The Anonymous Widower

Microwaves Could Turn Plastic Waste Into Hydrogen Fuel

This headline from this article in The Times could be the headline of the day!

Although thinking about it, it wouldn’t be a good idea to put all your plastic waste in the microwave and switch it on. It might catch fire or even worse create lots of hydrogen in your kitchen, which could be followed by a mini-Hindenburg disaster in the kitchen.

These are the introductory paragraphs.

From the yellowed bottles in landfill to the jellyfish-like bags clogging the oceans, plastics pollution is an apparently intractable problem.

Yet, chemists lament, it shouldn’t be. Within this waste there is something extremely useful, if only we could access it: hydrogen. Now a British team of scientists believes it has found a way to get at it, and do so cheaply, thanks to tiny particles of iron and microwaves.

If their system works at scale they hope it could be a way of cheaply converting useless plastic into hydrogen fuel and carbon.

Don’t we all want to believe that this impossible dream could come true?

Some Background Information

Some of the things I talk  about will be technical, so I will have a bit of a preamble.

Hydrogen; Handling And Uses

Because of pre-World War Two airships, which tended to catch fire and/or crash, hydrogen has a bad reputation.

I used to work as an instrument engineer in a hydrogen plant around 1970. To the best of my knowledge the plant I worked  in is still producing  hydrogen in the same large building at Runcorn.

Hydrogen is one of those substances, that if you handle with care, it can be one of the most useful elements in the world.

It is a fuel that burns creating a lot of energy.

The only by-product of hydrogen combustion is steam.

It is one of the feedstocks for making all types of chemicals like ethylene, fertilisers, ammonia, pharmaceuticals and a wide range of hydrocarbons.

Hydrogen is a constituent of natural gas and in my youth, it was a constituent of town gas.

Hydrogen and hydrocarbons are involved in the manufacture of a lot of plastics.

In the future, hydrogen will have even more uses like making steel and cement, and powering railway trains and locomotives, and shipping of all sizes.

Hydrocarbons

According to Wikipedia, hydrocarbons are compounds consisting entirely of atoms of hydrogen and carbon.

In a kitchen, there are several hydrocarbons.

• If you cook by gas, you will probably be burning natural gas, which is mainly methane, which is a hydrocarbon
• Some might use propane on a barbecue, which is another hydrocarbon.
• I suspect you have some polythene or polyethylene, to use the correct name, in your kitchen. This common plastic is chains of ethylene molecules. Ethylene is another hydrocarbon.
• There will also be some polypropylene, which as the name suggests is made from another hydrocarbon; propylene.

Hydrocarbons are everywhere

Plastics

I used to work in two ICI divisions; Mond at Runcorn and Plastics at Welwyn Garden City

• The forerunners of ICI Mond Division invented polyethylene and when I worked at Runcorn, I shared an office, with one of the guys, who had been involved before the Second World War. in the development of polyethylene.
• Plastics Division used to make several plastics and I was involved in various aspects of research plant design and production.

One day, I’ll post in this blog, some of the more interesting and funnier stories.

Many plastics are made by joining together long chains of their constituent molecules or monomer.

• Ethylene is the monomer for polyethylene.
• Propylene is the monomer for polypropylene.
• Vinyl chloride is the monomer for polyvinylchloride or PVC.

So how are the chains of molecules built?

• Polyethylene was made by ICI. by applying large amounts of pressure to ethylene gas in the presence of a catalyst.
• They used to make polypropylene in large reaction vessels filled with oil, using another catalyst.

I suspect both processes use large quantities of energy.

Catalysts

A catalyst is a substance which increases the rate of a chemical reaction.

Judging by the number of times, I find new catalysts being involved in chemical reactions, the following could be true.

• There are processes, where better catalysts can improve yields in the production of useful chemicals.
• There is a lot of catalyst research going on.

Much of this research in the UK, appears to be going on at Oxford University. And successfully to boot!

Velocys

It should be noted that Velocys was spun out of Oxford University, a few years ago.

• The company appears to have improved the Fischer-Tropsch process.
• They are building a waste-to-aviation biofuel plant in Lincolnshire.
• They are backed by British Airways, Shell and UK plc.

This infographic shows their process.

This could be a route to net-zero carbon aviation and heavy haulage.

The beauty is that there would need to be little modification to existing aircraft and trucks.

Oxford University’s Magic Process

These paragraphs from The Times article explain their process.

The clue came in research on particles of iron, and what happens when they get really small. “There’s a fascinating problem,” Professor Edwards said. “You take a bit of metal, and you break it into smaller and smaller bits. At what stage does it stop behaving like a copy of the bigger bit?”

When the particle gets below a critical size, it turns out it’s no longer a metal in the standard sense. The electrical conductivity plummets, and its ability to absorb microwaves does the reverse, increasing by ten orders of magnitude.

Professor Edwards realised that this could be useful. “When you turn on the microwaves, these things become little hotspots of heat,” he said. When he put them in a mix of milled-up plastic, he found that they broke the bonds between the hydrogen and carbon, without the expense and mess of also heating up the plastic itself.

What is left is hydrogen gas, which can be used for fuel, and lumps of carbon nanotubes, which Professor Edwards hopes might be of a high enough grade to have a use as well. The next stage is to work with industry to find ways to scale it up.

It sounds rather amazing.

Going Large!

This article from The Times on Friday, is entitled Plastic To Be Saved From Landfill By Revolutionary Recycling Plants.

These are the two introductory paragraphs.

Thousands of tonnes of plastic waste will be turned into new plastic in Britain rather than dumped in landfill sites, incinerated or sent overseas under plans for four new plants that will use cutting-edge recycling technology.

Up to 130,000 tonnes of plastic a year will be chemically transformed in the facilities, which are to be built in Teesside, the West Midlands and Perth.

It all sounds like technology, that can transform our use of plastics.

Conclusion

In the years since I left Liverpool University in 1968 with a degree in Electrical and control Engineering, it has sometimes seemed to me, that chemistry has been a partly neglected science.

It now seems to be coming to the fore strongly.

October 19, 2020 Posted by AnonW | Hydrogen | Chemical Catalyst, Chemistry, Energy From Waste, ICI, Innovation, Landfill, Oxford University, Polythene, Shell, Velocys | 4 Comments