Two-stage liquefaction of a Spanish subbituminous coal

Abstract

A Spanish subbituminous coal has been processed in two-stage liquefaction in a non-integrated process. The first-stage coal liquefaction has been carried out in a continuous pilot plant in Germany at Clausthal Technical University at 400°C of temperature, 20 MPa hydrogen pressure and anthracene oil as solvent. The second-stage coal liquefaction has been performed in continuous operation in a hydroprocessing unit at the Instituto de Carboquimica at 450°C and 10 MPa hydrogen pressure, with two commercial catalysts: Harshaw HT-400E (Co-Mo/Al 2O 3) and HT-500E (Ni-Mo/Al 2O 3). The total conversion for the first-stage coal liquefaction was 75.41 wt% (coal d.a.f.), being 3.79 wt% gases, 2.58 wt% primary condensate and 69.04 w% heavy liquids. The heteroatoms removal for the second-stage liquefaction was 97–99 wt% of S, 85–87 wt% of N and 93–100 wt% of O. The hydroprocessed liquids have about 70% of compounds with boiling point below 350°C, and meet the sulphur and nitrogen specifications for refinery feedstocks. Liquids from two-stage coal liquefaction have been distilled, and the naphtha, kerosene and diesel fractions obtained have been characterized.