Dear Mrs. Sahar,

You can use pyridine adsorption for determining acidic sites by FTIR technique. You can also use XRD and debye scherrer equation for particle size.

May I can provide you with some characterization

Article

Nickel supported on AlCeO3 as a highly selective and stable catalyst for hydrogen production via the glycerol steam reforming reaction

Nikolaos D. Charisiou1, Georgios I. Siakavelas1, Binlin Dou2, Victor Sebastian3,4, Steven J. Hinder5, Mark A. Baker5, Kyriaki Polychronopoulou6,7,*, Maria A. Goula1,*

1 Laboratory of Alternative Fuels and Environmental Catalysis (LAFEC), Department of Environmental and Pollution Control Engineering, Western Macedonia University of Applied Sciences, GR-50100, Greece; [email protected] (N.D.C.); [email protected] (G.I.S.); [email protected] (M.A.G.)

2 School of Energy and Power Engineering, University of Shanghai for Science and Technology, Shanghai 200093, China; [email protected]

3 Chemical and Environmental Engineering Department, Instituto de Nanociencia de Aragón (INA) and Instituto de Ciencia de Materiales de Aragón (ICMA), Universidad de Zaragoza-CSIC, 50018 Zaragoza, Spain; [email protected]

4 Networking Research Center on Bioengineering, Biomaterials and Nanomedicine, CIBERBBN, 28029 Madrid, Spain; [email protected]

5 The Surface Analysis Laboratory, Faculty of Engineering and Physical Sciences, University of Surrey, Guildford, GU2 4DL, UK; [email protected] (S.J.H.); [email protected] (M.A.B.)

6 Department of Mechanical Engineering, Khalifa University of Science and Technology, Abu Dhabi, P.O. Box 127788, UAE; [email protected]

7 Center for Catalysis and Separation, Khalifa University of Science and Technology, Abu Dhabi, P.O. Box 127788, UAE; [email protected]

* Correspondence: [email protected] (M.A.G.); [email protected] (K.P.)

Received: date; Accepted: date; Published: date

Abstract: In this study, a critical comparison between two low metal (Ni) loading catalysts is presented, namely Ni/Al2O3 and Ni/AlCeO3 for the glycerol steam reforming (GSR) reaction. The surface and bulk properties of the catalysts were evaluated using a plethora of techniques, such as N2 adsorption/desorption, ICP-AES, XRD, XPS, SEM/EDX, TEM, CO2-TPD, NH3-TPD, H2-TPR. Carbon deposited on the catalysts surfaces was probed using TPO, SEM and TEM. It is demonstrated that Ce-modification of Al2O3 induces an increase of the surface basicity and Ni dispersion. These features lead to a higher conversion of glycerol to gaseous products (60% to 80%), particularly H2 and CO2, enhancement of WGS reaction and a higher resistance to coke deposition. Allyl alcohol was found to be the main liquid product for the Ni/AlCeO3 catalyst, the production of which ceases over 700 oC. It is also highly significant that the Ni/AlCeO3 catalyst demonstrated stable values for H2 yield (2.9-2.3) and selectivity (89-81%), in addition to CO2 (75-67%) and CO (23-29%) selectivity during a (20h) long time-on-stream study. Following the reaction, SEM/EDX and TEM analysis showed heavy coke deposition over the Ni/Al2O3 catalyst, whereas for the Ni/AlCeO3 catalyst TPO studies showed the formation of more defective coke, the latter being more easily oxidized.

Keywords: Nickel catalysts, ceria, alumina, glycerol steam reforming, H2 production

1. Introduction

Biofuels are expected to play an important role in meeting the combined challenge of providing adequate energy supplies, while simultaneously combating the threat posed by climate change, with projections estimating that their use will grow from 1.3 million barrels of oil equivalent (BOE) in 2012 to 4.6 BOE in 2040 [1]. Although biodiesel had captured approximately 25% of total biofuel output in 2015 [2], the high costs associated with its production means that the sector remains uncompetitive, with favourable government policies underpinning much of its growth [3]. The industry is also facing the challenge of dealing, in a sustainable way, with the co-production of crude glycerol (C3H8O3), which constitutes its major by-product and amounts to approximately 10 wt.% of the oil undergoing transesterification [4].

However, glycerol can be converted into hydrogen, a fuel that finds a variety of present day applications in transport, building and other industry sectors, while at the same time is expected to have a leading role in a future carbon free energy mix [5]. Although different thermochemical processes may be used for the conversion of C3H8O3 into H2 - e.g., aqueous phase reforming (APR), autothermal reforming (ATR) and super critical water reforming (SCWR) - the process that appears most promising is that of the steam reforming of glycerol (GSR) [6-8]. This is because GSR has a high H2 production capacity per mol of C3H8O3 reformed (Eq. 1) and is a mature industrial technology unlikely to require major technical adjustments in switching feedstocks [9,10]. The GSR (Eq. 1), a strongly endothermic reaction (ΔΗΘ = 123 kJ/mole), combines the decomposition of glycerol (Eq. 2) and the water-gas shift reaction (WGS, Eq. 3), but a number of parallel reactions that include methanation (Eq. 4), methane dry reforming (Eq. 5) and carbon formation reactions (Eqs. 6-9) also take place [11,12]. According to the thermodynamic studies undertaken, the GSR should be undertaken at high temperature (>630 oC), high water to glycerol feed ratio (WGFR