Preliminary results and status of Project 6, March 2017
The project has two main parts,
1. Catalytic conversion of lignin to aromatic intermediates
2. Conversion of lignin to binders and binder constituents by hydrothermal processes including lignin characterization and analytical methods for lignin based products
In part 1, catalytic conversion processes of lignosulfonates from the industrial partner Borregaard A/S have been studied under a range of oxidative and solvothermal reductive conditions.
The studies of the oxidative conditions aimed at investigating whether high temperature and pressure conditions could improve the processes for converting lignin into vaniline. However, the results were very discouraging since these conditions lead to excessive charring and practically no soluble products. Thus this line of research was abandoned.
In the reductive solvothermal methods conversion catalyzed by Ni and NiMo catalysts were studied. Due to sulfur poisoning of the pure catalysts, reactions catalyzed by Ni gave only partial conversion and it was not possible to regenerate the catalysts effectively. The use of the NiMo catalysts resulted in conversion of lignin to an oil fraction in 60-84% yield as compared to 24% yield from un-catalyzed reactions.
Thus, industrial catalysts from Haldor Topsøe A/S have been demonstrated with success for reductive conversion of of Borregaard lignin intermidediates in alcohols!
In part 2, the target is to develop cost competitive new binders for stone-wool based products based on lignin. This is done by studying the conversion or the partial conversion of lignin under aqueous (hydrothermal) conditions. A significant result for the project is thus to have constructed the hydrothermal liquefraction (HTL) pilot plant reported in Biofuels International.
To develop cost competitive new binders for stone wool fibres, project 6 have tested a range of lignin-based binders either with lignin as the main constituent, or with solubilized lignin as an additive in existing binder systems. During 2016 two promising compositions (lignin as co-constituent in an existing binder system) were identified, and soluble lignin were produced in large batches (600l) on the HTL pilot and tested in production scale at the ROCKWOOL factory in Doense. The tests went well with no technical or environmental problems. The products were unchanged in color, no adverse smell and good mechanical properties. However, after long term testing, these test samples did not meet all requirements. The search for new binders with lignin as the main component is ongoing, and project 6 has developed a new device for producing test samples of fiber and binder.
Analytical methods have been developed for quantification of small phenolic compounds, determining molecular mass distribution and chemical features of oligomeric and polymers in raw lignin and relevant product fractions from hydrothermal treatment of lignin. The results suggest that the monolignol composition of lignin is an important factor for the valorization of lignin by alkaline hydrothermal treatment.
Project 6 has an article under review at Journal of Analytical and Applied Pyrolysis: ”Products of hydrothermal treatment of lignin and the importance of ortho-directed repolymerization reactions”.