Εργαστήριο Εναλλακτικών Καυσίμων & Περιβαλλοντικής Κατάλυσης
Title: An in depth investigation of deactivation through carbon formation during the biogas dry reforming reaction for Ni supported on modified with CeO2 and La2O3 zirconia catalysts [view paper]
Journal: International Journal of Hydrogen Energy 43 (2018) 18955-18976.
Authors: N.D. Charisiou1, G. Siakavelas1, L. Tzounis2, V. Sebastian3,4, A. Monzon3, M.A. Baker5, S.J. Hinder5, K. Polychronopoulou6,7, I.V. Yentekakis8, M.A Goula1,*
Affiliations:
1Laboratory of Alternative Fuels and Environmental Catalysis (LAFEC), Department of Environmental and Pollution Control Engineering, Western Macedonia University of Applied Sciences, GR-50100, Kozani, Greece
2Composite and Smart Materials Laboratory (CSML), Department of Materials Science & Engineering, University of Ioannina, GR-45110, Ioannina, Greece
3Department of Chemical and Environmental Engineering & Institute of Nanoscience of Aragon (INA), University of Zaragoza, SP-50018, Zaragoza, Spain
4Networking Research Center on Bioengineering, Biomaterials and Nanomedicine, CIBERBBN, 28029 Madrid, Spain
5The Surface Analysis Laboratory, Faculty of Engineering and Physical Sciences, University of Surrey, Guildford, GU2 4DL, UK
6Department of Mechanical Engineering, Khalifa University of Science and Technology, Abu Dhabi, P.O. Box 127788, UAE
7Center for Catalysis and Separation, Khalifa University of Science and Technology, Abu Dhabi, P.O. Box 127788, United Arab Emirates
8Laboratory of Physical Chemistry & Chemical Processes, School of Environmental Engineering, Technical University of Crete, GR-73100, Chania, Crete, Greece
Abstract
The dry reforming of biogas on a Ni catalyst supported on three commercially available materials (ZrO2, La2O3-ZrO2 and CeO2-ZrO2), has been investigated, paying particular attention to carbon deposition. The DRM efficiency of the catalysts was studied in the temperature range of 500-800oC at three distinct space velocities, and their time-on-stream stability at four temperatures (550, 650, 750 and 800oC) was determined for 10 or 50 h operation. The morphological, textural and other physicochemical characteristics of fresh and spent catalysts together with the amount and type of carbon deposited were examined by a number of techniques including BET-BJH method, CO2 and NH3-TPD, XPS, SEM, TEM, STEM-HAADF, Raman spectroscopy, and TGA/DTG. The impact of the La2O3 and CeO2 modifiers on the DRM performance and time-on-stream stability of the Ni/ZrO2 catalyst was found to be very beneficial: up to 20 and 30% enhancement in CH4 and CO2 conversions respectively, accompanied with a CO-enriched syngas product, while the 50 h time-on-stream catalytic performance deterioration of ~30-35% on Ni/ZrO2 was limited to less than ~15-20% on the La2O3 and CeO2 modified samples. Their influence on the amount and type of carbon formed was substantial: it was revealed that faster oxidation of the deposited carbon at elevated temperatures occurs on the modified catalysts. Correlations between the La2O3 and CeO2-induced modifications on the surface characteristics and physicochemical properties of the catalyst with their concomitant support-mediated effects on the overall DRM performance and carbon deposition were revealed.
Reforming of Glycerol
Biodiesel production has grown, between 2005 and 2015, at almost 25% per annum (reaching approximately 32 billion liters), leading to a seven-fold expansion of the sector. Although biodiesel is thought of as a renewable, biodegradable, environmentally-friendly fuel, there are concerns over the production of glycerol, the main by product of the transesterification reaction (it accounts for 10% of the volume of oil undergoing the reaction).
An innovative option is the energetic utilization of glycerol via steam reforming (SR), as every mole of glycerol fed to the reactor can theoretically produce seven moles of hydrogen. At LAFEC we have devoted our efforts towards the design of appropriate catalysts based on transition metals that can be used in the GSR. In some of our previous works, we reported on the performance of different transition metals (Ni, Co, Cu) on silica [BioResources 11 (2016) 10173-89] and alumina [Fuel Process Technol 152 (2016) 156-75], of Ni catalysts based on alumina, zirconia, silica [Top Catal 60 (2017) 1226-50] and apatite-type lanthanum silicates supports [RSC Adv 6 (2016) 78954-8], the influence of the synthesis method on Ni/Al catalysts [Chinese J Catal 37 (2016) 1949-65], the effect of the addition of lanthana on Ni/Al catalysts [Int J Hydrogen Energ 42 (2017) 13039-60], the effect of the addition of CaO-MgO on Ni/Al catalysts [Int J Hydrogen Energ 44 (2019) 256-273], the use of AlCeO3 as supporting material for a Ni catalyst [Catalysts 9 (2019) 411], the effect of the addition of silica [Top Catal 60 (2017) 1226-1250] or yttria [Int J Hydrogen Enrg, In press] on Ni/ZrO2 catalysts. We have also tested Ce-Sm-xCu [Sust Energ Fuels 3 (2019) 673-691] and Ni/Ce-Sm-xCu [Nanomaterials 8 (2018) 931] catalysts. A comprehensive literature review with particular focus on the main catalysts and support systems under development has also been carried out [Surf Coat Technol 352 (2018) 92-111].
Moreover, we have also examined glycerol reforming via chemical looping using Ni/ZrO2 nano-composite oxygen carriers [Int J Hydrogen Energ 43 (2018) 13200-11].
CO2 Utilization - Biogas Dry Reforming
It is well understood that human activities, emanating from current practices relating to the production and consumption of fossil based energy have an unequivocal impact upon the global climate. A promising technology is the Dry Reforming of Biogas, as the process makes use of the main greenhouse gases (CH4 and CO2), and can provide a renewable resource with a potential zero carbon footprint. The product of this process is syngas, a key chemical feedstock for the synthesis of oxygenated chemicals and hydrocarbons from Fisher – Tropsch synthesis.
At LAFEC we have examined the performance of nickel catalysts based on alumina modified with ceria, lanthana [J Nat Gas Sci Eng 31 (2016) 164-83 & Catal Today 195 (2012) 93-100], magnesia or calcium [Waste Biomass Valori 7 (2016) 725-36]. A theoretical investigation of Ni-Al2O3 and Ni/CeO2-Al2O3 has also been performed [Int J Hydrogen Energ 35 (2010) 9818-27].
We have also devoted effort in investigating the performance of Nickel catalysts based on zirconia modified with ceria, lanthana [Int J Hydrogen Energ 42 (2017) 13724-40] and tugsten [Front Environ Sci 5 (2017) 66]. Moreover, we have examined different synthesis techniques in an effort to maximize the dispersion of active phase and optimize the active species [Catal Today 46, 175-83; Int J Hydrogen Energ 40 (2015) 9183-00].
Finally, we have committed ourselves at investigating the carbonaceous species formed during the reaction [J Catal 161, 626-40; Adv Mater Proc 2 (2017) 807-12; Mater Today: Proc. 5 (2018) 27607-27616; Int J Hydrogen Energ 43 (2018) 18955-18976; Appl Surf Sci 474 (2019) 42-56], as it is one of the main reasons for catalyst deactivation.
NOx and SO2 abatement
Nitrogen and sulphur oxide abatement is a subject of major environmental importance, as Nitric (NOx) and Sulphur (SOx) oxides are recognized as important precursors of acid rain, contributors to the formation of photochemical smog and to the destruction of the ozone layer. Recently, a lot of academic and policy attention has focused on N2O emissions control. Nitrous oxide (N2O) is listed as one of the most harmful greenhouse gases with a strong global warming potential (310 times higher than that of CO2), that severely contributes to the stratospheric ozone layer depletion.
At LAFEC, we were the first to investigate the lean NOx reduction by propene, H2 as well as by propene + H2 over supported (on γ-Al2O3), low loading (0.5 wt%), Pt, Pd and Ir catalysts [J Environ Chem Eng 4 (2016) 1629-41]. In addition, we have examined the impact of alkali promoters (K) on the physicochemical properties and catalytic performance of Ir/Al2O3 catalysts towards the N2O decomposition [Top Catal 59 (2016) 1020-7]. Finally, we have examined the deactivation and regeneration procedures of copper oxide catalysts/sorbents that are supported on Al2O3, SiO2, CeO2-Al2O3, in the presence of SO2 and identified the appropriate conditions for the simultaneous removal of NO and SO2 [Global Nest J 14 (2012) 166-74].
Selective deoxygenation (SDO) of natural triglycerides
There are two main drawbacks associated with the production of biodiesel through the transesterification reaction: (a) The unsuitability of plant oils with relatively high acidity for transesterification catalyzed by basic solutions, and (b) the increasing accumulation of glycerol, the main sub-product of the process.
However, natural triglycerides can be upgraded using selective deoxygenation (SDO), which is realized by hydrotreatment via decarboxylation (deCO2), decarbonylation (deCO) and hydrodeoxygenation (HDO), to hydrocarbons in the range of petro-diesel (green or renewable diesel).
At LAFEC we have set up appropriate experimental procedures and are investigating the: (i) effect of supports, metal loading and promoters on catalytic performance, (ii) SDO pathways over transition metallic catalysts, and (iii) effect of preparation method on catalytic performance.
We have recently published a comprehensive literature review on the topic [Energies 12 (2019) 809].