IRON CATALYTIC PRECURSORS IN DRY COAL HYDROCONVERSION

The catalytic activities of three catalytic precursors based on iron ( FeSO4.7H(2)O, Fe2O3, and Fe-(CO)(5)) in direct hydroconversion of seve n coals covering a broad range of characteristics are reported in this paper. Coal itself was the catalytic support of the iron species disp ersed when iron sulfate (IS) was the precursor. When the catalyst prec ursor was iron oxide (from red mud, RM), coal and catalyst were direct ly mixed as powders, and for the iron pentacarbonyl (IF) as precursor, this was directly embedded on coal in inert atmosphere. With five of the seven coals, which were high sulfur content coals, Illinois No. 6, Mequinenza, and three Andorra-Arino, high conversions and THF-soluble s were obtained even in the absence of catalyst at 10 MPa (H-2, cold) for 30 min. With the two other coals, the conversions, THF-solubles, a nd oils/asphaltenes ratios were enhanced by CS2 addition. The temperat ures studied were 300, 350, 400, 425, and 450 degrees C. After reachin g a maximum in conversion percentages at 400 or 425 degrees C, dependi ng on the coal, a decrease takes place at the highest temperature stud ied on the THF-solubles accompanied by a considerable increase in oils formation. It seems that part of the formerly released asphaltenes, m ajor components of the THF-solubles, at 450 degrees C are converted in to oils and gas by hydrocracking reactions and into THF-insolubles by retrogressive reactions. The Mossbauer spectroscopy shows that pyrite is converted into pyrrhotite in all the processes, catalyzed or noncat alyzed, to a variable extent depending on the previous iron distributi on, on the iron chemical stage in the catalyst precursors, and on the CS2 addition. The total sulfur content in the reactor is also an influ encing factor. Important chemical and physical transformations of cata lysts are observed by XRD and SEM-EDX during the reaction. The catalyt ic performance seems to be due to the transformation of pyrite into py rrhotite, to the H2S homogeneous catalysis, and, when red mud was the catalytic precursor, to the sulfated iron oxides formation.