EFFECT OF CATALYST DISPERSION ON COAL-LIQUEFACTION WITH IRON CATALYSTS

The effectiveness of fine particle iron catalysts for first-stage coal liquefaction is influenced by the dispersion of the catalyst. Dispers ion can be characterized by catalyst surface area, particle size, and crystallite size. Increasing catalyst dispersion by increasing catalys t surface area, and decreasing catalyst particle size and/or decreasin g catalyst crystallite size, results in higher levels of coal conversi on to soluble products. For iron systems, a distinction must be made b etween the catalyst precursor and the active catalyst. Coal impregnati on with iron catalyst precursors results in higher coal conversion tha n simple mixing of powdered catalyst precursors with coal. Impregnatio n of iron precursors onto coal affects catalyst dispersion by maintain ing the fine particle size of the precursor during the transformation to the active catalyst phase. Agglomeration to larger particle size ca talysts can occur if the iron catalyst precursors are physically mixed with the coal.