| AVS 59th Annual International Symposium and Exhibition | |
| Nanometer-scale Science and Technology | Wednesday Sessions |
| Session NS+AS+SS+SP-WeM |
| Session: | Nanoscale Catalysis and Surface Chemistry |
| Presenter: | M. Komarneni, North Dakota State University |
| Authors: | M. Komarneni, North Dakota State University Z. Yu, North Dakota State University A. Chakradhar, North Dakota State University U. Burghaus, North Dakota State University Y. Tsverin, Weizmann Institute of Science, Israel R. Popovitz-Biro, Weizmann Institute of Science, Israel Y. Feldman, Weizmann Institute of Science, Israel R. Tenne, Weizmann Institute of Science, Israel |
| Correspondent: | Click to Email |
Inorganic nanotubes (INT) including WS2 INT are promising materials for heterogeneous catalysis due to their intriguing properties like enhanced surface area, defects, and confinement effects. The promotion effects of Co and Ni combined with novel nanomaterials such as INT-WS2 may create the next generation hydrodesulfurization (HDS) catalysts. To verify this, M/ INT-WS2 (M = Co or Ni) catalysts were synthesized and their catalytic activity towards HDS of thiophene was characterized by gas chromatography/ambient pressure catalytic tests and ultra-high vacuum (UHV) thermal desorption spectroscopy (TDS) experiments. Synthesis of M/ INT-WS2 involved two steps: Surface activation of INT-WS2 by palladium seeding process and electroless plating method to coat nanoparticles of M. The deposited nanoparticles of M formed non-uniform layer on the INT surface. Nanoparticles of size 10-20 nm for Co (hcp structure) and 10-20 nm for Ni (fcc structure) were coated on INT-WS2. Next, the catalytic activity of M/ INT-WS2 towards thiophene HDS was characterized using an atmospheric flow reactor. M/ INT-WS2 catalysts exhibited enhanced HDS activity when compared to pristine INT-WS2 mainly due to the promotion effects of Co and Ni. Hydrogen sulfide and hydrocarbons such as 1,3-butadiene, butane, cis-2-butene, and trans-2-butene were formed as HDS products by both pristine and M/INT-WS2. Commercial HDS catalysts, CoMo and NiMo from Haldor Topsoe were found to show ~ 4 times higher activity than M/INT-WS2 synthesized in this study. These results are promising and show that further optimization of the nanofabrication process yields better HDS nanocatalysts. Furthermore, the adsorption kinetics of thiophene on M/INT-WS2 was studied by TDS at UHV conditions. Thiophene adsorbed on internal, external, and groove sites of the M/INT-WS2 bundles. Binding energies of thiophene on Ni/INT-WS2 are ~ 10 kJ/mol smaller than that of pristine INT-WS2. Thiophene also decomposed on M/WS2 NT at UHV conditions. In addition, catalytic screening of nanocatalysts such as Au and Co-Ni coated INT-WS2, pristine MoS2 nanoparticles with fullerene-like structure (IF), and Re-doped IF-MoS2 for HDS was also performed. Overall, M/INT-WS2 catalysts were the best HDS catalysts among the new nanocatalysts studied. The results also reflected the promotion effects of Co and Ni on the M/INT-WS2 catalysts for higher thiophene conversion rates.