CN106423134B - A kind of preparation method of base metal soot combustion catalyst - Google Patents

Abstract

The present invention relates to a kind of preparation methods of base metal soot combustion catalyst, and in particular to the Pr of meso-hole structure _x Zr _1‑x O ₂ The preparation method of solid solution catalyst, using Pr (NO₃)₃For praseodymium source, with ZrOCl₂Or Zr (NO₃)₄For zirconium source, triblock copolymer F127 or P123 are that template prepares mesoporous Pr _x Zr _1‑x O₂Solid solution catalyst.Resulting Pr _x Zr _1‑x O₂It is both mesoporous material, with the advantages that large specific surface area, pore volume is big, and pore size is controllable；It is solid solution again, has oxygen storage capacity strong, the advantages that redox ability is strong, and thermal stability is high.

Description

A kind of preparation method of non-precious metal soot combustion catalyst

technical field

The invention relates to a preparation method of a non-precious metal soot combustion catalyst, in particular to a preparation method of a _{PrxZr1 - xO2} solid solution catalyst with a mesoporous structure, and belongs to the technical field of applied catalysis.

Background technique

As the main pollutant in diesel vehicle exhaust, soot particulate matter (PM) is the "culprit" in the formation of smog, causing great harm to human health and living environment. The development of clean energy, the development of diesel engine purification technology and the aftertreatment of diesel vehicle exhaust are the three main aspects of controlling pollutant emissions. However, due to the constraints of technical level and economic cost, clean fuel and in-plane purification technology have not been widely used. From the current point of view, the most direct and effective method is to use a particulate filter (DPF), a post-processing device specially designed for the purification of soot particles outside the machine to capture soot particles and oxidize them to CO ₂ . . However, the combustion temperature of soot particles is relatively high, in the range of 550-600 °C, which is much higher than the actual emission temperature range of diesel vehicle exhaust (200-400 °C). Therefore, a catalyst must be used to catalyze the combustion of PM, thereby realizing the regenerative use of DPF.

Catalysts used to catalyze the oxidation of soot particles can generally be divided into two categories, noble metal catalysts and non-precious metal catalysts. Precious metal catalysts are mainly made of precious metals with less loading as active components, which are coated on the surface of the carrier. Although noble metal catalysts have excellent catalytic oxidation performance, their poor thermal stability, easy deactivation in contact with water, "sulfur poisoning" reactions, and high production costs restrict their practical application. In recent years, composite metal oxides based on rare earth metal oxides and transition metal oxides as dopants have shown strong advantages in catalyzing soot combustion. In particular, the solid solution formed by this composite metal oxide has a positive effect on reducing the activation energy of soot combustion, strengthening the oxygen storage capacity of the material, and improving the redox performance of the catalyst due to the existence of lattice defects. The inherent large specific surface area, large pore volume, and controllable pore size of mesoporous materials are of great help to consolidate and expand the physical and chemical properties of materials. Therefore, mesoporous solid solution materials can be studied as a new type of catalyst for catalyzing soot combustion.

SUMMARY OF THE INVENTION

The invention provides a preparation method of a non-precious metal soot combustion catalyst, specifically a preparation method of a Pr _x Zr _1-x O ₂ solid solution catalyst with a mesoporous structure, through the following steps:

(1) According to the molar ratio of Pr to Zr=x:1-x (wherein, 0<x≤0.4), respectively weigh enough Pr(NO ₃ ) ₃ and metal zirconium salt, dissolve in anhydrous at room temperature In ethanol, prepare an ethanol solution with a concentration of 0.4~1mol/L, and then mix the two evenly;

(2) According to the mass ratio of (Pr(NO ₃ ) ₃ + metal zirconium salt) to template agent of 20:1~5:1, weigh a sufficient amount of template agent and dissolve it in absolute ethanol to prepare a concentration of 0.05~ 0.5g/mL solution;

(3) Under the condition of heating in a water bath at 40~60°C and vigorous stirring, add the ethanol solution of the template agent dropwise to the mixed solution of step (1);

(4) Add NaOH ethanol solution to the mixture prepared in step (3) to adjust the pH to 9~10, and continue stirring for 3~5h;

(5) Transfer the mixture obtained in step (4) into a conical flask, and cultivate in a constant temperature and humidity box with a temperature of 50-70°C and a humidity of 40-60% for 24-48 hours;

(6) The mixture obtained in step (5) was filtered, washed with absolute ethanol, dried at 80-120 °C for 12-24 h, and the obtained powder was calcined at 500-800 °C for 3-5 h to obtain mesoporous Structure of _{PrxZr1 - xO2} solid solution catalyst.

The metal zirconium salt is Zr(NO ₃ ) ₄ or ZrOCl ₂ .

The templating agent is F127 or P123.

The beneficial effects of the present invention are:

(1) The obtained mesoporous Pr _x Zr _1-x O ₂ solid solution has a large specific surface area (specific surface area of 110~140 m ² /g) and a large pore volume (pore volume of 0.17~2.4cc/g) ), the pore arrangement rules;

(2) The lattice defects existing in the Pr _x Zr _1-x O ₂ solid solution can significantly improve the oxygen exchange capacity of the material, and the doped ZrO ₂ can greatly improve the oxygen storage capacity of the material;

(3) _In the Pr _x Zr _1-x O solid solution, praseodymium exists in the form of Pr ₆ O ₁₁ , which has multiple stable oxidation states and has a higher oxygen exchange capacity _{than CeO 2 at} low temperature, especially it The advantage that the oxygen storage capacity will not decrease after calcination at high temperature is conducive to maintaining the stability of the catalyst, which plays an extremely important role in the field of catalysis.

Description of drawings

1 is a TEM image of the Pr _0.1 Zr _0.9 O ₂ solid solution catalyst with a mesoporous structure prepared in Example 1.

Detailed ways

The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

Example 1

(1) According to the molar ratio of Pr to Zr=0.1:0.9, weigh 0.004mol (1.74g) Pr(NO ₃ ) ₃ ·6H ₂ O and 0.036mol (11.6g) ZrOCl ₂ ·8H ₂ O and dissolve in 10mL respectively and 90 mL of dehydrated ethanol, after ultrasonication and stirring, were respectively prepared into an ethanol solution with a concentration of 0.4 mol/L, and the two were mixed evenly;

(2) According to the mass ratio of (Pr(NO ₃ ) ₃ ·6H ₂ O+ZrOCl ₂ ·8H ₂ O) to template F127 of 20:1, weigh 0.67g of triblock copolymer F127 and dissolve it in 13mL of anhydrous In ethanol, prepare a solution with a concentration of 0.05g/mL;

(3) The mixed solution of step (1) was stirred in a water bath at 40°C, and the ethanol solution of F127 was added dropwise to the mixed solution of step (1);

(4) Add NaOH ethanol solution to the mixture obtained in step (3) to adjust the pH to 9, and continue stirring for 3h;

(5) Transfer the mixture obtained in step (4) into a conical flask, and cultivate for 48 hours in a constant temperature and humidity box with a temperature of 50°C and a humidity of 40%;

(6) The mixture obtained in step (5) was filtered, washed three times with absolute ethanol, dried at 80 °C for 24 h, and the obtained powder was calcined at 500 °C for 5 h to obtain Pr _0.1 Zr _0.9 O with a mesoporous structure ₂ solid solution catalyst.

Catalytic activity test: Take 90mg of the prepared Pr _0.1 Zr _0.9 O ₂ solid solution catalyst and 10mg of soot powder, and mix them evenly; then add 300mg of 20-40 mesh quartz sand and mix them evenly, then put them in a quartz tube padded with quartz wool, Placed in a fixed-bed reactor, first introduced high-purity Ar gas with a flow rate of 50 mL/min, pretreated at 300 °C for 30 minutes to remove adsorbed water and easily decomposed carbonate; after the reactor was cooled to room temperature, introduced A 10% O ₂ +Ar mixture with a flow rate of 200 mL/min, and the exhaust gas was detected by on-line mass spectrometry; the temperature was raised at a rate of 10 °C/min until the soot was completely burned. According to the exhaust gas data detected by mass spectrometry, the soot was obtained under the action of the catalyst. The light-off temperature is 268°C.

Example 2

(1) According to the molar ratio of Pr to Zr=0.2:0.8, weigh 0.008mol (3.48g) Pr(NO ₃ ) ₃ ·6H ₂ O and 0.032mol (10.31g) ZrOCl ₂ ·8H ₂ O and dissolve in 16mL respectively and 64 mL of dehydrated ethanol, respectively, after ultrasonication and stirring, were prepared into solutions with a concentration of 0.5 mol/L, and the two were mixed evenly;

(2) According to the mass ratio of (Pr(NO ₃ ) ₃ ·6H ₂ O+ZrOCl ₂ ·8H ₂ O) to template F127 of 10:1, weigh 1.38g of triblock copolymer F127 and dissolve it in 13.8mL of In water ethanol, prepare a solution with a concentration of 0.1 g/mL;

(3) The mixed solution in step (1) was stirred in a water bath at 50°C, and the ethanol solution of F127 was added dropwise to the mixed solution;

(4) Add NaOH ethanol solution to the mixture obtained in step (3) to adjust the pH to 9.5, and continue stirring for 4 hours;

(5) Transfer the mixture obtained in step (4) into a conical flask, and cultivate for 36 hours in a constant temperature and humidity box with a temperature of 60°C and a humidity of 50%;

(6) The mixture obtained in step (5) was filtered, washed with absolute ethanol for 3 times, dried at 100 °C for 18 h, and the obtained powder was calcined at 600 °C for 4 h to obtain Pr _0.2 Zr _0.8 O with a mesoporous structure ₂ solid solution catalyst.

The catalytic activity of the Pr _0.2 Zr _0.8 O ₂ solid solution catalyst prepared in this example was tested according to the catalytic activity test method of Example 1. The test result showed that the light-off temperature of soot under the action of the catalyst was 275°C.

Example 3

(1) According to the mole ratio of Pr to Zr=0.3:0.7, weigh 0.012mol (5.22g) Pr(NO ₃ ) ₃ ·6H ₂ O and 0.028mol (12.02g) Zr(NO ₃ ) ₄ ·5H ₂ O, Dissolved in 12mL and 28mL of absolute ethanol, respectively, prepared into solutions with a concentration of 1mol/L after ultrasonication and stirring, and mixed the two evenly;

(2) According to the mass ratio of (Pr(NO ₃ ) ₃ ·6H ₂ O+Zr(NO ₃ ) ₄ ·5H ₂ O) to template P123 of 5:1, weigh 3.45g of triblock copolymer P123 to dissolve In 6.9mL of absolute ethanol, prepare a solution with a concentration of 0.5g/mL;

(3) stirring the mixed solution in step (1) in a water bath at 60°C, and adding the ethanol solution of P123 to the mixed solution dropwise;

(4) Add NaOH ethanol solution to the mixture obtained in step (3) to adjust the pH to 10, and continue stirring for 5h;

(5) Transfer the mixture obtained in step (4) into a conical flask, and cultivate for 24 hours in a constant temperature and humidity box with a temperature of 70°C and a humidity of 60%;

(6) The mixture obtained in step (5) was filtered, washed with absolute ethanol for 3 times, dried at 120 °C for 12 h, and the obtained powder was calcined at 700 °C for 3 h to obtain Pr _0.3 Zr _0.7 O with a mesoporous structure ₂ solid solution catalyst.

The catalytic activity of the Pr _0.3 Zr _0.7 O ₂ solid solution catalyst prepared in this example was tested according to the catalytic activity test method of Example 1. The test result showed that the light-off temperature of soot under the action of the catalyst was 287°C.

Claims (8)

1. a preparation method of a non-precious metal soot combustion catalyst, comprising the following steps: (1) Weigh Pr(NO ₃ ) ₃ and metal zirconium salt, dissolve them in absolute ethanol at room temperature to make a solution, and then mix the two evenly; (2) Dissolve the template agent in absolute ethanol to make a solution; (3) Under the condition of heating in a water bath and vigorous stirring, the ethanol solution of the template agent is added dropwise to the mixed solution in step (1); (4) Add NaOH ethanol solution to the mixture obtained in step (3) to adjust the pH to 9~10, and continue stirring for 3~5h; (5) Incubate the mixture obtained in step (4) at a temperature of 50-70°C and a humidity of 40-60% for 24-48 hours; (6) The mixture obtained in step (5) was filtered, washed with absolute ethanol, dried at 80-120°C for 12-24h, and the obtained powder was calcined at 500-800°C for 3-5h to obtain the medium. Pore-structured _{PrxZr1 - xO2} solid solution catalyst. 2 . The preparation method according to claim 1 , wherein the metal zirconium salt is Zr(NO ₃ ) ₄ or ZrOCl ₂ . 3 . 3 . The preparation method according to claim 1 , wherein the molar ratio of Pr to Zr in step (1)=x:1-x, wherein 0<x≦0.4. 4 . 4. The preparation method according to claim 1, characterized in that, in step (1), Pr(NO ₃ ) ₃ is dissolved in a solution made from anhydrous ethanol and a metal zirconium salt is dissolved in a solution made from anhydrous ethanol. The concentration is 0.4~1mol/L. 5 . The preparation method according to claim 1 , wherein the templating agent in step (2) is F127 or P123. 6 . 6 . The preparation method according to claim 1 , wherein in step (2), the mass ratio of (Pr(NO ₃ ) ₃ + metal zirconium salt) to the template agent is 20:1 to 5:1. 7 . 7 . The preparation method according to claim 1 , wherein the concentration of the ethanol solution of the template agent in step (2) is 0.05-0.5 g/mL. 8 . 8 . The preparation method according to claim 1 , wherein the heating temperature of the water bath in step (3) is 40-60° C. 9 .