The Effect of Noble Metal (M: Ir, Pt, Pd) on M/Ce2O3-γ-Al2O3 Catalysts for Hydrogen Production via the Steam Reforming of Glycerol

Nikolaos D Charisiou,Victor Sebastian,Maria A Goula,Georgios I Siakavelas,Kyriaki Polychronopoulou,Kyriakos N Papageridis,Davide Motta,Nikolaos Dimitratos

doi:10.3390/catal10070790

Abstract

A promising route for the energetic valorisation of the main by-product of the biodiesel industry is the steam reforming of glycerol, as it can theoretically produce seven moles of H2 for every mole of C3H8O3. In the work presented herein, CeO2–Al2O3 was used as supporting material for Ir, Pd and Pt catalysts, which were prepared using the incipient wetness impregnation technique and characterized by employing N2 adsorption–desorption, X-Ray Diffraction (XRD), Temperature Programmed Reduction (TPR), Temperature Programmed Desorption (TPD), X-ray Photoelectron Spectroscopy (XPS) and Transmission Electron Microscopy (TEM). The catalytic experiments aimed at identifying the effect of temperature on the total conversion of glycerol, on the conversion of glycerol to gaseous products, the selectivity towards the gaseous products (H2, CO2, CO, CH4) and the determination of the H2/CO and CO/CO2 molar ratios. The main liquid effluents produced during the reaction were quantified. The results revealed that the Pt/CeAl catalyst was more selective towards H2, which can be related to its increased number of Brønsted acid sites, which improved the hydrogenolysis and dehydrogenation–dehydration of condensable intermediates. The time-on-stream experiments, undertaken at low Water Glycerol Feed Ratios (WGFR), showed gradual deactivation for all catalysts. This is likely due to the dehydration reaction, which leads to the formation of unsaturated hydrocarbon species and eventually to carbon deposition. The weak metal–support interaction shown for the Ir/CeAl catalyst also led to pronounced sintering of the metallic particles.

Highlights

Anthropogenic dominance over the planet is so profound that the term ‘anthropocene’ has been proposed as a more apt description of the current geological epoch
The catalytic experiments aimed at identifying the effect of temperature on the total conversion of glycerol, on the conversion of glycerol to gaseous products, the selectivity towards the gaseous products (H2, CO2, CO, CH4 ) and the determination of the H2 /CO and CO/CO2 molar ratios
CeAl (17%), while SCO is of the order Ir/CeAl ≈ Pd/CeAl (69%) > Pt/CeAl (41%). These results show that the reverse water–gas-shift reaction probably dominates at high temperatures on the Pd and Ir catalysts; in contrast, its prevalence appears to diminish at high temperatures for the Pt/CeAl sample

Summary

Introduction

Anthropogenic dominance over the planet is so profound that the term ‘anthropocene’ has been proposed as a more apt description of the current geological epoch. Systems (RES) for electricity production, in the transport sector petro-energy retains a protagonists0 role, with current efforts in finding an alternative relying on the development of starch- and sugar-based ethanol, deoxygenation for the production of bio-hydrogenated diesel, and fatty acid methyl ester (FAME) biodiesel [1,2,3,4]. As glycerol (C3 H8 O3 ) is a polyol with three hydroxyl groups, it may be possible to utilize it in a plethora of industrial platforms (Bagheri et al [9] has provided an excellent review on the different technological pathways that are currently being developed) the pressing need for further ‘greening’ of the energy sector, means that its conversion to hydrogen via thermochemical processes (i.e., via pyrolysis or different reforming reactions) is perhaps the most attractive option [10,11,12,13].

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Results

Conclusion