Selective synthesis of light olefins from syngas over potassium-promoted molybdenum carbide catalysts

Park, Ki Yeop; Seo, Won Kyu; Lee, Jae Sung

doi:10.1007/bf00764327

Cited by 55 publications

(33 citation statements)

References 13 publications

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“…Kim et al found that supported and unsupported Mo 2 C catalysts exhibited CO hydrogenation rates at atmospheric pressure similar to those for Ru [7], a metal that is known to be an effective CO hydrogenation catalyst. The effects of pressure [8] and promoters such as K [12,17,19], Rb [20] and Ru/Co [9,10] have also been explored. While the utility of early transition metal carbides and nitrides for syngas conversion reactions has been demonstrated, very little is known about the reaction mechanisms over these materials.…”

Section: Introductionmentioning

confidence: 99%

“…All of these pathways require a catalyst that can perform some, if not all, of the following steps: (i) H 2 activation, (ii) CO adsorption and activation, (iii) C-O bond cleavage, (iv) C-C bond formation, and (v) hydrogenation. Early transition metal carbides and nitrides have been demonstrated to be active for syngas conversion reactions, catalyzing the aforementioned reaction steps, albeit to varying degrees depending upon metal/non-metal atom type, reaction conditions, and presence of promoters [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21]. Kojima et al were among the first to investigate the CO hydrogenation activities of early transition metal carbides [3][4][5].…”

Section: Introductionmentioning

confidence: 99%

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Fischer–Tropsch synthesis over early transition metal carbides and nitrides: CO activation and chain growth

Schaidle

Thompson

2015

Journal of Catalysis

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a b s t r a c tA series of transition metal carbide and nitride catalysts (Mo 2 C, Mo 2 N, W 2 C, W 2 N, VC, VN, NbC, and NbN) were prepared and evaluated for Fischer-Tropsch synthesis. The activity trend was Mo 2 C $ W 2 C $ VN $ NbN > Mo 2 N $ W 2 N ) VC $ NbC, with carbides and nitrides of the same parent metal exhibiting significantly different turnover frequencies (TOF). For example, the Mo 2 C catalyst exhibited a TOF of 0.36 s À1 at 300°C whereas the TOF for the Mo 2 N catalyst was 0.04 s À1 . The carbides and nitrides favored light hydrocarbons (C 1 -C 4 ) exhibiting a values between 0.31 and 0.43 at 290°C, and were active for the water-gas shift reaction. Results from temperature programmed desorption and reaction indicated that both the Mo 2 N and Mo 2 C catalysts are capable of direct (without H 2 assistance) CO dissociation; however, the activation barrier is much higher over Mo 2 N than Mo 2 C. The results also indicate that C-C coupling over the Mo 2 C surface was facilitated by molecularly adsorbed CO (without H 2 pre-adsorption), suggesting the primary pathway to C 2+ hydrocarbons was through the oxygenate mechanism.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Fischer–Tropsch synthesis over early transition metal carbides and nitrides: CO activation and chain growth

Schaidle

Thompson

2015

Journal of Catalysis

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“…Carbide catalysts have been the subject of numerous theoretical and experimental investigations since their activity was compared to platinum by Levy and Boudart [12], and have proven to be active for many different reactions [8,3,13]. Molybdenum carbide in particular has shown catalytic activity for conversion of syngas to hydrocarbons and alcohols [14,15,16,17,18,19,20,8,21,22], steam/dry reforming [6,18,3,10,23,24,25], water-gas shift [26,27,28], methane aromatization [7,29,30], hydrocarbon hydrogenolysis [6,19,14,18], hydrocarbon hydrogenation [8,31,32] and various other reactions involving hydrocarbons and alcohols [8,33,30,34,35]. The activity and selectivity of molybdenum carbide differs depending on the synthesis procedure and reaction conditions [17], and can be tuned using alkali metal promoters such as potassium or rubidium [36,37].…”

Section: Introductionmentioning

confidence: 99%

Elementary steps of syngas reactions on Mo2C(001): Adsorption thermochemistry and bond dissociation

Medford

Vojvodić

Studt

et al. 2012

Journal of Catalysis

102

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Density functional theory (DFT) and ab initio thermodynamics are applied in order to investigate the most stable surface and subsurface terminations of Mo 2 C(001) as a function of chemical potential and in the presence of syngas. The Mo-terminated (001) surface is then used as a model surface to evaluate the thermochemistry and energetic barriers for key elementary steps in syngas reactions. Adsorbtion energy scaling relations and Brønsted-Evans-Polanyi relationships are established and used to place Mo 2 C into the context of transition metal surfaces. The results indicate that the surface termination is a complex function of reaction conditions and kinetics. It is predicted that the surface will be covered by either C 2 H 2 or O depending on conditions. Comparisons to transition metals indicate that the Mo-terminated Mo 2 C(001) surface exhibits carbon reactivity similar to transition metals such as Ru and Ir, but is significantly more reactive towards oxygen.

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“…High surface area carbon as support in Fe-Mn catalyst had certain properties in the stabilization of highly dispersed Fe particles, presumably due to the presence of physical barriers which suppress surface migration and resultant agglomeration [9,10]. Unsupported Mo 2 C produced mostly C 2 -C 5 paraffins with high olefin selectivity while large amounts of CO 2 were also produced [15]. The surface deposited carbon in iron-based catalysts caused an increase in the ratio of alkenes to alkanes, and a rise in the percentage of shorter-chain hydrocarbons at the expense of large-molecule hydrocarbons [16].…”

Section: Introductionmentioning

confidence: 97%

Carbon modified Fe–Mn–K catalyst for the synthesis of light olefins from CO hydrogenation

Zhang

Fan

Zhao

et al. 2011

Reac Kinet Mech Cat

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A novel carbon modified Fe-Mn-K catalyst for light olefin synthesis from CO hydrogenation was prepared by the sol-gel method. The effect of carbon contents on the structure and performance of the catalysts was investigated. With the incorporation of carbon, the catalysts showed much different morphology from that prepared by co-precipitation. At the carbon contents between 0.23 and 6.66 wt%, the catalyst particles were around 10 nm while the carbon phase was amorphous. The activity test results indicated that the catalysts (Fe/Mn/K molar ratio = 60/20/1) with carbon modification showed high conversion of CO and selectivity to light olefins with low CH 4 selectivity. At the carbon content of 2.43 wt%, the total C 2 -C 4 content in all hydrocarbons and O/P (olefin/paraffin) in the C 2 -C 4 fraction was 49 wt% and 4.89, respectively. Furthermore, when the K content in the catalyst was reduced by half, the C 2 -C 4 olefin yield raised from 60 to 71 g/Nm 3 syngas. The formation of carbon provided a more hydrophobic surface, which inhibited the water gas shift reaction (WGSR) and caused a decrease in CO 2 selectivity. The dispersion of carbon favored the formation and stabilization of small particles, and promoted the production of light olefins via suppressing the chain propagation.

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Selective synthesis of light olefins from syngas over potassium-promoted molybdenum carbide catalysts

Cited by 55 publications

References 13 publications

Fischer–Tropsch synthesis over early transition metal carbides and nitrides: CO activation and chain growth

Fischer–Tropsch synthesis over early transition metal carbides and nitrides: CO activation and chain growth

Elementary steps of syngas reactions on Mo2C(001): Adsorption thermochemistry and bond dissociation

Carbon modified Fe–Mn–K catalyst for the synthesis of light olefins from CO hydrogenation

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