Fischer diesel

Shell Gas B.V. has constructed a 1987 mVd (12,500 bbhd) Fischer-Tropsch plant in Malaysia, start-up occurring in 1994. The Shell Middle Distillate Synthesis (SMDS) process, as it is called, uses natural gas as the feedstock to fixed-bed reactors containing cobalt-based cat- yst. The heavy hydrocarbons from the Fischer-Tropsch reactors are converted to distillate fuels by hydrocracking and hydroisomerization. The quality of the products is very high, the diesel fuel having a cetane number in excess of 75. 

The major advantage of Fischer Tropsch diesel, compared to natural gas, lies in its liquid nature. It does not need special infrastructure and compression like CNG does, and unlike LNG, once converted, it is a liquid fuel that can be treated like any other liquid fuel. However, because the GTL process is more complex than traditional refining, it requires low-cost natural gas priced at less than 1 per million BTUs to remain cost-competitive. Without stranded gas, sources sold at a large discount compared to crude oil, GTL diesel would be considerably more expensive than traditionally refined diesel fuel. 

Fischer Tropsch technology is best exemplified by the SASOL projects in South Africa. After coal is gasified to a synthesis gas mixture, it is purified in a rectisol unit. The purified gas mixture is reacted in a synthol unit over an iron-based catalyst. The main products are gasoline, diesel fuel, and jet fuels. By-products are ethylene, propylene, alpha olefins, sulfur, phenol, and ammonia which are used for the production of downstream chemicals. 

The Fischer-Tropsch process has attracted renewed interest as a way to produce high quality, sulfur-free diesel fuel from natural gas and, possibly, an opportunity to utilize natural gas at remote oilfields. The process represents proven technology and is regarded as an alternative for when oil may no longer be widely available, and one has to resort to natural gas and coal. In a really futuristic scenario one may even contemplate the use of GO and H2 produced by photo-catalytic dissociation of GO2 and water. 

The fact that Fischer-Tropsch fuels contain neither sulfur nor aromatics may become a strong selling point for the process. Less sulfur in the fuel has, of course, a direct effect on the sulfur oxides in the emissions, and the newly developed exhaust purification systems for lean burning engines that can be introduced means that all emissions, including GO2 and NOx, will diminish. Aromatics promote particulate formation in the combustion of diesel fuels and are therefore undesirable. We discuss this further in Ghapter 10. 

Figure 8.17. Hydrocarbon distribution of the products formed by Fischer-Tropsch synthesis over cobalt-based catalysts and by additional hydrocracking, illustrating how a two-stage concept enables optimization of diesel fuel yield. [Adapted from S.T. Sie,...

Ohtsuka, Y., Arai, T., Takasaki, S., and Tsubouchi, N. 2003. Fischer-Tropsch synthesis with cobalt catalysts supported on mesoporous silica for efficient production of diesel fuel fraction. Energy Fuels 17 804-9. 

Diesel production involved a straightforward design. The olefinic distillate from olefin oligomerization was combined with the straight-run HTFT distillate and hydrotreated. The hydrotreated Fischer-Tropsch-derived distillate was blended with the distillate fraction from the natural gas liquids to produce diesel fuel. In 2003 another hydrotreater (noble metal catalyst) was added to the refinery to convert part of the hydrotreated HTFT distillate into low aromatic distillate to serve a niche market.56... 

Another option to extend the ligno-cellulosic feedstock base is the development of BTL through biomass gasification and subsequent Fischer-Tropsch synthesis. Although BTL is fully compatible with diesel fuel, ligno-cellulosic BTL has not yet been commercialised. 

Diesel (Cu-Cie) Fatty acid esters (methyl = FAME, ethyl = FAEE) Levulinic acid esters (methyl, ethyl) DME Ethanol Fischer-Tropsch diesel (from bio-based synthesis gas) Deoxygenated and refined primary bioliquids... 

Depending on the reason for converting the produced gas from biomass gasification into synthesis gas, for applications requiring different H2/CO ratios, the reformed gas may be ducted to the water-gas shift (WGS, Reaction 4) and preferential oxidation (PROX, Reaction 5) unit to obtain the H2 purity required for fuel cells, or directly to applications requiring a H2/CO ratio close to 2, i.e., the production of dimethyl ether (DME), methanol, Fischer-Tropsch (F-T) Diesel (Reaction 6) (Fig. 7.6). 

Diesel B, Seifert M, Radermacher J, Fischer U, Tilgen W, et al. 2004. Towards a complete picture of splice variants of the gene for 25-hydroxyvitamin D31alpha-hydroxylase in brain and skin cancer. J Steroid Biochem Mol Biol 89-90 ... 

Second generation biofuels Non-food crops, wheat straw, com, wood, solid waste, energy crop Bioalcohols, bio-oil, bio-DMF, Biohydrogen, bio-Fischer-Tropsch diesel, wood diesel... 

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