Fischer-tropsch jet fuel process

Abstract

The invention provides a Fischer-Tropsch jet fuel refining process which has a jet fuel yield in excess of 60% by mass, said process including at least four of the following five conversion processes: a. hydrocracking one or more of a FT kerosene and heavier material fraction and a C9 and heavier FT syncrude fraction; b. oligomerising an FT syncrude fraction including hydrocarbons in the range C2 to C8; c. hydrotreating one or more of an FT syncrude fraction, a product from process b., and an alkylated FT syncrude fraction; d. aromatizing one or more of an FT syncrude fraction including hydrocarbons in the range C2 to C8, a product from process a., a product from process b, a product from process c., and a product from an aromatic alkylation process; and e. alkylating one or more of an FT syncrude fraction including hydrocarbons in the C2 to C6 range, a product from process b., and a product from process d.

Description

FIELD OF THE INVENTION[0001]The invention relates to a process for the production of jet fuel from synthetic crude produced by a Fischer-Tropsch process.BACKGROUND OF THE INVENTION[0002]The Fischer-Tropsch (FT) synthesis has been used for long time for the production of synthetic hydrocarbons from synthesis gas (syngas), a mixture of gases comprising mostly hydrogen (H2) and carbon monoxide (CO).[0003]The FT synthesis is a chemical reaction conducted over a metal oxide catalyst where the active metal comprises iron (Fe), cobalt (Co), ruthenium (Ru) and nickel (Ni). These catalysts can be produced by precipitation or can be supported in a metal oxide like alumina, titania, zirconia, magnesia and the like.[0004]The FT synthesis primary reaction can be described as follows:2H2+CO→—[CH2]—+H2O[0005]In this reaction —[CH2]— represents the primary building block of a paraffinic hydrocarbon, sometimes also referred as alkanes.[0006]The process is carried out at elevated temperatures normall...

AI Technical Summary

Benefits of technology

[0044]The alkylation process e. may be selected to reduce multiple alkylation of aromatics with olefins to maximise production of alkylaromatics in the kerosene boiling range.

[0051]It is believed that the above may result in a refinery of reduced complexity that can produce a fully synthetic jet fuel in high yield that meets international jet A-1 specifications, while co-producing chemicals and / or other transportation fuels that may also meet fuel specifications such as Euro-4.

[0052]Such a refinery may overcome some of the limitations imposed by straight run distillation yield, high linearity (high freezing point) and low aromatics content.

[0053]Depending on the selection of technology types and the ordering of the conversion units, the quantity of on specification jet fuel and quality of other products may be improved. This in itself is a further benefit of the invention, since it is flexible, it allows tailoring of the secondary products and it can accommodate different refining technology preferences.

Problems solved by technology

Although a “jet fuel only” refinery may be conceptually devised, there are limits to the yield of kerosene range material that can be obtained in practise.

Even conversion processes known in the art to be very kerosene selective, such as the conversion of propylene over solid phosphoric acid (Jones 1954), do not exclusively yield kerosene range material.

Straight run Fischer-Tropsch products have some inherent drawbacks in meeting Jet A-1 and / or BUFF specifications, namely a high linearity that results in a high freezing point and low temperature viscosity and a low aromatics content.

Furthermore, the Anderson-Schultz-Flory distribution often used to describe the carbon number distribution of Fischer-Tropsch products, show that the volume of straight run syncrude material in the kerosene range is limited, irrespective of the Fischer-Tropsch process.

However, even with a Fischer-Tropsch conversion process optimised for the production of kerosene range material, the straight run yield of kerosene is less than 30%.

It has also been pointed out that the low temperature viscosity of kerosene range material from Low Temperature Fischer-Tropsch (LTFT) syncrude may present a problem by being too viscous (Lamprecht 2006).

Preparation of Jet A-1 from high temperature Fischer-Tropsch (HTFT) hydrogenated straight run kerosene and iso-paraffinic kerosene from short chain olefin oligomerisation over Solid Phosphoric Acid (SPA), meets all the specifications, including density, however, the volumes that can be produced are unfortunately limited.

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