RU2428374C2 - Method of destroying polysulphanes in commercial-grade sulphur - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to chemistry and can be used in gas-processing industry to remove polysulphanes from commercial-grade sulphur. Molten sulphur is fed into aqueous solution of an oxidising agent - 3,5-di-tert-butyl-o-benzoquinone in amount of 0.8 wt %. The polysulphane decomposition process is carried out at temperature 70-90°C. The spent oxidising agent is regenerated in an air current.

EFFECT: invention increases quality of commercial-grade sulphur.

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Description

The invention relates to the field of organic chemistry, in particular to the decomposition of polysulfanes in commercial sulfur obtained by the Claus method, and can be used in the gas processing industry to remove polysulfanes from commercial sulfur and improve its quality.

A known method of removing polysulfanes from gas streams containing hydrogen sulfide, based on the adsorption of polysulfanes on a catalytically active porous material (activated carbon, molecular sieves, alumina, silica gel, modernite), followed by decomposition to hydrogen sulfide and sulfur at a temperature of 130-162 ° C and pressure 1-5 bar [Patent WO 2008087125, 2008].

The disadvantages of this method is the impossibility of its use for the decomposition of polysulfanes in liquid sulfur, a sufficiently high temperature of the process, a significant consumption of adsorbent, the complexity of disposal of spent adsorbent and low environmental friendliness of the process by burning the spent catalyst.

A known method of removing polysulfanes from a gas product mixture in the process of producing hydrogen sulfide from sulfur and hydrogen by passing a gas stream containing from 400 to 1500 ppm through a multi-stage washing system in which the gas stream is in contact with an aqueous or methanol solution of alkali (5-20% wt. ) with the formation of metal polysulfides at a temperature of 10-60 ° C and atmospheric pressure, and then passes the stage of post-treatment on adsorbents (activated carbon or zeolite) [Patent WO 2004028963, 2004]. The degree of removal of polysulfanes in a hydrogen sulfide-containing gas is 99.5%, while the residual amount of polysulfanes does not exceed 10 ppm.

The disadvantages of this method are its use only for the decomposition of polysulfanes contained in the gas phase, significant consumption of alkali and methanol, high operating costs of adsorbents, the complexity of the process of disposal of waste water, methanol-alkaline solutions.

A prototype for the proposed method was not found.

The technical task is to create a new method for the destruction of polysulfanes in commercial sulfur, which provides for the removal of polysulfanes from liquid sulfur, obtained by the Klaus method at the granulation stage, by treating molten sulfur with an aqueous solution of an organic oxidizing agent regenerated by atmospheric oxygen.

EFFECT: improved quality of marketable sulfur due to simultaneous removal of polysulfanes and residual hydrogen sulfide dissolved in liquid sulfur, lowering the temperature of the process of destruction of polysulfanes, elimination of the stages of treatment with aqueous or methanol solutions of alkali, and post-treatment on adsorbents.

It is achieved by the fact that in the proposed method, comprising supplying a molten sulfur to an aqueous solution of a one-electron oxidizing agent - 3.5 di-tert-butyl o-benzoquinone in an amount of 0.8% by weight, the process of decomposition of polysulfanes is carried out at a temperature of 70-90 ° C and regenerate the spent oxidizing agent in a stream of air. The degree of conversion of polysulfanes reaches 60-80%.

The proposed method is based on the ability of polysulfanes to oxidatively decompose to sulfur in the presence of o-benzoquinones in aqueous media. In this case, the oxidizing agent is converted to a hydrogenated form, which is regenerated in the stream of oxygen to the initial o-benzoquinone.

A method for the destruction of polysulfanes involves treating molten sulfur with an aqueous solution of 3.5 di-tert-butyl o-benzoquinone in an amount of 0.8% by weight, carrying out an oxidation process of polysulfanes at a temperature of 70-90 ° C.

The method is as follows.

Example 1. The destruction of polysulfanes in commercial sulfur obtained at the Astrakhan gas processing plant, after the degassing process.

Molten sulfur (weighing 50 g) containing 280 ppm polysulfanes is passed through a washing system (an aqueous solution of an oxidizing agent - 3.5 di-tert-butyl-o-benzoquinone in an amount of 0.8% by weight) at a temperature of 80 ° C and atmospheric pressure. The decomposition of polysulfanes occurs at the stage of granulation of the sulfur melt in water for 10 minutes. The oxidizing agent is converted to reduced dihydroform (3,5 di-tert-butyl pyrocatechol). The degree of conversion of the oxidizing agent is determined visually by the disappearance of the characteristic red-brown staining of the solution. The spent oxidizer is subjected to regeneration by supplying air to the solution (the regeneration time is 1 h, the degree of regeneration is 75%). The content of polysulfanes in the initial (liquid) sulfur and the treated (granular) sulfur is determined by the electrochemical method — cyclic voltammetry. Analysis of the studied sulfur after the process of destruction of polysulfanes showed that the residual content of polysulfanes is 75 ppm. The degree of conversion of polysulfanes to sulfur is 73.2%.

Example 2. The destruction of polysulfanes in commercial sulfur obtained at the Astrakhan gas processing plant, before the degassing process.

Under the conditions of Example 1, in the presence of the oxidizing agent described above (3.5 di-tert-butyl o-benzoquinone in an amount of 0.8% by weight), polysulfanes with a content of 360 ppm are degraded at a temperature of 90 ° C. and atmospheric pressure. The decomposition of polysulfanes occurs within 10 minutes. Analysis of the studied sulfur after the process of destruction of polysulfanes showed that the residual content of polysulfanes is 80 ppm. The degree of conversion of polysulfanes to sulfur is 77.7%.

Depending on the concentration of polysulfanes in the initial sulfur samples (150-600 ppm), the decomposition time of polysulfanes can be varied in the range of 5-30 minutes.

From the above examples it is seen that the process of destruction of polysulfanes by the proposed method allows you to remove polysulfanes from the sulfur melt and exclude the use of aqueous and methanol solutions of alkali.

The positive effect of the proposed method lies in the effectiveness of a one-stage process for the removal of polysulfanes and residual hydrogen sulfide from the sulfur melt, the intensification of the process through the use of an oxidizing agent that can be regenerated by atmospheric oxygen, improving the quality of commercial sulfur and ensuring the safety of its transportation and storage.

These advantages of the proposed method can significantly improve the technical and economic indicators of the degassing process in gas processing plants.

Claims (1)

The method of degradation of polysulfanes in commercial sulfur, including the supply of a sulfur melt into an aqueous solution of an organic oxidizing agent - 3.5 di-tert-butyl o-benzoquinone in an amount of 0.8 wt.%, The process of decomposition of polysulfanes at a temperature of 70-90 ° C and regeneration spent oxidizer in a stream of air.