A research team at the University of Limerick has come up with a new class of sponge that can soak up impurities in a chemical process, desalinate water and mop up carbon dioxide right out of the atmosphere.
This is no sponge you might use to clean a counter top or wash the car, it is a rigid crystalline material that can trap contaminants, explains Prof Michael Zaworotko who leads the UL research group that developed the sponge.
Originally Prof Zaworotko thought he was making a sieve but in reality it ended up working like a sponge.
"That is the fun part. We had a really really good plan but it failed," he said. The original plan was to develop a sieve that could help separate a waste material acetylene from a process to produce ethylene.
The idea was you create sieve holes that let the ethylene through while trapping the acetylene. "It is called size exclusion," says Zaworotko, a Science Foundation Ireland research professor and Bernal Chair of Crystal Engineering at UL.
But the failure turned into a success, and one that could potentially save billions of euro worth of energy.
“You need a precise size for holes in the sieve and we thought we had them. But the larger holes worked much better because the larger holes had binding sites for acetylene.”
In effect the ethylene passes through the material developed at UL and the acetylene binds to sites inside the structure. Once the ethylene clears the sieve the acetylene can then be extracted.
The fact that his material is capable of trapping acetylene has huge financial implications. Ethylene is a primary feedstock for all sorts of plastics such as polyethylene and is one of the largest single chemical processes in the world.
Getting the acetylene out of the process requires large amounts of energy. Processes such as distillation can do it but the energy load required is enormous.
“If you do the maths there is 150 million tonnes of ethylene produced every year and two to three million tonnes of acetylene which is waste material now. “You need huge improvements in purification. The approach we take can cut the energy cost of separating the two materials by 90 per cent,” says Zaworotko.
The nice thing is the sponge - actually a crystalline material - allows you to recover the acetylene which is itself a useful product used in a number of ways including as a fuel and in oxy acetylene welding.
“In a way this was a glorious failure, where the outcome was so much better than expected,” he says.
UL worked on the project as part of an international research team that includes researchers in the US and in China.
Prof Zaworotko leads the Crystal Engineering Research Group at UL that includes nine post doctoral researchers and 10 postgrads. He also has ongoing collaborations within the university with three other faculties.
Prof Zaworotko has a track record in the use of purpose built crystalline structures to trap chemical substances.
"The work is in an area called crystal engineering. Instead of randomly screening material we design new materials."
He has already produced a crystalline material for the collection of carbon dioxide. “It is not yet a major industrial process but it will be. Carbon dioxide has a value, with an important one in agriculture, he says.
“What we want is to capture carbon from the air and then use it where you want to use it. That is something we are independently working on.”
Commodity purification currently accounts for between 10 and 15 per cent of the world’s energy consumption. His group believes the US alone could save 100 million tonnes of carbon dioxide emissions and in the process save €3.6 billion in energy costs annually.
“We have leapt forward, it is not a small change. It really is a better mouse trap,” Prof Zaworotko says.
"We use a process called self assembly. Crystal engineering is a little like being an architect. We try to construct crystals with particular features. If you use the wrong building blocks you will not get the correct reaction. It is not just having the right ingredients they have to function correctly.
He and his group have identified 10 international processes where UL’s sieves can be used to reduce the energy demand.
“We are going down the list. We picked the biggest ones first but there are about 10 other major applications where this approach would work.”
He believes that this will become the norm in purification processes.
His team is now looking at its use in the pharmaceutical industry where refinement of chemical substances must be highly regulated. It is no accident that UL hosts the Pharmaceutical Manufacturing Technology Centre, he says.
“Think of the world’s most valuable substances. Pound for pound it is in pharma and crystal engineering can make better drug products.”
Prof Zaworotko collaborated on the acetylene research with Dr Kai-Jei Chen, one of his post doctoral researchers.
