Enhanced hydrocarbon conversion catalyst and preparation method thereof

Abstract

The present invention provides an enhanced hydrocarbon conversion catalyst and a preparation method thereof, and relates to the technical field of catalyst preparation, the catalyst comprises a carrier and a catalyst coating arranged on the carrier, the catalyst coating comprises alumina and an active component, and the mass ratio of the alumina to the active component is 1: 1-10. According to the preparation method disclosed by the invention, the conversion capability of Pt and Pd to hydrocarbons is enhanced by virtue of the sol treatment of the Pt-Pd-Mo-Nb precursor solution and the design of step-by-step addition of the Nb2O5-MoO3-Sm2O3-CeO2-ZrO2 composite oxide auxiliary agent; in the preparation process, an internal micropore system of a composite condensate is constructed by selectively dissolving ZnO, so that the internal diffusion resistance of gas is reduced, the utilization rate of active components of the coating is favorably improved, and finally, the catalytic conversion capability of the coating on hydrocarbon is improved under the condition that precious metal is not increased.

Description

Technical Field

[0001] The present invention relates to the technical field of catalyst preparation, and particularly relates to an enhanced hydrocarbon conversion catalyst and a preparation method thereof. Background Art

[0002] Due to the relatively compact volume of the engine compartment of motorcycles, the post-treatment catalyst often cannot be directly arranged at the engine exhaust outlet (also known as close-coupled arrangement) like that of light-duty vehicles; therefore, there will be a certain temperature loss when the engine exhaust gas reaches the catalyst inlet through the exhaust pipe, which is not conducive to the efficient catalytic conversion of NMHC. Usually, the solution is to increase the content of coated noble metals (such as Pt or Pd, etc.) to improve the hydrocarbon conversion performance, but this method will bring a substantial increase in the catalyst cost and is not conducive to economy; therefore, improving the hydrocarbon conversion ability of the coating body and meeting the regulatory requirements for THC and NMHC emissions of motorcycles without the need to use a large amount of noble metals is the key research direction in the field of motorcycle post-treatment systems at present. Summary of the Invention

[0003] The purpose of the present invention is to overcome the deficiencies existing in the prior art and provide an enhanced hydrocarbon conversion catalyst and a preparation method thereof, which can effectively solve the problem of hydrocarbon emission control of motorcycles without increasing the amount of noble metals used.

[0004] The technical solution adopted by the present invention is as follows:

[0005] An enhanced hydrocarbon conversion catalyst, which includes a carrier and a catalyst coating provided on the carrier, and the catalyst coating includes alumina and an active component, and the mass ratio of alumina to the active component is 1:1 to 10.

[0006] Preferably, for the enhanced hydrocarbon conversion catalyst, the active component is a Pt-Pd-Nb2O5-MoO3-Sm2O3-CeO2-ZrO2 composite solidified product.

[0007] Preferably, for the enhanced hydrocarbon conversion catalyst, by mass percentage, the Pt-Pd-Nb2O5-MoO3-Sm2O3-CeO2-ZrO2 composite solidified product includes 1-2% Pt, 1-2% Pd, 5-10% Nb2O5, 5-8% MoO3, 3-6% Sm2O3, 30-40% CeO2, and 32-55% ZrO2.

[0008] Preferably, for the enhanced hydrocarbon conversion catalyst, the coating amount of the catalyst coating is 50-200 g / L.

[0009] The present invention also provides a preparation method of an enhanced hydrocarbon conversion catalyst, which includes the following steps:

[0010] Step S1. Mix platinum nitrate, palladium nitrate, ammonium molybdate, ammonium niobium oxalate and deionized water to obtain a Pt-Pd-Mo-Nb mixed solution. Then, add ethylenediamine to the Pt-Pd-Mo-Nb mixed solution in sequence, and then add ammonia water to adjust the pH of the mixed solution to 8-10. Then, heat and stir the Pt-Pd-Mo-Nb mixed solution to obtain a Pt-Pd-Mo-Nb sol compound solution;

[0011] Step S2. Completely dissolve cerium nitrate and zirconium nitrate in deionized water, and then add them to the Pt-Pd-Mo-Nb sol compound solution obtained in Step S1 to obtain a composite solution. Then, add zinc acetate to the composite solution and stir, and then heat to obtain a mixed solution;

[0012] Step S3. Dry the mixed solution prepared in Step S2, and then calcine to obtain a composite powder;

[0013] Step S4. Crush the composite powder prepared in Step S3, then add a hydrochloric acid solution to the crushed composite powder and stir to form a suspension. Then, perform solid-liquid phase separation on the above suspension, wash, and finally add deionized water to the washed solid to prepare a suspension;

[0014] Step S5. Add samarium nitrate to the suspension prepared in Step S4, then add glycine and stir, then add an ammonium oxalate solution and continue to stir for at least 2 h. Finally, dry the above suspension to obtain a composite solid;

[0015] Step S6. Mix alumina and the composite solid prepared in Step S5, and add deionized water to form a slurry. Ball mill the slurry to obtain a coating slurry;

[0016] Step S7. Coat the coating slurry on a monolithic carrier. After coating, calcine the monolithic carrier to obtain a promoted hydrocarbon conversion catalyst.

[0017] Preferably, in the method for preparing the promoted hydrocarbon conversion catalyst, in Step S1, the addition amount of ethylenediamine is 5-10% of the total amount of the elements in the Pt-Pd-Mo-Nb mixed solution, the heating temperature is 50-60 °C, and the heating time is 3-4 h.

[0018] Preferably, in the method for preparing the promoted hydrocarbon conversion catalyst, in Step S2, the addition amount of zinc acetate is 5-10% of the mass of the solidified product of the composite solution, the stirring time is 2-4 h, the heating temperature is 70-80 °C, and the heating time is 4-6 h.

[0019] Preferably, in the method for preparing the enhanced hydrocarbon conversion catalyst, in steps S3 and S5, the drying method is microwave drying, and the drying rate of microwave drying is controlled to be > 90%; the calcination temperature in step S3 is 400 - 450 °C, and the calcination time is 2 - 4 h.

[0020] Preferably, in the method for preparing the enhanced hydrocarbon conversion catalyst, in step S4, the mass fraction of hydrochloric acid in the hydrochloric acid solution is 5 - 10%, the mass ratio of the hydrochloric acid solution to the composite powder is 2 - 3:1, the stirring time is 2 - 3 h, and the number of washing times is ≥ 3 times.

[0021] Preferably, in the method for preparing the enhanced hydrocarbon conversion catalyst, in step S5, the addition amount of glycine is 3 - 5% of the mass of samarium in samarium nitrate, and the molar ratio of ammonium oxalate to samarium is 2 - 3:1; in step S6, the specific surface area of alumina is 100 - 200 m 2 / g, the loose bulk density is 0.5 - 1.0 g / mL, and the D90 of the coating slurry is 10 - 20 um.

[0022] Preferably, in the method for preparing the enhanced hydrocarbon conversion catalyst, in step S7, the calcination is specifically: calcining at 300 - 400 °C for 1 - 2 h, and then raising the temperature to 500 - 600 °C and calcining for 1 - 2 h.

[0023] Advantages of the present invention:

[0024] (1) For the enhanced hydrocarbon conversion catalyst and its preparation method of the present invention, through the solubilization treatment of the Pt - Pd - Mo - Nb precursor solution and the step - by - step addition of the Nb2O5 - MoO3 - Sm2O3 - CeO2 - ZrO2 composite oxide additive, an active center with Pt - Pd as the main catalytic component and Nb2O5 - MoO3 as the co - catalytic component is constructed. The Nb2O5 - MoO3 oxide plays a synergistic role to enhance the overall catalytic activity; subsequently, a CeO2 - ZrO2 composite oxygen storage and release compound is covered around the active center to enhance the transfer process of O2 to the catalytic active center, which helps the active components to efficiently catalyze the oxidation of hydrocarbons; finally, the added Sm2O3 component is coated on the outer layer, and its high thermal stability reduces the thermal aging effect of high temperature on the inner - layer components and improves the anti - aging performance of the catalyst.

[0025] (2) For the enhanced hydrocarbon conversion catalyst and its preparation method of the present invention, during the preparation process, an internal microporous system of the composite solid is constructed by selectively dissolving ZnO, thereby reducing the internal diffusion resistance of the gas, which is beneficial to improving the utilization rate of the coating active components, and finally realizing the improvement of the catalytic conversion ability of the coating to hydrocarbons without increasing precious metals. Detailed implementation manners

[0026] The present invention will be further described below in conjunction with specific embodiments.

[0027] Example 1

[0028] A hydrocarbon conversion enhancing catalyst includes a straight-through honeycomb metal carrier and a catalyst coating disposed on the carrier. The carrier has a specification of Ф52×112mm, a pore density of 300 cpsi, and an inner core volume of 0.2L. The catalyst coating includes alumina and an active component, and the mass ratio of alumina to the active component is 1:1. The active component is a Pt-Pd-Nb2O5-MoO3-Sm2O3-CeO2-ZrO2 composite solidified product. By mass percentage, the Pt-Pd-Nb2O5-MoO3-Sm2O3-CeO2-ZrO2 composite solidified product includes 1% Pt, 1% Pd, 5% Nb2O5, 5% MoO3, 3% Sm2O3, 30% CeO2, and 55% ZrO2. The coating amount of the catalyst coating is 100g / L, and the loading amount of noble metal Pt is 14.2g / ft 3 and the loading amount of noble metal Pd is 14.2g / ft 3 .

[0029] The preparation method of the hydrocarbon conversion enhancing catalyst of this example includes the following steps:

[0030] Step S1. Mix platinum nitrate, palladium nitrate, ammonium molybdate, ammonium niobium oxalate, and deionized water to obtain a Pt-Pd-Mo-Nb mixed solution. Then, successively add ethylenediamine to the Pt-Pd-Mo-Nb mixed solution. The addition amount of ethylenediamine is 5% of the total amount of the single substances in the Pt-Pd-Mo-Nb mixed solution. Subsequently, add ammonia water to adjust the pH of the mixed solution to 8. Then, heat the Pt-Pd-Mo-Nb mixed solution at 50°C for 4h, and keep stirring during the heating process to obtain a Pt-Pd-Mo-Nb sol compound solution;

[0031] Step S2. Completely dissolve cerium nitrate and zirconium nitrate in deionized water, and then add it to the Pt-Pd-Mo-Nb sol compound solution obtained in step S1 to obtain a composite solution. Then, add zinc acetate to the composite solution and stir for 2h. The addition amount of zinc acetate is 5% of the mass of the solidified product of the composite solution. After that, heat at 70°C for 6h to obtain a mixed solution;

[0032] Step S3. Microwave dry the mixed solution prepared in step S2, control the drying rate of microwave drying to be 92%, and then calcine in a temperature-controlled muffle furnace to obtain a composite powder. The calcination temperature is 400°C, and the calcination time is 4h;

[0033] Step S4. Crush the composite powder prepared in step S3 to a D90 of 20 μm. Subsequently, stir the crushed composite powder and add a 5% mass fraction hydrochloric acid solution and stir for 2 h to form a suspension. The mass ratio of the hydrochloric acid solution to the composite powder is 2:1. Then, perform solid-liquid separation on the above suspension, wash the solid phase with deionized water, and then repeat the above solid-liquid separation and deionized water washing processes 3 times. Finally, add deionized water to the washed solid phase to prepare a suspension;

[0034] Step S5. Add samarium nitrate to the suspension prepared in step S4, then add glycine and stir. The addition amount of glycine is 3% of the mass of samarium in samarium nitrate. Then, add ammonium oxalate solution and continue to stir for 3 h. The molar ratio of ammonium oxalate to samarium is 2:1. Finally, microwave-dry the above suspension, control the drying rate of microwave drying to be 93%, and obtain a composite solidified product;

[0035] Step S6. Mix alumina and the composite solidified product prepared in step S5. The specific surface area of alumina is 100 m 2 / g, and the loose bulk density is 1.0 g / mL. Add deionized water to form a slurry, and ball-mill the slurry to obtain a coating slurry. Control the D90 of the coating slurry during ball-milling to be 10 μm;

[0036] Step S7. Coat the coating slurry on a straight-through honeycomb metal carrier. After coating, calcine the monolithic carrier at 300 °C for 2 h, and then raise the temperature to 500 °C and calcine for 2 h to obtain a promoted hydrocarbon conversion catalyst.

[0037] Example 2

[0038] A promoted hydrocarbon conversion catalyst, comprising a straight-through honeycomb metal carrier and a catalyst coating provided on the carrier. The carrier has a specification of Ф52×112 mm, a pore density of 300 cpsi, and an inner core volume of 0.2 L. The catalyst coating includes alumina and an active component. The mass ratio of alumina to the active component is 1:1; the active component is a Pt-Pd-Nb2O5-MoO3-Sm2O3-CeO2-ZrO2 composite solidified product; by mass percentage, the Pt-Pd-Nb2O5-MoO3-Sm2O3-CeO2-ZrO2 composite solidified product includes 2% Pt, 2% Pd, 10% Nb2O5, 8% MoO3, 6% Sm2O3, 40% CeO2, and 32% ZrO2. The coating amount of the catalyst coating is 100 g / L, and the loading amount of the noble metal Pt is 28.3 g / ft 3 , and the loading amount of the noble metal Pd is 28.3 g / ft 3 .

[0039] The preparation method of the promoted hydrocarbon conversion catalyst of this example includes the following steps:

[0040] Step S1. Mix platinum nitrate, palladium nitrate, ammonium molybdate, ammonium niobium oxalate and deionized water to obtain a Pt-Pd-Mo-Nb mixed solution. Then, add ethylenediamine to the Pt-Pd-Mo-Nb mixed solution in sequence. The addition amount of ethylenediamine is 5% of the total amount of the single substances in the Pt-Pd-Mo-Nb mixed solution. Subsequently, add ammonia water to adjust the pH of the mixed solution to 8. Then, heat the Pt-Pd-Mo-Nb mixed solution at 50 °C for 4 h and stir to obtain a Pt-Pd-Mo-Nb sol compound solution;

[0041] Step S2. Completely dissolve cerium nitrate and zirconium nitrate in deionized water, and then add them to the Pt-Pd-Mo-Nb sol compound solution obtained in Step S1 to obtain a composite solution. Then, add zinc acetate to the composite solution and stir for 2 h. The addition amount of zinc acetate is 5% of the mass of the solidified product of the composite solution. After that, heat at 70 °C for 6 h to obtain a mixed solution;

[0042] Step S3. Microwave-dry the mixed solution prepared in Step S2, control the drying rate of the microwave drying to be 92%, and then calcine at 400 °C for 4 h to obtain a composite powder;

[0043] Step S4. Crush the composite powder prepared in Step S3 to D90 of 20 μm. Then, stir the crushed composite powder and add a hydrochloric acid solution with a mass fraction of 5% and stir for 2 h to form a suspension. The mass ratio of the hydrochloric acid solution to the composite powder is 2:1. Then, perform solid-liquid separation on the above suspension, wash the solid phase with deionized water, and then repeat the above solid-liquid separation and deionized water washing processes 3 times. Finally, add deionized water to the washed solid phase to prepare a suspension;

[0044] Step S5. Add samarium nitrate to the suspension prepared in Step S4, then add glycine and stir. The addition amount of glycine is 3% of the mass of samarium in samarium nitrate. Then, add ammonium oxalate solution and continue to stir for 3 h. The molar ratio of ammonium oxalate to samarium is 2:1. Finally, microwave-dry the above suspension, control the drying rate of the microwave drying to be 93% to obtain a composite solidified product;

[0045] Step S6. Mix alumina and the composite solidified product prepared in Step S5. The specific surface area of alumina is 100 m 2 / g, and the loose bulk density is 1.0 g / mL, and add deionized water to form a slurry. Ball-mill the slurry to obtain a coating slurry, and control D90 of the ball-milling of the coating slurry to be 10 μm;

[0046] Step S7. Coat the slurry for coating on the straight-through honeycomb monolithic carrier. After the coating is completed, calcine the monolithic carrier at 300 °C for 2 h, and then raise the temperature to 500 °C and calcine for 2 h to obtain the enhanced hydrocarbon conversion catalyst.

[0047] Example 3

[0048] An enhanced hydrocarbon conversion catalyst, comprising a straight-through honeycomb metal carrier and a catalyst coating provided on the carrier. The carrier has a specification of Ф52×112 mm, a pore density of 300 cpsi, and an inner core volume of 0.2 L. The catalyst coating includes alumina and an active component, and the mass ratio of alumina to the active component is 1:10; the active component is a Pt-Pd-Nb2O5-MoO3-Sm2O3-CeO2-ZrO2 composite solidified product; by mass percentage, the Pt-Pd-Nb2O5-MoO3-Sm2O3-CeO2-ZrO2 composite solidified product includes 1% Pt, 1% Pd, 5% Nb2O5, 5% MoO3, 3% Sm2O3, 30% CeO2, and 55% ZrO2. The coating amount of the catalyst coating is 100 g / L, and the loading amount of the noble metal Pt is 25.7 g / ft 3 , and the loading amount of the noble metal Pd is 25.7 g / ft 3 .

[0049] The preparation method of the enhanced hydrocarbon conversion catalyst of this example includes the following steps:

[0050] Step S1. Mix platinum nitrate, palladium nitrate, ammonium molybdate, ammonium niobium oxalate, and deionized water to obtain a Pt-Pd-Mo-Nb mixed solution. Then, successively add ethylenediamine to the Pt-Pd-Mo-Nb mixed solution. The addition amount of ethylenediamine is 10% of the total amount of the single substances in the Pt-Pd-Mo-Nb mixed solution. Subsequently, add ammonia water to adjust the pH of the mixed solution to 10. Then, heat the Pt-Pd-Mo-Nb mixed solution at 60 °C for 3 h and stir to obtain a Pt-Pd-Mo-Nb sol compound solution;

[0051] Step S2. Completely dissolve cerium nitrate and zirconium nitrate in deionized water, and then add it to the Pt-Pd-Mo-Nb sol compound solution obtained in Step S1 to obtain a composite solution. Then, add zinc acetate to the composite solution and stir for 4 h. The addition amount of zinc acetate is 10% of the mass of the solidified product of the composite solution. After that, heat at 80 °C for 4 h to obtain a mixed solution;

[0052] Step S3. Microwave-dry the mixed solution prepared in Step S2, control the drying rate of the microwave drying to be 93%, and then calcine at 450 °C for 2 h to obtain a composite powder;

[0053] Step S4. Crush the composite powder prepared in step S3 to a D90 of 30 um. Then, stir the crushed composite powder and add a 10% mass fraction hydrochloric acid solution and stir for 3 h to form a suspension. The mass ratio of the hydrochloric acid solution to the composite powder is 3:1. Then, perform solid-liquid phase separation on the above suspension, wash the solid phase with deionized water, and then repeat the above solid-liquid phase separation and deionized water washing process 4 times. Finally, add deionized water to the washed solid phase to prepare a suspension;

[0054] Step S5. Add samarium nitrate to the suspension prepared in step S4, then add glycine and stir. The addition amount of glycine is 5% of the mass of samarium in samarium nitrate. Then, add ammonium oxalate solution and continue to stir for 3 h. The molar ratio of ammonium oxalate to samarium is 3:1. Finally, microwave dry the above suspension, and control the drying rate of microwave drying to be 91% to obtain a composite solidified product;

[0055] Step S6. Mix alumina with the composite solidified product prepared in step S5. The specific surface area of alumina is 200 m 2 / g, the loose bulk density is 0.5 g / mL, and add deionized water to form a slurry. Ball mill the slurry to obtain a slurry, and control the D90 of the slurry ball milling to be 20 um;

[0056] Step S7. Coat the slurry on a straight-through honeycomb monolithic carrier. After coating, bake the monolithic carrier at 400 °C for 1 h, and then raise the temperature to 600 °C and bake for 1 h to obtain a strengthened hydrocarbon conversion catalyst.

[0057] Example 4

[0058] A strengthened hydrocarbon conversion catalyst, comprising a straight-through honeycomb metal carrier and a catalyst coating provided on the carrier. The carrier specifications are Ф52×112 mm, the pore density is 300 cpsi, and the inner core volume is 0.2 L. The catalyst coating includes alumina and an active component, and the mass ratio of alumina to the active component is 1:10; the active component is a Pt-Pd-Nb2O5-MoO3-Sm2O3-CeO2-ZrO2 composite solidified product; by mass percentage, the Pt-Pd-Nb2O5-MoO3-Sm2O3-CeO2-ZrO2 composite solidified product includes 2% Pt, 2% Pd, 10% Nb2O5, 8% MoO3, 6% Sm2O3, 40% CeO2, and 32% ZrO2. The coating amount of the catalyst coating is 100 g / L, and the loading amount of the noble metal Pt is 51.5 g / ft 3 , and the loading amount of the noble metal Pd is 51.5 g / ft 3 .

[0059] The preparation method of the strengthened hydrocarbon conversion catalyst of this example includes the following steps:

[0060] Step S1. Mix platinum nitrate, palladium nitrate, ammonium molybdate, ammonium niobium oxalate and deionized water to obtain a Pt-Pd-Mo-Nb mixed solution. Then, add ethylenediamine to the Pt-Pd-Mo-Nb mixed solution in sequence. The addition amount of ethylenediamine is 10% of the total amount of the elements in the Pt-Pd-Mo-Nb mixed solution. Subsequently, add ammonia water to adjust the pH of the mixed solution to 10. Then, heat the Pt-Pd-Mo-Nb mixed solution at 60 °C for 3 h and stir to obtain a Pt-Pd-Mo-Nb sol compound solution;

[0061] Step S2. Completely dissolve cerium nitrate and zirconium nitrate in deionized water, and then add them to the Pt-Pd-Mo-Nb sol compound solution obtained in Step S1 to obtain a composite solution. Then, add zinc acetate to the composite solution and stir for 4 h. The addition amount of zinc acetate is 10% of the mass of the solidified matter in the composite solution. After that, heat at 80 °C for 4 h to obtain a mixed solution;

[0062] Step S3. Microwave-dry the mixed solution prepared in Step S2, control the drying rate of microwave drying to be 93%, and then calcine at 450 °C for 2 h to obtain a composite powder;

[0063] Step S4. Crush the composite powder prepared in Step S3 to D90 of 30 μm. Then, stir the crushed composite powder and add a 10% mass fraction hydrochloric acid solution and stir for 3 h to form a suspension. The mass ratio of the hydrochloric acid solution to the composite powder is 3:1. Then, perform solid-liquid phase separation on the above suspension, wash the solid phase with deionized water, and then repeat the above solid-liquid phase separation and deionized water washing process 4 times. Finally, add deionized water to the washed solid phase to prepare a suspension;

[0064] Step S5. Add samarium nitrate to the suspension prepared in Step S4, then add glycine and stir. The addition amount of glycine is 5% of the mass of samarium in samarium nitrate. Then, add ammonium oxalate solution and continue to stir for 3 h. The molar ratio of ammonium oxalate to samarium is 3:1. Finally, microwave-dry the above suspension, control the drying rate of microwave drying to be 91%, to obtain a composite solidified product;

[0065] Step S6. Mix alumina and the composite solidified product prepared in Step S5. The specific surface area of alumina is 200 m 2 / g, and the loose bulk density is 0.5 g / mL, and add deionized water to form a slurry. Ball-mill the slurry to obtain a slurry, and control D90 of the ball-milling of the slurry to be 20 μm;

[0066] Step S7. Coat the slurry on a straight-through honeycomb monolithic carrier. After coating, calcine the monolithic carrier at 400 °C for 1 h, and then raise the temperature to 600 °C and calcine for 1 h to obtain a reinforced hydrocarbon conversion catalyst.

[0067] Comparative Example 1

[0068] An enhanced hydrocarbon conversion catalyst, comprising a straight-through honeycomb metal carrier and a catalyst coating provided on the carrier. The carrier has a specification of Ф52×112mm, a pore density of 300 cpsi, and an inner core volume of 0.2L. The catalyst coating includes alumina and a cerium-zirconium composite oxide, and the mass ratio of alumina to the cerium-zirconium composite oxide is 1:1; in the cerium-zirconium composite oxide, the mass ratio of CeO2 to ZrO2 is 6:11, the coating amount of the catalyst coating is 100g / L, and the loading amount of noble metal Pt is 14.2g / ft 3 , and the loading amount of noble metal Pd is 14.2g / ft 3 .

[0069] The preparation method of the enhanced hydrocarbon conversion catalyst of this comparative example includes the following steps:

[0070] (1) Dissolve cerium nitrate and zirconium nitrate completely in deionized water to form a mixed solution. Place the mixed solution in a microwave dryer for microwave drying, take it out when the drying rate is controlled at 94%, and then place it in a temperature-controlled muffle furnace and calcine at 400°C for 4h to obtain cerium-zirconium composite oxide powder;

[0071] (2) Mix alumina and the cerium-zirconium composite oxide powder prepared in step (1) according to the coating mass ratio of 1:1. The specific surface area of the above alumina is 100m2 / g, and the loose bulk density is 1.0g / mL. Then add deionized water to form a slurry, and ball-mill the slurry to control D90 at 10um;

[0072] (3) Add platinum nitrate and palladium nitrate solutions to the slurry prepared in step (2), stir evenly, then coat the slurry on the straight-through honeycomb metal carrier. After the coating is completed, place the monolithic carrier in a temperature-controlled muffle furnace, calcine at 300°C for 2h, and then raise the temperature to 500°C and calcine for 2h to obtain the hydrocarbon conversion catalyst.

[0073] Comparative Example 2

[0074] An enhanced hydrocarbon conversion catalyst, comprising a straight-through honeycomb metal carrier and a catalyst coating provided on the carrier. The carrier has a specification of Ф52×112mm, a pore density of 300 cpsi, and an inner core volume of 0.2L. The catalyst coating includes alumina and a cerium-zirconium composite oxide, and the mass ratio of alumina to the cerium-zirconium composite oxide is 1:1; in the cerium-zirconium composite oxide, the mass ratio of CeO2 to ZrO2 is 5:4, the coating amount of the catalyst coating is 100g / L, and the loading amount of noble metal Pt is 28.3g / ft 3 , and the loading amount of noble metal Pd is 28.3g / ft 3 .

[0075] The preparation method of the enhanced hydrocarbon conversion catalyst of this comparative example includes the following steps:

[0076] (1) Completely dissolve cerium nitrate and zirconium nitrate in deionized water to form a mixed solution. Place the mixed solution in a microwave dryer for microwave drying. Take it out when the drying rate is controlled at 93%, and then place it in a temperature-controlled muffle furnace and calcine at 400 °C for 4 h to obtain cerium-zirconium composite oxide powder;

[0077] (2) Mix alumina and the cerium-zirconium composite oxide powder prepared in step (1) according to a coating mass ratio of 1:1. The specific surface area of the above alumina is 100 m 2 / g, and the loose bulk density is 1.0 g / mL. Then add deionized water to form a slurry, and ball-mill the slurry to control D90 at 10 um;

[0078] (3) Add platinum nitrate and palladium nitrate solutions to the slurry prepared in step (2), stir evenly, then coat the slurry on a straight-through honeycomb metal carrier. After the coating is completed, place the monolithic carrier in a temperature-controlled muffle furnace, calcine at 300 °C for 2 h, and then raise the temperature to 500 °C and calcine for 2 h to obtain a hydrocarbon conversion catalyst.

[0079] Comparative Example 3

[0080] An enhanced hydrocarbon conversion catalyst includes a straight-through honeycomb metal carrier and a catalyst coating provided on the carrier. The carrier specifications are Ф52×112 mm, the pore density is 300 cpsi, and the inner core volume is 0.2 L. The catalyst coating includes alumina and cerium-zirconium composite oxide, and the mass ratio of alumina to cerium-zirconium composite oxide is 1:10; the mass ratio of CeO2 to ZrO2 in the cerium-zirconium composite oxide is 6:11. The coating amount of the catalyst coating is 100 g / L, and the loading amount of precious metal Pt is 25.7 g / ft 3 , and the loading amount of precious metal Pd is 25.7 g / ft 3 .

[0081] The preparation method of the enhanced hydrocarbon conversion catalyst of this comparative example includes the following steps:

[0082] (1) Completely dissolve cerium nitrate and zirconium nitrate in deionized water to form a mixed solution. Place the mixed solution in a microwave dryer for microwave drying. Take it out when the drying rate is controlled at 92%, and then place it in a temperature-controlled muffle furnace and calcine at 450 °C for 2 h to obtain cerium-zirconium composite oxide powder;

[0083] (2) Mix alumina and the cerium-zirconium composite oxide powder prepared in step (1) according to a coating mass ratio of 1:10. The specific surface area of the above alumina is 200 m 2 / g, and the loose bulk density is 0.5 g / mL. Then add deionized water to form a slurry, and ball-mill the slurry to control D90 at 20 um;

[0084] (3) Add the platinum nitrate and palladium nitrate solutions to the slurry prepared in step (2), stir evenly, then coat the slurry on a straight-through honeycomb metal support. After the coating is completed, place the monolithic support in a temperature-controlled muffle furnace and calcine it at 400 °C for 1 h, then raise the temperature to 600 °C and calcine for 1 h to obtain a hydrocarbon conversion catalyst.

[0085] Comparative Example 4

[0086] An enhanced hydrocarbon conversion catalyst, comprising a straight-through honeycomb metal support and a catalyst coating provided on the support. The support has a specification of Ф52×112 mm, a pore density of 300 cpsi, and an inner core volume of 0.2 L. The catalyst coating comprises alumina and a cerium-zirconium composite oxide, and the mass ratio of alumina to the cerium-zirconium composite oxide is 1:10; the mass ratio of CeO2 to ZrO2 in the cerium-zirconium composite oxide is 5:4, the coating amount of the catalyst coating is 100 g / L, and the loading amount of noble metal Pt is 51.5 g / ft 3 and the loading amount of noble metal Pd is 51.5 g / ft 3 .

[0087] The preparation method of the enhanced hydrocarbon conversion catalyst of this comparative example comprises the following steps:

[0088] (1) Completely dissolve cerium nitrate and zirconium nitrate in deionized water to form a mixed solution. Place the mixed solution in a microwave dryer, perform microwave drying, take it out when the drying rate is controlled at 93%, and then place it in a temperature-controlled muffle furnace and calcine it at 450 °C for 2 h to obtain a cerium-zirconium composite oxide powder.

[0089] (2) Mix alumina and the cerium-zirconium composite oxide powder prepared in step (1) according to a coating mass ratio of 1:10. The specific surface area of the above alumina is 200 m 2 / g, and the loose bulk density is 0.5 g / mL. Subsequently, add deionized water to form a slurry, and ball-mill the slurry to control D90 at 20 um;

[0090] (3) Add the platinum nitrate and palladium nitrate solutions to the slurry prepared in step (2), stir evenly, then coat the slurry on a straight-through honeycomb metal support. After the coating is completed, place the monolithic support in a temperature-controlled muffle furnace, calcine it at 400 °C for 1 h, and then raise the temperature to 600 °C and calcine for 1 h to complete the preparation of the hydrocarbon conversion catalyst coating.

[0091] Comparative Example 5

[0092] An enhanced hydrocarbon conversion catalyst, comprising a through-flow honeycomb metal carrier and a catalyst coating disposed on the carrier. The carrier has a specification of Ф52×112mm, a pore density of 300 cpsi, and an inner core volume of 0.2L. The catalyst coating includes alumina and an active component, and the mass ratio of alumina to the active component is 1:10. The active component is a Pt-Pd-Nb2O5-MoO3-Sm2O3-CeO2-ZrO2 composite solidified product. By mass percentage, the Pt-Pd-Nb2O5-MoO3-Sm2O3-CeO2-ZrO2 composite solidified product includes 2% Pt, 2% Pd, 10% Nb2O5, 8% MoO3, 6% Sm2O3, 40% CeO2, and 32% ZrO2. The coating amount of the catalyst coating is 100g / L, and the loading amount of the noble metal Pt is 51.5g / ft 3 , and the loading amount of the noble metal Pd is 51.5g / ft 3 .

[0093] The preparation method of the enhanced hydrocarbon conversion catalyst of this comparative example includes the following steps:

[0094] (1) Take platinum nitrate, palladium nitrate, ammonium molybdate, ammonium niobium oxalate, samarium nitrate, cerium nitrate, and zirconium nitrate and mix them with deionized water to obtain a mixed solution, and control the composition of each component of the above mixed solution to be equal to the composition ratio of the composite solidified product;

[0095] (2) Place the mixed solution prepared in step (1) in a microwave dryer for microwave drying, take it out when the drying rate reaches 93%, and then place it in a temperature-controlled muffle furnace and calcine it at 450°C for 2h to obtain a composite powder;

[0096] (3) Mix alumina and the composite powder prepared in step (2) according to a coating mass ratio of 1:10. The specific surface area of the above alumina is 200m 2 / g, and the loose bulk density is 0.5g / mL. Then add deionized water to form a slurry, and ball-mill the slurry to control D90 at 20um to obtain a coating slurry;

[0097] (4) Coat the slurry on the through-flow honeycomb metal carrier. After coating, place the monolithic carrier in a temperature-controlled muffle furnace, calcine it at 400°C for 1h, and then raise the temperature to 600°C and calcine it for 1h to complete the preparation of the hydrocarbon conversion catalyst coating.

[0098] Comparative Example 6

[0099] An enhanced hydrocarbon conversion catalyst, comprising a through-flow honeycomb metal carrier and a catalyst coating disposed on the carrier. The carrier has a specification of Ф52×112mm, a pore density of 300 cpsi, and an inner core volume of 0.2L. The catalyst coating includes alumina and an active component, and the mass ratio of alumina to the active component is 1:10. The active component is a Pt-Pd-Nb2O5-MoO3-Sm2O3-CeO2-ZrO2 composite solidified product. By mass percentage, the Pt-Pd-Nb2O5-MoO3-Sm2O3-CeO2-ZrO2 composite solidified product includes 2% Pt, 2% Pd, 10% Nb2O5, 8% MoO3, 6% Sm2O3, 40% CeO2, and 32% ZrO2. The coating amount of the catalyst coating is 100 g / L, and the loading amount of the noble metal Pt is 51.5 g / ft 3 , and the loading amount of the noble metal Pd is 51.5 g / ft 3 .

[0100] The preparation method of the enhanced hydrocarbon conversion catalyst of this comparative example includes the following steps:

[0101] Step S1. Mix platinum nitrate, palladium nitrate, ammonium molybdate, ammonium niobium oxalate, and deionized water to obtain a Pt-Pd-Mo-Nb mixed solution. Then, successively add ethylenediamine to the Pt-Pd-Mo-Nb mixed solution. The addition amount of ethylenediamine is 10% of the total amount of the simple substances in the Pt-Pd-Mo-Nb mixed solution. Subsequently, add ammonia water to adjust the pH of the mixed solution to 10. Then, heat the Pt-Pd-Mo-Nb mixed solution at 60°C for 3 h with stirring to obtain a Pt-Pd-Mo-Nb sol compound solution;

[0102] Step S2. Completely dissolve cerium nitrate and zirconium nitrate in deionized water, and then add it to the Pt-Pd-Mo-Nb sol compound solution obtained in Step S1 to obtain a mixed solution;

[0103] Step S3. Microwave-dry the mixed solution prepared in Step S2, control the drying rate of the microwave drying to be 93%, and then calcine it at 450°C for 2 h to obtain a composite powder. The composite powder is formulated into a suspension with deionized water;

[0104] Step S4. Add samarium nitrate to the suspension prepared in Step S3, then add glycine and stir. The addition amount of glycine is 5% of the mass of samarium in samarium nitrate. Then, add ammonium oxalate solution and continue to stir for 3 h. The molar ratio of ammonium oxalate to samarium is 3:1. Then, add 10% of the mass of the above suspension of polystyrene (microspherical, diameter 1-2um), stir for 2 h, and then microwave-dry the above suspension, control the drying rate of the microwave drying to be 91% to obtain a composite solidified product;

[0105] Step S5. Mix alumina and the composite solidified product obtained in Step S4 at a mass ratio of 1:10. The specific surface area of the alumina is 200 m 2 / g, and the loose bulk density is 0.5 g / mL. Then add deionized water to form a slurry, and ball-mill the slurry to obtain a slurry, controlling the D90 of the slurry ball-milling to be 20 um;

[0106] Step S6. Coat the slurry on a straight-through honeycomb monolithic carrier. After the coating is completed, calcine the monolithic carrier at 400 °C for 1 h, and then raise the temperature to 600 °C and calcine for 1 h to obtain a reinforced hydrocarbon conversion catalyst.

[0107] Comparative Example 7

[0108] A reinforced hydrocarbon conversion catalyst, comprising a straight-through honeycomb metal carrier and a catalyst coating provided on the carrier. The carrier specifications are Ф52×112 mm, the pore density is 300 cpsi, and the inner core volume is 0.2 L. The catalyst coating includes alumina and an active component, and the mass ratio of alumina to the active component is 1:10; the active component is a Pt-Pd-Nb2O5-MoO3-Sm2O3-CeO2-ZrO2 composite solidified product; by mass percentage, the Pt-Pd-Nb2O5-MoO3-Sm2O3-CeO2-ZrO2 composite solidified product includes 2% Pt, 2% Pd, 10% Nb2O5, 8% MoO3, 6% Sm2O3, 40% CeO2, and 32% ZrO2. The coating amount of the catalyst coating is 100 g / L, and the loading amount of the noble metal Pt is 51.5 g / ft 3 , and the loading amount of the noble metal Pd is 51.5 g / ft 3 .

[0109] The preparation method of the reinforced hydrocarbon conversion catalyst of this comparative example includes the following steps:

[0110] Step S1. Mix platinum nitrate, palladium nitrate, ammonium molybdate, ammonium niobium oxalate, and deionized water to obtain a Pt-Pd-Mo-Nb mixed solution. Then, successively add ethylenediamine to the Pt-Pd-Mo-Nb mixed solution. The addition amount of ethylenediamine is 10% of the total amount of the single substances in the Pt-Pd-Mo-Nb mixed solution. Subsequently, add ammonia water to adjust the pH of the mixed solution to 10. Then, heat and stir the Pt-Pd-Mo-Nb mixed solution at 60 °C for 3 h to obtain a Pt-Pd-Mo-Nb sol compound solution;

[0111] Step S2. Completely dissolve cerium nitrate and zirconium nitrate in deionized water, and then add them to the Pt-Pd-Mo-Nb sol compound solution obtained in Step S1 to obtain a mixed solution;

[0112] Step S3. Microwave-dry the mixture obtained in Step S2, control the drying rate of microwave drying to be 93%, and then calcine it at 450 °C for 2 h to obtain a composite powder. The composite powder is formulated into a suspension with deionized water;

[0113] Step S4. Add samarium nitrate to the suspension obtained in Step S3, then add glycine and stir. The addition amount of glycine is 5% of the mass of samarium in samarium nitrate. Then add ammonium oxalate solution and continue to stir for 3 h. The molar ratio of ammonium oxalate to samarium is 3:1. After stirring for 2 h, microwave-dry the above suspension, control the drying rate of microwave drying to be 91%, and obtain a composite solidified product;

[0114] Step S5. Mix alumina and the composite solidified product obtained in Step S4 at a mass ratio of 1:10. The specific surface area of alumina is 200 m 2 / g, and the loose bulk density is 0.5 g / mL. Add deionized water to form a slurry, and ball-mill the slurry to obtain a slurry, control the D90 of the slurry ball-milling to be 20 um;

[0115] Step S6. Coat the slurry on a through-flow honeycomb monolithic carrier. After coating, calcine the monolithic carrier at 400 °C for 1 h, and then raise the temperature to 600 °C and calcine for 1 h to obtain a reinforced hydrocarbon conversion catalyst.

[0116] Light-off temperature comparison test:

[0117] Install the catalysts prepared in Examples 1-4 and Comparative Examples 1-7 on the gasoline engine test bench respectively, and conduct the fresh-state HC light-off temperature test based on the standard requirements of HJ / T 331-2006 "Technical Requirements for Environmental Protection Products - Gasoline Vehicle Catalytic Converters", and the space velocity is set to 150 k h -1 . Then place the above catalysts of the same scheme in an aging furnace, age them at 850 °C and 15% H2O for 50 h to obtain aged catalysts. After aging, conduct the aged-state HC light-off temperature test of the catalysts of each scheme according to the above method. The light-off temperature test of each scheme is carried out 3 times, and the average value is taken as the final result. The comparison of the light-off temperature (T50) is shown in Table 1 (Note: The lower the T50, the better the HC conversion rate of the catalyst).

[0118] Table 1 Comparison table of HC light-off T50

[0119]

[0120] As can be seen from Table 1, under the same precious metal conditions, the light-off temperatures of fresh and aged HC in the examples provided by the present invention are lower than those of the corresponding comparative examples, indicating that the Pt-Pd-Nb2O5-MoO3-Sm2O3-CeO2-ZrO2 composite solidifying agent provided by the present invention has a better enhancing effect on HC light-off compared to the conventional CeO2, ZrO2, and Al2O3 components; at the same time, from the test results of Example 4 and Comparative Examples 5 to 7, it can be seen that the addition methods of the Nb2O5, MoO3, Sm2O3, CeO2, and ZrO2 components and the selective dissolution of ZnO to construct a microporous system have a significant impact on the overall HC catalytic activity of the coating.

[0121] Motorcycle vehicle emission comparison test:

[0122] The catalysts of Examples 1 to 4 and Comparative Examples 1 to 7 (including fresh and aged states) that have completed the light-off temperature comparison test were respectively encapsulated into an exhaust pipe structure and installed in the exhaust system of a 250CC displacement Euro V standard motorcycle. The distance between the catalyst inlet and the engine outlet was approximately 30 cm. Subsequently, each catalyst scheme was respectively subjected to an exhaust pollutant emission test (WMTC test) after cold start at room temperature in accordance with the requirements of Euro V regulations, and the fresh and aged THC and NMHC pollutant emissions of each scheme were compared. Each scheme was tested 3 times, and the average value was taken as the final result. The comparison results of HC pollutant emissions in the WMTC test are shown in Table 2 (Note: The lower the emission value, the better the HC conversion rate of the catalyst).

[0123] Table 2 Comparison of typical gaseous pollutant emissions in the WMTC test

[0124]

[0125] As can be seen from Table 2, the variation trends of the motorcycle vehicle emission comparison test results and the light-off temperature comparison test results are consistent. Under the same precious metal conditions, the fresh and aged THC and NMHC emission results of the examples provided by the present invention are lower than those of the corresponding comparative examples; at the same time, the HC emission results of the examples provided by the present invention are all within the Euro V regulation limits. The aged NMHC emissions of Comparative Example 1 and Comparative Example 3 exceed the regulation limits, and the NMHC emissions of Comparative Example 2 are only less than 3% different from the limits; the method provided by the present invention can meet the Euro V regulation requirements for vehicle emissions without increasing precious metals, and the HC conversion in the case of high precious metals is more excellent than the conventional scheme, thereby effectively reducing HC pollution.

[0126] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention rather than to limit them. Although the present invention has been described in detail with reference to the examples, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered within the scope of the claims of the present invention.

Claims

1. An enhanced hydrocarbon conversion catalyst, characterized in that, It includes a carrier and a catalyst coating disposed on the carrier. The catalyst coating includes alumina and an active component, and the mass ratio of alumina to the active component is 1:1 to 10.

2. The enhanced hydrocarbon conversion catalyst according to claim 1, wherein The active component is a Pt-Pd-Nb2O5-MoO3-Sm2O3-CeO2-ZrO2 composite solidified product.

3. The enhanced hydrocarbon conversion catalyst according to claim 2, wherein By mass percentage, the Pt-Pd-Nb2O5-MoO3-Sm2O3-CeO2-ZrO2 composite solidification product comprises 1-2% Pt, 1-2% Pd, 5-10% Nb2O5, 5-8% MoO3, 3-6% Sm2O3, 30-40% CeO2 and 32-55% ZrO 2。 4. The preparation method of the hydrocarbon conversion enhancing catalyst according to any one of claims 1-3, characterized in that, It includes the following steps: Step S1. Mix platinum nitrate, palladium nitrate, ammonium molybdate, ammonium niobium oxalate and deionized water to obtain a Pt-Pd-Mo-Nb mixed solution. Then, add ethylenediamine to the Pt-Pd-Mo-Nb mixed solution in sequence, and then add ammonia water to adjust the pH of the mixed solution to 8-10. Then, heat and stir the Pt-Pd-Mo-Nb mixed solution to obtain a Pt-Pd-Mo-Nb sol compound solution. Step S2. Completely dissolve cerium nitrate and zirconium nitrate in deionized water, and then add it to the Pt-Pd-Mo-Nb sol compound solution obtained in Step S1 to obtain a composite solution. Then, add zinc acetate to the composite solution and stir, and then heat to obtain a mixed solution. Step S3. Dry the mixed solution prepared in Step S2, and then calcine it to obtain a composite powder. Step S4. Crush the composite powder prepared in Step S3, then add a hydrochloric acid solution to the crushed composite powder and stir to form a suspension. Then, perform solid-liquid phase separation on the above suspension, wash it, and finally add deionized water to the washed solid phase to prepare a suspension. Step S5. Add samarium nitrate to the suspension prepared in Step S4, then add glycine and stir, then add an ammonium oxalate solution and continue to stir for at least 2 h. Finally, dry the above suspension to obtain a composite solidified product. Step S6. Mix alumina and the composite solidified product prepared in Step S5, and add deionized water to form a slurry. Ball-mill the slurry to obtain a coating slurry. Step S7. Coat the coating slurry on a monolithic carrier. After coating, calcine the monolithic carrier to obtain a reinforced hydrocarbon conversion catalyst.

5. The preparation method of the enhanced hydrocarbon conversion catalyst according to claim 4, characterized in that, In Step S1, the addition amount of ethylenediamine is 5-10% of the total amount of the Pt-Pd-Mo-Nb mixed solution in terms of single substances, the heating temperature is 50-60 °C, and the heating time is 3-4 h.

6. The preparation method of the enhanced hydrocarbon conversion catalyst according to claim 4, characterized in that, In Step S2, the addition amount of zinc acetate is 5-10% of the mass of the solidified product of the composite solution, the stirring time is 2-4 h, the heating temperature is 70-80 °C, and the heating time is 4-6 h.

7. The preparation method of the enhanced hydrocarbon conversion catalyst according to claim 4, characterized in that, In Steps S3 and S5, the drying method is microwave drying, and the drying rate of microwave drying is controlled to be >90%; the calcination temperature in Step S3 is 400-450 °C, and the calcination time is 2-4 h.

8. The preparation method of the enhanced hydrocarbon conversion catalyst according to claim 4, characterized in that, In Step S4, the mass fraction of hydrochloric acid in the hydrochloric acid solution is 5-10%, the mass ratio of the hydrochloric acid solution to the composite powder is 2-3:1, the stirring time is 2-3 h, and the number of washing times is ≥3 times.

9. The preparation method of the enhanced hydrocarbon conversion catalyst according to claim 4, characterized in that, In step S5, the addition amount of glycine is 3-5% of the mass of samarium in samarium nitrate, and the molar ratio of ammonium oxalate to samarium is 2-3:1; in step S6, the specific surface area of alumina is 100-200 m 2 / g, the loose bulk density is 0.5-1.0 g / mL, and the D90 of the coating slurry is 10-20 um.

10. The preparation method of the enhanced hydrocarbon conversion catalyst according to claim 4, wherein, In Step S7, the calcination is specifically: calcine at 300-400 °C for 1-2 h, and then raise the temperature to 500-600 °C and calcine for 1-2 h.

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