The CO-catalyzed conversion of H2S to H-2 plus sulfur - Part 2. The thermal decomposition of COS

The pyrolysis of COS has been studied over the temperature range 300 to 750 degrees C using a variety of catalysts. The observed product distribution confirmed that two parallel reaction paths: 2 COS --> 2 CO + S-2 (1) and 2 COS --> CO2 + CS2 (4) are involved in the decomposition. The decomposition yield increased with rising temperature, accompanied a shift in selectivity . At temperatures lower than similar to 700 degrees C the disproportionatio n reaction 4 was predominant, whereas at temperatures higher than 700 degre es C, reaction 2 was favoured. In the high-temperature region (700 to 750 d egrees C) it was possible to achieve full suppression of reaction 4 with ad ded CSI. The pyrolysis of COS was also studied in a reactor packed with qua rtz chips without catalysts at high temperatures. Between 800 and 900 degre es C, up to 99% conversion (with respect to the thermodynamic limit) could be achieved, with the almost complete absence of the disproportionation rea ction 4. The results point to the commercial potential in the two-step reac tion sequence: [GRAPHICS] for the economic conversion of hydrogen sulfide to hydrogen and sulfur.