Influence of Composition of Solvent on Solvent Hydrotreatment in NEDOL Coal Liquefaction Process
Masato KOUZU, Yasunori KURIKI, Yoshikazu SUGIMOTO
Recycle solvents obtained from 150t/d NEDOL coal liquefaction pilot plant were hydrotreated over sulfided Ni-Mo/γ-Al2O3 by using an experimental downflow fixed bed reactor at 325°C under 8MPa to examine an influence of composition of solvent on the solvent hydrotreatment. The hydrotreated solvents were divided into seven fractions (compound classes) by HPLC, and the hydrogenation reactivity of each compound class was investigated.
The hydrogenation reactivity of the compound classes was in the following order, mono-aromatics << di-aromatics < tetra-aromatics < tri-aromatics < polar fraction. When Adaro or Ikeshima coal was processed in the pilot plant, as compared with an operation for Tanito-harum coal, the reaction rate constant for solvent hydrotreatment decreased owing to smaller content of polar fraction.
The increase of partially hydrogenated aromatic compounds, naphthenic compounds, in the solvent lowered the hydrogenation reactivity of the non-polar aromatic fractions. The decrease of the reaction rate constant for solvent hydrotreatment in an operation with higher coal concentration slurry (40→50wt%) resulted from the increase of the partially hydrogenated aromatic compounds due to the enhancement of degree of solvent hydrotreatment to promote the hydrogen donating ability.
Results of a series of our researches for the solvent hydrotreatment are useful in identifying the nature of feedstock for solvent on the basis of the properties of coal employed and the operating conditions, which helps to design the solvent hydrotreater.
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