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The production of aromatic hydrocarbons from cellulose by zeolite-catalyzed fast pyrolysis involves a complex reaction network sensitive to the zeolite structure, crystallinity, elemental composition, porosity, and acidity. The interplay of these parameters under the reaction conditions represents a major roadblock that has hampered significant improvement in catalyst design for over a decade. Here, we studied commercial and laboratory-synthesized ZSM-5 zeolites and combined data from 10 complementary characterization techniques in an attempt to identify parameters common to high-performance catalysts. Crystallinity and framework aluminum site accessibility were found to be critical to achieve high aromatic yields. These findings enabled us to synthesize a ZSM-5 catalyst with enhanced activity, which offers the highest aromatic hydrocarbon yield reported to date., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

This study investigates the optimal supply chain design for commodity chemicals (BTX, etc.) production via woody biomass fast pyrolysis and hydroprocessing pathway. The locations and capacities of distributed preprocessing hubs and integrated biorefinery facilities are optimized with a mixed integer linear programming model. In this integrated supply chain system, decisions on the biomass chipping methods (roadside chipping vs. facility chipping) are also explored. The economic objective of the supply chain model is to maximize the profit for a 20-year chemicals production system. In addition to the economic objective, the model also incorporates an environmental objective of minimizing life cycle greenhouse gas emissions, analyzing the trade-off between the economic and environmental considerations. The capital cost, operating cost, and revenues for the biorefinery facilities are based on techno-economic analysis, and the proposed approach is illustrated through a case study of Minnesota, with Minneapolis-St. Paul serving as the chemicals distribution hub., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Depolymerization of cellulose offers the prospect of inexpensive sugars from biomass. Breaking the glycosidic bonds of cellulose to liberate glucose has usually been pursued by acid or enzymatic hydrolysis although a purely thermal depolymerization route to sugars is also possible. Fast pyrolysis of pure cellulose yields primarily the anhydrosugar levoglucosan (LG) whereas the presence of naturally occurring alkali and alkaline earth metals (AAEMs) in biomass strongly catalyzes ring-breaking reactions that favor formation of light oxygenates. Here, we show a method of significantly increasing the yield of sugars from biomass by purely thermal means through infusion of certain mineral acids (phosphoric and sulfuric acid) into the biomass to convert the AAEMs into thermally stable salts (particularly potassium sulfates and phosphates). These salts not only passivate AAEMs that normally catalyze fragmentation of pyranose rings, but also buffer the system at pH levels that favor glycosidic bond breakage. It appears that AAEM passivation contributes to 80 % of the enhancement in LG yield while the buffering effect of the acid salts contributes to the balance of the enhancement., (Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A techno-economic analysis was conducted to investigate the feasibility of a gasification-based hybrid biorefinery producing both hydrogen gas and polyhydroxyalkanoates (PHA), biodegradable polymer materials that can be an attractive substitute for conventional petrochemical plastics. The biorefinery considered used switchgrass as a feedstock and converted that raw material through thermochemical methods into syngas, a gaseous mixture composed mainly of hydrogen and carbon monoxide. The syngas was then fermented using Rhodospirillum rubrum, a purple non-sulfur bacterium, to produce PHA and to enrich hydrogen in the syngas. Total daily production of the biorefinery was assumed to be 12 Mg of PHA and 50 Mg of hydrogen gas. Grassroots capital for the biorefinery was estimated to be $55 million, with annual operating costs at $6.7 million. With a market value of $2.00/kg assumed for the hydrogen, the cost of producing PHA was determined to be $1.65/kg.

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]

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]

Abstract Pyrolysis is one of the most efficient and environmentally attractive thermochemical processes for conversion of both biomass and wastes to energy products. This review focuses on the use of auger reactors, also known as screw reactors, for the pyrolysis of carbonaceous solids into liquid, gaseous and solid products that can be used in the production of fuels and other valued-added products. The auger reactor is attractive for its versatility in transforming a wide range of feedstocks, and has been recognized as one of the technologies with better strengths not only for fast pyrolysis, but also for slow or intermediate pyrolysis. Auger pyrolyzers are of relatively simple design and overcome some of the problems of conveying heat for pyrolyzing biomass or wastes. The mechanical forces associated with auger reactors enhance particle mixing and heat transfer, which are key to successful pyrolysis. This paper presents a comprehensive review of the advantages and challenges of this technology and identify the main characteristics of both single- and twin-screw auger technology. The effect of operating conditions on yield and some properties of pyrolysis products are also provided. The review includes examples of commercial/demonstration-scale auger pyrolysis plants operated around the world. Highlights • The literature on auger pyrolyzers is widely surveyed. • Auger technology is attractive for pyrolyzing a wide range of feedstocks. • Auger pyrolyzers are able to work for fast, intermediate and slow conditions. • Yields and products characteristics are described for different plants. [ABSTRACT FROM AUTHOR]

The goal of this study is to evaluate the role of biomass heating time on bio-oil yield during fast pyrolysis in a free fall reactor. Biomass heating times were controlled using several configurations for conveying solids from the bottom of the free fall reactor. In all tests reactor wall temperature was 550 °C, sweep gas flowrate was 18 L/min, and heated reactor length was 2.77 m, which set the minimum biomass heating time of approximately 1.4 s (particles falling downward in sweep gas). Analysis of products included solid, liquid and gas mass yields; proximate analysis of the solids; and water-soluble sugar and carboxylic acid content of the liquid. These experiments showed that biomass continued to pyrolyze well beyond the few seconds frequently assumed to be adequate to achieve fast pyrolysis. Bio-oil yield increased with biomass heating times, even for times exceeding 40 s. Analysis of liquid products suggests that hemicellulose, cellulose, and lignin all contributed toward the longer than expected pyrolysis times. [ABSTRACT FROM AUTHOR]

Gasification is an attractive option for converting biomass into fuels and chemicals. Most biomass contains significant amounts of fuel-bound nitrogen (FBN), which partially converts into ammonia (NH 3 ) and hydrogen cyanide (HCN) during gasification. These nitrogen compounds are problematic as they can lead to NO X emissions or catalyst poisoning in downstream applications of syngas. FBN can convert to other products as well, including diatomic nitrogen (N 2 ), char-bound nitrogen (char-N), and tar-bound nitrogen (tar-N). Efforts to predict concentrations of NH 3 and HCN have been hindered by a lack of accurate, comprehensive measurements of nitrogen partitioning among gasification products. The present study gasified switchgrass under allothermal, short residence time conditions and measured NH 3 , HCN, char-N, and tar-N as a function of temperature in the range of 650–850 °C with diatomic nitrogen determined by difference. It was found that a major portion of FBN was retained in the char and tar products. As temperature was increased, char and tar were consumed, releasing nitrogen as gaseous NH 3 and HCN. This increase in undesirable nitrogen compounds is contrary to the predictions of most gasification models, which overlook the presence of significant nitrogen in char and tar even if they include tar cracking and char gasification reactions. The results of this study demonstrate that gas-phase reactions alone are not sufficient to predict the fate of nitrogen during gasification. In order for modeling efforts to obtain more accurate predictions of nitrogen partitioning, the reactions through which gaseous nitrogen-bearing species are released from char and tar must be considered. [ABSTRACT FROM AUTHOR]

Technical lignin extracted from lignocellulosic biomass melts and agglomerates when heated, making its thermal processing problematic and impeding this pathway to low-cost renewable aromatics. We have developed a simple pretreatment of technical lignin with Ca(OH)2 that made possible the continuous pyrolysis of lignin in a fluidized bed reactor to produce a phenolic-rich bio-oil. The yield of bio-oil was approximately 38 wt% for pyrolysis in the temperature range of 450 to 600 °C. Average molecular weight of bio-oil was less than 288 Da indicating that the lignin was extensively depolymerized to phenolic monomers and dimers. Char from pyrolysis of pretreated lignin was fine powder in contrast to the large agglomerates of char produced from untreated lignin. The surface area of char from pyrolysis of pretreated lignin was relatively less than for char obtained from pyrolysis of whole biomass. The melting and agglomeration behavior of lignin appears to be due to the presence of phenolic hydroxyl, carboxylic acid and aldehyde groups in lignin. Pretreatment with Ca(OH)2 reduced these functional groups by forming hydroxylcalcium phenoxides, phenolic alcohols, and phenolic carboxylate salts that inhibited agglomeration. [ABSTRACT FROM AUTHOR]

This article reports that biomass resources, such as wood, grasses and municipal wastes, can take one of three thermochemical pathways -- combustion, indirect liquefaction or direct liquefaction --to be converted to useful energy and fuel. Topics discussed include how these pathways transform biomass resources into liquid fuels or electric power and the associated economic costs of these pathways. Mentioned also are pyrolysis and solvent liquefaction as the two methods of direct liquefaction.

We report on the quantitative analysis of free radicals in bio-oils produced from pyrolysis of cellulose, organosolv lignin, and corn stover by EPR spectroscopy. Also, we investigated their potential role in condensed-phase polymerization. Bio-oils produced from lignin and cellulose show clear evidence of homolytic cleavage reactions during pyrolysis that produce free radicals. The concentration of free radicals in lignin bio-oil was 7.5×1020 spin g−1, which was 375 and 138 times higher than free-radical concentrations in bio-oil from cellulose and corn stover. Pyrolytic lignin had the highest concentration in free radicals, which could be a combination of carbon-centered (benzyl radicals) and oxygen-centered (phenoxy radicals) organic species because they are delocalized in a π system. Free-radical concentrations did not change during accelerated aging tests despite increases in molecular weight of bio-oils, suggesting that free radicals in condensed bio-oils are stable. [ABSTRACT FROM AUTHOR]

Fast pyrolysis of biomass to produce a bio-oil followed by catalytic upgrading is a widely studied approach for the potential production of fuels from biomass. Because of the complexity of the bio-oil, most upgrading strategies focus on removing oxygen from the entire mixture to produce fuels. Here we report a novel method for the production of the specialty chemical, gluconic acid, from the pyrolysis of biomass. Through a combination of sequential condensation of pyrolysis vapors and water extraction, a solution rich in levoglucosan is obtained that accounts for over 30 % of the carbon in the bio-oil produced from red oak. A simple filtration step yields a stream of high-purity levoglucosan. This stream of levoglucosan is then hydrolyzed and partially oxidized to yield gluconic acid with high purity and selectivity. This combination of cost-effective pyrolysis coupled with simple separation and upgrading could enable a variety of new product markets for chemicals from biomass. [ABSTRACT FROM AUTHOR]

Highlights: [•] Partial oxidative pyrolysis of acid infused red oak was conducted. [•] Char agglomeration was reduced by 88.9% compared to the control run. [•] Sugar yield increased to 20.62g/100g biomass for 2.1vol% oxygen. [•] Up to 67% of SF1 bio-oil was hydrolysable sugar. [ABSTRACT FROM AUTHOR]

This study explores the separate recovery of sugars and phenolic oligomers produced during fast pyrolysis with the effective removal of contaminants from the separated pyrolytic sugars to produce a substrate suitable for fermentation without hydrolysis. The first two stages from a unique recovery system capture 'heavy ends', mostly water-soluble sugars and water-insoluble phenolic oligomers. The differences in water solubility can be exploited to recover a sugar-rich aqueous phase and a phenolic-rich raffinate. Over 93 wt % of the sugars is removed in two water washes. These sugars contain contaminants such as low-molecular-weight acids, furans, and phenols that could inhibit successful fermentation. Detoxification methods were used to remove these contaminants from pyrolytic sugars. The optimal candidate is NaOH overliming, which results in maximum growth measurements with the use of ethanol-producing Escherichia coli. [ABSTRACT FROM AUTHOR]

Abstract: Syngas from gasification of carbonaceous feedstocks is used for power production and synthesis of fuels and commodity chemicals. Impurities in gasification feedstocks, especially sulfur, nitrogen, chlorine, and ash, often find their way into syngas and can interfere with downstream applications. Incomplete gasification can also produce undesirable products in the raw syngas in the form of tar and particulate char. This paper reviews the technologies for removing contaminants from raw syngas. These technologies are classified according to the gas temperature exiting the cleanup device: hot (T > 300 °C), cold (T < ∼100 °C), and warm gas cleaning regimes. Cold gas cleanup uses relatively mature techniques that are highly effective although they often generate waste water streams and may suffer from energy inefficiencies. The majority of these techniques are based on using wet scrubbers. Hot gas cleaning technologies are attractive because they avoid cooling and reheating the gas stream. Many of these are still under development given the technical difficulties caused by extreme environments. Warm gas cleaning technologies include traditional particulate removal devices along with new approaches for removing tar and chlorine. [Copyright &y& Elsevier]

Thermochemical processing of biomass by fast pyrolysis provides a nonenzymatic route for depolymerization of biomass into sugars that can be used for the biological production of fuels and chemicals. Fermentative utilization of this bio-oil faces two formidable challenges. First is the fact that most bio-oil-associated sugars are present in the anhydrous form. Metabolic engineering has enabled utilization of the main anhydrosugar, levoglucosan, in workhorse biocatalysts. The second challenge is the fact that bio-oil is rich in microbial inhibitors. Collection of bio-oil in distinct fractions, detoxification of bio-oil prior to fermentation, and increased robustness of the biocatalyst have all proven effective methods for addressing this inhibition. [ABSTRACT FROM AUTHOR]

Abstract: An indirectly heated gasifier is under development at Iowa State University. This gasifier integrates a latent-heat ballast with a fluidized-bed reactor. The latent heat ballast is an array of stainless-steel tubes filled with lithium fluoride, which is a high-temperature phase-change material (PCM). Previous studies have presented experimental results from the gasifier and described a mathematical model of the pyrolysis phase of the cyclic gasification process. This model considers both heat transfer and chemical reactions that occur during pyrolysis, but discrepancies between model predictions and experimental data have demonstrated the need to refine the model. In particular, cooling curves for the ballasting system are not well predicted during phase change of the lithium fluoride. A reformulated model, known as the Receding Interface (RI) model, postulates the existence of a receding liquid phase within the ballast tubes as they cool, which progressively decreases the rate of heat transfer from the tubes. The RI model predicts behavior that is more consistent with experimental results during the phase-change process, while retaining accuracy before and after the process of phase change. [Copyright &y& Elsevier]

The International Panel on Climate Change and the 2015 Climate Summit in Paris have recommended that efforts to reduce carbon emissions be coupled with carbon removal from the atmosphere. Carbon negative energy combines net carbon removal with the production of energy products or other revenue-generating products beyond sequestered carbon. Even though both biochemical and thermochemical approaches to carbon negative energy can be envisioned, this paper considers the prospects for the latter including pyrolysis and gasification. The fundamentals of these two processes are described to better understand how they would be integrated with carbon removal. Characteristics of pyrolysis and gasification are related to the kinds of sequestration agents they would produce, the scale of their deployment, the fraction of biomass carbon that could ultimately sequestered, the challenges of effectively sequestering these different forms of carbon and the economics of thermochemical carbon negative energy. [ABSTRACT FROM AUTHOR]

Pyrolysis for Energy Technologies: The studies assembled in this Special Issue of Energy Technology highlight the prospects and challenges of improved pyrolysis technologies for renewable fuel and chemical production. We thank all of our contributors and hope that our readership will share our excitement about this Special Issue. [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]

This study evaluated the impact of biomass properties on the pyrolysis product yields, economic and environmental performance for the pyrolysis-biochar-bioenergy platform. We developed and applied a fast pyrolysis, feedstock-sensitive, regression-based chemical process model to 346 different feedstocks, which were grouped into five types: woody, stalk/cob/ear, grass/plant, organic residue/product and husk/shell/pit. The results show that biomass ash content of 0.3–7.7 wt% increases biochar yield from 0.13 to 0.16 kg/kg of biomass, and decreases biofuel yields from 87.3 to 40.7 gallons per tonne. Higher O/C ratio (0.88–1.12) in biomass decreases biochar yield and increases biofuel yields within the same ash content level. Higher ash content of biomass increases minimum fuel selling price (MFSP), while higher O/C ratio of biomass decreases MFSP within the same ash content level. The impact of ash and O/C ratio of biomass on GHG emissions are not consistent for all feedstocks. [ABSTRACT FROM AUTHOR]

Co-pyrolysis of red oak and high density polyethylene (HDPE) was conducted in a laboratory-scale, continuous fluidized bed reactor in a temperature range from 525 to 675 °C. Pyrolysis products, including two fractions of pyrolysis-oil, non-condensable gases and char were analyzed to assess the influence of pyrolysis temperature and co-feeding of biomass with HDPE. It was found that increasing pyrolysis temperature up to 625 °C promoted the production of pyrolysis-oil and its yield reached 57.6 wt%. Further increase in pyrolysis temperature caused the cracking of pyrolysis-oil to form light gases rich in hydrocarbons. Organic phase of pyrolysis-oil produced from plastic-biomass mixture (PBM) had a higher heating value (HHV) up to 36.6 MJ/kg contributed by the additive effect of HDPE-derived aliphatic hydrocarbons. A significant synergetic effect was also observed during co-pyrolysis. Co-pyrolysis with HDPE increased the production of furan, acids and water from red oak. Co-presence of HDPE also inhibited char formation from red oak and improved the HHV of the resulting char. The char produced from co-pyrolysis had a significantly lower BET surface area than red oak biochar. Not only did HDPE-derived particulate matter blocks the pores, the synergetic interaction also resulted in the formation of large and shallow micro-pores on the char surface. [ABSTRACT FROM AUTHOR]

Abstract: The objective of this study was to compare the mass and energy balances for a conventional air blown fluidized bed gasifier and a ballasted fluidized bed gasifier developed at Iowa State University. The ballasted gasifier is an indirectly heated gasifier that uses a single reactor for both combustion and pyrolysis. Heat accumulated in high-temperature phase change material during the combustion phase is released during the pyrolysis phase to generate producer gas. Gas composition, tar and char contents, cold gas efficiency, carbon conversion, and hydrogen yield per unit biomass input were determined as part of these evaluation. During the pyrolysis phase of ballasted gasification, higher volumetric concentrations of hydrogen and methane were obtained than during air blown gasification. Hydrogen yield for ballasted gasification was 14gkg−1 of biomass, which was about 20% higher than that obtained during air blown gasification. The higher heating value of the producer gas also reached higher levels during the ballasted pyrolysis phase than that of air blown gasification. Heating value for air blown gasification was 5.2MJm−3 whereas the heating value for the ballasted pyrolysis phase averaged 5.5MJm−3, reaching a maximum of 8.0 MJ m−3. The ballasted gasifier was expected to yield producer gas with average heating value as high as 15MJm−3 but excessive use of nitrogen to purge and cool the fuel feeder system greatly diluted the producer gas. Relatively simple redesign of the feeder system would greatly reduce the use of purge gas and may increase the heating values to about 17.5MJm−3. Higher char production per kilogram of biomass was associated with the ballasted system, producing 140gkg−1 of biomass compared to only 53gkg−1 of biomass during air blown gasification. On the other hand, tar concentrations in the producer gas were 6.0gm−3 for ballasted gasification compared to 11.7gm−3 for air blown gasification. On balance, carbon conversion was found to be higher for air blown gasification. Cold gas efficiencies were somewhat higher for air blown gasification compared to ballasted gasification, although the difference did not appear to be significant. [Copyright &y& Elsevier]

Abstract: Processing bio-oil with the help of currently existing petroleum refinery infrastructure has been considered as a promising alternative to produce sustainable fuels in the future. The feasibility of bio-oil production and upgrading processes depend upon its chemical composition which in turn depends on the biomass composition and the process conditions of the fast pyrolysis reactions. The primary goal of this paper was to investigate the effect of mineral salts including mixtures of salts in the form of switchgrass ash on the chemical speciation resulting from primary pyrolysis reactions of cellulose and to gain an insight of the underlying mechanisms. Various concentrations of inorganic salts (NaCl, KCl, MgCl2, CaCl2, Ca(OH)2, Ca(NO3)2, CaCO3 and CaHPO4) and switchgrass ash were impregnated on pure cellulose. These samples were pyrolyzed in a micro-pyrolyzer connected to a GC–MS/FID system. Effects of minerals on the formation of (a) low molecular weight species – formic acid, glycolaldehyde and acetol, (b) furan ring derivatives – 2-furaldehyde and 5-hydroxy methyl furfural and (c) anhydro sugar – levoglucosan are reported exclusively. Further, the effect of reaction temperature ranging from 350 to 600°C on the pyrolysis speciation of pure and ash-doped cellulose is also reported. The pyrolysis speciation revealed the competitive nature of the primary reactions. Mineral salts and higher temperatures accelerated the reactions that led to the formation of low molecular weight species from cellulose as compared to those leading to anhydro sugars. [Copyright &y& Elsevier]

Devolatilization kinetics were determined using a modified micropyrolyzer reactor for several biomass feedstocks: switchgrass, corn stover, red oak, and pine. The micropyrolyzer was directly coupled to a flame ionization detector (FID) to track the release of volatiles from the biomass. Time series data from these experiments was analyzed to determine apparent devolatilization rates. Care was taken to assure the experiments were isothermal and kinetically limited calculating a Biot number less than 0.1 and pyrolysis numbers greater than 10, which simplifies the derivation of devolatilization rates. A single, first order reaction was able to model devolatilization rates at temperatures up to 500 °C. No correlation was found between the inorganic content of the biomass and its rate of devolatilization. Apparent activation energies were in the range of 54.9–88.4 kJ mol−1. The rate coefficient at 500 °C was calculated as 1.90–5.14 s−1 for the four feedstocks. • Devolatilization kinetics were determined for four biomass feedstocks. • A single global rate accurately modeled formation of pyrolytic vapors. • Apparent devolatilization activation energies were in the range of 54.9–88.4 kJ mol−1. • Biomass inorganic content did not affect devolatilization rates. [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]

Abstract Thermochemical processing is a promising method for the rapid depolymerization of biomass. This study investigated switchgrass, corn stover, red oak, hybrid poplar, and loblolly pine in terms of heteropolymer and elemental composition, and the distribution and composition of the fast pyrolysis products. Corn stover differed from other biomass types in that less of the biomass was recovered as sugar or phenolic oil (PO) and more of the biomass was recovered as bio-char and bio-gas. The sugar-rich aqueous stream recovered from the bio-oil heavy fraction was characterized in terms of sugar content and distribution, inhibitor content, and ability to support production of ethanol by Escherichia coli KO11 + lgk as a model biorenewable product. Levoglucosan was the most abundant sugar from each type of biomass, followed by either xylose or cellobiosan. For hybrid poplar, cellobiosan accounted for 30 wt% of the total sugar pool. Each of the sugar streams also contained a variety of inhibitors, particularly 5-hydroxymethylfurfural (5-HMF) and methylcyclopentenolone. Methylcyclopentenolone, maple lactone, was found to decrease the specific growth rate of E. coli by 50% when present at 0.72 wt%, indicating that it is less toxic than furfural, acetic acid and guaiacol. Sugars produced from switchgrass contained 4-fold less contaminants on a per-sugar basis than those from poplar and pine. All of the sugar streams contained too many inhibitors to be used at an industrially feasible concentration without additional detoxification. The poplar-derived pyrolytic sugar syrup was particularly inhibitory, possibly due to the high abundance of aromatic hydrocarbons, such as xylenes, and anisoles. Highlights • Corn stover pyrolysis produced less sugar or phenolic oil than other biomass types. • Maple lactone is abundant in pyrolytic sugars, but its toxicity to E. coli is low. • Sugar syrup derived from poplar showed high toxicity to ethanologenic E. coli. • Xylene and anisole content trends with observed toxicity of sugar stream. • Anhydrosugar distribution differs between biomass types. [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]

Char is formed as a significant product from the pyrolysis of biomass, and it is well reported that lignin is the greatest contributor to the production of char. The structures of lignin chars are well studied in literature; however, an elucidation on the lignin char formation mechanism is lacking and this is essential to achieve precise control of biomass thermal conversion. In this work, the char growth process from β-O-4 linkage derived lignin monomers was investigated using density functional theory (DFT) and validated by slow pyrolysis experiments and Nuclear Magnetic Resonance (NMR) analysis. It was shown that char forms in a two-step process, beginning with the aggregation of two mono-aromatic species to yield tricyclic species, which then participate in further ring forming reactions to yield larger aromatic clusters. The side products generated involve hydrogen, water, methanol, and formaldehyde. Insights from the proposed mechanism are important for guiding future research on char formation during biomass thermochemical conversion processes. • The formation mechanism of char from lignin monomers was investigated. • An initiation step is found involving Diels-Alder cycloaddition and eliminations. • The char structure is further growing through cluster aggregation. • The mechanism is proposed from Density Functional Theory calculations. • Experimental validation based on pyrolysis and NMR are included. [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]

In situ catalytic fast pyrolysis (CFP) of biomass was conducted with base or acid catalysts in a bench-scale fluidized bed pyrolyzer. Complete mass balances were performed, allowing for quantitatively investigating the catalytic impacts on the final bio-oil composition. Acidic catalysts exhibited relatively higher activities for decomposition of sugar and pyrolytic lignin, dehydration, decarbonylation, and coke formation, as relative to base catalysts. Carbon balances revealed that a significant amount of carbon in bio-oil was transformed to coke during CFP. Due to the decrease in the bio-oil yield during CFP, significantly less energy was recovered in CFP products than in control fast pyrolysis products. CFP was also performed in micropyrolyzer and the results were compared with those in the bench-scale reactor to determine the consistency across the experimental systems. Different from the bench-scale pyrolyzer, the basic catalyst more strongly influenced the micropyrolyzer products and the discrepancies suggest a more rapid deactivation of the basic catalyst. [ABSTRACT FROM AUTHOR]

A new method was developed for collecting, identifying and quantifying contaminants in hot process gas streams using time-weighted average (TWA) passive sampling with retracted solid-phase microextraction (SPME) and gas chromatography. The previous lab scale proof-of-concept with benzene was expanded to include the remaining major tar compounds of interest in syngas: toluene, styrene, indene, and naphthalene. The new method was tested on high T (⩾100 °C) process gas from a pilot-scale fluidized bed gasifier feeding switchgrass and compared side-by-side with conventional impingers-based method. Fourteen additional compounds were identified, representing 40–60% improvement over the conventional method’s detection capacity. Differences between the two methods were 1–20% and as much as 40–100% depending on the sampling location. Compared to the inconsistent conventional method, the SPME-TWA offered a simplified, solvent-free approach capable of drastically reducing sampling and sample preparation time and improving analytical reliability. The improved sensitivity of the new method enabled identification and quantification of VOCs beyond the capability of the conventional approaches, reaching concentrations in the ppb range (low mg/m 3 ). RSDs associated with the TWA-SPME were <10%, with most lab-based trials yielding <2%. Calibrations were performed down to the lowest expected values of tar concentrations in ppb ranges (low mg/N m 3 , with successful measurement of tar concentrations at times >4000 ppm (up to 10 g/N m 3 ). The new method can be a valid alternative to the conventional method for light tar quantification under certain conditions. The opportunity also exists to exploit TWA-SPME for process gas streams analysis e.g., pyrolysis vapors and combustion exhaust. [ABSTRACT FROM AUTHOR]

The effect of alkali and alkali earth metals (AAEMs) on yields of hydrocarbons from catalytic pyrolysis of biomass was investigated. Experiments were performed in a tandem micro-reactor that segregates the biomass from the zeolite catalyst ( ex-situ catalytic pyrolysis). It was found that even trace amounts of AAEMs added to cellulose as acetate salts dramatically reduced the yields of hydrocarbons. Both the concentration and types of AAEM salts impacted product distribution. The yield of aromatics and olefins decreased monotonically with increasing concentration of AAEMs. The effect of AAEMs on reducing hydrocarbon yields followed the order: K + > Na + > Ca 2+ > Mg 2+ . Two pretreatments of biomass were investigated to alleviate the catalytic effects of AAEMs that naturally occurs in biomass: acid-washing and acid-infusion. It was found that pretreated biomass increased yields of hydrocarbons apparently by suppressing reactions that would otherwise convert carbohydrate to non-condensable gases and char. [ABSTRACT FROM AUTHOR]

Syngas from biomass and coal gasification contains ammonia (NH 3 ) and hydrogen cyanide (HCN) that originate from fuel bound nitrogen (FBN). Despite being minor constituents of the syngas, they are of great interest. They represent NO X precursors when the syngas is burned for process heating or IGCC applications and catalyst poison if the syngas is to be converted to fuels or chemicals. Measuring NH 3 and HCN via wet chemical methods can be challenging and laborious, which may account for the relative paucity of NH 3 and HCN measurements reported in the literature. Three frequently cited studies report HCN yields that are insignificant regardless of operating conditions and biomass feedstock types. These studies have been cited by other authors as justification for not measuring HCN in studies of nitrogen evolution during gasification. Other authors have reported much higher yields of HCN, on the order of a few tens of percent. Tellingly, sample collection methods are distinctive for these two ranges of HCN measurements. The present study investigated the analytical methods underlying these results, and found the lower numbers to be the result of flawed sampling methodologies. [ABSTRACT FROM AUTHOR]

Highlights: [•] The effect of pyrolysis temperature on recovery of various products collected in stage fractions (SF) was investigated. [•] The highest moisture content, over 91% total moisture, was collected in SF 5 at 550°C. [•] The majority of sugars were collected in SF 1–2 with the maximum production at 450°C. [•] Highest production of phenolic compounds occurred at 400°C at 29.4wt% db with most collected as oligomers in SF 1–2. [•] Relative molecular weight distribution of the majority of heavy ends bio-oil (SF 1–2) ranged from monomers to tetramers. [ABSTRACT FROM AUTHOR]

With appropriate pretreament, sugars can be a major product from fast pyrolysis of lignocellulosic biomass. Analytical pyrolysis of pure cellulose can produce up to 60 wt% yield of levoglucosan although yields are significantly lower in continuouos pyrolysis at larger scales. Secondary reactions of vaporized levoglucosan are thought to be responsible for this loss of sugar yield, suggesting changes in the design and operation of pyrolysis reactors to minimize these reactions. Micropyrolysis experiments were performed to better understand the mechanism of sugar degradation in the presence of biochar. A 57% loss in levoglucosan yield was observed for cellulose overlain with untreated biochar powder compared to the pure cellulose control sample. The addition of biochar derived from pyrolysis of untreated corn stover to a fluidized bed pyrolyzer reduced sugar yields from cellulose from 61.3 wt% to 21.3 wt% and 41.5–11.6 wt% for conventional and autothermal operation, respectively. The significant drop in sugar yield due to biochar interaction inspired change in feeder configuration for the fluidized bed pyrolyzer to reduce vapor-char interactions. Biomass feeding was changed from in-bed to above-bed injection, which allowed signficant devolatilization to occur above the layer of biochar that exists at the surface of the bed. By reducing secondary reactions, bio-oil and sugar yields increased by 7.9% and 14%, respectively, for autothermal pyrolysis. • We hypothesize that char reduces sugar yields during pyrolysis. • Micropyrolysis and fluidized bed pyrolysis experiments tested this hypothesis. • Biochar reduced sugar yields up to 72%. • Switching from in-bed to above-bed injection increased sugar yields. [ABSTRACT FROM AUTHOR]

• Intensification of sugar production from low ash wood possible with ferrous pretreatment. • Improved oxidation of char reduces oxygen demand of autothermal pyrolysis. • Increased ferrous catalyst loading required for biomass high in S-lignin. • Low ash biomass requires addition of ferrous acetate to prevent char agglomeration. Passivation of naturally occurring AAEM in biomass enhances sugar yields from the fast pyrolysis of biomass by preventing these metals from catalyzing the fragmentation of pyranose rings in cellulose and hemicellulose. However, because AAEM also catalyzes lignin depolymerization, its passivation can be accompanied by undesirable char agglomeration. Pretreatment of biomass with ferrous sulfate both passivates AAEM and substitutes ferrous ions as lignin depolymerization catalysts. This pretreatment has been particularly successful for high ash biomass like corn stover, but of limited value for low ash biomass like wood. This study explores the reasons for this discrepancy and offers a combined pretreatment of ferrous sulfate and ferrous acetate pretreatment to overcome char agglomeration in wood. This new pretreatment increased sugar yields from 4.4 wt% to 15.5 wt% and 5.4 wt% to 19.0 wt% for hardwood and softwood biomasses, respectively. This pretreatment produces an iron-rich biochar that catalyzes oxidation of the biochar under the oxygen-rich conditions of autothermal pyrolysis, which is preferentially consumed to provide the enthalpy for pyrolysis, preserving bio-oil as a more desirable energy product. Instead of producing carbon monoxide, which dominates oxidation of biochar from untreated biomass, the iron catalyzes oxidation to carbon dioxide, producing more energy per mole of oxygen consumed. In fact, oxygen demand to support autothermal pyrolysis of red oak and southern yellow pine was reduced 15% by the presence of iron in the biochar. [ABSTRACT FROM AUTHOR]

Abstract: The goal of this research is to produce high concentrations of hydrogen from gasification of biomass. Air-blown gasification of biomass in fluidized bed reactors produces relatively low concentrations of hydrogen (about 8 vol.%). Steam reforming of tars and light hydrocarbons and reacting steam with carbon monoxide via the water–gas shift reaction can increase hydrogen content in the producer gas to almost 30 vol.%. In these experiments, the temperature, space velocity, and steam/gas ratio were varied to determine the effect of these variables on hydrogen production. Characterization of the catalysts by X-ray photoelectron spectroscopy (XPS) and BET analysis was also performed. These analyses showed that coke and small quantities of sulfur and chlorine deposited on the catalysts, although catalytic deactivation was not evident during the tests. [Copyright &y& Elsevier]

• Phenolic oligomers were analysed to determine influence of oxidative environment. • Elemental analysis indicated no significant difference between conditions. • NMR analyses measured a decrease in hydroxyl groups and an increase in carbonyls. • Model compound experiments found oxidation state effects gas phase polymerization. Fast pyrolysis is traditionally defined as the rapid decomposition of organic material in the absence of oxygen to produce primarily a liquid product known as bio-oil. However, the introduction of small amounts of oxygen to the process holds prospects of internally generating the energy needed for pyrolysis. The present study investigates the partial oxidation of lignin-derived compounds during pyrolysis, which generates both carbon oxides and aromatic carbonyl compounds. Analysis of lignin derived phenolic compounds was performed to determine if the composition had changed under oxidative conditions. NMR analyses indicates aromatic carbonyls increased under oxidative conditions, with a corresponding decrease in phenolic hydroxyl groups. Model phenolic compounds were pyrolyzed to help understand the role of partial oxidation during autothermal pyrolysis of lignocellulosic biomass. [ABSTRACT FROM AUTHOR]

• A method for monitoring product evolution during pyrolysis was demonstrated. • Results provide direct visual evidence of dominant transport mechanisms. • Laser scattering images monitor in situ volatile product evolution and condensation. • Vapor-phase transport of products dominates in whole biomass and cellulose. • Lignin coalescence after liquefaction leads to thermal ejection of droplets. The thermochemical conversion of biomass via fast pyrolysis requires detailed descriptions of both the kinetic and heat and mass transport rates, which are often in direct competition. To investigate the evolution of products, whole biomass and biomass constituents (e.g. cellulose and lignin) are pyrolyzed in a novel optically accessible reactor. This enables real-time, in situ observation of the temporal evolution of light-oxygenates, volatile sugars, and phenolic compounds during melting, agglomeration, ejection, and volatilization of biomass under realistic heating rates (∼100 K/s). Both cellulose and lignin underwent liquefaction, but liquid coalescence in lignin limits vapor transport. This is overcome by dispersing extracted lignin in an inert matrix, and confirms the predominant mass transport of pyrolysis products from whole biomass, cellulose, and lignin occurs via devolatilization. These results differ from prior work on single-particle pyrolysis and reveal thermochemical mechanisms that are relevant for typical large-scale pyrolysis processes with transport limitations. [ABSTRACT FROM AUTHOR]

Abstract: This analysis compares capital and operating cost for six near-term biomass-to-liquid fuels technology scenarios representing three conversion platforms: pyrolysis, gasification, and biochemical. These analyses employed similar assumptions to allow comparisons among the results. Most prominently, the feedstock is assumed to be corn stover and plant capacity was 2000tonne/day for each plant. There are large differences in the total capital investments required among the three platforms. The stand-alone biomass-to-liquid fuel plants are expected to produce fuels with a product value in the range of $2.00–5.50per gallon ($0.53–1.45per liter) gasoline equivalent, with pyrolysis the lowest and biochemical the highest. These relatively high product values are driven primarily by an assumed feedstock cost of $75per dry ton and the cost of capital for the plants. Pioneer plant analysis, which takes into account increased capital costs and decreased plant performance associated with first-of-a-kind plants, increases estimated product values to $2.00–12.00per gallon ($0.53–3.17per liter) gasoline equivalent. [ABSTRACT FROM AUTHOR]

Abstract: This study compares capital and production costs of two biomass-to-liquid production plants based on gasification utilizing 2000 dry Mg per day of corn stover. The focus is to produce liquid transportation fuels with electricity as co-product using commercially available technology within the next 5–8years. The first biorefinery scenario is a low temperature (870°C, 1598°F), fluidized bed gasifier and the second scenario a high temperature (1300°C, 2372°F), entrained flow gasifier both followed by catalytic Fischer–Tropsch synthesis and hydroprocessing. The scenarios were modeled and investment costs estimated. A discounted cash flow rate of return analysis was performed to determine a fuel product value (PV). The analysis shows that despite higher investment costs for the high temperature gasification scenario, a lower PV results due to higher fuel yield. These nth plant scenarios are expected to produce fuels with a PV in the range of $4–5 per gallon of gasoline equivalent ($1.06–1.32 per liter) and require $500–650 million capital investment. Main factors responsible for this relatively high PV are feedstock cost and return on capital investment. Biomass-to-liquid based on gasification has yet to be commercialized. Hence, a pioneer plant is expected to be more costly to build and operate than an nth plant. Pioneer plant analysis found PV to increase by 60–90% and capital investment to more than double. [ABSTRACT FROM AUTHOR]