Fuel perspectives

The use of a Fischer-Tropsch (FT) process to produce long-chain hydrocarbons is well known in industry, and achieving the desired selectivity from the FT reaction is crucial for the process to make economic sense. It is, however, well known that a one-alpha model does not describe the product spectrum well. From either a chemicals or fuels perspective, hydrocarbon selectivity in the FT process needs to be thoroughly understood in order to manipulate process conditions and allow the optimization of the required product yield to maximize the plant profitability. There are many unanswered questions regarding the selectivity of the iron-based low-temperature Fischer-Tropsch (Fe-LTFT) synthesis. 

Sulfur. Sulfur in diesel fuel should be kept below set limits for both environmental and operational reasons. Operationally, high levels of sulfur can lead to high levels of corrosion and engine wear owing to emissions of SO that can react with condensed water during start-up to form sulfuric acids. From an environmental perspective, sulfur bums to SO2 and SO, the exact spHt being a function of temperature and time in the combustion chamber. 

Since 1976, these forms of acids have become a significant environmental concern from both a physical handling and disposal perspective. This concern has fueled much development work toward soHd acid catalysts, including zeoHtes, siHca —aluminas, and clays (107,108). 

A fuel closely related to gasoline is naphtha, which is also a potential fuel cell fuel. Naphtha is already produced in large quantities at refineries and is a cheaper fuel than gasoline, which must have octaneboosting additives blended into it. Unlike methanol, naphtha can be distributed in the same pipelines as gasoline. From the fuel cell s perspective, it has a higher H C ratio and lower sulfur and aromatics content than gasoline. 

BB-SFG, we have investigated CO adsorption on smooth polycrystaHine and singlecrystal electrodes that could be considered model surfaces to those apphed in fuel cell research and development. Representative data are shown in Fig. 12.16 the Pt nanoparticles were about 7 nm of Pt black, and were immobilized on a smooth Au disk. The electrolyte was CO-saturated 0.1 M H2SO4, and the potential was scanned from 0.19 V up to 0.64 V at 1 mV/s. The BB-SFG spectra (Fig. 12.16a) at about 2085 cm at 0.19 V correspond to atop CO [Arenz et al., 2005], with a Stark tuning slope of about 24 cm / V (Fig. 12.16b). Note that the Stark slope is lower than that obtained with Pt(l 11) (Fig. 12.9), for reasons to be further investigated. The shoulder near 2120 cm is associated with CO adsorbed on the Au sites [Bhzanac et al., 2004], and the broad background (seen clearly at 0.64 V) is from nomesonant SFG. The data shown in Figs. 12.4, 12.1 la, and 12.16 represent a hnk between smooth and nanostructure catalyst surfaces, and will be of use in our further studies of fuel cell catalysts in the BB-SFG IR perspective. 

Final Report (2003) Refuse derived fuel, current practice and perspectives. European Commission, p 51... 

We believe that new type of conducting polymer / expanded graphite composite electrodes as gas-diffusion cathodes will find in perspective a practical application for some types of batteries and fuel cells. 

It is useful to put in perspective the range of temperature conditions during the combustion of a liquid fuel. In increasing order ... 

Pleil, J.D., Smith, L.B., and Zelnick, S.D., Personal exposure to JP-8 jet fuel vapors and exhaust at air force bases, Environ. Health Perspect., 108, 183, 2000. 

From the perspective of greenhouse gases, electrolysis is unsettled for the foreseeable future since both electrolysis and central-station power generation are relatively inefficient processes and most U.S. electricity is generated by the burning of fossil fuels. Nuclear and renewables make up only about 1 / 3 of total generation. 

However, it has to be noted that, from the perspective of providing mobility, by using that natural gas as feedstock -and taking into account fuel production and vehicle conversion efficiencies - the majority of passenger cars can be fuelled with the production of liquid fuels from oil sands, followed (with about a factor of three less) by its conversion into hydrogen and subsequent use in fuel-cell vehicles, and its direct use in CNG vehicles. 

Among liquid fuels (XTL), only biomass-derived hydrocarbons (BTL) are a relevant option from the perspective of lowering GHG emissions not so other fossil-based liquids (CTL, GTL). Even if CTL fuel supply paths were upgraded by carbon capture and storage, the resulting specific CCF-equivalent emissions would only be reduced to the level of conventional gasoline or diesel energy chains. 

In 2003, the European Biofuels Directive (CEU, 2007 EC, 2003) was enacted. It sets an indicative target of a 2% market share for biofuels in 2005, a 5.75% share in 2010 and a 10% share in 2020 for road transport related to the energy content of the fuel. It has to be noted, however, that biofuel mandates are increasingly being scrutinised from a sustainability perspective and the targets in the EU are currently being reconsidered. 

Krewitt, W., Nitsch, J., Fischedick, M., Pehnt, M. and Temming, H. (2006). Market perspectives of stationary fuel cells in a sustainable energy supply system - longterm scenarios for Germany. Energy Policy, 34 (2006), 793-803. 

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