Chau Hoang

Catalytic valorisation of humin-based by-products from biomass processing for production of sustainable synthesis gas/H2

Promotion date: July 18.

Promotor: Prof. dr. Kulathuiyer Seshan
Prof. dr. ir. Leon Lefferts

Lignocellulosic biomass is addressed as the only carbon containing sustainable alternative resource for our needs towards chemicals and fuels. Biorefinery concepts are proposed for making energy, fuels and chemicals from different components of biomass. Here, the conversion of (hemi)celluloses is important since they comprise 70 – 80 wt.% of biomass.

Furans (HMF, FF, FDCA) and levulinic acid (LA) are in the list of Top Ten value added platform molecules from carbohydrates. The conversion of carbohydrate to these molecules requires de-polymerisation of polysaccharides to sugar monomers and dehydration of the corresponding sugar to HMF, FF or LA. One of the major problems in such conversions is the formation of large amounts of solid by-products, named humin.

In order to achieve a breakthrough, valorisation of humin by-products should be taken into account, to improve the economic value and environmental factor of this bio-process. Upgrading, however, demands large amounts of hydrogen. Therefore, the approach for producing hydrogen from humin is attractive.

The potential of humin for gasification to produce sustainable hydrogen/synthesis gas is investigated. The fundamental study on the chemical structure of humin as well as its characteristics during the gasification is elucidated. A chemical structure of humin segments was proposed, using spectroscopy and pyrolysis data. It was found that in the first stage of gasification humin turns from a dense towards a porous structure. Also it is essential to employ catalysts in order to improve the reaction rate, reduce the gasification temperature and thus the energy input into the process.

The whole process of humin gasification was studied. Humin is a potential carbonaceous material for producing sustainable hydrogen. These findings can also contribute to gasification of a wider bio-derived feedstock range (e.g., lignocellulose, bio-oils).

What was your personal incentive for investigating ‘humin’ during your PhD project?

I chose this topic right from the beginning. Despite being a major waste with high yield in conversion of carbohydrate, our knowledge about humin is very limited, and valorization of humin via catalytic routes (including gasification) for making chemicals and energy is a new topic in biorefinery schemes. My supervisor, professor Seshan, formulated this challenging project program. I got interested in this while working on my master thesis here, in the same group.

The work was part of a collaboration project with university groups from Utrecht and Groningen. Whereas they are more interested in the hydrogen processes involved, the University of Twente brings in expertise concerning gasification processes using steam and CO2. By the time I started the project, the only possible application of humin was combustions for heat. Now some fundamental issues have been partially solved.

Adjacent to CATCHBIO programs industrial partners like Shell, Avantium, DSM and Sasol are involved as well. They were represented in my PhD committee, indicating that this subject of research is supported broadly.

Can you recall some special moments happening during your PhD project?

When characterizing the humin products - performing SEM measurements and analyses - I got very surprised a few times. Humin appears to be not stable at all, especially when higher temperatures are reached during the treatment steps. Then hollow structures appeared. When I first noticed these structures, I was very surprised as I had never expected this outcome.

Also demonstrating the asymmetrical composition, when characterizing humin, was a bit of a surprise. This feature is of importance as well, since future catalysts and catalyst processes should be designed in an efficient way and deal with this.

In what way did you develop personally as a research and scientist?

When studying literature, I learned to ask why-questions more often, paying attention to the scientific questions involved. By doing so I am able to work out a complete scientific story, and to plan and schedule my experiments from there. One could say my scientific approach is more of a full package now, in which I learned to integrate more and more aspects right from the beginning.

In what magazines were your articles published?

Three articles are submitted, waiting for release, at this very moment. One article was published in ChemSusChem.

What are your future plans? Would you like to stay in academia or would you like to pursue a career in industry?

Now I am working in a post-doc position for another year, here at Mesa+. This project is more application oriented. The treatment of gas products is one aspect, as are other technical and economic aspects.

Working on sustainable energy issues is appealing to me. Hopefully some good jobs in Dutch industry are worth applying for in the near future. As this research topic is a global one, it is thinkable I might return to my home country Vietnam. I can think of some good chances to share the knowledge I have built up here in the Netherlands in the past six years. It could go either way.

What, in your opinion, is important for Mesa+ to stay successful in future?

As a member of the Catalytic Processes & Materials Group, I enjoyed working in the intermediate area of research in which two institutes were involved: Mesa+ and Impact. Fundamental science and research on materials and catalytic processes were all present in my work.

This is a characteristic of nanotechnology: getting into contact with a lot of people, institutes and groups. At Mesa+ a variety of techniques and expertise areas are covered. It is impossible to know them all. Looking for transparency and searching for collaboration could open up new and promising crossover projects. When expertise is made more accessible, these projects could grow rapidly as many techniques to work on new ideas are available here. They can be used right way. There is no need to go and look for them at different universities.