(600z) Thermal Decomposition of K-Comosx Catalyst Precursors: Effects On Catalyst Morphology and Performance

Cobalt molybdenum sulfide-type mixed alcohol catalysts were
synthesized via calcination of precipitated bulk sulfides and studied with
temperature programmed decomposition analysis. Precursors containing aqueous
potassium were also considered. Precipitates thermally decomposed in unique
events which released ammonia, CO2, and
sulfur. Higher temperature treatments led to more crystalline and less active
catalysts in general with ethanol productivity falling from 203 to 97
g-(kg-cat)-1-h-1 when
the calcination temperature was increased from 375 to 500°C. The addition of
potassium to the precursor led to materials with crystalline potassium sulfides
and good catalytic performance. In general, less potassium was required to
promote alcohol selectivity when added before calcination. At calcination
temperatures above 350 °C, segregated cobalt sulfides were observed, suggesting
that thermally decomposed sulfide precursors may contain a mixture of
molybdenum and cobalt sulfides instead of a dispersed Co-Mo-S type of material.

Table
1. Catalyst thermal history, surface area,
and elemental analysis

Figure 1. Performance of catalysts 1-5 in Table 1. Green = ethanol, purple = propanol, blue = methanol. Data
was collected at 325 °C, p_CO = p_H2
= 4.8 MPa, 6000 NTPL-(kg-cat)^-1-h^-1.