Simulating Real World Soot-Catalyst Contact Conditions for Lab-Scale Catalytic Soot Oxidation Studies

Changsheng Su,Paul Mcginn,Yujun Wang,Ashok Kumar

doi:10.3390/catal8060247

Abstract

In diesel soot oxidation studies, both well-defined model soot and a reliable means to simulate realistic contact conditions with catalysts are crucial. This study is the first attempt in the field to establish a lab-scale continuous flame soot deposition method in simulating the “contact condition” of soot and a structured diesel particulate filter (DPF) catalyst. The properties of this flame soot were examined by means of X-ray diffraction (XRD) and transmission electron microscopy (TEM) for structure analysis, Brunauer-Emmett-Teller (BET) for surface area analysis, and thermogravimetric analysis (TGA) for reactivity and kinetics analysis. For validation purposes, catalytic oxidation of Tiki® soot using the simulated contact condition was conducted to compare with the diesel particulates collected from a real diesel engine exhaust system. It was found that the flame soot is more uniform and controllable than similar samples of collected diesel particulates. The change in T50 due to the presence of the catalyst is very similar in both cases, implying that the flame deposit method is able to produce comparably realistic contact conditions to that resulting from the real exhaust system. Comparing against the expensive engine testing, this novel method allows researchers to quickly set up a procedure in the laboratory scale to reveal the catalytic soot oxidation properties in a comparable loose contact condition.

Highlights

Diesel soot consists of agglomerates with diameters of up to several hundred nanometers and a fine structure of spherical primary particles
The results reveal that the majority of constituents in diesel particulates and model soot were carbon, oxygen, and hydrogen, with low concentrations of nitrogen and sulphur
The change in T50 due to the presence of the catalyst is very similar in both cases, implying that the flame deposit method is able to produce comparably realistic, albeit slightly looser, contact conditions to that resulting from the real exhaust system

Summary

Introduction

Diesel soot consists of agglomerates with diameters of up to several hundred nanometers and a fine structure of spherical primary particles. Unlike the well understood formation of NOx in internal combustion engines, the formation of soot is still more ambiguous because the process is more complicated and difficult to examine [1]. The characterization of diesel particulates from a particular engine at different operational conditions may vary considerably due to variations in combustion parameters [2] and diesel fuels [3]. Laboratory studies often utilize diffusion flames in burners, because the soot formation processes in burner diffusion flames are thought to be fundamentally similar to those in diesel engines [4] with sequential nucleation, growth and agglomeration steps taking place. It is generally accepted that the particle size, surface area and overall

Methods

Results

Discussion

Conclusion