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Iron Oxide over Silica-Doped Alumina Catalyst for Catalytic Steam Reforming of Toluene as a Surrogate Tar Biomass Species Muflih A Adnan, Oki Muraza, Shaikh Abdur Razzak, Mohammad Mozahar Hossain, and Hugo I. de Lasa Energy Fuels, Just Accepted Manuscript • Publication Date (Web): 13 Jun 2017 Downloaded from http://pubs.acs.org on June 14, 2017
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Energy & Fuels
Iron Oxide over Silica-Doped Alumina Catalyst for Catalytic Steam Reforming of Toluene as a Surrogate Tar Biomass Species Muflih A. Adnana,d, Oki Murazaa,b, Shaikh A. Razzak, Mohammad M. Hossaina,b*, Hugo I. de Lasac a
Chemical Engineering Department, bCenter of Research Excellence in Nanotechnology, King Fahd University of Petroleum & Minerals, Dhahran 31261, Saudi Arabia c Chemical Reactor Engineering Centre, Faculty of Engineering Science, University of Western Ontario, London, Ontario, Canada N6A 5B9 d Department of Chemical Engineering, Islamic University of Indonesia, Yogyakarta 55584, Indonesia
Abstract An iron oxide over silica-doped alumina catalyst was successfully synthesized using one-pot, solvent-deficient method. The prepared Fe2O3/SiO2-Al2O3 catalyst was characterized using TGA/DTG, XRD, N2 adsorption isotherm, NH3-TPD and SEM. The TGA/DTG and XRD results show that the presence of Si enhances the stability of γ-Al2O3 support at high temperatures. The prepared Fe2O3/SiO2-Al2O3 catalyst was obtained by calcination at 950oC, with a high BET specific surface area (49 m2/g). The NH3-TPD showed that Fe addition can significantly increase catalyst acidity. SEM images confirmed the textural properties of the catalysts in term of surface morphology. The Fe2O3/SiO2-Al2O3 catalytic activity for toluene steam reforming was examined in a CREC fluidized Riser Simulator at various reaction times and temperatures. Experiments with this catalyst yielded high toluene conversions. Composition of gases produced (H2, CO, CO2 and CH4) were close to chemical equilibrium at 25 s and 600°C. These results indicate that the Fe2O3/SiO2-Al2O3 catalyst is a promising fluidizable catalyst for tar reduction. This novel supported metal oxide catalyst has a great potential for industrial use since it is a relatively cheap, less toxic, and long-lasting operation. Keywords: gasification; toluene steam reforming; iron oxide; silica alumina; catalyst. *Corresponding Author: E-mail:
[email protected] (M. M. Hossain)
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Introduction
In recent years, worldwide energy demand is growing as a pace as a result of the fast rates of economic1. The consumption of fossil fuels as a main energy source causes serious environmental problems such as climate change and acid rain. Attempts on substituting fossil fuels by renewable energy is becoming very essential. Biomass is an attractive renewable energy since it is considered as both carbon neutral cycle and low sulfur content2, 3. Biomass as a renewable energy feedstock has been applied to fermentation, direct combustion, pyrolysis and gasification3, 4. Gasification is one of the best alternatives for biomass conversion. Common products species from biomass gasification are permanent gases, tars, unreacted char and inert ash. Gas product contains H2, CO, CO2 and CH4, and is frequently designated as producer gas. Producer gas offers flexibility since it can be easily converted into heat, electricity and petrochemical products5-7.
Formation of tars is a major issue in biomass gasification. During gasification tars are mainly produced from decomposition of lignocellulosic biomass in the pyrolysis stage8. Condensation of tars causes operational problems in the downstream units such the pipes, filters, gas engine, and others3, 9. Furthermore, the presence of tars lower process efficiency, since condensed tars consist of aromatic hydrocarbons which contain a large amount of energy. Tar composition is affected by many factors such as the gasification operating conditions, type of gasifier and type of biomass5,
10-12
. Typically, toluene is the main compound of the tar produced from biomass
gasification5. Physical, thermal and catalytic tar conversion are the common processes to eliminate the tars in the producer gas6, 13, 14. Among these processes, catalytic tar conversion is
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Energy & Fuels
the most attractive one since the catalytic tar conversion requires low energy and simple reactor design3, 13, 15.
Regarding catalytic tar cracking, catalysts should display high catalytic activity, high resistance towards carbon deposition, and withstand on harsh condition16. Concerning catalysts for tar conversion, olivine and dolomite are possible alternatives given their thermal and mechanical stability, and fair cracking activity. However, those natural minerals require relatively high reaction temperatures (above 850°C) to achieve significant tar conversions. For instance, at 750°C tar conversion is limited to 21%. In addition, the surface area of these natural minerals is very low (
