Controlled catalytic breakdown of humin and chitin to waterborne building blocks including spatially-resolved spectroscopy of film formation and drying processes

Shown was the high potential of chitosan in all kinds of biobased, more specifically chitosan based materials for a more sustainable future. Likewise, chitosan could be used as a functional carrier for active catalysts like successfully shown for e.g., platinum-integrated zirconia-based metal organic framework (MOF) UiO 67, which were used for carbon dioxide (CO2) reduction as a model reaction.

Further, green additives were successfully used to tune the properties of chitosan-based films and materials within a wide range from soft to hard, and from brittle to flexible. The uptake behaviour of the additives show non-saturating, saturating, and crosslinking behaviour, indicating that multifunctional additives, such as citric acid, crosslink the polymer strands, which induces a great strength to the material. Additionally, pure chitosan films show to be reacetylated when cast with acetic acid in comparison to when cast with hydrochloric acid, inducing additional higher thermal and mechanical strength to the film. As their potential for industrial application is also highly dependent on the long-term stability and effects of aging, we found through aging-studies that all films had at least slight discolorations coming from degradation products within them after the investigated period of 400 days. The least affected hereby are the pure chitosan film and films with lactic acid and citric acid as additives.

Finally, the depolymerization of chitosan with supported bimetallic nanoparticles was investigated, using a combination of palladium (Pd) as a potent noble metal and nickel (Ni) as a cheap transition metal in different metal ratios supported on SiO2. Pd alone appears not to depolymerize chitosan to a large extent, while Ni alone already can depolymerize the initial polymer to ~ 45-58% of its initial length. In combination though, Pd and Ni show a synergistic effect which is even depolymerizing the chitosan polymer further than any of the metals alone.