CN101352685B - Supported type nickel catalyst for producing hydrogen from decomposition of ammonia and preparation method - Google Patents

Abstract

A supported nickel catalyst for ammonia decomposition to produce hydrogen, the active component is Ni, and the carrier is silicon oxide, aluminum oxide or titanium oxide; the mass percentage of the active component is 1-50%. The preparation steps are as follows: soluble nickel salt, pH regulator, precipitant, carrier and deionized water are prepared into a suspension; the suspension is heated to 70-110° C. for 60-300 minutes; After -30°C, filter, wash with water, and filter; dry at 80-120°C for 18-24 hours, and bake at 400-900°C for 2-6 hours; Activate at -900°C for 3-5 hours, and then reduce to make a supported nano-nickel catalyst. The catalyst of the invention has high activity to the ammonia decomposition reaction, can be applied to the process of producing COx-free hydrogen by ammonia decomposition, and can also be used in the purification treatment process of various ammonia-containing gases.

Description

A kind of preparation method of supported nickel catalyst for ammonia decomposition hydrogen production

technical field

The invention relates to a catalyst for ammonia decomposition to produce COx-free hydrogen.

The present invention also relates to a method for preparing the above-mentioned catalyst.

The present invention also relates to the application of the above-mentioned catalyst in the hydrogen production reaction of ammonia decomposition.

Background technique

At present, the research and development of proton exchange membrane fuel cell (PEMFC) using hydrogen as fuel is attracting more and more attention from enterprises and government departments. However, the purity, storage and transportation of hydrogen have become one of the bottlenecks in the development of hydrogen sources for fuel cells. Hydrogen produced from carbon-containing substrates inevitably contains COx (x=1-2) gas that reduces the life of the proton membrane fuel cell; at the same time, the storage of hydrogen requires the use of materials with high hydrogen storage capacity or liquid hydrogen-containing fuels. As a chemical hydrogen storage medium, ammonia not only has a high hydrogen content (about 17.6%), but also its decomposition products are hydrogen and nitrogen, and nitrogen has no negative impact on the electrodes of PEMFC. Compared with methanol hydrogen production technology, the price of ammonia decomposition hydrogen production process is lower. In addition, ammonia is easy to liquefy (the liquefaction pressure of ammonia at 20°C is only 0.8MPa), and it is convenient for storage and transportation. Therefore, the on-site or vehicle-mounted ammonia decomposition hydrogen production process can provide COx-free high-purity hydrogen at a relatively low temperature, and solve the technical problem of difficult transportation and storage of hydrogen. Therefore, the production of hydrogen from ammonia (NH ₃ ) without carbon atoms will be one of the attractive technical approaches before the emergence of high hydrogen storage materials for commercial applications and long-term anti-CO poisoning fuel cell electrodes.

At present, the catalysts for hydrogen production from ammonia decomposition mainly have active centers of Fe, Ni, Ru, Co and metal nitrides, and the supports are mostly MgO, TiO ₂ , Al ₂ O ₃ , activated carbon, porous carbon nanotubes, and magnesium-aluminum spinels. Stone, super alkali, etc. In the study of these catalysts, noble metal catalysts with Ru as the active center showed higher catalytic activity (WO0187770A1, WO0208117A1, CN1456491A, CN1528657A, CN1712132A). However, as a noble metal catalyst, the high price of Ru is a fatal flaw in its practical industrial application in the future. It is of great practical significance to carry out research on nickel-based catalysts with abundant reserves, low price and high activity for ammonia decomposition.

CN1772614A discloses a method for preparing nanoscale Ni/Al ₂ O ₃ and Ni/La-Al ₂ O ₃ catalysts. The preparation process of the catalyst is to make the nitrate of Ni and Al into aqueous solution or ethanol solution, then use the aqueous solution or ethanol solution of ammonium carbonate or ammonium bicarbonate as precipitant to make Ni and Al co-precipitate, then dry, roast and reduce The ammonia decomposition catalyst was prepared. The catalyst prepared by this method has high activity for ammonia decomposition. However, the disadvantage of the co-precipitation method is that the precursor is easily included in the support oxide, and it is also difficult to control the pore structure of the catalyst.

Contents of the invention

The object of the present invention is to provide a supported nickel catalyst for ammonia decomposition to produce hydrogen.

Another object of the present invention is to provide a method for preparing the above catalyst.

The invention can prepare a loaded nano-nickel catalyst with high specific surface area, high dispersion, high stability and high activity.

In order to achieve the above object, the present invention provides a supported nickel catalyst for ammonia decomposition to produce hydrogen, the catalyst active component is Ni, and the carrier is silicon oxide, aluminum oxide or titanium oxide material; wherein, the mass of the active component Ni The percentage is 1-50%.

The supported nickel catalyst, wherein the particle size of the active component nickel is 2-10 nanometers.

The supported nickel catalyst, wherein the carrier is SBA-15, MCM-41, SiO ₂ , Al ₂ O ₃ or TiO ₂ .

The method for preparing above-mentioned supported nickel catalyst provided by the invention, its steps are:

A) The soluble nickel salt, pH regulator, precipitant, carrier and deionized water are formulated into a suspension according to the mass ratio of 5-25:0.5-3:5-25:1:50-500 in sequence;

B) The suspension is heated to 70-110°C and deposited for 60-300 minutes, preferably the deposition temperature is 90°C.

C) the suspension is lowered to 20-30°C and filtered, washed with water, and filtered;

D) After drying at 80-120°C for 18-24 hours, calcining at 400-900°C for 2-6 hours, preferably at 500-800°C;

E) In a hydrogen atmosphere, or a mixed gas atmosphere of hydrogen and helium, activate at 400-900°C for 3-5 hours, and reduce to make a supported nano-nickel catalyst;

The soluble nickel salt is nickel nitrate, nickel acetate or/and nickel chloride, preferably nickel nitrate;

The pH regulator is nitric acid, acetic acid or/and hydrochloric acid, preferably nitric acid;

The precipitation agent is urea;

The carrier is silicon oxide, aluminum oxide or titanium oxide material;

The mass percent content of the nickel accounts for 1-50% of the total mass of the catalyst.

The preparation method, wherein, in step D, the sample is dried in an air atmosphere, and the drying temperature is 110°C.

The preparation method, wherein, in step D, the sample is roasted in an air atmosphere.

The supported nickel catalyst provided by the invention can be used in the hydrogen production reaction of ammonia decomposition, and the specific reaction conditions are: temperature 500-800°C, space velocity 20000-60000ml/h.g-cat.

The supported nickel catalyst provided by the invention not only has the advantages of high specific surface area, high dispersion, high stability, etc., but also the particle size of the active component nickel is controlled at 2-10 nanometers, and the distribution is uniform. At the same time, the catalyst prepared by the method has high catalytic decomposition activity and high stability for ammonia decomposition to produce COx-free hydrogen. In addition, the preparation method has simple procedures and strong repeatability.

Detailed ways

The technology of the present invention is further described below by some embodiments

Example 1

Mix nickel nitrate (28.2g), nitric acid (1.98g), urea (19.3g), SBA-15 (1.95g) and deionized water to prepare a 300ml suspension, and then heat to 90°C. After stirring for 120 minutes the temperature was lowered to 25°C and filtered. The samples were washed several times with 100 ml of deionized water. The sample obtained was treated at 110° C. for 24 hours. Dried samples were fired at 550°C for 3 hours. Take 0.1g of catalyst and place it in a quartz reactor, raise it from room temperature to 500°C at 5°C/min in a 25% H ₂ /He mixed gas atmosphere, and activate at this temperature for 5 hours, then purged with helium Then feed high-purity ammonia to react. Under the reaction conditions of 600°C and space velocity of 30000ml/hg-cat, the results of ammonia decomposition reaction are as follows: the conversion rate of ammonia is 92.1%, the formation rate of hydrogen is 30.8mmol/min.g _cat ; the nickel particle of the active center is about 7.8 nanometers.

Example 2

The stirring time of catalyst preparation is 180 minutes, and others are identical with embodiment 1. Under the reaction conditions of 600°C and space velocity of 30000ml/hg-cat, the ammonia decomposition reaction results are as follows: the ammonia conversion rate is 96.2%, the hydrogen formation rate is 32.2mmol/min.g _cat ; the nickel particle of the active center is about 7.4 nanometers.

Example 3

The reduction temperature is 600°C, and the others are the same as in Example 2. Under the reaction conditions of 600°C and space velocity of 30000ml/hg-cat, the ammonia decomposition reaction results are as follows: the ammonia conversion rate is 100%, the hydrogen formation rate is 33.5mmol/min.g _cat ; the nickel particle of the active center is about 5.7 nanometers.

Example 4

Urea is 25.2g, solution volume is 250ml, and others are identical with embodiment 1. Under the reaction conditions of 600°C and space velocity of 30000ml/hg-cat, the ammonia decomposition reaction results are as follows: the ammonia conversion rate is 97.2%, the hydrogen formation rate is 32.5mmol/min.g _cat ; the nickel particle of the active center is about 6 nanometers.

Example 5-8

The carrier is SiO ₂ , MCM-41, Al ₂ O ₃ and TiO ₂ in sequence, and the others are the same as in Example 2. The ammonia decomposition reaction results and the nickel particle size results of the active center under the reaction conditions of 600°C and a space velocity of 30000ml/hg-cat are shown in Table 1:

Table 1

Example Ammonia conversion (%) Hydrogen formation rate (mmol/min g_cat) Nickel particle size (nm) 5 99 33.2 7.2 6 99.5 33.3 6.8 7 97 32.5 7.3 8 93 31.1 8

Example 9

The pH adjuster hydrochloric acid (2.5g), the carrier is SiO ₂ , and the others are the same as in Example 2. Under the reaction conditions of 600°C and space velocity of 30000ml/hg-cat, the ammonia decomposition reaction results are as follows: the ammonia conversion rate is 96%, the hydrogen formation rate is 32.1mmol/min.g _cat ; the nickel particle of the active center is about 8 nanometers.

Examples 10-11

Soluble nickel nitrate adopts nickel acetate (24.2g), nickel chloride (23g) successively, and others are identical with embodiment 2. The ammonia decomposition reaction results and the nickel particle size results of the active center under the reaction conditions of 600°C and a space velocity of 30000ml/h.g-cat are shown in Table 2:

Table 2

Example Ammonia conversion (%) Hydrogen formation rate (mmol/min.g_cat) Nickel particle size (nm) 10 96.8 32.4 8.2 11 96.5 32.3 8.5

Claims (6)

1. one kind is used for the nickel catalyst carried preparation method of preparing hydrogen by ammonia decomposition, the steps include:

A) with soluble nickel salt, pH value conditioning agent, precipitating reagent, carrier and deionized water in regular turn according to mass ratio 5-25: 0.5-3: 5-25: 1: 50-500 is made into suspension;

B) suspension was heated to 70-110 ℃ of deposition 60-300 minute;

C) also filter water washing, filtration after above-mentioned suspension is reduced to 20-30 ℃;

D) after 80-120 ℃ of dry 18-24 hour, in 400-900 ℃ of roasting 2-6 hour;

E) at hydrogen atmosphere, perhaps in the gaseous mixture atmosphere of hydrogen and helium, in 400-900 ℃ of activation 3-5 hour, supported nanometer nickel catalyst was made in reduction;

Described soluble nickel salt is that nickel nitrate, nickel acetate are or/and nickel chloride;

Described pH value conditioning agent is that nitric acid, acetic acid are or/and hydrochloric acid;

Described precipitating reagent is a urea;

Described carrier is silica, aluminium oxide or titania meterial;

The quality percentage composition of nickel accounts for the 1-50% of catalyst gross mass.

2. preparation method as claimed in claim 1, wherein, soluble nickel salt is a nickel nitrate in the steps A.

3. preparation method as claimed in claim 1, wherein, pH value conditioning agent is a nitric acid among the step B.

4. preparation method as claimed in claim 1, wherein, depositing temperature is 90 ℃ among the step B.

5. preparation method as claimed in claim 1, wherein, sample drying is in the air atmosphere among the step D, the sample drying temperature is 110 ℃.

6. preparation method as claimed in claim 1, wherein, roasting is an air atmosphere among the step D, the sample sintering temperature is 500-800 ℃.