Climate change, including the need to reduce relevant emission such as CO2 on the one side and finite reservoirs of crude oil on the other side, lead to an increased interest in sustainable, renewable and alternative sources for aromatic molecules. Lignin is the most abundant renewable source of aromatic molecules on earth. In this context, lignin-containing process streams deriving from pulp and paper industries or biorefineries are of huge interest. The pulp and paper industry produces ca. 50 million tons of lignin per year as kraft lignin, lignosulfonates and organosolv lignin, but only approximately 2% are used for the production of industrial products while the rest is incinerated for internal energy supply or treated as waste. Aim of the present study is the treatment of spent sulfite liquor deriving from paper mills to enable the valorization of lignin, or more precisely of lignosulfonate, applying ultrafiltration processes with ceramic membranes (tubular and hollow fiber). A first ultrafiltration step (UF1) is implemented in order to concentrate and to fractionate the containing lignosulfonate molecules. The next step comprises a chemical degradation of the concentrated lignosulfonate fraction into smaller units followed by another ultrafiltration step (UF2), which separates partially degraded or non-degraded lignosulfonates from desired mono-aromatic products. Within this work we investigate a) the performance of ceramic membranes with different properties (tubular and hollow fiber membrane geometries and various membrane molecular weight cut-offs: 1.0 kDa up to 800 kDa) and b) the performance of different membrane separation processes and parameters as well as operation modes and their effects on membrane fouling for the treatment of spent sulfite liquor and different feed streams from the degradation step.

Ceramic membranes for lignin valorization

255th National Meeting (2018)

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