NL8320198A - CATALYST FOR GAS PHASE OXIDATION OF SULFUR COMPOUNDS. - Google Patents

Description

. . 85 2 0.: -1- 24407 / Vk / mvl

Short designation: Catalyst for the gas-phase oxidation of sulfur compounds.

Field of the invention.

This invention relates to catalysts and more particularly to catalysts for the oxidation of sulfur compounds in the gaseous phase.

Description of the known prior art.

Of course, activated bauxite containing 50-70 wt% Al ^ 0 ^ »10 8-20 wt% Fe ^, 2-8 wt% SiO2, 0.5-5 wt% TiO ^ is used as catalyst for the oxidation of mercaptan with oxygen to disulfides (U.S. Patent 2,558,221, June 6, 1951, class 260-608).

This catalyst gives a no higher than 50% conversion of mercaptan to disulfides and moreover it can be used at a low space velocity of the supplied reagent. Therefore, this catalyst cannot be recommended for treating gases to remove mercaptans.

Also known is a catalyst for the oxidation of mercaptan tan with oxygen containing gas to disulfides such as activated bauxite, activated carbon, nickel oxide, iron oxide and cobalt oxide (U.S. Patent No. 2,589,249, dated November 4, 1958, class 250-608).

The degree of conversion of mercaptans using the above catalysts at a temperature of 170-270 ° C

25 does not exceed 95% at a space velocity of the reaction mixture of -1 approximately 25 hours. Insufficient conversion and low activity of the catalyst make it unsuitable for gas treatment.

Also known is a catalyst used for the oxidation of mercaptans with oxygen-containing gas to disulfides at a temperature of 150-220 ° C, such as copper and iron oxides applied to activated carbon or other supports (U.S. Patent 2,979,532, April 11 1961, class 260-608). Nor does this catalyst have an activity higher than 96%.

Some catalysts are known for the oxidation of hydrogen sulphide in gases. Thus, for example, activated carbon can be used for the oxidation of hydrogen sulfide to elemental sulfur, which is subsequently recovered from the regeneration 8320198 I f -2-24407 / Vk / mvl of coal (Journal of Catalysis, 35, No. 1, 1974; M Steijnt, P. Mart:

The Role of Sulfur Trapped in Micropores in Oxidation of Hydrogen Sulfide with Oxygen ", p. 11-17). The reaction on the carbon surface takes place at a temperature of 20-250 ° C. However, the sulfur that is formed at a temperature up to 200 ° C is precipitated on the carbon surface, reducing the catalyst activity At a temperature above 200 ° C, sulfur is oxidized to SO 2, resulting in a decrease in the selectivity of the carbon.

Zeolites can be used as catalysts for the oxidation of hydrogen sulfide (Transaction of Mendeleev Moscow Chemical Engineering Institute, No. 56, 1967, pp. 160-164: NV Keltsev, MA Adlivankina, NS Torocheshnikov, Ju.J. Shumjatsky "Investigation of Incomplete Oxidation of Hydrogen Sulfide using Zeolites "). Zeolites have a high activity when the oxidation of hydrogen sulphide is carried out at a low concentration, however, the activity decreases over time. Furthermore, a high activity of zeolites is obtained at low space velocities up to 1000 hours and at a temperature higher than 300 ° C.

Bauxite is known in the prior art as a catalyst for the oxidation of hydrogen sulphide. (U.S. Patent 3,781,445; Gasovaya Promyshlennost No. 8, 1966, pp. 42-44;

Ju.N. Brodsky, V.J. Gerus, S.M. Goland, Ja.J. Frenkel "The Production of Sulfur at Pokhvistnevskaya Gas Compressor Station"). However, the maximum hydrogen sulfur conversion at this facility is not above 93%. In addition, bauxite easily loses activity in the presence of steam. The use of bauxite as a catalyst for the oxidation of hydrogen sulfide is associated with the need for stringent control of the oxygen to hydrogen sulfide ratio, because as the ratio increases this results in a decrease in the selectivity of the catalyst by the formation of SO2 and a decrease in this results in a decrease in activity due to the residual amount of unreacted hydrogen sulfide.

Activated alumina is used as a catalyst for the oxidation of hydrogen sulfide (Ingener-neftjanik N4, pp. 36-38, 35 1973: "Modern Processes for Purification, Drying and Processing of Hydro carbon Gases; Chimia i Pererabotka Uglevodorodov N10, pp. 54- 60, 1978: P. Granshe "Progress in Claus Process Technology", part II Improvement 8320198 fr -3- 24407 / Vk / mvl of Industrial Plants and Operation Methods "; Inzhener-Neftjanik, no. 2, biz. 104-111 , 1973: M. Pirson, "Progress in the Development of Catalyst for Claus process"). However, the catalyst activity is lowered by the sulfation reaction on its surface and by the presence of water. The conversion of hydrogen sulfide becomes 2-2.5 reduced times when the water content increases from 5 to 35%.

The use of iron oxide as a catalyst is also limited (Russian Inventor Certificate No. 865777, class C01 B 17/04, 1981). As in the above case using this catalyst, it is impossible to obtain a selectivity of 100% and activity within the temperature range of 200-300 ° C and space velocities of -3000-15 * 000 hours. A catalyst containing 0.1 wt% iron oxide and 99.9 wt% titanium oxide has high activity and selectivity (Russian Inventor Certificate No. 856974, class C 01 B 17/04, 1981).

The conversion of 99.5% hydrogen sulphide and a catalyst selectivity of 100% can only be obtained in the two-step process at a relatively high temperature of 285-300 ° C and at a low space velocity -1 of 3000 hours.

Description of the invention.

The object of the invention is to obtain such a catalyst for the oxidation of sulfides with a high stable activity, selectivity and mechanical strength.

The above objective was achieved by obtaining a sulfide oxidation catalyst containing iron oxide catalyst, which according to the invention is characterized in that it contains chromium oxide and has the following composition, expressed in weight percent: 20-75 % Fe 2 O 2, 25-80% Cr 2 Oy catalyst has high activity and selectivity for the oxidation of hydrogen sulphide and mercaptans. Thus, the conversion at a space rate of the gaseous mixture of 6000 hours and at concentrations of hydrogen sulphide and oxygen in the gaseous mixture of 3 and 4.5% by volume at 250 ° C, respectively, of hydrogen sulphide is 97.6% and the selectivity for its oxidation to sulfur is not less than 98%. This catalyst also has high activity and selectivity for the oxidation of mercaptans.

The catalyst can consist of cobalt, nickel, manganese, copper, zinc and titanium oxides in an amount of 1.5-25% by weight. The 832 0 1 -4-24407 / Vk / mvl presence of the above oxides in the catalyst promotes an increase in their activity. The oxidation operation of hydrogen sulfide using the catalyst which is 28 wt% 17 wt%

Cr 0 contains 25 wt% ZnO effects a conversion of hydrogen sulphide 5 of 99> 9% at a space velocity of 6000 hours and at a temperature of 220 ° C and the selectivity of this process is 98.5%. The catalyst also has a high activity in the oxidation of - mercaptan at a space velocity of 2000 hours and at a temperature of 140 ° C, the conversion of mercaptan being 100% at a concentration thereof in the gas of 1.5 vol%.

For the oxidation of hydrogen sulphide and mercaptan, it is recommended to use a catalyst with the following composition: 20-30 wt.% Fe ^, 25-50 wt.% Cr ^, 10-25 wt.% TiC> 2 and 20-25 wt. .%

ZnO. The catalyst of the invention has a high activity for both the oxidation of hydrogen sulfide and mercaptans, although it is more effective for the oxidation of hydrogen sulfide. Thus, at a space velocity of 6000 hours 1 and at a hydrogen sulfur concentration of 3% by volume with an excess of oxygen, the hydrogen sulfur conversion is approximately 100%, at a substantially 100% selectivity for the oxidation to sulfur.

Thus, it follows from the above that the catalyst gives high values in the hydrogen sulfide and mercaptan conversions by oxidation at a higher rate and at higher oxygen concentrations in the gas mixture.

Preferred Embodiments of the Catalyst.

One of the catalyst forms for the oxidation of hydrogen sulphide and mercaptans is a catalyst having the following composition: 25-40 wt.% Fe 2, 40-50 wt.% Cr 2 O 3 with 20-25 wt.% Zinc oxide as the additive. The catalyst has a high activity and selectivity for the oxidation of hydrogen sulphide at an increased space velocity of the gas mixture. Thus, at a space velocity of the gas mixture of 9000 hours and at a temperature of 230 ° C, at concentrations of hydrogen sulphide and oxygen in the gas mixture starting from 3 and 2.25 vol%, respectively, the conversion to hydrogen sulphide is 98, 7% and the selectivity for the oxidation to sulfur not less than 99%. The catalyst also has a high activity for the oxidation of

83201f P

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-5- 24407 / Vk / mvl -1 mercaptans: at a space velocity of 2000 hours, at a temperature of 180 ° C and a concentration of mercaptans in the gas starting from 1.5 vol% with an excess of oxygen, gives the catalyst practically 100% conversion of mercaptans.

A better alternative to the catalyst is a catalyst containing 20-25 wt.% Fe 2, 25-50 wt.% Cr 2, 10-15 wt.% TiO 2 and 20-25 wt.%

ZnO contains. The catalyst has a high activity for the oxidation of both hydrogen sulphide and mercaptans.

At a space velocity of 6000 hours and at a temperature of 240 ° C with hydrogen sulfide and oxygen content in the mixture starting from 3 and 3% by volume, respectively, the catalyst converts 99.6% hydrogen sulfide at a substantially 100% selectivity for its oxidation to elemental sulfur. The oxidation of mercaptan in a high excess of oxygen at 1.5 vol% of the starting mercaptan concentration in the starting gas mixture, using this catalyst, a conversion of nearly 100% is obtained at 200 ° C and at a space velocity of 4000 hours 1.

One of the most important advantages of the catalyst is its high activity and selectivity at a high space velocity of up to 5000 hours and an excess of oxygen.

The catalyst has a high stability in the oxidation of hydrogen sulphide and mercaptans. Thus, when its activity is investigated in the oxidation of hydrogen sulphide in the presence of hydrocarbons of natural gas at a space velocity of 6000 hours 1, at a hydrogen sulphide and oxygen concentration of 3 and 2.25 vol% at 240 ° C, respectively, hydrogen sulfide conversion after 100 hours was 98.5% and selectivity was 98.9%. The activity of the catalyst in the oxidation of mercaptan remained high for a period of 1000 hours at a concentration thereof in the gas of 1.5% by volume with excess oxygen, at a space velocity of 2000 hours and at a temperature of 200 ° C. Mercaptans conversion was virtually 100%. It should be noted that the catalyst does not tend to deactivate in the above process.

35 One of the important advantages of the catalyst is the high activity in the presence of water vapor, hydrogen chloride, carbon dioxide, methanol and saturated hydrocarbons with 1-3 and 6 carbon 8320108

I I

-6- 24407 / Vk / mvl atoms. The content of these components in a gas mixture does not affect the activity of the catalyst and the selective conversion to elemental sulfur without the formation of by-products such as sulfurous anhydride.

The desired influence cannot be achieved when the quantitative content of the catalyst components is changed. A drop in the iron oxide content in the catalyst to less than 20% by weight results in a decline in the catalyst activity and an increase in the iron oxide content in more than 75% by weight results in a reduction in the selectivity of the catalyst .

Decreasing the chromium oxide content to less than 25% by weight gives no further effect and increasing this content to more than 80% by weight decreases the catalyst activity.

Decreasing the additives to the metal oxide in the catalyst to less than 1.5 wt.% Has no advantages, since it adversely affects the properties of the catalyst and results in an increase in its content to more than 25 wt.% in a reduction in the selectivity of the catalyst in cobalt, nickel and copper oxides, in a reduction in the catalyst activity in manganese and zinc oxides and in a shortening of the operating time of the catalyst in a titanium oxide content.

An important advantage of the catalyst of the present invention is that it is prepared from an inexpensive and readily available starting material by a simple process. The water-soluble salts of iron, chromium, titanium and zinc are used for the preparation of the catalyst. Predetermined amounts of these salts are dissolved in distilled water.

The solutions are prepared in separate vessels. Thereafter, the corresponding hydroxides are completely precipitated from the salt solutions using 3N aqueous solution. The pH of the solution is used to determine the degree of precipitation. The resulting precipitates are fed to a vessel and stirred well, after which the precipitate is washed with warm distilled 2-water to make the negative determination for chlorine ions or SO 2. The washed precipitate is filtered, finely ground and dried in air at ambient temperature and then roasted at 450-500 ° C for 4 hours.

8320108 J ί -7- 24407 / Vk / mvl

The final catalyst has a cylindrical shape with a grain diameter of 3-5 mm and a height of 8-12 mm. The catalyst has a specific surface area of 35-45 m / g. The catalyst has a high strength: mechanical abrasion resistance (residue) determined in a jet type mill with the operating time, determined in air, being 85-90%. The catalyst is thermally stable at a temperature up to 950 ° C.

As will be apparent from the above description, the catalyst preparation process is simple and requires no special equipment and no expensive, not readily available materials.

For a further explanation of the present invention, the following specific examples are given for the preparation and composition of the catalyst.

Example I

15 g of iron sulphate were dissolved in 550 ml of distilled water in a vessel and 10 g of chromium sulphate were dissolved in 360 ml of distilled water in another vessel. Then a 6% ammonia solution was added to these solutions with continuous stirring until complete precipitation of iron and chromium hydroxides. The resulting suspensions were fed to a vessel, stirred well and then allowed to settle for 12 hours. The precipitate was then washed with 2-distilled water to a negative reaction with SO 2 ions, filtered, ground, dried at 120 ° C for 1.5 hours and roasted at 450 ° C for 5 hours. The resulting catalyst had the following composition: 60 wt.% Fe ^ ^ and ^ Sew *% Cr2 ° 3 "

Example II

The catalyst was prepared as indicated in Example I using 7> 5 g Fe 2 SO 4), 12 g Cr 2 SO 4), 4 g ZnSO 4. The resulting catalyst had the following composition: 30 wt.% Fe 2, 50 wt.% Cr 2 O 2 and 20 wt.% ZnO.

Example III

The catalyst was prepared as indicated in Example 1 using 15 g Fe2 (SO2) ^, 6.25 g Cr ^ SO ^) ^, 3 g CuSO ^. The resulting catalyst had the following composition: 60 wt.% Fe, 25 wt.% Cr 2 O 3 and 15 wt.% CuO.

8320198

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-8- 24407 / Vk / mvl

Example IV

The catalyst was prepared as indicated in Example 1 using 15 g Fe 2 SO 4), 4.5 g Ti (SO 2) 2. The resulting catalyst had the following composition: 54 wt% Fe 2 O 2, 33 wt% Cr ^ 5 and 13 wt% TiCl2 as anatase modification.

Example V

The catalyst was prepared in the same manner as in Example 1, using 10 g Fe 2 SO 2), 12.5 g 2.1 g MnSO 2. The resulting catalyst had the following composition: 40 wt.% Fe 2, 50 wt.% And 10 wt.% MnO.

Example VI

The catalyst was prepared as indicated in Example 1 using 12.5 g Fe 2 SO 4), 12.6 g Cr 2 SO 4), 1.2 g CoSO 4.

The resulting catalyst had the following composition: 50 wt.% Fe 2 4, 45 wt. Cr ^ and 5 wt% CoO.

Example VII

The catalyst was prepared as indicated in Example I using 11.7 g Fe 2 SO 4), 12.8 g Cr 2 SO 4), 4 g NiSO 4. The resulting catalyst had the following composition: 40 wt.% Fe 2, 4, 43 wt.% Qr 2 O 2, and 17 wt.% NiO.

The catalyst obtained in Examples I-VII was tested for the oxidation of mercaptan. The operating conditions and results are summarized in Table A.

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As will be apparent from the table, the catalyst according to the invention is characterized by a high selectivity (higher than 98%) and a high conversion of mercaptan (97-99> 9%) which is considerably better than with the known catalysts used for the oxidation of mercaptan.

Example VIII

To prepare the catalyst, 25.5 g of ferric chloride in 943 ml of distilled water, 26.3 g of chromium chloride in 1000 ml of water, 17.8 g of titanium chloride in 940 ml of water and 10 12.5 g of zinc chloride in 916 were added in separate vessels. ml of water dissolved. To the resulting solutions, 3N aqueous solution of ammonia was added with continuous stirring until complete precipitation of the corresponding hydroxides. The pH of the solution was used to determine the amount of precipitation. The resulting hydroxide precipitates were fed to a vessel and stirred well and the precipitate was washed with warm distilled water until negative reaction to chloride ions. The precipitate was then filtered off, ground, air dried at ambient temperature and roasted at a temperature of 500 ° C for 4 hours. The resulting catalyst had the following composition: 25 wt% 25 wt% Cr25 wt% TiO 2 and 25 wt%

ZnO.

Example IX

To prepare the catalyst, 30.5 g of ferric chloride was dissolved in 1128 ml of distilled water, 21 g of chromium chloride in 788 ml of water, 21.5 g of titanium chloride in 1133 ml of water and 10 g of zinc chloride in 734 ml of water. The catalyst was then prepared according to the procedure described in Example VIII. The resulting catalyst had the following composition: 30 wt% Fe 2 4, 25 wt% Cr 2 O, 25 wt% TiO 2, and 20 wt% ZnO.

30 Example X

To prepare the catalyst, 20.3 g of ferric chloride was dissolved in 750 ml of distilled water, 52.6 g of chromium chloride in 1975 ml of water, 7.1 g of titanium chloride in 375 ml of water and 10 g of zinc chloride in 735 ml of water. The catalyst was then prepared according to the method described in Example VIII. The resulting catalyst had the following composition: 20 wt% Fe 2, 50 wt% Cr 10 wt% TiO 2 and 20 wt% ZnO.

8320198 I Λ -11- 24407 / Vk / mvl

The catalyst samples obtained contained granules of cylindrical shape with a diameter of 3-5 mm and a height of 8-12 mm. The specific surface area of the catalyst was 35-45 m / g.

The mechanical abrasion resistance (residue) was 85-90%. The catalyst was thermally stable at a temperature up to 950 ° C.

The results of experiments with the obtained catalyst samples for the oxidation of hydrogen sulphide under different conditions are shown in Table B.

TABLE B

catalyst according to tempera- ture-concen- trating example, reaction speed — raie — conversion rate theorem (wt%) (° C) (h) H2S ^ 2 (%) 1 2 3 4 5 6 7 8

Example_VIII

1 Fe203 - 25 220 6000 3 3 -100 -100 2 Cr203 - 25 240 3000 3 4.5 -100 98.8 3 Ti02 - 25 260 15000 3 3 99.9 100

ZnO - 25

Example_IX

5 Fe203 - 30 220 6000 3 3 -100 -100 6 Cr203 - 25 240 15000 3 4.5 99.1 -100

TiO2 - 25

ZnO - 20

Example X.

a) test duration: 2 hours 9 Fe203 - 20 220 6000 3 3 98.5 -100 10 Cr203 - 50 240 15000 3 4.5 98.6 -100

TiO2 - 10

ZnO - 20 b) Test duration: 100 hours 240 6000 3 2.25 98.5 98.9

As will be apparent from Table B, the resulting catalyst exhibited high activity (conversion of Η2 $ is not less than 98.5%) and selectivity for the oxidation of sulfur water- 8 3 2 0 1 D 8, Λ -12- 24407 / Vk / mvl dust to elemental sulfur is not less than 98.8% at high speeds up to 15000 hours ^ and an excess of oxygen in the gas mixture.

Industrial applicability.

The catalyst of the invention can be used in the purification of gas and oil to remove hydrogen sulphide and mercaptan compounds from gases as well as residual gases from the Claus process and regeneration gases obtained from the adsorption purification of natural gas in the ammonia preparation.

In summary, the invention relates to a catalyst containing the following components: 20-75 wt% iron oxide and 25-80 wt% chromium oxide. The catalyst can contain cobalt, nickel, manganese, copper, zinc, titanium oxides in an amount of 1.5 to 25% by weight.

8 3?. 0 1 9 8

Claims (3)

1. Catalyst for the gas-phase oxidation of sulfur compounds, which catalyst contains iron oxide, characterized in that it contains chromium oxide and has a composition of 25-75% by weight iron oxide and 25-80% by weight chromium oxide. 1. Catalyst for the gas-phase oxidation of sulfur compounds, which catalyst contains iron oxide, characterized in that it also contains chromium oxide and that the composition is 20-60 wt.% Iron oxide and 25-50 wt.% Chromium oxide. Catalyst according to claim 1, characterized in that it contains cobalt, nickel, manganese, copper, zinc and titanium oxides in an amount of 1.5 to 25% by weight. Catalyst according to claim 1, characterized in that it contains cobalt, nickel, manganese, copper, zinc, titanium oxides in an amount of 1.5 to 30% by weight. Catalyst according to claims 1-2, characterized in that it contains iron, chromium, titanium, zinc oxides in the following amounts: 20-30 wt.% Iron oxide, 20-50 wt.% Chromium oxide, 10-30 wt. % titanium oxide and 20-25 wt% zinc oxide. 8320198 1 »1% -14- 24407 / Vk / mvl IMPROVED CONCLUSIONS for the international patent application. Catalyst according to claim 2, characterized in that it contains iron, chromium, titanium and zinc oxides with the following composition: 20-30% by weight iron oxide, 25-50% by weight chromium oxide, 10-25% by weight titanium oxide and 20-25 wt% zinc oxide. 8320198