HYDROGENOLYTIC ACTIVITY OF SOLUBLE AND SOLID FE-BASED CATALYSTS AS RELATED TO COAL-LIQUEFACTION EFFICIENCY

A comparative activity study of soluble and solid Fe-containing catalysts for hydrogenolysis of (1) coal-simulating compounds, i.e., 2-isopropylnaphthalene (IPN), 1,2-dinapthylethane (DNE), and diphenylmethane (DPM), and (2) a Blind Canyon coal sample (designated as DECS-17) was performed. The soluble catalysts were supported on inert SiO2 and included aqua complexes of various Fe salts, i.e., sulfate, acetate, and chloride. The solid catalysts consisted of finely dispersed superacides, i.e., Fe2O3/SO42- and ZrO2/SO42-. The activity of the soluble catalysts is ascribed to the aqua complex ion [Fe(H2O)(6)](3+), which is performed or formed in situ in the presence of water and could act as a protonic acid by ligand dissociation. Kinetic rate constants for hydrodealkylation of IPN and hydrogenolytic cleavage of DPM show that at temperatures of 350-400 degrees C the above solid superacids possess markedly higher activity as compared with that of the SiO2-supported soluble Fe salts. In agreement with this finding, the same solid superacids were found to be effective hydrogenolysis catalysts in the low-temperature depolymerization-liquefaction of the Blind Canyon coal sample. Consequently, small amounts (0.1-0.5 wt %) of Fe-containing solid superacids can be conveniently used in the initial step of a modified version of the HT-BCD (mild hydrotreatment-base catalyzed depolymerization) coal liquefaction procedure.