Influence of H2O and H2S on the composition, activity, and stability of sulfided Mo, CoMo, and NiMo supported on MgAl2O4 for hydrodeoxygenation of ethylene glycol [electronic resource]

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Ngôn ngữ: eng

Ký hiệu phân loại: 660.6 Biotechnology

Thông tin xuất bản: Oak Ridge, Tenn. : Distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy, 2017

Mô tả vật lý: Size: p. 106-121 : , digital, PDF file.

Bộ sưu tập: Metadata

ID: 263107

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Here in this work, density functional theory (DFT), catalytic activity tests, and in-situ X-ray absorption spectroscopy (XAS) was performed to gain detailed insights into the activity and stability of MoS
2
, Ni-MoS
2
, and Co-MoS
2
catalysts used for hydrodeoxygenation (HDO) of ethylene glycol upon variation of the partial pressures of H
2
O and H
2
S. The results show high water tolerance of the catalysts and highlight the importance of promotion and H
2
S level during HDO. DFT calculations unraveled that the active edge of MoS
2
could be stabilized against SO exchanges by increasing the partial pressure of H
2
S or by promotion with either Ni or Co. The Mo, NiMo, and CoMo catalysts of the present study were all active and fairly selective for ethylene glycol HDO at 400 �C, 27 bar H
2
, and 550?2200 ppm H
2
S, and conversions of ?50?100%. The unpromoted Mo/MgAl
2
O
4
catalyst had a lower stability and activity per gram catalyst than the promoted analogues. The NiMo and CoMo catalysts produced ethane, ethylene, and C1 cracking products with a C
2
/C
1
ratio of 1.5?2.0 at 550 ppm H
2
S. This ratio of HDO to cracking could be increased to ?2 at 2200 ppm H
2
S which also stabilized the activity. Removing H
2
S from the feed caused severe catalyst deactivation. Both DFT and catalytic activity tests indicated that increasing the H
2
S concentration increased the concentration of SH groups on the catalyst, which correspondingly activated and stabilized the catalytic HDO performance. In-situ XAS further supported that the catalysts were tolerant towards water when exposed to increasing water concentration with H2O/H2S ratios up to 300 at 400?450 �C. Raman spectroscopy and XAS showed that MoS2 was present in the prepared catalysts as small and highly dispersed particles, probably owing to a strong interaction with the support. Linear combination fitting (LCF) analysis of the X-ray absorption near edge structure (XANES) spectra obtained during in-situ sulfidation showed that Ni was sulfided faster than Mo and CoMo, and that Mo was sulfided faster when promoted with Ni. Extended X-ray absorption fine structure (EXAFS) results showed the presence of MoS
2
in all sulfided catalysts. Lastly, sulfided CoMo was present as a mixture of CoMoS and Co
9
S
8
, whereas sulfided NiMo was present as NiMoS.

1. 09 biomass fuels
2. Dft
3. Hydrodeoxygenation
4. Molybdenum sulfide
5. Xas

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Influence of H<sub>2</sub>O and H<sub>2</sub>S on the composition, activity, and stability of sulfided Mo, CoMo, and NiMo supported on MgAl<sub>2</sub>O<sub>4</sub> for hydrodeoxygenation of ethylene glycol [electronic resource]