RU2483799C2 - Method of producing catalyst of methane-bearing hydrocarbon steam conversion - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to method of catalyst production. Produced catalyst comprises oxide carrier composed of complex spinel, i.e. Mg [Al, Fe]₂O₄ and active component, i.e. nickel. Proposed method comprises calcination of modified carrier. It differs from known processes in that oxide carrier surface is, first, impregnated with the solution of cerium or lanthanum salts or mix thereof taken in amount of 5.0-10.0 wt % per oxide carrier. Then, nickel is applied to calcine at 500°C so that catalyst containing 10 wt % of nickel is obtained. Note here that prior to impregnation said oxide carrier is subjected to hydrothermal treatment at partial pressure of steam equal to 1.8-2.0 MPa and gradual increase in reaction zone temperature to 800-900°C at heating rate of 10 degree/min.

EFFECT: higher resistance to coke formation and mechanical strength.

4 ex, 2 tbl

Description

The invention relates to a method for producing a catalyst used for the conversion of hydrocarbons into hydrogen and hydrogen-containing gases.

Currently, most of the large-scale production of hydrogen and hydrogen-containing gases is based on the conversion of hydrocarbons and, above all, natural gas. In this case, the main technological process is catalytic steam conversion. Technologically, the method is well developed and allows the process to be carried out at high pressures and temperatures.

A further increase in the economic efficiency of hydrogen production units is possible in two main directions: an increase in catalyst productivity and a decrease in the vapor / carbon ratio. Work in such modes requires the use of catalysts combining high activity and resistance to carbonization.

Given these requirements, the search for catalytic compositions that differ in structure-forming additives, promoters in the active component and the nature of the active component itself continues.

In [1] (SU No. 743716, 03/06/1980) a method for the preparation of a catalyst by impregnating alumina with solutions of nitrate salts, followed by drying and calcination of a catalyst mass at 900-1000 ° C, is described. In order to increase activity and resistance to carburization, the catalyst is additionally impregnated with a 5-10% potassium hydroxide solution.

The introduction of alkali metals into the catalyst makes it possible to inhibit carbon formation reactions, but due to their volatility under conditions of steam reforming, this positive effect decreases with time and can also adversely affect the course of the process.

A known catalyst for methane steam conversion [2] (US No. 7.767.619, 08/03/2010), the carrier of which is calcium aluminate, on which up to 30% of the active component (Ni, Co, Pt, etc.) and up to 35% of the promoter ( La, Ce, Y, etc.).

The catalyst is prepared by mixing aluminum hydroxide with cement, water and graphite. The prepared mixture is tabletted, autoclaved for 10 hours and then calcined for 8 hours at a temperature of 400 ° C. Next, the carrier is impregnated with a solution of La (NO ₃ ) ₃ or Ce (NO ₃ ) ₃ and calcined for 5 hours at a temperature of 1250-1350 ° C.

Tests of the catalyst at low temperature (538 ° C) showed high resistance to its carbon deposits.

The disadvantages of the method include multi-stage preparation and the high temperature of calcination of the finished catalyst. The use of various calcium aluminates increases the stability of the catalysts to the formation of nickel spinel, the accumulation and crystallization of which are one of the main causes of catalyst deactivation. The disadvantage is the decrease in heat resistance with increasing concentration of calcium aluminates in the carrier.

A rather large group consists of catalysts in which noble metals (Ag, Pt, Pd, Au) are used as the active component.

So in [3] (US No. 4.060.498, 11.29.1977) a catalyst preparation method was described, according to which silver is used as the active component to suppress carbon deposition on it when working with low H ₂ O / C ratios.

In [4] (US No. 6.958.310, 10.25.2005) and in [5] (WO 02066371, 08/29/2002) a method for producing a catalyst is described where platinum, palladium, and iridium are used as the active element.

In [6] (US No. 5.997.835, 12/07/1999), the process of catalytic steam reforming without carbon formation on a Ni-containing catalyst, including 0.01-10.0% gold, was described as a promoter. The catalyst is prepared by impregnating the support with solutions of nickel nitrate and gold tetraaminonitrate. After drying the catalyst particles, it is loaded into the reactor and activated at 350-400 ° C in a hydrogen medium.

The disadvantages of these catalysts include their high cost.

The known method [7] (US No. 5.679.614, 10.21.1997), according to which the preparation of the catalyst consists of the following steps:

a) the preparation of the catalyst carrier by mixing oxides of 65% γ-Al ₂ O ₃ , 5% La ₂ O ₃ and 10% MgO, followed by calcination at 700-800 ° C for 6 hours;

b) impregnation of the carrier with solutions of nitric salts of Cr and Ni;

c) adding a 1 N solution of nitric acid to the mixture, molding the catalyst granules and calcining the latter at a temperature of 800 ° C for 6 hours.

The final composition of the obtained catalyst is 15% Ni, 10% MgO, 5% Cr, 5% La, 65% Al ₂ O ₃ .

The catalyst, according to the authors, has high activity and mechanical strength in the conditions of steam conversion of paraffin hydrocarbons and high resistance to carbon deposits.

The disadvantages of the method include its multi-stage and high temperature calcination of the obtained catalyst granules.

In [8] (US No. 5.268.346, December 7, 1993), a catalyst support was prepared by mixing aqueous solutions of Ce (NO ₃ ) ₃ and Al (NO ₃ ) ₃ with a 2 N solution of NH ₄ OH. The filtered precipitate was dried at 120 ° C for 24 hours and then calcined at 800 ° C for 3 hours.

The resulting carrier is impregnated with an aqueous solution of ruthenium chloride, dried and reduced with hydrogen at a temperature of 700 ° C for 3 hours. The catalyst showed good resistance to carbon deposition during steam reforming at a temperature of 600 ° C.

The closest technical solution to the proposed one is a method for producing a steam reforming catalyst for methane-containing hydrocarbons described in [9] RU No. 2375114, 12/10/2009, according to which a method for preparing a catalyst based on a mixed oxide with a spinel structure obtained from vermiculite ore is developed. The carrier is obtained by etching vermiculite with dilute hydrochloric acid (5-7% solution) at 50-70 ° C, followed by separation of the etching solution and processing it with 2 N NaOH solution. When etching vermiculite in an acidic solution passes up to 60% wt. (based on initial vermiculite) non-empirical inclusions of aluminum, magnesium and iron ions. When treated with alkali, these ions are released in the form of a precipitate, which is formed into granules and then calcined at a temperature of 850 ° C for 2 hours. Nickel in an amount of 10% wt. introduced into the catalyst by impregnation using Ni (NO ₃ ) ₂ · 6H ₂ O.

Get the catalyst containing the carrier in the form of a complex spinel type Mg [Al, Fe] ₂ O ₄ when the mass ratio of oxides of magnesium, iron and aluminum, equal to 1: 0.6: 1, and Nickel.

In the presence of the catalyst thus obtained, methane conversion reaches an equilibrium value in the first two hours of operation at a process temperature of 800 ° C. However, at 600 ° C the content of carbon deposits during the test was 1.6%, which with an increase in the duration of the process can lead to a significant decrease in the activity of the catalyst.

The disadvantages of the described method include the low resistance of the catalyst to coke formation and the low mechanical strength of the latter.

The task of the invention is to increase the stability of the catalyst to coke formation and increase its mechanical strength.

The solution to this problem is achieved by the fact that in the method for producing a steam reforming catalyst for methane-containing hydrocarbons containing an oxide support in the form of a complex spinel of the Mg [Al, Fe] ₂ O _{4 type} and an active component nickel, including calcining the modified support, the surface of the oxide support is first applied by impregnation with a solution of cerium or lanthanum salt or a mixture thereof, taken in an amount ensuring their content equal to 5.0-10.0% by weight. calculated on the oxide carrier, and then Nickel is applied and calcined at a temperature of 500 ° C to obtain a catalyst containing 10.0% wt. nickel. To increase the mechanical strength of the oxide support, the latter is subjected to hydrothermal treatment before impregnation at a partial pressure of water vapor equal to 1.8-2.0 MPa, and a gradual increase in temperature in the reaction zone to 800-900 ° C with a heating rate of 10 deg / min.

In order to increase the resistance of the catalyst to coke formation, before the stage of applying the nickel-containing active component, 5.0% of cerium or lanthanum or a mixture thereof is applied to the surface of the oxide carrier with a total amount of modifying components of 5.0-10%.

The invention is illustrated by the following examples.

Example 1

An oxide support in the form of a complex spinel of the Mg [Al, Fe] ₂ O _{4 type} with a mass ratio of magnesium, iron and aluminum oxides of 1: 0.6: 1 is obtained according to the procedure described in RU No. 2393016, 06/27/2010.

Vermiculite of the Kovdorsky deposit of a fraction of 0.5 mm grade “150” is used as a feedstock.

Etching is carried out in one stage using 7% and 3.5% hydrochloric acid. Processing the initial vermiculite with acids is carried out at a temperature of 50-60 ° C for 6 hours with constant stirring. The volume ratio of vermiculite: acid is 1: 3 in the case of samples 1n, 2n and 1: 4 in the case of sample 3n.

Solutions containing iron, magnesium, aluminum ions are used to prepare the catalyst support by coprecipitation of metal hydroxides with 2 N alkali solution of NaOH at room temperature and a variable pH of 9.50.

The resulting precipitate of metal hydroxides is separated from the mother liquor by squeezing on a Buchner funnel using a Diagonal fabric and washed with distilled water, heated to 40-50 ° C, until the washings react to chlorine ions (silver nitrate test).

The prepared hydroxide precipitates are formed in the form of balls with a diameter of 3-4 mm, first dried in air for 48 hours, then in an oven at a temperature of 120 ° C for 6 hours.

Next, the carrier samples are subjected to hydrothermal treatment (GTO) at a partial pressure of water vapor of 1.8-2.0MPa and a gradual increase in temperature in the reaction zone to 800-900 ° C with a heating rate of 10 deg / min. The mechanical strength of the carrier before and after the TRP is determined by the method in accordance with GOST 21560.2-82.

Data on the change in strength before and after the TRP are shown in table 1.

Table 1 No. T, ° C Partial pressure H ₂ O, MPa Partial pressure N ₂ , MPa Strength, MPa before the TRP after the TRP 1n 800 1.8 0.2 0.20 0.92 2n 800 1.9 0.1 0.21 1.00 3n 800 2.0 - 0.20 0.90 1n 900 1.8 0.2 0.20 0.98 2n 900 1.9 0.1 0.21 1.10 2n 900 2.0 - 0.18 0.95

Example 2

The preparation of Ni-La-containing catalyst is carried out by impregnation. As sources of lanthanum, an acetic acid salt, La (OAc) ₃ · 1.5H ₂ O, is used. The preparation of the catalyst is carried out in two stages.

In the first stage carry out the application of 5.1% wt. La by weight of the carrier. Based on the values of moisture capacity and the required amount of introduced lanthanum, the concentration of an aqueous solution of lanthanum acetate is calculated. A portion of the granular support is placed in a crystallizer, poured with an excess of a solution of lanthanum salt, incubated for two hours. Then the impregnated granules are separated from the excess solution, dried in air in an oven at 120 ° C. for 6 hours, and calcined in a muffle furnace at a temperature of 500 ° C. for 6 hours.

At the second stage, 10.0% Ni (based on the weight of the catalyst) is applied. At the end of the deposition of nickel and drying of the samples in air and in an oven, calcination is carried out in a muffle furnace at a temperature of 500 ° C for 5 hours.

The finished catalyst contains: Nickel 10.0% wt .; lanthanum 4.4% wt .; the carrier is the rest.

Example 3

Prepare a carrier, as in example 1, on which cerium is applied in an amount of 5.1% wt. by weight of the carrier. As the source of cerium, the acetic acid salt Ce (OAc) ₃ · 1.5H ₂ O is used. The impregnation is carried out by the method described in example 2, followed by applying 10.0% Ni (by weight of the catalyst).

The finished catalyst contains: Nickel 10.0% wt .; cerium 4.4% wt .; the carrier is the rest.

Example 4

Preparation of Ni-Ce-La-containing catalyst

Prepare the carrier, as in example 1, on which cerium is sequentially applied in an amount of 5.4% wt. by weight of the carrier, then lanthanum in an amount of 5.4% wt. by weight of the carrier. The cerium source is used as the acetic acid salt of Ce (OAc) ₃ .1,5H ₂ O, as the lanthanum source - La (OAc) ₃ .1,5H ₂ O. The impregnation is carried out in the manner described in Example 2, followed by application of 10% wt. Ni (by weight of the catalyst).

The finished catalyst contains: Nickel 10.0% wt .; cerium 4.4% wt .; lanthanum 4.4% wt .; the carrier is the rest.

Testing of catalyst samples during methane steam reforming

The proposed catalysts were tested in a steam methane conversion process. The experiments were carried out in a reactor made of heat-resistant steel with an internal diameter of 30 mm. In all experiments, 20 cm ^{3 of the} tested catalysts were loaded into the reactor.

As a comparison catalyst, a catalyst was used according to the method [9] containing 10% wt. Ni.

The catalysts prepared by the method described in examples 2, 3 and 4, and the comparison catalyst were tested in the process of steam conversion of methane under a pressure of 2.0 MPa, a temperature of 720 and 600 ° C, the ratio of steam / carbon = 2: 1 and 1: 1 by volume and space velocity of 6000 h ^-1 .

The activity of the catalyst was determined as the ratio of the observed degree of conversion of methane (X) to equilibrium (X _p ) during the conversion of methane with water vapor.

In the unloaded samples, the amount of carbon deposited was determined by the method according to GOST 2408.1-95.

The test results are shown in table 2.

table 2 The results of experiments on the conversion of methane Time hour T, ° C steam / s by volume The composition of the dry gas,% vol. X * X / X _p ** Contents carbon,% wt. P in the system, MPa H ₂ With CO ₂ CH ₄ Catalyst 10.0% Ni - 4.4% Ce 10 721 2 55.8 6.9 9.6 27.7 0.38 0.86 2.0 twenty 723 2 56.1 8.1 9,4 26,4 0.40 0.91 2.0 thirty 724 2 56.4 9.1 8.3 26.1 0.40 0.91 2.0 40 722 2 57.7 7.4 9.2 25.7 0.39 0.90 2.0 fifty 606 one 34.0 1,2 6.6 58.4 0.11 0.71 2.0 60 610 one 31.3 1,0 5.9 61.8 0.10 0.65 2.0 70 600 one 30.1 1,2 7.1 61.6 0.11 0.71 0.26 2.0 Catalyst 10.0% Ni - 4.4% La 10 721 2 56.3 5.3 8.9 29.5 0.32 0.73 2.0 twenty 723 2 57.7 7.1 9.2 26.0 0.38 0.86 2.0 thirty 720 2 59.6 7.4 9.1 23.9 0.41 0.93 2.0 40 724 2 58.9 7.2 9,4 24.5 0.41 0.93 2.0 fifty 606 one 30,2 1,2 7.1 61.5 0.12 0.77 2.0 60 596 one 31.1 1.3 5.3 62.3 0.09 0.60 2.0 70 600 one 30,0 1,2 7.2 61.6 0.11 0.73 0.18 2.0 Catalyst 10.0% Ni - 4.4% La - 4.4% Ce 10 720 2 59.3 5.7 9.1 25.8 0.36 0.85 2.0 twenty 723 2 58.9 7.2 9.2 24.7 0.40 0.92 2.0 thirty 722 2 56.4 9.2 8.3 26.1 0.40 0.92 2.0 40 720 2 59.5 7.3 9.2 24.0 0.41 0.93 2.0 fifty 595 one 31,0 1.4 5.2 62,4 0.09 0.60 2.0 60 600 one 30,2 1.3 6.4 62.1 0.11 0.73 2.0 70 585 one 30,0 1,2 7.4 61,4 0.12 0.76 0.20 2.0 The catalyst is 10.0% Ni [comparative prototype] 10 730 2 59,4 5.7 9.0 25.9 0.36 0.82 2.0 twenty 723 2 57.9 7.5 8.2 26,4 0.37 0.84 2.0 thirty 724 2 58.7 7.4 9.2 24.7 0.41 0.94 2.0 40 730 2 60.5 6.2 9.8 23.5 0.40 0.91 2.0 fifty 596 one 21.0 1,2 6.6 58.4 0,07 0.55 2.0 60 587 one 19.1 1,0 5.9 61.8 0.06 0.51 2.0 70 583 one 19.3 0.4 4.6 75.7 0.06 0.51 1.75 2.0 * the observed degree of conversion of methane (X); ** the ratio of the observed degree of conversion of methane (X) to equilibrium (X _p )

As can be seen from the experimental results, the catalyst exhibits a rather high activity at a temperature of 720 ° C and a ratio of H ₂ O: CH ₄ = 2: 1. The concentration of reaction products quickly reaches values close to equilibrium, and remains stable over the duration of the run.

A decrease in the reaction temperature to 600 ° С and a decrease in the ratio of Н ₂ О: С = 1: 1 in order to determine the catalyst resistance to coke formation showed that the catalyst resistance to coke formation at low temperature is in the order Ni-La / support> Ni-Ce / support > Ni / carrier.

Used sources

1. SU No. 743716, 03/06/1980.

2. US No. 7.767.619, 08/03/2010.

3. US No. 4.060.498, 11.29.1977.

4. US No. 6.958.310, 10.25.2005.

5. WO 02066371, 08/29/2002.

6. US No. 5.997.835, 12/07/1999.

7. US No. 5,679.614, 10.21.1997.

8. US No. 5.268.346, 12/07/1993.

9. RU No. 2393016, 06/27/2010.

Claims (1)

A method of producing a steam reforming catalyst for methane-containing hydrocarbons containing an oxide support in the form of a complex spinel of the Mg [Al, Fe] ₂ O _{4 type} and the active component is nickel, including calcining the modified support, characterized in that the surface of the oxide support is first applied by impregnation with a salt solution cerium or lanthanum or a mixture thereof, taken in an amount ensuring their content of 5.0-10 wt.% calculated on the oxide carrier, and then nickel is applied and calcined at a temperature of 500 ° C to obtain catalysis an atom containing 10.0 wt.% nickel, the oxide carrier being subjected to hydrothermal treatment before impregnation at a partial pressure of water vapor equal to 1.8-2.0 MPa and a gradual increase in temperature in the reaction zone to 800-900 ° C at a rate heating 10 degrees / min.