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The present work focuses on the development of efficient desulphurization processes for multi-fuel reformers for hydrogen production. Two processes were studied: liquid hydrocarbon desulphurization and H2S removal from reformate gases. For each process, materials with various chemical compositions and microporous structures were synthesized and characterized with respect to their physicochemical properties and desulphurization ability. In the case of liquid phase desulphurization, the adsorption of sulphur compounds contained in diesel fuel under ambient conditions was studied employing as sorbents, zeolite-based materials, i.e. NaY, HY and metal ion-exchanged NaY and HY, as well as a high-surface area activated carbon (AC), for three different diesel fuels with sulphur content varying between 5 and 180 ppmw. Among all sorbents studied, AC showed the best desulphurization performance followed by cerium ion-exchanged HY. The gas phase desulphurization experiments involved the evaluation of zinc-based mixed oxides, synthesized by non-conventional (combustion synthesis) techniques on high steam content reformate gas mixtures.
Article Outline
1. Introduction
2. Experimental
2.1. Materials synthesis and characterization
2.1.1. Sorbents for liquid phase desulphurization
2.1.2. Sorption materials for gas phase desulphurization
2.2. Experimental procedure
2.2.1. Liquid phase desulphurization
2.2.2. Gas phase desulphurization
3. Results and discussion
3.1. Liquid phase desulphurization
3.2. Gas phase desulphurization
4. Conclusions
Acknowledgements
References
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673
Mathematical modeling of an industrial steam-methane reformer for on-line deployment Original Research Article
Fuel Processing Technology, Volume 92, Issue 8, August 2011, Pages 1574-1586
Dean A. Latham, Kimberley B. McAuley, Brant A. Peppley, Troy M. Raybold
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Abstract
A mathematical model of an industrial steam-methane reformer (SMR) is developed for use in monitoring tube-wall temperatures. The model calculates temperature profiles for the outer-tube wall, inner-tube wall, furnace gas and process gas. Inputs are the reformer inlet-stream conditions, the furnace geometry and material properties of the furnace and catalyst-bed. The model divides the reformer into zones of uniform temperature and composition. Radiative-heat transfer on the furnace side is modeled using the Hottel Zone method. Energy and material balances are solved numerically. The effect of important model parameters on reformer temperature profiles is assessed and the parameters are fit to data from an industrial SMR. At plant rates greater than 85% the model accurately predicts the process-gas outlet temperature, composition, pressure, flow rate and tube-wall temperatures. The adjustable parameters may need to be re-estimated using additional low plant rate data. The model has the capacity to be developed into a more complex model that accounts for classes of tubes associated with different radiative environments.
Article Outline
1. Introduction
2. Mathematical model
3. Numerical methods
3.1. Fitting of model parameters using industrial data
4. Results and discussion
5. Conclusion
Acknowledgements
Nomenclature
References
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Highlights
► Model developed for industrial top-fired steam-methane reformer. ► Zone furnace model with 1-D fixed-bed tube model. ► Adjust parameters to match tube temperatures. ► Predict temperatures within 95% confidence intervals at high rates. ► Advanced models possible for wall tubes and center tubes.
674
Ethanol internal steam reforming in intermediate temperature solid oxide fuel cell Original Research Article
Journal of Power Sources, In Press, Corrected Proof, Available online 18 November 2010
Stefan Diethelm, Jan Van herle
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Abstract
This study investigates the performance of a standard Ni–YSZ anode supported cell under ethanol steam reforming operating conditions. Therefore, the fuel cell was directly operated with a steam/ethanol mixture (3 to 1 molar). Other gas mixtures were also used for comparison to check the conversion of ethanol and of reformate gases (H2, CO) in the fuel cell. The electrochemical properties of the fuel cell fed with four different fuel compositions were characterized between 710 and 860 °C by I–V and EIS measurements at OCV and under polarization. In order to elucidate the limiting processes, impedance spectra obtained with different gas compositions were compared using the derivative of the real part of the impedance with respect of the natural logarithm of the frequency.
Results show that internal steam reforming of ethanol takes place significantly on Ni–YSZ anode only above 760 °C. Comparisons of results obtained with reformate gas showed that the electrochemical cell performance is dominated by the conversion of hydrogen. The conversion of CO also occurs either directly or indirectly through the water–gas shift reaction but has a significant impact on the electrochemical performance only above 760 °C.
Article Outline
1. Introduction
2. Experimental
2.1. Catalytic tests
2.2. Electrochemical tests
3. Results and discussion
3.1. Catalysis
3.2. Electrochemistry
3.3. Comparison of performance with dry and humid mixtures: effect of steam
3.4. Comparison of performance with humid and syngas mixtures: effect of CO/CO2
3.5. Comparison of performance with syngas and ethanol mixture
4. Conclusions
Acknowledgements
References
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675
Internal reforming of hydrocarbon fuels in tubular solid oxide fuel cells
International Journal of Hydrogen Energy, Volume 33, Issue 7, April 2008, Pages 1853-1858
P.K. Cheekatamarla, Caine M. Finnerty, Jun Cai
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Abstract
The application of heterogeneous catalysis has an important role to play in the successful commercial development of solid oxide fuel cell (SOFC) technology. In this paper, we present an SOFC that combines a catalyst layer with a conventional anode, allowing internal reforming via partial oxidation (POX) of fuels such as methane, propane, butane, biomass gas, etc., without coking and yielding stable power output. The catalyst layer is fabricated on the anode simply by catalyst support coating and reforming catalyst impregnation. The composition and microstructure of catalyst support layer as well as the catalyst composition was easily tailored to meet the demand of in situ reforming. The usage of catalyst layer as an integrated part of the traditional SOFC will provide a simple low-cost power-generating system at substantially higher fuel efficiency and faster start-ups, and may accelerate the application of SOFCs through the direct use of hydrocarbon fuels.
Article Outline
1. Introduction
2. Experimental
3. Results and discussion
3.1. Biogas and methane reforming
3.2. Propane and LPG reforming
4. Summary
References
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676
Investigation on the xylitol aqueous-phase reforming performance for pentane production over Pt/HZSM-5 and Ni/HZSM-5 catalysts Original Research Article
Applied Energy, In Press, Corrected Proof, Available online 6 May 2011
Ting Jiang, Tiejun Wang, Longlong Ma, Yuping Li, Qing Zhang, Xinghua Zhang
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Abstract
Pt/HZSM-5 and Ni/HZSM-5 catalysts were prepared and evaluated for aqueous-phase reforming (APR) reaction of xylitol. Effects of reaction temperature, pressure and metal loading on xylitol conversion and pentane selectivity were studied. Experiments over 4 wt% Pt/HZSM-5 catalysts showed that high temperature increased the xylitol conversion while high pressure led to the decrease of pentane selectivity. The xylitol conversion and pentane selectivity increased with the metal loading in the range of 0–3 wt%, but the values decreased as further increasing the metal loading to 5 wt% over both Ni/HZSM-5 and Pt/HZSM-5, indicating that higher metal loading would increase the rate of C–C bond cleavage compared to hydrogenation. Under the condition of 240 °C and 4 MPa, Ni/HZSM-5 and Pt/HZSM-5 with the same metal loading of 2 wt% showed similar xylitol conversion, while the primary had higher pentane selectivity of 95% than 58% of the latter. Ni has higher activity for pentane production than Pt during the APR reaction of xylitol, while Pt has stronger effect of C–C bond cleavage to produce lighter alkanes of C1–C4. In order to investigate catalyst recyclability, 2 wt% Ni/HZSM-5 was reused and analyzed by TG characterization. It was found that considerable amount of coke and heavy hydrocarbons were formed on the catalyst surface, which could cover the active sites and cause catalyst deactivation.
Article Outline
1. Introduction
2. Experimental
2.1. Catalyst preparation
2.2. Product analysis and catalyst characterization
2.3. Experimental methods and data processing
3. Results and discussion
3.1. Effect of reaction temperature on the xylitol APR performance
3.2. Effect of pressure on the xylitol APR performance
3.3. Effect of metal loading on the xylitol APR performance
3.4. Reaction pathways
3.5. Catalyst recyclability
4. Conclusion
Acknowledgements
References
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Highlights
► Ni/HZSM-5 and Pt/HZSM-5 catalysts for pentane production by APR processing of xylitol. ► Low hydrogen pressure and metal loading below 3wt% favor the pentane selectivity. ► Pt exhibited stronger cleaving of C-C bond than Ni for lighter alkane formation. ► Alkane selectivity was controlled by coupling of C–O cleavage, C–C cleavage and hydrogenation.
677
Evaluation of membrane reactor with hydrogen-selective membrane in methane steam reforming Original Research Article
Chemical Engineering Science, Volume 65, Issue 3, 1 February 2010, Pages 1159-1166
P. Bernardo, G. Barbieri, E. Drioli
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Abstract
A comparative analysis of a conventional industrial process and a membrane reactor plant for hydrogen production via natural gas steam reforming is proposed by calculating two sustainability metrics: mass and energy intensities. The analysis takes into account membrane reactors equipped with hydrogen-selective membranes (Pd-based) which can operate at milder temperature (500 °C) and pressure (1.0 MPa) conditions and at higher CH4 conversion levels (90–100%) than that achieved in conventional industrial systems.
The use of the MR retentate stream to produce the steam required as feed for the reforming section is proposed and for this option a reduced mass intensity is calculated (reduced amount of fuel to the process) with respect to the conventional plant. The reduction is in the range 25–32% for the MRs operated at m=3 and 44–50% for the MRs operated at m=2. A more important saving concerns the energy use.
Article Outline
1. Introduction
1.1. Systems analysed
2. Results
2.1. Mass intensity
2.2. Energy intensity
3. Conclusions
Acknowledgements
References
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678
Hydrogen generation from liquid reforming of glycerin over Ni–Co bimetallic catalyst Original Research Article
Biomass and Bioenergy, Volume 34, Issue 4, April 2010, Pages 489-495
Nianjun Luo, Kun Ouyang, Fahai Cao, Tiancun Xiao
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Abstract
Glycerin is a low cost renewable byproduct of the biodiesel industry, and can be reformed into hydrogen. Here we describe the development of cerium promoted nickel cobalt catalysts on alumina supports for the liquid phase reforming of aqueous glycerine in subcritical water. The bimetallic Ni–Co catalyst was prepared using the urea matrix combustion method over a wide range of compositions both with and without cerium. TPR profiles indicated a synergism between the metals, however, the catalysts deactivated due to carbon deposition as plaques, and in some compositions due to sintering. Cerium (2Ce–Ni1Co3) suppressed sintering and lowered methane selectivity by comparison with Ni1Co3 alone.
Article Outline
1. Introduction
2. Experimental
2.1. Samples preparation
2.2. Sample characterization
2.3. Activity evaluation
3. Results
3.1. XRD
3.2. Catalytic activity
3.2.1. Effect of Ni–Co ratios
3.2.2. Effect of cerium addition
4. Discussions
4.1. Synergic effect of nickel and cobalt
4.2. Effect of cerium addition
4.3. Deactivation studies
4.3.1. XRD
4.3.2. SEM
5. Summaries
Acknowledgements
References
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Microplasma reforming of hydrocarbons for fuel cell power
Journal of Power Sources, In Press, Corrected Proof, Available online 1 December 2010
R.S. Besser, P.J. Lindner
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Abstract
The implementation of a microplasma approach for small scale reforming processes is explored as an alternative to more standard catalyst-based processes. Plasmas are a known approach to activating a chemical reaction in place of catalysts, and microplasmas are particularly attractive owing to their extremely high electron and power densities. Their inherent compactness gives them appeal for portable applications, but their modularity leads to scalability for higher capacity. We describe the realization of experimental microplasma reactors based on the microhollow cathode discharge (MHCD) structure by silicon micromachining for device fabrication. Experiments were carried out with model hydrocarbons methane and butane in the reactors within a microfluidic flow and analytical setup. We observe several key phenomena, including the ability to liberate hydrogen from the hydrocarbons at temperatures near ambient and sub-Watt input power levels, the tendency toward hydrocarbon decomposition rather than oxidation even in the presence of oxygen, and the need for a neutral carrier to obtain conversion. Mass and energy balances on these experiments revealed conversions up to nearly 50%, but the conversion of electrical power input to chemical reaction enthalpy was only on the order of 1%. These initial, exploratory results were recorded with devices and at process s
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