The production of chemical feedstocks from plant waste

Computer simulation of supported nano-particle catalysts for the production of chemical feedstocks from plant waste

Liam Thomas

After completing a BSc degree in Chemistry at Bristol University and an MSc in Molecular Modelling at Cardiff University, Liam Thomas joined the Cardiff Catalysis Institute as a PhD student in October 2012, with a studentship funded by Fujitsu. Liam is working with Nextek Innovations Ltd to develop new packaging materials produced from sustainable sources to replace today’s oil-based polymers. According to Liam:

"I decided to pursue this area of research as I can combine my interest in computational modelling with investigation of a real catalytic system. I also hope that my research will contribute to finding greener alternatives to crude-oil based products.”

Almost two million tonnes of plastics are used in the UK packaging industry each year. They are ideally suited for this due to their weight, durability and strength. However, many of today’s most widely used plastics (e.g. polyethylene terephthalate (PET) or terephthalic acid (PTA)) have a detrimental impact on the environment as they are generally derived from oil, have a relatively short useful life and do not degrade quickly once they are discarded. This has resulted in a drive to develop new forms of biodegradable plastics that can be manufactured from renewable resources.

Nextek are targeting the use of 2,5-furandicarboxylic acid (FDCA) as a green replacement for PTA. They believe that it will be possible for plastics based on FDCA to be produced at a similar cost to PTA via the oxidation of hydroxymethylfurfural (HMF), which is present in food waste (a renewable source). This makes FDCA an attractive replacement for PTA.

Using traditional oxidation techniques to produce FDCA may be harmful to the environment, so Nextek are investigating a new method known as heterogeneous catalysis, which uses a complex mixture of very small (~10-9 m) precious metal nanoparticles and oxide materials (called support) to enable the reaction. The exact mechanism for the reaction is not well understood – especially the influence of the metal/support region.

As Nextek had little experience with using high performance computing prior to this project, Liam is responsible for interacting with their researchers in order to establish how the use of this technology can assist in their work and benefit their business.

His project aims to investigate computationally the mechanism for the oxidation of HMF using supported nanoparticles by running a series of simulations on HPC Wales’ systems.

So far, Liam has obtained a good model of the titanium dioxide support used within the catalysis reaction, and has investigated the reaction mechanism when unsupported clusters of gold nano-particles are used to catalyze the HMF to FDCA reaction.

His simulations show that HMF adsorbs favourably to clusters of gold nano-particles of any size. However, small clusters (e.g. Au13 – clusters of 13 atoms) show more flexibility than larger clusters (e.g. Au38). This may have implications for Nextek as cluster flexibility can affect the efficiency of the oxidation reaction.

HPC Wales provides Liam with access to much more computing power than would be available to him within the university, enabling him to provide research results much faster. He uses the wide range of chemistry packages available on the system to run a suite of computational tests (each of which may run for days) on the nano-particle catalysts. These include geometry optimizations, nudged elastic band calculations, molecular dynamics simulations and memory-demanding CCSD(T) simulations using Molpro.

The multi-tiered nature of the system allows Liam to spread his tests across the most appropriate computers (located in both Cardiff and Swansea), maximizing his use of the resources and allowing him to respond to questions from Nextek much quicker than before. As he explains:

“The computational resources HPC Wales provides are excellent, enabling the study of large systems which would not be possible on smaller machines. The technical support provided has enabled this research to be performed with ease, whereas I do not know that it would have been possible without the availability of HPC Wales”

Liam plans to run further simulations in order to determine the optimal cluster size and geometry for the adsorption and oxidation of HMF, as well as extend his investigation by considering the use of other metal nano-particles (such as platinum or silver); the impact of using a support on the oxidation reaction (such as the titanium dioxide he already has a model for); and the inclusion of a solvent in his simulations to investigate the role of water.

Nextek are benefiting from Liam’s use of HPC Wales’ services by achieving research results faster than before, helping them to innovate in a very competitive area. The aim of providing a more sustainable lifestyle for all through the creation of new, environmentally friendly food and drink packaging contributes to the green agenda for Wales and the wider economy.

 

 

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