Description:

Speaker: Lauren McCullough, Notestein Lab

Title: Acceptorless Dehydrogenative Coupling of Ethanol over Bulk MoS2 and Spectroscopic Structure-Function Correlations

Abstract
The production of oxygenates such as esters and organic acids from alcohols is an attractive route to high value industrial chemicals. In particular, routes that do not require the addition of oxidants, volatile or toxic reactants, base co-catalyst, or precious metal catalysts are highly desirable [1]. Acceptorless dehydrogenative coupling (ADC) has been commercialized over copper based catalysts [2] but current systems suffer from the requirement that bio-ethanol be dried before introduction to the catalyst bed and from the co-production of aldehydes and ketones requiring re-hydrogenation over a Ru based secondary catalyst. Previous reports have indicated that sulfated Mo/C could be a potentially promising material for this class of reactions [3].

In this work, we demonstrate that nanoparticulate bulk MoS2 is active for conversion of ethanol to ethyl acetate and hydrolysis to acetic acid. In high pressure batch reactions equilibrium yield of ethyl acetate (44%) is achieved in 24 hours at 230oC. Upon addition of water, total acetate yield (ethyl acetate and acetic acid) increases to 82%. MoS2 from a variety sources was tested for this reaction. Structure-function correlations were developed by combining atmospheric pressure flow reactions and material characterization based on x-ray absorption spectroscopy and infrared spectroscopy with CO as a probe molecule [4]. Based on these correlations, it is postulated that formation of ethyl acetate occurs via a hemiacetal intermediate [5] over two sites, a coordinatively unsaturated Mo site for dehydrogenation of ethanol to acetaldehyde, and a basic site (likely an -SH group) for formation of the hemiacetal [6].

This is the first report of ADC on bulk MoS2 as well as the first application of these characterization techniques to a class of reactions outside of the hydrotreating literature.

References:
(1) Sato, A. G.; Biancolli, A. L. G.; Paganin, V. A.; da Silva, G. C.; Cruz, G.; dos Santos, A. M.; Ticianelli, E. A.; Int. J. Hydrogen Energy. 2015, 40, 14716-147222.
(2) Colley, S. W.; Tuck, M. W. M.; Catalysis in Application, 2003, 101-107.
(3) Wang, L. X.; Zheng, D. F.; Ma, C. X.; Zhu, W. C.; Liu, S. Y.; Cui, J.; Wang Z, L.; Zhang, W. X.; Polish J. Chem., 2009, 83, 1993-2000.
(4) Chen, J.; Maugé, F.; El Fallah, J.; Oliviero, L.; J. Catal., 2014, 320, 170-179.
(5) Inui, K.; Kurabayashi, T.; Sato, S.; J. Catal., 2002, 380, 113-117.
(6) Colley, S. W.; Tabatabaei, J.; Waugh, K. C.; Wood, M. A.; J. Catal., 2005, 236, 21-33.

Speaker: Hongda Zhang, Snurr Lab

Title: Computational Study of Natural Gas Storage and Water Adsorption in Metal-Organic Frameworks

Abstract
Metal-Organic Frameworks (MOFs) are a new class of promising nanoporous materials for different applications including gas storage and separation, catalysis, sensor, etc. In this talk, the computational study of natural gas storage and water adsorption in MOFs will be introduced.
Adsorbed natural gas (ANG) has many advantages, including higher safety and lower cost, compared with traditional compressed natural gas storage for vehicular applications. However, in addition to methane, commercial natural gas always contains small amount of impurities including ethane and propane. These higher hydrocarbons are more easily adsorbed by the adsorbents due to their stronger interactions with the adsorbent framework atoms. In order to study the effect of these impurities on the performance of an ANG tank, we combined grand canonical Monte Carlo (GCMC) simulations and macroscopic thermodynamics to develop a model for an ANG tank. With this model, the performance, especially the deliverable energy, of the natural gas storage system with different MOFs can be tested over many operation (adsorption/desorption) cycles. Furthermore, screening of a small MOF database containing 120 structures has been carried out. Based on the screening result, good MOF candidates have been identified, and some interesting trends have been observed.
Water is one of the most common components in industrial gas or liquid systems. It often has a non-negligible effect on chemical and physical processes such as gas or liquid adsorption in porous materials, like zeolites and MOFs. However, the molecular simulation of water adsorption in MOFs always brings many challenges especially the slow simulation speed mainly due to the clustering of water molecules through hydrogen bonds. In this study we selected the hydrophobic MOF ZIF-8 as a representative adsorbent to discover the adsorption mechanism of water. In addition, we proposed and investigated several advanced Monte Carlo algorithms including the energy-bias method and the continuous fractional component Monte Carlo (CFC MC) method and successfully accelerated the simulation speed.