Better together: a novel bimetallic catalyst for the efficient processing of biomass

17-03-2015

Wenhao Luo, Meenakshisundaram Sankar, Pieter Bruinincx and Bert Weckhuysen from the Debye Institute for Nanomaterials Science in Utrecht, together with Andrew Beale (UCL, UK) and Qian He & Christopher J. Kiely (Lehigh University, Pennsylvania, USA) have developed a successful catalyst for a crucial intermediate stage in the transformation of lignocellulose-based biomass into renewable fuels and chemicals. Extended X-ray Absorption Fine Structure (EXAFS) measurements performed at the ESRF on BM26A and BM23 played a crucial role in determining the nature and location of the catalytically active sites.

  • Share

The modern world is built on crude oil, important both as fuel and as raw material for plastics. However we all know that the use of crude oil is unsustainable, because of its impact in global warming and its finite quantity. Consequently significant effort is being made to find ways to convert renewable resources such as agricultural or forestry waste (biomass) into useable oil. It has so far proved difficult to make the chemistry of the process fast and efficient.  The work reported today represents an important advance.

 

The key is a newly developed catalyst which results in a greater yield of valuable chemical building blocks from biomass and also in fewer by-products and therefore less waste. A patent has been applied for. The results are reported in Nature Communications (doi:10.1038/ncomms7540).

 

The EXAFS measurements played a crucial role in determining the key to high catalyst efficiency.

 

By 2050, some three-quarters of the world’s population will be living in cities. The growing number of cities with over a million inhabitants is demanding closed carbon loops (renewable energy) for a sustainable environment. Chemical building blocks derived from biomass (such as straw, foliage and wood) can form a significant contribution to the increasing demand for “green” materials and fuels. During the processing of biomass, a select number of chemical building blocks form that serve as the basis for the production of a wide range of renewable chemicals such as plastics, fuels and solvents. To obtain these intermediate products in high yield and to ensure their proper conversion, catalysts are crucial.

 

Levulinic acid is one of the most important intermediary products of the processing of cellulose, a component of plant material. By means of catalytic conversion, this product is transformed into a different “green” building block γ-valerolactone. The new and reusable catalyst enables a much quicker and more efficient process of converting biomass-derived levulinic acid into γ-valerolactone – and it also produces less waste.

 

The catalysts used are often metals such as gold, palladium and ruthenium supported on titanium dioxide. These researchers tested combinations of metals which are known to alloy easily. Alloying enables the structure/electronic properties of the metallic nanoparticles to be tuned to optimise the catalytic activity. They found that one of the alloys, Ru-Pd (ruthenium-palladium), controls the desired conversion both very quickly and very specifically. Data from DUBBLE helped explain why.

 

Optimal performance is controlled by the nanoparticle size and the metal distribution within it. This structural information was determined by combining Fourier-Transform Infra-Red (FTIR), X-ray Photoelectron Spectroscopy (XPS), Scanning Transmission Electron Microscopy (STEM) and EXAFS data, but it was the application of EXAFS in particular, recorded at both BM26A and BM23 at the ESRF and at both edges in the bimetallic samples, that allowed a detailed structural model of the active catalyst to be obtained. The researchers were able to conclude that the active nanoparticles are some 1.5 nm in size and form random alloys. Crucially they were able to determine that the key to super-efficiency in Ru-Pd is a high degree of Ru dispersion in the Pd matrix.[2]

 

--------------------------------------------------------------------

 

More information

 

Contact:

Pieter Bruijnincx (+31 (0)6 2273 6354; email: p.c.a.bruijnincx@uu.nl) and Bert Weckhuysen (+31 (0)30 253 4328; email: b.m.weckhuysen@uu.nl)

 

References

[1] M. Sankar, N. Dimitratos, P. J. Miedziak, P. P. Wells, C. J. Kiely, G. Hutchings, Chem. Soc. Rev. 41, 8099 (2012).

[2] W. Luo, M. Sankar, A. M. Beale, Q. He, C. J. Kiely, P. C. A. Bruijnincx, B. M. Weckhuysen, Nature Commun. 6, 6540 (2015).

 

Principal publication and authors

Wenhao Luo (a), Meenakshisundaram Sankar (a), Andrew M. Beale (a,b,c), Qian He (d), Christopher J. Kiely (d), Pieter C. A. Bruijnincx (a), Bert M. Weckhuysen (a), High Performing and Stable Supported Nano-Alloys for the Catalytic Hydrogenation of Levulinic Acid to γ-Valerolactone, Nature Communications, 6: 6540 DOI: 10.1038/ncomms7540 (2015).

 

  1. Inorganic Chemistry and Catalysis, Debye Institute for Nanomaterials Science, Utrecht University, Universiteitsweg 99, 3584 CG Utrecht, The Netherlands.
  2. UK Catalysis Hub, Research Complex at Harwell, Rutherford Appleton Laboratory, Oxfordshire OX11 0QX, UK.
  3. Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, UK.
  4. Department of Materials Science and Engineering, Lehigh University, 5 East Packer Avenue, Bethlehem, Pennsylvania 18015, USA

 

Patent reference

 

Wenhao Luo, Meenakshisundaram Sankar, Pieter C. A. Bruijnincx, Bert M. Weckhuysen, Supported Monometallic and Bimetallic catalysts for the Hydrogenation of Levulinic Acid, Patent application PCT/NL2014/050569

 

Top image: the platform molecule ​levulinic acid (which can be produced easily from the carbohydrate fraction in lignocellulosic biomass) is converted into the useful chemical ​γ-valerolactone using a bimetallic nanoparticulate catalyst