(79d) Tuning of Higher Alcohol Selectivity and Productivity in CO Hydrogenation Reactions over K/MoS2 Catalysts Supported on Mesoporous Activated Carbon and Mixed Mgal Oxide

Micaela Taborga Claure^1*, Song-Hai Chai², Sheng Dai², Faisal M. Alamgir¹, Pradeep K. Agrawal¹, and Christopher W. Jones¹

1. School of Chemical & Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA, 30332 USA2.

2. Chemical Science Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA

The use of supports as a means of enhancing both activity and selectivity of MoS₂ has been investigated over the past four decades. Our previous work showed that carbon supports yield high methanol and ethanol productivities.¹ Mesoporous activated carbon, obtained via collaboration with ORNL, when used as a support, is confirmed to show greater alcohol productivity than commercial activated carbon. Hydrotalcite-derived mixed MgAl oxide (MMO) supports yield high C₃₊OH selectivity influenced by Mo-MMO interaction, but generally yield low productivity. It has been shown that the Mo:MMO ratio greatly affects selectivity while catalyst preparation methods do not.² In this work, we seek to evaluate the hypotheses that molybdenum supported on a family of MMO and carbon mixed-supports may allow tuning of higher alcohol productivity (due to carbon support) and selectivity (due to MMO support).

When Mo is first impregnated on the carbon support and the resulting material is physically ground with MMO, the selectivity trends lie in between that of the carbon and MMO single-support catalysts. Although not as selective toward higher alcohols compared to the single-support MMO catalyst, this novel mixed-support catalyst gives an increased selectivity toward higher alcohols compared to the single-support carbon catalyst, and a significant increase in higher alcohol productivity over both single-support catalysts, a result of Mo’s ability to migrate from the carbon to the MMO during sulfidation and reaction. In contrast, when Mo is first impregnated on MMO and the resulting material is ground with carbon, the catalyst has selectivity and productivity trends similar to the MMO single-support catalysts, indicating that strong Mo-MMO interactions limit the ability of Mo to migrate to the carbon support.

Detail characterization via STEM and XAS was used to probe the effect of the number of MoS₂ stacked layers on reaction performance. The combined data shed light into the role of MoS₂ stacking on the selectivity towards higher alcohols and total hydrocarbons.

References

1. Morrill, M. R.; Thao, N. T.; Agrawal, P. K.; Jones, C. W.; Davis, R. J.; Shou, H.; Barton, D. G.; Ferrari, D., Mixed MgAl Oxide Supported Potassium Promoted Molybdenum Sulfide as a Selective Catalyst for Higher Alcohol Synthesis from Syngas. Catalysis Letters 2012, 142 (7), 875-881.

2. Morrill, M. R.; Thao, N. T.; Shou, H.; Davis, R. J.; Barton, D. G.; Ferrari, D.; Agrawal, P. K.; Jones, C. W., Origins of Unusual Alcohol Selectivities over Mixed MgAl Oxide-Supported K/MoS2 Catalysts for Higher Alcohol Synthesis from Syngas. ACS Catalysis 2013, 3 (7), 1665-1675.