Improved Hydrothermal Stability in Glass Diesel Soot Oxidation Catalysts

James Zokoe,Paul J Mcginn,Changsheng Su,Xiaoxiang Feng

doi:10.3390/catal9080684

James Zokoe, Paul J Mcginn + Show 2 more

Open Access

https://doi.org/10.3390/catal9080684

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Abstract

The hydrothermal stability of K-Ca-Si-O glass soot oxidation catalysts has been improved by substitution of Ce and Zr for Ca. This work demonstrates that glasses can be tailored to withstand the challenging diesel exhaust hydrothermal environment by considering the field strengths and partial molar free energies of the hydration reactions (ΔGi) of the cation species in the glass. The result is a glass that shows less formation of precipitates after 2 h hydrothermal exposure in air with 7% H2O at temperatures ranging from 300–700 °C. A K-Ca-Si-O glass with a soot T50 (the temperature when 50% of the soot is oxidized) of 394 °C was found to degrade to 468 °C after a 2 h, 700 °C hydrothermal exposure, whereas the improved K-Ce-Zr-Si-O glass only changed from 407 °C to 427 °C after the same treatment.

Highlights

A diesel particulate filter (DPF) is used to remove harmful soot particles from the exhaust stream of a diesel engine
In this research we examine the effects of modifying a simple potassium calcium silicate glass through
The hydrothermal stability of K-Ca-Si-O glass soot oxidation catalysts in a diesel exhaust environment can be improved by considering the field strengths and partial molar free energies of the hydration reactions (∆Gi ) of the cation species in the glass

Summary

Introduction

A diesel particulate filter (DPF) is used to remove harmful soot particles from the exhaust stream of a diesel engine. Replacing the Ca in the K-glass composition with another stabilizing element that is catalytically active in soot oxidation could improve the useful lifetime performance of the glass catalyst. Based on the ionic field strength reasoning described above, one expects improved glass stability (reduced corrosion) with ZrO2 additions. This has been shown to be the case in several studies [48,49]. Additions of Zr to a K-glass catalyst could allow replenishment of K+ ions to the surface during K depletion events, such as soot oxidation with reduced humidity, by forcing the silicate structure to remain open, effectively allowing better use of the sub-surface K.

Catalytic Activity Characterization by HR-TGA

Hydrothermal Testing of KCeSZ-1 Glass Composition

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Materials and Methods

Conclusions