Presentation Title

Mechanistic Investigation into Molybdenum-Catalyzed Deoxydehydration Reactions

Faculty Mentor

Alex John

Start Date

17-11-2018 8:45 AM

End Date

17-11-2018 9:00 AM

Location

C327

Session

Oral 1

Type of Presentation

Oral Talk

Subject Area

physical_mathematical_sciences

Abstract

Although fossil resources comprise a large portion of global energy production, these hydrocarbon resources are finite and have detrimental effects upon the environment when utilized, thus leading to an increased need for discovering a more sustainable source of chemicals. One promising avenue in the search for a renewable chemical feedstock is biomass, as it is a byproduct of many industrial practices. However, biomass contains numerous oxygen-containing functional groups, therefore posing a challenge in turning biomass into hydrocarbon feedstocks. A promising solution to this dilemma is the deoxydehydration (DODH) reaction, which essentially removes oxygen and water to convert biomass into hydrocarbons. Previous research on DODH has mainly revolved around rhenium (Re) as the catalyst, but despite high yields, its low abundance and high costs make Re an impractical catalyst for larger scale production. Another metal that has the capability to catalyze DODH is molybdenum (Mo), which is more cost-friendly, yet does not have as high yields and requires harsher conditions. Our research group has explored various molybdenum complexes to determine structure-function relationships based upon sterics, electronics, and flexibility. In order to successfully quantify the differences in catalysis on a more mechanistic level, it is imperative to first develop a feasible method to study reaction kinetics. Trends in substrate potential and the manipulation of reaction conditions will be discussed, in addition to findings from initial kinetic studies conducted.

Summary of research results to be presented

With the high temperature constraints for the deoxydehydration (DODH) reaction, a typical NMR machine could not be utilized for data collection. Our laboratory group explored various methods for kinetic studies, such as high-pressure reactors and low pressure/vacuum NMR tubes. The thick glass of the high-pressure reactors caused an initial lag in catalysis, and the NMR tubes resulted in sensitivity to temperature fluctuations. Nonetheless, it was determined that the NMR tube method was a more reliable system for collecting kinetic data when conditions were modified to accommodate the temperature sensitivity. Previous DODH involving molybdenum (Mo) catalysts have demonstrated yields of approximately 55% after running the reaction overnight, whereas our laboratory group was able to obtain comparable results in a shorter time, ranging from 3-5 hours, as supported by preliminary kinetic data. The difference between two reductants, triphenylphosphine and sodium sulfite, will also be reviewed, in which they demonstrated comparable results in terms of yields. Furthermore, the efficacies of four different substrates will be highlighted, and the two most reactive will be compared at a lower temperature. The approximate yields were 10% and 45%, whereas under normal conditions yields reached to roughly 45% and 75%, respectively, therefore showing some sort of temperature dependency, as well as allowing new kinetic studies to be run based upon temperature.

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Nov 17th, 8:45 AM Nov 17th, 9:00 AM

Mechanistic Investigation into Molybdenum-Catalyzed Deoxydehydration Reactions

C327

Although fossil resources comprise a large portion of global energy production, these hydrocarbon resources are finite and have detrimental effects upon the environment when utilized, thus leading to an increased need for discovering a more sustainable source of chemicals. One promising avenue in the search for a renewable chemical feedstock is biomass, as it is a byproduct of many industrial practices. However, biomass contains numerous oxygen-containing functional groups, therefore posing a challenge in turning biomass into hydrocarbon feedstocks. A promising solution to this dilemma is the deoxydehydration (DODH) reaction, which essentially removes oxygen and water to convert biomass into hydrocarbons. Previous research on DODH has mainly revolved around rhenium (Re) as the catalyst, but despite high yields, its low abundance and high costs make Re an impractical catalyst for larger scale production. Another metal that has the capability to catalyze DODH is molybdenum (Mo), which is more cost-friendly, yet does not have as high yields and requires harsher conditions. Our research group has explored various molybdenum complexes to determine structure-function relationships based upon sterics, electronics, and flexibility. In order to successfully quantify the differences in catalysis on a more mechanistic level, it is imperative to first develop a feasible method to study reaction kinetics. Trends in substrate potential and the manipulation of reaction conditions will be discussed, in addition to findings from initial kinetic studies conducted.