Size-dependent Kinetics Determination of MoS2-K2O/CNTS Nanocatalyst in the Synthesis of Alcohols from Syngas

Document Type: Research Paper

Authors

University of Tehran

Abstract

The influence of Mo particle size on the catalytic activity and product selectivity of alkalized MoS2 nanocatalysts has been investigated. Nanocatalysts are prepared using a microemulsion technique with water-to-surfactant ratios of 1-12. Three different techniques, including XRD, TEM, and hydrogen chemisorption were used to determine the molybdenum average particle size and their activity and selectivity in higher alcohols synthesis (HAS) carried out in a fixed bed microreactor at 330 °C and 70 bar. To fix the percentage of CO conversion, the GHSV is changed from 3.6 to 2.57 (nl/(hr.g catalyst)). The average MoS2 particle sizes are changed from 4.5 to 11.9 nm. The experimental results showed that changing particle size from 11.9 to 4.5 nm decreased the methanol formation rate from 0.00634 to 0.00534 (mol/(hr.g catalyst)) but increased ethanol formation rate from 0.00581 to 0.00787 (mol/(hr.g catalyst)) and higher alcohols formation rate from 0.00473 to 0.00657 (mol/(hr.g catalyst)). A size-dependent kinetics model was developed to calculate the alcohol formation rates versus catalyst average particle size. The model not only matched experimental and theoretical results, but also showed that MoS2 catalyst had size-dependent structure and for the prediction of product selectivity it was easier to use this mathematical model.

Keywords


      [1]     Herman R., “Studies in Surface and Catalyst (Chapter 7),” Amsterdam, Elsevier, 1990.##

      [2]     Woo H. C. and Park K. Y., “Mixed Alcohol Synthesis from Carbon Monoxide and Hydrogen over Potassium Promoted Molybdenum Carbide Catalysts,” Applied Catalysis, 75, 1991, 267-280.##

      [3]     Jiang M., Bian G. Z., and Fu Y. L., “Effect of the K-Mo Interaction in K-MoS2/γ-Al2O3 Catalysts on the Properties for Alcohol Synthesis from Syngas,” Journal of Catalysis, 146, 1994, 144-154.##

      [4]     Lee J. S., Kim S., Lee K. H., Nam I. S., et al., “Role of Alkali Promoters in K/MoS2 Catalysts for CO-H2 Reactions,” Applied Catalysis, 110, 1994, 11-25.##

      [5]     Tatsumi T., Muramatsu A., Yokota K., and Tominga H., “Mechanistic Study on the Alcohol Synthesis over Molybdenum Catalysts: Addition of Probe Molecules to CO-H2,” Journal of Catalysis, 115, 1989, 388-398.##

      [6]     Surisetty V. R., Tavasoli A., and Dalai A. K., “Synthesis of Higher Alcohols from Syngas over Alkali Promoted MoS2 Catalysts,” Applied Catalysis, 365, 2009, 243-251.##

      [7]     Iranmahboob J., Toghiani H., and Hill D. O., “Dispersion of Alkali on the Surface of Co-MoS2/Clay Catalyst: a Comparison of K and Cs as a Promoter for Synthesis of Alcohol,” Applied Catalysis, 247, 2003, 207-218.##

      [8]     Iranmahboob J. and Hill D. O., “Alcohol Synthesis from Syngas over K2CO3/CoS/MoS2 on Activated Carbon,”Catalysis Letters, 78, 2002, 49-56.##

      [9]     Leendert Bezemer G. and Bitter J. H., “Cobalt Particle Size Effects in the Fischer- Tropsch Reaction Studied with Carbon Nanofiber Supported Catalysts,” J. of American Chemical Society, 128, 2006, 39-56.##

    [10]    Parmon V. N., “Thermodynamic Analysis of the Effect of the Nanoparticle Size of the Active Component on the Adsorption Equilibrium and the Rate of Heterogeneous Catalytic Processes,”Physical Chemistry, 413, 2007, 42-48.##

    [11]    Murzin D. Y., “Kinetic Analysis of Cluster Size Dependent Activity and Selectivity,” Journal of Catalysis, 276, 2010, 85-91.##

    [12]    Dmitry Y. M., “Thermodynamic Analysis of Nanoparticle Size Effect on Catalytic Kinetics,” Chemical Engineering Science, 64, 2009, 1046-1052.##

    [13]    Dmitry Y. M., “Size-dependent Heterogeneous Catalytic Kinetics,” Journal of Molecular Catalysis A: Chemical, 315, 2010, 226–230.##

    [14]    Park T. Y., Nam I. S., and Kim Y. G., “Kinetic Analysis of Mixed Alcohol Synthesis from Syngas over K/MoS2 Catalyst,” Ind. Eng. Chem. Res., 36, 1997, 5246-5257.##

    [15]    Surisetty V., Dalai A., and Kozinski J., “Intrinsic Reaction Kinetics of Higher Alcohol Synthesis from Synthesis Gas over a Sulfided Alkali-Promoted Co-Rh-Mo Trimetallic Catalyst Supported on Multi-walled Carbon Nanotubes (MWCNTs),” Energy and Fuels, 24,2010, 4130–4137.##

    [16]    MartŁnez A. and Prieto G., “Breaking the Dispersion-reducibility Dependence in Oxide-supported Cobalt Nanoparticles,” Journal of Catalysis, 2007, 245, 245-470.##

    [17]    Kim W. Y., Haoka T., Kishida M., and Wakabayashi K., “Hydrogenation of Carbon Monoxide over Zirconia-supported Palladium Catalysts Prepared using Water-in-oil Microemulsion,” Appl. Catal. A, 1997, 155, 283-289.##

    [18]    Tago T., Hanaoka T., Dhupatemiya P., Hayashi H., et al., “Effects of Rh Content on Catalytic Behavior in CO Hydrogenation with Rh-silica Catalysts Prepared using Microemulsion,” Catal. Lett., 2000, 64(1), 27-31.##

    [19]    Eriksson S., Nylén U., Rojas S., and Boutonnet M., “Preparation of Catalysts from Microemulsions and their Applications in Heterogeneous Catalysis,”Applied Catalysis A: General, 2004, 265, 207–219.##

    [20]    Gunturu A., KuglerE., Cropley J., and Dadyburjor D .,“A Kinetic Model for the Synthesis of High-molecular-weight Alco-hols over a Sulfided Co K Mo/C Catalyst,” Ind. Eng. Chem. Res., 1998, 37, 2107-2115.##