it in general "when working with a soluble Catalyst occurs.

As indicated above, the present method is in the present case insoluble metal sulfide. The metal consists of nickel, cobalt or iron, with nickel being preferred. Mixtures of these sulfides can also be used be used.

While it is possible to practice the invention with a catalyst layer of the solid metal sulfide as such, it is preferred to combine the metal sulfide with a suitable support material. Examples are active coals such as charcoal, bone charcoal or the like, which can be activated before use, alumina, silica, zirconium oxide, diatomite, bauxite, carbon in various forms and other natural or artificial highly porous inorganic carrier material. Alumina and activated carbon are preferred. Nickel sulphide mi * in association with clay or with activated carbon is therefore particularly preferred catalysts are.

For association of the metal sulfide with the carrier can apply suitable measures such as impregnation of the support by immersion in a solution of a soluble S _a lzes the desired metal component, subsequent Wasdung and drying. The me-

C.

The metal constituent can then be treated with hydrogen sulphide, preferably converted to the sulfide at room temperature will. Instead, the salt form can also be used in the

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part of the process cycle can be converted to sulphide. In some cases it can be useful to calcine the impregnated support material prior to sulphidation.

When the metal sulfide is combined with a carrier material, the amount by weight of the metal compound can be calculated as the sulfide is generally in a range up to 60 ^c ß> M or more of the total are _a te. In general, however, it is preferred to work in the range from about 10 to 40% by weight of the total mass.

The method of the invention can be carried out in a suitable manner, e.g.

operated in single batches or continuously.

A particularly preferred method uses a fixed one Layer of catalyst in an oxidation zone. Desxilfid containing Solution is then passed through, upstream or downstream, and the oxygen is either in countercurrent or in cocurrent guided.

YJenn the method according to the invention ζιτ generation essential Yields of elemental sulfur is operated, the sulfur from the outlet from the oxidation zone can be more suitable Manner, e.g., filtration, centrifugation, settling, or other known means for removing solid particles from a Liquid are separated. If desired, the outlet from the oxidation zone can be in a sulfur settling basin be conducted at a sufficiently high temperature

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(As is known, sulfur melts at about 112 ⁰ G), so that the sulfur agglomerates and is then removed by simply draining off a separate immiscible liquid sulfur phase.

In some situations it may be useful to carry out the invention in multiple stages in order to achieve a complete To effect sulfide conversion. For example, it can be useful to operate the first stage in such a controlled manner that that sulfur is produced, the effluent from the first stage being fed to a second stage after the sulfur has been separated off which is designed in such a way that the remaining sulfide is oxidized into sulfate, in order in this way to this outlet in To be able to discharge currents or positive flows. It should also be noted that that in some cases the practically sulfide-free discharge from the process of the invention into the industrial process can be deflected back from where it came in order to use it further.

The process of the invention is carried out at a suitable temperature which can range from ambient up to about 200 ° 0 or more. When the method for producing elemental sulfur is operated, one works preferably in the range of about 0 to about 100 ⁰ O. other hand, when the process is operated for the production of sulphate, is carried out preferably in a range of about 100 to 200 ⁰ O.

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The pressure applied should be chosen so that the sulphide solution is kept in a liquid state. In general, it is preferable to operate at overpressure and a pressure of about 1.7 Ms 10.2 atm is particularly suitable.

The liquid space velocity, defined as per hour attached space part of the sulfide solution divided by the total volume of the catalyst in the oxidation one, is located preferably in the range of about 0.5 to 4.0.

The catalyst layer used in the invention can be discarded if it becomes contaminated with adsorbed elemental sulfur clogged or it can be regenerated by suitable methods known per se. Examples for this are: Burning off at an elevated temperature with oxygen and subsequent reduction in hydrogen} Heating of the layer in an inert atmosphere at sulfur evaporation temperature and subsequent stripping of the rock with an inert gas, Use of a desorbent to remove the sulfur

The following examples serve to further illustrate the novelty, operation, and utility of the invention, without to limit them to the flow sheet, the working conditions and the types of catalyst used, because these should serve for explanation only.

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example 1

An alumina carrier was made by adding alumina hydrosol dripped into an oil bath using a nozzle or rotating disk. The usual aging, drying and calcining -treatment, the carrier was treated with an ITickelnitral solution in a !! close soaked, which leads to a finished M & sse with 20 G-ew .- $ Nickel led. After drying, the impregnated carrier was heated to about 427 ° 0 in a stream of air for two hours to decompose the kitrat. The mass obtained was then sulfided by flowing a stream of hydrogen sulfide conducted over it at room temperature.

100 · cm of the catalyst obtained was inserted into a reaction zone: an aqueous Z _u laufatrom 1.67 wt .- ^ Ammoniai and 2.5 wt .- $ sulfide and oxygen in a ratio of 0.5 moles per mole of sulfide were then brought into contact with the catalyst in the reaction zone. The zone was maintained at an inlet pressure of approximately 3.9 atmospheres throughout the experiment. The inlet rate was maintained at approximately 100 ml per hour during the duration of the experiment so that the liquid space velocity was adjusted to about 1.0. The experiment was continued over a period of 20 hours and was divided into a series of 4 run-out periods and test periods designed to examine the rate of oxidation as a function of the reaction temperature. The results were as follows:

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Table 1 Sulfide conversion
. (D selectivity
in Io (2) Attempt no. Temperature in O 84 95 1 35 84 93 2 60 85 77 3 90 75 68 4th 125

(1) based on the sulfide content of an aqueous inlet stream

(2) Percentage by weight of elemental sulfur based on the total converted sulfide.

These experiments demonstrate the ability of the nickel sulfide catalyst to effect the desired conversion of sulfide to higher levels Stages of oxidation. In particular, these results prove that The fact that the nickel sulfide catalyst with an appropriate choice of reaction conditions can be made so that it provides a product rich in elemental sulfur.

Example 2

An alumina carrier, which was manufactured as described in Example 1, was with eiia? Cobalt nitrate solution soaked to a finished To deliver mass with 20 wt .- ^ cobalt. The mass obtained was dried at a temperature of 100.degree. It was then immersed in a sodium carbonate solution. Afterward

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vmrde washed with water, dried at 95 ° C and finally by passing over hydrogen sulfide " Sulfided at room temperature.

The cobalt sulfide-alumina catalyst obtained was' dem subjected to the same evaluation test as in Example 1. The following results for the experiment are based on same basis as in example 1.

Table 2

Experiment no. Temperature in ⁰ O fo sulfide selectivity in

conversion

1 35 65 84 2 60 71 79 3 90 75 73 4th 125 68 59

These results show that cobalt sulfide in _a ge i to effect the desired conversion, but under these conditions does not perform as well as the preferred ITickelsulfid.

Example 3

The alumina carrier produced according to Example 1 was impregnated with a fi'errinitratlösung so that it gave a finished mass with 10 wt .- ^ iron. Then, the resulting mass at 100 ⁰ O was dried. A stream of ammonia gas was then passed over the mass. Finally the masa was washed, dried

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and sulfided in the same manner as described in Example 2,.

The obtained catalyst was subjected to a similar evaluation subjected, as in example 1. The scarfing results on the same basis as above were the following:

Table III

Experiment no. Temperature in ⁰ O <? <> Sulfide selectivity in

conversion

1 35 79 2 60 79 3 90 81 4th 125 73

82 82 82 70

Thus, these results indicate that iron sulfide on alumina is effective for the desired reaction. Under these conditions however, this catalyst is not as effective as the preferred nickel sulfide catalyst of the example

A commercially available activated carbon, known under the name Nuchar WA, was impregnated with a nickel nitrate solution, so that a finished catalyst composition with 63% by weight of nickel, based on the weight of the carbon carrier, was obtained. After drying, the maaae obtained were treated with a stream of ammonia gas and then ^{heated to 95 0} O ^

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to drive off excess ammonia. Then the Catalyst washed with water, dried and sulfided at room temperature.

The obtained catalyst mass was then subjected to the same evaluation test subjected, as indicated in Example 1. The results of the test were as follows:

Table IY

Experiment no. Temperature in ⁰ C <fo sulfide selectivity in ° /

conversion

1 35 93 98 ο 60 93 96 3 90 92 93 4th 125 85 89

These results confirm the unique selectivity of S nickel sulfide for the generation of elemental sulfur and show a long-lasting activity of this catalyst in the oxidation of sulfide.

Example 5 -

This example concerns the embodiment in which the The method according to the invention is used for the oxidation of the sulphide to higher levels beyond the elemental state, so that the need for additional oxygen is reduced and the resulting electricity is safe in rivers and lakes

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can be drained. This is particularly valuable in cases where the amount of sulfide in the solution is too small to be economical Extraction of elemental sulfur is.

D _e r used Mckelsulfid-activated carbon catalyst was the same

3 as in example 4. 100 cm of this catalyst were again used in an oxidation zone. Then a solution of 1.67 wt. -Fo sulfide and 2.35 wt .-? 5 ammonia mixed with such an amount of air in the zone is taken in that the molar ratio of oxygen to sulphide was about 3.5. A pressure of 6.8 atm was used to keep the solution in the liquid phase. Furthermore, the feed was carried out in such a ratio that the liquid space velocity was 1.0.

The experiment was carried out for 12 hours, divided into Outlet periods and test periods. The test results were the following:

Table V

Test No. Duration in'Stunden temperature fo SChv / efelumwandlun

in ⁰ C "in sulphate form (1)

1 3 125 97 2 2 150 100 3 2 150 97

(1) Wt .- # in the outlet in sulphate form

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The above example clearly demonstrates the suitability of the invention For the creation of a drainage stream without a practical one Oxygen demand, which is thus released into rivers, streams and lakes can be.

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Claims (1)

Claims 1. Process for oxidizing a soluble sulfur compound, characterized in that there is a solution of the sulfide compound with an oxygen-containing gas in the presence of a solid catalyst consisting of nickel, iron and / or Treated cobalt sulfide. 2. The method according to claim t, characterized in that the solution consists of an aqueous alkaline solution of the sulfide compound consists. 3. The method according to claim 2, characterized in that the solution consists of an aqueous ammoniacal hydrogen sulfide solution consists. 4. The method according to any one of claims 1 to 3, characterized in that that the metal sulfide is carried on a carrier material is. 5. The method according to claim 4-, characterized in that the Carrier is made of clay. 6. The method according to claim 4, characterized in that the Carrier made of activated carbon ^. - 19 209813/129 5 7. The method according to claim 5, characterized in that the solid catalyst containing nickel sulfide combined with alumina. '8th. Process according to Claim 6, characterized in that the solid catalyst is nickel sulfide in combination with activated carbon contains. 9. The method according to any one of claims 1 "to 8, characterized in that the contact treatment is carried out at a temperature iir. The range from 0 to 200 ⁰ G under änem pressure at which the solution is kept in a liquid state. 10. The method according to any one of claims 1 to S, characterized in that oxygen is brought into contact with the solution in an amount in the range from 0.25 to 1 mole per mole of sulfide in the solution and the sulfide is practically oxidized to elemental sulfur. 11. The method according to claim 10, characterized in that the contact treatment takes place at a temperature in the range from 0 to 100 ⁰ G. Method according to one of Claims 1 to 9 »characterized in that that the solution is treated with oxygen in an amount greater than 2 moles per mole of sulfide in the solution and the sulfide is essentially oxidized to sulfate. 209813/1295 -20- 13. The method according to claim 12, characterized in that the contact treatment takes place at a temperature in the range from 100 to 200 ⁰ G. OFHSiNAL INSPECTED 2 09813/1295