CN1184005C - Prepn of nickel-base catalyst - Google Patents

Abstract

The invention discloses a preparation method of a nickel-based catalyst, which is used for partial oxidation of methane to prepare synthesis gas. The preparation method includes mixing nickel nitrate aqueous solution, a solution composed of n-octane, polyoxyethylene 9-10 octyl phenyl ether and n-hexanol, aluminum isopropoxide or tetraethyl orthosilicate, at 20-60 ° C Stirring; then filtered, washed, dried and roasted to obtain the catalyst. Compared with the traditional impregnation method, the prepared catalyst has smaller particle size and larger specific surface area. Under the operating conditions of normal pressure, reaction temperature of 600-800°C, and space velocity of 6000-15000mlg ^-1 h ^-1 , in a fixed-bed reactor, it has high reactivity, and the catalyst also has anti-coking and high-temperature stability. sex.

Description

Preparation method of nickel-based catalyst

Field

The invention relates to a preparation method of a nickel-based catalyst, which is used for partial oxidation of methane to prepare synthesis gas.

Background technique

In the current field of methane reforming and partial oxidation to synthesis gas, it has been found that only supported Ni catalysts have application prospects, because supported Ni catalysts have similar performance to noble metal catalysts such as Rh and Pt in terms of reactivity and high temperature stability. , and the price is cheap [Petroleum and Gas Chemical Industry, Vol. 26, No. 3, Page 145]. However, the catalytic activity of Ni, the active component of this catalyst, will decrease due to easy loss and sintering during the reaction process [Applied Chemistry, Volume 14, Issue 3, Page 19]. Therefore, it is of great significance to further study the preparation method of nickel-based catalysts and improve its performance for future industrial production.

Contents of the invention

The object of the present invention is to provide a kind of preparation method of nickel-based catalyst.

The carrier of the nickel-based catalyst is Al ₂ O ₃ or SiO ₂ , and the active component is nickel. The mass ratio _of nickel to _Al2O3 or _SiO2 is 1-25%. The particle diameter of the catalyst is 4-10nm, and the specific surface area is 300-900m ² g ^-1 .

A preparation method of a nickel-based catalyst is characterized in that the method comprises nickel nitrate aqueous solution, a solution composed of n-octane, polyoxyethylene 9-10 octylphenyl ether and n-hexanol, aluminum isopropoxide or orthosilicon Acid tetraethyl ester phase mixed, stirred at 20-60 ° C; then filtered, washed, dried and roasted to obtain the catalyst.

The mass ratio of n-octane and polyoxyethylene 9-10 octylphenyl ether is 2-10.

The mass ratio of n-hexanol and polyoxyethylene 9-10 octylphenyl ether is 1-5.

Nickel nitrate aqueous solution, its molar concentration is 0.2-1.0mol/l.

The volume ratio of the nickel nitrate aqueous solution to the mixed solution composed of n-octane, polyoxyethylene 9-10 octyl phenyl ether and n-hexanol is 2-8.

The amount of aluminum isopropoxide or tetraethyl orthosilicate added is 5-12 times the mass of solid nickel nitrate.

The mixed solution composed of n-octane, polyoxyethylene 9-10 octylphenyl ether and n-hexanol is used as the "oil phase" in this reaction, and can be uniformly mixed with the "water phase" of nickel nitrate aqueous solution to form a clear and transparent The solution, so that nickel atoms are more dispersed in the solution, this solution can be called microemulsion solution. The "oil phase" solution may also be referred to as a microemulsion medium.

The catalyst prepared by the present invention is used for the partial oxidation of methane to produce synthesis gas. Under the operating conditions of normal pressure, reaction temperature of 600-800°C and space velocity of 6000-15000mlg ^-1 h ^-1 , in a fixed-bed reactor, With high reactivity, the conversion rate of CH ₄ can reach 99.3%, the selectivity of CO can reach 97.1%, and the selectivity of H ₂ can reach 100% (the above refers to the best result). The catalyst also has carbon deposition resistance and high temperature stability.

The outstanding features of the present invention are: (1) Compared with the traditional impregnation method, the catalyst prepared by this method has smaller particle size and larger specific surface area. The particle diameter of the catalyst obtained by this method is 4-10nm, and the specific surface area is 300-900m ² g ^-1 . (2) The time required for this preparation method is shorter than that of the dipping method. (3) The process of this method is simple and the raw materials are cheap and easy to obtain, and it is possible to produce on a large scale.

Detailed ways

Example 1:

Dissolve 0.6245 grams of Ni(NO ₃ ) ₂ ·6H ₂ O in 7ml of distilled water to form a nickel nitrate aqueous solution, and then add it to 20ml of polyoxyethylene 9-10 octylphenyl ether, 18ml of n-octane, and 5ml of n-hexanol. in the mixed solution. After mixing evenly, add 7 grams of aluminum isopropoxide, stir at 50°C for 3 hours, filter with suction, wash, dry at 80°C, and roast at 600°C for 4 hours in an air atmosphere to obtain the finished catalyst. The particle diameter of the obtained catalyst was measured to be 8.2 nm, and the specific surface area was 357 m ² g ^-1 .

Example 2:

Dissolve 2.014 grams of Ni(NO ₃ ) ₂ ·6H ₂ O in 10 ml of distilled water to form an aqueous solution of nickel nitrate, then add 34 ml of polyoxyethylene 9-10 octylphenyl ether, 20 ml of n-octane, and 15 ml of n-hexanol. mixture. After mixing evenly, add 20ml tetraethyl orthosilicate, stir at 50°C for 2 hours, then filter with suction, wash, dry at 80°C overnight, and then bake at 600°C for 2 hours in an air atmosphere to obtain the finished catalyst. The particle diameter of the obtained catalyst was measured to be 5.6 nm, and the specific surface area was 804 m ² g ^-1 .

Example 3:

0.8034 g of Ni(NO ₃ ) ₂ ·6H ₂ O was dissolved in 8 ml of distilled water, and the preparation process of the catalyst was the same as in Example 1.

Take 0.4 g of the catalyst of 30-50 mesh and place it in a quartz tube reactor with a diameter of 6 mm, feed 2:1 methane and oxygen at a space velocity of 8400 mlg ^-1 h ^-1 , and continue the reaction under normal pressure with programmed temperature increase. The reaction results are listed in Table 1.

Table 1. Methane conversion and product selectivity of partial oxidation of methane at different temperatures temperature(℃) X _CH4 (%) Y _CO (%) Y _CO2 (%) Y _H2 (%) 600 62.3 63.2 36.8 89.8 650 74.0 76.7 23.3 94.5 700 87.9 89.0 11.0 99.9 750 92.3 91.9 8.1 100 800 95.8 95.0 5.0 100

X _CH4 : _CH4 conversion Y _CO : CO selectivity Y _CO2 : _CO2 selectivity Y _H2 : _H2 selectivity

Example 4:

1.024 g of Ni(NO ₃ ) ₂ ·6H ₂ O was dissolved in 8 ml of distilled water, and the preparation process of the catalyst was the same as in Example 1.

Get this catalyzer of 0.4 gram 30-50 order, adopt the reaction apparatus and reaction condition of embodiment 3. The reaction results are listed in Table 2.

Table 2. Methane conversion and product selectivity of partial oxidation of methane at different temperatures temperature(℃) X _CH4 (%) Y _CO (%) Y _CO2 (%) Y _H2 (%) 600 66.0 67.8 32.8 92.3 650 76.4 82.5 17.5 96.3 700 91.2 92.3 7.7 98.9 750 95.7 95.0 5.0 100 800 99.3 97.1 2.9 100

X _CH4 : _CH4 conversion Y _CO : CO selectivity Y _CO2 : _CO2 selectivity Y _H2 : _H2 selectivity

Moreover, the Ni/Al ₂ O ₃ prepared by this method and the Ni/Al ₂ O ₃ prepared by the traditional impregnation method with the same load were reacted for 20 hours at 750 ° C, and the amount of carbon deposited was found to be 0.5 %, while the latter is 0.9%.

Example 5: 1.2036 g of Ni(NO ₃ ) ₂ ·6H ₂ O was dissolved in 8 ml of distilled water, and the preparation process of the catalyst was the same as in Example 1.

Get this catalyzer of 0.4 gram 30-50 order, adopt the reaction apparatus and reaction condition of embodiment 3. The reaction results are listed in Table 3.

Table 3. Methane conversion and product selectivity of partial oxidation of methane at different temperatures temperature(℃) X _CH4 (%) Y _CO (%) Y _CO2 (%) Y _H2 (%) 600 66.1 66.8 33.2 91.5 650 76.2 83.7 16.3 97.1 700 92.3 90.3 9.7 99.7 750 94.4 95.1 4.9 99.4 800 98.3 96.7 3.3 98.5

X _CH4 : _CH4 conversion Y _CO : CO selectivity Y _CO2 : _CO2 selectivity Y _H2 : _H2 selectivity

Example 6: 1.4056 g of Ni(NO ₃ ) ₂ ·6H ₂ O was dissolved in 8 ml of distilled water, and the preparation process of the catalyst was the same as in Example 1.

Get this catalyzer of 0.4 gram 30-50 order, adopt the reaction apparatus and reaction condition of embodiment 3. The reaction results are listed in Table 4.

Table 4. Methane conversion and product selectivity of partial oxidation of methane at different temperatures temperature(℃) X _CH4 (%) Y _CO (%) Y _CO2 (%) Y _H2 (%) 600 63.3 63.9 36.1 89.9 650 74.9 77.4 22.6 95.7 700 85.7 87.2 12.8 99.3 750 92.2 92.0 8.0 100 800 96.6 94.9 5.1 100

X _CH4 : _CH4 conversion Y _CO : CO selectivity Y _CO2 : _CO2 selectivity Y _H2 : _H2 selectivity

Claims (6)

1, a kind of preparation method of nickel-base catalyst, it is characterized in that this method comprises nickel nitrate aqueous solution, by the solution that normal octane, polyoxyethylene 9-10 octyl phenyl ether and n-hexyl alcohol are formed, aluminium isopropoxide or positive tetraethyl orthosilicate mix mutually, stir down at 20-60 ℃; Through suction filtration, wash then, dry and roasting makes catalyst.

2,, it is characterized in that the mass ratio of normal octane and polyoxyethylene 9-10 octyl phenyl ether is 2-10 as the said method of claim 1.

3,, it is characterized in that the mass ratio of n-hexyl alcohol and polyoxyethylene 9-10 octyl phenyl ether is 1-5 as the said method of claim 1.

4, as the said method of claim 1, the molar concentration that it is characterized in that nickel nitrate aqueous solution is 0.2-1.0mol/l.

5,, it is characterized in that nickel nitrate aqueous solution and the volume ratio of the mixed solution be made up of normal octane, polyoxyethylene 9-10 octyl phenyl ether and n-hexyl alcohol is 2-8 as claim 1 or 4 said methods.

6, as the said method of claim 1, the addition that it is characterized in that aluminium isopropoxide or positive tetraethyl orthosilicate is 5-12 a times of solid nitric acid nickel quality.