CN1966143A - Ferric oxide carried palladium catalyst and its preparation method and application - Google Patents

Abstract

The invention relates to a ferric oxide palladium catalyst, wherein said catalyst is palladium catalyst loaded on ferric oxide, while the palladium mass percentage is 0.1-20% of carrier; and it is prepared by deposit method; said catalyst is multifunctional one, which has better low-temperature oxidize activity on CO, H2, CO+H2 and methane, and eliminates CO+H2 at room temperature, while it has high catalysis activity on steam.

Description

Iron oxide supported palladium catalyst and its preparation method and application

field of invention

The invention relates to an iron oxide-supported palladium catalyst, a preparation method and application thereof.

Background technique

Due to their irreplaceable catalytic activity and selectivity, noble metal catalysts play an extremely important role in oil refining, petrochemical and organic synthesis. The precious metal palladium has excellent catalytic performance, and the application of palladium catalysts in the petrochemical industry even exceeds that of platinum catalysts. For example, catalytic reforming in petroleum refining, isomerization and dehydrogenation of alkanes and aromatics, selective hydrogenation in olefin production, and production of organic chemical raw materials such as acetaldehyde, vinyl acetate, and methyl methacrylate. Palladium catalyst is inseparable. In addition, palladium is an excellent catalyst or an important component of catalysts in various organic chemical reactions such as hydrogenation, oxidative dehydrogenation, hydrocracking, coupling, hydroesterification, one-carbon chemistry, and automobile exhaust purification. one-third.

So far, palladium catalyst preparation methods include impregnation method, metal ion vapor deposition method, solvated metal atom impregnation method, ion exchange method, sol-gel method, etc. Co-precipitation method is relatively rare. The palladium catalyst should be dispersed on a suitable carrier. For different reactions, the most researched carriers are activated carbon, aluminum oxide, molecular sieve, zeolite, ceramics, silica gel, etc. The preparation technology of palladium-based catalytic membrane new materials is also a research One of the key points. So far, there has been no report on the use of iron oxide as a carrier for palladium catalysts.

The elimination of trace amounts of carbon monoxide is of great significance to environmental protection and industrial production, such as gas purification and safety assurance. Catalytic oxidation is a simple and effective method. For example, in the industrial synthesis of urea, because the carbon dioxide raw material gas usually contains a small amount of hydrogen, it is not consumed during the synthesis process. If it accumulates too much, it may cause an explosion, and such incidents have occurred. However, a small amount of carbon monoxide in the carbon dioxide feed gas will strongly inhibit the oxidation of hydrogen, and usually only by greatly increasing the reaction temperature can the complete elimination of hydrogen be achieved. Similarly, a large part of the hydrogen-rich feed gas for _H2 fuel cells comes from methanol, reformed gas and steam shift, which often contains trace amounts of CO, which will poison the Pt electrode and reduce the performance of the fuel cell. At the same time, when the submarine is operating underwater, the battery and the engine will produce a small amount of CO during the working process. In order to avoid possible explosions and personnel poisoning, it is necessary to find a way to completely oxidize CO at the lowest possible temperature and select oxidation catalyst.

In recent years, the optimal utilization of natural gas has attracted more and more attention. One of the important uses of natural gas (the main component is methane) is that it can be widely used as clean energy. Due to the incomplete combustion of methane, a small amount of methane is emitted into the atmosphere, causing a greenhouse effect (20 times that of carbon dioxide). Catalytic combustion is an effective technology to curb methane emissions. It is of great scientific significance and practical value to study the complete combustion of methane at the lowest possible temperature, and it is also a very challenging subject. Noble metals palladium, platinum, and rhodium have been extensively studied as catalysts for the low-temperature combustion of methane, among which palladium has always been considered as the catalyst with the best catalytic combustion activity for methane, and Al ₂ O ₃ is also used as a carrier for palladium because of its huge surface area and low price. , but because the Pd/Al ₂ O ₃ catalyst has poor activity below 350°C, and the light-off temperature is low. Therefore, it is necessary to develop catalysts with better activity, so that the light-off temperature and final elimination temperature of methane oxidation can be sufficiently low.

In recent years, the water vapor shift reaction has received renewed attention due to its potential application in proton exchange membrane fuel cells. In addition, because the environmental pollution gas usually contains CO and a certain amount of water, the water vapor shift reaction can consume CO, so this reaction is also of great significance to environmental protection; at the same time, the product _H2 of the shift reaction is still highly efficient. _NOx reducer. The application of supported gold and platinum catalysts in the water vapor shift reaction has received extensive attention and research, and the application of unique palladium catalysts in the water vapor shift reaction is seldom.

Contents of the invention

The object of the present invention is to provide a palladium catalyst supported by iron oxide and its preparation method and application.

The catalyst of the invention is characterized in that the catalyst carrier is iron oxide, the active component is palladium, and the mass percentage of palladium is 0.1% to 20% of the carrier.

The catalyst of the present invention is characterized in that the catalyst is prepared by a co-precipitation method, and the specific process is: at room temperature, the Fe(NO ₃ ) ₃ solution is mixed with the (NH ₄ ) ₂ PdCl ₄ or H ₂ PdCl ₄ solution evenly, and the Add dropwise into the precipitant solution to form co-precipitation, stir to disperse, stand still, filter, wash, dry at room temperature to 100°C, roast at 300-800°C, use 1%-100% hydrogen by volume at 100- Reduction at 500°C.

During the preparation of the catalyst, the precipitating agent used is selected from NaOH, Na ₂ CO ₃ , Li ₂ CO ₃ , KOH or K ₂ CO ₃ .

The catalyst is a multifunctional catalyst, which can be applied to the following aspects:

The catalyst of the invention has high oxidation activity for both CO and _H2 , and can eliminate CO and _H2 that exist alone in the air at a temperature lower than room temperature.

The catalyst of the invention has high oxidation activity to the CO+ _H2 mixed gas, and can co-oxidize the CO+ _H2 mixed gas in the air under the condition of lower than room temperature.

The catalyst of the present invention has a lower light-off temperature and high total oxidation activity for _CH4 , and can fully oxidize _CH4 in the air under the condition of 350°C.

The catalyst of the invention has high catalytic activity for the water vapor shift reaction, and can make the CO conversion reach the equilibrium conversion rate under the condition of 250°C.

The catalyst can remove CO from the air.

An application of an iron oxide-supported palladium catalyst. The carrier of the catalyst is iron oxide, the active component is palladium, and the mass percentage of palladium is 0.1% to 20% of the carrier. It is characterized in that the catalyst is under normal pressure, gas When the space velocity is 5.0×10 ³ ~3.0×10 ⁴ h ^-1 ml/g-catalyst, 0.01~5% CO in the air can be eliminated at -20~50°C.

The catalyst can eliminate H ₂ in the air.

An application of an iron oxide-supported palladium catalyst. The carrier of the catalyst is iron oxide, the active component is palladium, and the mass percentage of palladium is 0.1% to 20% of the carrier. When the rate is 5.0×10 ³ ～3.0×10 ⁴ h ^-1 ml/g-cat, 0.01～5% of H ₂ in the air can be eliminated at -20～20℃.

The catalyst can eliminate the CO+H ₂ mixture in the air.

An application of an iron oxide-supported palladium catalyst, the carrier of which is iron oxide, and the active component is palladium, characterized in that the catalyst has a gas space velocity of 5.0×10 ³ to 3.0×10 ⁴ h ^-1 under normal pressure When ml/g-cat, CO and H ₂ in the mixed gas of CO and H ₂ under aerobic conditions are simultaneously eliminated at -10~60°C, CO accounts for 0.01~5% of the total volume, and H ₂ accounts for 0.01~5% of the total volume %%, oxygen accounts for 1-5% of the total volume.

The catalyst can eliminate CH ₄ in the air.

An application of an iron oxide-supported palladium catalyst. The carrier of the catalyst is iron oxide, the active component is palladium, and the mass percentage of palladium is 0.1% to 20% of the carrier. When the rate is 5.0×10 ³ ～3.0×10 ⁴ h ^-1 ml/g-cat, it can eliminate 0.01～5% of CH ₄ in the air at 350～450℃.

The catalyst can catalyze the water vapor shift reaction.

An application of an iron oxide-supported palladium catalyst. The carrier of the catalyst is iron oxide, the active component is palladium, and the mass percentage of palladium is 0.1% to 20% of the carrier. It is characterized in that the catalyst can be used under normal pressure, gas When the space velocity is 5.0×10 ³ to 3.0×10 ⁴ h ^-1 ml/g-cat, the CO conversion rate in the steam shift reaction reaches the equilibrium conversion rate at 250-350°C.

Compared with prior art, the substantive characteristics that the present invention has are:

1. The catalyst is prepared by co-precipitation method, which can obtain highly dispersed and relatively uniform nano-palladium particles with small scale.

2. The catalyst is a multifunctional catalyst, which can show good catalytic activity for the elimination of CO, H ₂ , CO+H ₂ mixed gas and CH ₄ gas, and also has good catalytic activity for water vapor shift reaction.

3. As a single metal catalyst, the catalyst can realize the co-oxidation of CO+H ₂ mixed gas at room temperature, which cannot be realized by any other single metal catalyst.

4. The presence of water vapor will not reduce the catalytic activity of the catalyst for reactions such as CO, H ₂ , CO+H ₂ mixed gas and complete oxidation of CH ₄ .

5. Compared with the gold catalyst, the catalyst has a longer life under the condition of comparable activity to CO oxidation.

6. The catalyst can be easily combined with the existing honeycomb carrier to prepare a catalyst whose shape and size can be adjusted according to needs.

Detailed ways

Example 1:

Mix 10ml of 1M Fe(NO ₃ ) ₃ solution and 0.05ml of 0.29M H ₂ PdCl ₄ solution evenly, and add dropwise to 30ml (wt) 10% NaCO ₃ solution under strong stirring to form a coprecipitate and adjust the pH The value was 8, continued to stir for 2 hours, stood still for 2.5 hours, filtered, washed with distilled water, left at room temperature for 24 hours to dry the catalyst naturally, calcined at 400°C for 5 hours, and reduced with pure hydrogen at 200°C for 2 hours to obtain catalyst cat 1.

Example 2:

Mix 10ml of 1M Fe(NO ₃ ) ₃ solution and 0.2ml of 0.29M H ₂ PdCl ₄ solution evenly, place in a conical flask, add 20ml of 1M NaOH solution drop by drop under vigorous stirring to form coprecipitation and adjust the pH The value was 7.5, continued to stir for 2 hours, stood still for 2.5 hours, filtered, washed with distilled water, left at room temperature for 24 hours to let the catalyst dry naturally, calcined at 500°C for 5 hours, and reduced with 50% _H2 at 200°C for 2 hours to obtain catalyst cat 2.

Example 3:

Mix 10ml of 1M Fe(NO ₃ ) ₃ solution with 0.2ml of 0.35M (NH ₄ ) ₂ PdCl ₄ solution evenly, place in a conical flask, add 30ml of 1M K ₂ CO ₃ solution drop by drop under vigorous stirring , form a coprecipitate, adjust the pH value to 8, continue to stir for 2h, let stand for 2.5h, filter, wash with distilled water, dry at 50°C for 4 hours, roast at 600°C for 5 hours, and reduce with 10% H ₂ at 300°C for 2 hours to obtain the catalyst cat3.

Example 4:

Mix 5ml of 1M Fe(NO ₃ ) ₃ solution with 0.35M (NH ₄ ) ₂ PdCl ₄ solution evenly, place in a Erlenmeyer flask, add 15ml of 1M KOH solution drop by drop under vigorous stirring to form a co-precipitation, Adjust the pH value to 9, continue stirring for 2 hours, let stand for 2.5 hours, filter, wash with distilled water, dry at 80°C for 4 hours, roast at 500°C for 5 hours, and reduce with 10% H ₂ at 200°C for 2 hours to obtain catalyst cat 4.

Example 5:

In the case that the raw material gas composition is CO: 1.0%; O ₂ : 5.0%; N ₂ balance (volume percentage), and the gas volume space velocity is 2.0×10 ⁴ h ^-1 , use cat 1 at 40°C to reach the residual in the tail gas The amount of CO<10ppm.

Embodiment 6:

When the feed gas composition is CO: 1.0%; O ₂ : 5.0%; N ₂ balance (volume percentage), and the gas volume space velocity is 2.0×10 ⁴ h ^-1 , use cat 3 to reach the tail gas at -20°C Residual CO content <10ppm.

Embodiment 7:

When the feed gas composition is H ₂ : 1.0%; O ₂ : 5.0%; N ₂ balance (volume percentage), and the gas volume space velocity is 2.0×10 ⁴ h ^-1 , use cat 1 to reach the tail gas at 10°C Residual H ₂ amount < 5ppm.

Embodiment 8:

In the case that the feed gas composition is H ₂ : 2.0%; O ₂ : 5.0%; N ₂ balance (volume percentage), and the gas volume space velocity is 2.0×10 ⁴ h ^-1 , use cat 4 to reach the tail gas at -10°C The amount of residual H ₂ in the medium is less than 5ppm.

Embodiment 9:

When the feed gas composition is CO: 1.0%; H ₂ : 1.0%; O ₂ : 1.0%; N ₂ balance (volume percentage), and the gas volume space velocity is 1.0×10 ⁴ h ^-1 , use cat 1 to At 50°C, the residual CO content in the tail gas is <10ppm, and the residual _H2 content is <5ppm.

Example 10:

When the feed gas composition is CO: 1.0%; H ₂ : 2.0%; O ₂ : 2.0%; N ₂ balance (volume percentage), and the gas volume space velocity is 1.0×10 ⁴ h ^-1 , use cat 3 to At 0°C, the residual CO content in the tail gas is <10ppm, and the residual _H2 content is <5ppm.

Example 11:

When the feed gas composition is CH ₄ : 1.0%; O ₂ : 5.0%; N ₂ balance (volume percentage), and the gas volume space velocity is 2.0×10 ⁴ h ^-1 , use cat 2 to reach the tail gas at 400°C Residual CH ₄ amount <10ppm.

Example 12:

When the feed gas composition is CH ₄ : 1.0%; O ₂ : 5.0%; N ₂ balance (volume percentage), and the gas volume space velocity is 2.0×10 ⁴ h ^-1 , use cat 4 to reach the tail gas at 350°C Residual CH ₄ amount <10ppm.

Example 13:

When the feed gas composition is CO: 5.0%, N ₂ dilution (volume percentage), water vapor is passed under anaerobic conditions, and the gas volume space velocity is 2.0×10 ⁴ h ^-1 , use cat 3 to convert CO at 250°C rate reaches the equilibrium conversion rate.

Claims (8)

1, a kind of ferric oxide carried palladium catalyst is characterized in that catalyst carrier is an iron oxide, and active component is a palladium, and palladium quality percentage composition is 0.1%～20% of a carrier.

2, as the said Preparation of catalysts method of claim 1, it is characterized in that catalyst adopts the coprecipitation preparation, detailed process is: under the normal temperature, with Fe (NO ₃) ₃Solution and (NH ₄) ₂PdCl ₄Or H ₂PdCl ₄Solution mixes, stir down and dropwise join in the precipitant solution, form co-precipitation, dispersed with stirring, leave standstill, filter, washing, room temperature to 100 ℃ drying, 300～800 ℃ of roastings are that 1%～100% hydrogen is 100～500 ℃ of reduction down with volumn concentration.

3,, it is characterized in that precipitating reagent is selected from NaOH, Na as the said method of claim 1 ₂CO ₃, Li ₂CO ₃, KOH or K ₂CO ₃

4, a kind of application of ferric oxide carried palladium catalyst, the carrier of this catalyst are iron oxide, and active component is a palladium, and palladium quality percentage composition is 0.1%～20% of a carrier, it is characterized in that this catalyst under normal pressure, gas space velocity is 5.0 * 10 ³～3.0 * 10 ⁴h ^-1During the ml/g-catalyst, eliminate in the air 0.01～5% CO for-20～50 ℃.

5, a kind of application of ferric oxide carried palladium catalyst, the carrier of this catalyst are iron oxide, and active component is a palladium, and palladium quality percentage composition is 0.1%～20% of a carrier, it is characterized in that catalyst under normal pressure, gas space velocity is 5.0 * 10 ³～3.0 * 10 ⁴h ^-1During ml/g-cat, eliminate in the air 0.01～5% H for-20～20 ℃ ₂

6, a kind of application of ferric oxide carried palladium catalyst, the carrier of this catalyst are iron oxide, and active component is a palladium, it is characterized in that catalyst under normal pressure, gas space velocity is 5.0 * 10 ³～3.0 * 10 ⁴h ^-1During ml/g-cat, eliminate CO and H under the aerobic conditions simultaneously for-10～60 ℃ ₂CO in the gaseous mixture and H ₂, CO accounts for 0.01～5% of cumulative volume, H ₂Account for 0.01～5%% of cumulative volume, oxygen accounts for 1～5% of cumulative volume.

7, a kind of application of ferric oxide carried palladium catalyst, the carrier of this catalyst are iron oxide, and active component is a palladium, and palladium quality percentage composition is 0.1%～20% of a carrier, it is characterized in that catalyst under normal pressure, gas space velocity is 5.0 * 10 ³～3.0 * 10 ⁴h ^-1During ml/g-cat, eliminate in the air 0.01～5% CH for 350～450 ℃ ₄

8, a kind of application of ferric oxide carried palladium catalyst, the carrier of this catalyst are iron oxide, and active component is a palladium, and palladium quality percentage composition is 0.1%～20% of a carrier, it is characterized in that catalyst can be under normal pressure, gas space velocity is 5.0 * 10 ³～3.0 * 10 ⁴h ^-1During ml/g-cat, 250～350 ℃ make that the CO conversion ratio reaches equilibrium conversion in the steam transformationreation.