|Professor Alan Chaffee|
|BCIA Research Leader Fellowship|
|By Prof. Alan Chaffee, School of Chemistry, Monash University|
|“I was delighted to have the opportunity to take up a BCIA Research Leader Fellowship and it provided an opportunity to pursue a number of research themes under the title ‘New markets and greener approaches to brown coal use’.”|
|BCIA Research Leader fellowships are awarded to outstanding researchers of international repute who can provide a significant leadership and mentoring role, and build Australia’s internationally-competitive research capacity. |
With Alan Chaffee’s fellowship now complete, he provides a review of the work undertaken.
The programme sought to address issues that impede the broader use of Victorian brown coal (VBC) and to facilitate its utilisation in new markets, along four major themes.
- Understanding spontaneous combustion.
- Transformation of brown coal into high value products.
- Coal and coal derived materials as adsorbents.
- CO₂ capture and utilisation.
|The research focus was on ‘applied science’ – looking to generate outcomes that could be used in subsequent process development work by engineering groups. The programme also emphasised activities that offered improved environmental outcomes, including reduced energy consumption and the recovery or utilisation of associated CO₂ emissions. I have briefly described some of the highlights of the programme below.|
Although spontaneous combustion has been widely studied, the physico-chemical factors that influence its rate have been poorly characterised. Also, because VBC is heterogeneous, this has compromised comparisons between prior studies.
A significant new finding from our work was the identification of an inverse relationship between the volume of micropores present in the coal and the so-called critical ignition temperature, Tcr. Thus, when the micropore volume was reduced, for example by some dewatering methodologies, the propensity for spontaneous combustion was also reduced.
VBC is potentially a low-cost carbonaceous precursor to a variety of higher value products. We have investigated methods for making materials, such as blast furnace coke substitute, active carbon products and also road bitumen. This work has been quite successful and has led to the development of valuable IP in the former two cases and we are looking to take this further. Studies of liquefaction of VBC in comparison with various forms of biomass led to new understanding about the chemical mechanisms involved.
|In other work we identified a novel means of extracting coal using ‘metastable’ ionic liquids formed from the condensation of CO₂ and various low molecular weight amines. In certain cases these ionic liquids can extract as much as 70% of the coal.|
The ionic liquid can be recovered as its constituent gases by simply heating the liquid to a mild temperature (~60C). This approach can be selective for specific types of molecular structures (such as triterpenoid components) under certain conditions. We are considering possible ways to take this forward.
|Figure 1: Analysis of coal oxidation pathways.|
|Adsorbents from Brown Coal|
|In a substantial programme on new materials for CO₂ capture we developed a composite amine / silica material that has also been patented. This material is prospective for adsorption based CO₂ capture from flue gas streams using a vacuum-swing adsorption (VSA) process configuration. Other materials were identified that have potential for CO₂ capture from synthesis gas at elevated temperatures in a pre- combustion context.|
Active carbons prepared from VBC have abundant micropores and this makes them excellent adsorbents for small molecules. We have investigated their ability to store hydrogen and methane as well as CO₂. The electrical conductivity of carbons gives them a distinctive capability for use in a process configuration known electrical swing adsorption (ESA) and this is the subject of an on-going study with a consortium of European collaborators from industry and academia.
|The direct conversion of CO₂ into commodity chemicals, such as methanol, by gas phase heterogeneous catalysis is also being investigated. In this study we are applying both conventional catalysts and novel ones based on a relatively new class of materials known as metal-organic frameworks (MOFs). MOFs are also prospective for CO₂ capture. This approach requires the use of hydrogen from a renewable source to assist the mitigation of CO₂ emissions associated with fossil fuel utilisation.|
|The fellowship provided the opportunity to collaborate with many groups both domestically and internationally. We hosted international exchange researchers from Canada, China, Germany, Japan and Spain who came here to learn of our approaches to utilising VBC.|
There were several reciprocal visits by group members that provided opportunities to utilise unique facilities in overseas laboratories and to present our work at international conferences. The fellowship also provided a platform that helped foster funding from other sources. The programme was leveraged with funding from a range of industry and government sources.
Although I will not name them here, I want to record my heartfelt appreciation to my collaborators, staff and students who worked with me through this period. It is their ideas, their enthusiasm and their hard work that has enabled the outcomes and advances we have made.
|Figure 2: Molecular structure of MIL-53, a ‘flexible’ metal organic framework (MOF) material of interest for CO₂ capture. The pores of this MOF have the unusual ability to open or close in response to the gas atmosphere to which they are exposed.|
|Figure 3: This image displays the predicted electrostatic charge distribution over the internal surface of the porous metal organic framework (MOF) material known as ‘Mg-MOF74’. Orange shading indicates areas of high positive electrostatic potential where CO₂ will selectively adsorb.|