RU2414298C2 - Catalyst and method of deep cleaning of gas mixes from carbon sulphide in its presence - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to catalytic methods of cleaning gas mixes of carbon sulphide. Proposed catalyst comprises activated silicon dioxide matrix produced by acid etching of natural vermiculite, and nano-sized particles of iron or iron oxides, or mixes thereof, in amount of 0.1-2.5 % by wt relative to mass of silicon oxide and at copper-to-iron ratio in their mix equal to 0.3. Proposed invention covers also the method of catalytic deep cleaning of gas mixes of carbon sulphide by its oxidising oxygen. Note here that gas mixes represent mixes containing carbon sulphide in amount of about 1%, while process occurs in the presence of above described catalyst to residual content of sulfur not exceeding 1 ppm.

EFFECT: described catalyst allows conversion of carbon sulphide equal to 95-99 %.

5 cl, 4 tbl, 3 dwg, 43 ex

Description

The present invention relates to nanotechnology in heterogeneous catalysis, and in particular to a method for deep purification of natural gas from hydrogen sulfide, and can be used to prepare natural gas for subsequent conversion processes to hydrogen and synthesis gas.

Today and the near future, the production of hydrogen and synthesis gas is mainly based on catalytic conversion processes, including steam conversion of natural gas, in which nickel deposited on substrates of various nature in the form of oxide acts as the main component of the catalyst.

However, the nickel components of the catalyst are highly sensitive to poisoning by sulfur-containing components, including hydrogen sulfide, which is present in the natural gas of many deposits. So, the content of hydrogen sulfide in natural gas sometimes reaches 15-20%. At the same time, the level of necessary purification of natural gas entering the catalytic conversion of methane and estimated by the residual concentration of hydrogen should not exceed 1-2 ppm.

In this regard, one of the most important problems in the field of production of hydrogen and synthesis gas from natural gas is the degree of its purification from hydrogen sulfide. For example, already after amine purification, the content of hydrogen sulfide in methane is from 2 to 6 ppm. This amount is enough to irreversibly poison expensive methane conversion catalysts.

Exhaustive purification of methane is carried out by stoichiometric interaction of hydrogen sulfide with expensive zinc oxide, which is a reagent at this stage, the regeneration process of which is energy-intensive and expensive.

Thus, all the above problems make it extremely urgent to develop processes for the direct, exhaustive catalytic purification of reaction exhaust gases and household gases from hydrogen sulfide.

One of the promising methods for exhaustive purification of gases from hydrogen sulfide is direct oxidative catalytic decomposition on a number of metal-containing catalysts.

The first works in this area relate to the use of nickel, molybdenum, chromium, vanadium, and other metal-containing catalytic systems based on traditional supports, such as oxides of aluminum, silicon, and aluminosilicates. Such catalysts are obtained, as a rule, by the method of impregnation of carriers from aqueous solutions of inorganic salts, mainly nitric acid.

The main feature of the process is the selective oxidation of hydrogen sulfide in air to elemental sulfur:

H ₂ S + 1 / 2O ₂ → S + H ₂ O

As can be seen from the chemical equation, an air medium is necessary for supplying a stoichiometric amount of oxygen in order to ensure thermodynamically favorable conditions for the process. However, the oxygen kinetics of the reaction is lower than the first order. This indicates that active oxygen of the catalyst surface is involved in the reaction, while molecular oxygen is most likely necessary for saturation of the surface (healing of defects). The temperature of the decomposition processes of H ₂ S on known catalysts does not exceed 300 ° C.

At the same time, it should be noted that higher temperatures than 300 ° C, or an excess of molecular oxygen can lead to the oxidation of sulfur to SO ₂ :

H ₂ S + 1,5O ₂ → H ₂ O + SO ₂

The sulfur consumption of such catalysts, as a rule, is low, which leads to low productivity and frequent regeneration, and the methods for their production are energy intensive and environmentally hazardous. Therefore, these methods of decomposition of hydrogen sulfide are more likely to be fundamental in order to study the mechanism of catalytic decomposition itself and are unlikely to be used in industry for economic reasons.

Metal-containing catalysts for the purification of gases from hydrogen sulfide based on carbon carriers are also known.

For example, earlier in ed. testimonial. USSR No. 1761236, 1992 was proposed for the purification of gases from hydrogen sulfide by its oxidative decomposition using brown coal containing nickel or iron as catalysts for hydrogenation, and RF patent No. 2172647, 2001 proposed an iron-carbon catalyst for selective oxidative decomposition of hydrogen sulfide.

The main drawback of such catalysts is their fire hazard, especially considering that the process of direct oxidation of hydrogen sulfide is exothermic with a large thermal effect (Q = 53 kcal / mol).

In US patent No. 2003194366 of 2003, a method was described for purifying hydrogen sulfide contained in a wide range of organic substrates, such as gaseous hydrocarbons, aromatic and oxygen-containing compounds, in the presence of an extremely wide (practically the entire Periodic system of elements) metal oxides (aluminum oxide, silicon titanium, modified Fe, Co, Mn, Cr, Cu, Mo, Nb, etc.) or mixtures thereof at temperatures close to 400 ° C to sulfur and sulfur oxides. Despite the wide coverage of possible conditions, the patent has a number of significant drawbacks, the main of which is that only a specific form of oxides fixed on the surface of the carriers allows for the deep and selective oxidation of hydrogen sulfide to sulfur. Criticism and high temperatures of the proposed process. Metal oxides, such as Mn, Cr, at these temperatures oxidize hydrogen sulfide to sulfur oxides, which is unacceptable in the process of gas purification. Copper and molybdenum oxides exhibit low activity if they are not present in the specific form of nanosized particles. Massive oxides of iron and cobalt quickly undergo sulphurization and lose activity. Moreover, stable sulfide forms do not leave the possibility of their regeneration. The patent in question is more suitable for the first stage of the Claus process, in which part of the hydrogen sulfide must be oxidized to sulfur dioxide. This analogue does not indicate the depth of purification from hydrogen sulfide, which is an important technological and environmental factor for the subsequent use of gas. Thus, the considered analogue is not a solution for deep gas purification from hydrogen sulfide.

The closest analogue is the catalyst and method according to the patent of the Russian Federation No. 2114685 from 10.07.1998.

According to this patent, it is proposed to use a material consisting of silicon oxide (silica) and containing one or more transition metal oxides, such as Ni, Co, Fe, Cu, as an active component in the catalyst for deep purification of gas mixtures from hydrogen sulfide. , Ag, Mn, Mo, Cr, W, V.

The method of deep purification of gas mixtures from hydrogen sulfide according to this patent in the presence of this catalyst involves the oxidation of hydrogen sulfide to elemental sulfur by contacting the initial mixture of gases and gas containing free oxygen in an amount providing a molar ratio of O ₂ : H ₂ S 0.5-3.0 with a catalyst for the selective oxidation of hydrogen sulfide to sulfur at 50-180 ° C with the deposition of sulfur formed on the catalyst and obtaining a gas stream that is practically free of hydrogen sulfide; regeneration of a catalyst filled with sulfur, sold uvki gas that does not contain free oxygen, at a temperature sufficient to evaporate the sulfur deposited on the catalyst.

The main comments on these catalysts and the method include insufficient catalyst stability, complexity of the technology, high energy intensity of catalyst regeneration.

The objective of the invention is to create a catalyst that exhibits high activity, selectivity and stability during the deep cleaning of gas mixtures from hydrogen sulfide, as well as cheaper and easier technology by reducing the energy intensity of catalyst regeneration.

The problem is solved in that a catalyst for the deep purification of gas mixtures from hydrogen sulfide is proposed, containing a silica matrix and particles of iron or copper oxide or a mixture thereof, which contains an activated silica matrix obtained by acid etching of natural vermiculite and nanosized particles of iron or copper oxide or mixtures thereof, in an amount of 0.1-2.5 wt.% based on the metal relative to the mass of silica and with a ratio of copper to iron in their mixture equal to 0.3.

The problem is also solved by the fact that the proposed method for the catalytic deep purification of gas mixtures from hydrogen sulfide by oxidizing it with atmospheric oxygen to elemental sulfur, in which the process is conducted in the presence of the proposed catalyst to a residual sulfur content of not more than 1 ppm. The process is carried out at a temperature of 25-250 ° C, the volumetric rate of supply of the gas mixture to the catalyst, equal to 1000-4000 h ^-1 using gas mixtures with a hydrogen sulfide content of up to 1 vol.%.

Moreover, when the process is conducted at temperatures below 120 ° C, after passing 14,000 volumes of gas per 1 volume of catalyst, without stopping the supply of reagents, periodic regeneration of the catalyst is carried out. To this end, the temperature in the reaction zone is increased to 250 ° C, the oxidation process is carried out at this temperature for 2 hours, after which the temperature is again reduced to the initial one.

The activated silica matrix is obtained by acid etching of natural vermiculite according to the procedure described in USSR Authentic Certificate No. 1042794, B.I. No. 35.1983; RAS (ser. Chem.), 1984, 6, p.1237-1241; Journal of Physical Chemistry, 2007, Vol. 81, No. 5, 781-787.

Step etching of vermiculite allows to obtain highly purified silica with a developed mesoporous structure.

Previously, the authors of the present invention found that the silica matrix obtained by acid etching of vermiculite shows affinity for Group VIII metals, including them in the structure of silica when its surface interacts with complexes of the corresponding metals, and becomes active in a number of reactions as a result of the inclusion of metal ions in the interlayer space of the matrix, which was published in a number of works: A.S. No. 1039534, B.I. No. 33, 1983; Physical chemistry of ultrafine systems. Collection edited by Acad. Tananaeva I.V., Science, p.132-139, 1987; Izv. RAS (ser. Chem.), 6, p. 1724-1728; Hyperfme Interaction, 1990, 57, b. 1983-1986; Izv. RAS (Ser. Chem.), 2004, No. 6, 1376-1382; Inorganic Materials, 2006, Volume 42, No. 4, 1-4.

For example, the iron-containing matrix obtained in this way is active in the reaction of hydrogenation of CO in hydrocarbons “Inclusion of iron in a modified layered silicate and the influence of its state on selectivity in the reaction of hydrogenation of CO”, Izv. RAS (ser. Chem.), 12, p. 2666-2670, 1986.

However, it was previously not known that the metal-containing silica matrix exhibits increased activity and stability in the oxidative decomposition of hydrogen sulfide into sulfur.

The increased stability of the proposed catalytic systems is due to the strong interaction of the silica matrix and metal ions included in its structure, which does not allow metal ions to pass into inactive forms of metal sulfides, such as pyrrhotite and pyrite, the formation of which on the surface of the catalyst leads to its sulfurization upon exposure to hydrogen sulfide as a result, loss of activity.

The following examples illustrate the invention, but in no way limit its scope.

Media Preparation

Example 1

Calcined natural vermiculite with a fractional composition of 60-80 mesh. in the amount of 100 g is subjected to 2-stage etching, in which at the 1st stage diluted 5-7% hydrochloric acid in the amount of 300 g is used at a temperature of 50-60 ° C with stirring for 2 hours, and then at 2- stage I is treated with a 2-fold volume of concentrated hydrochloric acid (d = 1.18 g / cm ³ ) at 70-80 ° C for 4 hours.

After etching, 50-60 g of sorbent are discharged, which is washed with distilled water until neutral (pH 6-7 per litmus indicator) and, depending on the desired type, the powder or tablets are either dried in air or wet pressed into tablets then the tablets are dried in a vacuum oven at 100 ° C and then calcined in a muffle cabinet at 200 ° C for at least 2 hours, 350 ° C for 2 hours and at 500 ° C for 4 hours.

An activated silica matrix is obtained, the porous structure of which is characterized by a specific surface area of 320-350 m ² / g and a pore size of 3-4 nm.

Example 2

The first stage of etching is carried out with 100 g of calcined vermiculite, as in example 1.

In the second stage, the carrier is etched with a 2-fold excess of 40% sulfuric acid at a temperature of 80-90 ° C for 2-3 hours.

Then proceed as described in example 1.

The porous structure of the activated silica matrix is characterized by a specific surface area of 430 m ² / g and supermicropores with a size of 1.0-2 nm.

Example 3

The first stage of etching is carried out with 100 g of calcined vermiculite, as in example 1.

In the second stage, 40% orthophosphoric acid is used in a 2-fold excess by volume, etching is carried out and calcined stepwise, as in example 1.

The porous structure of the activated silica matrix is characterized by a specific surface area of 420-430 m ² / g and supermicropores with a size of 1.0-2 nm.

Example 4

The first stage is carried out, as in example 1. In the second stage, the sorbent is treated with stirring with a 3-fold excess of a mixture consisting of 30-50% sulfuric acid and 60% nitric acid, taken in quantities of 60 and 40 vol.%, Respectively . Then dried and calcined, as in example 1.

The porous structure of the activated silica matrix is characterized by a specific surface area of 350 m ² / g and small mesopores with a size of 4-6 nm.

Example 5

The first stage of etching of natural vermiculite is carried out, as in examples 1 and 2.

After washing, the carrier is subjected to stepwise drying, first in air, then in a vacuum oven at a temperature of 100 ° C, and then processed in a muffle furnace at temperatures of 250, 350 and 550 ° C.

Then, without access to moisture, the carrier is discharged into an impregnation vessel, into which, with stirring, a 2% aqueous solution of urea, carbonate or ammonium acetate is added and soaked for 2 hours. The adsorption capacity of the matrix, estimated by the volume of absorbed water per 100 g of sorbent, increases from 0.28 cm ³ / g for the samples obtained in examples 2-4 to 40 g of an aqueous solution per 100 g of support.

After impregnation, the carrier is dried first in air, and then in a vacuum oven at 80-100 ° C. Then the carrier is placed in a muffle furnace and kept at a temperature of 400-450 ° C for 30 minutes, after which the carrier is removed from the furnace and cooled to room temperature.

The activated silica matrix thus obtained is characterized by a specific surface area of 350-400 m ² / g and a pore size of 2-4 nm.

Example 6

The first stage of vermiculite etching is carried out, as in example 1. After etching, 80 g of silica are discharged, washed with distilled water until a neutral reaction to the indicator, and heat treated, as in example 1.

The specific surface area of the activated silica matrix discharged after one-stage etching with dilute hydrochloric acid is 450-470 m ² / g and the pore size is 1.0-1.5 nm.

Example 7

Vermiculite, taken as in example 1, is subjected to single-stage etching with 3 times the amount of concentrated hydrochloric acid at a temperature of 70-80 ° C with stirring for 4 hours.

Then the matrix is unloaded, washed with distilled water until a neutral reaction to the indicator and subjected to heat treatment, as in example 1.

The specific surface area of the activated silica matrix is 250 m ² / g with an average pore size of 6-8 nm.

The results of the examples are presented in table 1.

The method of stepwise processing of natural vermiculite is as follows.

At the first stage, the bulk of non-empirical inclusions are etched from natural vermiculite, the main of which are Al, Mg, and Fe ions. In this case, soft etching leads to the nucleation of micropores. The specific surface area of silica obtained after the first stage of vermiculite etching is 450-470 m ² / g.

Table 1 Porous structure and characteristic adsorption energy of matrices based on vermiculite N / N Examples of Preparation of Activated Matrix The pore volume, V, cm ³ · g Specific surface, m ² / g Characteristic adsorption energy kcal / mol V _micro V _meso V _macro one 0,110 0.377 0.010 350 1,6 2 0.106 0.311 0.05 430 1.3 3 0,110 0,300 0.1 420-430 four 0,097 0.249 0.08 410 1,1 5 0,055 0.260 0.5 300 6 0.250 0,050 0.01 420 7 0.01 0.150 0,100 90

Etching with concentrated acids in the second stage occurs mainly along micropores and leads to their increase, as well as to an increase in the total adsorption volume of the activated silica matrix. If in the first stage, despite the large specific surface area, the adsorption volume does not exceed 0.15-0.2 cm ^{3 of} benzene per 1 g of support, then in the second stage the adsorption volume of pores increases to 0.5 cm ³ / g.

When etching in one step with concentrated acid, the macrostructure of the matrix is destroyed, and ultimately the activated silica matrix is characterized by low adsorption capacity with respect to organic products.

According to example 5, there is a directed development of the adsorption volume while maintaining a high affinity of the activated silica matrix for the adsorption of hydrocarbons. In this example, the adsorption of inorganic sorbates is carried out in micropores formed in the first stage of etching with dilute acid. During the subsequent thermal action (thermal shock), the adsorbed ammonium salts decompose, resulting in partial destruction of micropores and their increase with the formation of mesopores. In this case, the macrostructure of the activated silica matrix remains close to the natural compound.

Obtaining a catalyst for the decomposition of hydrogen sulfide

After etching, the activated silica matrix is washed with distilled water to a neutral medium, fractionated, a fraction with sizes of 0.1-0.4 mm is taken and metal oxides are applied from organic solutions of their metal complex precursors, for example, acetylacetonates, acetates, formates or pivolates, followed by drying in air, by vacuum and stepwise heat treatment at a temperature of 300, 400 and 600 ° C for one hour at each temperature.

Examples 8-11.

On the activated silica matrix obtained as described in example 1, 0.1 is applied by impregnation; 1.5; 2.5 and 5% iron from 50 cm ^{3 of} solutions containing the corresponding amounts of iron acetylacetonate [Fe (acac) ₃ ] in toluene at room temperature and stirring for 4 hours until the solution decolours.

After impregnation, the iron-containing matrix is dried in the atmosphere and then stepwise heated to 200, 300 and 550 ° C, keeping at each temperature for two hours.

Examples 12-14.

Get the catalyst containing 1.5% Fe, as described in example 9, using the activated silica matrix obtained in examples 3-5, respectively.

Examples 15-16.

Get the catalyst containing 1.5% Fe, as described in example 9 using the activated matrix of silica obtained in examples 6 and 7, respectively.

Example 17

Copper acetylacetonate (Cu ²⁺ ), dissolved, dissolved in 0.5 cm ^{3 of} monoethanolamine - get a solution of 1, which is then diluted with toluene and get a solution of 2.

Iron acetylacetonate complex is added to solution 2 to obtain solution 3.

The activated silica matrix obtained in example 1 is impregnated with solution 3 with stirring for 2 hours, after which the catalyst system is dried, as described in examples 7-10.

Copper acetylacetonate (Cu ²⁺ ) and iron acetylacetonate complex are taken in the amounts necessary to obtain a catalyst containing 1.5 wt.% Fe and 0.5 wt.% Cu.

Example 18

A catalyst is prepared as described above, containing only 1.5% copper oxide as the active component, based on copper, relative to the activated silica matrix obtained in Example 1.

Example 19

An iron-copper catalyst is prepared, as in example 17, using an activated silica matrix obtained in example 1, with the application of active components from solutions of formate complexes of iron and copper in toluene.

Example 20

An iron-copper catalyst is prepared, as in Example 17, using carboxylate complexes (pivolates) of iron and copper and an activated silica matrix obtained in Example 1.

Purification of gas mixtures from hydrogen sulfide

The purification of gas mixtures from hydrogen sulfide by its oxidation to elemental sulfur is carried out using two model gas mixtures: the first, consisting of methane containing 0.5 vol.% H ₂ S and stoichiometric in relation to hydrogen sulfide, the amount of air oxygen (1.5%) and the second, corresponding to the waste of the Klaus-process and containing 30% water vapor, 0.5% H ₂ S; 0.5% O ₂ , the rest is N ₂ .

Experiments on the oxidation of hydrogen sulfide are carried out in a flow-through glass apparatus with a fixed catalyst bed. 5 cm ^{3 of} catalyst crumbs, the size of which d = 3 mm, are loaded into the reactor. For this, the iron-containing activated silica matrix is ground in an agate mortar, 8 × 3 mm tablets are pressed from the powder, which are then broken. The experiments are carried out at a temperature of 25-250 ° C and a volumetric feed rate of the gas mixture to the catalyst, equal to 1000-4000 h ^-1 .

The loaded catalyst is pretreated with an inert gas (N ₂ ) at a temperature of 400 ° C for 2 hours.

From the reactor, gas passes through a refrigerator and sparges through a 10% CdCl ₂ solution. The conversion of H ₂ S is determined by the gravimetric method: the breakthrough of hydrogen sulfide is fixed by the formation of a precipitate of cadmium sulfide, which is filtered off, dried and weighed.

The degree of conversion of hydrogen sulfide is determined by the formula:

α _H2S = [1-1.39a] 100,

where α is the degree of conversion of H ₂ S, vol.%; a is the amount of CdS formed in the solution, g.

Examples 21-24.

The oxidation of hydrogen sulfide contained in methane (0.5 vol.%) Is carried out at a temperature of 100 ° C and a gas flow rate of 1000 h ^-1 in the presence of catalysts containing 0.5; 1.5; 2.5 and 5% iron obtained according to examples 8-11.

The test results of the direct oxidation of hydrogen sulfide contained in methane, in accordance with examples 21-32 are presented in table 2.

table 2 N / N H ₂ S Oxidation Examples Catalyst Preparation Examples No. Temperature ° C Volumetric gas flow rate, h ^-1 The conversion of H ₂ S,% The specific volume of gas passed before the breakthrough, vol. gas / vol. cat 21 8 one hundred 1000 95 15,000 22 9 one hundred 1000 > 99.9 > 20,000 23 10 one hundred 1000 > 99.9 > 20,000 24 eleven one hundred 1000 92 10,000 25 12 120 80 5000 26 13 120 > 99.9 > 20,000 27 fourteen 120 > 99.9 > 20,000 28 fifteen 120 70 10,000 29th 16 120 60 5000 thirty 8 150 2500 Residual concentration - 10 ppb > 50,000 31 8 150 4000 Residual concentration - 10 ppb > 50,000 32 8 25-30 > 99.9 13000 (1 cycle), 13000 (2 cycle), 13000 (3 cycle)

As can be seen, the catalytic activity of iron-containing silica increases with an increase in the content of the active component up to 1.5%, which is expressed in greater sulfur intensity and the amount of gas (up to 20,000 v / v of catalyst) that has passed through the catalyst bed to breakthrough during exhaustive hydrogen sulfide conversion. An increase in the content of the active component to 2.5% does not lead to a change in the resource of the system used. At the same time, at 5% of the iron-containing component, the activity of the system decreases, which, as shown by the study by Mössbauer spectroscopy and magnetic susceptibility, is associated with the enlargement of particles of the active phase of iron oxide.

So, when the content of iron catalyst in the sample is up to 2.5%, about 20% of its content in the sample is ions (Fe ³⁺ ) associated with oxygen on the surface of silica, and the remaining 80% are in the interlayer space of silica in the form of superparamagnetic gamma oxide particles iron with a size of 2-4 nm, also strongly interacting with the surface oxygen of the silica matrix, which provides increased stability of the proposed catalyst.

At a higher content (more than 2.5 wt.%), Iron is represented by coarse particles of gamma iron oxide and magnetite with a size of 6-8 nm. Such particles do not interact so strongly with the surface of silica and, when exposed to a strong oxidizing agent, such as H ₂ S, pass into the sulfide phases of pyrrhotite and pyrite, i.e. the catalyst is sulphurized and its activity is lost.

Examples 25-27.

The hydrogen sulfide contained in methane is oxidized in the presence of catalysts containing 1.5% iron and obtained according to examples 12-14, respectively.

As can be seen from table 2, the activity of the catalytic system is not inferior to the iron-containing catalyst obtained in example 1.

Examples 28-29.

The hydrogen sulfide contained in methane is oxidized in the presence of catalysts containing 1.5% iron, obtained according to examples 15-16, respectively.

As can be seen from table 2, the catalyst prepared on the basis of a matrix of silica obtained by single-stage acid etching of vermiculite, has a lower catalytic activity compared with the catalysts tested in examples 21-24.

The breakdown of hydrogen sulfide occurs after passing 10,000 vol. gas at 1 vol. catalyst.

The decrease in catalytic activity of the catalysts prepared in examples 15 and 16, most likely, is explained by the lower adsorption volume of the initial silica matrix obtained as a result of single-stage acid etching.

Thus, the most optimal catalyst for the oxidation of hydrogen sulfide to sulfur, both from the standpoint of catalytic activity and from the point of view of simplicity and cheapening of the process of its preparation, is the system obtained in example 8 based on an activated silica matrix obtained by two-stage etching with hydrochloric acid, according to example one.

Example 30

In order to thoroughly purify methane from hydrogen sulfide, hydrogen sulfide is oxidized in the presence of the optimal catalyst sample obtained in Example 8 for a methane gas mixture containing 0.1% H ₂ S. In this experiment, 240 l of methane containing hydrogen sulfide are passed through 5 cm ^{3 of} catalyst , at 150 ° C and with a space velocity of 2500 h ^-1 .

The depth of gas purification is estimated by the sulfur content in the solid residue of an aqueous solution of CdCl ₂ , adjusted for sulfur impurities in the initial cadmium chloride. The latter is determined on the basis of hydrogen sulfide, which interacted with CdCl ₂ in a bubbler solution at the outlet of the reactor. For this, an aqueous solution of CdCl _{2 is} evaporated, and the dry residue is dried. The amount of sulfur of hydrogen sulfide interacting with cadmium chloride is determined by laser spectrometry.

During the experiment, no precipitation of cadmium sulfide was observed. An analysis of the dry precipitate isolated from the bubbler by laser spectrometry showed that, adjusted for trace amounts, sulfur was found in it - 0.0005% S - (0.000025 g) in 5 g of loaded CdCl ₂ . This amount lies at the limit of the sensitivity of the method.

In terms of the residual concentration of hydrogen sulfide in purified methane is less than 10 ppb.

Example 31

Conducted under conditions similar to example 30, but at a space velocity of 4000 h ^-1 .

The residual concentration of hydrogen sulfide in purified methane is less than 10 ppb.

Example 32

Purify methane containing 0.5% hydrogen sulfide in the presence of the catalyst obtained in example 8, at a temperature of 25-30 ° C and a volumetric feed rate of the gas mixture equal to 1000 h ^-1 .

Figure 1 presents a diagram of the catalytic activity of the catalyst, from which it can be seen that at a low temperature without breakthrough 14,000 vol. gas at 1 vol. catalyst, after which there is a slip. The regeneration of the catalyst by treatment with air at 450 ° C does not lead to the restoration of the original activity. At the same time, if, when the working gas is supplied, the temperature is raised to 170-180 ° C and oxidation of hydrogen sulfide is carried out at this temperature for 2 hours, with a subsequent decrease in temperature to 25-30 ° C, the activity of the catalyst reaches the initial level. The treatment of the catalyst with a working gas mixture at 170-180 ° C promotes two processes: the smelting of sulfur from the surface and, in all likelihood, the oxidation of bound sulfur. As a result, non-stoichiometric iron oxide clusters are again formed on the catalyst surface, which are active components of the oxidative decomposition of hydrogen sulfide to sulfur.

Based on the tests, it was found that the sulfur intensity of the catalyst reaches high values and is equal to 22 g S per 100 g of catalyst.

The following examples illustrate a method for purifying gas mixtures from hydrogen sulfide for a second model mixture corresponding to Klaus process waste and containing 30% water vapor, 0.5; H ₂ S; 0.5% O ₂ , the rest is N ₂ .

Examples 33-37.

Direct oxidation of 1% H ₂ S contained in the vapor-nitrogen mixture in the presence of catalysts is carried out, with different contents of the active component at 250 ° C. Table 3 presents data on the effect of the amount of supported iron on catalytic activity.

Table 3 The effect of Fe content (wt.%) On the conversion (wt.%) And selectivity (wt.%) In the oxidation of hydrogen sulfide to sulfur Fe content Conversion Selectivity Traces 10 ≥99 1,0 40 ≥99 1,5 80 ≥99 2.5 98 97 5,0 ≥99 75

From table 3 it is seen that the amount of deposited iron has a significant impact on the performance of the process. With an increase in the amount of iron to 2.5%, the activity increases, while a further increase in the active component leads to a significant decrease in the selectivity of the process as a result of deep oxidation of hydrogen sulfide to SO ₂ .

Example 38

Direct oxidation of 1% H ₂ S contained in the vapor-nitrogen mixture is carried out. The test time of the catalyst in the presence of a system containing 2.5% Fe is 60 hours.

Figure 2 presents a curve of catalytic activity for the conversion of hydrogen sulfide during the entire test period of the catalyst at various temperatures.

As can be seen from the test chart (figure 2), the best results on the study of the activity of the catalyst were obtained when working in the temperature range of 230-255 ° C, and the temperature of 250 ° C is optimal. At this temperature, the catalyst provides a degree of hydrogen sulfide conversion close to 100%, the selectivity and sulfur yield are 90-95%. At temperatures below 250 ° C, the performance of the catalyst (hydrogen sulfide conversion and sulfur yield) deteriorate over time. When the temperature rises to 250 ° C, the conversion of hydrogen sulfide and sulfur yield again increase and amount to at least 90%, remaining unchanged for 5 hours. The same effect is also observed when the temperature rises from 250 to 270 ° C and its subsequent return to the level of 250 ° C. Thus, the catalyst has a very valuable property - the ability to restore its activity upon returning to optimal process conditions.

We can interpret the results as follows: the optimum temperature for the operation of this catalyst is 250 ° C, below this temperature the inhibitory parameter is the degree of conversion of hydrogen sulfide, which is most likely due to the deposition of sulfur, which blocks active centers, in narrow slit-like pores of the catalyst. Above 250 ° C at high conversion, a significant decrease in sulfur selectivity is observed due to the formation of SO ₂ .

Based on the obtained experimental data, we can draw the following conclusions.

The proposed catalyst is characterized by high selectivity in the temperature range 230-255 ° C and high activity at an optimum temperature of 250 ° C, which compares favorably with many catalytic systems. In addition, the catalyst has the ability to restore and provide a high degree of conversion of hydrogen sulfide, selectivity and sulfur output when returning to optimal conditions.

Examples 39-41.

In order to expand the temperature range of the catalyst, systems based on an activated silica matrix (AMC) are used, in which copper ions were introduced as active components, in addition to iron. The catalysts obtained in examples 9, 17 and 18 by applying acetylacetonate complexes of iron, copper and a mixture of iron and copper complexes. The total amount of active components in the catalyst of example 17 is 2.0%, in which the ratio Cu / Fe is 0.3.

Results on H ₂ S conversion and selectivity at a temperature of 230 ° C. of the purification process obtained in the presence of Fe / AMK catalysts; Fe-Cu / AMK and Cu / AMK are presented in table 4.

Table 4 The results of the conversion of H ₂ S and selectivity at a temperature of 230 ° C N / N H ₂ S Oxidation Examples Catalyst Preparation Examples No. The conversion of H ₂ S, vol.% Selectivity, vol.% 39 9 78 99 40 17 96 99 41 eighteen 44 99

Figure 3, where the conditional contact time _τcont - 0.5 s when loading the catalyst equal to V _cat = 9.0 cm ³ , gives the dependence of the conversion of the process in the presence of the same catalysts at different temperatures, from which it can be seen that the addition to As the active component of copper, it is possible to achieve a systematic increase in the activity of the catalyst with increasing temperature from 220 to 300 ° C without losing its selectivity.

This is an important factor, given the exothermicity of the reaction. With a sharp increase in activity, local overheating can occur, which will inevitably lead to a loss of selectivity.

In this regard, in order to expand the temperature range, it is more advisable to use an iron-copper catalyst. As can be seen from figure 3, the conversion in the presence of a heterometallic system is 98%, the selectivity of 90-100%, at 200-250 ° C. According to the results of laboratory studies, the heterometallic catalyst showed better performance than iron-containing.

Checking the stability of the catalyst at an integrated installation of VNIIGAZ showed that its activity at a temperature of 280 ° C remains almost constant during the entire test period - 60 hours.

Examples 42-43.

Oxidation of 1% hydrogen sulfide contained in a vapor-nitrogen mixture is carried out at a temperature of 250 ° C and in the presence of iron / copper catalysts Cu / Fe — 0.3, with a total amount of active components equal to 2.0%, obtained on the basis of an activated silica matrix and formate and pivalate complexes of iron and copper, according to examples 19 and 20, respectively.

Regardless of the nature of the metal complex precursors, H ₂ S conversion is 98% with a selectivity of 98-99% in sulfur formation.

Thus, in the present invention, an original catalyst is developed based on an activated matrix of silica obtained by etching of natural vermiculite, which significantly exceeds the known analogues and prototype in terms of catalytic activity and selectivity.

So, the proposed catalyst allows the process at a volumetric feed rate of gas mixtures containing hydrogen sulfide to the catalyst equal to 1000-4000 h ^-1 , which is an order of magnitude higher than the feed rate of gas mixtures according to the prototype, with the conversion of hydrogen sulfide equal to 95-99%.

In addition, the proposed catalyst allows the process to be carried out at lower temperatures in comparison with the prototype, and in some cases almost at room temperature, which eliminates the possibility of formation of sulfur dioxide and, in the presence of water vapor, sulfur dioxide, while maintaining high activity and selectivity.

An important feature of the developed catalyst is that it is characterized by high thermal stability and fire resistance. This property compares favorably with catalytic systems based on combustible carbon supports, in the presence of which the process temperature cannot be elevated. Along with this, in the claimed invention, the stabilization factors of the active components are identified and indicated, which determine the high activity and stability of the proposed catalyst in comparison with the prototype. It should also be noted that the depth of conversion of hydrogen sulfide in comparison with the known analogues is a record, and the number of active components is significantly lower. All of the listed features of the catalyst and the method for purifying gas from hydrogen sulfide are fully related to nanotechnology.

It should also be noted the favorable situation associated with large raw materials in Russia and a fairly simple way to obtain a catalyst that does not require the creation of non-standard equipment.

And at the end of a rough estimate, the cost of the proposed catalyst is much lower than the existing industrial ones. This primarily refers to the Klaus process waste treatment catalyst, which is produced by the only company in the world, Komprino (Netherlands).

Claims (5)

1. The catalyst for the deep cleaning of gas mixtures of hydrogen sulfide containing a silica matrix and particles of iron or copper oxide, or a mixture thereof, characterized in that it contains an activated silica matrix obtained by acid etching of natural vermiculite and nanoscale particles of iron or copper oxide, or mixture, in an amount of 0.1-2.5 wt.% in relation to the mass of silica and with a ratio of copper to iron in their mixture equal to 0.3. 2. The method of catalytic deep purification of gas mixtures from hydrogen sulfide by its oxidation with atmospheric oxygen to elemental sulfur, characterized in that gas mixtures with a hydrogen sulfide content of up to 1 vol.% Are used, and the process is conducted in the presence of a catalyst according to claim 1 until the residual sulfur content is more than 1 ppm. 3. The method according to claim 2, characterized in that the process is carried out at a temperature of 25-250 ° C, a space velocity of 1000-4000 h ^-1 . 4. The method according to claim 2, characterized in that when the process is conducted at temperatures below 120 ° C, after passing 14,000 volumes of gas per 1 volume of catalyst, without stopping the supply of reagents, periodic regeneration of the catalyst is carried out. 5. The method according to claim 4, characterized in that for the regeneration of the catalyst, the temperature in the reaction zone is increased to 250 ° C, the oxidation process is carried out at this temperature for 2 hours, after which the temperature is again reduced to room temperature.

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