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CN-121988277-A - Pd/Mn/SSZ-13 molecular sieve NOxAdsorption material and preparation method and application thereof

CN121988277ACN 121988277 ACN121988277 ACN 121988277ACN-121988277-A

Abstract

The invention discloses a Pd/Mn/SSZ-13 molecular sieve NO x adsorption material, a preparation method and application thereof, and belongs to the technical field of motor vehicle tail gas treatment. The method adopts a co-impregnation and/or stepwise impregnation method to introduce Mn species into the Pd/SSZ-13 material, and controls the loading amount of Mn element to prepare the Pd/Mn/SSZ-13 molecular sieve NO x adsorption material. The mass of Mn element and Pd element is (0.8-1.2): 1. The invention is based on the competitive ion exchange and electron modulation dual mechanism of Mn ions, promotes the formation of hydroxylation [ Pd (OH) ] + -Z species by occupying the adjacent aluminum sites in the molecular sieve framework preferentially, realizes the directional regulation and control of Pd species morphology, and simultaneously generates strong electron interaction with the PdO x species to inhibit the weak adsorption of NO. The synergistic effect of the two obviously improves the initial desorption temperature of the NO x adsorbing material, optimizes the storage-release window of NO x , and ensures that the NO x release temperature window of the NO x is matched with the high-activity temperature interval of the downstream SCR catalyst in a high-efficiency manner.

Inventors

  • PENG HONGGEN
  • LI GUOBO
  • LI HAO
  • HUA ZHEN

Assignees

  • 南昌大学

Dates

Publication Date
20260508
Application Date
20251231

Claims (10)

  1. 1. The Pd/Mn/SSZ-13 molecular sieve NO x adsorbing material is characterized in that the preparation method comprises the following steps: Performing competitive ion exchange on the NH 4 /SSZ-13 molecular sieve, the first metal salt solution and the second metal salt solution, removing water, and calcining to obtain the Pd/Mn/SSZ-13 molecular sieve NO x adsorption material; And/or, performing first ion exchange on the NH 4 /SSZ-13 molecular sieve and the first metal salt, removing water, calcining to obtain a Mn/SSZ-13 molecular sieve or a Pd/SSZ-13 molecular sieve, performing second ion exchange on the Mn/SSZ-13 molecular sieve and the second metal salt solution, removing water, and calcining to obtain the Pd/Mn/SSZ-13 molecular sieve NO x adsorbing material; the first metal salt and the second metal salt are respectively and independently manganese salt or palladium salt, and the first metal salt and the second metal salt are different; The mass ratio of Mn element in the manganese salt to Pd element in the palladium salt is (0.8-1.2): 1.
  2. 2. The NO x adsorbent according to claim 1, wherein the mass ratio of Mn element in the manganese salt to Pd element in the palladium salt is (0.9 to 1.1): 1.
  3. 3. The NO x adsorbent material according to claim 1, wherein the method of preparation comprises the steps of: Performing competitive ion exchange on the NH 4 /SSZ-13 molecular sieve, the manganese salt solution and the palladium salt solution, removing water, and calcining to obtain the Pd/Mn/SSZ-13 molecular sieve NO x adsorption material.
  4. 4. The NO x adsorbent material according to claim 1, wherein the Mn element accounts for 0.8 to 1.2wt% of the total mass of the Pd/Mn/SSZ-13 molecular sieve NO x adsorbent material.
  5. 5. The NO x adsorbent material of claim 1, wherein the NH 4 /SSZ-13 molecular sieve is prepared by ion exchange of Na/SSZ-13 with an ammonium salt.
  6. 6. The NO x adsorbent according to claim 1, wherein the competitive ion exchange or first ion exchange or second ion exchange time is 0.5 to 2 hours.
  7. 7. The NO x adsorbent material according to claim 1, wherein the calcination temperature is 500-600 ℃.
  8. 8. The use of the Pd/Mn/SSZ-13 molecular sieve NO x adsorbent according to any one of claims 1 to 7 to increase the initial desorption temperature of NO x .
  9. 9. The application of the Pd/Mn/SSZ-13 molecular sieve NO x adsorbing material according to any one of claims 1-7 in purifying motor vehicle exhaust, wherein the Pd/Mn/SSZ-13 molecular sieve NO x adsorbing material adsorbs NO x in the exhaust.
  10. 10. The use according to claim 9, wherein the initial desorption temperature of NO x in the temperature programmed desorption test of the Pd/Mn/SSZ-13 molecular sieve NO x is not less than 210 ℃.

Description

Pd/Mn/SSZ-13 molecular sieve NO x adsorption material, preparation method and application thereof Technical Field The invention relates to the technical field of motor vehicle tail gas aftertreatment, in particular to a Pd/Mn/SSZ-13 molecular sieve NO x adsorption material, a preparation method and application thereof. Background In the cold start and low speed operation phases of diesel vehicles, the exhaust temperature is usually lower than 200 ℃, and at this time, the traditional ammonia selective catalytic reduction (NH 3 -SCR) system cannot operate effectively due to insufficient catalyst activity, so that the NO x emission amount in the phase can account for more than 30% of the total emission. Passive NO x adsorption (PNA) materials are one of the effective strategies to solve this problem, and the core is to trap NO x at low temperature with the adsorption material and temporarily store it, and then controllably release NO x and catalytically reduce it when the exhaust temperature rises to the downstream SCR catalyst activity window (typically 200-500 ℃). Among the numerous PNA materials, palladium (Pd) -supported SSZ-13 molecular sieves are of great interest due to their high NO x adsorption capacity and good hydrothermal stability. However, the existing research shows that the desorption temperature window of NO x adsorbed on the Pd/SSZ-13 material is low overall, and a considerable part of the desorption temperature window is desorbed before 200 ℃, so that the desorption temperature window is difficult to effectively cooperate with a downstream SCR system, and the improvement of the overall denitration efficiency is limited. Studies in the prior art have shown that Pd species in Pd/SSZ-13 exist in a variety of forms (e.g., pd 2+-2Z、[Pd(OH)]+ -Z and PdO x clusters, Z representing a negatively charged site in the molecular sieve framework), and these Pd species differ in terms of adsorption strength and desorption temperature for NO. Wherein, the NO adsorption on [ Pd (OH) ] + -Z species is strongest, and the desorption temperature is highest. Therefore, how to promote the formation of such stable Pd species through modification and inhibit the low-temperature unstable adsorption of PdO x has important significance for integrally improving the desorption temperature of NO x of the material. Disclosure of Invention In order to solve the problems that the Pd/SSZ-13 passive NO x adsorption material in the prior art has low initial desorption temperature and is not matched with the SCR catalyst activity window, the primary purpose of the invention is to provide a Pd/Mn/SSZ-13 molecular sieve NO x adsorption material. The invention also aims to provide the application of the Pd/Mn/SSZ-13 molecular sieve NO x adsorbing material in purifying the tail gas of a diesel vehicle. In order to achieve the above object, the present invention provides the following technical solutions: the preparation method of the Pd/Mn/SSZ-13 molecular sieve NO x adsorption material comprises the following steps: Performing competitive ion exchange on the NH 4/SSZ-13 molecular sieve, the first metal salt solution and the second metal solution, removing water, and calcining to obtain the Pd/Mn/SSZ-13 molecular sieve NO x adsorption material; And/or, performing first ion exchange on the NH 4/SSZ-13 molecular sieve and a first metal salt solution, removing water, then calcining to obtain a Mn/SSZ-13 molecular sieve or a Pd/SSZ-13 molecular sieve, performing second ion exchange on the Mn/SSZ-13 molecular sieve and a second metal salt solution, removing water, and then calcining to obtain the Pd/Mn/SSZ-13 molecular sieve NO x adsorbing material; the first metal salt and the second metal salt are respectively and independently manganese salt or palladium salt, and the first metal salt and the second metal salt are different; The mass ratio of Mn element in the manganese salt to Pd element in the palladium salt is (0.8-1.2): 1. The method adopts a co-impregnation method and/or a stepwise impregnation method to introduce Mn species into the Pd/SSZ-13 material, and controls the loading amount of Mn element to prepare the Pd/Mn/SSZ-13 molecular sieve NO x adsorption material. Mn species improves the initial desorption temperature of the composite material to NO x compared with Pd/SSZ-13 material by changing the structural form of Pd in the SSZ-13 molecular sieve, optimizes the storage-release window of NO x, ensures that the release temperature window of NO x is highly overlapped with the catalytic activity temperature window (200-500 ℃) of the SCR catalyst, solves the key technical bottleneck of the synergistic treatment of PNA material and the SCR catalyst on motor vehicle tail gas, and reduces the emission of NO x of the motor vehicle in the cold start stage. A preferred embodiment of the invention is the introduction of Mn species by competitive ion exchange. The introduced Mn species occupy part of the aluminum sites (especially orth