Catalytic hydropyrolysis of crop straws with different biochemical composition

In this study, four kinds of straws with different biochemical compositions, including soybean straw (SS), peanut straw (PS), rice straw (RS), and corn straw (CS), were subjected to catalytic hydropyrolysis (HyPy) to explore the influence of biochemical composition on the products distribution and properties of the pyrolysis oil. The HyPy reactions were performed at 400 °C for 2 h with added 10 wt% Pd/C and 4 MPa H₂. During the HyPy, hydrogen and catalyst broke the coating structure and hydrogen bond between cellulose (CL) and hemicellulose (HCL), and thus significantly weakened the biochemical composition effect on the yield and elemental composition of the bio-oil. The bio-oil yield varied between 11.75 wt% and 13.05 wt%, and the C, H, N, O, and S content fell into the following ranges of 82.06–85.15 wt%, 9.24–9.61 wt%, 1.18–1.43 wt%, 4.62–7.86 wt%, 45–130 ppm, respectively. Biochemical composition of straw, especially the mass ratio of CL to HCL (m_CL/m_HCL), markedly influenced the molecular composition of the bio-oil. Hydrocarbons (20.15–46.66%) and phenolic compounds (17.01–47.98%) accounted for the vast majority of the identified compounds. SS and PS with higher m_CL/m_HCL (1.92 and 1.80, respectively) tended to produce bio-oils with more aromatics (22.63% and 20.70%, respectively) and fewer phenolic compounds (17.01% and 22.56%, respectively).     

Catalytic depolymerisation and conversion of Kraft lignin into liquid products using near-critical water

A high-pressure pilot plant was developed to study the conversion of LignoBoost Kraft lignin into bio-oil and chemicals in near-critical water (350 °C, 25 MPa). The conversion takes place in a continuous fixed-bed catalytic reactor (500 cm³) filled with ZrO₂ pellets. Lignin (mass fraction of approximately 5.5%) is dispersed in an aqueous solution containing K₂CO₃ (from 0.4% to 2.2%) and phenol (approximately 4.1%). The feed flow rate is 1 kg/h (reactor residence time 11 min) and the reaction mixture is recirculated internally at a rate of approximately 10 kg/h. The products consist of an aqueous phase, containing phenolic chemicals, and a bio-oil, showing an increased heat value (32 MJ/kg) with respect to the lignin feed. The 1-ring aromatic compounds produced in the process are mainly anisoles, alkylphenols, guaiacols and catechols: their overall yield increases from 17% to 27% (dry lignin basis) as K₂CO₃ is increased.