Remarkably Efficient Microwave-Assisted Cross-Metathesis of Lipids under Solvent-Free Conditions

Significance Statement

The vast majority of raw materials used nowadays in chemical industries come from fossil fuels and only about 10% of the feedstock can be traced to renewable resources. In view of the dwindling fossil fuel resources as well as the ever-rising need for sustainability, chemical industries and academia have grown interest in the development of fuels, materials, and chemicals from renewable resources. For this reason, to realize a more sustainable economy, the shift from petro-refinery to bio-refinery is of utmost importance.

To be more precise, the transformation of vegetable oils, reference to their low cost, large-scale availability, and biodegradability, has received renewed research attention. Above their large-scale availability, an array of products can be obtained from seed oils making them good fit for biorefinery as environmentally friendly alternative. For the conversion as well as formation of new carbon-carbon double bonds, olefin metathesis is a versatile synthetic formation tool, which has been applied for both pure and applied chemistry.

Olefin metathesis reactions have been classified into cross-metathesis, ring opening and ring closing. Cross-metathesis is becoming a standard approach with a number of industrial uses such as Shell higher olefin process. Unfortunately, the selectivity of ruthenium complexes for the synthesis of α-olefins from renewable seed oils has been identified as poor. A number of research works have focused on the conversion of plant-oil-derived fatty acids into useful products using ethenolysis chemistry.

Irrespective of the considerable improvements in the metathesis, there is still the desire for solvent-free rapid conversion of plant oils into preferred terminal olefins for the effective transformation of plant oils into downstream products. Aman Ullah and Muhammad Arshad at the University of Alberta developed a microwave assisted ethenolysis as well as alkenolysis technique by applying ethylene as well as a diolefin under microwave irradiation conditions. This was aimed at rapid and efficient conversion of canola oil along with mixtures of canola methyl esters as well as recycled cooking oil into linear α-olefins under solvent-free metathesis conditions. Their research work is published in ChemSusChem

The application of the microwave electromagnetic radiation for the cross-metathesis of vegetable oils and fatty esters of vegetable oils with 1,5-hexadiene and ethylene led to an increase in conversion rates, turnover numbers and turn-over frequencies in a short reaction duration under solvent-free conditions and low catalysts concentrations. Ethenolysis of canola oil methyl esters and recycled cooking oil provided better results. Out of the four catalysts, Hoveyda–Grubbs catalyst 2nd generation was identified to be the most effective at 50 °C, providing effective conversion with better yield as well as selectivity in a majority of cases for ethenolysis and alkenolysis reactions.

The authors achieved high turnover frequency values of 19110/min for direct ethenolysis of canola oil, 10900/min for the cross metathesis of 1,5-hexadiene, 21450/min for ethenolysis of canola methyl esters, and 15840/min for ethenolysis of recycled cooking oil methyl esters. The authors also performed ethenolysis of methyl oleate for comparison with recycled cooking oil methyl esters and canola methyl esters. They realized the highest turnover frequency value for the ethenolysis of methyl oleate.

The outcomes of their study demonstrated that microwave-assisted conversion of renewable oils together with their fatty acid derivatives is a promising as well as a rapid process for the synthesis of a number of materials for use in chemical industries.

Microwave-Assisted Cross-Metathesis of Lipids under Solvent-Free Conditions-Advances in Engineering

About The Author

Dr. Aman Ullah received his PhD (with distinction) in Chemical Sciences and Technologies in 2010 at the University of Genova, Italy by working together at Southern Methodist University, USA. He worked as a postdoctoral fellow before accepting an academic position at the Department of AFNS, University of Alberta. He has recently developed and is teaching a new graduate course entitled “Renewable Biomaterials”. This course deals with fundamentals in bio-based materials development, characterization, and various industrial applications. Current research, recent literature, and real-life applications of biomaterials/bionanomaterials in various industries are discussed throughout the course. Aman has published more than 40 papers in reputed journals and 3 patents/patent applications. He was named a Canadian Rising Star in Global Health by Grand Challenges Canada in 2012.

His current research interests are on the synthesis of monomers, biopolymers, nano-engineered biopolymers, nano-biocomposites and bioconjugates from lipids and other renewable resources for various applications. More specifically his research is focused on: (1) the development of renewable monomers from lipids and preparation of biopolymers and biopolymer based nanocomposites for high performance industrial applications, (2) utilization of lipids and protein biopolymers for the preparation of bioconjugates and nano-structured biomaterials for water remediation and biodegradable packaging, (3) development and nano-modification of lipids for therapeutic and cosmetic applications. Renewable block co-polymers as nano-carriers for drug delivery applications

About The Author

Muhammad Arshad received his master degree in chemistry from Islamia University of Bahawalpur and PhD (chemistry) at the University of Karachi, in Pakistan. He is currently working as a Post-Doctoral Fellow at University of Alberta. During his PhD program he won a prestigious, six months Canadian Commonwealth Scholarship to come to the University of Alberta for a work term. He also won one year post-doctoral fellowship from LRIGS, University of Alberta. His future plans involve continued work to find ways to apply chemistry to help solve some of the myriad of environmental challenges that exist in the world.

Reference

Aman Ullah and Muhammad Arshad. Remarkably Efficient Microwave-Assisted Cross-Metathesis of Lipids under Solvent-Free Conditions. ChemSusChem 2017, 10, 2167 – 2174.

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