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Project description:

Project no:
Fate of Nitrogen during Hydrothermal Carbonization
1st project leader:
Kruse, Andrea - Department of Conversion Technologies of Biobased Resources, Institute of Agricultural Engineering, University of Hohenheim, Stuttgart
2nd project leader
I. Introduction
A lot of biomass includes Nitrogen-containing compounds like proteins. In order to get higher value products from this, hydrothermal carbonization gains high interest (Kruse et al. 2013). During hydrothermal carbonization, nitrogen is partly integrated in the structure of the hydrochar formed (Kruse et al. 2016). This is important in view of the production of n-doped carbon materials for electrochemical applications, e.g. for supercaps or electrodes (Braghiroli et al. 2012; Inagaki et al. 2018). On the other hand, it is important to recover nitrogen components as fertilizer from the liquid phase. This is possible, because only a minor part is integrated into the hydrochar structure (Kruse et al. 2016). Also a part of the nitrogen, as ammonia, can be recovered together with struvite (Becker et al. 2019). In the case of struvite the ratio of ammonia and phosphate is 1:1; as usually more ammonia is in the biomass as phosphate, a new method is needed to recover the residual nitrogen from organic and inorganic compounds (see e.g. by adsorption (Zhang et al. 2020)). There is still a gap in knowledge regarding the chemical processes behind this incorporation of nitrogen in the hydrochar (Arauzo et al. 2019), and the formation of soluble n-containing compounds.

II. Aims of the studies
Basing on the knowledge summarized above the aims of this project are:

a) A better understanding how nitrogen is incorporated into the hydrochar

b) Basing on that: Development of a method to control the nitrogen incorporation.

c) Development of a method to recover the soluble nitrogen compounds after hydrothermal carbonization.
Arauzo, P. J.; Du, L.; Olszewski, M. P.; Meza Zavala, M. F.; Alhnidi, M. J.; Kruse, A. (2019): Effect of protein during hydrothermal carbonization of brewer’s spent grain. In: Bioresource Technology 293. DOI: 10.1016/j.biortech.2019.122117.

Becker, G. C.; Wüst, D.; Köhler, H.; Lautenbach, A.; Kruse, A. (2019): Novel approach of phosphate-reclamation as struvite from sewage sludge by utilising hydrothermal carbonization. In: Journal of Environmental Management 238, S. 119–125. DOI: 10.1016/j.jenvman.2019.02.121.

Braghiroli, F. L.; Fierro, V.; Izquierdo, M. T.; Parmentier, J.; Pizzi, A.; Celzard, A. (2012): Nitrogen-doped carbon materials produced from hydrothermally treated tannin. In: Carbon 50 (15), S. 5411–5420. DOI: 10.1016/j.carbon.2012.07.027.

Inagaki, Michio; Toyoda, Masahiro; Soneda, Yasushi; Morishita, Takahiro (2018): Nitrogen-doped carbon materials. In: Carbon 132, S. 104–140. DOI: 10.1016/j.carbon.2018.02.024.

Jung, D.; Körner, P.; Kruse, A. (2019): Kinetic study on the impact of acidity and acid concentration on the formation of 5-hydroxymethylfurfural (HMF), humins, and levulinic acid in the hydrothermal conversion of fructose. In: Biomass Conversion and Biorefinery. DOI: 10.1007/s13399-019-00507-0.

Jung, D.; Zimmermann, M.; Kruse, A. (2018): Hydrothermal Carbonization of Fructose: Growth Mechanism and Kinetic Model. In: ACS Sustainable Chemistry and Engineering 6 (11), S. 13877–13887. DOI: 10.1021/acssuschemeng.8b02118.

Körner, P.; Jung, D.; Kruse, A. (2018): The effect of different Brønsted acids on the hydrothermal conversion of fructose to HMF. In: Green Chemistry 20 (10), S. 2231–2241. DOI: 10.1039/c8gc00435h.

Körner, P.; Jung, D.; Kruse, A. (2019): Influence of the pH Value on the Hydrothermal Degradation of Fructose. In: ChemistryOpen 8 (8), S. 1121–1132. DOI: 10.1002/open.201900225.

Kruse, A.; Funke, A.; Titirici, M.-M. (2013): Hydrothermal conversion of biomass to fuels and energetic materials. In: Current Opinion in Chemical Biology 17 (3), S. 515–521. DOI: 10.1016/j.cbpa.2013.05.004.

Kruse, A.; Koch, F.; Stelzl, K.; Wüst, D.; Zeller, M. (2016): Fate of Nitrogen during Hydrothermal Carbonization. In: Energy and Fuels 30 (10), S. 8037–8042. DOI: 10.1021/acs.energyfuels.6b01312.

Zhang, T.; Wu, X.; Shaheen, S. M.; Zhao, Q.; Liu, X.; Rinklebe, J.; Ren, H. (2020): Ammonium nitrogen recovery from digestate by hydrothermal pretreatment followed by activated hydrochar sorption. In: Chemical Engineering Journal 379. DOI: 10.1016/j.cej.2019.122254.
Methods that will be used:
a) Experimental investigation. In the lab there are several different autoclaves available to conduct hydrothermal carbonization experiments. In addition, several different analytical methods are available there, including TGA-GC-MS, BET and FTIR. Other methods, e.g. NMR are available in the core facilities. The composition of the liquid phase could be measured by HPLC, GC, IC and other methods. Additional methods are also here available in the core facilities.

b) The processes are planned to be described by kinetic modelling. Here some experiences and the necessary software is available (Jung et al. 2018; Jung et al. 2019; Körner et al. 2018, 2019).
Collaboration partners:
Prof. T. Müller, University of Hohenheim

Prof. N. Dahmen, KIT

Prof. Zhu Wei, Hohai University
Expected candidate‘s qualification:
M.Sc in chemistry, chemical engineering or similar fields
Very good English
Hydrothermal carbonization, N-fertilizer, supercaps, electrodes, n-doped carbon materials