Hydrocracking of Fischer-Tropsch Wax

Abstract

The low-temperature Fischer-Tropsch synthesis (LTFT) processing of renewable feedstocks combined with the hydrocracking of its solid product is an effective way to produce synthetic renewable engine fuels. The hydrocracking of an FT wax derived from natural gas using the LTFT synthesis was studied in this paper. The hydrocracking was carried out in a tubular fixed-bed reactor with a cocurrent flow of the feedstock and hydrogen. Reaction temperatures in the range of 305– 370 °C, a pressure of 8 MPa, an H2/feed ratio of 500 m3/m3 and weight hour space velocities (WHSV) of 1; 2 and 4 h-1 were tested. The naphtha fraction (boiling up to 200 °C) was the main product of the hydrocracking under all the tested reaction conditions. It could be used as a component into petroleum-derived gasoline in a neat form or the after processing by common refinery processes (isomerization and/or reforming). The production of low-sulfur and low-aromatic paraffinic solvent or the utilization as a feedstock for steam cracking could be some other options of the naphtha fraction utilization. The maximum yield of the gaseous products (depending on the reaction temperatures and WHSV) was 20 wt.%. They were primarily composed of n-alkanes and isoalkanes and could be, therefore, used as an optimal feedstock for steam cracking as well. The C3-C4 fraction of the gaseous products could be also utilized as an LPG fuel. Very low yields (up to 10.4 wt.%) of the middle distillates were obtained under all the tested reaction conditions. Due to their saturated nature, their densities were very low and, additionally, poor low-temperature properties can be expected.

Value-Added Pyrolysis of Waste Sourced High Molecular Weight Hydrocarbon Mixtures

“…FT waxes are low-value products, therefore value-adding conversions seem to be necessary. The most commonly used technologies are hydroconversion processes (hydrotreating, hydrocracking, hydroisomerisation) [12][13][14][15]. Due to the applied hydrogen atmosphere, the products obtained from FT wax hydrocracking mainly contain saturated hydrocarbons (n-and isoparaffins) [12].…”

“…The most commonly used technologies are hydroconversion processes (hydrotreating, hydrocracking, hydroisomerisation) [12][13][14][15]. Due to the applied hydrogen atmosphere, the products obtained from FT wax hydrocracking mainly contain saturated hydrocarbons (n-and isoparaffins) [12]. Because of the composition, the petroleum and diesel fraction obtained by FT wax hydrocracking can be used as an excellent fuel blending component (good cold flow properties with relatively high cetane number).…”

“…Due to the extended amount of n-paraffins and the lack of olefin and aromatic hydrocarbons, the obtained gasoline fraction has a low octane number. Light products of the hydrocracking include mostly propane and butane, which can be utilized as LPG [12][13][14][15].…”

Hydrocracking of a Heavy Vacuum Gas Oil with Fischer–Tropsch Wax

“…Such fuels can be utilised either directly as blending components or, after upgrading, based on the hydrogenation or hydroisomerisation, for example, to improve the cold-flow properties or octane number, respectively. In comparison with conventional biofuels, the properties of XTL fuels are more similar to the properties of the common petroleum-derived fuels so they can be used in the current engines without limitation [7][8][9][10] (so called drop-in fuels).…”

“…A heavy vacuum gas oil (HVGO), i.e., the product of crude oil vacuum distillation, is the most common feedstock for catalytic hydrocracking in oil refineries. Its hydrocracking is usually carried out at reaction temperatures of 400-450 • C, relatively high pressures (8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20) and in a high excess of hydrogen to suppress the formation of coke [12]. The reaction conditions of hydrocracking neat FTS products, which are usually produced from natural gas or coal on an industrial scale, differ due to the specific composition and properties of the feedstock and target composition and properties of the products.…”