Reductive catalytic fractionation of pine wood: elucidating and quantifying the molecular structures in the lignin oil.

In-depth structural analysis of biorefined lignin is imperative to understand its physicochemical properties, essential for its efficient valorization to renewable materials and chemicals. Up to now, research on Reductive Catalytic Fractionation (RCF) of lignocellulose biomass, an emerging biorefinery technology, has strongly focused on the formation, separation and quantitative analysis of the abundant lignin-derived phenolic monomers. However, detailed structural information on the linkages in RCF lignin oligomers, constituting up to 50 wt% of RCF lignin, and their quantification, is currently lacking. This study discloses new detailed insights into the pine wood RCF lignin oil's molecular structure through the combination of fractionation and systematic analysis, resulting in the first assignment of the major RCF-derived structural units in the 1H-13C HSQC NMR spectrum of the RCF oligomers. Specifically, ß-5 γ-OH, ß-5 ethyl, ß-1 γ-OH, ß-1 ethyl, ß-ß 2x γ-OH, ß-ß THF, and 5-5 inter-unit linkages were assigned unambiguously, resulting in the quantification of over 80% of the lignin inter-unit linkages and end-units. Detailed inspection of the native lignin inter-unit linkages and their conversion reveals the occurring hydrogenolysis chemistry and the unambiguous proof of absence of lignin fragment condensation during proper RCF processing. Overall, the study offers an advanced analytical toolbox for future RCF lignin conversion and lignin structural analysis research, and valuable insights for lignin oil valorization purposes.

Catalytic Strategies Towards Lignin-Derived Chemicals.

Lignin valorization represents a crucial, yet underexploited component in current lignocellulosic biorefineries. An alluring opportunity is the selective depolymerization of lignin towards chemicals. Although challenged by lignin's recalcitrant nature, several successful (catalytic) strategies have emerged. This review provides an overview of different approaches to cope with detrimental lignin structural alterations at an early stage of the biorefinery process, thus enabling effective routes towards lignin-derived chemicals. A first general strategy is to isolate lignin with a better preserved native-like structure and therefore an increased amenability towards depolymerization in a subsequent step. Both mild process conditions as well as active stabilization methods will be discussed. An alternative is the simultaneous depolymerization-stabilization of native lignin towards stable lignin monomers. This approach requires a fast and efficient stabilization of reactive lignin intermediates in order to minimize lignin repolymerization and maximize the envisioned production of chemicals. Finally, the obtained lignin-derived compounds can serve as a platform towards a broad range of bio-based products. Their implementation will improve the sustainability of the chemical industry, but equally important will generate opportunities towards product innovations based on unique biobased chemical structures.

[Neoplastic invasion of the pulmonary arteries. Evaluation by MRI. Preliminary experience]. / Envahissement néoplasique des artères pulmonaires. Evaluation par IRM. Expérience préliminaire.

Bronchial tumors invading the mediastinum are no longer systematically regarded as inoperable. Curative surgery has produced a significant survival rate and led to the adaptation of the TNM classification. The degree of invasion of the pulmonary artery is a criterion of operability. The authors are trying to assess the role of MRI with regard to CT and DSA for the measurement of invasion. Their study deals with the prospective assessment of ten patients. The MRI examinations have been carried out with a 0.5 and 1.5 T supraconductive magnet (Philips Gyroscan). Cardiac gating has been used for acquisition. The planes of section are axial, transverse or oblique along the greater axis of the pulmonary arteries. CT examinations in 9-mm thick sections with and IV contrast injection demonstrate the contact of the tumor with the mediastinum. The digital angiograms have been taken with an intravenous injection into a vein of the bend of the elbow or into a femoral vein. Six cases have been verified at surgery. In all cases, the invasion predicted with MRI proved to be correctly assessed. In three cases, MRI provides additional information to the combined findings of CT and DSA. MRI is a good complement for the preoperative assessment of patients with large tumors invading the mediastinum but for which curative surgery is indicated.