Search

The aim of this study was the experimental demonstration and assessment of a novel lignocellulose biorefinery (LCB) for the integration of beech wood-based products as platform and fine chemicals. The process sequence included organosolv pulping followed by pulp bleaching, hydrothermal conversion of hemicellulose to xylose and its purification, fermentation of xylose to malic acid, and base-catalyzed lignin depolymerization (BCD). The resulting products were dissolving pulp, phenolic BCD-oligomers, and malic acid. The state of the art for these technologies is their experimental proof of concept and validation at a laboratory- and pilot-scale and has a technology readiness level (TRL) of 3–4. By integrating and optimizing the single-process steps into one LCB, the TRL could be increased to 5. Based on the findings of the experimental studies, a LCB converting 50,000 dry metric tonnes ($$ \hat{=} $$ = ̂ 38.7 MW) of beech wood annually was simulated with Aspen Plus. Mass and energy balances showed that 14,616 dry metric tonnes of dissolving pulp, 5174 dry metric tonnes of BCD-oligomers, and 4077 dry metric tonnes of malic acid annually could be produced. The total energy efficiency is 40.3%. The calculation of specific production costs demonstrated the marketability of dissolving pulp (1350 €/t) and BCD-oligomers (2180 €/t), whereas malic acid (4750 €/t) is not yet competitive. Environmental assessment showed reduced greenhouse gas (GHG) emissions from the production of BCD-oligomers and malic acid and higher GHG emissions from the production of dissolving pulp compared with the reference products. In total, the examined LCB would contribute to the mitigation of global warming.

In this work, the continuous hydrothermal base catalyzed depolymerization of kraft lignin to phenolic oligomers was investigated. Using response surface methodology, a model equation for the oligomer yield in dependence of the four parameters temperature (513−573 K), NaOH concentration (1.67 and 2.50 wt%), reactor volume (0.055 and 1.000 L) and mass flow (10−20 kg/h) was obtained. To determine rate constants of the depolymerization reaction, a three-lump kinetic model was proposed, which shows a good correlation between the predicted and the experimental values. In dependence on the sodium hydroxide concentration, this model resulted in activation energies of 37 and 22 kJ/mol for the depolymerization with 1.67 and 2.50 wt% NaOH, respectively. The model enables the determination of the reaction time, where the rate of depolymerization reaches its maximum over repolymerization, which has been shown strongly depending on the reaction temperature and sodium hydroxide concentration.

Objective of this study was the investigation on the up-scaling of base-catalyzed depolymerization (BCD) of lignin to pilot plant dimension. The cleavage process was carried out in dilute alkaline solution at temperatures up to 340°C and a pressure of 25 MPa in a continuously operated tubular flow reactor with throughputs up to 20 kg/h. Investigations included the proof of the feasibility of the scale-up as well as a parameter study on the cleavage of hardwood Organosolv lignin and softwood Kraft lignin within the established pilot plant. Yields and molecular compositions of the isolated product fractions BCD-oil (liquid phenolic fraction) and BCD-oligomers (solid phenolic fraction) are similar to those described in technical lab scale, showing a good scalability. Here, BCD-oils rich in phenolic monomers such as guaiacol, catechol and/or syringol were obtained with a content of up to 13.3 wt% and 14.5 wt% from Organosolv lignin and Kraft lignin, respectively. Formation of BCD-oligomers strongly depends on temperature and residence times within the reactor.

This work evaluates the direct etherification of bio-sourced isobutylene with ethanol forming fully renewable ethyl tert-butyl ether (ETBE). Challenge was the use of the fermentative produced substrate in a solvent-free catalysis using the acidic ion exchanger Amberlyst-15. CO2 impurities have a significant influence on the liquid phase process. The conversion at a ratio that is based on molarities of isobutylene to ethanol of 1:0.9 results in yields up to 97 mol% ETBE. Purities up to 99 wt.% could be achieved by subsequent water extraction in order to ensure qualities for technical application as high performance fuel additive.

The concept of bioeconomy supports the diversification strategies of forest-based industries to create new value chains and contribute to economic growth and sustainability. The use of side streams or by-products of the pulp and paper industry (PPI) is seen as a promising approach. In line with this, the idea of substituting fossil-based materials and products is frequently discussed. One such example is the use of lignin as a bio-based alternative for fossil-based phenols. Lignin-based products not only have to fulfil identical technical requirements as their fossil-based counterparts, they are also expected to be more sustainable. This study conducts an integrated hotspot analysis of two lignin valorisation pathways during R&amp, D. The analysis considers the provision of technical kraft lignin as a by-product of a state-of-the-art kraft pulp mill, followed by valorisation, either via solvent fractionation or via base-catalysed depolymerisation (BCD), and the final application of the valorised lignins in phenol formaldehyde resins. As a two-step approach, first of all, the environmental hotspots (e.g., energy-intensive process steps) along the valorisation pathways are identified. Secondly, a variation analysis is carried out, which involves the identification of sustainability levers (e.g., selection of solvents). Identifying those levers at an early research stage helps to support the R&amp, D process towards sustainable product development.

Copper-mediated cascade reactions were performed with heterocyclically substituted aldimines. These oxidative heterocyclizations include sequences of oxidations and cycloadditions or nucleophilic additions which take place in the coordination sphere of copper ions. When two heterocyclically substituted aldimines were reacted in the presence of copper (II) salts under air, pyridine derivatives were produced. In one case a 1,4-diazatricyclo-[3.2.1.02.7]oct-3-ene was also formed. The basic structure of this new tetracyclic compound contains five new chirale carbon atoms. This cage-like structure has been revealed by X-ray crystallography. The synthesis of 2H-pyrroles by copper-assisted conversions of the aldimines with dimethylacetylene carboxylate or quinones was also described.

Copper-mediated cascade reactions were performed with heterocyclically substituted aldimines. These oxidative heterocyclizations include sequences of oxidations and cycloadditions or nucleophilic additions which take place in the coordination sphere of copper ions. When two heterocyclically substituted aldimines were reacted in the presence of copper (II) salts under air, pyridine derivatives were produced. In one case a 1,4-diazatricyclo-[3.2.1.02.7]oct-3-ene was also formed. The basic structure of this new tetracyclic compound contains five new chirale carbon atoms. This cage-like structure has been revealed by X-ray crystallography. The synthesis of 2H-pyrroles by copper-assisted conversions of the aldimines with dimethylacetylene carboxylate or quinones was also described.