Manganese oxide supported cobalt‐nickel catalysts for carbon monoxide hydrogenation

Abstract

Performances of manganese oxide‐supported cobalt, nickel, and their combinations of varying compositions have been investigated for CO hydrogenation to lower hydrocarbons using a fixed bed microreactor at atmospheric pressure and temperatures ranging from 525 to 575 K. While Co/MnO was found to exhibit high selectivity to olefins in the C2–C4 range, the total yield of hydrocarbons was low. Addition of nickel to cobalt gave a stable catalyst having improved hydrocarbon yields while still retaining good olefin selectivity. The effect of operating conditions on product distribution was studied. Lower space times and higher temperatures favored olefin selectivity. A comparison of Ni and Co catalysts on various support materials was made. MnO‐supported Co catalyst gave significantly higher olefin/paraffin ratio than that obtained using conventional supports such as SiO2 or Al2O3. It was found that Co/MnO exhibited high water‐gas shift activity, and suppressed hydrogen uptake due to strong metal‐support interaction which favored olefin formation. This can be explained on the basis of competitive adsorption of water and hydrogen on the same surface sites resulting in low hydrogenation activity but improved olefin selectivity.

Direct conversion of synthesis gas to aromatic hydrocarbons: Variation of product distribution with time‐on‐stream

“…Figure 2 shows that the selectivity to C3 and C, fractions slightly decreases, and that to C, increases with time-on-stream during the initial periods. An increase in the formation of olefins during the initial deactivation of the catalyst has also been observed for MnO supported Co-Ni systems (Varma et al, 1985a). As shown in Figure 3, the fraction of olefins in both Cz and C3 hydrocarbons initially increases with time-on-stream but later shows a slight declining trend thus giving a maximum at about 40-50 h of operation.…”

Carbon Monoxide Hydrogenation over Zirconia Supported Ni and Co-Ni Bimetallic Catalysts

“…However, a major drawback of the process is the low selectivities for gasoline and diesel products. It has been reported that bimetallic catalysts containing Ni, Fe, Co and Ru are more active towards CO conversion, and exhibit markedly improved selectivity for olefins and heavier hydrocarbons as compared to single metal catalysts [2][3][4][5][6][7]. A large number of combinations of bimetallic catalysts are possible from the above four metals by varying the supports such as silica, alumina, titania, zirconia, zeolites, etc.…”

“…It has been reported that the bimetallic catalysts containing Ni, Fe, Co and Ru are more active towards CO conversion and exhibit markedly improved selectivity for olefins and heavier hydrocarbons as compared with single metal catalysts [2][3][4][5][6][7]. Verma et al [3] studied the performance of MnO supported Co, Ni and Co-Ni bimetallic catalysts at 525-575 K and at atmospheric pressure. Addition of Ni to Co/MnO catalysts produced a stable catalyst with high CO conversion activity.…”

Impact of Na Promoter on Structural Properties and Catalytic Performance of CoNi/Al2O3 Nanocatalysts for the CO Hydrogenation Process: Fischer–Tropsch Technology

“…The possible rate-determining steps were identified, whereas all other steps were assumed to be at quasi-equilibrium. Storch et al [41] developed a useful LHHW kinetic equation for the FTS reaction based the enolic mechanism by considering dissociative adsorption of H 2 and molecular adsorption of CO. The reaction rate of the rate-determining step is:…”