Fuel-Blending Stocks from the Hydrotreatment of a Distillate Formed by Direct Coal Liquefaction

Abstract

The direct liquefaction of coal in the iron-catalyzed Suplex process was evaluated as a technology complementary to Fischer−Tropsch synthesis. A distinguishing feature of the Suplex process, from other direct liquefaction processes, is the use of a combination of light- and heavy-oil fractions as the slurrying solvent. This results in a product slate with a small residue fraction, a distillate/naphtha mass ratio of 6, and a 65.8 mass % yield of liquid fuel product on a dry, ash-free coal basis. The densities of the resulting naphtha (C5−200 °C) and distillate (200−400 °C) fractions from the hydroprocessing of the straight-run Suplex distillate fraction were high (0.86 and 1.04 kg/L, respectively). The aromaticity of the distillate fraction was found to be typical of coal liquefaction liquids, at 60−65%, with a Ramsbottom carbon residue content of 0.38 mass %. Hydrotreatment of the distillate fraction under severe conditions (200 °C, 20.3 MPa, and 0.41 gfeed h-1 gcatalyst -1) with a NiMo/Al2O3 catalyst gave a product with a phenol content of <1 ppm, a nitrogen content <200 ppm, and a sulfur content <25 ppm. The temperature was found to be the main factor affecting diesel fraction selectivity when operating at conditions of WHSV = 0.41 gfeed h-1 gcatalyst -1 and P H 2 = 20.3 MPa, with excessively high temperatures (T > 420 °C) leading to a decrease in diesel selectivity. The fuels produced by the hydroprocessing of the straight-run Suplex distillate fraction have properties that make them desirable as blending components, with the diesel fraction having a cetane number of 48 and a density of 0.90 kg/L. The gasoline fraction was found to have a research octane number (RON) of 66 and (N + 2A) value of 100, making it ideal as a feedstock for catalytic reforming and further blending with Fischer−Tropsch liquids.

A review on coal-to-liquid fuels and its coal consumption

“…Comprehensive analysis of emission characteristics of synthetic and conventional fuels have been compared by others [43,44]. DCL products are typically rich in polycyclic aromatics and heteroatoms [45][46][47][48], while ICL has lower aromatics content. High temperature FT-synthesis yields branched products and contains aromatics, whilst these are virtually absent in low temperature FTsynthesis [49].…”

Characterization and Refining Pathways of Straight-Run Heavy Naphtha and Distillate from the Solvent Extraction of Lignite

“…The cetane number of 42 is too low (minimum 51 required), and the density of 860 kg/m 3 is too high (maximum 845 kg/m 3 ). Higher cetane numbers can be achieved by deep hydrogenation or hydrocracking , or the addition of cetane-number improvers as blending additives, but this does not reduce the density unless the cycloalkanes can be ring-opened. Hydrocracking of coal-derived distillate does not necessarily reduce the density sufficiently to meet European diesel fuel specifications.…”

“…Heavy paraffins have very low octane numbers, and coal tar naphtha streams with meaningful heavy paraffin content have low octane numbers despite their high aromatic content. 27,28 When present, hydrotreating is typically followed by catalytic naphtha reforming. 8,9,29 Performance tests of catalytic naphtha reforming with coal liquids indicate that a liquid yield of 89−90 vol % can be anticipated in production of reformate with a research octane number of 98.…”

Low temperature autoignition of 5-membered ring naphthenes: Effects of substitution

“…(A3) reduces to the form shown in Eq. (2). During the calculation of HRR, the composition of the reacting mixture is varied (from reactants to products, proportional to the extent of heat release, as a fraction of LHV) to reasonably account for changes in heat capacity, and thus .…”

“…Naphthenes (or cycloalkanes) are a major constituent of conventional petroleum derived fuels, and they comprise a larger fraction in fuels derived from non-conventional sources such as oil sands and shale [1], liquefied coal [2], and biomass [3][4][5]. Unlike their linear counterparts, naphthenes are significantly less reactive [6] with increased sooting propensity [7].…”