Front-end design decisions for a process to produce sustainable aviation turbine fuel from waste materials were presented. The design employs distributed conversion of wastes to oils, which are then transported to a central facility for gasification, syngas cleaning, Fischer-Tropsch synthesis and refining, that is, a spoke-and-hub approach. Different aspects of the front-end design, that is, the steps up to syngas cleaning, were evaluated. The evaluation employed a combination of case studies, calculations, experimental investigations, and literature review. The supply of sustainable aviation fuel (SAF) as a 50:50 mixture of wastederived and petroleum-derived kerosene to meet the demand of an international airport (Pearson, Toronto) was employed as case study. The amount of raw material required made it impractical to make use of only one type of waste. Using the same set of assumptions, it was shown that in terms of cumulative transport distance required, a spoke-and-hub approach was twice as efficient as centralized processing only. Technologies for decentralized production of oils were assessed, and oils produced by pyrolysis and hydrothermal liquefaction (HTL) in pilot-scale and larger facilities were procured and characterized. These oils were within the broader compositional space of pyrolysis oils and HTL oils reported in laboratory studies. The oil compositions were employed to study the impact of oil composition on entrained flow gasification. Thermodynamic equilibrium calculations of pyrolysis and HTL oil entrained flow gasification resulted in H 2 / CO ratios of syngas and O 2 consumption rates in a narrow range, despite the diversity of feeds. At the same time, to produce an equal molar amount of syngas (H 2 + CO), less HTL oil than pyrolysis oil was required as feed. Gas cleaning technologies were reviewed to ascertain types of contaminants anticipated after gasification, their removal effectiveness, and Fischer-Tropsch catalyst poisoning 1763

Hydrocracking of Fischer−Tropsch wax can be used to produce kerosene-range products that can be blended in jet fuel. Performing the hydrocracking at pressures near that of Fischer−Tropsch synthesis could be beneficial for some refinery scenarios, as unconverted H 2 from Fischer−Tropsch synthesis can be used for hydrocracking without further compression. At lower pressure, the equilibrium alkene content during hydrocracking is increased and this could affect the product distribution. In particular, the degree of isomerization of the kerosene-range products affects the properties of hydrocracked kerosene to be used for jet fuel. The purpose of this study was to gain a better understanding of the isomer distribution obtained by wax hydrocracking. Hydrocracking of paraffin wax was carried out over a 0.5 wt % Pt/SiO 2 − Al 2 O 3 catalyst at a pressure of 2 MPa. Detailed chromatographic analysis of narrow distillation cuts of the obtained kerosene-range product was used to obtain isomer distributions for the C 8 , C 9 , and C 11 alkanes formed during hydrocracking. While the observed carbon number and isomer distributions were generally what would be expected from the hydrocracking and hydroisomerization mechanism, there were two observations that could not be explained in this way. (i) The isomer distributions were not equilibrated and were dominated by 2-and 3-methylalkanes. (ii) There were also percentage levels of cyclic compounds. An increased contribution of Pt catalysis under the chosen low-pressure conditions contributed to the observed deviations. The formation of cyclic compounds could be attributed to the increased contribution of Pt catalysis at 2 MPa. Although some speculation was offered about what could have affected the isomer distribution, the prevalence of 2-and 3methylalkanes in the product remained unexplained.

Aviation turbine fuel (jet fuel) must remain fluid enough for use at low temperatures typically experienced during high-altitude flights. The viscosity–temperature relationship of petroleum-derived jet fuel is described by the MacCoull correlation in ASTM D341. The maximum kinematic viscosity of jet fuel at −20 °C is regulated by specification, but for long-distance flights, viscosity of <12 mm2 s–1 at −40 °C is important. For synthesized paraffinic kerosene (SPK) to be approved as a synthetic jet fuel, compliance with these viscosity limits is imperative. A petroleum-based kerosene and SPK from wax hydrocracking were distilled into narrow cut (5 °C range) fractions, and for each narrow cut, density, viscosity, and refractive index values were measured over the temperature range from +60 to −60 °C. The viscosity–temperature dependences of the petroleum-derived and synthetic narrow cuts were described with comparable accuracy (relative deviation <5%) by the MacCoull correlation. Calculation of kinematic viscosity at −40 °C by extrapolating data measured at ≥−20 °C underpredicted viscosity for >200 °C boiling kerosene cuts, with a maximum relative deviation of 6.6%. The freezing point is another jet fuel property that is regulated by specification. Good agreement (±1.3 °C) was found between the end of the melting endotherm obtained by differential scanning calorimetry (DSC) and the freezing point determined according to ASTM D2386. Local maxima/minima in the freezing point of distillation cuts with increasing boiling point were observed and could be related to the freezing point characteristics of the n-alkanes.

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