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Volatile products from thermal decomposition of lignocellulosic biomass have been well characterized, but the solid- and liquid-phase reactions during the early stages of decomposition are largely unknown. Here the initial solid-phase biomass thermal deconstruction reactions were analyzed in situ and with high particle heating rates, delineating how these processes occur. A variety of instrumentation was used to quantify the extent and relative rates of deconstruction, demonstrating that biopolymers resist the thermally energetic conditions to differing degrees, even when ensconced in biomass cell walls. Hemicellulose and the more frangible lignin components decompose and volatilize more readily than cellulose, which temporarily enriches biomass with cellulose. These chemical changes manifest in larger cell wall structural and mechanical property transformations. In all, this investigation concludes that these solid-phase reactions strongly influence the production rates of volatile species and will require additional study before these processes can be modeled precisely to improve yields of desired product. [ABSTRACT FROM AUTHOR]

This article explores the potential for extracting sugars from lignocellulosic biomass as a renewable energy source. It compares two strategies for extracting sugars: biochemical processing based on enzymatic hydrolysis and thermochemical processing, which includes fast pyrolysis and solvent liquefaction. The article discusses the challenges and advantages of each method and explores the potential for using sugars to produce biofuels and chemicals. It also addresses the debate over using crops for fuel production instead of food and provides an overview of biofuel policies in various countries. The text discusses different methods of biomass deconstruction, the importance of pretreatment in enzymatic hydrolysis, and various pretreatment techniques. It also explores different approaches to designing bioprocesses and the challenges involved in enzyme production and recycling. The text discusses the process of pyrolysis, the role of alkali and alkaline earth metals in catalyzing the depolymerization of lignin, and challenges in producing sugars through pyrolysis. It also discusses methods for separating and purifying sugars for fermentation. The article highlights the advantages and disadvantages of different pretreatment methods and discusses the economics of enzymatic hydrolysis and fast pyrolysis for sugar production. It emphasizes the need for further improvement in cellulosic sugar technologies. The document is a compilation of various scientific articles and reports related to biofuels and biomass conversion, providing insights into the scientific and technological aspects of biofuel production. It also includes a list of references related [Extracted from the article]

Naturally occurring alkali and alkaline earth metals (AAEM) play an important catalytic role in the pyrolysis of lignin. Other metals also potentially play a role in the catalytic deconstruction of lignin but have only been qualitatively investigated. A combination of experiments and computational modeling were performed to explore the catalytic activity of ferrous iron in comparison to AAEM. Pyrolysis experiments with extracted lignin and density functional theory (DFT) calculations for model lignin dimers showed agreement between theory and experiment. Ferrous iron proved to be a stronger catalyst than either potassium or calcium. The activity order of the AAEM cations was less clear as model and experiments agreed for hardwood lignin but disagreed for softwood lignin. DFT predicted calcium to be a stronger catalyst than potassium for breaking β-O-4 ether bonds while experiments indicated potassium to be more catalytically active as a result of higher turnover frequency. Pyrolysis of softwood lignin had a lower apparent activation energy (9.2 kcal mol−1) than for hardwood lignin (15.3 kcal mol−1). Of the catalysts tested only ferrous iron prevented the melting of lignin during pyrolysis due to its low apparent activation energy of 3.6 kcal mol−1 and 8.6 kcal mol−1 for softwood and hardwood lignin, respectively. [ABSTRACT FROM AUTHOR]

• A novel semi-batch autoclave uses rapid heat transfer for solvent liquefaction. • Slow heat transfer during heating or cooling alters products and their yields. • Scale-up from slow heat transfer experiments can lead to undersized reactors. The thermal profile of solvent liquefaction experiments must be well-controlled to generate data suitable for process scaling and technoeconomic analysis. Acknowledging the differences in small-scale batch systems compared to continuous commercial processes is important. In particular, many experiments have long heating and cooling periods, which influence rates of reaction in ways that would not occur in commercial continuous reactors. To overcome this problem, a novel semi-batch autoclave (SBA) system was built to rapidly heat reactants and cool products while maintaining constant pressure during solvent liquefaction experiments. In this study, the performance of the SBA reactor was compared to an isobaric conventional batch autoclave (ICBA) reactor in the solvent liquefaction of lignin in n -butanol. Heat transfer affected both the apparent reaction rate and measured product yields. Solvent liquefaction limited by slow heating gave the misperception that reaction rates were faster than was actually the case and promoted the formation of char-like solids. Experiments constrained by slow heat transfer are of limited use in process modeling and reactor design, which would otherwise result in undersized reactors for desired processing rates. The SBA system facilitates the design and scale-up of commercial SL plants as it approximates the thermal profile of a continuous system. [ABSTRACT FROM AUTHOR]