Demonstration of the Use of 3D X-ray Tomography to Compare the Uniformity of Catalyst Coatings in Open-Cell Foams

Marie-Line Zanota,Stéphanie Pallier,Anaïs Dousse,Valérie Meille,Joël Lachambre

doi:10.3390/chemengineering2040052

Abstract

Coating open-cell foams by a catalytic layer is a necessary step to obtain structured catalytic foam reactors. The dip-coating method, consisting of immersing the foam in a suspension or in a sol-gel, is generally used to obtain the coating. The excess of liquid has to be evacuated from the foam to obtain a thin layer. Different methods to remove this excess of liquid have been investigated in the present work. The objective was to show that 3D X-ray tomography coupled to image analysis could be a tool to discriminate the methods by analysing the spatial localisation of the catalyst layer throughout the whole foam samples. A simple blowing by air in every direction seems to not be appropriate to obtain uniform coatings.

Highlights

Monolithic catalysts have been studied for decades, as catalytic converters of exhaust gas in cars, and for various gas/solid and gas/liquid/solid reactions [1,2,3]
Using catalyst-coated foams in chemical reactor engineering has become a standard in laboratories to improve mass and heat transfer and avoid high pressure drops [7,8]
Concerning the coating characterization, a sample of commercial catalytic monolith for automotive exhaust gas after treatment was scanned by X-ray microtomography to obtain realistic 3D images of the coated layer [19]

Summary

Introduction

Monolithic catalysts have been studied for decades, as catalytic converters of exhaust gas in cars, and for various gas/solid and gas/liquid/solid reactions [1,2,3]. Concerning the coating characterization, a sample of commercial catalytic monolith for automotive exhaust gas after treatment was scanned by X-ray microtomography to obtain realistic 3D images of the coated layer [19]. It has been used by the group of Lange [20,21] to check the thickness distribution throughout a whole foam. We use the 3D microtomography tool to estimate the coating thickness and we go further, by comparing several methods that can be used at lab scale to remove the excess suspension from an open cell foam. The method is applied to catalytic coatings in the present article but could be applied to other thin films [23]

Objectives

Methods

Results

Conclusion