Catalyst and method for producing hydrogen-rich gas mixture of dimethyl ether

 

(57) Abstract:

The invention relates to the reaction of steam reforming of dimethyl ether in order to obtain hydrogen-rich gas mixture which can be used in hydrogen energy, in particular, as a fuel for fuel cells for various applications, including fuel cells installed on mobile media. Task to be solved by the present invention is directed, is the development of new catalytic systems having high catalytic activity, selectivity and stability in relation to the steam reforming of dimethyl ether (DME), as well as the development of the process of obtaining from DME gas mixture enriched in hydrogen, using this catalytic system. The task is solved by providing a catalyst comprising a mechanical mixture of catalyst hydration ether and a copper-containing catalyst for steam reforming of methanol, and the catalyst for the hydration of the ester is Si - or P-, M - or W-heteroalicyclic or their Na-, Mg-, Cu - and Zn-salt deposited on SiO2or Al2O3in the amount of 1-50 wt.%, the rest is media SiO2or Al2O3and how p is the journey of a specified catalyst. The proposed catalysts offer the possibility of varying chemical composition. Their use allows to reduce the operating temperature of the process and is carried out at a ratio of steam/DME equal to the stoichiometric (N2O/DME=3), which has important technological importance. 2 S. and 3 C.p. f-crystals, 4 PL.

The invention relates to a catalytic method implementing the reaction of steam reforming of dimethyl ether in order to obtain hydrogen-rich gas mixture which can be used in hydrogen energy, in particular, as a fuel for fuel cells for various applications, including fuel cells installed on mobile media. Fuel cells are being considered as a real alternative to the known sources of energy on mobile tools, such as internal combustion engines and batteries. In this case, the fuel for fuel cells is hydrogen or hydrogen-rich gas mixture.

There are two main method of supplying hydrogen to the fuel cell (J. V. Ogden, M. M. Steinbugler, T. G. Kreutz, A Comparison of Hydrogen, Methanol and Gasoline as Fuels for Fuel Cell Vehicles: Implications for Vehicle Design and Infrastructure D is de he is in a compressed state. The disadvantage of this method is the necessity of using equipment operating at high pressures, which adds cost and complexity to the process and increases the consumption of plants. In the second scheme, the hydrogen produced in the catalytic chemical process of the carriers of hydrogen, such as hydrocarbons or methanol, directly on a mobile vehicle.

It is known that the process of catalytic steam reforming of methanol is considered as the main way to obtain hydrogen-rich gas mixture directly on a mobile vehicle with the purpose of supply of the fuel element. This process is carried out in the presence of catalysts containing, for example, palladium (Iwasa, N.; Kudo, S.; Takahashi, H.; Masuda, S.; N. Takezawa, Hight Selective Supported Pd Catalysts for Steam Reforming of Methane, Catalysis Letters, vol. 19 (1993) N 2-3, p. 211 to 216), or copper and zinc (Wang D.; Ma L; Jiang C. J.; Trimm, D. L.; Wainwright, M. S.; Kirn, D. H., The Effect of Zinc Oxide in Raney Copper Catalysts on Methanol Synthesis, Water Gas Shift and Methanol Steam Reforming Reaction, Studies In Surface Science And Catalysis, vol. 101 (1996), p. 1379-1387; Idem, R. O., bakhshi for N. N., Production of Hydrogen from Methanol over Promoted Coorecipitated Cu-Al Catalysts: The Effects of Varies Promotors and Catalyst Activation Methods, Ind. Eng. Chem. Res., vol. 34 (1995), p. 1548-1557).

It is known that dimethyl ether, as well as methanol, can be obtained by direct synthesis from synthesis gas (Roucudies in Surface Science and Catalysis, vol. 107 (1997), p. 117-125), and the synthesis of dimethyl ether is economically more beneficial than the methanol synthesis (T. Shikada , Ohno Y., Ogava T. Ono, M., Mizuguchi Tomura Fujimoto K. Direct Synthesis of Dimethyl Ether from Synthesis Gas, Studies in Surface Science and Catalysis, vol. 119 (1998), p. 515-520).

Given this, and the fact that the physico-chemical properties of DME are similar to the properties of reduced petroleum gas (I. Dybkjaer, Hansen J. B., Large Scale Production of Alternative Synthetic Fuel from Natural Gas, Studies in Surface Science and Catalysis, vol. 107 (1997), p. 99 - 118), the process of steam reforming of dimethyl ether with the aim of producing hydrogen on a mobile vehicle to power a fuel cell is a serious alternative to the process of steam reforming of methanol.

Known two-stage method for producing, from DME hydrogen-rich gas mixture (U.S. Pat. N 5626794, C 07 C 01/00, 1997). In the first stage is a catalytic steam reforming of dimethyl ether on the catalysts containing copper and zinc, in elemental form and not containing alkali metals (first stage) with the formation of hydrogen and carbon monoxide. In the second stage catalytic steam conversion of carbon monoxide on the catalyst containing the oxides of copper, zinc, chromium or iron. The resulting two-stage process gas mixture used for combustion tion energy. The disadvantage of this method are receiving at the first stage of the diluted gas mixture through the use of an inert gas diluent (nitrogen), high temperature flow of the first stage (above 350oC) and a low degree of conversion of dimethyl ether, which at temperatures below 350oC does not exceed 88%.

The closest is the one way to obtain hydrogen-rich gas mixture by reacting dimethyl ether and water vapor from the reaction of CH3OCH3+ 3H2O=2CO2+6H2in the presence of a mechanical mixture of two catalysts:

(1) catalyst hydration ether, which represents an aluminosilicate ZSM in the hydrogen form or SIRAL 5, and (2) the catalyst for the decomposition of methanol (U.S. Pat. US N 5837217, C 01 B 03/02, 17.11.98).

The disadvantage of this method and catalyst is that the complete conversion of dimethyl ether is achieved at a sufficiently high temperature 300oC and with the increased ratio of H2O/DME=4:1 as compared with the stoichiometric H2O/DME= 3. This reduces the overall efficiency of the process steam reforming of dimethyl ether to hydrogen gas.

The challenge aimed nationally, selectivity and stability in relation to the steam reforming of DME, as well as the development of the process of obtaining of the dimethyl ether gas mixture enriched in hydrogen, using this catalytic system, which will reduce the operating temperature and the water vapor content at the outlet of the reactor and thereby improve the efficiency of the process.

The problem is solved by development of a catalyst to obtain a hydrogen-rich gas mixture by reacting dimethyl ether and water vapor, consists of a mechanical mixture of catalyst hydration ether and a copper-containing catalyst for steam reforming of methanol, and the catalyst for the hydration of the ester is Si - or P-, Mo - or W - heteroalicyclic or their Na-, Mg-, Cu - or Zn-salt deposited on SiO2or Al2O3in the amount of 1-50 wt.%, the rest is media SiO2or Al2O3.

The task is also solved by providing a method of obtaining a hydrogen-rich gas mixture by reacting dimethyl ether and water vapor in the presence of a mixture of catalyst hydration ether and a copper-containing catalyst for steam reforming of methanol, the catalyst hydration ether used ether and steam reforming of methanol is used with a weight ratio of from 1:5 to 5:1. The reaction is carried out at inlet 150 up to 450oC, 1-100 atmospheres and a molar ratio water / dimethyl ether H2O /DME 2-10.

The process proceeds according to the reaction:

CH3OCH3+H2O=2CH3OH; (1)

CH3OH+H2O=3H2+CO2(2)

CO2+H2=CO+H2O (3)

total reaction:

CH3OCH3+3H2O=2CO2+6H2. (4)

A distinctive feature of the proposed catalytic system consists of a mechanical mixture of the two catalysts is the fact that as DME hydration catalyst used heteroalicyclic (CCP) or their salts supported on a carrier; as a catalyst for steam reforming of methanol - known copper-containing catalysts, such as Cu-Zn-Al catalyst for methanol synthesis (U.S. Pat. RF N 2055639, B 01 J 37/08, bull. N 7 18.06.93), Cu-Zn-AI (Cr) or Cu-Mg-catalysts steam reforming WITH (U.S. Pat. RF N 2118910, 01 J 37/08, bull. N 26, 26.03.97), (Ed. St. USSR 223069, bull. N 33, 1978).

Composition and methods for producing copper-containing catalysts described in the above patents.

Hydration catalyst ether have the following composition:

H4[Si(P)] [Mo(W)]12O40or their Na-, Mg-, Cu-, Zn-salts media, such as SiO2and Al2O3.

The invention is illustrated by the following examples describing the preparation methods of catalysts and the results of their testing in the reaction of steam reforming of dimethyl ether.

Steam reforming of dimethyl ether is carried out in the installation of the flow type in glass or quartz reactor with a diameter of 8 mm on the sample mechanical mixture of two catalysts 3 g at a ratio of water/DME = 3:1-5:1, contact time 1200-5000 h-1, 200-350oC and 1-5 ATM. In hanging the weight ratio of copper-containing catalyst to the catalyst on the basis of the CCP or their salts vary in the range of 1/5-5/1.

Hydration catalyst ether is prepared by impregnation of carriers aqueous solution of the CCP or their salts according to capacity with a subsequent heat treatment in air at 250 to 300oC.

Example 1. Catalyst - kremneva.liliya CCP/Al2O3prepare:

a) 44.6 g Si-W-CCP dissolve when heated in water so that the solution volume was 60 ml;

b) 100 g of the powder (1-2 mm) -Al2O3with the surface 200 m2/g and a pore volume of 0.6 cm3/g are impregnated with stirring the resulting solution, then dried at 25oC during the Example 2. Catalyst - kremneva.liliya CCP/SiO2prepare:

a) 15 g of Si-W-CCP dissolve when heated in water so that the volume of the solution was 50 ml;

b) 10 g of the powder (0.5-1.0 mm) SiO2impregnate with stirring, 15 ml of the obtained solution, then dried at 25oC for 20 hours, at 100oC for 4 hours and calcined in air at 300oC for 4 hours.

Example 3. Catalyst - phosphormolybdenum CCP/Al2O3prepare:

a) 20 g of P-Mo SBC dissolve when heated in water so that the volume of solution was 65 ml;

b) 10 g of the powder (1-2 mm) -Al2O3impregnate with stirring, 6 ml of the obtained solution, then dried at 25oC for 20 hours, at 100oC for 4 hours and calcined in air at 250oC for 4 hours. Then the catalyst was re-impregnated and calcined. Such processing is repeated 3 times.

Example 4. The catalyst is a magnesium salt cremaboldrini CCP/SiO2prepare:

a) 25 g of Si-W-CCP dissolve when heated in water so that the volume of the solution was 40 ml, then to this solution was added 0.56 g of MgO and the mixture is heated until complete dissolution of the oxide;

b) 10 g Evora, further dried at 25oC for 20 hours, at 100oC for 4 hours and calcined in air at 300oC for 4 hours.

Example 5. Steam reforming of dimethyl ether in the hydrogen-rich mixture is carried out in a flow reactor at a mechanical mixture consisting of Cu-Mg-oxide catalyst for steam reforming and CO catalyst hydration of the ester prepared according to the method described in example 1, taken with the weight ratio of 3/4, respectively. The results are shown in table 1.

Example 6. In the process, similar to the one described in example 5, DME converted into hydrogen-rich mixture to a mechanical mixture of Cu-Zn-Al catalyst for methanol synthesis catalyst prepared by the method described in example 2. The weight ratio of these catalysts in a mixture of 1/1. The results are shown in table 2.

Example 7. In the process, similar to the one described in example 5, DME converted into hydrogen-rich mixture to a mechanical mixture of Cu-Zn-Al catalyst for the conversion of CO and the catalyst prepared by the method described in example 3. The weight ratio of these catalysts in a mixture of 1/1. The results are shown in table hydrogen mixture to the mechanical mixture of Cu-Mg-oxide catalyst for the conversion of CO and the catalyst, prepared according to the method described in example 4. The weight ratio of these catalysts in a mixture of 1/1. The results are shown in table 4.

These examples demonstrate methods of making catalysts, and high activity, selectivity and stability of the catalysts.

The proposed catalysts offer the possibility of varying chemical composition. The use of the proposed catalysts allows to reduce the operating temperature of the process and is carried out at a ratio of steam/dimethyl ether equal to the stoichiometric (H2O/DME = 3), which has important technological importance.

1. Catalyst to obtain a hydrogen-rich gas mixture by reacting dimethyl ether and water vapor, consists of a mechanical mixture of catalyst hydration ether and a copper-containing catalyst for steam reforming of methanol, characterized in that the catalyst for the hydration of the ester is Si - or P - Mo - or W - heteroalicyclic or their Na-, Mg-, Cu - or Zn-salt deposited on SiO2or Al2O3.

2. The catalyst p. 1, characterized in that the composition of the catalyst hydration ether ASS="ptx2">

3. The way to obtain hydrogen-rich gas mixture by reacting dimethyl ether and water vapor in the presence of a mixture of catalyst hydration ether and a copper-containing catalyst for steam reforming of methanol, characterized in that as a catalyst for the hydration of the ester used Si - or P - Mo - or W-heteroalicyclic or Na-, Mg-, Cu - or Zn-salt supported on a carrier.

4. The method according to p. 3, characterized in that the hydration catalyst ether and steam reforming of methanol is used with weight ratio of 1 : 5 to 5 : 1.

5. The method according to p. 4, characterized in that the reaction is carried out at 150 - 450oC, 1 100 MPa, and a molar ratio water/dimethyl ether H2O/DME 2 - 10.

 

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