The Challenges and Comprehensive Evolution of Cu-Based Zeolite Catalysts for SCR Systems in Diesel Vehicles: A Review

Qi, Xiaojuan; Wang, Yanhua; Liu, Caixia; Liu, Qingling

doi:10.1007/s10563-022-09384-6

Cited by 5 publications

(1 citation statement)

References 95 publications

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“…To comply with current and future emission regulations, it is urgent and imperative to eliminate NO x emissions from diesel engines. Among the various NO x removal technologies, the selective catalytic reduction of NO x with ammonia (NH 3 -SCR) is regarded as the most efficient method [4,5], and copper (Cu)-exchanged SSZ-13 zeolites are now commercial products for NH 3 -SCR catalysts due to their outperformance in reducing diesel engine NO x emissions compared with traditional vanadia-based (V 2 O 5 -WO 3 /TiO 2 ) catalysts [6][7][8][9][10]. However, the SSZ-13 zeolite has a chabazite (CHA) structure with a relatively small pore radius of 3.8 Å in an eight-membered ring, which may limit the mass transfer of reactants in channels [11,12].…”

Section: Introductionmentioning

confidence: 99%

Hard Template-Assisted Trans-Crystallization Synthesis of Hierarchically Porous Cu-SSZ-13 with Enhanced NH3-SCR Performance

et al. 2023

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Small porous Cu-SSZ-13 catalysts have recently been commercialized for the selective catalytic reduction of NOx with ammonia (NH3-SCR) on diesel vehicles. Unfortunately, the conventional Cu-SSZ-13 catalyst still confronts the challenge of diffusion limitations, which represent a major obstacle that reduces the catalyst’s SCR performance. Herein, a hierarchically porous SSZ-13 zeolite was synthesized via a trans-crystallization method assisted by the use of carbon black as a hard template in a short synthetic period, and the corresponding Cu-SSZ-13 catalysts with mesopores exhibited improved low-temperature activity and hydrothermal stability when compared with their microporous counterpart. A series of characterizations revealed that the mesopores are conducive to an increase in Cu loading while helping to stabilize the CHA structure and maintain the Cu species in their ionic form. More importantly, intra-particle diffusion limitations are reduced via the introduction of the mesopores owing to the shortened diffusion path inside the SSZ-13 zeolite, thus not only enhancing the active sites’ accessibility but also promoting the diffusion of the reactants and products. This work contributes to the design and synthesis of a high-performance Cu-SSZ-13 zeolite SCR catalyst for the removal of NOx emitted from diesel vehicles.

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Section: Introductionmentioning

confidence: 99%

Hard Template-Assisted Trans-Crystallization Synthesis of Hierarchically Porous Cu-SSZ-13 with Enhanced NH3-SCR Performance

et al. 2023

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Study on transient temperature characteristics of SCR under different post-injection strategies

Nie,

Bi,

Shen

et al. 2024

Fuel

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Elucidating the Impact of Cis–Trans Organic Structure Directing Agent Isomer Ratios on the Aluminum Distribution Within SSZ-39

Umhey,

Guo,

Cui

et al. 2024

Chem. Mater.

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Despite their widespread use, the mechanisms governing the synthesis of zeolite catalysts are still poorly understood. A notable example of this problem is the uncertainty surrounding the influence of synthesis conditions on the placement of Al atoms in the zeolite framework, which determines the active sites available for catalytic species. In this work, the role of the cis to trans isomer ratio of the OSDA N,N-dimethyl-3-5-dimethylpiperidinium on the energetics of 26 distinct Al pair distributions in SSZ-39 is examined both in the presence and absence of Na using density functional theory calculations. The initial orientation of the OSDA was found to have a significant impact on the final energies present, necessitating the screening of a large number of initial orientations with force field calculations and single point DFT calculations. Ground state energies were found to vary significantly with the ratio of cis to trans OSDAs with a Boltzmann distribution revealing the most likely Al pair distributions shift from sharing the same 8 membered rings to sharing the same double 6-membered rings to having no shared subunits as one increases the amount of cis OSDA present within the framework. The presence of Na was found to favor Al pair distributions where both Als occupied the same 6-membered ring. When an implicit solvent model was used to evaluate ground state energies the ideal Na sites shifted from 6membered rings to empty SSZ-39 cages while OSDA positions and orientations remained largely the same. To provide insight on how kinetic factors may influence Al distributions, formation energies we calculated for connected double 6-membered rings. These formation energies revealed a preference for Al pairs to occupy the same 4-membered ring, which indicates kinetic and thermodynamic control may lead to different Al distributions in SSZ-39.

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The Challenges and Comprehensive Evolution of Cu-Based Zeolite Catalysts for SCR Systems in Diesel Vehicles: A Review

Cited by 5 publications

References 95 publications

Hard Template-Assisted Trans-Crystallization Synthesis of Hierarchically Porous Cu-SSZ-13 with Enhanced NH3-SCR Performance

Hard Template-Assisted Trans-Crystallization Synthesis of Hierarchically Porous Cu-SSZ-13 with Enhanced NH3-SCR Performance

Study on transient temperature characteristics of SCR under different post-injection strategies

Elucidating the Impact of Cis–Trans Organic Structure Directing Agent Isomer Ratios on the Aluminum Distribution Within SSZ-39

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