Fuels, Synthetic, Liquid Fuels

Abstract

The creation of liquids to be used as fuels from sources other than natural crude petroleum broadly defines synthetic liquid fuels. Synthetic liquid fuels have characteristics approaching those of the liquid fuels in commerce, specifically gasoline, kerosene, jet fuel, and fuel oil. For much of the twentieth century, the synthetic fuels emphasis was on liquid products derived from coal upgrading or by extraction or hydrogenation of organic matter in coke liquids, coal tars, tar sands, or bitumen deposits. However, much of the direction involving synthetic fuels technology has changed. The potential of natural gas, which typically has 85–95% methane, has been recognized as a plentiful and clean alternative feedstock to crude oil. The proven technology to upgrade methane is via steam reforming to produce synthesis gas, CO + H 2 . Such a gas mixture is clean and when converted to liquids produces fuels substantially free of heteroatoms such as sulfur and nitrogen. Two commercial units utilizing the synthesis gas from natural gas technology in combination with novel downstream conversion processes have been commercialized. The direct methane conversion technology has received the most research attention and involves the oxidative coupling of methane to produce higher hydrocarbons such as ethylene. A second trend in synthetic fuels is increased attention to oxygenates as alternative fuels as a result of the growing environmental concern about burning fossil‐based fuels. The environmental impact of the oxygenates is still under debate, but these alternative liquid fuels are gaining new prominence. Despite reduced prominence, coal technology is well positioned to provide synthetic fuels for the future. World petroleum and natural gas production are expected ultimately to level off and then decline. Coal gasification to synthesis gas is utilized to synthesize liquid fuels in much the same manner as natural gas steam reforming technology. Although world activity in coal liquefaction technology is minimal, the extensive development and detailed demonstration of processes for converting coal to liquid fuels should serve as solid foundation for the synthetic fuel needs of the future. Coal, tar, and heavy oil fuel reserves are widely distributed. The importance of coal gasification as a means of producing fuel gas(es) for industrial use cannot be underplayed. But coal gasification systems also have undesirable features. A range of undesirable products are also produced which must be removed before the products are used to provide fuel and/or to generate electric power. Natural gas is a plentiful resource, and there has been a marked tendency not to use other fossil fuels as SNG sources. However, petroleum oil shale, and biomass have been the subject of extensive research efforts.

Potential routes for thermochemical biorefineries

“…Details of process design and plant economics are given elsewhere. 164,165,171 Technoeconomic assessments on gasoline production from lignocellulosic biomass have been recently published. 21,170,172,173 Methanol/DME to olefi ns Th e methanol/DME to olefi ns (ethylene and propylene) route was developed simultaneously with the methanol/ DME to gasoline route and both routes have important similarities.…”

Single-Step Syngas-to-Distillates (S2D) Synthesis via Methanol and Dimethyl Ether Intermediates: Final Report

“…However, Pd/ZnO is inactive for the dehydration of methanol to DME [19,20]. Therefore, it is reasonable to assume that for the Pd/ZnO/Al 2 Table 3.2), the coverage of the Al 2 O 3 support increases, and the number of accessible acid sites decreases. Note that there is a correlation between the DME selectivity and the amount of acid sites.…”

“…Selectivities, however, do not vary significantly. Selectivity to hydrocarbons, CO 2 , and oxygenates range from 77 to 71%, 17 to 21%, and 6-8%, respectively. Of the C 5 + hydrocarbons produced, there is an increase in CH 4 production, and a corresponding decrease in C 2 -C 4 production, when increasing the GHSV from 1490 to 2970 hr -1 .…”

“…The major hydrocarbons selectivity has been listed in D.3 Table 2.3. Based on the experimental results, the product distillate mainly contains light gases (CO, CO 2 , and H 2 ); light hydrocarbons (C 1 -C 4 ); straight chain paraffins, branched alkanes, naphthenes, and alkyl benzenes (C 5 -C 9 ); and heavy components, mainly C 10 to C 12 aromatics. Over 40 components are used to simulate the distillate product from the S2D process.…”

“…The products follow an Anderson-Schulz-Flory distribution, and post processing is required to maximize the desired fraction. Overall, the FT process suffers from low operating efficiencies and has not realized significant market share despite much development work in this area [2].…”