CN1131638A - Catalyst for preparing synthetic gas by natural gas partial oxidation and its preparation method - Google Patents

Abstract

A catalyst for preparing synthetic gas by partial oxidation of natural as is a carried Ni catalyst with noble metal as additive, and contains Ni (12-24%) and noble metal (0.1-5% in carrier weight as reference). The noble metal is uniformly distributed on surface of carrier and reacts with Ni mutually. It features high catalytic activity and carbon deposition resistance, and high selectivities (93.4% for H2 and 90.2% for CO).

Description

Catalyst for preparing synthesis gas by partial oxidation of natural gas and preparation method thereof

The invention provides a noble metal-added negative-cut nickel catalyst for preparing synthesis gas by partial oxidation of natural gas and a preparation method thereof.

Chemical utilization of natural gas is primarily achieved by conversion to synthesis gas. The process for converting natural gas into synthesis gas has three processes as follows:

1. reforming natural gas steam, wherein the main reaction is (1);

(1)

2. the natural gas partial oxidation combines with the steam conversion method, the main reaction is (1) and (2); $C$ $H_4+\frac{1}{2}{O}_2\→\mathrm{CO}+2H_2-----\left(2\right)$

3. the main reaction of the partial oxidation method of natural gas is (2).

The first process is mainly used for generating synthesis gas for synthesizing ammonia; the second process is to produce synthesis gas for methanol; both of these processes have been used industrially. The third process is mainly used for producing the synthesis gas for methanol, the process has been researched in the fortieth of the century, and due to the advantages of high space velocity, low energy consumption and the like, people pay more attention to the process in the nineties. The catalyst used in the process is mainly a supported noble metal catalyst and a supported nickel catalyst. In 1993, the results are better when the supported Pt (content is 12-20 wt%) and the pure Pt-Rh alloy net adopted by the Schmidt professor of the university of Minnesota in the United states are used as catalysts, but the noble metal catalyst is difficult to industrially produce due to large consumption and high cost of the noble metal; the negative type nickel catalyst has low activity, easy carbon formation, easy fire flowing of effective components and unstable activity. 3 wt% Ni/Al by Schmidt professor 1994₂O₃The investigation was conducted and it was found that the Ni content in the front portion of the catalyst after 22 hours of reaction at 850 ℃ was only 0.1 wt%, and CH₄Conversion and H₂The selectivity of (2%) is reduced.

The invention aims to develop a catalyst with low cost, high catalytic activity and H pair₂And the supported nickel catalyst added with noble metal has good CO selectivity and strong anti-coking performance.

The aim of the invention is achieved by adding noble metal to the supported nickel catalyst, and by a special preparation method, the noble metal is highly dispersed and interacts with nickel.

The amount of the noble metal added to the catalyst is preferably 0.1 to 5% by weight, more preferably 0.1 to 1.0% by weight based on the carrier.

The preparation method of the catalyst comprises the following steps:

(1) fully stirring the carrier, the soluble nickel salt and water, standing, drying at 50-200 ℃, and roasting at 500-700 ℃ to obtain the supported nickel catalyst.

The carrier of the catalyst may be Al₂O₃，SiO₂-Al₂O₃，SiO₂-ZrO₂，MgAl₂O₄Suitable soluble nickel salts such as Ni (CH)₃COO)₂，Ni(NO₃)₂，NiCl₂，NiSO₄Etc., the amount of the nickel salt may be determined according to the desired nickel content of the catalyst.

(2) And fully mixing the load nickel catalyst with the noble metal compound solution,standing, slowly drying, and reducing in a pure hydrogen atmosphere at 300-400 ℃ to obtain the noble metal-added load nickel catalyst.

A suitable noble metal compound for this step is H₂PtCl₆，H₂PdCl₄，H₃RhCl₆，PdCl₂，RuCl₃，Rhcl₃And the like.

The catalyst of the invention has the following characteristics:

1. x-ray diffraction and X-ray photoelectron spectroscopy analysis show that the noble metal is highly dispersed, and nickel and the noble metal are interacted.

2. Under the same experimental conditions, compared with a supported nickel catalyst without noble metal, the supported nickel catalyst has the advantages of high catalytic activity, strong anti-coking performance and H resistance₂The selectivity of CO can reach more than 92 percent. These properties are comparable to large cut-offs (12% by weight) of supported noble metal catalysts.

3. The working conditions of the catalyst are suitable for the conditions of negative nickel catalysts used in the industrial steam conversion and two-stage oxygen blowing method.

4. Because only a small amount of noble metal is added, the cost of the supported noble metal catalyst with larger loading amount is greatly reduced.

The specifications of the catalyst of the invention are as follows: a particle size of 20 to 100 mesh, a bulk density of 1.1 to 1.5g/ml, and a BET specific surface area of 5 to 20M²(iv) per gram, the average pore volume is 0.1 to 0.3 ml/gram.

Example 1:

1 wt% Pt in Ni/α -Al₂O₃Preparation and testing of (1):

taking 5g of catalyst as an example, the feeding amount is as follows:

taking 4.5g of α -Al₂O₃Adding 13.4g of 12.5% nickel nitrate aqueous solution into the carrier, soaking for 2 hours, drying, and roasting at 600 ℃ to obtain Ni/α -Al₂O₃A catalyst; then 1.2ml of H with a concentration of 0.0379g/ml were added₂PtCl₆Dipping the solution and drying to obtain the finished product catalyst.

Testing the catalytic performance in the partial oxidation reaction of methane under the experimental conditions:

a stainless steel tube fixed bed reactor, a thermocouple is inserted, the granularity of the catalyst is 40-60 meshes, the dosage is 0.5mml, the bed layer height is 45mm, and H is₂Reducing for two hours, axially passing raw gas through the catalyst bed from top to bottom, leading out product from the lower part of the bed, and obtaining CH₄Conversion and CO selectivity of (2) was calculated by gas chromatography analysis, H₂Selectively using material balance. The reaction conditions are that the temperature range is 600 ℃ and 950 ℃, and CH₄/O₂The ratio is 1.8 and the space velocity is 1.5X 10⁵Time of flight^-1CH at 800 ℃₄Conversion of 90%, CO selectivity of 88.5%, H₂The selectivity of (a) was 91.3%.

Example 2:

0.6 wt% Pt Ni/α -Al₂O₃Preparation and testing of (1):

taking 5g of catalyst as an example, the feeding amount is as follows:

to Ni/α -Al₂O₃The catalyst (amount and preparation method are the same as example 1) is added with 0.72ml of H with the concentration of 0.0379g/ml₂PtCl₆Dipping the solution and drying to obtain the finished product catalyst.

The catalyst activity was measured as in example 1,CH at 800 ℃₄Conversion 86.5%, CO selectivity 88.3%, H₂The selectivity was 89.1%.

Example 3:

ni/α -Al of 1 wt% Rh₂O₃Preparing and testing the activity;

taking 5g of catalyst as an example, the feeding amount is as follows:

to Ni/α -Al₂O₃Catalyst (amount of used material and preparation method are same as example 1) is added3.5ml RhCl with a concentration of 0.0105g/ml₃Dipping the solution and drying to obtain the finished product catalyst.

The catalyst activity was determined as in example 1, CH₄Conversion 92.5%, CO selectivity 90.2%, H₂The selectivity was 93.4%.

Example 4:

1 wt% Ru Nl/α -Al₂O₃Preparation and activity test of (1):

taking 5g of catalyst as an example, the feeding amount is as follows:

to Ni/α -Al₂O₃4.0ml RuCl with concentration of 0.0112g/ml is added into the catalyst (the material amount and the preparation method are the same as the example 1)₃Dipping the solution and drying to obtain the finished product catalyst.

The catalyst activity was tested as in example 1, with a methane conversion of 91.1%, a CO selectivity of 89.7%, and H₂The selectivity was 91.5%.

Example 5:

ni/α -Al of 1 wt% Pd₂O₅Preparation and activity test of (1):

still taking the preparation of 5g of catalyst as an example, the charge amounts are:

to the obtained Ni/α -Al₂O₃2.4ml of PdCl with a concentration of 0.0186g/ml were added to the catalyst (the amount and preparation method were the same as in example 1)₂Dipping the solution and drying to obtain the finished product catalyst.

The catalytic activity was measured as in example 1, with a methane conversion of 81%, a CO selectivity of 84.5%, and a H selectivity₂The selectivity was 86.3%.

Comparative example 1:

Ni/α-Al₂O₃preparation and testing of (1):

taking 5g of catalyst as an example, the feeding amount is as follows:

taking 4.5g of α -Al₂O₃Cutting, adding 13.4g of 12.5% nickel nitrate solution, soaking for 2 hours, drying, and roasting at 600 ℃ to obtain the finished catalyst.

The activity of the catalyst was determined as in example 1, CH at 800 ℃₄Conversion 68.3%, CO selectivity 74.1%, H₂The selectivity was 79.6%.

Comparative example 2:

2wt％Pd/α-Al₂O₃preparation and testing:

taking 5g of catalyst as an example, the feeding amount is as follows:

5g of α -Al was taken₂O₃Carrier, 5.4ml of Pdcl with the concentration of 0.0186g/ml is added₂And (5) soaking the solution, and drying to obtain the finished catalyst.

The catalyst activity was tested as in example 1, with a methane conversion of 72.8%, a CO selectivity of 80.4%, and a H selectivity₂The selectivity was 82.6%.

Claims (6)

1. A nickel-loaded catalyst for preparing synthetic gas by partial oxidation of natural gas is characterized in that noble metal is added as a cocatalyst, the content of the noble metal is 0.1-5% (based on a carrier, in percentage by weight), and the specific surface area is 5-20M²/g。

The preparation method of the catalyst comprises the following steps:

(1) and uniformly stirring the carrier and the measured soluble nickel salt solution at the temperature of 10-80 ℃.

(2) Standing for more than 1 hour, and drying at 50-200 ℃.

(3) And roasting at 500-700 ℃ to obtain the supported nickel catalyst.

(4) And uniformly mixing the supported nickel catalyst with a metered noble metal compound solution, standing and drying to obtain the supported nickel catalyst added with noble metal.

2. The catalyst according to claim 1, wherein the noble metal is Pt.

3. The catalyst according to claim 1, wherein the noble metal is Rh.

4. The catalyst according to claim 1, wherein the noble metal is Ru.

5. The catalyst according to claim 1, wherein the noble metal is Pd.

6. A catalyst according to claim 2, 3, 4 or 5, characterized in that the noble metal is added in an amount of 0.1 to 1.0% by weight based on the support.