Processing of Primary Fischer-Tropsch Products - University of Alberta

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from the LTFT material. As implied above, some aromatic content is desirable to increase the diesel density. Future diesel specifications focus mainly on sulphur reduction, with the sulphur content likely to be limited to 10 ppm. Moving from Euro-2 to Euro-4 specifications also require increased Cetane number (> 51), lower T95 boiling point (i.e. 95% volume recovered at
490 cannot be used with FT products, but rather that these technologies neither have a specific refining advantage nor address a specific shortcoming. In some instances application of these technologies provides excellent refining opportunities. By looking at the HTFT product on a carbon number for carbon number basis, these opportunities will be highlighted. The focus of this discussion remains on fuels refining, although opportunities for chemical extraction are briefly discussed where applicable. The carbon numbers discussed actually refer to the boiling range of the equivalent hydrocarbons in the FT primary product. Most oxygenates have higher boiling points than their hydrocarbon analogues. Within the same boiling range, oxygenates will have three to four carbon atoms less than the hydrocarbons. For example, hexanol will be relevant to the discussion of C9/C~0 hydrocarbons and will not be discussed with the C6 hydrocarbons. 3.2.1 C3 hydrocarbons Propylene is the most abundant HTFT product. When purified, it can be used for chemicals and polymer production. However, the level of propylene recovery is limited by economic considerations and the refinery has to deal with propylene in a propane-rich mixture. Direct marketing as liquid petroleum gas (LPG) is not always possible and the preferred refining options are" 9 Alkylation: the process involving benzene and propylene to produce cumene is a well-established one that is fairly insensitive to the propane content in the feed. The reaction takes place over an acidic catalyst, like solid phosphoric acid or a zeolite. Cumene has a high octane value (RON-113 and MON-99) and has value as a chemical commodity too. This is an excellent way to improve octane, increase fuel density and move propylene into the fuel boiling range. Aliphatic alkylation of iso-butane with propylene is possible, but will typically not be considered. FT material is not only low in iso-butane, but propylene also gives a poor quality alkylate when compared to 2-butene which is the industry standard (5-8 octane units difference) [32]. 9 Aromatisation" The aromatisation of C3 hydrocarbons to give a high octane aromatic product has the advantage that it converts both propane and propylene. A number of commercial technologies exist, most being based on metal promoted ZSM-5 catalysts. The liquid product yield (C5 and heavier) is typically in the order of 60-70%. It is therefore a good way to improve octane, increase density and move C3 hydrocarbons into the fuel boiling range. It is especially beneficial for propylene lean streams, when olefin- based technologies like oligomerisation and alkylation would be able to upgrade only a small part of the C3-fraction. 9 Oligomerisation: Propylene can be converted by homogeneous or heterogeneously catalysed processes to heavier hydrocarbons. Zeolites, solid phosphoric acid and amorphous silica-alumina based catalysts are in use
Page 1 and 2: Studies in Surface Science and Cata
Page 3 and 4: 484 Cold separation .~~"~ Condensat
Page 5 and 6: 486 Chemical production at the Moss
Page 7: 488 Table 1 Research octane value (
Page 11 and 12: 492 an attractive refining option f
Page 13 and 14: 494 pose a serious refining problem
Page 15 and 16: 496 offset by the higher capital co
Page 17 and 18: 498 technology that can be used to
Page 19 and 20: 500 includes conventional petroleum
Page 21 and 22: 502 environmental footprint refers
Page 23 and 24: 504 option depending on the scale o
Page 25 and 26: 506 yielding a much higher selectiv
Page 27 and 28: 508 conditions are significantly le
Page 29 and 30: 510 protonated on the acidic cartie
Page 31 and 32: ~ .I Condensat, i ,~ ~l Cond,nsate
Page 33 and 34: 514 product upgrading unit is compa
Page 35 and 36: 516 broad terms, the information re
Page 37 and 38: 518 7.1.1 LTFT diesel as a blending
Page 39 and 40: 520 component e.g. biodiesel and/or
Page 41 and 42: 522 A comparison of the characteris
Page 43 and 44: 524 100 -[ ........................
Page 45 and 46: 526 60.0 . . : . . . i i ! i i i .
Page 47 and 48: 528 of hydrocarbon products, the pr
Page 49 and 50: 530 [41 ] F.D. Rossini, Chemical th
Page 51: 532 [83] J.A. Tilton, W.M. Smith an

Processing of Primary Fischer-Tropsch Products - University of Alberta

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