Synthetic and Alternative Fuels

Since that time, a variety of alternatives to refined petroleum products have been evaluated and used as fuels for internal combustion engines. Reasons for considering synthetic and alternative fuels stem from two primary motivating factors the need to ensure an adequate supply of low-cost fuel, and the desire to use fuel that bums completely and cleanly without undesirable exhaust emissions. 

The terms synthetic fuel and alternative fuel are closely related, but not truly synonymous. Synthetic fuel was coined as a term in the middle of the twentieth century to include gaseous, liquid and solid fuels produced from coal, oil shale, tar sands, and biomass. Alternative fuel appeared as a popular phrase during the latter years of the twentieth century which referred to fuels that were not totally based on petroleum and held potential as clean-burning, low-polluting, commercially viable fuel resources. 

Coal is a rich source of carbon and has been a valuable source of fuel for centuries. It is classified by both coal type and coal rank. Coal type is determined by the nature of the original biomass that led to the formation of the coal. Coal rank signifies the degree of maturation or chemical change in coal and usually determines coal quality. The calorific value, moisture content, elemental analysis, volatile matter, ash, and fixed carbon content are important qualities of coal. 

The carbon in coal can exist in two forms, volatile carbon and base carbon. Volatile carbon is released by pyrolysis while base carbon remains as a residual char or coke. Both forms of carbon in coal have been utilized in the development of synthetic fuel. 

In 1792, Murdoch, a Scottish engineer, distilled coal in an iron oven and used the coal gas to fuel lamps in his home. This discovery led to the development of the coal gas industry, and by 1812, distilled coal gas was being used to fuel street lamps in London. Use of distilled coal gas quickly spread throughout Europe and remained an important source of domestic and industrial heating and lighting into the early twentieth century. 

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To keep pace with advances and changes in the fuel industry, a new chapter has been added. The chapter is titled Synthetic and Alternative Fuels. Contained within this chapter is a review of information about the processing, properties, and performance of synthetic and alternative fuels. Pertinent background information is presented to account for the tremendous amount of work that led to the development of the present-day synthetic and alternative fuel industry. A brief summary of the handling and performance characteristics associated with various alternative fuels provides useful information about the fuels, their strengths, and their shortcomings. 

Alternative fuels fall into two general categories. The first class consists of fuels that are made from sources other than cmde oil but that have properties the same as or similar to conventional motor fuels. In this category are fuels made from coal and shale (see Fuels, synthetic). In the second category are fuels that are different from gasoline and diesel fuel and which require redesigned or modified engines. These include methanol (see Alcohol fuels), compressed natural gas (CNG), and Hquefted petroleum gas (LPG). 

Today ethanol and biodiesel (FAME) are the most common biofuels. Alternative fuels from fossil energy sources are mainly LPG and CNG. Synthetic gasoline and diesel from coal (CTL) and natural gas (GTL) are produced mainly in South Africa. Electricity used in battery-electric vehicles plays a minor role today. The fuel consumption for road transport in the world today amounts to about 65 700 PJ per year (IEA, 2006a) in total, the share of alternative fuels for transport at the time of writing was about 2.7% (Table 7.24). 

The alternative fuels and drive systems available only seem to be viable on the mass market, if the oil price stays above 60 to 70 /bbl for a sustained period. Oil prices peaked above 140 /bbl in summer 2008 and many experts believe that stable oil prices over 100 /bbl could be reached in the next one or two decades. The higher the market prices of fossil fuels, the more competitive low-carbon alternatives will become The principal choice here is between biofuels, electricity and hydrogen, provided that they are produced either from low/zero-carbon feedstock or that the C02 generated during their production is captured and stored. But higher priced conventional oil resources, on the other hand, can also be replaced by high-carbon alternatives such as oil sands, oil shale or synthetic fuels from coal and gas. 

These are the touchstones for all alternative fuels, which - along with hydrogen -include biofuels, compressed natural gas (CNG), and synthetic liquid fuels derived from natural gas (NG) and coal. Although this chapter focuses on hydrogen, it is relevant to recognize that this whole spectrum of future fuels will in the de-... 

Alkyl-substituted monoamides are known as extractants for the uranyl cation and they could potentially be considered as alternatives to organophosphorus compounds in nuclear fuel reprocessing. In toluene, the uranyl cation forms complexes with two monoamide molecules. These relatively simple molecules were selected for computer-aided design,14 taking into account a lot of synthetic and experimental work that must be done to prove the modeling predictions. 

Besides gasoline, methanol is the most promising alternative fuel. Unfortunately, there are only a few industrial units all over the world that process natural gas to motor fuels based on its preliminary conversion to synthetic gas. This is a multistage, power-consuming process, which requires high pressure and temperature, expensive catalysts, etc. 

The concept of this process is shown in Figure 6. The carbon in biomass which is fixed by photosynthesis from atmospheric C02 is converted into i) solid carbon (various kinds of charcoal, carbon and graphite) for use as materials or for storage, which is a stable state of carbon element ii) synthetic fuels such as FT diesel oil, DME or hydrogen, which can replace fossil fuels as carbon neutral alternate fuels (Hori, 2007, 2007a, 2007b). 

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