Fast Pyrolysis Of Biomass Research Articles

Thermal Reactivity of Bio-Oil Produced from Catalytic Fast Pyrolysis of Biomass.

Catalytic fast pyrolysis (CFP) of biomass is a versatile thermochemical process for producing a biogenic oil that can be further upgraded to sustainable transportation fuels, chemicals, and materials. CFP oil exhibits reduced oxygen content and improved thermal stability compared to noncatalytic fast pyrolysis oil. However, some level of reactive oxygenates remain in CFP oils, and reactions between these species can result in molecular weight growth and increased viscosity, leading to the potential for challenges during transportation, storage, and downstream processing. Previous research has provided considerable insight into the reactivity of noncatalytic fast pyrolysis oils, but CFP oils have yet to be studied in a similar fashion. Consequently, the degree of catalytic upgrading that is necessary to effectively stabilize CFP oils has yet to be established, and little is known about the mechanistic details underlying the process. The current study addresses this knowledge gap by controlling the CFP reaction conditions to systematically vary the oxygen content of the resulting oil. Accelerated thermal reactivity studies were then performed, and the CFP oils were analyzed using gas chromatography-mass spectrometry (GC-MS), Fourier transform ion cyclotron mass spectrometry (FT-ICR MS), gel permeation chromatography (GPC), and viscometry to evaluate the impact of heating on their physical and chemical properties. The results revealed that short chain carbonyls, anhydrosugars, and lignin derivatives with conjugated vinyl groups likely play a role in the thermal reactivity of CFP oils. Additionally, experiments performed across a wide variety of feedstocks revealed relatively low thermal reactivity for CFP oils with oxygen contents of <20 wt %. However, above this threshold value, the thermal reactivity grew exponentially as a function of oxygen content, resulting in large increases in viscosity and molecular weight. These results serve to deepen the mechanistic understanding of CFP oil thermal reactivity and help inform the development of quality specifications for catalytic upgrading to effectively stabilize CFP oils.

Integration of energy storage and determination of optimal solar system size for biomass fast-pyrolysis

This study presents a model and analysis of a heliostat field collector (HFC) system integration with fast-pyrolysis of biomass and determination of the optimal solar system size for this integrated system. Given the intermittent nature of solar energy, an auxiliary heater and a thermochemical energy storage system (TCES) are included. Four cases of HFC integration with the fast-pyrolysis process have been studied: 1) low solar radiation, 2) sufficient solar radiation, 3) high solar radiation, and 4) no solar radiation with available stored energy in TCES. The solar energy system was modeled and calculated using the Engineering Equation Solver (EES) software, while the fast-pyrolysis process and the TCES were simulated using the Aspen Plus software. A thermodynamic and economic analysis has been conducted to estimate the share of solar energy for different process configurations. Economic calculations have been conducted for three different heliostat filed areas: 4000, 8000, and 12000 m2. Solar fraction, investment and operational costs, as well as total cost were calculated for these three heliostat field areas. The results indicate that the optimum heliostat field area for the studied biomass pyrolysis plant is 8000 m2 and the average solar fraction of the required energy in summer is 0.39 and while it is 0.34 for the whole year. Simulation results considering this optimized heliostat filed area indicate that 6.27 t/h of bio-oil is produced from 10 t/h of hybrid poplar biomass. Implementing this solar-assisted system reduces CO2 emissions, increases efficiency of the system and lowers thermal energy requirement for the fast-pyrolysis process from 6MW to 3.99MW.

Mechanism insight into α-D-galactopyranose conversion to 5-hydroxymethyl furfural by combining Py-GC–MS experiments and theoretical calculations

Pyrolysis of biomass is a promising technique for producing various chemicals. During the fast pyrolysis of biomass, 5-hydroxymethyl furfural (5-HMF) is a significant product derived from holocellulose, which consists of cellulose and hemicellulose. In this study, the formation mechanism of 5-HMF was systematically revealed by combining fast pyrolysis experiments of 13C-labeled and unlabeled D-galactose and density functional theory calculations that α-D-galactopyranose was selected as the model compound for hemicellulose. Experimental results show the yield and concentration of 5-HMF gradually decrease as the temperature rises (≥400 °C). In addition, the origin of the C atoms in 5-HMF was determined. The aldehyde group and hydroxymethyl are primarily derived from C1 and C6 of D-galactose, respectively. Based on computational results, α-D-galactopyranose prefers to undergo a ring-opening reaction to form acyclic D-galactose with an energy barrier of 166.5 kJ/mol. (2R,3S,E)-2,3,5,6-tetrahydroxyhex-4-enal (C1-i2) and (2R,3S)-2,3,6-trihydroxy-5-oxohexanal (C1-i3) generated by D-galactose are important intermediates for 5-HMF formation. Because C1-i3 can readily form 5-HMF through successive dehydration at 3-OH+2-H site, cyclization, and dehydration at 5-OH+4-H site. In favorable paths, the aldehyde group of 5-HMF all comes from C1 of α-D-galactopyranose, which reasonably explains the experimental results. Overall, this study will be helpful to improve the formation mechanism of 5-HMF and to develop relevant pyrolysis techniques to prepare it.

Intrinsic promotion mechanism of calcium oxide on ketone production during catalytic fast pyrolysis of biomass via experiment and density functional theory simulation

CaO modified with acetic acid solution or sodium hydroxide (H-CaO/OH-CaO) was used to explore the relationship between the physical and chemical properties of CaO and the components of bio-oil during the pyrolysis of rice straw (RS) and model compounds via experiment and density functional theory(DFT) simulation. The results showed that the modification changed the properties of CaO, and thus the catalytic performance on production of bio-oil components. H-CaO with the larger number of strong basic sites (1.10 ∼ 2 times than commercial CaO) and the longer Ca-O bond length showed the better selectivity and performance on formation of ketones (the maximum relative content in bio-oil reached 43 %). The conversion pathway of cellulose/hemicellulose was changed by H-CaO, which promoted the formation of ketones. The easier combining of H-CaO with the pyrolysis primary products due to the longer Ca-O bond was the key to its better performance.

Towards the production of 1,4:3,6-dianhydro-α-d-glucopyranose from biomass fast pyrolysis based on oxalic acid-assisted torrefaction pretreatment

Pyrolysis, a promising thermochemical conversion technique, can convert lignocellulosic biomass into various value-added products. Herein, the selective production of 1,4:3,6-dianhydro-α-d-glucopyranose (DGP) was achieved through fast pyrolysis of cellulose based on oxalic acid-assisted torrefaction (OAT) pretreatment. The mixture of cellulose and oxalic acid first underwent torrefaction, followed by fast pyrolysis to yield DGP. Simultaneously, the air atmosphere was considered to facilitate the formation of esterification intermediates, thereby promoting the formation of DGP. The effects of torrefaction temperature, oxalic acid amount, as well as pyrolysis temperature were carefully explored for DGP production. A yield of 9.6 wt% and a selectivity of 57.5 % for DGP were achieved from the micro-scale pyrolysis of cellulose under the optimized conditions. In lab-scale tests, the DGP yield reached 12.5 wt% from cellulose. The OAT-based pyrolysis was confirmed to be applicable to the waste cellulose-rich materials, with a DGP yield of 8.2 wt% from waste cotton and 6.0 wt% from spent paper in lab-scale experiments. Additionally, the OAT-based pyrolysis also showed the potential for poly-generation of DGP and formic acid at different stages.

Electrocatalytic Upgrading of Biomass-Derived Compounds for Biofuel Production

Biomass fast pyrolysis liquid (also known as bio-oil) is considered to be one of the most promising renewable carbon feedstocks. However, fresh pyrolyzed bio-oil is acidic and corrosive and contains large amounts of carbonyl and phenolic compounds produced by polymerization under acidic conditions. This work primarily utilizes an electrochemical conversion strategy using only earth-abundant metal catalysts to achieve the carbonyl hydrogenation process. The results show that upgrading this process produces biofuels with greater stability and higher specific energy. In addition to analyzing the chemical implications of this conversion strategy, this work will also discuss why electrocatalytic conversion is a promising technology path for biofuels and fine chemicals. Reference Huang, S., Lam, C. H.* et al. (2022). "The Structural Phase Effect of MoS2 in Controlling the Reaction Selectivity between Electrocatalytic Hydrogenation and Dimerization of Furfural." ACS Catalysis 12(18): 11340-11354.Huang, S., Lam, C. H.* et al. (2022). "MoS2-Catalyzed Selective Electrocatalytic Hydrogenation of Aromatic Aldehydes in an Aqueous Environment." Green Chemistry.Tu, Q., Lam, C. H.* et al. (2021). "Electrocatalysis for Chemical and Fuel Production: Investigating Climate Change Mitigation Potential and Economic Feasibility." Environmental Science & Technology 55(5): 3240-3249.Garedew, M., Lam, C. H.* et al. (2020). "Greener Routes to Biomass Waste Valorization: Lignin Transformation Through Electrocatalysis for Renewable Chemicals and Fuels Production." ChemSusChem 13(17): 4214-4237. Lam, C. H., et al. (2017). "Towards sustainable hydrocarbon fuels with biomass fast pyrolysis oil and electrocatalytic upgrading." Sustainable Energy & Fuels 1(2): 258-266. Figure 1

Energy Analysis and Heat Integration in the Joint Process of Biomass Fast Pyrolysis and In Line Sorption Enhanced Steam Reforming.

Biomass Fast Pyrolysis and in line Steam Reforming (PY-SR) is promising alternative for H2 production. However, there are potential strategies for intensifying the process, such as capturing the CO2 in situ in the reforming step, which is so-called Sorption Enhanced Steam Reforming (SESR). Both PY-SR and PY-SESR were simulated using a thermodynamic approach and empirical correlations, and they were compared based on the energy requirements, H2 production, and H2 purity at different temperatures (500-800 °C) and steam to biomass (S/B) ratios (0-4). Then, the energy requirements for the PY-SESR were analyzed in detail for a reforming temperature of 600 °C and several S/B ratios, and a heat integration scheme was proposed, aiming at making the process thermally autosustained. Although the energy requirement of PY-SESR is always higher than that of PY-SR at the same reforming conditions, it allows the use of milder operating conditions, with the process performance being even better. Thus, PY-SESR outshines PY-SR, as it allows obtaining a higher H2 production (0.124 kgH2 kg-1 biomass vs 0.118 kgH2 kg-1 biomass) and H2 purity (98 mol % vs 67 mol %), with a lower energy requirement, and capturing the CO2 generated, thereby attaining negative emissions. The main energy demands of this process account for water evaporation and sorbent calcination. Nevertheless, a thermally autosustained PY-SESR process may be attained by recovering heat from the product streams, transferring heat from the reforming reactor to the pyrolysis reactor, and burning the char generated in the pyrolysis step.

Catalytic Fast Pyrolysis of Biomass over Hierarchical Zeolites: Comparison of Mordenite, Beta, and ZSM-5

Catalytic Fast Pyrolysis of Biomass over Hierarchical Zeolites: Comparison of Mordenite, Beta, and ZSM-5

Selective production of high-value fuel via catalytic upgrading of bio-oil over nitrogen-doped carbon-alumina hybrid supported cobalt catalysts

Bio-oil derived from biomass fast pyrolysis can be upgraded to gasoline and diesel alternatives by catalytic hydrodeoxygenation (HDO). Here, the novel nitrogen-doped carbon–alumina hybrid supported cobalt (Co/NCAn, n = 1, 2.5, 5) catalyst is established by a coagulation bath technique. The optimized Co/NCA2.5 catalyst presented 100 % conversion of guaiacol, high selectivity to cyclohexane (93.6 %), and extremely high deoxygenation degree (97.3 %), respectively. Therein, the formation of cyclohexanol was facilitated by stronger binding energy and greater charge transfer between Co and NC which was unraveled by density functional theory calculations. In addition, the appropriate amount of Lewis acid sites enhanced the cleavage of the C–O bond in cyclohexanol, finally resulting in a remarkable selectivity for cyclohexane. Finally, the Co/NCA2.5 catalyst also exhibited excellent selectivity (93.1 %) for high heating value hydrocarbon fuel in crude bio-oil HDO. This work provides a theoretical basis on N dopants collaborating alumina hybrid catalysts for efficient HDO reaction.

Biomass fast pyrolysis kinetics using curie-point pyrolysis: Comparison with pyroprobe and thermogravimetric analysis

In this study, the kinetics of fast pyrolysis of pine wood biomass at short timescales is evaluated using analytical Curie-point and Pyroprobe® pyrolyzers. Curie-point pyrolysis was highly effective in ensuring that the biomass was heated to the set temperatures at very high heating rates and precise time scales. This is the first time the mass loss data of lignocellulosic biomass using a Curie-point pyrolyzer is being reported at short timescales of the order of 10−1 s. COMSOL Multiphysics® simulations, employed to determine the time required for the sample to heat-up to the final reaction temperature, proved that it was 0.2 s in the Curie-point pyrolyzer and 6–8 s in the Pyroprobe® reactor. Within a time period of 0.5 s for temperatures greater than 400 °C, complete conversion of the biomass was achieved using a Curie-point pyrolyzer. The conventional reaction kinetic models were not able to explain the pyrolysis behavior of the sample in a Curie-point pyrolyzer, especially at short timescales of 0–0.5 s. However, the kinetics until 0.4 s, corresponding to the release of light volatiles, is shown to follow the sigmoidal Avrami model, while the major devolatilization stage in the range of 0.4–0.5 s could not be described by a standard kinetic model. This showed that the reactions at short time scales are highly complex processes governed by the competing decomposition rates of the biomolecules. The isothermal mass loss experiments using the Pyroprobe® showed that pyrolysis followed first-order kinetics, and the rate of decomposition was slower as it took 10–20 s for the conversion to attain a steady value. The kinetic compensation for the pyrolysis of pinewood was constructed using the fast pyrolysis data and the kinetics of slow pyrolysis using isoconversional models, and it was found to be ln(A) = 0.18*Ea – 3.12.

Co-production of porous N-doped biochar and hydrogen-rich gas production from simultaneous pyrolysis-activation-nitrogen doping of biomass: Synergistic mechanism of KOH and NH3

In this study, a method of simultaneous activation and nitrogen doping during biomass fast pyrolysis for co-production of porous N-doped biochar and H2-rich gas production was proposed. The effect of temperature on chemical interaction mechanism of KOH and NH3 was investigated at 500–800 °C. Results showed that KOH and NH3 had a synergistic effect on pore development and nitrogen doping, and the specific surface area and nitrogen content reached maximum values of 2008.37 m2/g and 5.05 wt%, respectively. It may be due to that NH3 entered pores generating by KOH activation for further activation, and at the same time, excessive NH3 could convert new O-containing groups to N-containing groups for more effective nitrogen doping. What's more, the H2 concentration and yield were up to 56.67 vol% and 517.95 mL/g, respectively. It indicates that the synchronization method of fast pyrolysis-activation-nitrogen doping is a promising approach, which is of great significance for the high-value utilization of biomass.

Fast pyrolysis of biomass with diverse properties to produce liquid hydrogen storage molecules

Liquid organic hydrogen carriers (LOHCs), such as methanol and formic acid, offer a reliable solution for the challenges associated with transporting and storing gaseous hydrogen. However, the current industrial LOHCs are costly and in limited supply due to complex synthesis methods involving gasification and Fischer-Tropsch synthesis. An alternative approach utilizing efficient pyrolysis methods can convert biomass into substances that mimic LOHCs, making them a promising avenue for hydrogen storage. Compounds with a high hydrogen content, including glycolaldehyde, acetic acid, and acetol, hold potential as effective LOHCs. This study seeks to assess how the specific properties of biomass impact the resulting products and target molecules, focusing on identifying the primary sources of LOHC compounds. The experimental results indicate that glycolaldehyde primarily originates from cellulose, while acetic acid is mainly derived from hemicellulose. Acetol is produced from both cellulose and hemicellulose. At a pyrolysis temperature of 500 °C and a particle size of 0.38–0.83 mm, corn cob yields a higher quantity of glycolaldehyde, acetic acid, and acetol (107 mg/g) compared to rice husk (85.6 mg/g) and pine (68.9 mg/g) due to its significant cellulose and hemicellulose content. Notably, the primary sources of these hydrogen storage molecules during pyrolysis are the initial biomass pyrolysis products rather than secondary reactions.

Study on the flow characteristics of heterogeneous particles in three types of biomass fast pyrolysis down-tube reactors

A novel staircase down-tube reactor has been developed to solve the problem of the short residence time of ceramic balls in a vertical down-tube reactor and flow separation of biochar powder and ceramic balls in a V-shaped down-tube reactor. Numerical simulation was performed using a coupled approach that combined the Discrete Element Method (DEM) and Computational Fluid Dynamics (CFD) to simulate the mixing flow of heterogeneous particles (biochar powder and ceramic balls) in three types of down-tube reactors: staircase, vertical, and V-shaped structure. The results show that at an equivalent vertical height. The average residence time for ceramic ball in a staircase down-tube reactor is longer than that of the other two types (tstaircase structure = 1.6 s > tV-shaped structure = 1.0 s > tvertical structure = 0.6 s). The average residence time of biochar powder in three types of down-tube reactors can be classified as follows: tV-shaped structure = tstaircase structure = 1.2 s > tvertical structure = 1.1 s. The flow separation and centripetal motion of heterogeneous particles were observed in V-shaped down-tube reactor. A distinct periodic motion is exhibited in staircase down-tube reactor, it has great significance for exploring the flow and heat transfer regularity of heterogeneous particles. Eccentric distance (E.d) was proposed as a measure of the spatial utilization efficiency of the device. While the degree of coherence (D.c) was used to assess the degree of flow separation among heterogeneous particles.

Modeling hydrodynamic and biomass pyrolysis effects of recycled product gases in a bubbling fluidized bed reactor

Fast pyrolysis of biomass in a fluidized bed reactor is typically conducted in a nitrogen gas environment. Recycling product gas can improve the economics of operating such a system by reducing reliance on pure process streams, but much less is known about how recycling pyrolysis product gas may affect fluidization behavior and pyrolysis kinetics. Therefore, gas effects in a fluidized bed biomass pyrolysis reactor were investigated using engineering correlations, low-order models, and CFD simulations for N2, H2, CO, CO2, and CH4 carrier gas mixtures. Our findings reveal viscosity of a gas mixture can be significantly underestimated depending on the model and correlation. Furthermore, fluidization characteristics such as Umf and gas-solid convective heat transfer can be greatly affected by the gas properties. By utilizing H2 as the fluidizing gas (instead of N2), while maintaining a constant fluidization ratio (Us/Umf), the bio-oil yields can be increased ∼5%. This is due to the lower density H2 producing similar hydrodynamics as N2 at higher gas flow rates. These higher flow rates result in shorter gas residence times, and as a result, less secondary reactions that convert bio-oil to light gases and char. Model results also suggest that bio-oil yield is not significantly affected by the type of carrier gas used, with bio-oil yield varying by ∼2% across different gas mixtures while maintaining constant flow rate. This indicates that recycled pyrolytic gas can be used as the carrier gas for biomass pyrolysis.

Mathematical Modeling of Multi-Phenomena Anisotropic Systems: Ejection of Primary Aerosols during the Fast Pyrolysis of Biomass

This study introduces a novel particle model for biomass fast pyrolysis, incorporating an anisotropic cylindrical particle to address mass and energy transport coupled with aerosol ejection, which previous models have overlooked. The main contribution lies in developing a model that considers aerosol generation in anisotropic cylindrical particles for the first time, addressing bubbling dynamics and bursting within the liquid phase. The population balance equation describes bubble dynamics and aerosol formation, capturing phenomena like nucleation, growth, coalescence, and bursting. The model employs the method of moments with bubble volume as an internal variable, substantially reducing computational costs by eliminating dependence on this variable. Results highlight the significant impact of anisotropy and particle size on aerosol ejection: smaller, less elongated particles experience faster heating, quicker conversion, and the increased accumulation of the liquid intermediate phase. Specifically, 1 mm diameter particles yield higher concentrations of metaplast and bio-oil aerosols, exceeding 15%, compared to concentrations below 11% for 3 mm particles. This model provides insights into aerosol structure (volume, surface area), aiding in understanding aerosol reactivity at the reactor scale.

Coupling coarse‐grained DEM‐CFD and intraparticle model for biomass fast pyrolysis simulation and experiment validation

AbstractThe understanding of complex fluidization hydrodynamics and chemical reactions in biomass fast pyrolysis fluidized bed reactors is lacking and requires further investigation. It is urgent to develop accurate mathematical models capable of describing the complex multiphase reaction system of biomass pyrolysis. A comprehensive multiscale model based on coarse‐grained discrete element method (DEM)‐computational fluid dynamics (CFD) was developed in open‐source MFiX code. It incorporates detailed biomass pyrolysis kinetics and an intraparticle model. To validate the model, measurements were conducted in a fluidized bed pyrolyzer, including quantifying the segmental pressure drop along the height of the bed and determining the yields and compositions of gas, liquid, and solid products. The particle mixing and segregation, axial distribution and residence time, Lacey index, and pyrolysis products were investigated. The study provides experimental and theoretical foundations for designing multiphase fluidized bed reactors and advancing biomass thermochemical conversion.

Physical modelling and hydrodynamic characterization of an internally circulating fluidized bed for biomass fast pyrolysis

This study investigates the hydrodynamics of the cold flow model (CFM) of an internally circulating fluidized bed (ICFB) finalized to biomass fast pyrolysis. The ICFB, basically consisting of a bubbling fluidized bed interconnected with a moving bed, is designed aiming at high fuel particles heating rates, efficient solids mixing and low gas residence times. Experimental techniques such as basket collection, solids and gas tracing are adopted to determine solids circulation rates, gas bypassing and particles residence times, consequently a compartment model of the CFM is proposed. The influence of operating conditions such as bed inventory and superficial gas velocity is investigated together with the effect of the opening ratio between the two interconnected beds. Results highlight that different operation regimes can occur and an optimization of operating and design parameters allows high solids circulation rates, low gas bypass and residence times lower than 1 s, as pursued in fast pyrolysis.

Hybrid Biomass Fast Pyrolysis Process and Solar Thermochemical Energy Storage System, Investigation and Process Development

Hybrid Biomass Fast Pyrolysis Process and Solar Thermochemical Energy Storage System, Investigation and Process Development

A deep-learning model for predicting spatiotemporal evolution in reactive fluidized bed reactor

Detailed information of flow fields is of great significance for designing and optimizing multiphase flow systems. However, predicting spatiotemporal evolution of gas-solid flows using numerical simulation often requires a significant amount of computation and time. In this study, we proposed a 3D convolutional neural network for predicting reactive dense gas-solid flows. We first explored the design of model architecture and extensively evaluated the performance in terms of efficiency, accuracy, long-term prediction stability and generalizability for a non-reactive fluidized bed. Then we extended the method to a biomass fast pyrolysis process. The proposed model achieves real-time prediction, 3–4 orders of magnitude faster than CFD-DEM simulations. The surrogate model reasonably captures bubble-driven flow behaviors and effects of bubble on fast pyrolysis reactions. The predicted bubble characteristics, and time-averaged and RMS flow fields match well with the simulation results. Our approach exhibits excellent long-term stability and has good generalization capability to unseen fluidization velocities. To the best of our knowledge, this is the first time a neural network has been successfully applied to learn spatiotemporal evolution of reactive dense gas-solid flows.

Deconstructing biomass resistance for improving pyrolytic sugars via γ-valerolactone pretreated bamboo coupled with fast pyrolysis

Pyrolytic sugars, as significant fermentable sugars for the production of fuel ethanol, can be fleetly prepared by biomass fast pyrolysis. However, both the biomass inherent resistance and the interaction of compositions restrain the formation of pyrolytic sugars during pyrolysis. To overcome the above bottleneck and improve the yield of pyrolytic sugars, γ-valerolactone (GVL) pretreatment of bamboo coupled with fast pyrolysis was proposed. The effects of reaction temperatures, concentration of acid catalyst, pyrolytic parameters and kinetics on the distributions of sugar compounds were systematically investigated in this process. The experimental results demonstrated that the GVL pretreated biomass effectively eliminated the inherent resistance due to the removal of lignin (16.5 wt%) and hemicellulose (16 wt%). In addition, the content of alkaline and alkaline earth metals significantly decreased from 0.25 wt% of untreated bamboo to 0.01 wt% of the pretreated sample. Subsequently, the selectivity of levoglucosan effectively raised from 9.1 % of untreated bamboo to 70.3 % of GVL pretreated bamboo, and the content of levoglucosan from fast pyrolysis of GVL pretreated bamboo increased 20.2 folds as compared to untreated bamboo.