Environment Scientific Progress
This theme focuses on new applications of catalysis which impact on improving the environment using multi-centre multidisciplinary teams e.g., improve efficiency of catalysed processes and indeed designing new catalysts.
Carbon fibre reinforced composite materials have revolutionised aerospace and automotive industries. It is lightweight with outstanding mechanical performance but damage is difficult to detect and repair. The project aims to design functionality within the composite material to impart autonomous self-healing by incorporating monomer filled microspheres and a complementary polymerisation catalyst into the material. During a damage event, microspheres rupture, releasing monomer which contacts catalyst and heals.
The work has received extensive publicity with articles in the Independent on Sunday, Daily Mail, BBC website, CNN website; and with radio interviews on Radio 5 live, BBC world service; TV: BBC Points west.
Robust synthesis of epoxy resin-filled microcapsules for application to self-healing materials P. A. Bolimowski, I. P. Bond, D. F. Wass 2016. DOI: 10.1098/rsta.2015.0083
We have designed new supported bimetallic nanoparticle redox catalysts for the valorisation of bio-derived platform molecules. The project focused on the valorisation of glycerol to either tartronic acid or lactic acid, via an oxidation or a dehydration pathway respectively, using high surface area lanthanum based perovskites as supports for bimetallic AuPt nanoparticles as catalysts. By changing the B site of the LaBO3 (where B= Cr, Mn, Fe, Co or Ni) we can tailor the reaction pathway to produce either tartronic acid or lactic acid. Our results indicate that support modification to tailor selectivity is a promising approach for designing catalysts for various liquid phase oxidation reactions. The work was patented and then presented at a Faraday Discussion (Faraday Discussions (2016), 188, 427-450) and follow on funding has been supplied by the EPSRC IAA.
Closing the chlorine cycle in large-scale chemical manufacturing processes has been a key aim and a three-stage process is being investigated (see Fig). The proposed process operation has real industrial appeal, as it could be used to close the chlorine cycle in certain large-scale isocyanate manufacturing operations. After considerable effort, an understanding of the fundamental processes has been achieved to determine if the proposed process is viable as a commercial unit operation. Catalysis using an industrial oxy-chlorination catalyst has enabled a qualitative model to be developed that is consistent with the observable catalytic performance.
The breadth of the theme is demonstrated by the project on ‘Artificial metalloenzymes for selective C1 oxidation of alkanes’ where the broad nature of the Hub community has allowed access to techniques including EXAFS for the analysis of the artificial metalloenzymes. The EXAFS results have provided the crucial information to explain the unprecedented behaviour of the rhodium metalloenzyme in the aqueous phase hydroformylation of long-chained alkenes. High selectivity for the linear aldehyde and rate accelerations of 6-7 orders of magnitude are observed compared to comparable chemocatalytic Rh-monophosphine complexes.
We have designed novel catalysts for the reduction of nitrates into nitrites, ammonia and ultimately nitrogen. The most promising catalysts for this reaction is gold supported on titania. Having carried out a detailed study into the various parameters of the preparation of these catalysts we have found that catalysts with very low loadings of gold, prepared by the incipient wetness methodology, are particularly active. These results have been presented at the ICC 2016 in China.
Self-healing Composite Materials have been a key focus with work focused on two areas; the development of an embedded catalyst and microcapsule systems for self-healing of carbon fiber reinforced composite materials, and the discovery of new mechanically-activated catalysts for the same application that should be very stable, allow multiple healing events and re-modeling of the structural material.
The image shows a schematic of composite material fibers and matrix; to right are three monomer-containing microspheres in the process of rupture.
Advances have been made in the first topic in the controlled synthesis of the microcapsule/catalyst system itself (Phil. Trans. R. Soc. A. 2016, 374, 20150083) and in widening the applications of this approach closer to real materials (Smart Mater. Struct. 2014, 23, 115002; Macromol. Mat Eng. 2014, 208; Polymer 2015, 69, 283). The second area requires more fundamental discoveries and studies are at an earlier stage.
Preliminary results using a coordination polymer as catalyst have been promising (Smart Mater. Struct. 2015, 055004) and these results are being built upon. (see also https://www.epsrc.ac.uk/newsevents/news/selfhealingaircraftwings/)
Discussions are also at an advanced stage with several industrial partners (including Dassi bikes, Leidos (autonomous boats), Maserati, Dyson and IHI) to commercialize this technology, either in direct collaboration or via a spin-out company.
A soot-combustion catalyst which can be incorporated into the particulate filter of a diesel car has been studied. Mechanistic studies of our most active catalyst to date, Ag-K/CeO2-ZrO2-Al2O3, indicate that surface carbonates are the oxidising species under exhaust-gas conditions, contrary to the accepted wisdom that both Ag and alkali metals activate oxygen molecules into reactive superoxide species. We have presented our mechanistic results at ICC 2016 in China. We have also started to investigate the possibility of integrating soot-combustion and selective catalytic reduction in a single catalytic unit that would simultaneously target carbon particulate and NOx emissions. Our results indicate that this is a very promising approach, which can lead to a synergy between the two functions, resulting in soot combustion being initiated at an ideal temperature for application on diesel passenger cars. As our results are counter-intuitive, they are due to be reviewed by the Cardiff University Commercial Advisory Panel in October, with a view to patenting the concept.
A new reactor for high pressure methanol synthesis from pure CO2 and H2 has been developed, with a wide range of catalysts being produced Pd/ZnO proves to be an interesting material because, although the material itself is poor for methanol synthesis, when pre-reduced it becomes very selective to methanol. This is due to the formation of a Pd-Zn alloy, supported on ZnO.(Bahruji et al. J. Catal., (2016) doi.org/10.1016/j.jcat.2016.03.017). Catalyst preparation using anti-solvent precipitation has several advantages over conventional preparation methods. We have shown by using supercritical carbon dioxide as an anti-solvent metal/metal oxide catalysts with high surface area, small crystallite size and highly heterogeneous mixing of components can be produced (Hutchings et al., Nature 531, 83–87 (03 March 2016). While the process is highly successful for material discovery the high CO2 pressure required makes the process energy intensive, limiting the techniques practical application. The aim of the current project is to utilise the highly tuneable properties of ionic liquids in the anti-solvent precipitation of heterogeneous catalysts. We have made initial progress on the use of deep eutectic choline chloride solvents to precipitate Cu/ZnO methanol synthesis catalysts. We are investigating switchable solvents to change the polarity/hydrophilicity of solvents to precipitate materials and using ionic liquids as solvents and templates to produce porous materials.
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