Abstract
Polar fractions in recycle solvent used in a 150t/d NEDOL coal liquefaction pilot plant were divided into acidic, basic, and neutral polar fractions by extraction with NaOH and H2SO4 solutions. These fractions were analyzed by GCFID and GCMS to identify the chemical structure.
The acidic fraction was mainly composed of phenols and indanols. Since the basic and neutral-polar fractions contained a large number of hydrogenated and alkylated homologues of polar aromatics, pyrolyzer-GC (Py-GC) system was useful in examining aromatic skeleton of these fractions. Nitrogen compounds in the basic fraction (1.7-5.5wt%) were pyridine type with 2-4 aromatic rings, and those in the neutral-polar fraction (3.3-5.9wt%) were pyrrole type with 2-4 aromatic rings. Most of the phenolic compounds in the neutral-polar fraction were with 3-4 aromatic rings, and the recycle solvent included 11.5-17.4wt% phenolic compounds in total.
The content of the nitrogen compounds in the recycle solvent increased with an increase in nitrogen content of raw coal. The basic pyridine type markedly increased, compared with the neutral pyrrole type. The degree of deactivation of catalyst for solvent hydrotreatment was not influenced by the content of the basic nitrogen compounds.
