Transportation fuels, compositions

Borup, R. et al., Fuel composition effects on transportation fuel cell reforming, Catal. Today, 99, 263,2005. 

Jiang Y., Virkar A.V., 2003. Fuel composition and diluent effect on gas transport and performance of anode-supported SOFCs. Journal of the Electrochemical Society 150(7), A942-A951. 

Barton, S.C. (2005) Oxygen transport in composite biocathodes. Proton Conducting Membrane Fuel Cells III, Proceedings, 2002 (31), 324—335. 

Cobalt-promoted molybdenum sulfides supported on alumina are widely used in petroleum refining for sulfur removal [1]. However, there is now increasing necessity to further improve their performance (activity, selectivity, and stability), due to more and more stringent legislation on sulfur contents in transportation fuels [2]. It is thus primordial to understand the detailed structure and catalytic behavior of these catalysts. In this respect, controlled preparation of catalysts with desired composition and structure has great importance in permitting fundamental study of structure-performance correlation. 

In this chapter a detailed CFD study of the chemical and electrochemical processes in an internally reforming anode supported SOFC button cell was carried out. Detailed models for chemistry, electrochemistry and porous media transport have been implemented into the commercial CFD code FLUENT with the help of used defined functions (UDF). Simulation results were compared with experimentally reported data. The comparisons lead to the conclusion that precise calculation of surface carbon formation is critical for the accurate prediction of OCVs for hydrocarbon fuels with very low H2O content, and that Nemst equation may not be valid for the calculation of OCV for a fuel composition such as the one considered here. Anodic overpotentials showed remarkable difference from expected behavior. 

The main difference between the AFC and PAFC is the gas-tight solid polymer electrolyte membrane, a sohd proton exchange membrane which has as its main function the transport of protons from anode to cathode. To investigate the physical and electrochemical origins of the performance loss in PEFC—operated at different conditions like high current densities, fuel composition (neat H2, H2 -1- lOOppm CO, H2O), flow rates, temperature, air or pure oxygen, etc.—electrochemical impedance studies on different PEFC systems with different electrodes and membranes were performed, as mentioned in Section 4.5.4.1. First impedance measurements and interpretation of FIS performed to characterize PEFC were reported by Srinivasan et al. [1988], Fletcher [1992], Wilson et al. [1993] and Poltarzewski et al. [1992], With increasing research and development effort to improve the PEFC performance and availability of suitable instrumentation the number of publications has increased. 

To evaluate fuel cycle risks and their composition, it is first necessary to define the fuel cycle. This will be variable in time due to changing constituents in the fuel composition as well as in the geographical location of the cycle plants and in the modes of shipment. Decisions on the proximity of waste storage sites to r rocessing plants will impact transportation risks. Plutonium recycle and spiking of reprocessed fuel can also impact the magnitude of potential accident risk. 

The compositions of transportation fuels vary widely depending on the crude oils used, the refining process, the product demand, and the product specifications. The approximate compositions of gasoline, diesel, and jet fuel are given in Table 10.12. Branched and n-alkanes are the main ingredients of these fuels, typically 70-80%. The major alkane is n-hexane and the main branched alkanes are C5 and Ce compounds. The aromatics are mainly benzene, toluene, xylenes, and alkyl benzenes, totaling about 20-30%. 

Purification of H2 as an intermediate or final product is a pivotal process that cuts across the transportation fuels and chemical sectors. Over the past few decades, tremendous progress has been made in the development of selective polymeric, ceramic, metal, and composite membranes for H2 separation. Of particular interest has been development of highly permselective membrane systems to enable efficient, economic, and environmentally responsible production of power within the context of advanced gasification processes that employ combustion turbines and solid oxide fuel cells. 

Fig. 1.2 provides evidence that multiphase catalytic reactors are present across a spectrum of process technologies. They constitute over 98% of reactors employed in practical processes and are employed in numerous industrial sectors, such as processes for manufacture of advanced materials (e.g., composites, nanomaterials, optical fibers, plastics, and semiconductors), bio-based materials, bulk chemicals, catalysts, environmental remediation, fine and specialty chemicals, pharmaceuticals, plastics, polymers, natural gas derivatives, petroleum-refined products, and transportation fuels. These products represent a large contribution to the GDP in both the United States and elsewhere in the world (Tunca et al., 2006). 

There are three major types of transportation fuels gasoline, diesel and jet fuels that differ in composition and properties. The common types of sulfin compounds in liquid fuels are listed below. 

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