Posted in | Pollution | Sustainability

MIT Researchers Develop New Method for Synthesizing Epoxides Found in Textiles, Plastics, and Pharmaceuticals

Industrial manufacturing of products, like steel, iron, and plastics, is believed to be the greatest source of energy consumption worldwide. This is because large amounts of energy are required to develop these materials and, added to this, a majority of the reactions directly release carbon dioxide (CO2) gas as a byproduct.

MIT researchers used these manganese oxide nanoparticles to catalyze the breakdown of water and the subsequent incorporation of oxygen into useful compounds called epoxides. (Image credit: MIT)

Hence, in order to decrease this energy consumption and the associated emissions, chemical engineers at MIT have developed an alternative method for producing a type of chemical called epoxide. This chemical is used for producing a wide range of products, such as textiles, pharmaceuticals, and plastics. The latest technique utilizes electricity to run the reaction, and it can be performed at atmospheric pressure and room temperature while removing CO2 as a byproduct.

What isn’t often realized is that industrial energy usage is far greater than transportation or residential usage. This is the elephant in the room, and there has been very little technical progress in terms of being able to reduce industrial energy consumption.

Karthish Manthiram, Study Senior Author and Assistant Professor, Department of Chemical Engineering, MIT

A patent on this technique has been filed by the MIT researchers, who are currently exploring ways to enhance the efficiency of the synthesis so that it can be modified for industrial applications on a large scale.

The study was reported online in the Journal of the American Chemical Society on April 9th, 2019. MIT postdoc Kyoungsuk is the study’s lead author. Graduate students Nathan Corbin Joseph Maalouf, and Nikifar Lazouski, and postdoc Dengtao Yang are the other authors.

Ubiquitous chemicals

The main chemical feature of epoxides is a three-member ring containing an oxygen atom adhered to two carbon atoms. Epoxides are used for developing an array of products, including polyester, antifreeze, and detergents.

It’s impossible to go for even a short period of one’s life without touching or feeling or wearing something that has at some point in its history involved an epoxide. They’re ubiquitous. They’re in so many different places, but we tend not to think about the embedded energy and carbon dioxide footprint.

Karthish Manthiram, Study Senior Author and Assistant Professor, Department of Chemical Engineering, MIT

Among the chemicals, many epoxides are associated with the top carbon footprints. In fact, the development of ethylene oxide—a single epoxide—produces the fifth-largest emissions of CO2 of any chemical product.

Many chemical steps are needed to develop epoxides, and a majority of them are highly energy-intensive. For instance, the reaction used for bonding an atom of oxygen to ethylene, generating ethylene oxide, has to be performed at almost 300 °C and also under pressures that are 20 times higher than atmospheric pressure. Moreover, fossil fuels are largely used for powering this kind of manufacturing.

The reaction used for creating ethylene oxide also produces CO2 as a byproduct, which adds to the carbon footprint. This CO2 is subsequently discharged into the atmosphere. A more complicated method is used for producing other kinds of epoxides, but this approach involves the use of calcium hydroxide, which can lead to skin irritation, and toxic peroxides, which can be quite explosive.

Hence, in order to develop a more sustainable technique, the MIT researchers took a cue from a reaction called water oxidation. This reaction utilizes electricity to split water into electrons, protons, and oxygen. The team first decided to carry out water oxidation and subsequently attached the oxygen atom to olefin—an organic compound that acts as a precursor to epoxides.

According to Manthiram, this method was counterintuitive because generally, water and olefins cannot react with one another; however, if an electric voltage is applied, then both can react with one another.

To exploit this condition, the MIT researchers created a reactor with an anode in which water is converted into electrons, oxygen, and hydrogen ions or protons. Furthermore, manganese oxide nanoparticles serve as a catalyst to support this reaction along and also to integrate the oxygen into an olefin to produce an epoxide. Then, electrons and protons travel to the cathode, where they are changed into hydrogen gas.

Thermodynamically, about 1 V of electricity—which is less than the voltage of a regular AA battery—is needed for this kind of reaction, which does not create any CO2 gas. The team believes that the carbon footprint could be reduced further by applying electricity from wind, solar, and other renewable sources to fuel the conversion of epoxides.

Scaling up

To date, the investigators have demonstrated that this process can be used for producing cyclooctene oxide, which is another kind of epoxide, and they are currently exploring ways to modify it to other epoxides. In addition, the researchers are working on ways to make the conversion of olefins into epoxides as efficient as possible—in this analysis, the conversion reaction consumes around 30% of the electrical current, but the team is hoping to double that.

The researchers estimate that if their process is scaled up, then ethylene oxide could be produced at a cost of $900 per ton, in comparison to $1,500 per ton through existing techniques. As the process becomes more efficient, that cost could be reduced further. Yet another aspect that can possibly play a role in the economic feasibility of this method is that it also produces hydrogen as a byproduct, which is considered to be useful in its own right to drive fuel cells.

The investigators are planning to further advance the technology and believe that it would be ultimately commercialized for industrial applications. They are also working on methods in which electricity can be used to produce chemicals of different kinds.

There are many processes that have enormous carbon dioxide footprints, and decarbonization can be driven by electrification. One can eliminate temperature, eliminate pressure, and use voltage instead.

Karthish Manthiram, Study Senior Author and Assistant Professor, Department of Chemical Engineering, MIT

MIT’s Department of Chemical Engineering and a National Science Foundation Graduate Research Fellowship funded the study.

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