Understanding Change in Process Chemistry

Lead Research Organisation: University of Southampton
Department Name: School of Chemistry


Processes that are used to manufacture or convert materials from one form or state to another are the cornerstone of manufacturing and play a vital part in both the UK and global economy. Within industry, processes, including precipitation, are used to manufacture catalysts for applications such as methanol synthesis, water gas shift, steam reforming and Fischer Tropsch. Other processes, such as wet milling, are used to prepare automotive washcoats and new techniques such as mechanochemistry (dry milling) are also of interest. These processes all involve dynamic change in physical properties (particle size, morphology) and chemical properties (phase, chemical environment) that affect materials over short (ms) and long (hours) timescales and short (nm) and long (micron) length scales. Currently the starting materials and products of these processes can be studied using ex situ techniques, such as XRD or Raman. This is coupled with rheology approaches to model and measure what is happening to the bulk properties of the material during the process itself. However, there is a lack of detailed chemical and physical knowledge of what is actually happening from the point of view of the chemistry in real time. The aim of the project is to join up the different length scales and move towards a description of materials at the atomic/molecular scale from the average properties of bulk materials.

This project will examine and understand process changes by:
- Developing continuous flow methods for the precipitation of metal oxides. Working in flow provides static time points for assessing the chemical events at the molecular level using techniques such as XAFS, SAXS, XRD, and Raman, which allows the approach to bridge both time and length scales.
- Systematic environmental (humidity, atmosphere) investigations of the mechanochemical production of metal oxide phases, both crystalline (XRD) and amorphous (XAFS, PDF).


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Studentship Projects

Project Reference Relationship Related To Start End Student Name
EP/N509747/1 01/10/2016 30/09/2021
1940092 Studentship EP/N509747/1 01/02/2017 31/07/2021 George Tierney
Description We have discovered that by using X-ray absorption spectroscopy (XAS), we can efficiently investigate nanoparticle oxidation state and size in solutions with concentrations as low as 0.05 mM (~6 times more dilute than reported in literature) using X-ray absorption near-edge and extended X-ray absorption fine structures (XANES and EXAFS respectively). This work has also shown that there is an unreported growth stage that occurs between preparation of colloidal solutions (suspended nanoparticles in solution) and the formation of supported nanoparticle catalysts (immobilisation).
During this phase we find that nanoparticle growth occurs independent of other synthesis control parameters, i.e. temperature of reduction, metal concentration, but is due to the acidification of the colloidal metal onto the support surface.
We have also discovered that reduction of HAuCl4 using dimethylamine borane can be measured in situ using XAFS techniques at the Au L3 edge energy.
Variations to the synthetic solvent have also afforded us to recognise that by using methanol as the solvent, we can remove the acidification step in preparing Pd nanoparticle catalysts. Removal of this step does not impact on NP size and results in the production of lower quantities of ether by-products in the hydrogenation of furfural. These by-products have been commonly observed for water only solvent systems, suggesting that methanol plays a role in mitigating hydrogen spillover on the Pd nanoparticles.
Exploitation Route The ability to acquire XAS data of low concentration solutions at specific synchrotron beamlines will be one point of the research that many other groups will find beneficial to their research.
The ability to measure the reduction of Au precursor solutions in situ using XAFS will be of great benefit for further research into understanding the fundamental nucleation and growth steps that occur in nanoparticle preparation.
Sectors Agriculture, Food and Drink,Chemicals,Energy,Manufacturing, including Industrial Biotechology,Pharmaceuticals and Medical Biotechnology

URL https://pubs.rsc.org/en/content/articlelanding/2019/na/c9na00159j#!divAbstract