REACTIONS OF DIBENZOTHIOPHENE WITH HYDROGEN IN THE PRESENCE OF SELECTED MOLYBDENUM, IRON, AND COBALT COMPOUNDS

The catalytic effects of several molybdenum-, cobalt-, and iron-contai ning compounds have been examined in the reactions of dibenzothiophene (DBT) with hydrogen under conditions related to coal liquefaction. Th e metal compounds are candidate catalyst precursors for direct coal li quefaction. The reactions were carried out in batch microautoclave rea ctors at 400 degrees C for 30 min with 6.9 MPa (cold) hydrogen pressur e and tridecane solvent. A metal loading of 0.5 mol % resulted in low conversion and only hydrogenation. Addition of sulfur in a 4:1 molar r atio led only to a minor increase in conversion and hydrodesulfurizati on. The use of a higher boiling solvent (octadecane vs tridecane) was beneficial in providing increased conversion, hydrodesulfurization, an d hydrogenation. An increase in metal compound loading to 36.2 mol % l ed to a dramatic increase in conversion, hydrodesulfurization, and hyd rocracking. Molybdenum hexacarbonyl at 36 mol % loading, with added su lfur at 6:1 ratio and octadecane solvent, gave 100% conversion of dibe nzothiophene to other products with 100% hydrodesulfurization. Ammoniu m tetrathiomolybdate and molybdenum(III) chloride are less active unde r similar conditions. A cobalt-molybdenum thiocubane complex gave unex pectedly low conversions. iron and cobalt carbonyls also provided very low conversions, even with added sulfur.