The catalyst for sulfur from acid gases and the method of its preparation

 

(57) Abstract:

The invention relates to the production and use of catalysts used in obtaining sulfur from acid gases according to the method Claus, in particular to catalysts of the so-called protective layer serving to protect from oxygen catalysts of the base layer in the reactor installations Claus and the reactor tail gas treatment. The catalyst contains alumina and iron oxides, and optionally oxides of magnesium and silicon, and phosphates of these metals in the following ratio of components in terms of oxides, wt.%: FeO, Fe2O3the 2.0 - 14; SiO21 - 1,5; MgO 0.3 to 0.5; P2O50,5 - 1,0, Al2O3- the rest. The process of preparation of the catalyst comprises a mechanical mixture of aluminum hydroxide with an oxide or hydroxide of iron, oxides of silicon and magnesium, followed by plasticization of the mixture when you add 20 - 30% aqueous solution of phosphoric acid, the formation of granules and their heat treatment. The ratio of initial components is in terms of oxides, g/mol: Al2O3: Fe2O3: SiO2: MgO : P2O5= 1 : (0,013 - 0,107) : (0,019 - 0,028) : (0,009 - 0,015) : (0,004 - 0,007). In this case, the heat treatment of the catalyst assests the exposure 2 - 3 h, and then with a speed of 2 to 3oC/min, in the temperature range 120 - 550oaged 3 to 4 h and cooled at a speed of 4 - 5oC/min 2 S. and 2 C.p. f-crystals, 1 table.

The invention relates to the production and use of catalysts used in the production of sulfur from acid gases according to the method Claus, in particular to catalysts of the so-called protective layer serving to protect from oxygen catalysts of the base layer in the reactor installations Claus and tail gas treatment carried out at a temperature below the dew point of sulfur. The invention can be used in oil, gas, petrochemical, metallurgical and other industries.

As a catalyst in the Claus reactors and reactor tail gas treatment using active alumina (D. A. Abaskuliev, N. A. Hajiyev, Y. F. Vysheslavtsev. Modern processes and catalysts for sulfur. KBO. INF. Niigaam, ser. "Preparation and processing of gas and gas condensate", M. 1988, vol. 2). This catalyst is available, cheap and extremely effective in the primary reaction of sulfur:

2H2S+SO2_ 3S+2H2O,

and adverse reactions of hydrolysis of the carbon-cerusico aluminosilicate catalysts is their instability with respect to oxygen, in the presence of which they sulfatide, so that the alumina goes into the sulfate or sulfite of aluminum with the loss of the porous structure and catalytic activity.

As to avoid the presence of oxygen in the process gas, it's almost impossible to prevent sulfation of aluminum oxide in the Claus reactors and reactors purification using the so-called protective catalysts.

Known protective catalysts are of two types: extracting oxygen from the gas and oxygen-consuming.

The closest to the technical nature of the claimed invention is a catalyst obtained by impregnation of the granules of aluminum oxide sulfates of iron or Nickel, followed by drying and calcination of the pellets (patent Germany N 2617649, class B 01 D 53/36, 1980).

The main disadvantages of the known catalysts are the low specific surface area (up to 250 m2/g) and pore volume (up to 0.3 cm3/g) and low activity in the primary reaction Claus, in particular in the process tail gas treatment, because the catalyst provides only the consumption of oxygen and is not involved in obtaining sulfur. This reduces the performance of the reactors, and on ostanovivshiy proposed mixed catalyst comprising alumina and oxide of iron, additionally comprising oxides of silicon and magnesium, and phosphates of these metals with the following content of components in terms of oxides, wt. FeO, Fe2O32,0 14; SiO21 1,5; MgO 0,3 0,5; P2O50,5 1,0; Al2O3the rest of it. Compounds of divalent or trivalent iron can be interconnected in any proportion, but, as a rule, is dominated by the latter, including all of the iron may be in the trivalent state. Crystal structure of aluminum oxide, prevailing in the catalyst is essentially a-Al2O3.

The catalyst was prepared by mechanical mixing aluminum hydroxide with an oxide or hydroxide of iron by adding oxides of magnesium and silicon, and then carry out the plasticization of the mixture when you add 20 to 30% aqueous solution of phosphoric acid, forming granules and heat treatment. Mainly the heat treatment of the catalyst is carried out in the linear heating rate 1 2oC/min in the temperature range 20 120oC, followed by exposure 2 to 3 hours, then at a speed of 2 3oC/min in the temperature range 120 550oaged 3 to 4 h and cooled at a speed of 4 to 5oC/min

Unlike from the through surface and porosity and, as a result, maintains the activity of the main reaction Claus and sulfur-retaining capacity in the process tail gas treatment.

Introduction to the catalyst composition of magnesium oxide prevents sulfation of aluminum oxide and provides work sustainability catalyst, also in the process of preparation of the catalyst portion of the magnesium oxide enters phosphate Mg3(PO4)2that helps increase the activity of oxides and sulfates of iron in the reaction: H2S + 3/2 O2_ SO2+ H2O and hence increased the selectivity of action of the catalyst as a whole.

In addition, SiO2and MgO are structure-forming additives that improve the texture of the catalyst, its thermal stability and mechanical strength.

Processing of oxides of phosphoric acid leads to a decrease in their basicity, respectively, to reduce the chemisorption of SO2and increase flow rate in the presence of oxygen reactions: MgO + SO3-L MgSO4. It was shown that treatment with 1% solution of phosphoric acid leads to a decrease of the adsorption of SO2at 340oC on Al2O3from 0.19 mmol/g to 0.04 mmol/g and Fe2O3(hematite) with 0.06 mmol/g p is a developed system of meso - and macropores, that is particularly important to ensure the effectiveness of the catalyst in the process tail gas treatment.

The preparation of the catalyst by mechanical mixing of components ensures the formation of the active phase in the volume of the granules of the catalyst. The oxides of iron, magnesium and silicon is introduced into the aluminum hydroxide at the stage of plasticization of the latter. Due to prolonged mixing is the distribution of components throughout the volume of the plasticized mass. Each of the components is available for reacting substances free of catalytically active surface. Thus the alumina pores remain free for reaction Claus and holding the condensed sulfur in the tail gas treatment. This allows the proposed catalyst to work not only for removal of oxygen from the gas, but also to act as a catalyst for Claus as in any of the reactors of units Claus and the reactor tail gas treatment.

In addition, the preparation of alumo-ferrum catalyst by the method of mixing the components can significantly simplify the production technology, to avoid repeating the steps of drying and Procurator composition in terms of oxides, wt. Fe2O32,0 14,0; SiO21,0 1,5; MgO 0,3 0,5; P2O50,5 1,0; Al2O3the rest, is prepared by the method of mixing in a Z-shaped mixer load aluminum hydroxide with a humidity of 60 to 70% of the oxide or hydroxide of iron, silicon oxide in the form of white carbon black and magnesium oxide in a predetermined ratio of the components. The mixing is carried out for 10 to 20 minutes Then the mixture plastificator for 30 to 40 minutes at a temperature of 50 60oC and stirring with the addition of an aqueous solution of phosphoric acid with a concentration of 20 to 30% of the Ratio of initial components in terms of oxides, g/mol: Al2O3Fe2O3SiO2MgO P2O51 (0,013 0,107) (0,019 0,028) (0,009 - 0,015) (0,004 0,007).

The mass formed by extrusion into pellets of cylindrical or spherical shape.

The obtained granules are subjected to heat treatment, for which they at first be dried, and then calcined at a linear heating rate of 1 to 2oC/min in the temperature range 20 120oC with a holding time of 2 to 3 hours, at a speed of 2 3oC/min in the temperature range 120 150oC with a holding time of 3 to 4 hours and cooled at a speed of 4 to 5oC/min

Thus obtained catalyst has a specific surface is of talesfore, containing in terms of oxides, wt. Fe2O32,0; SiO21,2; MgO And 0.4; P2O5- 0,7; Al2O395,7 was prepared as follows: in a Z-shaped mixer sequentially loaded 300 g of aluminum hydroxide with a moisture content of 65.0% 1,43 g of iron oxide, 0.86 silicon oxide and 0.29 magnesium oxide. Mixing was carried out for 20 min, then the mixture was plastifitsirovanie for 40 min adding 3.4 ml of a 20% aqueous solution of phosphoric acid. This was also drying the mass to a moisture content of 50% the mixing Ratio in terms of oxides, g/mol: Al2O3Fe2O3SiO2MgO P2O51 0,013 0,025 0,012 0,006.

The mass was extrudible forming into granules of cylindrical shape. The obtained pellets were dried for 3 hours at a temperature of 120oC with the speed of raising temperature in the range of 20-120oC 2oC/min, progulivali at 550oC with a holding time of 5 h and with the speed of raising temperature in the range 120-550oC 3oC/min and cooled at a speed of 4oC/min

Physico-chemical, mechanical and performance characteristics are given in the table.

Example 2. A sample of catalyst containing in terms of oxides, wt. Fe2O31 is led aluminum was added 11,48 g of iron oxide, 0.98 silicon oxide and 0.33 of magnesium oxide. Mixing was carried out for 20 min, then the mixture was plastifitsirovanie for 40 min adding 2,53 ml of 30% aqueous solution of phosphoric acid at a temperature of 50oC. the mixing Ratio in terms of oxides, g/mol: Al2O3Fe2O3SiO2MgO P2O51 0,107 0,024 0,012 0,006.

The mass was extrudible forming into granules of cylindrical shape. The obtained granules were dried for 2 hours at a temperature of 120oC with the speed of raising temperature in the range of 20-120oC 1oC/min

Physico-chemical, mechanical and performance characteristics shown in the table.

Example 3. A sample of catalyst containing in terms of oxides, wt. Fe2O37,0; SiO21,5; MgO Of 0.5; P2O5- 1,0; Al2O390,0 was prepared according to example 1 with the difference that the aluminum hydroxide was added 5.34 g of iron oxide, 1.15 silicon oxide and 0.38 magnesium oxide and 5.1 ml of a 20% aqueous solution of phosphoric acid. The mixing ratio in terms of oxides, g/mol: Al2O3Fe2O3SiO2MgO P2O51 0,049 0,028 0,015 0,007.

Physico-chemical, mechanical and operational characteristics when37,0; SiO21,0; MgO 0,3; P2O5- 0,5; Al2O391,2 was prepared according to example 1 with the difference that the aluminum hydroxide was added at 5.27 g of iron oxide, 0.75 silicon oxide and 0.23 magnesium oxide and 2,53 ml of 20% aqueous solution of phosphoric acid. The mixing ratio in terms of oxides, g/mol: Al2O3Fe2O3SiO2MgO P2O51 0,049 0,019 0,009 0,004.

Physico-chemical, mechanical and performance characteristics shown in the table.

The catalysts prepared in examples 1 to 4 were tested for activity in the reactions of oxygen consumption and Klaus in terms of the 2nd reactor:

Temperature 220oC

The contact time 3

Pressure naturally

The composition of the gas, about. H2S 5,0; SO22,5; O2500 ppm; H2O 30,0; N2the rest.

The tests were carried out in a laboratory setup with a flow reactor with a diameter of 15 mm and a volume of catalyst layer 25 ml. Test was carried out for 3 h In the process of constantly testing were selected gas samples for analysis. Analysis chromatography. The results of the analysis used to calculate the degree of conversion of SO2and H2S. the Results are shown in the table.

Efficiency R>TemperatureoC 130

The contact time, with 3

Pressure naturally

The composition of the gas, about. H2S 0,5; SO20,25; O2100 ppm; H2O 30,0; N2the rest.

The tests were carried out at pilot plant reactor with a diameter of 100 mm and a volume of catalyst layer 5 l the Tests were carried out to reduce the degree of conversion is below 90% Then the test was stopped and the reactor was switched on regeneration in a stream of nitrogen at a temperature of 350oC. Melted in the process of regeneration of sulfur were collected, weighed and counted sulfur-retaining capacity of the sample as the ratio obtained in the process of cleaning gas sulfur by weight or volume of the catalyst. The results are shown in the table.

The data presented in the table show that the proposed catalyst within changes in the composition, as claimed in the claims, has advantages over the prototype according to the achieved value of specific surface area (21% higher), total porosity (45% higher) and activity in oxygen consumption (degree of conversion of O2increases in comparison with the prototype 32 40% ). Especially significant is the effect of increasing careercast (3 to 4 times) in the process tail gas treatment.

Catalysts with content companion in quantities exceeding the upper limit, does not correspond to the achievement of the additional effect and is not justified from an economic point of view.

The catalyst according to the invention can not only effectively protect the main catalyst in the Claus reactors and reactor tail gas treatment from sulfation in the presence of oxygen, but also simultaneously serve as a catalyst in the Claus process and the sulfur adsorbent in the reactor tail gas treatment.

1. The catalyst for obtaining sulfur from acid gases containing oxides of aluminum and iron compounds, characterized in that compounds of iron catalyst containing the oxides, the catalyst further comprises an oxide of magnesium and silicon, and phosphates of metals in the following ratio of components in terms of oxides, wt.

FeO, Fe2O32,0 14

SiO21,0 1,5

MgO 0,3 0,5

P2O50,5 1,0

Al2O3Else

2. The method of preparation of a catalyst containing alumina and iron compounds, including the formation of granules and subsequent heat treatment, characterized in that before forming perform mechanical mixture of aluminum hydroxide is% aqueous solution of phosphoric acid.

3. The method according to p. 2, characterized in that the ratio of initial components is in terms of oxides, g/mol: Al2O3Fe2O3SiO2MgO P2O51:(0,013

0,107):(0,019 0,028):(0,009 0,015):(0,004 0,007).

4. The method according to p. 2, characterized in that the heat treatment of the catalyst is carried out in the linear heating rate 1 2 deg./min in the temperature range 20 120oWith subsequent exposure 2 to 3 hours, then at a speed of 2 3 degrees./min in the temperature range 120 550oC, aged 3 to 4 h and cooled at a speed of 4 to 5 degrees./minutes

 

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