Luke Higgins

Transitioning towards a low carbon future requires the development of innovative biorefinery processes capable of sustainably producing fuels and fine chemicals without fossil resources.  Designing an effective, integrated biorefinery relies on developing robust processes for upgrading biomass to fuels and chemicals.  These products include high-value chemicals, such as benzene, toluene and xylenes (BTX), which act as platform chemicals to produce a variety of chemicals and materials. Catalytic fast pyrolysis (CFP) is a highly developed process that can convert woody biomass in a single-step at 400 – 600 °C.  Moreover, the high-quality, low oxygen content bio-oil produced, makes CFP compatible with current refining infrastructure as a drop-in refinery substitute.

Zeolites such as ZSM-5 are known to be effective catalysts for hydrodeoxygenation of lignocellulosic biomass to high value BTX and monoaromatic hydrocarbons.  Recent research has shown that the addition of ca. 1 % wt. Fe to ZSM-5 has a notable impact on the selectivity of the reaction, typically increasing the BTX yields, when compared to non-Fe-modified zeolite.  It is believed that Fe sites in Fe-ZSM-5 zeolite are both selective and active towards monocyclic aromatic hydrocarbon (MAH) formation and suppress further polymerisation and the formation of oxygenates.  Conspicuous by its absence though is an understanding of the nature and role of the Fe species present under real reaction conditions.

The aim of this project is to study the distribution and function of Fe during CFP of biomass.  In the past, the study of these Fe sites has been challenging, due to the relatively low concentration (ca. 1.0 wt%) of Fe present in the zeolite.  This project will exploit the new 14 crystal analyser X-ray emission spectrometer at I20 scanning of Diamond Light Source.to perform operando Resonant X-ray Emission Spectroscopy (RXES) and High Energy Resolution Fluorescence Detection (HERFD) X-ray absorption spectroscopy.  This state-of-the-art instrument, combined with other techniques (e.g., high resolution electron microscopy, X-ray Raman scattering) will enable insight into the mechanisms governing FCP. In particular, it is hoped that RXES will identify active Fe species (e.g., iron carbides).  These results will develop our understanding of the mechanisms occurring during CFP, which could have exciting implications for future biorefinery.

1. Feng, J., Cai, R., Magliocca, E., Luo, H., Higgins, L., Romario, G.L.F., Liang, X., Pedersen, A., Xu, Z., Guo, Z. and Periasamy, A., 2021. Iron, Nitrogen Co‐Doped Carbon Spheres as Low Cost, Scalable Electrocatalysts for the Oxygen Reduction Reaction. Advanced Functional Materials, 31(46), p.2102974.
2. Higgins, L.J., Sahle, C.J., Balasubramanian, M. and Mishra, B., 2020. X-ray Raman scattering for bulk chemical and structural insight into green carbon. Physical Chemistry Chemical Physics, 22(33), pp.18435-18446.
3. Higgins, L.J., Brown, A.P., Harrington, J.P., Ross, A.B., Kaulich, B. and Mishra, B., 2020. Evidence for a core-shell structure of hydrothermal carbon. Carbon, 161, pp.423-431.

Luke Higgins is a post doctoral research associate on I20-scanning. He did his first degree at the University of Kent, then a PhD at the University of Leeds, with Dr B. Mishra as his principal supervisor. He was awarded an  EPSRC Doctoral Prize Fellowship at Leeds after his PhD.