Spatial Concentration Profiles for the Catalytic Partial Oxidation of Jet Fuel Surrogates in a Rh/Al2O3 Coated Monolith

Julian Bär,Lubow Maier,Olaf Deutschmann,Claudia Antinori

doi:10.3390/catal6120207

Julian Bär, Lubow Maier + Show 2 more

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https://doi.org/10.3390/catal6120207

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Abstract

The catalytic partial oxidation (CPOX) of several hydrocarbon mixtures, containing n-dodecane (DD), 1,2,4-trimethylbenzene (TMB), and benzothiophene (BT) as a sulfur compound was studied over a Rh/Al2O3 honeycomb catalyst. The in-situ sampling technique SpaciPro was used in this study to investigate the complex reaction system which consisted of total and partial oxidation, steam reforming, and the water gas shift reaction. The mixtures of 83 vol % DD, 17 vol % TMB with and without addition of the sulfur compound BT, as well as the pure hydrocarbons were studied at a molar C/O-ratio of 0.75. The spatially resolved concentration and temperature profiles inside a central channel of the catalyst revealed three reaction zones: an oxidation zone, an oxy-reforming zone, and a reforming zone. Hydrogen formation starts in the oxy-reforming zone, not directly at the catalyst inlet, contrary to methane CPOX on Rh. In the reforming zone, in which steam reforming is the predominant reaction, even small amounts of sulfur (10 mg S in 1 kg fuel) block active sites.

Highlights

The catalytic partial oxidation (CPOX) of liquid hydrocarbons over rhodium at short contact times is an efficient route to on-board syngas production for a fuel cell with the reformer and the fuel cell forming an auxiliary power unit [1,2,3,4,5,6]
It is reported that the CPOX process follows a reaction sequence, in which the reaction system could be divided into two reaction zones along the catalyst
As hydrogen is detected in the first reaction zone for methane CPOX on rhodium, a direct route for partial oxidation was suggested

Summary

Introduction

The catalytic partial oxidation (CPOX) of liquid hydrocarbons over rhodium at short contact times is an efficient route to on-board syngas production for a fuel cell with the reformer and the fuel cell forming an auxiliary power unit [1,2,3,4,5,6]. In-situ investigations on the CPOX of methane as well as microkinetic modeling studies were crucial to unravel possible reaction pathways in order to establish reaction mechanisms and to gain an insight into different reaction zones [10,12,15,16,17,18]. In these papers, it is reported that the CPOX process follows a reaction sequence, in which the reaction system could be divided into two reaction zones along the catalyst. Due to the highly exothermic total oxidation, a hot spot occurs in the first few millimeters of the catalyst Within this oxy-reforming zone, oxygen is completely consumed. Capillary-based in-situ techniques revealed further reaction pathways, e.g., the homogeneous dehydrogenation of Catalysts 2016, 6, 207; doi:10.3390/catal6120207 www.mdpi.com/journal/catalysts

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