CN1216793C - Catalyst for water transfer reaction and method for converting carbon monoxide and water to hydrogen and carbon dioxide - Google Patents

Abstract

The present invention provides a catalyst suitable for converting carbon monoxide and water into hydrogen and carbon dioxide (water shift reaction), comprising a metal oxide carrier, and 0.1-10% platinum and 0-5% rhenium supported on the metal oxide carrier, based on the weight of the metal oxide carrier. The metal oxide carrier comprises copper oxide; aluminum oxide; and a metal oxide selected from zinc oxide, chromium oxide and magnesium oxide. The present invention also discloses a method for reducing the carbon monoxide content of a hydrogen-rich recombinant gas.

Description

Catalyst for water shift reaction and method for converting carbon monoxide and water into hydrogen and carbon dioxide

                      

The present invention is concerned with providing a process for the conversion of carbon monoxide and water into hydrogen and carbon dioxide (water transfer reaction), especially with regard to the catalysts used therein.

Background technique

Polymer Electrolyte Membrane Fuel Cell (PEMFC) is very likely to be used in stationary household power generation systems and electric vehicles in the future, and the fuel required to supply the PEMFC system is a hydrogen-rich gas (H ₂ concentration > 35%). Generally, the CO concentration of the hydrogen-rich recombined gas produced by the recombination reaction of hydrocarbons is about 8-15%, and the CO concentration of the hydrogen-rich recombined gas must be reduced to 1%, and then through selective oxidation to reduce the CO concentration of the reformed gas to below 20ppm. The traditional WGS catalyst is Cu-ZnO/Al ₂ O ₃ . Its biggest disadvantages are narrow reaction temperature range, need for activation, inaccessibility to air and heat resistance. Due to these disadvantages, the application of traditional Cu-ZnO/Al ₂ O ₃ to the fuel reformer system of household stationary fuel cell power generation system will cause great inconvenience in operation.

Therefore, every catalyst research unit or company actively wants to develop a WGS reaction catalyst with convenient operation, such as the U.S. patent (US 6,238,640) of Idemitsu Kosan developed Cu-MO-Al ₂ O ₃ (M is Zn, Cr, Mg), Japan Panasonic’s European patent (EP 1,161,991) developed Pt-M/ZrO ₂ (M is Re, Sc, Pr), Toyota’s European patent (EP 1,184,445) developed Pt-M/TiO ₂ (M is Al, Si , P, S, V), and Nextech have developed Pt/CeO ₂ -ZrO ₂ catalysts. They all claim that these catalysts are not afraid of contact with oxygen and have high catalytic WGS reactivity. But in fact, the catalyst of above-mentioned patent research and development has its shortcoming respectively, and the activity of catalyst research and development as Idemitsu Kosan is not high, and the catalyst noble metal content of the research and development of Nextech, Matsushita Electric and Toyota is high (Pt concentration 3～12wt% of the patent embodiment ), the catalyst synthesis cost is higher.

Contents of Invention

An object of the present invention is to provide a catalyst which can be used in the process of converting carbon monoxide and water into hydrogen and carbon dioxide (water transfer reaction), which has the advantages of high conversion rate and low manufacturing cost.

Another object of the present invention is to provide a method for converting carbon monoxide and water into hydrogen and carbon dioxide.

Another object of the present invention is to provide a method for reducing the carbon monoxide content and increasing the hydrogen content in a hydrogen-rich reformed gas.

A catalyst suitable for converting carbon monoxide and water into hydrogen and carbon dioxide according to the content of the present invention in order to achieve the above-mentioned purpose of the invention, comprising a metal oxide carrier, the metal oxide carrier includes copper oxide; aluminum oxide; and A metal oxide selected from zinc oxide, chromium oxide and magnesium oxide, characterized in that it contains 0.1-10% platinum (Pt), preferably 0.5-5% Pt, loaded on the metal oxide carrier, And 0-5% rhenium (Re), preferably 0.1-3% Re, based on the weight of the metal oxide support.

The present invention also discloses a method for converting carbon monoxide and water into hydrogen and carbon dioxide, comprising contacting a hydrogen-rich feed containing carbon monoxide and water vapor with the above-mentioned catalyst of the present invention at 200-500°C.

Preferably, the metal oxide carrier in the catalyst of the present invention comprises copper oxide; aluminum oxide; and zinc oxide, wherein the metal oxide carrier contains 25 to 55% copper, based on the weight of the metal oxide carrier .

Preferably, the hydrogen-rich feed used in the method of the present invention is hydrogen-rich reformed gas formed by reforming a hydrocarbon.

Preferably, the hydrogen-rich feed used in the method of the present invention contains more than 30 mol% hydrogen, and the molar ratio of H ₂ O to CO is 2-10.

Description of drawings

Figure 1 is a plot of the CO conversion rate of the catalyst versus the reaction gas inlet temperature when the _H2O /CO molar ratio is 3, wherein the catalyst of Example 1 of the present invention is represented by black dots, and the catalyst of Comparative Example 1 is represented by hollow circle dots , the catalyst of Comparative Example 2 is represented by a solid diamond point.

Figure 2 is a plot of the CO conversion rate of the catalyst versus the reaction gas inlet temperature when the molar ratio of H ₂ O/CO is 6, wherein the catalyst of Example 1 of the present invention is represented by a hollow rhombus point, and the catalyst of Example 2 is represented by a black circle , the catalyst of Example 3 is represented by a hollow circle point, and the catalyst of Comparative Example 3 is represented by a triangle point.

Figure 3 is a plot of the CO conversion rate of the catalyst versus the reaction gas inlet temperature when the _H2O /CO molar ratio is 4, wherein the catalyst in Example 2 of the present invention is represented by a black dot before aging, and after aging (400°C , 20 hours) are represented by open circle points, compared with three catalysts before aging are represented by solid triangle points, after aging (400°C, 20 hours) are represented by open triangle points.

Figure 4 is a plot of the CO conversion rate of the catalyst versus the reaction gas inlet temperature when the molar ratio of _H2O /CO is 6, wherein the catalyst of Example 2 of the present invention is represented by a black circle, and the catalyst of Comparative Example 4 is represented by a triangle point, The catalyst of Comparative Example 5 is represented by square dots.

Detailed ways

The present invention discloses a catalyst for WGS reaction, which can avoid the disadvantages of traditional Cu-ZnO/Al ₂ O ₃ , and the catalytic activity of the catalyst for WGS reaction is better than or comparable to that developed by the aforementioned Japanese Matsushita Electric, Nextech and Toyota. In addition, the noble metal concentration of the catalyst of the present invention must be reduced in order to reduce the cost of catalyst synthesis. The following table lists the comparison result of the embodiment of preceding case and a preferred embodiment of this case invention:

ToyotaEP 1184445 Panasonic Electric EP 1161991 Idemitsu KosanUS 6238640 this invention Catalyst composition Pt-M/TiO ₂ M: Al, Si, P, S and V Pt-M/ZrO ₂ M: Re, Sc, Pr Cu-M/ _Al2O3M : Zn, _Cr , Mg Pt-Re/Cu-Zn-Al precious gold content 3-12% by weight 3% by weight --- 1-4% by weight reactivity high high middle high Access to oxygen Can Can Can Can synthetic cost high high Low middle

The present invention can be further understood by means of the following examples, which are provided for illustrative purposes only and are not intended to limit the scope of the present invention.

Example 1

Weigh 34.2g Cu(NO ₃ ) ₂ .3H ₂ O, 92.7g Al(NO ₃ ) ₃ .9H ₂ O and 30.6g Zn(NO ₃ ) ₂ .6H ₂ O and dissolve them in 1500ml of deionized water. Under stirring, 28% ammonia water was added dropwise until the pH value of the solution was 7.5. After stirring at room temperature for 2 hours, the gel formed in the solution was filtered out and washed with water, dried at 120°C for 12 hours, and calcined at 500°C for 5 hours to obtain Cu/Al ₂ O ₃ -ZnO, and its weight composition ratio Cu:Al ₂ O ₃ :ZnO=30:42:28.

Add an appropriate volume of Pt(NH ₃ ) ₂ (NO ₂ ) ₂ solution containing 0.2 grams of Pt to 20 grams of Cu/Al ₂ O ₃ -ZnO powder by incipient wetness impregnation method, mix evenly, and dry at 120°C for 12 hours. Calcined at 400°C for 2 hours to obtain a Pt/Cu/Al ₂ O ₃ -ZnO catalyst, wherein the concentration of platinum is 1% by weight.

Mix the prepared Pt/Cu/Al ₂ O ₃ -ZnO powder with aluminum oxide gel (alumina sol) at a weight mixing ratio of 9 to 1, during which an appropriate amount of water is added to adjust the solid content, and the slurry is adjusted after grinding. Viscosity, then the slurry is coated on a ceramic honeycomb carrier with a diameter of 2 cm and a length of 2 cm with 400 cells/in 2 (cells/in ² ), and then dried at 120°C (12 hours) and fired at 450°C (2 hours) to prepare a monolith honeycomb catalyst (monolith honeycomb catalyst). The amount of catalyst attached to each monolithic honeycomb catalyst is about 1-2 grams.

Comparative example 1

Repeat the steps of Example 1 to prepare a monolithic honeycomb catalyst, but replace the Pt/Cu/Al ₂ O ₃ -ZnO powder with Cu/Al ₂ O ₃ -ZnO powder that does not contain Pt in Example 1. Repeat steps.

Comparative example 2

Weigh 114g Cu(NO ₃ ) ₂ .3H ₂ O, 102g Al(NO ₃ ) ₃ .9H ₂ O and 309g Zn(NO ₃ ) ₂ .6H ₂ O in 3000ml of deionized water, stir at room temperature, 28% ammonia water was added dropwise until the pH value of the solution was 7.5. After stirring at room temperature for 2 hours, the precipitate formed in the solution was filtered out and washed with water, dried at 120°C for 12 hours, and calcined at 500°C for 5 hours to obtain the Cu/Al ₂ O ₃ -ZnO catalyst, and its weight composition ratio Cu:Al ₂ O ₃ :ZnO=23.4:10.8:65.8. Then repeat the coating step of Example 1 with this Cu/Al ₂ O ₃ -ZnO powder to prepare a monolithic honeycomb catalyst.

Using a traditional fixed-bed reaction system to test the activity of the catalyst in catalyzing the WGS reaction, take the above-mentioned honeycomb catalyst and put it into a quartz reaction tube with an inner diameter of 2.2 cm, and use an electric furnace to control the inlet temperature of the reaction gas. The reaction gas is: H ₂ 50.2%, CO9 .4%, CO ₂ 12.2%, H ₂ O 28.2%, H ₂ O/CO molar ratio is 3, reaction gas space velocity (GHSV) is 7000 hours ^-1 . Fig. 1 is the conversion rate of WGS reaction catalyzed by the catalysts of Example 1 and Comparative Examples 1 and 2 at different temperatures. The experimental data in Figure 1 fully shows that the addition of platinum can greatly improve the catalytic ability of the Cu/Al ₂ O ₃ -ZnO catalyst for the WGS reaction and increase the CO conversion rate.

Example 2:

Weigh 151.02g Cu(NO ₃ ) ₂ .3H ₂ O, 214.31g Al(NO ₃ ) ₃ .9H ₂ O and 71.0g Zn(NO ₃ ) ₂ .6H ₂ O in 3000ml deionized water, stir at room temperature 28% aqueous ammonia was added dropwise until the pH value of the solution was 7.5. After stirring at room temperature for 2 hours, the precipitate formed in the solution was filtered out and washed with water, dried at 120°C for 12 hours, and calcined at 500°C for 5 hours to obtain a weight ratio of Cu:Al ₂ O _{3 :} ZnO=45:33 : 22 Cu/Al ₂ O ₃ -ZnO. After Cu/Al ₂ O ₃ -ZnO is ground into powder, an appropriate volume of Pt(NH ₃ ) ₂ (NO ₂ ) ₂ solution containing 0.2 g of Pt and 0.2 g of Re in NH ₄ ReO ₄ solution are mixed by incipient wetness impregnation method Diluted to 20 grams of Cu/Al ₂ O ₃ -ZnO powder and mixed evenly, dried at 120°C for 12 hours and calcined at 400°C for 2 hours to obtain the Pt-Re/Cu/Al ₂ O ₃ -ZnO catalyst, in which platinum The concentration of rhenium is 1% by weight, and the concentration of rhenium is 1% by weight. Then repeat the coating step in Example 1 with this Pt-Re/Cu/Al ₂ O ₃ -ZnO powder to prepare a monolithic honeycomb catalyst. The amount of catalyst attached to each monolithic honeycomb catalyst is about 2 grams.

Example 3

A monolithic honeycomb catalyst was prepared by repeating the steps of Example 1, but the Pt-Re/Cu/Al ₂ O ₃ -ZnO powder contained 3% by weight of Pt and 1% by weight of rhenium. The amount of catalyst attached to each monolithic honeycomb catalyst is about 2 grams.

Comparative example 3

Weigh 151.02g Cu(NO ₃ ) ₂ .3H ₂ O, 214.31g Al(NO ₃ ) ₃ .9H ₂ O and 71.0g Zn(NO ₃ ) ₂ .6H ₂ O in 3000ml deionized water, stir at room temperature 28% aqueous ammonia was added dropwise until the pH value of the solution was 7.5. After stirring at room temperature for 2 hours, the precipitate formed in the solution was filtered out and washed with water, dried at 120°C for 12 hours, and calcined at 500°C for 5 hours to obtain a weight ratio of Cu:Al ₂ O _{3 :} ZnO=45:33 : 22 Cu/Al ₂ O ₃ -ZnO. Then repeat the coating step of Example 1 with this Cu/Al ₂ O ₃ -ZnO powder to prepare a monolithic honeycomb catalyst.

Also use the traditional fixed bed reaction system to test the activity of the catalyst to catalyze the WGS reaction. Take the above-mentioned honeycomb catalyst and put it into a quartz reaction tube with an inner diameter of 2.2 cm, and use an electric furnace to control the inlet temperature of the reaction gas. The reaction gas is: H ₂ 33.8%, CO 5.4%, CO ₂ 10.2%, H ₂ O 32.4%, H ₂ O/CO molar ratio is 6, reaction gas space velocity (GHSV) is 6000 hours ^-1 . Fig. 2 is the conversion rate of WGS reaction catalyzed by the catalysts of Example 1, Example 2, Example 3 and Comparative Example 3 at different temperatures. The experimental data in Figure 2 fully show that the addition of rhenium can improve the catalytic ability of Pt/Cu/Al ₂ O ₃ -ZnO catalyst for WGS reaction, improve the conversion rate of CO, and the Pt-Re/Cu/Al ₂ O ₃ -ZnO catalyst can catalyze WGS The conversion rate of the reaction for CO is more significantly surpassed that of Cu/Al ₂ O ₃ -ZnO.

The traditional fixed-bed reaction system was also used to test the activity of the aged catalyst to catalyze the WGS reaction. The monolithic honeycomb catalysts of Example 2 and Comparative Example 3 were aged at 400°C for 20 hours, and then placed in a quartz reaction tube with an inner diameter of 2.2 cm for WGS reaction. The inlet temperature of the reaction gas was controlled by an electric furnace. The reaction gas was: H ₂ 47.3%, CO 8.1%, CO ₂ 12.2%, H ₂ O 32.4%, H ₂ O/CO molar ratio is 4, reaction gas space velocity (GHSV) is 6000 hours ^-1 . Fig. 3 shows the conversion rate of WGS reaction catalyzed by the monolithic honeycomb catalysts of Example 2 and Comparative Example 3 under the above reaction conditions without aging and after aging. The experimental data in Figure 3 shows that the CO conversion rate of the Pt-Re/Cu/Al ₂ O ₃ -ZnO catalyst can still be maintained at a high level after aging at 400°C for 20 hours, which is significantly higher than that of Cu/Al ₂ O ₃ -ZnO , showing that the addition of Pt-Re can effectively improve the catalytic properties of Cu/Al ₂ O ₃ -ZnO for WGS reaction.

Comparative example 4

Weigh an appropriate amount of zirconia powder and add 3 wt% Pt and 1 wt% Re by incipient wetness impregnation method, based on the weight of zirconia powder, dry at 120°C for 12 hours, and bake at 400°C for 2 hours to obtain Pt-Re / ZrO ₂ powder. Mix Pt-Re/ZrO ₂ powder with alumina gel binder, the weight mixing ratio is 9 to 1, and add an appropriate amount of water to adjust the solid content, adjust the viscosity of the slurry after grinding, and then coat the slurry A monolithic honeycomb catalyst was obtained by drying at 120°C for 12 hours on a ceramic honeycomb carrier with a diameter of 2 cm and a length of 2 cm with 400 cells/in ² , and then calcining at 400°C for 2 hours. The amount of Pt-Re/ _ZrO attached to each monolithic honeycomb catalyst is about 2 g.

Comparative Example 5

Weigh an appropriate amount of Pt/CeO ₂ -ZrO ₂ powder purchased from Nextech (containing 2% by weight of Pt, based on the weight of CeO ₂ -ZrO ₂ powder) and bond with 10% by weight of alumina gel (alumina sol) Mixing agent, adding appropriate amount of water to adjust the solid content, adjusting the viscosity of the slurry after grinding, and then coating the slurry on a 400 cells/in ² ceramic with a diameter of 2 cm and a length of 2 cm The honeycomb carrier was dried at 120°C for 12 hours and calcined at 400°C for 2 hours to obtain a monolithic honeycomb catalyst. The amount of Pt/CeO ₂ -ZrO ₂ attached to each monolithic honeycomb catalyst is about 2 grams.

Similarly, the traditional fixed bed reaction system was used to test the activity of the catalyst to catalyze the WGS reaction. The honeycomb catalysts of the above-mentioned Example 2 and Comparative Examples 4 and 5 were placed in a quartz reaction tube with an inner diameter of 2.2 cm, and the inlet of the reaction gas was controlled by an electric furnace. Temperature, reaction gas: H ₂ 33.8%, CO 5.4%, CO ₂ 10.2%, N ₂ 18.2%, H 2 O 32.4%, _{H 2 O} /CO molar ratio is 6, reaction gas space velocity (GHSV) for 6000 hours ^-1 . Fig. 4 is the conversion rate of the WGS reaction catalyzed by the catalysts of Example 2, Comparative Example 4 and Comparative Example 5 at different temperatures. The experimental data in Figure 4 shows that the highest CO conversion rate of the Pt-Re/Cu/Al ₂ O ₃ -ZnO catalyst is equivalent to that of the catalysts in Comparative Examples 4 and 5, but the reaction temperature of the Pt-Re/Cu/Al ₂ O ₃ -ZnO catalyst is lower and its noble metal content is lower than that of the catalysts of Comparative Examples 4 and 5. These experimental data fully demonstrate the excellent performance of Pt-Re/Cu/Al ₂ O ₃ -ZnO in catalyzing the WGS reaction.

Claims (10)

1. one kind is applicable to the catalyzer that carbon monoxide and water is changed into hydrogen and carbonic acid gas, comprises a metal oxide carrier, and this metal oxide carrier comprises copper oxide; Aluminum oxide; And being selected from zinc oxide, a metal oxide of chromated oxide and magnesium oxide is characterized in that comprising 0.1～10% platinum and 0.1～5% rhenium that is carried on this metal oxide carrier, is benchmark with the weight of this metal oxide carrier.

2. catalyzer as claimed in claim 1, wherein this metal oxide carrier comprises copper oxide; Aluminum oxide; And zinc oxide, wherein this metal oxide carrier comprises 25～55% bronze medals, is benchmark with the weight of this metal oxide carrier.

3. catalyzer as claimed in claim 1 or 2, wherein this catalyzer comprises 0.5～5% platinum, is benchmark with the weight of this metal oxide carrier.

4. catalyzer as claimed in claim 3, wherein this catalyzer comprises 0.1～3% rhenium, is benchmark with the weight of this metal oxide carrier.

5. one kind changes into the method for hydrogen and carbonic acid gas with carbon monoxide and water, comprises a rich hydrogen charging that will contain carbon monoxide and water vapor and contacts in 200～500 ℃ with catalyzer;

Described catalyzer is to comprise a metal oxide carrier, and this metal oxide carrier comprises copper oxide; Aluminum oxide; And being selected from zinc oxide, a metal oxide of chromated oxide and magnesium oxide also comprises 0.1～10% platinum and 0.1～5% rhenium that is carried on this metal oxide carrier, is benchmark with the weight of this metal oxide carrier.

6. method as claimed in claim 5 wherein should the hydrogen-enriched recombinant gas of richness hydrogen charging for forming by the hydrocarbon of recombinating.

7. as claim 5 or 6 described methods, wherein should the charging of richness hydrogen contain the above hydrogen of 30 moles of %, and H ₂O is 2～10 to the mol ratio of CO.

8. method as claimed in claim 5, wherein the metal oxide carrier of this catalyzer comprises copper oxide; Aluminum oxide; And zinc oxide, wherein this metal oxide carrier comprises 25～55% bronze medals, is benchmark with the weight of this metal oxide carrier.

9. as claim 5 or 8 described methods, wherein this catalyzer comprises 0.5～5% platinum, is benchmark with the weight of this metal oxide carrier.

10. method as claimed in claim 9, wherein this catalyzer comprises 0.1～3% rhenium, is benchmark with the weight of this metal oxide carrier.

Images