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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]

We demonstrate for the first time non-catalytic, oxidative cracking with molecular oxygen (O2) to depolymerize native lignin into oxygenated phenolic monomers. Maximum monomer yield of 10.5 wt% was achieved at 250 °C after only 10 min of reaction and included vanillin, syringaldehyde, vanillic acid, and syringic acid. High rates of oxidation are attributed to the use of perfluorodecalin as solvent. Perfluorodecalin is a perfluorocarbon (PFC), characterized by their chemical stability and exceptionally high solubility for O2. Monomer yields were typically five-fold higher in perfluorodecalin compared to solvents more commonly employed in lignin conversion, such as methanol, butanol, acetonitrile, and ethyl acetate. Phenolic monomer production in perfluorodecalin favors high temperatures and short reaction times to prevent further oxidation of the produced monomers. Lignin oil obtained under oxidative conditions in perfluorodecalin showed lower molecular weight and smaller polydispersity compared to other solvents. Increasing the reaction time further decreased the molecular weight, while increasing reaction time in an inert atmosphere increased the molecular weight of the lignin oil. High concentrations of O2 in perfluorodecalin not only increased lignin depolymerization but suppressed undesirable condensation reactions. Depolymerization is likely initiated by thermally induced homolytic cleavage of ether linkages in lignin to form phenoxy and carbon-based radicals. These radicals bind with O2 as a radical scavenger and further react to form phenolic monomeric products rather than repolymerizing to large oligomers. The PFC process was scaled from 5 mL to 250 mL without any loss of yield. Because most organic compounds are not soluble in perfluorodecalin, recycling is easily achieved via liquid–liquid separation. [ABSTRACT FROM AUTHOR]

Levoglucosan has significant potential in commercial applications for the synthesis of polymers, solvents and pharmaceuticals. It is currently overlooked for commercial applications due to its high cost of synthesis and purification. We have developed a system to produce pure crystals of levoglucosan based on the fast pyrolysis of lignocellulosic biomass. A novel bio-oil recovery system concentrated levoglucosan along with other anhydrosugars, sugars and phenolic compounds in a non-aqueous "heavy ends" fraction. Liquid–liquid water extraction separated sugar-rich solubilized carbohydrates from non-soluble phenolic compounds. The solubilized carbohydrate fraction, contaminated with partially soluble phenolic monomers, was filtered through Sepabeads SP207 adsorption resin to produce clarified juice. The composition of the clarified juice on a dry basis after resin filtration and rotary evaporation was 81.2% sugars, 4.45–4.60% volatile non-sugar, 1.71% carboxylic acids and 12.5–12.6% unidentified compounds, which was sufficiently pure to crystallize the sugars by evaporation. A cold solvent rinse of the crystal mass separated and purified levoglucosan from other sugars. Levoglucosan purity was 102.5% ± 3.109% at the 99% confidence level. Techno-economic analysis of a plant pyrolyzing 250 tonne per day of pretreated biomass to produce cellulosic sugars indicated a minimum selling price (MSP) for pure levoglucosan crystals of $1333 per MT, which is less than one-tenth its current average market price. Operating hours of the plant, fermentable syrup yield and fixed capital are the most significant parameters affecting MSP. [ABSTRACT FROM AUTHOR]

Although pyrolysis of carbohydrate-rich biomass should theoretically yield large amounts of sugar, the presence of alkali and alkaline earth metals (AAEMs) in most biomass prevents this from happening. Even in small amounts, AAEM strongly catalyzes the fragmentation of holocellulose to light oxygenates compared to the thermally-induced breaking of glycosidic bonds that yield anhydrosugars. The concept of AAEM passivation, by which the catalytic activity of AAEMs can be suppressed to enhance thermal depolymerization of lignocellulose to sugars, has been previously established at the microgram scale using batch reactors. The feasibility of increasing sugar yield via AAEM passivation has not been previously demonstrated at the kilogram scale in a continuous flow reactor. The goal of this research is to demonstrate the enhanced production of sugars from AAEM passivated feedstocks in a continuous auger pyrolyzer at the kilogram scale. Alkali and alkaline earth metal passivation prior to pyrolysis increased total sugars from red oak by 105% compared to conventional pyrolysis, increasing from 7.8 wt% to 15.9 wt% of feedstock. Light oxygenates and non-condensable gases (NCGs) simultaneously decreased 45%, from 27.1 wt% to 14.7 wt% of feedstock as a result of AAEM passivation. Similarly, AAEM passivation of switchgrass increased total sugars by 259%, from 4.5 wt% to 16.2 wt% of feedstock, while the light oxygenates and NCGs decreased by 48%, from 20.0 wt% to 10.5 wt% of feedstock. An undesirable outcome of AAEM passivation was an increase in char production, increasing by 65% and 30% for pyrolysis of red oak and switchgrass, respectively. Loss of lignin-derived phenolic compounds from the bio-oil can explain 67% and 38% of the increase in char for red oak and switchgrass, respectively. The remaining 33% char increase for red oak (3.1 wt% char) and 62% char increase for switchgrass (4.0 wt% char) appear to be from carbonization of sugars released during pyrolysis of acid-infused biomass. [ABSTRACT FROM AUTHOR]

We report on the catalytic pyrolysis of switchgrass and its three main components (cellulose, hemicellulose and lignin) over H-ZSM5 catalyst. The yields of aromatic hydrocarbons for the three components decreased in the following order: cellulose > hemicellulose ⪢ lignin. Moderately higher temperature favored formation of aromatics. The results indicate that H-ZSM5 catalyst did not remove oxygen in an optimal pathway for catalytic pyrolysis of biomass. Dehydration was the dominant oxygen removal mechanism for catalytic pyrolysis, while decarbonylation to CO was favored over decarboxylation to CO2. This suggests that higher yields of aromatics might be achieved by catalyst improvements or reactor design that optimizes deoxygenation pathway. For cellulose and hemicellulose, coke produced catalytically contributed a larger fraction of solid carbonaceous residue than char from purely thermal processes. In the case of lignin, thermal rather than catalytic processes primarily contribute to the production of solid carbonaceous residue. Product distribution from catalytic pyrolysis of switchgrass appeared to be the additive contribution of the three individual components, which indicates that there was no significant interaction among the biomass-derived products. [ABSTRACT FROM AUTHOR]

We report an economically- and environmentally-promising microalgae biorefinery pathway, which uses catalytic pyrolysis with HZSM-5 catalyst to convert whole microalgae into aromatic hydrocarbons. This process produces valuable petrochemicals and ammonia, the latter of which can be recycled as a fertilizer for microalgae cultivation. We tested samples of lipid-lean green microalgae, Chlorella vulgaris, at various reaction temperatures and catalyst loads. We also tested samples of lignocellulosic biomass, red oak, for comparison. Our results demonstrated that catalytic pyrolysis of microalgae produces better aromatic yields and better aromatic distributions than catalytic pyrolysis of red oak. The maximum carbon yield of aromatics from microalgae was 24%, while that from red oak was 16.7%. Moreover, catalytic pyrolysis of microalgae produced more monocyclic aromatics than were produced by catalytic pyrolysis of lignocellulosic biomass. Microalgae present many advantages as a feedstock for biofuel. With the promise catalytic pyrolysis offers for solving some of microalgae's disadvantages, microalgae biorefineries move one step closer to economic and environmental feasibility. [ABSTRACT FROM AUTHOR]

We have developed a biomass-derived solid fuel, referred to as Lignocol, that can reduce sulfur and nitrogen emissions from coal-fired power plants without suffering the ash fouling and loss of boiler capacity usually associated with co-firing biomass. To produce Lignocol, lignocellulosic biomass was pyrolyzed to vapors that were condensed as distinct fractions of bio-oil. The heavy ends of bio-oil, consisting primarily of anhydrosugars from holocellulose and phenolics from lignin in the biomass, was subjected to a water extraction to produce separate streams of water-insoluble phenolics and water-soluble sugars. The phenolics were cured at 105–220 °C to evaporate water and expedite cross-linking reactions that solidified the phenolic liquid into Lignocol. The higher heating value (HHV) and particle density of Lignocol were similar to several commercially significant coals in the United States while the nitrogen and sulfur contents were only 0.26 wt% and 0.02 wt%, respectively, much lower than typically found in coal. The ash content of Lignocol was less than 0.5 wt% compared to 3–10 wt% for coals. Lignocol was structurally stable in the presence of water and only leached 8.52 ppm and 9.03 ppm of aromatics at pH 4.2 and 5.0, respectively. Lignocol was combusted at 650 °C in a 100 g/h fluidized bed reactor to determine feeding characteristics. Neither melting in the feeder system nor agglomeration in the reactor were observed. Based on these observations, Lignocol has excellent prospects for high levels of co-firing with coal in power plants and replacing wood pellets in dedicated biomass-firing while avoiding the usual challenges of burning biomass. [ABSTRACT FROM AUTHOR]

• Advances in production of pyrolytic sugars hampered by char agglomeration. • Metals that catalyze sugar decomposition also catalyze lignin depolymerization. • Ferrous sulfate both prevented sugar decomposition and agglomerate formation. • Volumetric sugar productivity was 400 times higher than for enzymatic hydrolysis. Fast pyrolysis of lignocellulosic biomass yields little sugar or anhydrosugars compared to pyrolysis of pure polysaccharides because naturally abundant alkali and alkaline earth metals (AAEM) in biomass catalyze the fragmentation of pyranose and furanose rings. Sugar yields can be increased dramatically by pretreating the biomass with sulfuric acid prior to pyrolysis, which passivates the catalytic activity of the metals by converting them into thermally stable salts. However, depolymerization of lignin in biomass also depends on the catalytic activity of AAEM. Thus, passivating AAEM has the unintended consequence of slowing the rate of depolymerization and volatilization of lignin, resulting in a transient melt phase that agglomerates and can foul pyrolysis reactors. To overcome this problem, various non-alkali metal sulfates were tested as replacements for sulfuric acid. Iron in the form of ferrous sulfate proved the most effective in depolymerizing lignin without fragmenting pyranose rings. Conventional nitrogen-blown pyrolysis of ferrous sulfate pretreated corn stover achieved WHSV of 4 h−1 compared to only 0.6 h−1 for acid pretreated corn stover. Autothermal (air-blown) pyrolysis of ferrous sulfate pretreated corn stover showed even more dramatic improvement, increasing WHSV from 1 h−1 to 10 h−1 compared to acid pretreated corn stover under autothermal operation. Fermentable sugar yields from the pyrolysis of corn stover increased from 0.9 wt% to 11.8 wt% on a biomass basis, a 13-fold increase as a result of the ferrous sulfate pretreatment. These advantages combine to increase volumetric sugar productivity from 62 g L−1 h−1 for conventional pyrolysis of untreated corn stover to 2041 g L−1 h−1 for autothermal pyrolysis of ferrous sulfate treated corn stover. [ABSTRACT FROM AUTHOR]

Solvent liquefaction (SL) of biomass is a promising technology for the conversion of biomass to renewable fuels and chemicals. Liquid-phase thermal deconstruction of biomass in the presence of hydrocarbon-based hydrogen-donating solvents can result in bio-oils with low moisture and low oxygen content. These oils are thermally stable and highly miscible with hydrocarbon streams, which make them a promising biorenewable blendstock for petroleum refineries. We have developed a 1 kg hr −1 continuous SL pilot plant to evaluate the performance of SL of southern yellow pine in a hydrocarbon solvent. The process development unit (PDU) was also designed to evaluate several unit operations critical to large-scale operations. Online solids removal was conducted with inline wire mesh barrier filters with separation efficiency of over 99%. Acetone injection was used to aid in solids removal, and an online recovery system was demonstrated with greater than 97% acetone recovery. Continuous online bio-oil fractionation was also demonstrated using a distillation column to separate approximately 93 wt% of the initial solvent from the biomass-derived products. [ABSTRACT FROM AUTHOR]

Catalytic fast pyrolysis (CFP) offers a simple and robust route to convert raw lignocellulosic biomass to aromatic hydrocarbons. During CFP, cellulose, hemicellulose, and lignin are first thermally decomposed to bio-oil vapors that are further converted to aromatics in the presence of a ZSM-5 zeolite catalyst. The high temperatures required for CFP also favor coke formation, an undesired byproduct, through condensation of the oxygenated intermediates on ZSM-5′s outer surface and/or secondary reactions inside its micropores. Introducing mesopores through desilication represents a possible strategy to enhance mass transport and intracrystalline diffusion, and consequently favor aromatic production over undesired coke formation. Here, we study the effect of desilication on the structure, acidity, and performance of aluminum-rich ZSM-5. Detailed characterization of the obtained zeolite catalysts indicates that mild desilication conditions do not significantly affect the elemental composition, crystallographic structure, microporosity, and distribution of aluminum atoms in framework and extraframework sites. However, the number of accessible Brønsted acid sites increased by ∼50% as a result of the enhanced mesoporosity. Desilication increased the aromatic yields obtained for red oak pyrolysis (27.9%) compared to the parent zeolite (23.9%), without impacting the liquid product distribution (67.4% selectivity to benzene, toluene, and xylene). Our results suggest the catalytic performance could be further improved by enlarging the mouth of ink bottle shaped mesopores in order to further enhance mass transport between the gas phase and the zeolite’s micropore network. [ABSTRACT FROM AUTHOR]

Bio-oil derived from the pyrolysis of lignocellulosic biomass shows a great promise, however, needs further upgrading to potentially serve as an alternative to fossil fuels. Herein, we demonstrate that crude fast pyrolysis bio-oil can be directly used as a fuel for anion exchange membrane fuel cells (AEMFCs) to generate high power density electrical energy at low temperature (⩽80 °C). A simple aqueous-phase reduction method was used to prepare carbon nanotube (CNT) supported noble metal (Pt, Pd, Au, and Ag) nanoparticles with average particle sizes: 1.4 nm, 2.0 nm, 3.8 nm, and 12.9 nm for Pt/CNT, Pd/CNT, Au/CNT, and Ag/CNT, respectively. Direct fast pyrolysis bio-oil AEMFCs with the Pd/CNT anode catalyst and a commercial Fe-based cathode catalyst exhibit a remarkable peak power density of 42.7 mW cm −2 at 80 °C using 30 wt% bio-oil + 6.0 M KOH electrolyte. Levoglucosan was identified as the major sugar compound with 11.1 wt% of the bio-oil composition, along with disaccharides, pyrolytic lignin, and oligomer of lignin-derived phenolic compounds. Cyclic voltammetry (CV) studies investigated the electrocatalytic oxidation of high purity levoglucosan over the four noble metal catalysts in half cell, as levoglucosan is the dominant sugar component in bio-oil. Pd/CNT, compared to other catalysts, displayed the highest activity and lowest onset potential of electrocatalytic oxidation of levoglucosan. AEMFC with high purity sugars shows ∼1.2 to 3 times higher power density than that with fast pyrolysis bio-oil fuel. [ABSTRACT FROM AUTHOR]

Abstract: The economic feasibility of a facility producing monosaccharides, hydrogen and transportation fuels via fast pyrolysis and upgrading pathway was evaluated by modeling a 2000 dry metric ton biomass/day facility using Aspen Plus®. Equipment sizing and cost were based on Aspen Economic Evaluation® software. The results indicate that monosaccharide production capacity could reach 338 metric tons/day. Co-product yields of hydrogen and gasoline were 23.4 and 141 metric tons/day, respectively. The total installed equipment and total capital costs were estimated to be $210 million and $326 million, respectively. A facility internal rate of return (IRR) of 11.4% based on market prices of $3.33/kg hydrogen, $2.92/gal gasoline and diesel, $0.64/kg monosaccharide was calculated. Sensitivity analysis demonstrates that fixed capital cost, feedstock cost, product yields, and product credits have the greatest impacts on facility IRR. Further research is needed to optimize yield of sugar via the proposed process to improve economic feasibility. [Copyright &y& Elsevier]

The goal of this research is to develop a partial delignification process for corn stover that simultaneously improves accessibility of enzymes to cellulose and recovers hydroxycinnamic acids (HCA) as a value-added product from the lignin. We recover HCAs from corn stover with a mild base extraction employing sodium hydroxide, ethanol, and water. The total HCA yield was 33.5 wt% on a lignin basis and approximately 6 wt% on a corn stover basis. This partial delignification pretreatment allowed 85 wt% of total available glucose to be recovered by enzymatic hydrolysis using an enzyme loading that is only 10% of the level recommended for recovering sugars from lignocellulosic biomass. Technoeconomic analysis indicates that recovery of HCAs could reduce the selling price of ethanol by $0.26 L-1. That part of the lignin not removed as HCA becomes a co-product of enzymatic hydrolysis suitable for thermochemical processing into additional biofuels and/or chemicals. • Hydroxycinnamic acids were extracted from corn stover via alkaline pretreatment. • Hydroxycinnamic acids yield was 6 wt% on a biomass basis. • The pretreatment makes corn stover more susceptible to enzymatic hydrolysis. • Recovery of HCA from corn stover improves the economics of cellulosic ethanol. [ABSTRACT FROM AUTHOR]