Skip to Main Content
 

Global Search Box

 
 
 
 

Files

File List


36340.pdf (7.08 MB)

ETD Abstract Container

Abstract Header

Sulfur Tolerant Supported Bimetallic Catalysts for Low Temperature Water Gas Shift Reaction

Yun, Seonguk
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1573224656177825

Abstract Details

2019, PhD, University of Cincinnati, Engineering and Applied Science: Chemical Engineering.
A series of model CuPd nanoparticles, CoMo oxide nanoparticles, different metal oxide supported Mo sulfide catalysts, and sets of different composition ratio and surface coverage of CoMo sulfide catalysts were prepared and investigated as sulfur-tolerant WGS catalysts. For comparison, monometallic catalysts prepared by incipient wetness impregnation, as well as commercial CoMo catalysts, were also investigated. The model CoMo-S catalysts at the monolayer surface coverage employed in this research are highly promising as sulfur-tolerant WGS catalysts displaying desirable structural, morphological, and compositional properties. The CuPd-2 catalysts maximized the number of WGS-active Cu0 sites with the optimized ratio (2.37) of CuO/CuAl2O4, showing higher WGS activity, thermal stability, and sulfur tolerance at 250°C than any other tested Cu-based catalysts. Cu-Pd bimetallic alloy catalysts showed enhanced reducibility due to the Pd-promoting effect through hydrogen spillover and additional reducible CuO sites through Cu species diffusion from the CuO shell to Al2O3. The Mo and CoMo oxide nanoparticles were prepared by a metal colloid chemical co-reduction method by modifying the concentrations of the Mo and Co precursors during synthesis. The WGS activity of n-Mo-S and n-CoMo-S catalysts increased due to the reduction of the average particle size up to 5-Mo and 10-CoMo. The extent of sulfidation of n-Mo-S catalysts was saturated at 5-Mo and correlated with WGS activity. 10-CoMo-S catalysts were the most active among the tested Al2O3-supported Mo-based catalysts with similar sulfur dependence to a commercial CoMo/MgO catalyst. Mo-S/ZrO2 showed the highest WGS activity in 1,000 ppm H2S-containing feed and lowest H2S dependence in H2S-free feed among ZrO2-, Al2O3-, TiO2-, CeO2-, and SiO2-supported Mo catalysts. Weak support-MoO3 interaction of ZrO2 favored a higher extent of sulfidation, correlated to the WGS activity, and stable sulfur bonding in Mo-S/ZrO2 led to low sulfur dependence. Mo5-S/ZrO2 at monolayer MoO3 coverage showed optimal WGS activity and extent of sulfidation, suggesting that the topmost Mo-S layer comprised WGS-active catalytic sites. CoMo-S/ZrO2 catalyst at monolayer CoMo-O coverage with Co/Mo = 0.3 catalysts was the most active WGS catalyst among all the tested catalysts in this study. This catalyst was thermally stable for at least 4 weeks of reaction test, and demonstrated low sulfur tolerance under H2S-free feed at 350°C and GHSV 35,000 h-1. Structurally, this catalyst exhibited optimized surface coverage, highly dispersed CoMo-S species, saturated extent of sulfidation, and optimal number of active sites. The important result of this study is that cobalt promoter facilitated the dispersion of CoMo-S species, the formation of active surface sulfur, and the reactivity of CoMo-S, while cobalt promoter weakened the sulfur bond in CoMo-S species, leading not only to enhanced WGS activity, but also to increased sulfur dependence. However, optimal amount of Co addition could significantly reduce the active metal loading compared to the commercial CoMo catalysts, which could save a great deal of raw material cost in catalyst production. Therefore, the optimized CoMo-S/ZrO2 catalyst is a highly active, thermally stable, chemically stable, and economically beneficial sulfur-tolerant WGS catalyst to apply in hydrogen production using biomass-derived syngas.
Vadim Guliants, Ph.D. (Committee Chair)
Anastasios Angelopoulos, Ph.D. (Committee Member)
Junhang Dong, Ph.D. (Committee Member)
Mingming Lu, Ph.D. (Committee Member)
199 p.
Chemical Engineering
Water gas shift reaction; Mo sulfide; surface coverage; nanoparticle; heterogeneous catalysis

Recommended Citations

Citations

  • Yun, S. (2019). Sulfur Tolerant Supported Bimetallic Catalysts for Low Temperature Water Gas Shift Reaction [Doctoral dissertation, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1573224656177825

    APA Style (7th edition)

  • Yun, Seonguk. Sulfur Tolerant Supported Bimetallic Catalysts for Low Temperature Water Gas Shift Reaction. 2019. University of Cincinnati, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1573224656177825.

    MLA Style (8th edition)

  • Yun, Seonguk. "Sulfur Tolerant Supported Bimetallic Catalysts for Low Temperature Water Gas Shift Reaction." Doctoral dissertation, University of Cincinnati, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1573224656177825

    Chicago Manual of Style (17th edition)

ucin1573224656177825
536
© 2019, all rights reserved.
This open access ETD is published by University of Cincinnati and OhioLINK.