Higher alcohol synthesis from syngas was studied over MoS2 during the induction period by varying the support, carbon (C) and MgAl mixed oxide (MMO), and the presence of the K promoter. MoS2 on C and MMO supports produced longer chain hydrocarbons compared to unsupported MoS2. Potassium is known to shift product distribution from hydrocarbons to higher alcohols. Before potassium addition, the C support was selective towards methanol and hydrocarbons while the MMO support was predominantly selective towards hydrocarbons. After K addition, the MMO support produced primarily higher alcohols, whereas the C support remained selective towards hydrocarbons with enhanced alcohol selectivity.

1. Effect of Carbon and MgAl Oxide Supports and Potassium Promoter on Higher
Alcohol Selectivity over MoS2 Catalysts during Induction Period
Jin Wai Goh, Micaela Taborga Claure, Christopher W. Jones
Georgia Institute of Technology
Background Selectivity Results
Conclusions
Effect of Support and Promoter on Selectivity
Catalyst Preparation
Lower Olefins (C2-C4) are the key building blocks in the chemical industry
• Primarily produced by steam cracking
• Ethylene is the largest volume petrochemical produced worldwide
• Growing demand for olefins-doubled over the past 15 years1
• Alternative energy sources to olefins needed
Syngas-based processes to olefins include
Higher alcohol (C2-C4) from syngas
• Most widely studied family-noble metal catalyst is Rh
• Modified methanol or modified Fisher-Tropsch catalysts
• Modified MoS2 based catalysts with K
Previous work
• K shifts product distribution from hydrocarbons to higher alcohols2,3,4,5
• K/MoS2 on carbon (C) supports are selective towards hydrocarbons6
• K/MoS2 on mixed MgAl oxide (MMO) supports yield high C2+OH selectivity2,6,7
• K/MoS2 domain was correlated with selectivity (single layes~HC selectivity,
double layers~ C3+OH selectivity)6
Further understand the effect of support and promoter on structure-selectivity
relationship.
Objective
Supported Catalysts
CO hydrogenation reactions with syngas
High pressure (1500 psig)
Medium temperature (310 °C)
(in-situ sulfidation at 450 °C)
Composition
All Catalysts
Mo 5 wt. %
Promoted Catalysts
K 3 wt. %
Mo/K (mol) = 1
• Unsupported MoS2 produced primarily C1 species while
supported MoS2 produced primarily C2+ species.
• K promotion increases the induction period because K
intercalation requires a ‘break-in’ period.5
• Weak Mo-C interactions created single layers on the carbon
support – selective towards hydrocarbons.
• Strong Mo-MMO interactions created double layer formation on
the MMO support – selective towards higher alcohols
(only for K/MoS2).
Future Work
• Investigating absorbed species with in-situ IR
• Investigate the structure of the catalyst via in-situ Raman
and in-situ XAS
References
1H.M. Torres Galvis, K.P. de Jong, ACS Catal. 3 (2013) 2130.
2M.R. Morrill, N.T. Thao, Catal Lett. 142 (2012) 875
3A. Andersen, S.M. Kathmann, J. Phys. Chem. 116 (2012) 1826
4V.S. Dorokhov, D.I. Ishutenko, Kin & Catal 54 (2013) 24
5V.P. Santos, B. Linden, ACS Catal. 3 (2013) 1634
6M.T.Claure, S.H. Chai, J. Catal. 324 (2015) 88
7M.R. Morrill, N.T. Thao, ACS Catal. 3 (2013) 1665
Unsupported Catalysts Mo
C
MMO
K
Unpromoted Promoted
MoS2 Domains
Unpromoted Promoted
• Selective towards hydrocarbons
• Selective towards methane
Unpromoted Promoted
• Selective towards MeOH, followed
by EtOH
• Selective towards C2+OH
• Selective towards hydrocarbons
• Low higher alcohol selectivity
• Selective towards ethane
Predominantly single layer6
Predominantly double layers6,7
Multilayers7
Hypothesized MoS2 domain
Hypothesized MoS2 domain
Hypothesized MoS2 domain
C Mo MoC MoKC
MoMMOMMO
MoC MoKC
bulk MoS2
MoMMO MoKMMO
MoKMMO
K/ bulk MoS2
MoC
Mo
MoKC
MoMMO MoKMMO
Bulk MoS2
K/Bulk MoS2Bulk MoS2
K/Bulk MoS2
MoS2
C
MoS2MoS2
C
MoS2
MMO
MoS2
MoS2
MMO
MoS2
MoS2
K+
MoS2
MoS2
MoS2
MoS2
MoS2
MoS2
MoS2
MoS2
K+