Mixed Alcohol Synthesis over Sulfided Molybdenum-Based Catalysts

Abstract

Several alumina-supported molybdenum-based catalysts were prepared by impregnation. The prepared catalysts were characterized using N 2 adsorption, X-ray diffraction, temperature-programmed desorption of ammonia, and temperatureprogrammed reduction with hydrogen. The catalytic activity in mixed alcohol synthesis was evaluated using a fixed-bed pressurized flow reaction system under conditions of 250−320 °C, 3.5−5 MPa, gas hourly space velocity of 280−5000 h −1 , and H 2 /CO ratio of 0.5−1. Effects of reaction conditions, alumina supports, and the addition of potassium were elucidated. The CO conversion and selectivity of the catalysts changed depending upon the calcination temperature of alumina supports that influenced the acid amount of the catalysts. The selectivity of C 2+ alcohols eventually reached ca. 40% in the case of calcination temperatures higher than 1000 °C. The selectivity of C 2+ alcohols was almost proportional to the addition of potassium that promoted the formation of C 2+ alcohols. The selectivity of C 2+ alcohols and the chain growth probability of alcohols with potassium carbonate were higher than those with nitrate.

Effects of Adding Cobalt and Potassium to MoS₂-based Catalysts on Mixed Alcohol Synthesis

“…All unsupported and supported catalysts were prepared using a conventional precipitation method 26) , or a sequential impregnation method 6) . The loadings of metal, equivalent to K2O, CoO, MoOS2, and MoO3, are listed in Table 1.…”

“…The volumetric flow rate of the reactor outlet gas was measured using a bubble flow meter and a dry-system gas meter. The detailed experimental procedures and sampling methods were as previously published 6) . The reaction conditions were as follows: 250-350 , 8.0 MPa, gas hourly space velocity (GHSV) of 5000 h -1 , and H2/CO ratio of 1.0.…”

“…Stoichiometric alcohol synthesis and water-gas-shift (WGS) reaction, and formation of C1-3 alcohols, CO2, and H2O were assumed to occur according to the following Eqs. (5) and (6).…”

“…5 (b)). The peak at 547 was assigned to partial reduction of Mo 6 to Mo 4 in the amorphous, highly defective, multilayered Mo oxides or heteropolymolybdates, and octahedral Mo species 30) 34) . The peak at 910 was generally related with deep reduction from Mo 4 to Mo and strong binding of all Mo species to the support, including the highly dispersed tetrahedral Mo species 34) 36) .…”

“…Catalysts supported on materials, such as silica and alumina, are highly dispersed in comparison to bulk unsupported catalysts. Our previous study investigated the effects of acidity on the supports or catalysts in mixed alcohol synthesis 6) . In other reports, the selectivities for C2 alcohols with unsupported and activated carbon-supported K _ Co _ MoS2 were 71-72 % 20), 21) and 84-90 % (CO2 excluded) 22) 25) , respectively.…”