Kinetics of sulfur removal from a liquid coal residue in thermal, hydrothermal, and hydrocatalytic cracking

An asphaltenic residue from deasphalting a synthetic crude obtained by direct liquefaction of a subbituminous Spanish coal was submitted to several upgrading routes. In this paper, the kinetics of sulfur-removal reactions in thermal, hydrothermal, and hydrocatalytic cracking are reported. The sulfur-removal reactions fit a 2.7 kinetic order for the thermal process, a 3.8 kinetic order for the hydrothermal process, and a 4.7 kinetic order for the hydrocatalytic process, the activation energy being lowest in the hydrocatalytic process. The activation energy for the thermal processes is higher in the presence of hydrogen. The percentages of sulfur removal range from 3.6 to 56.6 wt % in thermal cracking, from 15.3 to 61.5 wt % in hydrothermal cracking, and from 19.1 to 55.0 wt % in hydrocatalytic cracking. The percentages of sulfur removal at low reaction times for the three processes increase in the order thermal < hydrothermal < hydrocatalytic.