Diethyl Ether to Reduce Emissions from Diesel Engines

By Jillian Jastrzembski

Introduction

Since we still can’t fully replace diesel engines, researchers look for other ways to reduce emissions. One of the major reduction strategies is the use of biodiesel and other fuel additives – the most important of which is diethyl ether.

If you feel like electric vehicles are already taking over, you may be getting ahead of yourself. The reality is that there are still several barriers to entry preventing people and organizations from converting to electric vehicles. They tend to be more expensive than traditional alternatives, charging stations can still be hard to come by, and they often have limited range.

Diesel fuel is still a great option compared to gasoline, because it reduces dependence on foreign petroleum products. Diesel engines are highly durable and also more efficient than gasoline. That is why they are used to power heavy-duty machines like trucks, trains, boats, and utility vehicles.

So, at least in the immediate future, diesel engines are sticking around – and so, unfortunately, are environmental concerns about emissions. Those emissions include gases like carbon monoxide (CO), carbon dioxide (CO₂), nitric oxide (NO), nitrogen dioxide (NO₂), other nitrogen oxides (NO_x), and unburned hydrocarbons (HC).

Let’s take a step back – what is diesel fuel?

You’ve probably seen signs for it at the gas station plenty of times, but just in case you still don’t know, here’s a crash course.

Diesel is an alternative term for distillate fuel oil, refined from crude oil. There’s also a subset of diesel fuel called biodiesel, refined from biomass materials.

Like gasoline, diesel is usually used to power vehicles, but you can think of it as a more heavy-duty fuel. It is a ubiquitous power source. Not only does it have widespread use in trucks, trains, boats, and construction equipment, but it also used for back-up power generation in large institutions like hospitals, and to generate electricity in remote villages.

Diesel engines operate differently than gasoline engines, resulting in better efficiency. In diesel engines air is compressed, causing it to heat up. The generation of heat from the compressed air is what allows the diesel fuel to ignite. Diesel engines rely on combustion reactions that produce energy to move pistons, which in turn rotate the wheels of the vehicle.

Historically, diesel engines bring to mind dirty, loud trucks emitting plumes of grayish gas. Nowadays many improvements have been made, resulting in lower emissions of almost all pollutants – except for nitric oxides and particulate matter.

Given the mounting concerns about environmental pollution, many laws and regulations are in place to limit the emissions produced by diesel engines.

This becomes particularly relevant under “cold start-up” conditions. When it becomes cold outside, the diesel engine becomes much less efficient. That’s because when there is a significant temperature difference between the air and the fuel, the engine cannot produce a homogenous air-fuel mixture. This results in incomplete combustion, and increased emissions by up to 85%!

What does all of this have to do with diethyl ether?

One of the major strategies for reducing emissions is the use of additives that change the properties of diesel fuel. For example, researchers test different ratios of diesel to biodiesel fuel to determine optimal blends. Increasing the ratio of biodiesel to diesel can reduce emissions, but after a certain point (about a 1:1 ratio), the engine will no longer start.

Other additives include chemicals like ethanol and diethyl ether. Diethyl ether, an isomer of butanol (a four-carbon alcohol, and not a far cry from the more familiar ethanol), is a highly volatile and flammable organic solvent. It also goes by other names like ethyl ether, or simply ether. It is of particular interest as a fuel additive because it has high miscibility with diesel/biodiesel blends.

Scientists add diethyl ether to diesel/biodiesel blends at varying concentrations, and measure the resulting emissions. Adding diethyl ether is shown to significantly reduce certain emissions – even nitric oxides, which have been the most difficult pollutants to mitigate.

As an added bonus, addition of diethyl ether has been found to recover the engine function under high ratios of biodiesel.

Conclusion

Diesel engines remain a valuable and efficient source of power, even with the introduction of electric vehicles. Emissions from diesel engines have been reduced greatly in the past century, but there is still room for improvement. Various nitric oxides and particulate matter remain the most stubborn pollutants to deal with, particularly under inefficient, cold-start conditions. Diethyl ether can be used as a fuel additive to help reduce emissions, and can be used to recover the function of the engine even with high ratios of biodiesel. Diethyl ether is a valuable resource to reduce the environmental impact of diesel engines and national dependence on foreign petroleum sources.

References

Clenci, Adrian, et al. “Impact of Biodiesel Blends and Di-Ethyl-Ether on the Cold Starting Performance of a Compression Ignition Engine.” Energies, vol. 9, no. 4, Apr. 2016, p. 284. Crossref, https://doi.org/10.3390/en9040284.

Roy, Murari Mohon, et al. “Cold start idle emissions from a modern Tier-4 turbo-charged diesel engine fueled with diesel-biodiesel, diesel-biodiesel-ethanol, and diesel-biodiesel-diethyl ether blends.” Applied Energy 180 (2016): 52-65.

Zhang, Xuewen, et al. “Strategies to Reduce Emissions from Diesel Engines under Cold Start Conditions: A Review.” Energies, vol. 16, no. 13, July 2023, p. 5192. Crossref, https://doi.org/10.3390/en16135192.

“U.S. Energy Information Administration – EIA – Independent Statistics and Analysis.” Diesel Fuel Explained – U.S. Energy Information Administration (EIA), www.eia.gov/energyexplained/diesel-fuel/. Accessed 2 Aug. 2023.

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