EVALUATION OF CATION-EXCHANGED IRON FOR CATALYTIC LIQUEFACTION OF A SUBBITUMINOUS COAL

The total conversion and the; oil yield in liquefaction tests of iron ion-exchanged Black Thunder coal were found to increase by up to 23 an d 18%, respectively, relative to the untreated coal. The ion-exchanged coal samples were prepared by stirring a slurry mixture of the coal a nd ferric acetate [Fe(OOCCH3)(3)] in a 10-L fermenter.: The ion-exchan ge process, in which iron was exchanged primarily for calcium and magn esium, yielded a highly dispersed catalytic iron species for coal liqu efaction. Fe-57: Mossbauer and X-ray absorption fine structure (XAFS) spectroscopies and electron probe microanalysis (EPMA) X-ray mapping w ere used to characterize this iron species after the ion-exchange proc ess. The results indicate that the added iron is present in bimodal fo rm. The majority of the iron is present as oxyhydroxide particles rang ing from 25 to 100 Angstrom in diameter, while the smaller fraction is believed to be molecularly dispersed ferric ions held at ion-exchange (carboxyl) sites. With sufficient sulfur present in the system, the i ron is rapidly transformed to pyrrhotite (Fe1-xS) during liquefaction.