Non-condensable Gas Production Research Articles

Pyrolysis of high-density polyethylene: Degradation behaviors, kinetics, and product characteristics

Pyrolysis is a promising technology for converting plastic waste into valuable raw materials while offering a potential solution to the global plastic pollution crisis. In this study, the thermal pyrolysis of high-density polyethylene (HDPE) is investigated in a drop tube reactor under nearly isothermal conditions. The impact of reaction temperature and gas/volatile residence time on carbon conversion and product distribution is examined across a range of 500–900 °C and 3.6–32.2 s, respectively. Non-condensable gas products detected by online mass spectrometry are H2, CH4, C2H4, C2H6, C3H6, and C3H8. At elevated temperatures and prolonged residence time, H2 yield reaches as high as 8.6 wt% of the initial HDPE mass due to intensified cracking reactions of C2–C3 hydrocarbons and long-chain aliphatic compounds. Consequently, pyrolysis tars consist mainly of polycyclic aromatic hydrocarbons (PAHs) with 5–7 rings, accompanied by visible coke deposition within the reactor. HDPE decomposition to volatiles is an endothermic process and it is complete at a temperature between 492 °C and 525 °C, depending on the heating rate employed, from non-isothermal thermogravimetric analysis and differential scanning calorimetry (TGA-DSC) measurements. The thermal degradation of HDPE pellets follows the two-dimensional nucleation growth model for conversion levels up to 0.8 with an apparent activation energy of 259–270 kJ/mol and a pre-exponential factor of 4.83 × 1017–1.37 × 1019 min−1, determined from various isoconversional methods such as Flynn-Wall-Ozawa (FWO), Kissinger-Akahira-Sunose (KAS), and Starink, along with Criado's master plots. These findings provide valuable insights into optimizing process parameters and refining reactor design for pyrolysis, which can be integrated with gasification and reforming processes to enhance hydrogen production on a larger scale.

Valorization of hazardous plastic wastes into value-added resources by catalytic pyrolysis-gasification: A review of techno-economic analysis

Plastic waste pollution has grown exponentially since the 1950s. This situation was exacerbated when the volume of personal protective equipment (PPE)-based plastic waste surged after the COVID-19 pandemic. Plastic waste management such as landfills and incineration have adverse effects on the environment and human health due to the leaching of hazardous chemicals and the emission of toxic gases. Modern solutions such as biodegradable plastics and green brick technology are expensive and not well developed to valorize the current accumulation of plastic waste. This has led to the emergence of thermal degradation processes, which is faster and more realistic to solve the PPE-based plastic waste buildup. Pyrolysis and gasification systems to valorize plastic waste into hydrocarbons and fuels are discussed and compared with examples respectively. Scoping review approach is employed to conduct this study. To further increase the value of the final product of plastic waste management, the integrated pyrolysis system to upcycle plastic waste to carbon nanomaterials (CNMs) and the factors affecting the production of non-condensable gases are critically reviewed. The importance of feedstock composition, catalyst type, pyrolysis operating condition (including gas condition and temperature profiles) based on various studies is discussed. The potential and limitation of an integrated pyrolysis system are assessed from kinetic analysis, economic analysis and life-cycle assessment. This review is expected to contribute to the industrial-scale development of sustainable upcycling of plastic waste and enhance the production of desirable gas components for CNM synthesis for environmental sustainability.

Wood Vinegars: Production Processes, Properties, and Valorization

Abstract Pyrolysis of lignocellulosic biomass is widely used for the production of charcoal, pyroligneous liquid, and noncondensable gases. All three are value-added products that are exploited in several fields. However, this review focuses on three main areas: wood vinegar production methods, its physicochemical properties, and the use of wood vinegar or pyroligneous acid in agriculture and the environment. Wood vinegar is a liquid derived from wood by the condensation of gases and vapors released during the carbonization process, which is the transformation of wood into charcoal. It is mainly composed of aliphatic, aromatic, and naphthenic hydrocarbons and other oxygenated compounds such as alcohols, aldehydes, ketones, furans, acids, phenols, and ethers. Wood vinegar has antioxidant and free-radical-scavenging properties and is used in agriculture as an antimicrobial, antifungal, insecticide, and plant germination and growth agent. It is also used in food preservation, in medicine, and in the ecological preservation of wood. This review also examines the state of the art in pyroligneous liquid production techniques and factors that could potentially affect its quality.

Potential of poultry residual fat biofuels from thermo-catalytic cracking

Biofuels have been occupying space in the fuel market as a renewable substitute for petrol fuels. The thermal and/or thermo-catalytic cracking using triglyceride biomass stands out among the biofuel production processes. Cracking processes result in the production of coke, bio-oil and non-condensable gases. The quantification of each product in a cracking process is directly linked to operational conditions. This project focuses on the use of residual fat from the poultry processing industry, converting it into biofuel so that it can be used in the industry itself as a source of energy. The quality of the products generated are linked to the raw material used, as well as the conditions used in the cracking process. One way to improve the characteristics of the bio-oil produced can be achieved with the use of a catalyst together with thermal cracking. The literature has shown that in thermo-catalytic cracking, there is lower yield in bio-oil, but with some properties, such as acidity and viscosity closer to the value required by legislation for use in engines. This project aims to add value to an industrial waste, by converting this waste into biofuel using thermo-catalytic cracking, with the possibility of being used in the industry itself, as well as investigating the optimization of the process to improve the quality of bio-oil. The yield of the liquid fraction was around 67 % with an acid value of 58.74 mg KOH/g sample.

Micro-pyrolysis of various lignocellulosic biomasses in molten chloride salts

In fast pyrolysis, the use of molten salts (i.e. eutectic mixtures) has shown potential for improving the heating rates of biomass, which is essential when targeting high bio-liquid yields. Techniques that allow faster screening of suitable eutectic salt mixtures for biomass pyrolysis before scaling up, are thus necessary. To validate a technique for rapid molten salt pyrolysis, micro-scale pyrolysis (py-GC-MS) has been carried out at 350 °C. Different chloride salt compositions (melting point of ∼ 200 °C) were tested in micro-pyrolysis of cellulose, pinewood, wheat straw, and softwood/hardwood Kraft lignin, at biomass to salt ratios from 1 to 20 (wt% biomass/wt% salts). Chloride molten salts pyrolysis highly promoted the depolymerization and dehydration of cellulose resulting mainly in the production of furfural and acetic acid, which are of interest when targeting the production of value-added chemicals. However, some of the eutectic mixtures used were not stable because they hydrolyzed (HCl detection) and volatilized during pyrolysis. Hydrolysis of salts was counteracted partially by adding ZnO, and fully by using less ZnCl2 in the eutectic mixture. On the other hand, the volatilization of salts inside the micro-reactor was suppressed by limiting the time at which the salts were kept at reaction temperatures. It was observed that the salts had a major catalytic effect on the pyrolysis volatiles when compared to those from pure lignocellulosic biomass. Molten salts pyrolysis of Lignoboost Kraft lignin selectively produced guaiacol and syringol, whereas pinewood and wheat straw, like cellulose, resulted mostly in the production of furfural and acetic acid. Overall, the yield of volatiles from all lignocellulosic feedstock was less in the presence of chloride molten salts, which indicated that the salts favored the production of char and/or non-condensable gases, instead of volatiles.

Flash Pyrolysis Experiment on Albizia odoratissima Biomass under Different Operating Conditions: A Comparative Study on Bio-Oil, Biochar, and Noncondensable Gas Products

This study deals with the flash pyrolysis of Albizia odoratissima biomass wastes at different temperature, sweep gas flow rate, and heating rate in a fluidized bed reactor. In the first phase of the experimental work, the effect of temperature (350–550°C) on product yield was analyzed, the second and third phases of the work were to analyze the effect of sweeping gas (N2), flow rate (1.25–2.25 m3/hr), and heating rate (20–40°C/min). The experimental works were carried out to get maximum bio-oil production. The experimental results demonstrated that the maximum yield of bio-oil was obtained at a temperature of 450°C, N2 flow rate of 1.75 m3/hr, and heating rate of 30°C/min. Temperature was found to be the crucial factor rather than sweep gas flow rate in the product distribution. Fourier transform infrared spectroscopy (FT-IR), gas chromatography mass spectroscopy (GC-MS), and elemental analysis were done on the obtained bio-oil, biochar, and noncondensable gas products. The heating value of the bio-oil and biochar was identified as 18.15 and 23.47 MJ/kg, respectively. The chemical analysis of the bio-oil showed that the oil is a mixture of phenol and oxygenated elements. The gas analyses showed that hydrogen and carbon dioxide were dominant, followed by carbon monoxide and methane.

On steady state noncondensable gas buildup in Autonomous Reactivity Control (ARC) systems

The Autonomous Reactivity Control (ARC) system, a new engineered passive safety system for liquid metal reactors, has been the subject of many recent studies, having shown the potential to improve both safety and performance of liquid metal reactors while introducing only a minor impact on normal operations. This study investigates one area of ARC system performance which has not yet been examined — the production of internal noncondensable gases during normal operations. Using neutronic calculations, this study finds that a non-negligible quantity of gases will be produced through transmutation reactions of the internal ARC system fluids, and a lower bound on this quantity is calculated. Through a series of geometric arguments and considerations on mutual solubility and chemical reactivity, the volume and distribution of noncondensable gas buildup is examined for a wide range of ARC system designs. To demonstrate the impact of these noncondensable gases, a series of thermal-hydraulic and transient calculations are performed, and it is shown that the production of noncondensable gases from transmutation of the liquid potassium expander fluid will have negative impacts on the performance of the ARC system, causing an unsteady and restricted actuation which will lead to a reduction of benefits for a given reactor’s transient performance and an increased uncertainty on the state of the system during reactor operations. In the end, multiple mitigation strategies are discussed, but ultimately this study motivates a reevaluation of the fundamental ARC system design so that its benefits may be most fully realized.

Pyrolysis of food waste over a Pt catalyst in CO2 atmosphere

In this study, a method of disposing food waste is introduced via catalytic pyrolysis under CO2 condition. The catalyst and CO2 hindered the generation of condensable compounds, leading to enhancing non-condensable gas generation. However, they did not affect the amount of solid residues left after the thermal reaction. The amount of condensable cyclic compounds was reduced when the catalyst and/or CO2 were used. The enhancement of non-condensable gas production and reduction of cyclic compounds formation were maximized when the Pt catalyst and CO2 were simultaneously applied to the pyrolysis of food waste. For instance, approximately 67.3 % less cyclic compounds, including benzene derivatives, were generated at 700 °C in the presence of the catalyst under a CO2 atmosphere compared to non-catalytic conditions without CO2. The results suggest that a CO2-assisted catalytic pyrolysis is as environmentally benign disposal method for food waste.

Silver nitrate in situ upgrades pyrolysis biofuels from brewer’s spent grain via biotemplating

Bio-based hydrocarbon fuels made from carbonaceous wastes are a renewable and potentially carbon neutral alternative to conventional fossil fuels. Pyrolysis biofuels are limited largely because of a poor overall energy balance along with the fuel’s high viscosity and high oxygen content. This study explores an integrated biorefinery approach to manage Brewer’s Spent Grain (BSG) waste that combines in situ catalytic upgrading of pyrolysis fuel with production of value-added products to improve process economics. By incorporating silver nitrate via a wet impregnation method into BSG prior to pyrolysis, non-condensable gas (particularly hydrogen and ethane) production dramatically increases, while the evolution of methane is largely unchanged. Critically, the peak temperatures at which pyrolysis gases evolve are decreased by the incorporation of silver, suggesting that this process could lower required pyrolysis temperatures. The silver-treated pyrolysis bio-oil showed a considerable increase in furfural, an important precursor in many chemical processes. The silver-impregnated biomass also showed a decrease in 2-methyl-propanal and 2-methyl-butanal yields, and virtually eliminated detectable anthracene and pyrene. In conjunction with the evolved gas results, it is likely that molecular rearrangement and dehydrogenation pathways, as opposed to a complete thermochemical cracking of the bio-oil fraction, are responsible for the catalytic behavior observed. After pyrolysis, the biochar can be oxidized to yield bio-templated, green-synthesized silver micro- and nanomaterials. The integrated biorefinery approach offers a novel path for upgrading pyrolysis biofuels, unifying synthesis of micro- and nanostructured materials and fuel production.

Fractionation of biomass and plastic wastes to value-added products via stepwise pyrolysis: a state-of-art review

Abstract Pyrolysis has been considered as a promising thermochemical process that can convert biomass in nonoxidizing atmospheres to value-added liquid bio-oil, solid biochar, and noncondensable gas products. Fast pyrolysis has a better economic return because of the valuable biofuel production (e.g. bio-oil, syngas). Because of the complexity and heterogeneity of the feedstocks, the one-step pyrolysis often leads to the mixed, acidic, and highly oxygenated liquid products. Moreover, the downstream processes (e.g. deoxygenation) for the desired fuels require high costs on energy and catalysts consumption. Stepwise pyrolysis is defined as a temperature-programmed pyrolysis that can separately obtain the products from each temperature step. It is a feasible approach to accomplish the fractionation by optimizing the pyrolysis process based on the decomposition temperature ranges and products among the biomass constituents. In recent years, the stepwise pyrolysis technology has gained attentions in thermochemical conversion of complex organic solid wastes. Through the stepwise pyrolysis of a real waste, oxygenated and acidic products were concentrated in the first-step liquid product, whereas the second-step product normally contained a high portion of hydrocarbon with low acidity. The stepwise pyrolysis of biomass, plastics, and their mixtures is comprehensively reviewed with the objective of fully understanding the related mechanisms, influence factors, and challenges.

Microwave-assisted pyrolysis of furfural residue in a continuously operated auger reactor: Biochar characterization and analysis

Microwave-assisted pyrolysis (MWAP) of furfural residue (FR) was performed in a continuously operated auger reactor. The effects of temperature and additives on pyrolysis products and char properties were investigated. The yield of FRBC (furfural residue biochar) decreased to 43.62 wt.% and non-condensable gas yield increased to 40.37 wt.% with temperature increasing to 750 °C. However, condensate yield increased with increasing temperature from 450 to 550 °C, reaching maximum (i.e. 21.49 wt.%) at 550 °C, then decreased to 15.65 wt.% as temperature reached 750 °C. Kaolin and K2CO3 promoted production of non-condensable gases and CaO increased the yield of FRBC. The relative proportion (RP) values of carbon, hydrogen, nitrogen and sulfur in FRBC were 50.49–65.07 wt.%, 13.05–26.81 wt.%, 61.99–79.84 wt.% and 60.93–74.16 wt.%, respectively. The highest iodine adsorption value of 127mg/g and methylene blue number of 59 mg/g were achieved for FRBC at 450 °C. Kaolin, CaO and K2CO3 increased methylene blue number, and K2CO3 significantly increased iodine adsorption capacity of FRBC. CaO retained sulfur, chlorine, zinc, and kaolin showed greater retention capacities for copper, nickel, chromium and zinc. The major crystalline phases of sulfur and nitrogen were CaSO4, K2Ca2(SO4)3, Zr(NO3)4 in FRBC and K2Ca2(SO4)3 in FR.

Catalytic Fast Pyrolysis of Kraft Lignin With Conventional, Mesoporous and Nanosized ZSM-5 Zeolite for the Production of Alkyl-Phenols and Aromatics.

The valorization of lignin that derives as by product in various biomass conversion processes has become a major research and technological objective. The potential of the production of valuable mono-aromatics (BTX and others) and (alkyl)phenols by catalytic fast pyrolysis of lignin is investigated in this work by the use of ZSM-5 zeolites with different acidic and porosity characteristics. More specifically, conventional microporous ZSM-5 (Si/Al = 11.5, 25, 40), nano-sized (≤20 nm, by direct synthesis) and mesoporous (9 nm, by mild alkaline treatment) ZSM-5 zeolites were tested in the fast pyrolysis of a softwood kraft lignin at 400–600°C on a Py/GC-MS system and a fixed-bed reactor unit. The composition of lignin (FT-IR, 2D HSQC NMR) was correlated with the composition of the thermal (non-catalytic) pyrolysis oil, while the effect of pyrolysis temperature and catalyst-to-lignin (C/L) ratio, as well as of the Si/Al ratio, acidity, micro/mesoporosity and nano-size of ZSM-5, on bio-oil composition was thoroughly investigated. It was shown that the conventional microporous ZSM-5 zeolites are more selective toward mono-aromatics while the nano-sized and mesoporous ZSM-5 exhibited also high selectivity for (alkyl)phenols. However, the nano-sized ZSM-5 zeolite exhibited the lowest yield of organic bio-oil and highest production of water, coke and non-condensable gases compared to the conventional microporous and mesoporous ZSM-5 zeolites.

Effect of blending on fuel gas composition of pyrolysed plastic wastes

An investigation into the effects of blending on the gaseous product distribution of plastic wastes was successfully carried out. Waste Low Density Polyethylene (LDPE) and waste High Density Polyethylene (HDPE) samples were subjected to thermal pyrolysis in an electric tubular furnace. A study was also carried out to investigateFirst, the effect of heating rate on the volume of the gaseous products was studied. Previous research by other authors showed appreciable gas production occurred at a minimum heating rate of 20oC/min as such hHeating rate valuess of 22oC/min, 26oC/min and 32oC/min were adoptedused . It showed thatwith results showinged that a higher heating rates favoured the production of non-condensable gases in HDPE but caused a persistent decrease in LDPE. The investigation into the effects of blending was then carried out at a temperature range of 480oC – 600oC and heating rate of 22oC/min using blends of 0%, 20%, 40%, 50%, 60%, 80% and 100% LDPE in HDPE. The gaseous product was analysed by gas chromatography and results obtained showed a similarity in hydrocarbon product distribution for both LDPE and HDPE gas products. 100% LDPE showed a composition of 21.84%, 47.39%, 20.78%, 8.40%, and 1.59%; and 100% HDPE showed a composition of 18.88%, 46.91%, 22.89%, 9.59%, and 1.73% for C1, C2, C3, C4, and C5+hydrocarbon molecules respectively. The presence of LDPE in blends of LDPE-HDPE favoured the production of C1 up to 99 mol. %.

Performance of rotary kiln reactor for the elephant grass pyrolysis

The influence of process conditions (rotary speed/temperature) on the performance of a rotary kiln reactor for non-catalytic pyrolysis of a perennial grass (elephant grass) was investigated. The product yields, the production of non-condensable gases as well as the biochar properties were evaluated. The maximum H2 yield was close to that observed for catalytic pyrolysis processes, while the bio-oil yield was higher than reported for pyrolysis of other biomass in rotary kiln reactors. A H2/CO ratio suitable for Fischer–Tropsch synthesis (FTS) was obtained. The biochars presented an alkaline pH (above 10) and interesting contents of nutrients, as well as low electrical conductivity, indicating a high potential as soil amendment.

Torrefaction of Biomass: Effect of Temperature on the Properties of Liquid and Gaseous Products

The torrefaction of rice husk was performed in a laboratory-scale torrefaction reactor at different temperatures (200, 230, 260, and 290 °C) for 30 min. It was found that the decomposition of hemicellulose was the direct reason for changes in the fuel properties of solid products after torrefaction. As the torrefaction temperature rose from 200 °C to 290 °C, the yield of torrefied rice husk decreased gradually from 97.47% to 67.03%, whereas the yields of liquid and noncondensable gas products increased from 2.01% to 15.67% and from 0.52% to 17.30%, respectively. Liquid products contained water and a small amount of acetic acids. CO2 and CO were the main gas products of rice husk torrefaction.

Computational Fluid Dynamics Modeling of Palm Fruit Pyrolysis in a Fast Fluidized Bed Reactor

The palm fruit biomass is introduced into the pyrolysis reactor bed and the transport equations for heat, mass and momentum transfer are solved using computational fluid dynamics (CFD) technique. The Eulerian-Eulerian approach is employed to model fluidizing behavior of the sand for an externally heated reactor prior to the introduction of the biomass. The particle motion in the reactor is computed using the drag laws which depend on the local volume fraction of each phase. Heat transfer from the fluidized bed to the biomass particles together with the pyrolysis reactions were simulated by Fluent CFD code through user-defined function (UDF). Spontaneous production of pyrolysis oil, char and non-condensable gases (NCG) confirm the observation widely reported in literature. The computer model can potentially be used to assess other candidate biomass sources also to assist design of optimized pyrolysis reactors.

Vapor-Phase Cracking of Eugenol: Distribution of Tar Products as Functions of Temperature and Residence Time

Knowledge of the product distribution and kinetics of the secondary vapor-phase cracking of biomass tar is crucial for the design and optimization of biomass thermochemical conversion processes, such as fast pyrolysis, gasification, and combustion. In this study, we have examined the distribution of condensable tar products from the vapor-phase cracking of eugenol, a model-fuel compound representative of the lignin structural entities found in biomass. Pyrolysis experiments were investigated at different temperatures (300–900 °C) and residence times (τ = 1 and 3 s) in a non-isothermal laminar-flow reactor operated at atmospheric pressure. Tar products were analyzed using gas chromatography with mass spectrometric detection. Eugenol conversion commenced rapidly above 350 °C at τ = 3 s and above 400 °C at τ = 1 s. Complete conversion was attained at 550 and 600 °C at τ = 3 and 1 s, respectively. A numerical model incorporating laminar-flow, non-isothermal temperature profile and pseudo-unimolecular kinetics was developed to model the eugenol conversion data. The model agreed very well with the experimental data, and the derived global kinetic parameters for overall eugenol decomposition were A = 1014 s–1 and Ea = 50.7 kcal mol–1. Tar products were comprised of oxygenates and aromatic hydrocarbons. Identified oxygenates include phenols, furans, ethers, and acids. The aromatics consisted of single-ring aromatic compounds and polycyclic aromatic hydrocarbons. Oxygenates were observed as tar products in the temperature range of 350–850 °C at both τ = 1 and 3 s. Aromatic hydrocarbons were observed as tar products at temperatures above 650 °C. Most of the identified aromatic hydrocarbons showed an increase in the yield above 650 °C at both τ = 1 and 3 s. At all temperatures, yields of oxygenates and aromatics were generally higher at τ = 1 s than at τ = 3 s. Mass balance closure was not achieved above 400 and 500 °C at τ = 3 and 1 s, respectively, with discrepancies in the mass balances increasing with an increase in the temperature. The discrepancies in the mass balances can be attributed to the formation of noncondensable gas products.

CORIUM COOLABILITY UNDER EX-VESSEL ACCIDENT CONDITIONS FOR LWRs

In the wake of the Three Mile Island accident, vigorous research efforts were initiated to acquire a basic knowledge of the progression and consequences of accidents that involve a substantial degree of core degradation and melting. The primary emphasis of this research was placed on containment integrity, with: i) hydrogen combustion-detonation, ii) steam explosion, iii) direct containment heating (DCH), and iv) melt attack on the BWR Mark-I containment shell identified as energetic processes that could lead to early containment failure (i.e., within the first 24 hours of the accident). Should the core melt fail the reactor vessel, then non-condensable gas production from Molten Core-Concrete Interaction (MCCI) was identified as a mechanism that could fail the containment by pressurization over the long term. One signification question that arose as part of this investigation was the effectiveness of water in terminating an MCCI by flooding the interacting masses from above, thereby quenching the molten core debris and rendering it permanently coolable. Successful quenching of the core melt would prevent basemat melt through, as well as continued containment pressurization by non-condensable gas production, and so the accident progression would be successfully terminated without release of radioactivity to the environment. Based on these potential merits, ex-vessel corium coolability has been the focus of extensive research over the last 20 years as a potential accident management strategy for current plants. In addition, outcomes from this research have impacted the accident management strategies for the Gen III+ LWR plant designs that are currently being deployed around the world. This paper provides: i) an historical overview of corium coolability research, ii) summarizes the current status of research in this area, and iii) highlights trends in severe accident management strategies that have evolved based on the findings from this work.

Characterization of bio-oil from induction-heating pyrolysis of food-processing sewage sludges using chromatographic analysis

In this study, gas chromatography–mass spectrometry (GC–MS) was used to analyze the pyrolytic bio-oils and gas fractions derived from the pyrolysis of industrial sewage sludges using induction-heating technique. The liquid products were obtained from the cryogenic condensation of the devolatilization fraction in a nitrogen atmosphere using a heating rate of 300 °C/min ranging from 25 to 500 °C. The analytical results showed that the pyrolysis bio-oils were very complex mixtures of organic compounds and contained a lot of nitrogenated and/or oxygenated compounds such as aliphatic hydrocarbons, phenols, pyridines, pyrroles, amines, ketones, and so on. These organic hydrocarbons containing nitrogen and/or oxygen should originate from the protein and nucleic acid textures of the microbial organisms present in the sewage sludge. The non-condensable devolatilization fractions were also composed of nitrogenated and oxygenated compounds, but contained small fractions of phenols, 1H-indoles, and fatty carboxylic acids. On the other hand, the compositions in the non-condensable gas products were principally carbon dioxide, carbon monoxide and methane analyzed by gas chromatography–thermal conductivity detector (GC–TCD).

Different pyrolytic pathways of levoglucosan in vapor- and liquid/solid-phases

Influence of the amount of levoglucosan-loading on the pyrolysis behavior was studied in N 2 at 400 °C with a dual-space closed ampoule reactor. The results indicated that the pyrolytic pathways are different between vapor- and liquid/solid-phases. Relative contribution of these two pyrolysis conditions changed depending on the amount of levoglucosan-loading. In vapor-phase, levoglucosan was selectively converted to the non-condensable gas (mainly CO and CO 2), while char and other condensable low molecular-weight (MW) products (furfural, 5-hydroxymethyl furfural, glycolaldehyde, hydroxyacetone, acetic acid and formic acid) were formed more selectively in liquid/solid-phase. Furthermore, the aldehydes and hydroxyacetone formed from the pyrolysis in liquid/solid-phase were found to stabilize levoglucosan in vapor-phase. Clearly-observed isotope effect with acetaldehyde-1- d 1 suggested that the vapor-phase gasification of levoglucosan proceeds in a radical-chain mechanism.