CN109012647A - A kind of diesel engine vent gas soot removing metal composite oxide catalyst and preparation method thereof - Google Patents

Abstract

The invention discloses a metal composite oxide catalyst for removing soot from diesel engine tail gas and a preparation method thereof. The general structural formula is Ag-Mn _x Ce _1-x O _y , where x=0.05-0.5. The invention has small particle size, uniform mixing, large specific surface area, low light-off temperature, good catalytic activity, low price, simple preparation method and synthesis process, and excellent industrial application prospect.

Description

A metal composite oxide catalyst for removing soot from diesel engine exhaust and its preparation method

technical field

The invention belongs to the technical field of catalyst materials, and in particular relates to a metal composite oxide catalyst for removing soot from diesel engine exhaust and a preparation method thereof.

Background technique

Diesel engines are widely used in large and medium-sized trucks and ships. Traditionally, diesel engines have been seldom favored by cars due to their bulkiness, lower power rating than gasoline engines (lower speed), higher noise and vibration, and serious soot particle (PM) emissions. Exhaust gas from diesel engines contains a considerable proportion of CO, NO _x , unburned organic hydrocarbons (HC) and soot particles (PM), which have a great negative impact on the atmospheric environment and human health. Due to the high ignition point of soot particles, the soot in the exhaust gas must be higher than 600°C to fully burn.

In situ regeneration of soot particulate filtration systems coated with catalysts has attracted much attention in recent years. Commonly used noble metal-based catalysts such as Pt, Rh, and Pd are difficult to popularize due to their high cost; while Ag-based catalysts are relatively economical due to their high activity, but generally have a high loading capacity, and have not yet achieved large-area industrial applications.

Contents of the invention

The purpose of the present invention is to overcome the defects of the prior art and provide a metal composite oxide catalyst for removing soot from diesel engine exhaust.

Another object of the present invention is to provide a preparation method of the above-mentioned metal composite oxide catalyst for removing soot from diesel engine exhaust.

Technical scheme of the present invention is as follows:

A metal composite oxide catalyst for removing soot from diesel engine tail gas, the general structure formula of which is Ag-Mn _x Ce _1-x O _y , where x=0.05-0.5.

The preparation method of the above-mentioned diesel engine exhaust soot removal metal composite oxide catalyst comprises the following steps:

(1) Weigh the following raw material components Ce(NO ₃ ) ₃ ·6H ₂ O, AgNO ₃ , Mn(NO ₃ ) ₂ , KOH and ammonia water according to the general structural formula;

(2) Mix Ce(NO ₃ ) ₃ ·6H ₂ O, Mn(NO ₃ ) ₂ and deionized water to make the first solution, mix AgNO ₃ and ammonia water to make the second solution, mix KOH and deionized water Mix to make KOH solution;

(3) Slowly drop the first solution and the second solution into the KOH solution at the same speed, while stirring and obtaining a uniform precipitation;

(4) Dry the above precipitate and grind it into powder, then roast it at 450-550° C. and cool it down to room temperature naturally to obtain the metal composite oxide catalyst for removing soot from diesel engine exhaust.

In a preferred embodiment of the present invention, in the first solution, both the concentrations of Ce(NO ₃ ) ₃ and Mn(NO ₃ ) ₂ are 0.1-0.3 mol/L.

In a preferred embodiment of the present invention, in the second solution, the concentration of AgNO ₃ is 0.05-0.2 mol/L, and the concentration of ammonia water is 1-3 mol/L.

In a preferred embodiment of the present invention, the concentration of the KOH solution is 1.0-3.0 mol/L.

In a preferred embodiment of the present invention, the drying in the step (4) is vacuum drying, the drying temperature is 60-120° C., and the drying time is 9-12 hours.

In a preferred embodiment of the present invention, the calcination time is 1-3 hours.

The beneficial effects of the present invention are: the doping of manganese element into the cerium oxide crystal phase in the present invention can significantly enhance the mobility of oxygen species and promote the formation of oxygen vacancies. As a carrier, manganese oxide helps to improve the oxidation ability of Ag catalyst, thereby reducing the loading of Ag and improving its economy. That is, the present invention has small particle size, uniform mixing, large specific surface area, low light-off temperature, good catalytic activity, low price, simple preparation method and synthesis process, and has excellent industrial application prospects.

Description of drawings

Fig. 1 is the XRD diffraction pattern of the metal composite oxide catalysts for removing soot from diesel engine exhaust prepared in Examples 1-6 of the present invention.

Fig. 2 is a graph showing the catalytic activity of the metal composite oxide catalysts for removing soot from diesel engine exhaust prepared in Examples 1-6 of the present invention.

Detailed ways

The technical solutions of the present invention will be further illustrated and described below through specific embodiments in conjunction with the accompanying drawings.

The test methods in the following examples, unless otherwise specified, are conventional methods; the soot used in the test materials in the following examples is German Printex, with an average particle size of 25nm. Other materials and reagents, unless otherwise specified, were purchased from conventional chemical reagent stores; the detection or testing methods involved, unless otherwise specified, were conventional methods.

Example 1

(1) According to the general structural formula Ag-Mn _x Ce _1-x O _y (x=0.05), weigh the following raw material components Ce(NO ₃ ) ₃ ·6H ₂ O, AgNO ₃ , Mn(NO ₃ ) ₂ , KOH and ammonia;

(2) Mix Ce(NO ₃ ) ₃ ·6H ₂ O, Mn(NO ₃ ) ₂ and deionized water to make the first solution (the concentrations of Ce(NO ₃ ) ₃ and Mn(NO ₃ ) ₂ are both 0.2 mol/L), mix AgNO ₃ and ammonia water to make the second solution (the concentration of AgNO ₃ is 0.2 mol/L, and the concentration of ammonia water is 1-3 mol/L), and mix KOH and deionized water to make a concentration of 1 mol /L KOH solution;

(3) Slowly drop the first solution and the second solution into the KOH solution at the same speed, while stirring mechanically to obtain a uniform precipitation;

(4) Vacuum-dry the above precipitate (60-120°C, 9-12h) and grind it into powder, then calcined at 500°C for 2h and then cool naturally to room temperature to obtain the metal composite oxide for removing soot from diesel engine exhaust catalyst;

The obtained diesel engine exhaust soot removal metal composite oxide catalyst was tested by XRD, and the results are shown in Figure 1: the material is cubic fluorite phase ceria oxide;

The obtained diesel engine exhaust soot removal metal composite oxide catalyst is tested for catalytic soot activity, and the obtained _T50 is 356°C (as shown in Figure 2): soot catalytic oxidation is carried out in an atmospheric pressure fixed bed stainless steel reaction tube. For evaluation, the contact condition is loose contact, and the mass ratio of catalyst to soot is 10:1. The _O2 content in the feed gas is 5%, the NO is 1000ppm, the rest is Ar, and the gas flow rate is 50mL.min-1. GC-2060 gas chromatograph was used to detect CO ₂ online, and T ₅₀ corresponds to the temperature when the conversion rate of soot is 50%.

Example 2

Preparation general formula is Ag-Mn _0.1 Ce _0.9 O _y (x=0.1) diesel engine exhaust soot removal metal composite oxide catalyst, catalyst activity evaluation method is the same as embodiment 1, XRD test result is shown in Fig. 1, gained Ag- The T ₅₀ of the Mn _0.1 Ce _0.9 O _y composite oxide catalyst is 321 °C (as shown in Figure 2).

Example 3

Preparation general formula is Ag-Mn _0.2 Ce _0.8 O _y (x=0.2) diesel engine exhaust soot removal metal composite oxide catalyst, catalyst activity evaluation method is the same as embodiment 1, XRD test result is shown in Fig. 1, gained Ag- The T ₅₀ of the Mn _0.2 Ce _0.8 O _y composite oxide catalyst is 350 °C (as shown in Figure 2).

Example 4

The preparation general formula is Ag-Mn _0.3 Ce _0.7 O _y (x=0.3) the diesel engine exhaust soot removes metal composite oxide catalyst, the catalyst activity evaluation method is the same as embodiment 1, the result is shown in Fig. 1, the obtained Ag-Mn _0.3 The _T50 of the Ce _0.7 O _y composite oxide catalyst is 353 °C (as shown in Figure 2).

Example 5

Preparation general formula is Ag-Mn _0.4 Ce _0.6 O _y (x=0.4) diesel engine exhaust soot removal metal composite oxide catalyst, catalyst activity evaluation method is the same as embodiment 1, XRD test result is shown in Fig. 1, gained Ag- The T ₅₀ of the Mn _0.4 Ce _0.6 O _y composite oxide catalyst is 368 °C (as shown in Figure 2).

Example 6

Preparation general formula is Ag-Mn _0.5 Ce _0.5 O _y (x=0.5) diesel engine exhaust soot removal metal composite oxide catalyst, catalyst activity evaluation method is the same as embodiment 1, XRD test result is shown in Fig. 1, gained Ag- The T ₅₀ of the Mn _0.5 Ce _0.5 O _y composite oxide catalyst is 372 °C (as shown in Figure 2).

Those of ordinary skill in the art know that when the technical solution of the present invention changes within the following ranges, the same or similar technical effects as those of the above-mentioned embodiments can still be obtained, and still belong to the protection scope of the present invention:

A metal composite oxide catalyst for removing soot from diesel engine tail gas, the general structure formula of which is Ag-Mn _x Ce _1-x O _y , where x=0.05-0.5.

The preparation method of the above-mentioned diesel engine exhaust soot removal metal composite oxide catalyst comprises the following steps:

(1) Weigh the following raw material components Ce(NO ₃ ) ₃ ·6H ₂ O, AgNO ₃ , Mn(NO ₃ ) ₂ , KOH and ammonia water according to the general structural formula;

(2) Mix Ce(NO ₃ ) ₃ ·6H ₂ O, Mn(NO ₃ ) ₂ and deionized water to make the first solution, mix AgNO ₃ and ammonia water to make the second solution, mix KOH and deionized water Mix to make KOH solution;

(3) Slowly drop the first solution and the second solution into the KOH solution at the same speed, while stirring and obtaining a uniform precipitation;

(4) Dry the above precipitate and grind it into powder, then roast it at 450-550° C. and cool it down to room temperature naturally to obtain the metal composite oxide catalyst for removing soot from diesel engine exhaust.

In the first solution, the concentrations of Ce(NO ₃ ) ₃ and Mn(NO ₃ ) ₂ are both 0.1˜0.3 mol/L. In the second solution, the concentration of AgNO ₃ is 0.05-0.2 mol/L, and the concentration of ammonia water is 1-3 mol/L. The concentration of the KOH solution is 1.0-3.0 mol/L. The drying in the step (4) is vacuum drying, the drying temperature is 60-120° C., and the drying time is 9-12 hours. The roasting time is 1-3 hours.

The above is only a preferred embodiment of the present invention, so the scope of the present invention cannot be limited accordingly, that is, equivalent changes and modifications made according to the patent scope of the present invention and the content of the specification should still be covered by the present invention In the range.

Claims (7)

1. a kind of diesel engine vent gas soot removes metal composite oxide catalyst, it is characterised in that: its general structure is Ag- Mn_xCe_1-xO_y, wherein x=0.05~0.5.

2. a kind of preparation method of diesel engine vent gas soot removing metal composite oxide catalyst as described in claim 1, It is characterized by comprising following steps:

(1) the following raw material component: Ce (NO is weighed according to the general structure₃)₃·6H₂O, AgNO₃, Mn (NO₃)₂, KOH and ammonia Water；

(2) by Ce (NO₃)₃·6H₂O、Mn(NO₃)₂It is mixed and made into the first solution with deionized water, by AgNO₃It mixes and makes with ammonium hydroxide At the second solution, KOH and deionized water are mixed and made into KOH solution；

(3) the first solution and the second solution are slowly dropped into KOH solution with identical speed, while stir and obtains uniform Precipitating；

(4) be ground into a powder after above-mentioned precipitating being dried, then in 450~550 DEG C roasting after cooled to room temperature to get The diesel engine vent gas soot removes metal composite oxide catalyst.

3. preparation method as claimed in claim 2, it is characterised in that: in first solution, Ce (NO₃)₃With Mn (NO₃)₂'s Concentration is 0.1~0.3mol/L.

4. preparation method as claimed in claim 2, it is characterised in that: in second solution, AgNO₃Concentration be 0.05~ 0.2mol/L, the concentration of ammonium hydroxide are 1~3mol/L.

5. preparation method as claimed in claim 2, it is characterised in that: the concentration of the KOH solution is 1.0~3.0mol/L.

6. preparation method as claimed in claim 2, it is characterised in that: the drying of the step (4) is vacuum drying, dry temperature Degree is 60~120 DEG C, and the time is 9~12h.

7. preparation method as claimed in claim 2, it is characterised in that: the time of the roasting is 1~3h.