Chunshan Song

Fuel processing for low-temperature and high-temperature fuel cells - Challenges, and opportunities for sustainable development in the 21st century

Abstract This review paper first discusses the needs for fundamental changes in the energy system for major efficiency improvements in terms of global resource limitation and sustainable development. Major improvement in energy efficiency of electric power plants and transportation vehicles is needed to enable the world to meet the energy demands at lower rate of energy consumption with corresponding reduction in pollutant and CO2 emissions. A brief overview will then be given on principle and advantages of different types of low-temperature and high-temperature fuel cells. Fuel cells are intrinsically much more energy-efficient, and could achieve as high as 70–80% system efficiency (including heat utilization) in electric power plants using solid oxide fuel cells (SOFC, versus the current efficiency of 30–37% via combustion), and 40–50% efficiency for transportation using proton-exchange membrane fuel cells (PEMFC) or solid oxide fuel cells (versus the current efficiency of 20–35% with internal combustion (IC) engines). The technical discussions will focus on fuel processing for fuel cell applications in the 21st century. The strategies and options of fuel processors depend on the type of fuel cells and applications. Among the low-temperature fuel cells, proton-exchange membrane fuel cells require H2 as the fuel and thus nearly CO-free and sulfur-free gas feed must be produced from fuel processor. High-temperature fuel cells such as solid oxide fuel cells can use both CO and H2 as fuel, and thus fuel processing can be achieved in less steps. Hydrocarbon fuels and alcohol fuels can both be used as fuels for reforming on-site or on-board. Alcohol fuels have the advantages of being ultra-clean and sulfur-free and can be reformed at lower temperatures, but hydrocarbon fuels have the advantages of existing infrastructure of production and distribution and higher energy density. Further research and development on fuel processing are necessary for improved energy efficiency and reduced size of fuel processor. More effective ways for on-site or on-board deep removal of sulfur before and after fuel reforming, and more energy-efficient and stable catalysts and processes for reforming hydrocarbon fuels are necessary for both high-temperature and low-temperature fuel cells. In addition, more active and robust (non-pyrophoric) catalysts for water–gas-shift (WGS) reactions, more selective and active catalysts for preferential CO oxidation at lower temperature, more CO-tolerant anode catalysts would contribute significantly to development and implementation of low-temperature fuel cells, particularly proton-exchange membrane fuel cells. In addition, more work is required in the area of electrode catalysis and high-temperature membrane development related to fuel processing including tolerance to certain components in reformate, especially CO and sulfur species.

Preparation and characterization of novel CO2 "molecular basket" adsorbents based on polymer-modified mesoporous molecular sieve MCM-41

Abstract Novel CO2 “molecular basket” adsorbents were prepared by synthesizing and modifying the mesoporous molecular sieve of MCM-41 type with polyethylenimine (PEI). The MCM-41-PEI adsorbents were characterized by X-ray powder diffraction (XRD), N2 adsorption/desorption, thermal gravimetric analysis (TGA) as well as the CO2 adsorption/desorption performance. This paper reports on the effects of preparation conditions (PEI loadings, preparation methods, PEI loading procedures, types of solvents, solvent/MCM-41 ratios, addition of additive, and Si/Al ratios of MCM-41) on the CO2 adsorption/desorption performance of MCM-41-PEI. With the increase in PEI loading, the surface area, pore size and pore volume of the PEI-loaded MCM-41 adsorbent decreased. When the PEI loading was higher than 30 wt.%, the mesoporous pores began to be filled with PEI and the mesoporous molecular sieve MCM-41 showed a synergetic effect on the adsorption of CO2 by PEI. At PEI loading of 50 wt.% in MCM-41-PEI, the highest CO2 adsorption capacity of 246 mg/g-PEI was obtained, which is 30 times higher than that of the MCM-41 and is about 2.3 times that of the pure PEI. Impregnation was found to be a better method for the preparation of MCM-41-PEI adsorbents than mechanical mixing method. The adsorbent prepared by a one-step impregnation method had a higher CO2 adsorption capacity than that of prepared by a two-step impregnation method. The higher the Si/Al ratio of MCM-41 or the solvent/MCM-41 ratio, the higher the CO2 adsorption capacity. Using polyethylene glycol as additive into the MCM-41-PEI adsorbent increased not only the CO2 adsorption capacity, but also the rates of CO2 adsorption/desorption. A simple model was proposed to account for the synergetic effect of MCM-41 on the adsorption of CO2 by PEI.

A New Approach to Deep Desulfurization of Gasoline, Diesel Fuel and Jet Fuel by Selective Adsorption for Ultra-clean Fuels and for Fuel Cell Applications

In order to further reduce the sulfur content in liquid hydrocarbon fuels (gasoline, diesel fuel and jet fuel) for producing ultra-clean transportation fuels and for fuel cell applications, we explored a new desulfurization process by selective adsorption for removing sulfur (SARS). An adsorbent was developed and used for adsorption desulfurization of diesel fuel, gasoline and jet fuel at room temperature. The results indicate that the transition metal-based adsorbent developed in this work is effective for selectively adsorbing the sulfur compounds, even the refractory sulfur compounds in diesel fuels. The SARS process can effectively remove sulfur compounds in the liquid hydrocarbon fuels at ambient temperature under atmospheric pressure with low investment and operating cost. On the basis of the present study, a novel integrated process is proposed for deep desulfurization of the liquid hydrocarbon fuels in a future refinery, which combines a selective adsorption (SARS) of the sulfur compounds and a hydrodesulfurization process of the concentrated sulfur fraction (HDSCS). The SARS concept may be used for on-site or on-board removal of sulfur from fuels for fuel cell systems.

Chemicals and materials from coal in the 21st century

Coal may become more important both as an energy source and as the source of organic chemical feedstock in the 21st century. The demonstrated coal reserves in the world are enough for consumption for over 215 years at the 1998 level, while the known oil reserves are only about 39 times of the worlds consumption level in 1998 and the known natural gas reserves are about 63 times of the worlds consumption level in 1998. Coal has several positive attributes when considered as a feedstock for aromatic chemicals, specialty chemicals, and carbon-based materials. Substantial progress in advanced polymer materials, incorporating aromatic and polyaromatic units in their main chains, has created new opportunities for developing value-added or specialty organic chemicals from coal and tars from coal carbonization for coke making. The decline of the coal tar industry diminishes traditional sources of these chemicals. The new coal chemistry for chemicals and materials from coal may involve direct and indirect coal conversion strategies as well as the co-production approach. Needs for environmental-protection applications have also expanded market demand for carbon materials. Current status and future directions are discussed in this review.

Synthesis of mesoporous molecular sieves : influence of aluminum source on Al incorporation in MCM-41

Three series of mesoporous aluminosilicate molecular sieves, MCM-41, with various Si/Al ratios were synthesized using different aluminum sources (aluminum isopropoxide, pseudo boehmite and aluminum sulfate). XRD analysis, temperature programmed desorption ofn-butylamine,27Al and29Si MAS NMR, and catalytic alkylation test indicated that aluminum isopropoxide is a better source for incorporating aluminum in the framework of MCM-41 type molecular sieves with better crystallinity and acid characteristics.

Clean liquid fuels from direct coal liquefaction: chemistry, catalysis, technological status and challenges

Increased demand for liquid transportation fuels coupled with gradual depletion of oil reserves and volatile petroleum prices have recently renewed interest in coal-to-liquids (CTL) technologies. Large recoverable global coal reserves can provide liquid fuels and significantly reduce dependence on oil imports. Direct coal liquefaction (DCL) converts solid coal (H/C ratio ≈ 0.8) to liquid fuels (H/C ratio ≈ 2) by adding hydrogen at high temperature and pressures in the presence or absence of catalyst. This review provides a comprehensive literature survey of the coal structure, chemistry and catalysis involved in direct liquefaction of coal. This report also touches briefly on the historical development and current status of DCL technologies. Key issues, challenges involved in DCL process and directions for the future research are also addressed.

Synthesis of mesoporous zeolites and their application for catalytic conversion of polycyclic aromatic hydrocarbons

Abstract Three series of mesoporous aluminosilicate (Al-MCM-41) samples were synthesized using different aluminum sources including aluminum isopropoxide, pseudo boehmite and aluminum sulfate. Their catalytic activities were tested in the conversion of aromatic hydrocarbons including hydrocracking of 1,3,5-triisopropylbenzene, alkylation of naphthalene, and hydrogenation of naphthalene and phenanthrene. The three series of Al-MCM-41 samples behaved differently in acting as acidic catalysts and as supports. The Al-MCM-41 synthesized using aluminum isopropoxide was found to be the most promising acidic catalyst and good support for Pt catalyst.

Environmental challenges and greenhouse gas control for fossil fuel utilization in the 21st century

Contents. Acknowledgements. Preface. Part 1: Pollutant Emissions. Analysis of Multiple Emission Strategies in Energy Markets J.A. Beamon, R.T. Eynon. Mercury in Illinois Coats: Abundance, Forms, and Environmental Effects I. Demir. Characterization of Particulate Matter with Computer-Controlled Scanning Electron Microscopy S.A. Benson, et al. Dioxin and Furan Formation in FBC Boilers L. Jia, et al. Reducing Emissions of Polyaromatic Hydrocarbons from Coal Tar Pitches J.M. Andresen, et al. Part 2: Carbon Sequestration. Carbon Sequestration: An Option for Mitigating Global Climate Change R.L. Kane, D.E. Klein. Using a Life Cycle Approach in Analyzing the Net Energy and Global Warming Potential of Power Production via Fossil Fuels with C02 Sequestration Compared to Biomass P.L. Spath. Carbon Storage and Sequestration as Mineral Carbonates D.J. Fauth, et al. Sequestration of Carbon Dioxide by Ocean Fertilization M. Markels, et al. Polyelectrolyte Cages for a Novel Biomimetic CO2 Sequestration System F.A. Simsek-Ege, et al. Novel Solid Sorbents for Carbon Dioxide Capture Y. Soong et al. Part 3: Greenhouse Gas Emissions Control. Near Zero Emission Power Plants as Future CO2 Control Technologies P. Mathieu. Reducing Greenhouse Emissions from Lignite Power Generation by Improving Current Drying Technologies G. Favas, et al. Reduction Process Of CO2 Emissions by Treating With Waste Concrete via an Artificial Weathering Process A. Yamasaki, et al. Understanding Brown Coal-Water Interaction to Reduce Carbon Dioxide Emissions L.M. Clemow, et al. High Temperature Combustion of Methane over Thermally Stable CoO-MgO Catalyst for Controlling MethaneEmissions from Oil/Gas-Fired Furnaces V.R. Choudhary, et al. Dual-Bed Catalytic System for Removal of NOx-N2O in Lean-Burn Engine Exhausts A.R. Vaccaro, et al. Part 4: Utilization of CO2 of CO2 for Synthesis Gas Production. Tri-reforming of Natural Gas Using CO2 in Flue Gas of Power Plants without CO2 Pre-separation for Production of Synthesis Gas with Desired H2O/CO Ratios C. Song, et al. Effect of Pressure on Catalyst Activity and Carbon Deposition During CO2 Reforming of Methane over Noble-Metal Catalysts A. Shamsi, C.D. Johnson. CO2 Reforming of CH4 to Syngas over Ni Supported on Nano-g-Al2O3 Jun Mei Wei, et al. Oxy-CO2 Reforming and Oxy-CO2 Steam Reforming of Methane to Syngas over CoxNi1-xO/MgO/SA-5205 V.R. Choudhary, et al. Carbon Routes In Carbon Dioxide Reforming of Methane L. Pinaeva, et al. Part 5: Utilization of CO2 for chemical synthesis. Life Cycle Assessment (LCA) applied to the synthesis of methanol. Comparison of the use of syngas with the use of CO2 and dihydrogen produced from renewables M. Aresta, et al. Reduction of CO2 in Steam Using a Photocatalytic Process to Form Formic Acid D.D. Link, C.E. Taylor. Carbon Dioxide as a Soft Oxidant: Dehydrogenation of Ethylbenzene Into Styrene S.-E. Park, et al. CO2 as a C1-Building Block for Dialkyl Carbonate Synthesis D. Ballivet-Tkatchenko. Part 6: Combustion Byproducts. An Investigation of the Characteristics of Unburned Carbon in Oil Fly Ash Y.-M. Hsieh, M.-S. Tsai. Separation of Fly Ash Carbons

Opportunities for developing specialty chemicals and advanced materials from coals

The main objective of this paper is to explore the potentials and possible ways to develop high-value chemicals and materials from coals and coal liquids. Recently it has become clear that more extensive use of fossil fuels, especially coal, may be constrained not only by economics, but also by environmental considerations such as SOx and NOx emissions and global warming. Therefore, new concepts are required, and significant advances are essential for the effective utilization of coals in the next century. Both from economic and environmental viewpoints, developing high-value chemicals and materials from coals and coal liquids should lead to more efficient and environmentally safe utilization of the valuable carbonaceous resources. It is important to explore the routes and methods for developing specialty chemicals, which are difficult to obtain or not readily available from petroleum, advanced polymeric engineering materials, and high-performance carbon materials. Recent years have seen significant progress in the development and application of new, industrially important aromatic engineering plastics, thermoplastic materials, liquid crystalline polymers, and membrane materials. Many of the monomers for these materials can be prepared from one- to four-ring aromatics such as alkylated benzenes, naphthalene, biphenyl, anthracene, phenanthrene, pyrene, phenol, and carbazole. Especially important are 2,6-dialkylnaphthalenes, 4,4′-dialkylbiphenyls, and 1,4-dialkylbenzenes. The large-volume application of aromatic high-performance polymers depends on lowering their cost, which in turn is largely determined by the cost of the aromatic monomers. By developing the critical aromatic chemicals from coals, coal-to-chemicals research could contribute significantly to high-technology development. Potential large-volume markets for materials from coal can be stimulated by developing high-performance carbon materials such as carbon fibers and graphites, and by developing ways to make advanced adsorbents for environmental applications such as air and water purification.

Influence of nitrogen compounds on deep hydrodesulfurization of 4,6-dimethyldibenzothiophene over Al2O3- and MCM-41-supported Co-Mo sulfide catalysts

Abstract The present work focuses on the effect of nitrogen compounds on the activity of MCM-41- and γ-Al 2 O 3 -supported Co-Mo catalysts for the deep hydrodesulfurization of 4,6-dimethyldibenzothiophene (4,6-DMDBT) in a fixed-bed flow reactor. Sulfur removal to the depths required by new specifications will require knowledge of the influence of non-sulfur diesel fuel components on deep hydrodesulfurization. The main objective of this paper is to examine the activity of hydrodesulfurization catalysts during and, most importantly, after exposure to basic and non-basic nitrogen. Quinoline (basic nitrogen) inhibits catalytic activity of both γ-Al 2 O 3 - and MCM-41-supported catalysts. It strongly inhibits hydrogenation and hydrogenolysis activity as evidenced by decreased selectivity for cyclohexylbenzene and biphenyl derivatives, respectively. To a certain extent, the long-term effects of quinoline are reversible. Carbazole (non-basic nitrogen) has little effect on the γ-Al 2 O 3 -supported Co-Mo catalyst but significantly inhibits the activity of the MCM-41-supported Co-Mo catalyst. The inhibition of the MCM-41-supported catalyst is reversible following removal of carbazole from the feedstock. Molecular modeling was also conducted to derive the bond order and electron charges of the nitrogen and sulfur compounds, which are helpful to understanding the experimental results.