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This paper reports the co-hydrotreatment of the heavy bio-oil fraction with waste cooking oil (WCO) using the NiMo/γ-Al2O3catalyst, followed by the distillation of the resulting deoxygenated oil and the characterization of the resulting fuel cuts. The heavy Biomass Technology Group (BTG) bio-oil fraction was obtained by removing the very reactive light-oxygenated compounds via rotary evaporation and subsequently mixed with 1-butanol. The resulting oil was blended with WCO and subjected to a two-step co-hydrotreatment process. The first step, called “stabilization,” was aimed at saturating highly reactive hydrogen-deficient compounds. The second step, called “deoxygenation,” aimed to remove bio-oil oxygen, primarily as H2O. This study examined the impact of varying bio-oil concentrations (0, 10, 20, 30, 40 wt % of WCO) on the upgraded oil’s yield, composition, and fuel properties. The resulting hydrotreated oil was distilled into gasoline-range, kerosene-range, and diesel-range hydrocarbons at <150, 150–250, and 250–350 °C, respectively. The yield of the hydrotreated oil indicated that as the bio-oil concentration increased, the amounts of coke (0.7–2.4%) and water (2–10 wt %) increased, while the organic layer yields decreased (80–63%). The coke yield was comparable to the coke yield obtained when co-processing the pyrolytic lignin fraction. This suggested that coke was formed from both the sugar oligomers and the lignin-derived oligomers. The UV fluorescence analysis on the hydrotreated oil showed that more polycondensed and conjugated ring compounds formed as the bio-oil concentration was increased. These compounds are precursors of coke. Fourier transform infrared spectroscopy (FTIR) results showed that most raw materials were converted to biofuels after the hydrotreatment. To achieve less than 1 wt % of coke yield, blends with up to 20 wt % pyrolysis oil should be used. An increase in the bio-oil concentration led to a slight increase in the gasoline yield and a decrease in kerosene and diesel yields. The identified carbon species found in the fuel cuts included n-paraffin, iso-paraffin, cycloparaffin, and aromatics. Further, the jet fuel cut (kerosene) was characterized by density, surface tension, and viscosity. Our product conforms to the standard specifications for sustainable aviation fuels (Jet A-1). Further research is suggested to fine-tune the operating parameters for achieving reduced coke yield and enhanced kerosene yield.

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The presence of heavy unknown oligomeric sugar products in bio-oil is evidenced in experimental results reported in the literature. In this paper, we study the fragmentation reactions yielding hydroxyacetone and hydroxyacetaldehyde from oligomeric sugars following previous work on dehydration reactions to propose structures of these oligomers. Hydroxyacetone and hydroxyacetaldehyde are primary products of cellulose fast pyrolysis, but the fragmentation reaction mechanism of these compounds from oligomers merits further study. The density functional theory approach was employed to study this reaction. Results revealed that hydroxyacetone and hydroxyacetaldehyde fragments are more favorably removed from the nonreducing end based on their thermodynamic stabilities. As a result of this study, we proposed new potential structures of unknown oligomeric sugars. Theoretical FTIR and NMR spectra were calculated so that in the future when these molecules are separated their experimental spectra and the theoretical ones herein reported can be used to confirm the structures of these oligomeric sugars. Also, the thermodynamics and physical properties of these compounds were estimated by using the group contribution method. These properties are essential in the design of technologies for bio-oil refining.

Although major differences in thermal stability and hydrotreatment behavior of hydrothermal liquefaction (HTL) and pyrolysis oils have been reported, little is known about the variations in the chemical composition of these oils that could explain such differences. Two commercial softwood pyrolysis oils [Pyrovac and Biomass Technology Group (BTG)] and their water-soluble (WS) and water-insoluble (WIS) fractions were analyzed and compared with the aqueous (WSWD-57) and oily (WISWS-57) fractions obtained from HTL of Douglas-fir. The samples were characterized by GC–MS, Karl Fischer titration, carbonyl content, total acid number, elemental composition, calorific value, proximate analysis, Fourier transform infrared spectroscopy, Folin–Ciocalteu (FC), and UV fluorescence. Fourier transform ion cyclotron resonance mass spectrometry (ICR-MS) and electrospray ionization mass spectrometry (ESI-MS) were also used to analyze the fractions. The most prevalent class of compounds in the WIS phases was phenols. WS phases contained mainly oxygenated compounds derived from cellulose and hemicellulose and were richer in the carbonyl functional group. The water content of the resulting aqueous phases was 65 (WBTG) and 96 (WSPyrovac) wt %. The bio-oil from BTG has higher water content and lower high heating value compared to Pyrovac oil. According to the GC–MS results, BTG oil contained more acetic acid and higher TAN number than the Pyrovac oil, while Pyrovac oil was mainly composed of monophenols. The higher number of monophenols in the Pyrovac oil was also confirmed by the FC method. Although the UV fluorescence spectra, ICR-MS, and the ESI-MS analyses showed some minor differences in the molecular weight and chemical make-up of the oligomers soluble and insoluble in water from pyrolysis and HTL, the differences observed were not significant enough to justify the differences in hydrotreatment behavior between these oils reported in the literature.

This paper reports the co-hydrotreatment of Biomass Technology Group commercial pyrolysis oil water-insoluble (WIS) phase (also known as pyrolytic lignin) and yellow greases (waste cooking oil), aiming to produce sustainable aviation fuels (SAFs). We use a sulfided NiMo/Al2O3blend with 16 wt % WIS and a central composite experimental design to identify processing conditions increasing kerosene yield and reducing coke formation. The input variables were: (1) reaction temperature (320, 350, and 380 °C), (2) initial hydrogen pressure (5, 6, and 7 MPa), and (3) amount of catalyst (0.7, 1.0, and 1.3 g). The hydrotreated oily phases were distilled to obtain gasoline (<150 °C), kerosene (150–250 °C), diesel (250–350 °C), and residual oil (>350 °C). The reaction temperature is the main factor affecting the yield of gaseous, solid, and liquid products. Meanwhile, a higher initial hydrogen pressure and catalyst loading increased the yield of kerosene and other distillates and decreased the coke formation. A high temperature correlated with a lower content of oxygenates in kerosene cuts. Based on our experimental results, we propose to conduct hydrotreatment studies at 380 °C, initial H2pressure of 7 MPa, and 1.3 g of catalyst. Under the identified conditions, it was possible to improve the kerosene yield to more than 20 wt % and reduce the yield of coke to close to 2.0 wt %. The chemical composition and fuel properties of the gasoline, kerosene, and diesel cuts were thoroughly analyzed. The content of aromatics and phenols in the kerosene fraction produced at the conditions identified in this project exceeded the recommended values for SAFs. New strategies (such as blending and more intense hydrotreatment to remove oxygenated compounds) need to be implemented to reduce the content of these molecules in our final product.

Research on using biochar for environmental applications has witnessed unprecedented advances in the past decade. Biochar is universally considered one of the best alternatives to store carbon to fight global warming. Thus, the sequential use of biochar in environmental remediation compatible with carbon sequestration is receiving growing attention. One of the reasons for such huge interest is the possibility to engineer biochar with targeted properties (e.g., surface area and chemistry) relevant to existing environmental issues. These properties can be achieved by selecting appropriate raw materials, processing conditions, carbonization technology, and the possibility of selecting postproduction modification approaches. The objective of this review is to summarize strategies to enhance biochar properties relevant to its use in environmental services (e.g., water purification, air/gas cleaning, construction materials, soil amendments) and the corresponding results on the use of this material for these applications. The main methods for enhancing biochar properties for environmental applications reviewed include activation (physical and chemical), oxidation, metal and metal oxide modification, metal-free heteroatom doping, and biological modification. Both modified and unmodified biochars have been used for soil amendments as adsorbents of pollutants in the aqueous phase (e.g., removal of P and N, heavy metals, and organic pollutants), adsorbents of pollutants in the gas phase (e.g., biogas cleaning), as a catalyst, as an additive for improving anaerobic digestion, and as an admixture to cementitious/construction materials, with promising results in all cases. New opportunities for using biochar are being reported as the science of biochar production, modification, and use advances.

Aqueous phase (AP) is frequently observed in bio-oil from biomass thermochemical conversion or as an upgrading coproduct. However, AP contains high organic content that can be toxic and that must be reduced or removed to be then treated in existing wastewater plants. A promising method to upgrade these APs is the catalytic wet peroxide oxidation (CWPO) that was applied here on APs of both hydrothermal liquefaction and pyrolysis bio-oils from softwood and hardwood. Efficiency of the CWPO was assessed by investigating the molecular composition of raw and treated APs by ultra-high-resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) with electrospray ionization (ESI) in negative- and positive-ion modes. Combination of FT-ICR MS and multivariate statistical analyses evidenced efficiency of the process with new compounds resulting from the oxidative depolymerization, characterized by lower unsaturation degree and molecular weight, and higher oxygen atom count. Refractory compounds were also observed, which are notably characterized by high unsaturation degrees. Interestingly, both detection modes were shown to be complementary for the understanding of the CWPO process. ESI (-) allowed to assess the completion of the oxidation process in detecting carboxylic acid conversion products and to specifically evidence refractory products. ESI (+) was informative on the CWPO process, especially on the conversion of the basic compounds, with the decrease of the detected species. Eventually, softwood AP was shown to be more reluctant to CWPO than the hardwood one.

The production of renewable fuels and chemicals is a critical component of global strategies to reduce greenhouse gas emissions. In this regard, pyrolysis oil obtained from biomass comprises hundreds of chemical compounds, thus rendering it a good precursor for manufacturing a variety of fuel products of commercial interest. Despite the large number of contributions describing the products’ extraction, upgrading, and potential refining schemes, no bio-oil refinery is currently in operation. The main challenge in building a bio-oil refinery lies in the lack of an economically viable process configuration. Systematic studies comparing alternative refinery concepts, or configurations, are needed to identify the most promising configuration. To the best of our knowledge, this study is the first to use process graph (P-graph) methodology for the synthesis of pyrolysis oil refineries. In particular, this work shows the effectiveness of P-graph methodology in simultaneously calculating the profitability of various biorefinery designs by using data reported in the literature and providing information on how the introduction of new technologies to the database will impact the formation of profitable biorefinery concepts. Our work demonstrates a methodology for the addition of new unit operations to the database generated from the literature. The addition of a centrifuge for water extraction and a wet oxidation system for acetic acid production resulted in the generation of 330 biorefinery configurations, seven of which have a profitability ranging from $1,650 to $23,666/h (USD) with acetic acid and levoglucosan as the main products, respectively. This demonstrates that P-graph methodology is useful for discovering optimum techno-economic scenarios that may otherwise be overlooked.

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.

Another opportunity for circularity involves integrating the current pork supply chain with alternative protein markets, including cell-based animal protein, in a sharedresource arrangement that supports both types of production, because both types of production rely on live animals. E ach year, approximately 200 million pigs are produced for consumption in the U.S., yielding 12.5 billion kg of pork products. Animal production and cell-cultured meat production require many of the same inputs, creating potential for combined systems in which total food production can increase while adapting to changing markets and consumer preferences more rapidly than either system could alone. [Extracted from the article]

Current animal production and processing systems have benefitted from vast improvements in efficiency to meet ever-growing consumer demands. U.S. per capita availability of beef, pork, chicken, and fish. and reduce the physical and psychological distances between food production and consumers. Larger animals also remain in the system longer, so beef production facilities face different challenges. In contrast, beef production has large and small operations in different parts of the production system, many different entities make major decisions across the system, and there is much greater interaction between the cattle and the natural environment. [Extracted from the article]

Separating bio-oil by fractionation with different chemical compositions is a critical step to refine these oils and obtain high-value products. Cold water precipitation of pyrolytic lignin from bio-oil is the most common approach used. However, the obtained aqueous phase from this method still contains phenols and is diluted and difficult to use. In this study, the use of liquid–liquid extraction with different solvents (1-butanol, ethyl acetate, 1-octanol, dichloromethane, toluene, and hexane) for the separation of targeted molecules (lignin oligomers, sugars, acetic acid) is explored. Ternary phase diagrams for the organic solvent/water/bio-oil are reported. The partition coefficient of compounds of interest (both light and heavy fractions) is reported for the liquid–liquid equilibrium zone. When using butanol as the solvent, the highest separation factor of total phenols over total sugars was observed. Our results provide information to design L–L separation units with the capacity to selectively recover targeted molecules from pyrolysis oils.

The pyrolysis of lignocellulosic materials is a promising technique to produce fuels and chemicals. It is well known that the most abundant products of lignin pyrolysis are oligomeric molecules, known as pyrolytic lignin (PL). The chemical composition of PL has been extensively studied; however, there is still an important debate whether these oligomers are produced directly from the lignin or from the recombination of monomeric pyrolytic products. Existing theories are unable to describe the effect of vacuum on the distribution of pyrolysis products. Hybrid poplar milled wood lignin (MWL) was initially isolated and thoroughly characterized by Fourier transform-ion cyclotron resonance mass spectrometry (FT-ICR MS). Chemical formulas were assigned to each oligomeric compound detected. The MWL was also subjected to vacuum pyrolysis in a modified pyroprobe at 250, 750, and 1000 mbar (absolute pressure), and the resulting liquid products were analyzed by FT-ICR MS. A new strategy to assign structural representations to the oligomeric PL products is proposed, based on the plausible pyrolysis reaction mechanisms of depolymerization/fragmentation applied to original MWL oligomer formulas. Our results support the hypothesis that PL is formed from the removal of moieties from primary lignin pyrolysis products with between three and five aromatic rings. This depolymerization/fragmentation allows the oligomers to reduce their molecular weights to the point where they can be removed from the reaction zone by direct vaporization. This phenomenon highlights the importance of pressure on removal mechanisms and their impact on the molecular weight of the resulting products from lignin pyrolysis.

Among the most prominent challenges for the analysis of biomass pyrolysis products is the characterization of the abundant oligomer fraction of bio-oil. This fraction is principally made up of pyrolytic lignins and dehydrated, highly modified sugar oligomers, called humins, in liquid phase. An emerging technique for analysis of this oligomer fraction is high-resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS), which allows for accurate determination of CxHyOzformulas for detected oligomers. Additionally, using simple dehydration and fragmentation reaction schemes, similar formulas can be developed from cellulose-, hemicellulose-, and lignin-derived oligomers, which are primary depolymerization products. In this study, FT-ICR MS analysis is coupled with combinatoric dehydration and fragmentation modeling to match experimentally detected bio-oil oligomers with hypothetical pathways for their formation during pyrolysis. In this way, we present a novel strategy by which oligomeric structures can be proposed for bio-oils. Using this approach, it becomes possible to advance the understanding of both the molecular structures comprising the bio-oil oligomer fraction and the pathways by which these structures form during biomass pyrolysis reactions.

Blends of lignin-rich oil (LRO) and vegetable oil (1:8, 1:4, 1:2, and 1:1) were prepared and hydrotreated over CoMo/Al2O3(catalyst liquid ratio of 1:50) at 623 K and 500 rpm, with 9.3 MPa of cold initial H2pressure for 4 h. The yield of liquid, gas, and solid products was reported. The yield of coke obtained was in all of the cases very high (between 25 and 50 wt % of the LRO processed, depending upon the LRO/vegetable oil ratio used). Most of the product from the lignin-rich fraction remained in the heavy fractions. To mitigate coke formation, blends containing 0.5 g of butanol/g of LRO studied were co-hydrotreated with vegetable oils maintaining the LRO/vegetable oil ratios. The presence of 1-butanol mitigated coke formation, but it did not translate in the production of distillable fractions; the LRO contributed to the formation of a heavy oil. The LRO needs to be stabilized and cracked before co-deoxygenation. Cracking/stabilization studies in the presence of butanol and methanol were conducted over Ni/SiO2–Al2O3at 473 K with 9.3 MPa of cold H2pressure for 24 h. The best results were obtained with the oils stabilized in the presence of butanol. The yield of coke formed decreased from 34.7 wt % on LRO basis to 6.65 wt %. The behavior of the stabilized/cracked LRO/vegetable oil blends (1:4) in terms of the product yield was comparable to the yields obtained when vegetable oil was deoxygenated alone. The solid residue (coke) increased from 0.04 wt % when vegetable oil was processed alone to 1.13 wt % when a 1:4 blend of stabilized/cracked lignin/vegetable oil was co-processed. Lower coke yields may be obtained in continuous co-hydrotreatment reactors.

Lignin liquefaction microkinetics is a move toward a more first-principles (i.e., ab initio)-based understanding at the molecular level in reaction engineering. While the microkinetic modeling of reactions to obtain kinetic rate parameters of chemical reactions have been widely used in the field of gas phase combustion and heterogeneous catalysis, this approach has not been as thoroughly developed in the area of biomass thermochemical reactions (e.g., lignin pyrolysis, hydrothermal liquefaction). The difficulties in establishing the structure of complex heterogeneous materials, like lignin, is perhaps the main challenge in developing rational microkinetic descriptions of biomass thermochemical reactions. In this manuscript, we review the current state of the art and the challenges to develop microkinetic models for lignin liquefaction technologies (e.g., pyrolysis, hydrothermal liquefaction, solvolysis). A general strategy for the development of microkinetic models for lignin liquefaction technologies is discussed. The first hurdle is to obtain sufficiently rich experimental data of lignin underlying polymeric structure and methodologies to use this data to build realistic lignin structural representations. Some analytical techniques for lignin structural characterization and their associated data, as well as a correlation for calculating the degree of macromolecular lignin branching, are discussed. The presence of small lignin oligomeric structures and the role of these structures in lignin pyrolysis is also addressed. The ways in which elementary deconstruction and repolymerization reactions occur within this structure to form a liquid intermediate and how these deconstruction products continue to interact with each other until they are removed from the liquid intermediate is thoroughly discussed. Further, experimental work with model compounds and the effect of reaction parameters (e.g., temperature, pressure, vapor residence time) are reviewed. Another major challenge to develop microkinetic models of lignin liquefaction is to describe product removal mechanisms (e.g., evaporation, solubilization, thermal ejection) from the liquid intermediate. Group contribution methods are presented for estimation of thermophysical parameters, like normal boiling point and heat of vaporization for model structures. Once the products have been removed from the liquid intermediate, they continue reacting in the aerosol droplets, in vapor phase, or in the solvent depending on the liquefaction technology studied. These “secondary reactions” need to be included in realistic microkinetic models. Based on this review, we can state that with careful implementation, high-quality microkinetic models can be developed to simulate thermochemical lignin liquefaction.

Bio-oil derived from fast pyrolysis of lignocellulosic materials is among the most complex and inexpensive raw oils that can be produced today. Although commercial or demonstration scale fast pyrolysis units can readily produce this oil, the pyrolysis industry has not grown to significant commercial impact due to the lack of bio-oil market pull. This paper is a review of the challenges and opportunities for bio-oil upgrading and refining. Pyrolysis oil consists of six major fractions (water 15–30 wt %, light oxygenates 8–26 wt %, monophenols 2–7 wt %, water insoluble oligomers derived from lignin 15–25 wt %, and water-soluble molecules 10–30 wt %). The composition of water-soluble oligomers is relatively poorly studied. In the 1880s, bio-oil refining (formally known as wood distillation) targeted the separation and commercialization of C1–C4 light oxygenated compounds to produce methanol, acetic acid, and acetone with the commercialization of the lignin derived water insoluble fraction for preserving wooden sailing vessels against rot. More recently, the company Ensyn extracted and commercialized condensed natural smoke as a food additive. Most research efforts in the last 20 years have focused on the two-step hydrotreatment concept for the production of transportation fuels. In spite of major progress, this concept remains at the demonstration scale. In this review, the opportunities and progress to separate bio-oil fractions and chemicals, mainly acetic acid (HAc), hydroxyacetaldehyde (HHA), acetol, and levoglucosan, and convert them into value added coproducts are thoroughly discussed. In spite of the large number of separation schemes and products tested, very few of them have been tested as part of fully integrated bio-oil refinery concepts. The synthesis and techno-economic and environmental evaluation of novel integrated bio-oil refinery concepts is likely to become a subject of intense research activity in the coming years.

Mo–W carbide was synthesized viatemperature-programmed reduction to generate a β-Mo2C phase with bulk morphology. The catalyst was characterized using X-ray diffraction (XRD), N2physisorption, X-ray photoelectron spectroscopy (XPS), H2-chemisorption, and ammonia temperature programmed desorption (NH3-TPD) to investigate the synergistic effect of the combination of molybdenum and tungsten in carbide. Due to the interaction of Mo–W, the bimetallic carbide exhibited a significantly higher density of H2-activating sites than the corresponding monometallic carbides prepared using the same method. In the HDO of guaiacol at 350 °C, MoWC exhibited the highest hydrodeoxygenation (HDO) activity and produced completely deoxygenated products with a selectivity of 92 mol% in which the benzene selectivity was ∼70 mol%. The superior catalytic activity is attributed to the presence of H2-activating sites and oxophilic sites. Under the testing conditions, the HDO of guaiacol over monometallic molybdenum carbide followed both direct deoxygenation (DDO) and hydrogenation–dehydration (HYD) pathways, while MoWC strongly favored the DDO route. Over 8 h on stream, the catalyst still retained a high catalytic stability.

ABSTRACTCommunity and technical colleges serve a vital function in STEM education by training workers for medium- and high-skilled technical careers and providing employers the labor necessary to operate and maintain thriving business ventures. A curriculum developed with the elements of a systems-based approach results in a program more relevant to the needs of the institution, its students, and industry partners—and avoids the pitfalls of programs designed without a plan or process in place. To achieve validity and reliability, curriculum assessment tools should be conduits to collect critical feedback from students, graduates, and the industries and academic partners served. Research was undertaken to design and evaluate an associate degree-level STEM workforce education program at the nexus of bioenergy/bioproducts, electrical systems and maintenance, and wastewater treatment plant operations. Component to the research, a program’s graduates were interviewed and professionals representing a spectrum of manufacturing/processing-type industries were surveyed. A curriculum development and assessment model emerged to help community and technical college faculty and administrators develop, evaluate, and revise associate degree-level STEM workforce education programs.

Pyrolysis oils are complex mixtures of hundreds of compounds that can be described as a mixture of few chemical macro-families. This description is highly desirable for modeling bio-oil combustion, cracking, separation, and evaporation. In one of our previous papers we recommended the deconvolution of bio-oil DTG curves as the basis for characterizing bio-oils in chemical families. However, the positioning of the peaks was based on the shape of the DTG curve. More specific guidelines are needed to position the peaks in this deconvolution strategy. In this paper we developed and tested a methodology to identify the position and shape of the peaks in the DTG curves. The first strategy uses the FTIR spectra of the TG evolved pyrolysis oil vapors. The second consists of doping the bio-oil with model compounds and with its fractions. The IR studies provided information on the position and width of the fitting curves describing the behavior of the very light volatile compounds (<150 °C) and of the heavy oligomeric fraction (>400 °C). The range between these two temperatures was fitted based primarily on the shape of the DTG curve and the results from the oil doping studies. Contribution of the chemical families toward formation of coke residue was examined based on the doping studies, and rules for coke assignment were developed. The developed DTG deconvolution method was applied to ten pyrolysis oils produced from compositionally diverse biomass feedstocks and production technologies. The chemical composition of the oils obtained by our new DTG deconvolution strategy was compared with other well accepted characterization methods. Our results show that the method proposed could be used to estimate the changes in the content of water, light volatile compounds, and water-soluble (WS) and water insoluble (WIS) fractions.

This paper reports a study of the chemical composition of the water-soluble (WS) fraction obtained by cold water precipitation of two commercial wood pyrolysis oils (BTG and Amaron). The fraction studied accounts for between 50.3 and 51.3 wt % of the oils. With the most common analytical techniques used today for the characterization of this fraction (KF titration, GC–MS, hydrolyzable sugars, and total carbohydrates), it is possible to quantify only between 45 and 50 wt % of the fraction. Our results confirm that most of the total carbohydrates (hydrolyzable sugars and nonhydrolyzable) are soluble in water. The ion chromatography hydrolysis method showed that between 11.6 and 17.3 wt % of these oils were hydrolyzable sugars. A small quantity of phenols detectable by GC–MS (between 2.5 and 3.9 wt %) were identified. It is postulated that the unknown high molecular weight fraction (30–55 wt %) is formed by highly dehydrated sugars rich in carbonyl groups and WS phenols. The overall content of carbonyl, carboxyl, hydroxyl, and phenolic compounds in the WS fraction was quantified by titration, the Folin–Ciocalteu method, 31P NMR, and 1H NMR. The WS fraction contains between 5.5 and 6.2 mmol/g carbonyl groups, between 0.4 and 1.0 mmol/g carboxylic acid groups, between 1.2 and 1.8 mmol/g phenolic −OH, and between 6.0 and 7.9 mmol/g of aliphatic alcohol groups. Translation into weight fractions of the WS was done by supposing surrogate structures for the water-soluble phenols, carbonyl groups, and carboxyl groups, and we estimated the content of WS phenols (21–27 wt %), carbonyls (5–14 wt %), and carboxyls (0–4 wt %). Together with the total carbohydrates (23–27 wt %), this approach leads to >90 wt % of the WS material in the bio-oils being quantified. We speculate the larger portion of the difference between the total carbohydrates and hydrolyzable sugars is the missing furanic fraction. Further refinement of the suggested methods and development of separation schemes to obtain and quantify subfractions with homogeneous composition (e.g., carbohydrates, high molecular weight WS phenols, furans, and dehydrated sugars) warrant further investigation.

The aim of this research was to evaluate the potential for the stabilization of biomass‐derived pyrolysis oils by using acid‐catalyzed (Amberlyst 70) reactions with alcohol (T=140–170 °C, P≈20 bar (1 bar=105Pa)). The alcohol‐stabilized oils were further upgraded by catalytic hydrotreatment (T=400 °C, non‐sulfided NiMo/Al2O3catalyst) to give a biofuel. The concept was evaluated experimentally in terms of overall mass and energy balances and biofuel properties. The pyrolysis oil used in this study was obtained by fractional condensation of pyrolysis vapors and had a very low water content that favored the equilibrium conversion of the stabilization reactions. The energy efficiency was between 44 and 48 %. Preliminary results with acid‐leached biomass showed that 43 % of levoglucosan in the pyrolysis oil was converted into methyl levulinate after the pyrolysis oil was purified. The proposed integrated concept of alcoholysis can be applied locally at the pyrolysis oil production site. Replacing hydrogen for stabilization: Biomass‐derived pyrolysis oil is stabilized by alcohol or hydrogen and a catalyst followed by deep hydrotreatment. The energy efficiency from biomass to fuel is in both cases around 46+/−2 %. Preliminary results with acid‐leached biomass show that 43 % of the levoglucosan in the pyrolysis oil is converted to methyl levulinate, after the pyrolysis oil was purified.

This paper explores the utility of large-scale atomistic models to examine the complex relationship between biochar behavior, its structural characteristics, and the reactions involved in its formation. Pyrolysis kinetic models primarily focus on explaining the formation of small volatiles and aromatic structures without fully understanding the carbonization process. To gain a deeper understanding of carbonization and move beyond unrealistic structures resembling levoglucosan, it is necessary to examine the transformation of the lignocellulosic macromolecules into carbonaceous structures from a molecular-level perspective. This includes exploring structural transitions and large-scale reactive dynamics. Furthermore, incorporating atomistic representations derived from experimental data and theoretical modeling can help overcome the limitations of relying solely on empirical and density functional theory approaches due to the need for scale to capture biochar properties. Additionally, by considering structural transitions on a large scale, we can effectively capture the complexity of biomass pyrolysis, the interaction of free radicals, and the pore size distribution, all essential for comprehending biochar reactivity and utility.

Fast pyrolysis of lignocellulosic materials is a promising research area to produce renewable fuels and chemicals. Dehydration is known to be among the most important reaction families during cellulose pyrolysis; water is the most important product. Together with water, dehydration reactions also form a range of poorly known oligomer species of varying molecular sizes, often collected as part of the bio-oil water-soluble (WS) fraction. In this work, we used electronic structure calculations to evaluate the relative thermodynamic stabilities of several oligomer species from cellulose depolymerization intermediates undergoing three consecutive dehydration events. A library of the thermodynamically favored candidate molecular structures was compiled. Results revealed that most of the water molecules are eliminated from the non-reducing end, forming thermodynamically more stable conjugated compounds. This is consistent with results reported in literature where dehydration reactions occur preferably at the non-reducing ends of oligomers. The theoretical Fourier-Transform Infrared Spectroscopy and NMR spectra of these proposed sugar oligomers conform qualitatively to the experimental result of pyrolytic sugars. Understanding their chemical structure could help to develop rational strategies to mitigate coke formation as sugars are often blamed to cause coke formation during bio-oil refining. The estimated physical–chemical properties (boiling point, melting point, Gibbs free energy of formation, enthalpy of formation, and solubility parameters among others) are also fundamental to conducting first-principles engineering calculations to design and analyze new pyrolysis reactors and bio-oil up-grading units.