Comparative Investigation of Structure and Operating Parameters on the Performance and Reaction Dynamic of CO Conversion on Silica Aerogel and Fumed-Silica-Supported Pd Catalysts

Authors

Rola Mohammad Al Soubaihi, KTH Royal Institute of Technology
Khaled M. Saoud, Virginia Commonwealth UniversityFollow
Joydeep Dutta, KTH Royal Institute of Technology

Document Type

Article

Original Publication Date

2022

Journal/Book/Conference Title

Surfaces and Interfaces

Volume

29

DOI of Original Publication

10.1016/j.surfin.2022.101776

Comments

Originally published at https://doi.org/10.1016/j.surfin.2022.101776

Date of Submission

November 2023

Abstract

The catalyst morphology, metal-support interaction, and reaction conditions greatly influence the catalytic performance and reaction dynamics. Similarly, the dispersion of the metal within the support plays a crucial role in the thermal stability and sintering of the catalyst. Furthermore, temperature-dependent conversion hysteresis is well-known to occur during ignition and extinction of exothermic CO oxidation over supported Pd catalysts due to the variation of CO adsorption on the surface or bulk oxidation of Pd and the ability of the catalyst to regenerate the active sites. Herein, the catalytic performance and the hysteresis behavior of mesoporous silica aerogel supported Pd (Pd/a-SiO2), and commercial fumed silica-supported Pd (Pd/f-SiO2) were investigated and compared using CO oxidation as a probe reaction under different reaction conditions and operating parameters (i.e., catalyst weight, ramp rate, and flow rate). Surface and morphologic examination using XPS, FTIR, and TEM of Pd/a-SiO2 and Pd/f-SiO2 reveal a strong correlation between the catalyst surface and structure and its catalytic performance and stability under different reaction parameters. Moreover, this study presents the effect of surface area, particle size, and size distribution on diffusion and mass transport of reactants (CO, O2) and products (CO2) and active sites accessibility.

This study showed that Pd/f-SiO2 had better efficiency under high (turbulence) flow. Moreover, intrinsic apparent activation energy (Ea) and the number of active sites were calculated from the Kinetics of CO oxidation fitted using Arrhenius plots indicate that the ramp rate has less effect on Pd/f-SiO2 catalytic behavior. Even though, Pd/f-SiO2 had higher relative active sites than Pd/a-SiO2, (Ea) was lower. Cyclic stability and long-term stabilities showed that both catalysts are stable and can regenerate the active sites. The current study contributes to understanding the catalysts' surface, structural and morphological properties on the catalysts' performance toward CO oxidation and other reactions under dynamic conditions.

Rights

© 2022 The Author(s). This is an open access article distributed under the terms of the Creative Commons CC-BY license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.