Pyrolysis Of Cellulose Research Articles

Influence of the chemical activation with KOH/KNO3 on the CO2 adsorption capacity of activated carbons from pyrolysis of cellulose

Plant biomass is an attractive precursor to prepare activated carbons with high surface area for CO2 adsorption due to its low-cost and easy regeneration. Despite this interest, there are still remaining questions regarding the optimal processing conditions and the choice of activating agent. Moreover, since plant biomass shows a highly variable proportion of different biopolymers (cellulose, hemicellulose, lignin), it is important to understand the activation effect on each constituent. In this work, carbons obtained from pyrolysis of cellulose were activated using two potassium salts, using two different activation temperatures. The samples were characterized to elucidate the influence of the activation conditions on their CO2 adsorption capacity. In general, all the carbons activated at higher temperature showed higher adsorption capacity. These results are comparable with other carbons derived from biomass described in the bibliography. Among the activated carbons studied, the carbon activated only with KOH exhibits the highest CO2 adsorption capacity at 1 bar meanwhile the highest adsorption capacity at saturation pressure belongs to the carbon activated with larger ratio of KNO3.

Synthesis and properties of graphene-like porous carbon from modified cellulose

The work is devoted to the synthesis of graphene-like magnetic nanocomposites by direct pyrolysis of hemp microcrystalline cellulose modified with citric acid containing nickel or cobalt salts. Their chemical structure and morphology were characterized by X-ray diffraction (XRD), electron microscopy (SEM), Raman spectroscopy, low-temperature N2 adsorption-desorption, and Fourier transform infrared spectroscopy (FT-IR). Thermogravimetry has established a possible mechanism of pyrolysis of a modified cellulose matrix containing Ni and Co metals. X-ray diffraction analysis and Raman spectroscopy have shown that an increase in the number of carboxyl groups accelerates the process of graphitization of the cellulose matrix with transition metals (Ni and Co), as well as increases the degree of structural order and the level of graphitization. The conducted studies have shown that nanoparticles of metals of the zero-valence state are enclosed in graphene-like shells having a mainly mesoporous structure.

Cellulose pyrolysis via liquid metal catalysis

Liquid metals are largely unexplored as catalytic media for biomass conversion. Unlike conventional solid-state catalysts which are prone to deactivation, liquid metals, i.e., low-melting metals operated above their melting point, can show resilience against coking, high thermal conductivity, and enhanced liquid-solid contact between catalyst and biomass feedstocks. This promise motivated the present investigation of liquid metals as catalysts for cellulose pyrolysis. Bismuth, tin, and indium were selected as liquid metal candidates, and their impact on cellulose devolatilization kinetics is studied via thermogravimetric analysis. The results indicate that all three metals show catalytic activity, with bismuth catalyzing volatiles formation, while indium and tin enhance char formation. Quantitative analysis of liquid product reveals that bismuth is selective to dehydration and functional rearrangement reactions, leading to anhydro sugars and functionalized furans formation. In contrast, indium and tin are selective towards dehydration, fragmentation reactions, and Diels Alder chemistry, leading to formation of C2-C4 fragments and aromatic compounds, as further confirmed via infrared spectroscopic analysis of the obtained chars. Finally, the Sn and Bi liquid metals’ stability against deactivation via coking is examined against conventional solid-state zeolite catalyst through multiple cellulose pyrolysis runs in the thermogravimetric analyzer (TGA) with the same batch of catalyst. While ZSM-5 zeolite catalyst's activity and selectivity declined and approached non-catalytic sand results (both the TGA curve and the liquid product distribution) within the first few runs, both Sn and Bi fairly maintained their robustness against coking for the conducted durability runs. Overall, the results show significant promise for this new class of catalysts for biomass pyrolysis.

Effective catalytic conversion of cellulose pyrolysis into D-Allose via Al1-Fe5 nano-catalysts

This research has made significant advancements in the field of high-value bio-oil production, specifically focusing on the synthesis of the rare sugar D-Allose. Notably, synthesizing D-Allose through cellulose pyrolysis has long been challenging due to its high synthetic difficulty, which has limited related studies. By employing a one-pot synthesis approach using Alx-Fey nano-catalysts prepared through a unique cellulose pretreatment method, this experiment successfully achieved efficient generation of D-Allose during rapid pyrolysis. Systematic experimentation demonstrated that at 330 °C with the Al1-Fe5 nano-catalyst, the yield of D-Allose from cellulose pyrolysis reached an impressive 50.69 %, accompanied by a detection of 14.35 % furfural in the bio-oil. This breakthrough not only significantly contributes to the high-value utilization of bio-oil but also provides robust support for further development in this area. Simultaneously, the success of this research extends beyond high-value bio-oil utilization and makes a substantial impact on both the scientific community and industry.

Improving the yield of levoglucosan platform chemical from the pyrolysis of date pits waste biomass through pre-treatments

Lignocellulosic biomass, as the primary carbon source, serves as the foundation for the entire biorefinery concept. In this regard, date pits constitute an important category of biomass waste in many parts of the world. Levoglucosan, also known as 1,6-anhydro-β-d-glucopyranose (LG), is a significant sugar derivative and a platform chemical produced as a primary product in the cellulose pyrolysis process. Aiming to further improve the yield of levoglucosan from pyrolysis of date pits, pre-treatment methods were carried out via washing crushed date pits with different concentrations of selected acids (sulfuric acid: 1 M/3 M, nitric acid:1 M/3 M), and with hot water. The chemical and elemental compositions of the five considered samples were thoroughly analyzed and characterized by a wide array of ultimate and proximate techniques such as Neutral Detergent Fiber (NDF %), ASH content and organic Matter (%), and Mineral Nutrients Profile (ppm). By utilizing Py-GC/MS system, the product distribution from pyrolysis of raw and treated date pits was obtained at a range of temperatures between 300 and 500 °C. Compared to the raw date pits, pyrolysis of treated date pits pre-treated by 1 M H2SO4 acid exhibited a dramatic increase in the concentration of levoglucosan due to the profound removal of the various categories of minerals in date pits and an increase in the NDF %. A positive correlation prevails between the removal efficiency of alkali/alkaline earth metals (AAEMs) and the yield of LG. The former catalyzes ring-opening reaction that results in the destruction of sugar derivatives. On the other hand, pre-treatment with water also increases the yield of LG compared to raw date pits, but to a lesser extent. Outcomes demonstrated herein convey a practical method to enhance the production of commodity chemicals from waste biomass.

Volatile-char interactions during biomass pyrolysis: Effects of functionalized graphitized carbon nanotubes on volatile distribution of cellulose and its model compounds

Volatile-char interactions are prevalent in biomass pyrolysis processes. To gain deeper insights into their impact on biomass pyrolysis volatile distribution, interactions between volatile compounds and char during flash pyrolysis of glucose, cellobiose, and cellulose were investigated using a pyrolysis–gas chromatography/mass spectrometry detection technique, by modifying both the chain lengths of the raw materials and the functional groups of graphitized multi-walled carbon nanotubes (CNTs). The results reveal that volatile-char interactions markedly influence the distribution of the final pyrolysis products derived from glucose-based compounds. In the presence of any type of CNTs, dehydrated saccharides in the primary products, particularly levoglucosan (LG), exhibit the highest sensitivity to the interactions. Consequently, primary products such as LG and 5-hydroxymethylfurfural (HMF) undergo secondary pyrolysis, yielding compounds such as levoglucosenone (LGO) and 5-methyl-2-furancarboxaldehyde (FCM). Additionally, CNTs without functional groups are advantageous for the production of expensive LGO (The relative abundance reached 9.65%), whereas the relative abundance of FCM increases significantly with hydroxyl-, carboxyl-, and amino-modified carbon nanotubes. Particularly, the relative abundance of FCM is highest in the presence of amino-modified carbon nanotubes, regardless of whether the feedstock is glucose, cellobiose, or cellulose, with values of 25.14%, 23.32%, and 4.23%, respectively. Furthermore, consistent changes in product distribution trends among different glucose-based compounds under identical CNT conditions suggest that glycosidic bonds have minimal impact on volatile-char interactions.

Experimental and numerical investigation on the combustion behavior of densified wood: Differences among wood species and impact of char oxidation

Densified wood (DW) is a novel structural material with promissing application potential in construction industry due to its excellent mechanical performance. However, it could also be a disastrous fuel contributing to the development of fires. This work experimentally and numerically investigated the combustion behavior of DW. The differences among wood species (fir, pine and oak) and their char oxidation impacts are emphasized. The experimental results indicate that DW has a 44.7 K lower pyrolysis peak temperature on average, a 32.2 % lower peak mass loss rate, and a 8 % higher residual mass ratio than natural wood (NW) in N2 due to the delignification process. The hemicellulose and cellulose pyrolysis are endothermic in N2 but exothermic in air. Wood pyrolysis has an additional char oxidation reaction in air. The higher density of DW leads to longer times for ignition and flaming combustion. DW presents a higher heat release rate and average 4.7 MJ kg−1 higher effective heat of combustion of char. Two parallel pyrolysis reaction schemes based on ambiance are proposed, which well-predict the microscale characterizations but fail to represent the combustion behavior. An optimized mode was developed by adding a continuous char oxidation reaction to the N2 reaction scheme, which best predicts the combustion behaviors.

Low temperature carbonization and synergistic flame retardancy of cotton fabric coated by phosphorus‑nitrogen flame retardants

To solve the problems of flammability and smoldering of cotton fabric, its flame-retardant finishing was executed with biomass wool keratin (WK) and cyclic phosphate ester (CPE) through the soaking and baking process. The synergistic mechanism of WK low-temperature melting and CPE catalytic dehydration prompted the formation of protective carbonization layer on cotton fabric surface, and this protective layer reduced its pyrolysis rate, inhibited the production of combustible materials and improved its flame retardancy. The results of synchronous thermal analysis indicate that the initial decomposition temperature of WK and CPE is lower than that of cotton fabric, and they precede the endothermic degradation before fabric main body. This effectively promotes the low-temperature carbonization of cotton fabric and inhibits its pyrolysis. The initial decomposition temperature of WK/CPE treated fabrics advances by 47.9 °C–97.8 °C, presenting significant low-temperature carbonization trend. Moreover, they form 3.0 %–20.0 % aromatic structural char before the pyrolysis of cotton cellulose due to the low-temperature dehydration and carbonization reactions. The damage length after vertical burning is only 4.0 cm for treated fabric with five layers, its after-flame and smoldering disappear, and its limiting oxygen index value increases to 28.7 %. This research provides an effective idea for the flammability and smoldering problems of cotton fabric.

Rapid pyrolysis of cellulose: Revealing the role of volatile matter and char structure evolution

The complexity of the cellulose structure hinders its energy conversion and utilization. Pyrolysis is not only an independent thermochemical conversion technology but also a necessary stage in the gasification process. The real-time capture of volatile components in cellulose pyrolysis is difficult, and the evolution of char structures is lacking, which is extremely challenging. In this work, elemental analysis, industrial analysis, thermogravimetric analysis, infrared spectroscopy (FTIR), Raman spectroscopy (Raman), and X-ray diffraction spectroscopy (XRD) were used to characterize the raw materials and products. Combined with rapid pyrolysis experiments, the pathways of cellulose pyrolysis volatiles and char structure evolution were explored. Dehydrated sugars are the initial products formed below 350 ℃, which quickly dehydrate to form furan compounds at 400 ℃ and then break CC bonds at 600 ℃ to generate fatty aldehydes, ketones, and carboxylic acids. Biochar generated at low temperatures (<300°C) has strong lipid solubility. An increase in pyrolysis temperature leads to a continuous decrease in the content of H and O in biochar, which destroys its functional groups and physical structure, and ultimately tends to form graphite-type char with aromatic structures. Based on the correlation between the volatile matter release characteristics and the evolution of the semichar structure, a cellulose pyrolysis pathway was established, providing theoretical support for the high-value utilization of cellulose.

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.

Enhanced selectivity in the production of furans/olefins through ex-situ catalytic pyrolysis over metal-modified TS-1

Catalytic pyrolysis technology is one of the most environmental and efficient approach in converting biomass waste into high-value chemicals and fuels. In this study, the ex-situ catalytic pyrolysis of cellulose to produce furans and olefins was reported using various metal-loaded TS-1 as catalysts. The experimental results showed that the Au/TS-1 exhibited an exceptional catalytic activity in the production of furans and olefins, achieving a selectivity of 49.17 % and 40.65 %, respectively. Ni/TS-1 effectively promoted the formation of ethylene, yielding a selectivity of 97.49 % and a yield of 6.11 C-mol%. Under the optimized conditions: pyrolysis temperature of 550 ℃, catalytic temperature of 600 ℃, and catalyst to cellulose mass ratio of 20:1, the Au/TS-1 catalyst achieved a furans selectivity of 41.91 % with a yield of 11.94 C-mol%, while olefins selectivity and yield were 49.84 % and 18.99 C-mol%, respectively. At this condition, Au/TS-1 still has excellent catalytic activity after 10 cycles and has good catalytic effect towards different biomass feedstocks. Furthermore, the possible mechanism to produce furans and olefins was revealed. This research offers valuable insights for guiding the directed conversion of biomass into value-added chemicals, paving the way for a more sustainable future.

Regulating phenol tar in pyrolysis of lignocellulosic biomass: Product characteristics and conversion mechanisms

The utilization of biomass pyrolysis is a crucial approach for sustainable development. This study used the typical biomass of pine (PI), rice husk (RH), and corn straw (ST) as feedstocks to evaluate the pyrolysis mechanisms, features and conversion mechanisms of the phenol tar product. The phenolic gaseous products were more trailing in ST, which mostly concentrated around 320–500 °C. Primary phenol tar is produced from lignin through the homolytic cleavage of β-O and α-O, and C-C bond breakage, primarily occurring before 550 °C. As the degree of aromatization increases, the oxygenates progressively deoxygenate, and the primary tar demethoxylates to form secondary tar as the temperature increases. The pyrolysis of cellulose produces H radicals, which aid the transformation of lignin into phenol tar. This study can provide a theoretical basis for biomass pyrolysis to select the appropriate process parameters to improve the quality of bio-oil and regulate phenol tar products.

Unravelling the complexity of hemicellulose pyrolysis: Quantitative and detailed product speciation for xylan and glucomannan in TGA and fixed bed reactor

For the first time, the complete characterization of the pyrolysis of key biomass components – xylan (representative of pentose-based hardwood hemicellulose) and glucomannan (representative of hexose-based softwood hemicellulose) – is herein obtained by applying a novel methodology based on TGA (thermogravimetric analysis), previously developed for cellulose. Data on devolatilization rates, onset temperatures and detailed quantification of the mass yield of ∼ 50 products in the gas, liquid, solid phase were achieved simultaneously, with closure of mass balance, thus providing unique kinetic information. Pyrolysis tests were also carried out in a fixed bed reactor to explore larger scales and validate the TGA-based approach. At both scales, combinations of different analytical techniques (online MS, offline GC-FID/MS, Karl Fischer titration) and sampling protocols (cold condenser, sorbent traps, vapour syringes, gas bags) were tuned to achieve closure of mass balances and rigorous product speciation.While the pyrolysis of cellulose – chosen as reference system − maximized the bio-oil production (mostly levoglucosan), the pyrolysis of xylan resulted into an even distribution among solid, liquid and gas phases, with condensable oxygenates spanning homogeneously in the C1-C9 range. Interestingly, glucomannan showed an intermediate behaviour between cellulose and xylan, mirroring its intermediate chemical structure. Raman and oxidation analyses on the collected char samples showed that the solid residuals from hemicelluloses were less ordered and richer in ashes than those from cellulose.The predictions of recent lumped kinetic models were used to benchmark the new datasets against the prior art on hemicellulose pyrolysis; the richness and comprehensiveness of the new information clearly emerge and pave the pathway to the de-bottlenecking of kinetic modelling.

Kinetic, gas emission, reaction pathway and interaction mechanism analysis during oxidative pyrolysis of aluminium electrolysis waste with beech wood

The oxidative pyrolysis kinetic, gas emission, reaction pathway and interaction mechanism during oxidative pyrolysis of spent cathode carbon block (SCCB) and beech wood (BW) were investigated via the thermogravimetry combined with Fourier transform infrared spectrometer (TG-FTIR) analysis. The hemicellulose, cellulose, and lignin in BW and the carbon materials and fluoride in SCCB were determined as the main five components based on thermogravimetric experiment. Compared with pure SCCB, the addition of BW increased the comprehensive oxidative pyrolysis index. Furthermore, the total of 44 kinetic parameters were obtained by the Shuffled Complex Evolution (SCE) method, which were used to further forecast the mass loss of the above five main components. The evolved gases were detected by FTIR, and the results indicated that the main gases for BW/SCCB oxidative pyrolysis were CO2, which corresponded to the oxidation of cellulose, lignin and carbon materials. Small amounts of phenols, alcohols, ethers, ketones, aldehydes, carboxylic acids, CO, aromatics, alkene were attributed to the thermal decomposition of hemicellulose and cellulose. Pyrolysis of cellulose and lignin produced small quantities of hydrocarbons. HF was formed by the thermal decomposition of fluoride. Eventually, the reaction pathway was proposed and the possible interaction mechanism was analyzed during the oxidative pyrolysis of BW/SCCB blends.

Evolution of the Pd0/PdO phase change on Pd-MCM-41 catalyst for efficient production of furfural from the fast pyrolysis of cellulose

Furfural (C5H4O2) is a high-value platform chemical that is traditionally derived from the solvolysis of hemicellulose. However, its production from pyrolysis is far from satisfactory. In particular, the abundant cellulose within lignocellulosic biomass has yet to be successfully upgraded into furfural. Consequently, the overall yield of furfural from a lignocellulosic biomass is extremely low. Herein, we report a facile heterogeneous catalyst prepared from a simple impregnation of palladium (Pd) onto MCM-41 mesoporous silica. The catalyst demonstrated a remarkably high selectivity of ∼58.5% and yield of ∼32.5 wt% for furfural from the fast pyrolysis of wet cellulose. It was also confirmed to reach a selectivity of 65.4% and yield of 44.5 wt% for furfural from wet xylan, as well as a furfural yield of 23.9 wt% from wet sugarcane bagasse. All these values are superior to the literature reports. Through advanced characterisation including in-situ synchrotron high-temperature XRD and DRIFTS measurement, the loading of Pd in a tiny quantity of 1 mol% was confirmed to be sufficient in enhancing the surface hydrophilicity of the MCM-41 support, promoting the adsorption of reactants especially the formaldehyde group (HCHO), as well as the desorption of the target product furfural. In addition, Pd oxide (i.e., Pd2+O) was confirmed to be the catalytic active site. However, it was partly reduced into metallic Pd0 during the cellulose pyrolysis, due to the preferred reduction by adsorbed formaldehyde group and other reductants including H2 and CO in the vicinity of the PdO sites on the Pd-O-Si interface. Nevertheless, the catalyst was proven to retain the memory of its initial state after combustive regeneration in air, having oxidation state of Pd, particle size, and dispersion degree being reversed to its original construction. Accordingly, its activity remained stable upon cyclic testing. All these results demonstrate a high practical viability of this heterogenous catalyst for the valorisation of cellulose-rich biomass, an otherwise abundant crop waste across the world.

Insight into catalytic effects of alkali metal salts addition on bamboo and cellulose pyrolysis

Alkali metal compounds have vital influence on biomass pyrolysis conversion. In this study, cellulose, and bamboo catalytic pyrolysis with different alkali metal salts catalysts (KCl, K2SO4, K2CO3, NaCl, Na2SO4, and Na2CO3) were investigated in the fixed-bed reaction system. The effects of cations (K+ and Na+) and anions (Cl-, SO42−, and CO32-) on the evolution properties of biochar, bio-oil, and gas products were explored under both in-situ and ex-situ catalytic pyrolysis. Results showed that alkali metal salts facilitated the yields of biochar and gases at the expense of that of bio-oil. Alkali metal chloride and sulfate showed a weaker catalytic effect, while alkali metal carbonate greatly promoted the generation of gas products and increased the condensation degree of biochar. With the addition of K2CO3 and Na2CO3, cyclopentanones content was over 50% from cellulose catalytic pyrolysis, and phenols content (mainly alkylphenols) reached over 80% from bamboo catalytic pyrolysis. Moreover, solid-solid catalytic reactions with K2CO3 and Na2CO3 catalysts had an important role in strikingly promoting conversion of pyrolysis products, and the solid-solid and gas-solid catalytic reactions with alkali metal carbonate catalysts were stronger than those with alkali metal chloride and sulfate catalysts. Furthermore, the possible catalytic pyrolysis mechanism of alkali metal salts on biomass pyrolysis was proposed, which is important to the high-value utilization of biomass.

Char formation during pyrolysis of torrefied cellulose: Role of potassium catalysis and torrefaction pretreatment

Torrefaction is an efficient pretreatment technology for large-scale and high-value utilization of biomass fuel. This study aims to enhance the understanding of the thermochemical conversion of torrefied biomass by delineating the role of potassium and torrefaction on primary/secondary charring reactions during pyrolysis of torrefied cellulose. Celluloses with varying potassium loading levels were torrefied at temperatures ranging from 200 to 320 °C and subsequently pyrolyzed at 1000 °C. Two contrasting pyrolysis conditions, i.e., limiting and enhancing transport resistance, were employed to tune the occurrence of secondary reactions, thereby determining the role of torrefaction and potassium on primary and secondary charring reactions. Potassium content, torrefaction severity, and pyrolysis conditions both profoundly affects char formation during pyrolysis of torrefied cellulose, resulting in a wide range of pyrolysis char yields from 1.95 wt% to 64.35 wt%. The structural changes induced by torrefaction, including the depolymerization of the carbohydrate structure and the formation of crosslinking structures, promote the char formation. Potassium enhances the char formation of torrefied cellulose in two ways: i) by catalyzing the transformation of the carbohydrate structure into the crosslinking structure during torrefaction, and ii) by catalyzing the charring reactions of both the carbohydrate and the crosslinking structures during pyrolysis. Raman spectral analysis of the char carbon structure indicates that increased potassium loading level and torrefaction severity enlarge the aromatic system of the char. The findings highlight the potential of optimizing biomass pyrolysis through controlled torrefaction and potassium, paving the way for more efficient biofuel production and high-quality biochar applications.

Effects of stepwise nitrogen-enriched pyrolysis strategies on nitrogenous compounds enrichment in cellulose pyrolysis bio-oils and nitrogen migration pathways

Nitrogen-enriched pyrolysis strategies can effectively convert biomass into nitrogenous chemicals. However, the bio-oil fractions obtained from conventional one-step pyrolysis (OSP) are still complex, limiting their further upgrading and refining. Therefore, a stepwise nitrogen-enriched pyrolysis strategy was proposed in this study. The aim was to investigate the role of the stepwise process in regulating the enrichment of bio-oil fractions and the evolution of nitrogen forms in biochar obtained from nitrogen-rich pyrolysis of cellulose. The results indicated that selecting lower pyrolysis temperatures (T1 = 250 °C, 300 °C) in the first step (S1) of the stepwise nitrogen-enriched pyrolysis could effectively convert the furans and carbonyls such as esters derived from the cellulose into nitrogenous compounds. Thereby, the relative enrichment of nitrogen-containing compounds was achieved. Of these, O300–S1 was enriched with 84.13% nitrogenous compounds (mainly pyrroles and pyrazines). Elemental and XPS analyses revealed that stepwise pyrolysis was more favorable for N enrichment in biochar, and that stepwise pyrolysis at 300 °C was favorable for nitrogen atoms to dope in the carbon lattice. Finally, the possible migration pathways of NH3–N during pyrolysis were proposed. This study presents new insights into the high-value utilization of nitrogenous compounds obtained from lignocellulosic biomass.

Evolution of heavy components in bio-oil during oxidative pyrolysis of cellulose, hemicellulose, and lignin

Biomass oxidative pyrolysis introduces restricted oxygen into the reaction zone, realizing autothermal pyrolysis to address the heat supply challenges inherent in large-scale applications. However, heavy components (＞200 Da) in bio-oil are critical precursors that lead to coke formation upon heating, which hinders the utilization of bio-oil. In this study, the conventional and oxidative pyrolysis experiments of cellulose, hemicellulose, and lignin in a fix-bed reactor were conducted at temperatures ranging from 300 °C to 800 °C, aiming to investigate the evolution of heavy components in bio-oil during biomass oxidative pyrolysis. The results showed that the addition of oxygen promoted the generation of bio-oil. Compared to conventional pyrolysis, the addition of oxygen mostly increased the yields of cellulose-oil, hemicellulose-oil, and lignin-oil by 28.21 %, 10.94 %, and 16.84 %, respectively. Further comprehensive analysis revealed that oxygen promoted the depolymerization of three components at a lower temperature range (＜ 500 °C). With increasing temperatures, oxygen enhanced the polymerization of volatiles from cellulose and lignin, where oxygen, acting as a binder, promoted the generation of phenolic compounds of heavy components in lignin-oil. Conversely, as the temperature increased, oxygen enhanced the oxidative decomposition of volatiles from hemicellulose, inhibiting the generation of heavy components in hemicellulose-oil. To sum up, this study presented a global evolution route of heavy components in bio-oil during oxidative pyrolysis of three components.

Thermogravimetric analysis on two Bambusa texlitis wastes slow pyrolysis behaviors and kinetics using isoconversional and parallel-reactions models

In this work, the pyrolysis behaviors and kinetics of two bamboo (Bambusa texlitis) wastes were investigated via thermogravimetric analysis. The weight loss behaviors of pyrolysis were studied by curvature of the conversion (α) curves. The curvature of α can depict the characteristic temperatures of pseudo component (hemicellulose, cellulose and lignin) pyrolysis. Model-free model was applied to estimate the apparent activation energies of the pure components for comparison with other kinetic models. Three parallel reaction (TPR) and parallel finite number first-order reaction (FNFOR) models were used for kinetic studies. The first-order TPR model underestimates the apparent activation energies of pseudo components. The nth-order TPR model underestimates the apparent activation energy of lignin and obtains characteristic temperatures that are inconsistent with those of pure lignin. The parallel FNFOR model is more reliable for simulating the kinetics of lignocellulosic biomass pyrolysis. The apparent activation energies of pseudo components depend on the variety of lignocellulosic biomass.