The catalytic effects of several molybdenum-, cobalt-, and iron-containing compounds have been examined in the reactions of dibenzothiophene (DBT) with hydrogen under conditions related to coal liquefaction. The metal compounds are candidate catalyst precursors for direct coal liquefaction. The reactions were carried out in batch microautoclave reactors at 400 °C for 30 min with 6.9 MPa (cold) hydrogen pressure 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 ratio led only to a minor increase in conversion and hydrodesulfurization. The use of a higher boiling solvent (octadecane vs tridecane) was beneficial in providing increased conversion, hydrodesulfurization, and hydrogenation. An increase in metal compound loading to 36.2 mol % led to a dramatic increase in conversion, hydrodesulfurization, and hydrocracking. Molybdenum hexacarbonyl at 36 mol % loading, with added sulfur at 6:1 ratio and octadecane solvent, gave 100% conversion of dibenzothiophene to other products with 100% hydrodesulfurization. Ammonium tetrathiomolybdate and molybdenum(III) chloride are less active under similar conditions. A cobalt-molybdenum thiocubane complex gave unexpectedly low conversions. Iron and cobalt carbonyls also provided very low conversions, even with added sulfur.
All Science Journal Classification (ASJC) codes
- General Chemical Engineering
- Fuel Technology
- Energy Engineering and Power Technology