A rare earth oxide-silica supported noble metal catalyst, its preparation method and application

Abstract

The present invention provides a rare earth oxide-silica supported noble metal catalyst, a preparation method thereof and an application thereof. The catalyst comprises: hydrophilic fumed silica with a specific surface area of 300-500 m 2 / g; rare earth oxides distributed on the surface of the hydrophilic fumed silica; noble metal nanoparticles with a size of 1-2 nm supported on the rare earth oxides; the noble metal nanoparticles are selected from Ru, Pt, Ir or Rh. The silica is dispersed in an aqueous solution, and rare earth cations and ammonia water are added; the mixed solution is subjected to suction filtration to obtain a solid; the above solid is dried and then impregnated with a noble metal precursor salt; and then dried and reduced. This method can obtain ruthenium nanoparticles with uniform size and uniform distribution. It is simple and easy to scale up. At the same time, when it is applied to the dry reforming of methane reaction, it has strong anti-sintering and anti-carbon deposition capabilities and can maintain high stability at high temperatures and high space velocities.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalysts, and particularly relates to a rare earth oxide-silica supported noble metal catalyst, a preparation method thereof, and an application thereof. Background Art

[0002] In recent years, due to the increasing emissions of carbon dioxide, the greenhouse effect has become more and more obvious. Therefore, it is urgent to utilize the carbon dioxide generated in human production activities. Converting methane and carbon dioxide, two greenhouse gases, into syngas through the dry reforming of methane is a feasible and economically beneficial process. Although Ru and Rh, as the active sites for the dry reforming of methane, have high catalytic activity, the catalysts suffer from serious sintering and carbon deposition.

[0003] Therefore, developing a methane dry reforming catalyst with anti-sintering and anti-carbon deposition properties has become a research hotspot. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a rare earth oxide-silica supported noble metal catalyst, a preparation method thereof, and an application thereof, and the catalyst has both high activity and high stability.

[0005] The present invention provides a rare earth oxide-silica supported noble metal catalyst, including silica with a specific surface area of 300 - 500 m 2 / g;

[0006] rare earth oxides distributed on the surface of the hydrophilic fumed silica;

[0007] noble metal nanoparticles with a size of 1 - 2 nm supported on the rare earth oxides; the noble metal nanoparticles are selected from Ru, Pt, Ir or Rh.

[0008] In the present invention, the mass ratio of the hydrophilic fumed silica, noble metal nanoparticles and rare earth oxides is 100:2:3 - 4.

[0009] In the present invention, the rare earth oxide-silica supported noble metal catalyst is specifically a Ru / LaO x -SiO2 catalyst, Ru / PrO x -SiO2 catalyst, Ru / NdO x -SiO2 catalyst, Ru / TbO x -SiO2 catalyst, Ru / SmO x -SiO2 catalyst, Ru / GdO x -SiO2 catalyst, Ru / CeO x -SiO2 catalyst, Rh / LaO x -SiO2 catalyst, Pt / LaOx -SiO2 catalyst, or Ir / LaO x -SiO2 catalyst. The theoretical loading of rare earth elements in each catalyst is 4 wt%, and the actual loading may be 3 - 4, that is, the x range is 3 - 4.

[0010] Ru / LaO x -SiO2 catalyst that exhibits long-term stability in the dry reforming of methane.

[0011] The present invention provides a method for preparing a rare earth oxide-silica supported noble metal catalyst as described in the above technical solution, including the following steps:

[0012] 1) Mix silica and water to obtain a first mixed solution;

[0013] 2) Mix rare earth nitrate and the first mixed solution to obtain a second mixed solution;

[0014] 3) Mix ammonia water and the second mixed solution to obtain a third mixed solution;

[0015] 4) Filter the third mixed solution by suction, and dry the obtained solid to obtain a mixed solid;

[0016] 5) Mix a precursor salt of any one of Ru, Pt, Ir, and Rh with water to obtain a fourth mixed solution;

[0017] 6) Mix the fourth mixed solution and the mixed solid, dry the obtained gel at room temperature and then dry it to obtain a rare earth oxide-silica supported noble metal catalyst.

[0018] In the present invention, the molar ratio of silica in step 1), water in step 1), and rare earth nitrate in step 2) is 1:(100 - 2000):(0.01 - 0.1).

[0019] In the present invention, the mixing of the rare earth nitrate and the first mixed solution is carried out under stirring; the stirring time is 10 - 30 min.

[0020] In the present invention, the mixing of the ammonia water and the second mixed solution is carried out under stirring; the stirring time is 10 - 30 min.

[0021] In the present invention, the molar ratio of the mixed solid, water in step 5), and the noble metal is: 1:(1 - 20):(0.01 - 0.1).

[0022] In the present invention, the drying temperature in step 6) is 60 - 80 °C.

[0023] The present invention provides an application of the rare earth oxide-silica supported noble metal catalyst described in the above technical solution in the production of syngas by dry reforming of methane.

[0024] In the present invention, the dry reforming reaction is the methane / carbon dioxide dry reforming reaction.

[0025] The present invention provides a rare earth oxide-silica supported noble metal catalyst, including silica with a specific surface area of 300-500 m 2 / g; rare earth oxides distributed on the surface of the hydrophilic fumed silica; noble metal nanoparticles with a size of 1-2 nm supported on the rare earth oxides; the noble metal nanoparticles are selected from Ru, Pt, Ir or Rh. The rare earth oxide-silica supported noble metal catalyst provided by the present invention has good anti-sintering and anti-carbon deposition capabilities; it shows high methane and carbon dioxide conversion rates and long-term stability in the methane dry reforming reaction at high temperature and high space velocity. Description of the Drawings

[0026] Figure 1 It is a transmission electron microscope photograph of Ru / LaO x -SiO2 prepared in Example 1 of the present invention after being reduced at 800 °C in an H2 atmosphere (H2 / Ar = 1 / 9) for 4 h;

[0027] Figure 2 It is a transmission electron microscope photograph of Ru / SiO2 prepared in Comparative Example 1 of the present invention after being reduced at 800 °C in an H2 atmosphere (H2 / Ar = 1 / 9) for 4 h;

[0028] Figure 3 It is for Rh / SiO2, Rh / LaO x -SiO2; Ir / SiO2, Ir / LaO x -SiO2; Pt / SiO2, Pt / LaO x -SiO2 after being reduced at 800 °C in an H2 atmosphere (H2 / Ar = 1 / 9) for 4 h;

[0029] Figure 4 It is a normalized comparison of the performance of the catalysts prepared in Examples 1-7 and Comparative Example 1 of the present invention in the methane dry reforming reaction at 800 °C and 250 L / g cat / h;

[0030] Figure 5 It is for Ru / LaO prepared in Example 1 and Comparative Example of the present invention x -SiO2 and Ru / SiO2 at 800 °C and 250 L / g catLong-term stability of the dry reforming of methane under / h conditions. Specific implementation mode

[0031] To further illustrate the present invention, a rare earth oxide-silica supported noble metal catalyst provided by the present invention, its preparation method and application will be described in detail below in conjunction with embodiments, but they cannot be understood as limiting the protection scope of the present invention.

[0032] Example 1

[0033] Weigh 500 mg of fumed silica and disperse it in 100 mL of deionized water, stir for 10 min, pour in 62.3 mg of La(NO3)3·6H2O and stir for 10 min until completely dissolved. Add a certain amount of 2M NH3·H2O to adjust the pH of the solution to 9-11, stir for 10 min and then filter by suction, and dry overnight in an oven at 60 °C. Grind the obtained solid, take out 300 mg, weigh 18.2 mg of Ru(NH3)6Cl3 and dissolve it in 600 μL of deionized water. Use the saturated impregnation method to add the above Ru(NH3)6Cl3 solution to 300 mg of the solid. The obtained catalyst is dried overnight in an oven at 60 °C and treated at 800 °C under a H2 atmosphere (H2 / Ar = 1 / 9) for 4 h to obtain Ru / LaO x -SiO2 catalyst. The transmission electron micrograph of the structure of this catalyst (Talos F200X, FEI Company) can be seen Figure 1 , and the average particle size is only 1.4 nm.

[0034] Example 2

[0035] Weigh 500 mg of fumed silica and disperse it in 100 mL of deionized water, stir for 10 min, pour in 61.7 mg of Pr(NO3)3·6H2O and stir for 10 min until completely dissolved. Add a certain amount of 2M NH3·H2O to adjust the pH of the solution to 9-11, stir for 10 min and then filter by suction, and dry overnight in an oven at 60 °C. Grind the obtained solid, take out 300 mg, weigh 18.2 mg of Ru(NH3)6Cl3 and dissolve it in 600 μL of deionized water. Use the saturated impregnation method to add the above Ru(NH3)6Cl3 solution to 300 mg of the solid. The obtained catalyst is dried overnight in an oven at 60 °C and treated at 800 °C under a H2 atmosphere (H2 / Ar = 1 / 9) for 4 h to obtain Ru / PrO x -SiO2 catalyst.

[0036] Example 3

[0037] Weigh 500 mg of fumed silica and disperse it in 100 mL of deionized water. Stir for 10 min, pour in 60.8 mg of Nd(NO3)3·6H2O and stir for 10 min until completely dissolved. Add a certain amount of 2M NH3·H2O to adjust the pH of the solution to 9 - 11. After stirring for 10 min, filter by suction, and dry overnight in an oven at 60 °C. Grind the obtained solid, take out 300 mg, weigh 18.2 mg of Ru(NH3)6Cl3 and dissolve it in 600 μL of deionized water. Use the saturated impregnation method to add the above Ru(NH3)6Cl3 solution to 300 mg of the solid. The obtained catalyst is dried overnight in an oven at 60 °C and then treated at 800 °C in a H2 atmosphere (H2 / Ar = 1 / 9) for 4 h to obtain the Ru / NdO x -SiO2 catalyst.

[0038] Example 4

[0039] Weigh 500 mg of fumed silica and disperse it in 100 mL of deionized water. Stir for 10 min, pour in 57.0 mg of Tb(NO3)3·6H2O and stir for 10 min until completely dissolved. Add a certain amount of 2M NH3·H2O to adjust the pH of the solution to 9 - 11. After stirring for 10 min, filter by suction, and dry overnight in an oven at 60 °C. Grind the obtained solid, take out 300 mg, weigh 18.2 mg of Ru(NH3)6Cl3 and dissolve it in 600 μL of deionized water. Use the saturated impregnation method to add the above Ru(NH3)6Cl3 solution to 300 mg of the solid. The obtained catalyst is dried overnight in an oven at 60 °C and then treated at 800 °C in a H2 atmosphere (H2 / Ar = 1 / 9) for 4 h to obtain the Ru / TbO x -SiO2 catalyst.

[0040] Example 5

[0041] Weigh 500 mg of fumed silica and disperse it in 100 mL of deionized water. Stir for 10 min, pour in 59.1 mg of Sm(NO3)3·6H2O and stir for 10 min until completely dissolved. Add a certain amount of 2M NH3·H2O to adjust the pH of the solution to 9 - 11. After stirring for 10 min, filter by suction, and dry overnight in an oven at 60 °C. Grind the obtained solid, take out 300 mg, weigh 18.2 mg of Ru(NH3)6Cl3 and dissolve it in 600 μL of deionized water. Use the saturated impregnation method to add the above Ru(NH3)6Cl3 solution to 300 mg of the solid. The obtained catalyst is dried overnight in an oven at 60 °C and then treated at 800 °C in a H2 atmosphere (H2 / Ar = 1 / 9) for 4 h to obtain the Ru / SmO x -SiO2 catalyst.

[0042] Example 6

[0043] Weigh 500 mg of fumed silica and disperse it in 100 mL of deionized water. Stir for 10 min, pour in 57.3 mg of Gd(NO3)3·6H2O and stir for 10 min until completely dissolved. Add a certain amount of 2M NH3·H2O to adjust the pH of the solution to 9 - 11. After stirring for 10 min, filter by suction and dry overnight in an oven at 60 °C. Grind the obtained solid, take out 300 mg, weigh 18.2 mg of Ru(NH3)6Cl3 and dissolve it in 600 μL of deionized water. Use the saturated impregnation method to add the above Ru(NH3)6Cl3 solution to 300 mg of the solid. The obtained catalyst is dried overnight in an oven at 60 °C and then treated at 800 °C under a H2 atmosphere (H2 / Ar = 1 / 9) for 4 h to obtain Ru / GdO x -SiO2 catalyst.

[0044] Example 7

[0045] Weigh 500 mg of fumed silica and disperse it in 100 mL of deionized water. Stir for 10 min, pour in 62.0 mg of Ce(NO3)3·6H2O and stir for 10 min until completely dissolved. Add a certain amount of 2M NH3·H2O to adjust the pH of the solution to 9 - 11. After stirring for 10 min, filter by suction and dry overnight in an oven at 60 °C. Grind the obtained solid, take out 300 mg, weigh 18.2 mg of Ru(NH3)6Cl3 and dissolve it in 600 μL of deionized water. Use the saturated impregnation method to add the above Ru(NH3)6Cl3 solution to 300 mg of the solid. The obtained catalyst is dried overnight in an oven at 60 °C and then treated at 800 °C under a H2 atmosphere (H2 / Ar = 1 / 9) for 4 h to obtain Ru / CeO x -SiO2 catalyst.

[0046] Example 8

[0047] Weigh 15.3 mg of RhCl3 and dissolve it in 600 μL of deionized water. Use the saturated impregnation method to add the above RhCl3 solution to 300 mg of the La / SiO2 solid described in Example 1. The obtained catalyst is dried overnight in an oven at 60 °C and then treated at 800 °C under a H2 atmosphere (H2 / Ar = 1 / 9) for 4 h to obtain Rh / LaO x -SiO2 catalyst. The transmission electron microscope image of the catalyst structure (FEI Company, Talos F200X) can be seen Figure 3 in Rh / LaO x -SiO2.

[0048] Example 9

[0049] Weigh 12.0 mg of Pt(NH3)4(NO3)2 and dissolve it in 600 μL of deionized water. Add the above Pt(NH3)4(NO3)2 solution to 300 mg of LaO x / SiO2 solid described in Example 1 using the saturated impregnation method. The obtained catalyst is dried overnight in an oven at 60 °C and then treated at 800 °C in an H2 atmosphere (H2 / Ar = 1 / 9) for 4 h to obtain Pt / LaO x -SiO2 catalyst. The transmission electron microscopy image of the catalyst structure (FEI Company, Talos F200X) can be seen Figure 3 in Pt / LaO x -SiO2.

[0050] Example 10

[0051] Weigh 9.3 mg of IrCl3 and dissolve it in 600 μL of deionized water. Add the above IrCl3 solution to 300 mg of La / SiO2 solid described in Example 1 using the saturated impregnation method. The obtained catalyst is dried overnight in an oven at 60 °C and then treated at 800 °C in an H2 atmosphere (H2 / Ar = 1 / 9) for 4 h to obtain Ir / LaO x -SiO2 catalyst. The transmission electron microscopy image of the catalyst structure (FEI Company, Talos F200X) can be seen Figure 3 in Ir / LaO x -SiO2.

[0052] Comparative Example 1

[0053] Weigh 18.2 mg of Ru(NH3)6Cl3 and dissolve it in 600 μL of deionized water. Add the above Ru(NH3)6Cl3 solution to 300 mg of fumed silica using the saturated impregnation method. The obtained catalyst is dried overnight in an oven at 60 °C and then treated at 800 °C in an H2 atmosphere (H2 / Ar = 1 / 9) for 4 h to obtain Ru / SiO2 catalyst. The transmission electron microscopy image of the catalyst structure (FEI Company, Talos F200X) can be seen Figure 2 , with an average particle size of 2.4 nm and uneven distribution.

[0054] Comparative Example 2

[0055] Weigh 12.0 mg of Pt(NH3)4(NO3)2 and dissolve it in 600 μL of deionized water. Add the above Pt(NH3)4(NO3)2 solution to 300 mg of fumed silica using the saturation impregnation method. The obtained catalyst is dried overnight in an oven at 60 °C and then treated at 800 °C in an H2 atmosphere (H2 / Ar = 1 / 9) for 4 h to obtain the Pt / SiO2 catalyst. The transmission electron micrograph of the structure of this catalyst (FEI Company, Talos F200X) can be seen Figure 3 in Pt / SiO2.

[0056] Comparative Example 3

[0057] Weigh 15.3 mg of RhCl3 and dissolve it in 600 μL of deionized water. Add the above RhCl3 solution to 300 mg of fumed silica using the saturation impregnation method. The obtained catalyst is dried overnight in an oven at 60 °C and then treated at 800 °C in an H2 atmosphere (H2 / Ar = 1 / 9) for 4 h to obtain the Rh / SiO2 catalyst. The transmission electron micrograph of the structure of this catalyst (FEI Company, Talos F200X) can be seen Figure 3 in Rh / SiO2.

[0058] Comparative Example 4

[0059] Weigh 9.3 mg of IrCl3 and dissolve it in 600 μL of deionized water. Add the above IrCl3 solution to 300 mg of fumed silica using the saturation impregnation method. The obtained catalyst is dried overnight in an oven at 60 °C and then treated at 800 °C in an H2 atmosphere (H2 / Ar = 1 / 9) for 4 h to obtain the Ir / SiO2 catalyst. The transmission electron micrograph of the structure of this catalyst (FEI Company, Talos F200X) can be seen Figure 3 in Ir / SiO2.

[0060] Example 11

[0061] Weigh 15 mg of the catalysts prepared in Examples 1 - 7 and Comparative Example 1 and place them in a fixed-bed reactor. Heat them to 800 °C at a rate of 10 °C / min in 40 mL / min of hydrogen and reduce them at atmospheric pressure for 1 hour. Maintain the temperature at 800 °C and introduce a certain flow rate of 62.5 ml / min of CH4 / CO2 / N2 (volume fraction 2 / 2 / 1) for continuous reaction at atmospheric pressure. Among them, N2 is used as an internal standard gas to calculate the conversion rates of CH4 and CO2. The products are analyzed online at atmospheric pressure after passing through a cold trap and analyzed by a gas chromatograph equipped with a TCD. The chromatographic conditions are a 5A molecular sieve packed column and a capillary packed column (50 m). The evaluation time is 15 h. After normalizing the initial activity, the performance results of Examples 1 - 7 and Comparative Example 1 are as Figure 4 .

[0062] Example 12

[0063] Weigh 15 mg of the catalyst prepared in Example 1 and place it in a fixed-bed reactor. Test its performance in dry reforming of methane under the same conditions as in Example 11. The evaluation time is 350 h, and the results are as Figure 5 shown.

[0064] Weigh 15 mg of the catalyst prepared in Comparative Example 1 and place it in a fixed-bed reactor. Test its performance in dry reforming of methane under the same conditions as in Example 11. The evaluation time is 170 h, and the results are as Figure 5 shown.

[0065] From Figure 1 and Figure 2 it can be seen that after reduction at 800 °C, Ru / SiO2 shows obvious sintering behavior, with an average particle size reaching 2.4 nm, and some particles exceeding 6 nm being clearly visible. In contrast, for Ru / LaO x -SiO2, after treatment at 800 °C, its average particle size is only 1.4 nm, and the maximum particle size is only 2 nm. Therefore, it can be concluded that the Ru / LaO x -SiO2 catalyst prepared in Example 1 shows better anti-sintering performance than the Ru / SiO2 catalyst in the comparative example.

[0066] As Figure 3 shown, for Rh / SiO2, Ir / SiO2, Pt / SiO2, after reduction at 800 °C for 4 h, different degrees of sintering occur. After adding La, it can be found that the average particle sizes of Rh / LaO x -SiO2, Rh / LaO x -SiO2, Rh / LaO x -SiO2 are significantly reduced, and the particle size distribution is uniform. Therefore, it is proved that the addition of LaO x has a certain effect on improving the anti-sintering performance of Rh / SiO2, Ir / SiO2, Pt / SiO2.

[0067] As Figure 4 shown, after introducing different rare earth oxides, the stability of dry reforming of methane over Ru / SiO2 is improved to varying degrees.

[0068] It can be seen from Figure 5 that under the space velocity conditions of 800 °C and 250 L / g cat / h, Ru / LaO xThe -SiO2 catalyst has good catalytic stability for dry reforming of methane, and no obvious deactivation is found. On the contrary, the methane conversion rate of Ru / SiO2 gradually decreases over time, from 89% to 38% within 170 h. It can be seen that the addition of LaO x significantly improves the performance of Ru / SiO2 in dry reforming of methane.

[0069] As can be seen from the above examples, the rare earth oxide-silica supported noble metal catalyst provided by the present invention has good anti-sintering ability; among them, the Ru / LaO x -SiO2 catalyst shows high methane and carbon dioxide conversion rates and long-term stability in the dry reforming of methane reaction at high temperature and high space velocity.

[0070] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A preparation method of a rare earth oxide-silica supported noble metal catalyst, comprising the following steps: 1) Mix silica and water to obtain a first mixed solution; the molar ratio of silica in step 1), water in step 1) and rare earth nitrate in step 2) is 1:(100~2000):(0.01~0.1); 2) Mix rare earth nitrate and the first mixed solution to obtain a second mixed solution; the rare earth nitrate and the first mixed solution are mixed under stirring; the stirring time is 10~30 min; 3) Mix ammonia water and the second mixed solution to obtain a third mixed solution; the ammonia water and the second mixed solution are mixed under stirring; the stirring time is 10~30 min; 4) Filter the third mixed solution by suction, and dry the obtained solid to obtain a mixed solid; 5) Mix a precursor salt of any one of Ru, Pt, Ir and Rh with water to obtain a fourth mixed solution; 6) Mix the fourth mixed solution and the mixed solid, dry the obtained gel at room temperature and then dry it, and treat it at 800 °C in an H2 atmosphere for 4 h. The ratio of H2 to Ar in the H2 atmosphere is 1:9 to obtain a rare earth oxide-silica supported noble metal catalyst; The rare earth oxide-silica supported noble metal catalyst comprises hydrophilic fumed silica with a specific surface area of 300-500 m 2 / g; Rare earth oxides distributed on the surface of the hydrophilic fumed silica; Noble metal nanoparticles with a size of 1~2 nm supported on the rare earth oxides; the noble metal nanoparticles are selected from Ru, Pt, Ir or Rh; The mass ratio of the hydrophilic fumed silica, noble metal nanoparticles and rare earth oxides is 100:1:3~4.

2. The preparation method according to claim 1, characterized in that, The molar ratio of the mixed solid, water in step 5), and the noble metal used is: 1:(1~20):(0.01~0.1).

3. The preparation method according to claim 1, characterized in that, The drying temperature in step 6) is 60~80 °C.

4. Application of the rare earth oxide-silica supported noble metal catalyst prepared by the preparation method described in claim 1 in the dry reforming of methane to produce syngas.

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