The scope of the visit at IKFT department at Karlsruhe Institute of Technology was to run large scale HTC and HTL (hydrothermal carbonization and hydrothermal liquefaction) of a lignin rich woody biomass (almond’s shell, lignin content > 40% by mass) to investigate the degree of decomposition of lignin macro-constituent of this kind of residues between subcritical and supercritical water condition. On one hand Lignin in biomass is normally recalcitrant to decomposition during mild hydrothermal treatment; on the other hand decomposition of lignin in biomass could reveal as a source of valuable liquid and chemical compounds. Decomposition of such material could also lead to the production of high energy solid biofuel and/or a carbonaceous material potentially convertible to advanced carbon material (electrode material for lithium and sodium batteries, activated carbon for water remediation and so on). 

During the visit at IKFT Department, located at KIT Campus North, PAUL reactor was successfully operated at different operating condition. The almond’s shell sample (approx. 2 kg) was finely milled (≤200 mm) by mean of Fritch Pulverisette 14 variable speed rotary mill. PAUL reactor is a 2 litres stainless still stirred batch reactor, controlled by temperature, capable to operate up to 500 °C and 300 bar, specially designed for biomass liquefaction. The system is provided with gas inlet and outlet to operate at different gas atmospheres (typically nitrogen or hydrogen) and a gas sampling system for GC gas analysis. In particular PAUL reactor during this visit was operated at T= 400 °C  and P = 207 bar – biomass to water soli load 20% by mass;  T= 350 °C  and P = 180 bar – biomass to water soli load 20% by mass;  T= 300 °C  and P = 90 bar – biomass to water soli load 20% by mass;   T= 250 °C  and P = 52 bar – biomass to water soli load 20% by mass;   At the end of the reactions, before discharge the over pressure, a portion of the gas was sampled for GC-analysis. The reaction mixture was recovered by a vacuum pump and the reactor rinsed with DI water for residual solid recovering. Aqueous phase was recovered via filtration under vacuum and stored for analyses (total organic carbon – TOC, HPLC  and ICP analyses). The solid residues, dried under ventilated oven at 105 °C, were treated with dichloromethane for bio-oil extraction. Bio-oil fractions are characterized by GC-MS.  

BRISK2 project offered me a unique opportunity to access at PAUL reactor facility at KIT, with the possibility to perform thermochemical processes close to supercritical water condition, otherwise not possible at University of Trento.