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Thin films (∼115 μm thick) of milled wood lignin from hybrid poplar and acid-washed hybrid poplar were pyrolyzed at 500 °C and ∼55 °C/s at five pressures (4, 250, 500, 750, and 1000 mbar) to determine the impact of secondary liquid intermediate reactions on the product distribution. For both milled wood lignin extracted from poplar and acid-washed hybrid poplar wood, pressure had a significant effect on the product distribution for thin film pyrolysis between 4 and 1000 mbar. For lignin, lowering the pressure from 1000 mbar to 4 mbar reduced the char yield from 36 to 23% and enhanced production of large cluster pyrolytic lignin. However, the pressure did not dramatically impact the gas yield (CO2, CO, methane, H2, ethane, propane, and butane), nor did it significantly impact the release of monomeric phenolic compounds. ICR-MS shows limited changes in the composition of lignin oligomers. The increase in the production of large lignin oligomers observed by UV fluorescence and the reduction of char yield with vacuum confirm the importance of oligomeric combination reactions to form large polyaromatic structures in the liquid intermediate. For hybrid poplar, lowering the pressure from 1000 mbar to 4 mbar decreased the char yield from 19 to 7% and enhanced production of heavy sugars (cellobiosan and cellotriosan). ICR-MS results clearly show the importance of dehydration reactions in the liquid intermediate. Lowering the pressure also enhanced production of CO, CO2, and methane due to heterogeneous catalysis by residual alkali and alkaline earth metals in the solid wood matrix. However, it also decreased production of levoglucosan from 10 to 6.1 wt %. The yields of levoglucosan and cellobiosan obtained for hybrid poplar were higher and lower, respectively, compared with those expected if the pyrolysis products were the result of the additive contribution of hybrid poplar constituents. This result could be explained by the tendency of lignin liquid intermediate to bubble vigorously, contributing in this way to the removal of cellulose oligomers from the liquid intermediate.

Sustainable aviation fuel (SAF) production is an area of intense research, with many production pathways competing for commercialization in a rapidly changing policy environment. Current techno-economic methods to discern minimum selling price (MSP) can require extensive research and be difficult to generalize to the guidance of emerging technologies. There is a need for more flexible methods to guide the evolution of SAF production toward economically and environmentally viable pathways. We present the following technology-neutral heuristic to approximate MSP, then demonstrate its use to evaluate strategies to minimize the cost of CO2abatement for a given SAF process. We first apply it to stoichiometric cases based on the method of oxygen removal (in the form of H2O, CO2, or O2), which serves as paradigm targets for technological evolution. Our analysis indicates that in a favorable green hydrogen market (prices below 2.50 $/kg), oxygen removal as H2O is preferable, while removal as CO2is preferable at current hydrogen prices. Carbon supplements from lower-oxygen-content sources (such as plastic) and sequestration (such as char) were also shown to potentially reduce production and abatement costs for stoichiometric models. These findings held true when applying this heuristic to model a fast pyrolysis process with waste plastic supplements reducing abatement costs while still meeting CI reduction criteria. The heuristic was also used to evaluate potential evolution paths for gasification/Fischer–Tropsch technologies. A similar trend to the stoichiometric models emerged, with a significant reduction in hydrogen cost and CI required to justify supplementing the process. In this way, we demonstrate a novel approach to the screening and evolution of SAF processes toward viability and efficiency.

In this work, we examine the evolution of functional groups (carbonyl, carboxyl, phenol, and hydroxyl) during hydrotreatment at 100–200 °C of two typical wood derived pyrolysis oils from BTG and Amaron in a batch reactor over Ru/C catalyst for reaction time of 4 h. An aqueous and an oily phase were obtained. The contents of the functional groups in both phases were analyzed by GC/MS, 31P NMR, 1H NMR, CHN, KF titration, UV fluorescence, carbonyl groups by Faix and phenols by Folin−Ciocalteu method. The consumption of hydrogen was between 0.007 and 0.016 g/(g of oil), and 0.001–0.020 g of CH4/(g of oil), 0.005–0.016 g of CO2/(g of oil), and 0.03–0.10 g of H2O/(g of oil) were formed. The contents of carbonyl, hydroxyl, and carboxyl groups in the volatile GC-MS detectable fraction decreased (80, 65, and ∼70%, respectively), while their behavior in the total oil and hence in the nonvolatile fraction was more complex. The carbonyl groups initially decreased having a minimum at ∼125–150 °C and then increased, while the hydroxyl groups had a reversed trend. This might be explained by the initial hydrogenation of the carbonyl groups to form hydroxyls, followed by continued dehydration reactions at higher temperatures that may have increased their content. The 31P NMR analysis was on the limit of its sensitivity for the carboxylic groups to precisely detect changes in the upgraded nonvolatile fraction; however, the more precise titration method showed that the concentration of carboxylic groups in the nonvolatile fraction remains constant with increased hydrotreatment temperature. The UV fluorescence results show that repolymerization increases with temperature, starting as low as 125 °C. ATR-FTIR method coupled with deconvolution of the region between 1490 and 1850 cm–1was shown to be a good tool for following the changes in carbonyl groups and phenols of the stabilized pyrolysis oils. The deconvolution of the IR bands around 1050 and 1260 cm–1correlated very well with the changes in the 31P NMR silent O groups (likely ethers). Most of the H2O formation could be explained from the significant reduction of these silent O groups (from 12% in the fresh oils, to 6 to 2% in the stabilized oils) most probably belonging to ethers.