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Volume 117
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Pore-to-reactor CFD-DEM modeling: How intraparticle diffusion limitation affects crotonaldehyde selectivity over Zr-BEA zeolite
Zhongfeng Geng a b c, Zhenhan Wang a b c, Yu Zhang a b c, He Dong a b c *
a Key Laboratory for Green Chemical Technology of Ministry of Education, R&D Center for Petrochemical Technology, Tianjin University, Tianjin, 300072, China
b Zhejiang Institute of Tianjin University, Ningbo, 315201, China
c State Key Laboratory of Engines, Tianjin University, Tianjin, 300072, China
10.1016/j.partic.2026.06.041
Volume 117, October 2026, Pages 235-248
Received 10 April 2026, Revised 24 June 2026, Accepted 29 June 2026, Available online 10 July 2026, Version of Record 6 August 2026.
E-mail: donghe@tju.edu.cn
Highlights

• Micron-scale model of Zr-BEA zeolite obtaining effective diffusion coefficients of each component.

• Intraparticle reaction-diffusion model analyzing the effect of particle shape and size.

• Correlation model of temperature, partial pressure and internal diffusion effectiveness factor.

• Apparent kinetic equations considering diffusion restriction.

• Effect of process conditions on reaction rate and selectivity.


Abstract

Heterogeneous aldol condensation of acetaldehyde to crotonaldehyde catalyzed by Zr-BEA zeolite holds significant industrial potential. However, the molecular diffusion is limited by the complex structure and various size of zeolite particles, leading to crotonaldehyde accumulation and over-condensation, which reduces process efficiency. Therefore, a thorough understanding of the intraparticle reaction-diffusion process is necessary for further industrial application. A micron-scale model of the zeolite particle was established using Discrete Element Method (DEM), and Computational Fluid Dynamics (CFD) simulations were conducted to obtain the effective diffusion coefficient of each component across a range of temperature. Integrating these coefficients with intrinsic kinetic equations, an intraparticle reaction-diffusion model was established to investigate the effect of particle shape and size on the process. A quantitative correlation was established among temperature, acetaldehyde partial pressure, and the internal diffusion effectiveness factor, yielding apparent kinetic equations that account for internal diffusion limitations. Based on the porous medium model, a fixed-bed reactor model was established to predict the distribution of velocity, temperature, and concentration under different process conditions. The results indicated that temperature had a more significant effect on product selectivity than the inlet flow rate or acetaldehyde partial pressure. As the temperature increased from 433.15 K to 493.15 K, the selectivity of crotonaldehyde first increased from 93.750% to 97.120% and then decreased to 82.180%, while the selectivity of over-condensation by-products increased from 0.370% to 17.730%.

Graphical abstract
Keywords
Aldol condensation; Crotonaldehyde; Zr-BEA zeolite; CFD; Reaction-diffusion
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