Pyrolysis Product Distribution Research Articles

Catalytic upgrading of Naomaohu coal pyrolysis volatiles over NiAl and NiLiAl oxides

Catalytic upgrading of volatiles is an essential technology to improve the product distribution of pyrolysis for the clean and efficient utilization of low-rank coals. In this work, novel acid-base bifunctional catalysts composed of Ni/Li/Al oxides were designed and prepared using LDH precursors with tunable chemical composition and structural properties. The catalysts were systematically characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), physisorption, NH3-temperature programmed desorption (NH3-TPD), CO2-temperature programmed desorption (CO2-TPD), H2-temperature programmed reduction (H2-TPR), and scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS). A two-stage fixed bed reactor was employed to evaluate the performance of the catalysts. Characterization results suggest that the crystal size of NiO and the surface area of the catalyst decreased with increasing Li content and decreasing Ni content in the catalyst, while the pore volume and pore diameter were positively correlated with Li content. Moreover, the addition of Li reduced the amount of weak acid sites and raised the amount of total basic sites. Consequently, the bifunctional catalysts boosted the yield of light tar and the contents of aromatics and phenols in tar. Specifically, with the highest total acid sites (569 μmol/g) promoting the cracking of heavy pitch components, Ni2.5Li0.5Al1 decreased the content of pitch in tar to 23.8wt.%, representing a 42.7% drop from the corresponding non-catalytic pyrolysis. Accordingly, it improved the light tar yield to 7.2wt.%, which was 18% higher than non-catalytic pyrolysis. 450°C is identified as a suitable temperature for the catalytic upgrading of volatiles from Naomaohu coal; higher catalysis temperatures at 500°C and 550°C led to lower tar yield and lower phenols content, along with higher gas yield and more carbon deposition.

Revealing the nitrogen migration mechanism during pyrolysis and steam gasification of biomass: A combined ReaxFF MD and DFT study

The biomass pyrolysis/gasification technology takes advantages of high efficiency and carbon neutrality, which is promising for high value-added products fabrication. However, biomass possesses relatively high amount of N especially for seaweeds and municipal sludge wastes, and the lack of N migration mechanism has resulted in emission of N-containing pollutants and limited its industrial application. In this work, a simulation investigation combining reactive force field molecular dynamic and density functional theory calculations was performed to study the conversion mechanisms of N-containing species in the pyrolysis/gasification of biomass processes. The glutamic acid and cellulose were selected as the model compounds of N-containing and typical compositions of biomass, respectively, and six models containing multiple mass ratios of glutamic acid to cellulose and steam to feedstock were constructed. The results show that the majority of nitrogen in the original model is converted towards NH3-N (62%) during glutamic acid pyrolysis by direct cleavage, hydrogen capture, deamination, and decarboxylation. The presence of cellulose effectively inhibits the decomposition of NH3 at high temperature range, thereby increasing the yield of NH3-N (up to 70%) and restraining the conversion of nitrogen into mesomolecules. The introduction of H2O provides a substantial amount of •H radicals, which facilitates the conversion of nitrogen into NH3-N. During DFT calculations, eight reaction pathways for the formation of N-containing products were proposed on the basis of distribution of pyrolysis products. The glutamic acid cleavage reaction achieves the lowest energy barrier, and the deamination of glutamic acid towards a ternary cyclic ether is found to be the most feasible pathway for the NH3 production. This work can provide theoretical support for nitrogen pollutants mitigation during pyrolysis and steam gasification of biomass processes.

Effect of lignin modification on the selectivity of pyrolysis products from softwood kraft lignin

The synthesis of phenol via pyrolysis of lignin can be envisaged as a prospective approach for the high-value utilization of lignin, Herein, we describe an in-depth investigation of the selective modification of lignin to effectively adjust the distribution of lignin pyrolysis products. We found that hydroxypropyl modification of lignin can facilitate the elimination of methoxy from the lignin macromolecule and improve the selectivity of phenol products. In addition, increasing the carbon number of the lignin side chains causes polymerization of pyrolysis products, which is unfavorable for the synthesis of fine chemicals via lignin pyrolysis. Conversely, an increase in lignin side-chain hydroxyl content can lead to more liquid-phase products from lignin pyrolysis, and the selectivity of phenol and its congeners will also increase. As a result, the yield of liquid products obtained via pyrolysis of lignin modified via selective oxyalkylation can reach 52 %, and the relative content of phenol and its homologs can reach 45.2 %.

Co-pyrolysis of waste tire with agricultural and forestry residues: Pyrolysis behavior, products distribution and synergistic effects

Co-utilization of waste tires (WT) and agricultural and forestry residues (AFR) provides an effective means to produce energy while simultaneously providing solution for waste treatment and environment protection. In this paper, co-pyrolysis of WT and AFR (cotton stalk, CS, peanut shell, PS, and poplar branch, PB) was performed using thermogravimetric analysis (TGA), Fourier transform infrared spectrometer (FTIR), and pyrolyzer coupled with gas chromatograph/mass spectrometer (Py-GC/MS). The synergistic effects of mass loss rate and hydrocarbon content were quantified from the results of co-pyrolysis of WT with CS, PS, or PB with the weighted average of individual pyrolysis of the feedstocks. The results showed that the mass loss rate of WT with CS, PS, or PB in co-pyrolysis increased by 3.06 %, 3.84 %, and 0.61 %, respectively, compared to the weighted average of individual pyrolysis, while the hydrocarbon content increased by 19.20 %, 18.26 % and 2.97 %, respectively. The addition of AFR to WT made the pyrolysis easier. In co-pyrolysis, the amount of O-compounds decreased while that of hydrocarbons (aromatic hydrocarbons and aliphatic hydrocarbons) increased. Co-pyrolysis of AFR and WT had an effect on reducing aromatic and nitrogen content. These results provide insights into the synergistic effects, from the products distribution and offer potential waste treatment method for these wastes via thermochemical conversion.

Catalytic pyrolysis of high-density polyethylene (HDPE) over hierarchical ZSM-5 zeolites produced by microwave-assisted chelation-alkaline treatment

A new microwave (MW) assisted chelation-alkaline strategy was developed to produce hierarchical ZSM-5 zeolites (with external surface area of 203 m2/g) in minutes, leading to the formation of heterogeneous structure with a high-silica shell and aluminium-rich core (silicon-to-aluminium ratios of 49.2 and 37.6, respectively). The zeolites were assessed comparatively by catalytic pyrolysis of high-density polyethylene (HDPE). Compared to the mesoporous ZSM-5 zeolite prepared by the conventional alkaline treatment (via desilication by the NaOH aqueous solution), the hierarchical zeolite by the MW-assisted method showed comparable kinetics in catalytic pyrolysis of HDPE, but with the improved stability in the cyclic pyrolysis-regeneration tests. The improved stability could be due to the better-preserved structural integrity thanks to the relatively milder surface etching by the MW-assisted chelation dealumination method. In addition, compared to the parent ZSM-5, the product distribution of HDPE catalytic pyrolysis over the hierarchical ZSM-5 zeolite showed a higher portion of oil products (i.e., 12 wt% vs. 6.9 wt%) and an improved alkane-to-olefin ratio in the oil products (2.22 vs. 1.86, respectively) due to the reduced acidity and improved hydrogen transfer ability. The MW-assisted chelation-alkaline treatment could be a new strategy to regulate the trade-off between stability and activity of zeolites for catalytic applications.

Insight into pyrolysis behaviors of cedar under different atmospheres via a fixed-bed reactor

Pyrolysis, as an efficient route for biomass, usually suffers the influence of pyrolysis atmosphere by the interaction with free radicals from biomass pyrolysis. To investigate the effects of pyrolysis atmosphere on cedar pyrolysis, several atmospheres including CH4, H2, CO2, CO, CH4/CO2 and H2/CO were used for CS pyrolysis on a fixed-bed reactor and the pyrolysis process was revealed based on products distribution, tar quality and compositions. The results show that the components in pyrolysis atmosphere apparently affect the distribution of pyrolysis products and play different roles in cedar pyrolysis. Tar yields under different atmospheres follow the order of H2/CO > H2 > CH4/CO2 > CO2 > CO > N2 > CH4. The highest tar yield of 45.5 wt.% was obtained under H2/CO atmosphere at 600 °C. Char yield was decreased under H2 by suppressing secondary reaction and followed the order of H2 < H2/CO < CH4/CO2 < N2 < CO2 < CO < CH4. The content of ketones was improved under CO2 atmosphere. The introduction of H2 mainly increases naphthalenes, benzenes, ketones and phenols; while the formation of acids, esters, aldehydes and furans was inhibited under CO atmosphere. Integrated process of biomass pyrolysis with CO2 reforming of CH4 can greatly increase tar yield and change tar compositions, which is ascribed to the participation of H-rich free radicals from CO2 reforming of CH4. This work provides a route to improve the yield of pyrolysis tar and adjust tar components.

Rapid pyrolysis mechanism and product distribution of coal model compounds containing typical C–O bonds

The structure and reactivity of coal is the core problem of coal chemistry, and solving it at the molecular level has been an international unsolved problem. The chemical similarity-based coal chemistry group elevates the study from the macroscopic to the molecular level. However, the previous free radical mechanism lacks experimental confirmation and theoretical computational support. Here, the pyrolysis products of model compounds are first utilized to predict pyrolysis. The hydrogen-donating solvent is then used as a radical trap to confirm the reaction. Subsequently, density functional theory calculations are utilized to aid in the validation. Finally, family components are utilized to demonstrate the universality of the free radical mechanism of coal pyrolysis. This work combines radical trapping with quantum chemical calculations to analyze the radical reaction mechanism of coal pyrolysis in depth at the molecular level. This will provide a theoretical basis for coal pyrolysis and clean and efficient utilization.

Co-pyrolysis of low-rank coal and rice stalk: A comprehensive study on product distributions, product properties, and synergistic effects

Co-pyrolysis of low-rank coal and rice stalk is an important way to achieve hierarchical and efficient utilization of energy. This work explored how blend ratios (0–100 wt%) and temperatures (773–1073 K) affect pyrolysis product distribution and characteristics. The results showed that a higher rice straw ratio (80 wt%) significantly reduced the yield of char (22.38–26.9 wt%) compared with 20 wt% of rice straw at different temperatures. The yield and physicochemical properties of target products were closely related to process parameters, which can provide a promising opportunity to acquire desired products by reaction conditions optimization. Co-pyrolysis was able to inhibit the production of large aromatic ring structures in char. High temperature promoted the generation of cross-linked structures, which was influenced by the blend ratio. The synergistic effects of BET surface area and pore volume were most pronounced when the J content was 40 wt% at 873 K, and their increments were 59.6 m2/g and 0.027 cm3/g, respectively. For the char derived from lower rice straw proportions (0, 20, and 40 wt%), the main combustion range and the maximum combustion rate temperature showed a progressive shift towards higher values with temperature increasing. The research is valuable of guiding high-value utilization of agricultural residues and energy transitions.

Pyrolysis characteristics and product distribution of oil sludge based on radiant heating.

It needs to be improved the conversion efficiency and stable operation of conventional pyrolysis with high-temperature flue gas heating (HFH). Herein, a new radiative heating (RH) pyrolysis method is proposed. Experimental studies are carried out on a self-made radiation pyrolysis pilot plant to investigate the effects of different factors (pyrolysis final temperature, residence time, and carrier gas volume) on product distribution. The results show that with the increase of pyrolysis temperature, the yield of the gas phase consistently increases, and the proportion of CH4 and H2 in the pyrolysis gas reaches 62.31% at 700°C. The yield of the liquid phase increases and then decreases. The recovery rate of pyrolysis oil achieves 68.07% when the pyrolysis temperature is 600°C with main components of ketones and unsaturated hydrocarbon compounds. The yield of the solid phase consistently decreases. The RH in this work generates more pyrolysis gas in the pyrolysis process and alleviates the effects of fouling layers on the continuous operation of the equipment which has guiding significance for the efficient resource utilization of oil sludge.

Preparation of monocyclic aromatic hydrocarbons from industrial lignin residue and polyethylene co-pyrolysis by microwave-assisted in fluidized bed based on bimetal-loaded HZSM-5/MCM-41 core-shell catalyst

Enzymatic hydrolysis lignin (EHL), lignosulfonate (LS), alkali lignin (AL), and hydrolysis lignin (HL) residues are mostly burned for heating in industrial production, which greatly wastes resources and pollutes the environment. In this study, we investigated the effects of different temperatures and catalyst-to-biomass mass (C/B) ratios on the relative content of hydrocarbons in the products by microwave-assisted pyrolysis in a fluidized bed. Co and Ni bimetal-loaded molecular sieve with core-shell structure (Co-Ni@H/M) was used as the catalyst. The main component of waste plastic, polyethylene (PE), was pyrolyzed with these four lignin residues to prepare monocyclic aromatic hydrocarbons (MAHs), and the mechanism of synergistic interaction in co-pyrolysis was investigated. It was shown that the maximum liquid phase yield and hydrocarbons relative content were obtained at 550 °C when lignin residues were pyrolyzed alone. Compared with the pyrolysis of lignin residues alone, the liquid phase and gas phase yields of co-pyrolysis were improved, while the solid phase yield decreased. Moreover, the temperature for maximum liquid phase yield and hydrocarbons relative content were reduced to 500 °C. Further exploration of the liquid phase products revealed that the relative contents of hydrocarbons in the four lignin residues and PE (EHL-PE, LS-PE, AL-PE, and HL-PE) co-pyrolysis products at 500 °C were 49.6 %, 33.1 %, 37.7 %, and 43.2 %, respectively, with MAHs as the main components. The results of the effect of different C/B ratios on the distribution of pyrolysis products showed that Co-Ni@H/M promoted the deoxygenation of oxygenated compounds, especially phenolic compounds, and the conversion of aliphatic hydrocarbons into MAHs by cyclization and aromatization.

Pyrolysis characteristics and product distribution of low-rank coal with heat-carrying particles adopting TG-FTIR and a novel self-mixing down tube reactor

A novel self-mixing down tube (SDT) pyrolyzer has been developed, which can separate the heat carrying particles preheated in the fluidized bed from the coal, and the two can be mixed through a specific structure to instantly heat the coal particles to a predetermined temperature. The present study investigated the pyrolysis behavior of low-rank coal with hot silica sand heat-carrying particles adopting TG-FTIR. Identifies optimal conditions for maximum tar production in a laboratory-scale SDT using a significantly larger range of coal feed rates (4 kg/h). An increase in the degree of coal metamorphism increased the initial temperature and the yield of char. The tar yield from Huolinhe lignite coal (6.56 %) and Daliuta bituminous coal (7.48 %) showing a trend of first increased and then decreased with elevating the operating temperature and optimal temperature at 520 °C, respectively. The effect of coal particle size on tar yield mainly comes from the different degrees of secondary cracking caused by contact with solid heat-carrying particles as well as the differences in the content of macerals. GC‒MS spectra of tar and deposited carbon on silica sand indicated that heavy tar can easily deposit on the surface of sand and form char through polymerization reactions.

Enhanced microwave assisted pyrolysis of waste rice straw through lipid extraction with supercritical carbon dioxide.

A combination of supercritical carbon dioxide (scCO2) extraction and microwave-assisted pyrolysis (MAP) have been investigated for the valorisation of waste rice straw. ScCO2 extraction of rice straw led to a 0.7% dry weight yield of lipophilic molecules, at elevated temperatures of 65 °C and pressures of 400 bar. Lipid compositions (fatty acids, fatty alcohol, fatty aldehydes, steroid ketones, phytosterols, n-alkanes and wax esters) of the waxes obtained by scCO2 were comparable to those obtained Soxhlet extraction using the potentially toxic solvent n-hexane. ScCO2 extraction positively influenced the pyrolysis heating rate, with a rate of 420 K min-1 for particles of 500-2000 μm, compared to 240 K min-1 for the same particle size of untreated straw. Particle size significantly affected cellulose decomposition and the distribution of pyrolysis products (gaseous, liquid and char), highlighting the importance of selecting an adequate physical pre-treatment. TG and DTG of the original rice straw and resulting biochar produced indicated that cellulose was completely decomposed during the MAP. While a rapid pressure change occurred at ∼120 °C (size > 2000 μm) and ∼130 °C (size 500-2000 μm) during MAP and was associated with the production of incondensable gas during cellulose decomposition, this takes place at significantly lower temperatures than those observed with conventional pyrolysis, 320 °C. Wax removal by scCO2 influences the dielectric properties of the straw, enhancing microwave absorption with rapid heating rates and elevated final pyrolysis temperatures, illustrating the benefits of combining these sustainable technologies within a holistic rice straw biorefinery.

Investigating primary decomposition of polypropylene through detailed compositional analysis using two-dimensional gas chromatography and principal component analysis

This work systematically assessed the effects of pyrolysis parameters, such as sample weight, particle size, carrier gas flow rate, and temperature, on product speciation and distribution in the pyrolysis of polypropylene (PP) for intrinsic kinetics. This study employed a Box-Behnken design (BBD), along with the analysis of BBD boundary conditions, as well as conditions beyond the BBD to validate the pyrolysis conditions in the primary decomposition of PP using a micropyrolyzer coupled to two-dimensional chromatography with flame ionization and time-of-flight spectrometer detectors (Py–GC×GC–FID/TOF–MS). Statistical differences and similarities in the product distribution of the experiments were determined using principal component analysis (PCA). Characteristic time analysis indicated that the sample weights employed in the study were within the isothermal kinetically controlled region, with film thickness ranging from 4.85 to 14.46 µm. The analysis of 600 pyrolysis products identified and quantified in the pyrolysis of PP for the condition combinations evaluated in BBD resulted in statistical differences at temperatures of 460, 530, and 600 oC, with C3 to C35 yields ranging from 39.88 ± 2.08 to 66.61 ± 3.26 wt%. However, no statistical differences were found in the pyrolysis product distribution within the ranges of sample weight (50 – 150 µg), particle size (53 – 125, 125 – 300, and >300 µm), and carrier gas flow rate (100 – 300 ml min-1) studied in the BBD experimental space. The analysis of the border conditions showed that a combination of the lowest carrier gas flow rate (100 ml min-1) and the highest sample weight (150 μg) resulted in statistically different product distribution at the studied pyrolysis temperatures compared to the combination suggested by BBD. Conditions beyond the BBD, including a sample weight of 800 µg and a carrier gas flow rate of 30 ml min-1, resulted in statistically different product distributions compared to the BBD. Notably, new products such as polycyclic aromatic hydrocarbons (PAHs) were identified. The findings from this work clearly show the importance of selecting appropriate pyrolysis parameters to obtain kinetically relevant experimental data, which in turn serves as a valuable guide for the development and validation of (micro-) kinetic models.

Enhanced co-pyrolysis of corn stalk and bio-tar into phenolic-rich biooil: Kinetic analysis and product distributions

This study explores the interaction between corn stalk and bio-tar through co-pyrolysis, aiming to provide insights for the valorization of bio-tar and biomass into phenolic-rich biooil. The study focuses on the thermal behavior analysis, pyrolysis kinetic, and product distributions during the co-pyrolysis process. The results demonstrate a significant interaction between bio-tar and corn stalk during the co-pyrolysis process. Notably, the co-pyrolysis of bio-tar and corn stalk with a ratio of 1:3 exhibits the most pronounced synergistic effect, enhancing the thermal decomposition of corn stalks. Kinetic modeling calculations reveal a reduction in activation energy for all mixing ratios, with a substantial decrease of 72.87 kJ/mol observed for the 1:3 bio-tar-to-stalk ratio. Additionally, the distribution of pyrolysis products varies with different mixing ratios, with lower bio-tar addition (ratio of bio-tar to stalk = 1:3) favoring phenolic compound production (>70% of phenols in biooil). These findings contribute to a better understanding of the interaction between bio-tar and corn stalk during co-pyrolysis, offering valuable insights for the efficient utilization of biomass resources.

Impact of pretreatment with photocatalysis sequential coupling Fenton oxidation on physicochemical properties, pyrolysis behaviors, and product distribution of walnut shell

Naturally occurring alkali and alkaline earth metals (AAEMs) in biomass can adversely affect its pyrolysis behavior and product distribution and contribute to ash deposition in boilers. To address these challenges, we proposed a new idea of photocatalysis sequential coupling Fenton oxidation for biomass pretreatment. Our findings revealed that sequential pretreatment has the optimal moderating effects on biomass relative to individual photocatalysis and Fenton oxidation. The lignin and AAEMs in biomass were effectively reduced via sequential pretreatment, which was accompanied by cellulose content increased by 80.78% relative to untreated. Also, the slagging/fouling inclinations of biomass were successfully alleviated, and the pyrolysis performance was effectively improved. The kinetic parameters obtained based on the Coats-Redfern method can characterize the pyrolysis behavior well. During fast pyrolysis, sequential pretreatment caused the productivity of bio-oil was increased by 30.14% relative to untreated. In particular, the productivity of levoglucosan in bio-oil was increased by 364.71%. This study presented a novel and effective pretreatment strategy to improve the pyrolysis behavior and product distribution of biomass and alleviate ash deposition problems in boilers.

Study on the Relationship between the Structure and Pyrolysis Characteristics of Lignin Isolated from Eucalyptus, Pine, and Rice Straw through the Use of Deep Eutectic Solvent.

Understanding the pyrolysis product distributions of deep eutectic solvent (DES)-isolated lignins (DESLs) from different types of biomass is of great significance for lignin valorization. The structure and pyrolysis properties of DESLs obtained from eucalyptus (E-DESL), pine (P-DESL), and rice straw (R-DESL) were studied through the use of various methods such as elemental analysis, GPC, HS-GC, and NMR techniques, and the pyrolysis characteristics and product distributions of the DESLs were also further investigated through the use of TGA, Py-GC/MS, and tubular furnace pyrolysis. DESLs with high purity (88.5-92.7%) can be efficiently separated from biomass while cellulose is retained. E-DESL has a relatively low molecular weight, and P-DESL has a relatively higher hydrogen-carbon effective ratio and a lower number of condensation structures. The Py-GC/MS results show that, during DESL pyrolysis, the monomeric aromatic hydrocarbons, p-hydroxyphenyl-type phenols, and catechol-type phenols are gradually released when the guaiacyl-type phenols and syringyl-type phenols decrease with the rising temperature. 4-methylguaiacol and 4-methylcatechol, derived from the guaiacyl-type structural units, are positively correlated with temperature, which causes a significant increase in products with a side-chain carbon number of 1 from P-DESL pyrolysis. 4-vinylphenol, as a representative product of the R-DESL, derived from p-hydroxyphenyl-type structural units, also gradually increased. In addition, the P-DESL produces more bio-oil during pyrolysis, while gases have the highest distribution in E-DESL pyrolysis. It is of great significance to study the characteristic product distribution of lignin isolated through the use of DES for lignin directional conversion into specific high-value aromatic compounds.

New insights into brominated epoxy resin type WPCBs pyrolysis mechanisms: Integrated experimental and DFT simulation studies

Pyrolysis is a recycling technology for waste circuit boards (WPCBs) with a wide range of applications. In this research, the brominated epoxy resin (BER) type WPCBs were taken as the research object, and the optimal pyrolysis process parameters were determined. Combined with experiments and density functional theory (DFT) calculations, the pyrolysis gaseous generation pattern and product distribution of BER type WPCBs were analyzed, and the generation mechanism of phenol, bromide and other pyrolysis products was investigated in depth. The results of the study showed that the pyrolysis rate of WPCBs exceeded 95 % under optimal reaction conditions. In the initial phase of the pyrolysis of WPCBs, the BER's CO bonds and a portion of Ph-Br bonds will be broken, leading to the production of intermediates such propylene oxide, bisphenol A, isopropyl alcohol, tetrabromobisphenol A and HBr. Among them, propylene oxide can generate ethylene oxide through free radical reaction. In the second stage, intermediates such as bisphenol A undergo homolytic cleavage and radical addition to form phenols, bromides, alcohols, ketones and other pyrolysis products.

Investigation of the effect of alumina porous media on the polyethylene waste pyrolysis with continuous feed

This study investigates the pyrolysis of polyethylene waste in a continuous-feed mode to provide novel insights into recycling waste plastics. Alumina (Al2O3) porous media has been introduced into the pyrolysis reactor to study its effect on continuous-feeding plastic waste pyrolysis. The pyrolysis product yields, oil fractions, and gas components have been determined under varying porous media structures, i.e., thickness and pore size, and operating parameters, i.e., temperature and gas-carrying velocity. To the best of our knowledge, it is the first attempt to investigate the influence of porous media pore size on the thermal decomposition of waste polyolefin in continuous feeding mode. The results reveal that higher thicknesses and smaller pore sizes of porous media can enhance the properties of pyrolysis oil with lower heavy fractions (>C20). The aromatization of light olefins is triggered when the temperature exceeds 520 °C, resulting in a rapid increase in light fraction (<C12) in pyrolysis oil. Moreover, the gas-carrying velocity determines the pyrolysis product distribution by regulating the volatiles' residence time.

Research on the application of catalytic materials in biomass pyrolysis

Biomass, as a very important renewable resource, its efficient conversion was an important way to achieve zero CO2 emissions, provide clean and renewable energy, and promote the resource utilization of agricultural waste. Biomass pyrolysis, as a technology that could simultaneously obtain high value-added energy and chemical products such as biochar, bio-oil, and combustible gas, had received widespread attention, in which the role of catalysts in biomass pyrolysis had also been widely studied. In this thesis, the application of catalysts in biomass pyrolysis was reviewed in detail on the basis of introducing the principle and pyrolysis methods of biomass pyrolysis, and found that catalysts could effectively improve the distribution and properties of pyrolysis products, especially for the reforming of bio-oil and bio-gas, which had shown outstanding performance in green energy and functional chemicals. At the same time, the current problems of catalysts in biomass pyrolysis were analyzed, and new thoughts were proposed for future research on biomass catalytic pyrolysis, with a view to providing new ways for efficient catalytic pyrolysis and green sustainable development of biomass.

Characterising flame-retardant mechanism of phosphorous-containing intumescent coating on polyethylene via ReaxFF MD simulations

Localised flame-retardant (FR) chemistry of polymer composites is complex, versatile and microscopic depending on the combination of polymer matrix and various FR systems. Particularly, the pyrolysis behaviour of the polymers can be varied and reinforced by effective microscopic synergistic effects between coating compositions. However, these atomistic reactions can be difficult to be characterised via experimental approaches. In this study, experimental studies and reactive molecular dynamic (ReaxFF-MD) simulation techniques were utilised to identify the thermal degradation behaviour of flame retarded high-density polyethylene (HDPE), coated with phosphoric acid (PA) and pentaerythritol (PER). The simulations tracked the pyrolysis product distribution under different heating temperatures and elucidated the pyrolysis hindrance offered by the FR system. The atomistic reaction pathways of phosphorus-based FR mechanism were also characterised, including secondary reactions and intermediate species, such as P-O-C and P-O-P cross-linking between FRs and radical capturing effects. These reactions were found to be increasing the C/H ratios of pyrolysed hydrocarbons and the aromaticity of residues. After applying the periodic removal techniques, the simulations can even predict the residue weight percentage of the polymer and exhibit similar degradation behaviour to the experimental results.