Initial Pyrolysis Temperature Research Articles

Engineering cellulose nanofibril aerogel for reinforcing polymethyl methacrylate with superior mechanical strength, high transparency, and improved thermal stability

In this study, a new strategy for preparing cellulose nanofibers/polymethyl methacrylate (CNF/PMMA) composite with high strength and high transmittance was developed. The UV curing technique was adopted to induce the polymerization of MMA and the grafting modification of methacryloylated CNF aerogel (CNFMA). The compatibility between CNF aerogel and PMMA was significantly improved through the grafting modification of CNF aerogel. The cold ultraviolet photopolymerization strategy makes the polymerization reaction much milder. The transmittance of the CNFMA/PMMA composite was 86.45 %, showing only a slight reduction compared to PMMA. Its tensile strength increased to 69.21 MPa, about twice that of PMMA, and 1.5 times that of CNFpure/PMMA, proving the interaction between CNF and PMMA was greatly enhanced due to the successful grafting of PMMA onto the surface of CNF. The glass transition temperature is 108.1 °C, which increased by nearly 20 %. The thermal stability has also been improved, as reflected by a 10 % increase in the initial pyrolysis temperature. Overall, this work provides a mild and green preparation method for CNF/PMMA composites, making them suitable for applications in the field of high-strength organic glass.

Design and processing of SiOC/SiC/Si3N4/C ceramics with hierarchical porosity and non-oxide nanostructures

An integral study on the development and characterization of porous SiOC/SiC/Si3N4/C-based ceramic bodies was conducted using a less-explored approach, which is based on the direct consolidation of previously unstudied composite systems (methacryloxypropyl silsesquioxane/sucrose/prepyrolyzed powder), burn-out, and N2 pyrolysis (1300–1400 °C). Their textural, physicochemical, and microstructural properties depended on the initial system composition and pyrolysis temperature; the latter was also decisive in the materials' oxidative stability. At the highest pyrolysis temperature, SiC, mainly in the form of whiskers, and Si3N4 formed, the amount of SiOC decreased, Si2N2O crystallized, and nanocrystalline graphite-type carbon underwent graphitization. The final bodies exhibited macro- and mesopores, with micropores present only in those pyrolyzed at 1300 °C. This latter material presented the highest specific surface area, making it a potential candidate for catalysis in non-oxidizing environments at high temperatures or in oxidizing conditions at lower temperatures. Meanwhile, the material developed at 1400 °C offered high-temperature oxidative stability.

Kinetic characteristics and product distribution of tar-rich coal in-situ underground pyrolysis: Influence of heterogeneous coal seam

Tar-rich coal contains more hydrogen-rich structures such as aliphatic side chains and bridge bonds, which is a good raw material for coal to oil. In-situ underground pyrolysis of tar-rich coal has significant advantages such as environmental friendliness and high safety factor; it is an efficient, clean coal utilization technology. Due to the influence of geological structure and other factors in the formation process, underground coal seam was often heterogeneous, generally accompanied by coal gangue interlayers. Due to the coal gangue being relatively dense and has poor thermal conductivity, it is also rich in metal oxides, it would inevitably affect the pyrolysis characteristics and product distribution during the pyrolysis process of heterogeneous tar-rich coal seam. The pyrolysis characteristics of heterogeneous tar-rich coal seam with different positions and layers of coal gangue interlayer were investigated by the thermogravimetric analyzer, and related kinetic parameters were obtained by the distributed activation energy model (DAEM). Based on the fixed bed tube furnace reactor, the pyrolysis experiments of heterogeneous tar-rich coal seam with different positions and layers of coal gangue interlayer were also carried out, and the pyrolysis products were characterized and analyzed. The thermogravimetric results showed that in the pyrolysis process of heterogeneous tar-rich coal seam, the initial pyrolysis temperature and the temperature corresponding to the maximum weight loss rate shifted to the higher temperature range, and the pyrolysis characteristic index decreased significantly. Under the same conditions, the corresponding pyrolysis characteristic indexes of the upper coal gangue interlayer and 4 layers of coal gangue interlayer were lower, which were 11.69 (10−8·%·min−1·℃−3) and 11.65 (10−8·%·min−1·℃−3), respectively. Compared with homogeneous tar-rich coal seam, pyrolysis activation energies of heterogeneous coal seam generally showed the decreasing trend. Under the conditions of the upper part containing coal gangue interlayer and the upper-and-lower parts containing coal gangue interlayer, the pyrolysis activation energies were higher due to the hindrance of the cover layer of coal gangue to the volatile release, which were 555.88 kJ·mol−1 and 546.66 kJ·mol−1 respectively. The results of fixed bed pyrolysis experiments showed that compared with homogeneous tar-rich coal seam, the tar yield obtained was reduced, the degree of tar lightening was significantly improved, and the proportion of lighter tar was up to 70.00 wt%. The contents of aromatic hydrocarbons and phenolic compounds in tar increased, the contents of aliphatic hydrocarbons and oxygenated compounds decreased significantly, and the maximum reductions were nearly 4.50 wt% and 6.50 wt%, respectively. The gas yield increased, the proportions of H2 and CO2 in the gas increased, and the proportions of CO and CH4 decreased to varying degrees. The tar yields were lower under the conditions of upper gangue and 4 layers gangue, which were 6.53 wt% and 5.81 wt%, respectively, and the degrees of tar lightening were also more significant. From the relationship between pyrolysis characteristic parameters and tar properties of heterogeneous tar-rich coal seam pyrolysis, it was found that the existence of coal gangue interlayer was not conducive to the tar production, but it could promote the lightening of tar and improve the tar quality. Exploring the kinetic characteristics and pyrolysis product distribution of heterogeneous tar-rich coal seam could provide theoretical guidance for the site selection of in-situ underground pyrolysis engineering and the well arrangement.

Effect of Polyethylene Glycol with Different Molecular Weights on the Properties of Mytilaria laosensis Timber

Mytilaria laosensis, a common fast-growing tree species in southern China, boasts excellent growth speed and attractive color and texture. However, due to its short growth cycle and high proportion of juvenile wood, it typically exhibits poor dimensional stability and low strength, which significantly limits its practical applications. This study uses vacuum impregnation to modify M. laosensis wood with polyethylene glycol (PEG), focusing on the effects and mechanisms of PEG with different molecular weights on wood properties. The results indicate that PEG enters the wood cell walls through capillary action and diffusion, forming hydrogen bonds with the free hydroxyl groups on cellulose and hemicellulose, which keeps the cell walls swollen and enhances dimensional stability. Post modification, the dimensional stability of M. laosensis wood improved, with an anti-swelling efficiency ranging from 61.43% to 71.22%, showing an initial increase followed by a decrease with increasing PEG molecular weight. The optimal PEG molecular weight for anti-swelling efficiency was 1500 Da, achieving 71.22%. The flexural modulus of elasticity and flexural strength of the treated wood also first decreased and then increased with increasing PEG molecular weight. Among them, the PEG1000-treated material showed the best performance, with the flexural modulus of elasticity increased by about 29% and the flexural strength increased by about 5% compared to untreated wood. Additionally, PEG, having a higher pyrolysis temperature than wood, raised the initial pyrolysis temperature and maximum pyrolysis rate temperature of M. laosensis wood, thus improving its thermal stability. These findings provide scientific evidence and technical support for the efficient utilization and industrialization of M. laosensis wood, promoting its widespread application and industrial development.

Research on the thermo-hydro-mechanical coupling simulation and deformation spatiotemporal evolution for the entire process of oil shale in-situ mining

The ground surface deformation (GSD) caused by oil shale in-situ mining poses a threat to land resources and human's lives and property. This study, for the first time, conducts a full stratum simulation of the Fuyu oil shale in-situ pyrolysis pilot base, analyzing the evolution characteristics of the temperature field, stress field, and deformation field of the entire stratum profile during the heating and cooling processes of convective heating mining. Considering the changes in the pore structure, thermophysical, and mechanical properties of the stratum, the environmental geological effects of rock deformation during in-situ mining were identified. Simulation results show that after heating, the temperature within 80 cm of the heating well reaches above the initial pyrolysis temperature of 350 °C for oil shale organic matter, and there is a significant stress concentration near the heat source. In the simulation, ground displacement rises in a wave-like manner during heating, quickly subsides after cooling, and finally stabilizes. Eventually, the entire stratum exhibited subsidence, with a subsidence amount of 0.59 cm. The spatiotemporal deformation trend obtained from SBAS-InSAR real-time monitoring results is similar to the simulation results. By comparing the monitoring results with the simulation results, the synergistic deformation mechanism of underground and ground surface co-deformation during in-situ mining of geochemical reactions in the study area was analyzed. The deformation rate is determined by the thermal hysteresis phenomenon and the temperature difference between the heated fluid and the rock layer. This provides scientific support for the geological effect evaluation of oil shale in-situ mining, which helps to improve mining safety and efficiency.

Experimental and simulation study on the thermal decomposition of Xishan coal and the pyrolysis of coal with Na2SO4

ABSTRACT Based on the Thermal Decomposition of Xishan coal Experiments and ReaxFF MD Simulations, the study investigated the processes and product changes in the thermal decomposition of coal and the pyrolysis of coal with Na2SO4. The results indicate that the initial temperature of thermal decomposition of Xishan coal is around 300 °C in experiments and approximately 1600 K in molecular simulations. The addition of Na2SO4 advances the initial pyrolysis temperature and promotes the generation of total number and types of products. Xishan coal pyrolysis generates a large number of small molecular gases and free radicals, and the addition of Na2SO4 promotes the generation of CO, CH4, and H2S, as well as the accumulation of a significant number of free radicals. Free Na mainly affects the evolution of N elements, promoting the formation of N into amino groups, and Na easily combines with sulfur-containing intermediates. Through the extraction of sulfur-containing intermediates and the analysis of the influence of free radicals, it was found that S elements Xishan coal ultimately forms H2S. This study microscopically confirms that in the coal with Na2SO4 system, H2S originates from the hybridised sulfur atoms in the carbon chain and free SO 4 2 − .

Thermal stability of trifluoroiodomethane (R13I1) as an environmentally friendly working fluid for refrigeration and heat pump systems: Investigations and improvement strategies

Trifluoroiodomethane (R13I1) has attracted extensive attention because of its excellent environmental protection performance and flame retardant effect. However, R13I1 has poor thermal stability due to the presence of C-I bonds, which greatly limits its application in refrigeration and heat pump systems. At present, there are few theoretical and experimental studies on the thermal stability of R13I1 and its improvement methods. In order to solve these problems, the thermal stability and pyrolysis mechanism of R13I1 and its mixture with lubricants and stabilizers were investigated using experiments, DFT calculations, and ReaxFF simulations in this study. Firstly, the pyrolysis temperature and pyrolysis products of R13I1 were measured using the reactor method. The initial pyrolysis temperature range of R13I1 was 110–120 °C. C2F6 and I2 are the main pyrolysis products of R13I1. Then, the effect of polyol ester (POE) oil on the thermal stability of R13I1 was analyzed. The results showed that the addition of POE oil significantly promoted the decomposition of R13I1 and the generation of the pyrolysis product CHF3. Circulation systems containing R13I1/POE oil were not suitable for long-term operation at temperatures above 120 °C. The active radicals generated by the pyrolysis of lubricant were the key factor in the deterioration of the thermal stability of R13I1. Finally, a stabilizer addition to the lubricant was used to improve the thermal stability of the R13I1/POE oil, and the optimal stabilizer was determined to be 5 % AN5/0.15 % 2-ethylhexyl glycidyl ether. The thermal stability of R13I1/POE oil before and after the addition of the optimal stabilizer was compared. The experimental results showed that when the reaction temperature was 160 °C, the concentration of R13I1 increased from 98.94 % to 99.85 %, the concentration of CHF3 decreased from 0.89 % to 0.08 %, and the pyrolysis rate of R13I1 was only 3.86 × 10−9 s−1 with the addition of the optimal stabilizer. The optimal stabilizer achieved excellent improvements. This study not only provides basic thermal stability data for R13I1 and its mixtures, but also proposes effective methods to improve the thermal stability, which is of great significance for the safe and reliable application of R13I1 in refrigeration and heat pump systems.

Experimental and reactive molecular dynamics simulation of municipal sludge extract pyrolysis

The sludge extract obtained from degradation solvent extraction exhibits high carbon content, low oxygen content, and ash-free characteristics, making it an ideal fuel due to its excellent performance. In this study, the pyrolysis process of the extract was systematically studied by combining GC-MS experiment with ReaxFF molecular dynamics simulation. The comparison between GC-MS experimental results and ReaxFF-MD simulation shows a high degree of similarity, thus confirming the accuracy of the simulation. This study identified 2000 K as the turning temperature between initial pyrolysis and secondary pyrolysis. In the temperature range of 1200–2000 K, the extract mainly undergoes primary pyrolysis, while in the temperature range of 2000–3000 K, the secondary reaction is remarkable, which is characterized by the further decomposition of tar free radicals and the condensation reaction involving tar free radicals or char. The analysis of typical gas content shows that H2, CO, NH3 and HCN are by-products of the secondary reaction of tar, and there are a lot of reducing gases at high temperature, such as H2, CO and CH4. Finally, the migration patterns of carbon, hydrogen, oxygen and nitrogen are discussed. It is worth noting that hydrogen and nitrogen mainly migrate to the pyrolysis gas phase. This not only laid a foundation for the separation of nitrogen and hydrogen in the future, but also triggered thinking about the potential of “low-carbon emission resource” in future research work. When compared to raw municipal sludge, the initial pyrolysis temperature of municipal sludge extract is much lower, and its pyrolysis process becomes faster. The advantages of reactive gas components indicate that it is more reactive. This variance results in a distinct product distribution and pyrolysis mechanism.

Thermal Behavior and Pyrolysis Kinetics of Mushroom Residue with the Introduction of Waste Plastics.

Co-pyrolysis is considered a very promising technology for the treatment of solid wastes as it can rapidly realize the volume reduction of raw materials and obtain high value-added products. To realize the resource utilization of newly emerging solid wastes in relation to edible fungi residue and waste plastics, mushroom residue (MR), a representative of edible fungi residue, was co-pyrolyzed with waste plastic bags (PE), waste plastic lunch boxes (PP), and waste plastic bottles (PET). The thermal behavior and pyrolysis kinetics of the mixtures were investigated. It was found that the softening of the plastics in the mixtures led to an increase in the initial pyrolysis temperature of MR by 2-27 °C, while the pyrolytic intermediates of MR could greatly promote the decomposition of the plastics, resulting in a decrease in the initial pyrolysis temperatures of PE, PP, and PET in the mixtures by 25, 8, and 16 °C, respectively. The mixture of MR and PE (MR/PE) under different mixture ratios showed good synergies, causing the pyrolysis peaks attributed to MR and PE to both move towards the lower temperature region relative to those of individual samples. The increase in heating rate led to enhanced thermal hysteresis of the reaction between MR and PE. The strength of the interaction between plastics and MR based on mass variation was subject to the order PE > PP > PET. The pyrolysis activation energies of MR, PE, PP, and PET calculated from kinetic analysis were 6.18, 119.05, 84.30, and 74.38 kJ/mol, respectively. The activation energies assigned to MR and plastics were both reduced as plastics were introduced to co-pyrolyze with MR, indicating that MR and plastics have a good interaction in the co-pyrolysis process. This study provides theoretical and experimental guidance for the resource utilization of agricultural solid wastes via thermochemical conversion.

Effects of 1-nitropropane on pyrolysis of n-hexane at atmospheric pressure

In order to investigate the effects of 1-nitropropane (1-NP) on the pyrolysis of n-hexane, the pyrolysis processes of pure n-hexane and n-hexane/1-NP mixture in a jet-stirred reactor (JSR) were experimentally studied at atmospheric pressure with the technique of synchrotron ultraviolet photoionization mass spectrometry (SVUV-PIMS). The pyrolysis experiments of pure n-hexane and n-hexane/1-NP mixture were performed in the temperature ranges of 673–1143 K and 598–1128 K, respectively. The species pools for the pyrolysis of pure n-hexane and n-hexane/1-NP mixture were comprehensively determined and 25 species for pyrolysis of pure n-hexane versus 18 species for pyrolysis of n-hexane/1-NP mixture were identified. Based on the photoionization mass spectra scanned at different photon energies, the mole fraction profiles of all the pyrolysis species were evaluated. The experimental results showed that the initial pyrolysis temperature of n-hexane was observably reduced by 75 K with the addition of 1-NP, and the initial formation temperatures (IFTs) of some major pyrolysis products and important intermediates were correspondingly reduced. A high degree of conformity in the species pools of the pyrolysis of pure n-hexane and n-hexane/1-NP mixture (at both low and atmospheric pressures) was observed. On the basis of the experimental observations, modeling simulations and mechanisms proposed in previous studies, the low-temperature mechanisms for the 1-NP-initiated pyrolysis of n-hexane were discussed. A mechanism, including unimolecular dissociation reactions of 1-NP, radical reactions to produce highly active radicals, H-abstraction reactions of n-hexane and subsequent C-C bond dissociation reactions of hexyl radicals, was proposed.

Mechanism research on the application of liquid film microencapsulation technology based on natural lotion in strengthening recycled bio‐composite wallpaper material

AbstractLow‐carbon technology is currently one of the main research directions in sustainable research. The purpose of this research is to explore environmentally friendly low‐carbon technologies to apply NL and wastes to the development of bio‐composite. This research can not only inhibit the release of toxic atmosphere from composite wallpaper materials but also propose new perspective for recycling several bulk wastes such as agricultural waste, waste plastics, and waste cooking oil. This study not only conducted an exploratory research on the degree of filling load from a vertical perspective but also conducted comparative experiments to clarify the strengthening effect of NL in a horizontal perspective. Several valuable findings are obtained through the analysis of several measurements such as mechanical performance and scanning electron microscope (SEM) morphology. The heat transfer effect between components inside the bio‐composite is enhanced by the action of NL. A better heat transfer effect can prevent heat from accumulating in local areas of bio‐composite, resulting in an increase in the overall initial pyrolysis temperature of thermogravimetric analysis (TGA) curve. It is found through experiments that when the biomass filler is excessive, the mechanical performance of the sample sharply decreased. These negative phenomena are presented in the specific form of voids and aggregates in the internal structure of bio‐composite from a microscopic perspective. Comprehensive analysis manifested that NL can suppress the negative effect of filler agglomeration and strengthen the filler/matrix interface bonding. The research also found that the type of biomass filler can affect the actual effect of NL. These findings have certain academic significance and can promote the further development of sustainable research on diversified recycle of wastes.

Investigation on pyrolysis mechanism and emission characteristics of CO2, NOx and SO2 during co-pyrolysis of coal gangue and sodium alginate/sodium carboxymethylcellulose/chitosan/guar gum

Biomass materials are potential to promote coal gangue pyrolysis process. This study investigates the effects of four biomass materials derived from different sources, namely sodium alginate (SA), sodium carboxymethyl cellulose (CMC), chitosan (CS), and guar gum (GG), on the pyrolysis of coal gangue (CG) in a nitrogen atmosphere. Thermal gravimetric analysis coupled with mass spectrometry (TG-MS) was used to analyze the thermal behaviors and emission characteristics of CO2, NOx, and SO2 during the co-pyrolysis process of CG and the four different biomaterial blends, which were mixed in varying ratios. The study investigated that the interactions between the various biomaterials and CG by calculating and comparing pyrolysis parameters, such as the comprehensive pyrolysis index (CPI) of CG and the blends. Additionally, a kinetic analysis using the Kissinger-Akahira-Sunose (KAS) method was conducted to reveal the co-pyrolysis mechanism. The thermal gravity analysis results illustrated that SA, CMC, CS and GG were all conducive to enhancing CG pyrolysis. As the biomass content in the blends increases, the sample experiences greater mass loss, while the initial pyrolysis temperature and residual mass ratio decrease. This suggests the presence of biomass enables more complete pyrolysis reactions of CG. Among the four biomass materials, GG had the most positive effect on promoting CG pyrolysis, followed by CS and SA, with CMC having the least effect. The kinetic analysis showed that the primary step of each blend sample generally conformed to the first-order kinetic model. The calculated activation energies of blends groups were lower than that of CG pyrolysis, verifying the positive effects of the four biomaterials on CG pyrolysis. However, the interaction mechanism varied in different pyrolysis stages for each type of biomass material. Gas emission analysis indicated that the emission of CO2, NOx and SO2 in blends groups were significantly lower than that of CG pyrolysis. This implies that the addition of the four biomaterials could effectively control the emission of carbon dioxide and pollutants during CG pyrolysis.

Study on pyrolysis characteristics, kinetics and thermodynamics of waste tires catalytic pyrolysis with low-cost catalysts

As a non-biodegradable solid waste, waste tires (WTs) have adverse effects on the ecological environment and human health. Waste tires are a good source of energy. In order to reduce the energy consumption of waste tires pyrolysis, this paper explores the influence of three low-cost catalysts on the catalytic effect of waste tires. The results of thermogravimetric experiments show that the use of spent FCC catalyst (FCC), red mud (Rm) and fly ash (Fa) during pyrolysis is beneficial to reducing the initial pyrolysis temperature of WTs. The kinetic calculation results show that compared with the direct pyrolysis of WTs, the average activation energy of WTs catalyzed by red mud and fly ash is reduced by about 9.5 kJ/mol and 7.8 kJ/mol, respectively. The average pre-exponential factor (lnA) decreased by about 1.3 min−1 and 1.4 min−1, respectively. The thermodynamic calculation results show that the endothermic reaction occurs in both the pyrolysis and catalytic pyrolysis of WTs, and the pyrolysis process cannot be carried out spontaneously. The pyrolysis reaction process of waste tires can be characterized by the combination of kinetics and thermodynamics, which provides parameters for determining the relevant process conditions for the industrialization of catalytic pyrolysis of waste tires.

Effects of ZSM-5 zeolite on pyrolysis of polystyrene: from stabilizing to catalyzing.

Nonisothermal pyrolysis measurements of polystyrene (PS)/ZSM-5 zeolite hybrids are conducted in N2 and thermogravimetric results have been kinetically analyzed with different isoconversional methods. Experimental results show that the addition of 5 and 10 wt.% ZSM-5 zeolite has increased the initial pyrolysis temperature of PS while the addition of 20 and 30 wt.% ZSM-5 zeolite can significantly decrease the initial pyrolysis temperature of PS. Elevated activation energy is resulted by adding low zeolite amount whereas reduced activation energy is obtained by adding high ZSM-5 amounts. The effect of zeolite ZSM-5 on PS pyrolysis can thus be observed to transfer from stabilizing to catalyzing. Furthermore, the pyrolysis mechanism functions of PS/zeolite hybrids are determined by integrating the master plots method with a new compensation effect method, and the most appropriate reaction models are found to be F0.92, F0.85, F0.56 and A1.32 for describing the pyrolysis of the PS/ZSM-5 hybrids with a zeolite loading of 5, 10, 20 and 30 wt.%, respectively. With the kinetic parameters thus available, the temperature-dependent mass conversion curves have been recast, leading to satisfactory simulations for PS/ZSM-5 hybrids.

Comparing four kinds of lignocellulosic biomass for the performance of fiber/PHB/PBS bio-composites

A new class of bio-composites was developed by utilizing four kinds of lignocellulosic biomass fiber (bagasse, bamboo, rice husk, and rice straw) as filling fibers. Poly-β-hydroxybutyrate (PHB) and poly(butylene succinate) (PBS) in a mixture ratio of 7:3 were used as matrix materials with hot-press molding. The performance of the resulting composites was evaluated by compositional analyses, mechanical analysis, Fourier transform infrared (FTIR) spectroscopy, thermogravimetry, and morphological analysis. The interfacial adhesion, thermal stability, and comprehensive mechanical properties of the alkali treated bamboo/PHB/PBS composite were highest among the four bio-composites. The bending strength, tensile strength, and impact strength for alkali treated bamboo/PHB/PBS composite was 19.82 MPa, 12.97 MPa, and 4.30 kJ/m2, respectively. The thermal stability for NaOH modified bamboo/PHB/PBS composite was slightly superior to the other three composites, with the initial pyrolysis temperature of 248 °C, moderate pyrolysis speed, and the amount of pyrolysis residue (5.81%). The results showed the suitability of biomass fiber and biodegradable polymer for producing environmentally friendly composite materials.

Glucose-Histidine Heyns compound: Preparation, characterization and fragrance enhancement

N-(2-Deoxy-D-glucos-2-yl)-L-histidine (Glu-His), one of Heyns rearrangement products (HRPs), was prepared by condensation, dehydration and rearrangement using l-Histidine and d-Fructose as raw materials with methanol as solvent. The response surface method (RSM) was used to improve yield of product and the optimal reaction condition was as following: the original ratio of Fru:His was 1.2:1 and the temperature and time of reaction was 73.2 °C and 4.7 h, and the yield of final product was 74.10% with the purity of 99.7%. The structure of product was identified by IR, NMR and conformed as C12H19N3O7 (317.1 Da) by high-resolution mass spectrometry (HRMS) and UPLC-MS/MS. The pyrolysis behavior of Glu-His showed that its initial pyrolysis temperature was 145.2 °C and the total weight loss reached 70.61% at 800 °C. The number of pyrolysis products increased with the increase of temperature, and the main pyrolysis products were pyrans, furans, pyrazines, pyrroles, pyridines, indoles and etc. with burnt-sweet, baking, nutty, sweet and floral aroma features. At last, the fragrance enhancement effect of Glu-His in the preparation of reconstructed tobacco stem (RTS) was investigated and the result of sensory evaluation showed that the smoke of RTS cigarettes brought about more sweet and moist, less irritation, better flavor and comfort with the addition of Glu-His (0.25%, w/w).

Experimental and theorical study on the pyrolysis behaviors of 2,3,3,3-tetrafluroropropene

The pyrolysis behaviors of 2,3,3,3-tetrafluroropropene (R1234yf) had been first studied in a flow reactor pyrolysis apparatus coupled with the synchrotron vacuum ultraviolet photoionization mass spectrometry and gas chromatography. The pyrolysis temperature, reaction products and intermediates were measured at atmospheric pressure. The experimental results revealed that the initial pyrolysis temperature of R1234yf was 1040K and the thermal decomposition was accelerated with the increase of temperature. It was found that the pyrolysis reaction of R1234yf will be replaced by a self-polymerization reaction at 1160 K. In order to explore the chemical process of R1234yf pyrolysis, a detailed kinetic simulation was performed and compared with experimental results. The calculated results indicated that the unimolecular decomposition paths took a dominant role in the whole pyrolysis processes. The intermediates of C2H2, C2HF, CF2, CHF3, CF4 and CF3CF3 were detected in the pyrolysis experiments. Moreover, the distribution characteristics and sensitivity analysis of the vital fluorinated species of CF2, C2H2, CF4, CF3CF3 and HF were discussed. All of these founding could provide reliable data for the development of pyrolysis models and guidance for the use of R1234yf in the refrigeration system.

Insight into pyrolysis mechanism of plastic waste with C-O/C-N bonds in the backbone

Pyrolysis is an important method for efficiently recovering plastic monomers, fuels and chemicals from plastic waste. The depolymerization of the backbone structure of plastic waste is a key step of the pyrolysis process. Currently, researches on the pyrolysis mechanism of plastics with C-O/C-N bonds in the backbone are still not sufficiently in-depth and also lack systematic and comprehensive investigation. Therefore, this study for the first time comprehensively investigated both macroscopic and microscopic pyrolysis processes of plastics with C-O/C-N bonds in the backbone, and evaluated the difficulty of breaking different backbone linkages via bond dissociation energy (BDE) obtained by density functional theory (DFT) calculations to deeply reveal the pyrolysis mechanism. The results indicated that polyethylene terephthalate (PET) had a higher initial pyrolysis temperature and its thermal stability was slightly stronger than nylon 6. The backbone of PET was mainly decomposed via the cleavage of Cα-O on the alkyl side, while the degradation of nylon 6 backbone began with NH2 groups at the end of the backbone. The pyrolysis products of PET were mainly derived from the small molecular fragments, which were generated by the degradation of the backbone through the cleavage of CO bonds or CC bonds, while the pyrolysis products of nylon 6 were always dominated by caprolactam. In addition, based on the results of DFT calculations, it could be inferred that the cleavage of CC bond in PET backbone and the cleavage of its adjacent Cα-O were most likely to occur, which followed a competitive reaction mechanism. However, in pyrolysis of nylon 6, the conversion to caprolactam was mainly via the concerted reaction of amide CN bonds. Compared with the concerted cleavage of amide CN bond, the cleavage of CC bond in the backbone of nylon 6 was not predominant.

Experimental study on n-hexane pyrolysis initiated by 1-nitropropane in a low-pressure flow reactor

In order to investigate the species pool and primary channels of initiated pyrolysis of n-hexane, the low-pressure (30 Torr, 4.0 kPa) flow reactor pyrolysis of n-hexane initiated by 5% 1-nitropropane (1-NP) was studied experimentally in a wide range of temperature from 623 K to 1223 K. Combined with synchrotron vacuum ultraviolet (SVUV) photoionization mass spectra scanned at photon energies ranging from 9.0 to 14.7 eV and near-threshold photoionization efficiency (PIE) spectra, 29 pyrolysis species, covering C1–C6 hydrocarbons and several pyrolysis species containing O or N atoms, were identified. Based on the ion signal intensities of the visible peaks in the mass spectra, the mole fraction profiles of all the experimental species were evaluated. The experimental results suggested that the initial pyrolysis temperature of n-hexane was reduced by approximately 275–325 K. On the basis of the mole fraction profiles and the initial formation temperatures reported in this work and rate coefficients proposed in previous studies, the 1-NP-initiated pyrolysis mechanisms of n-hexane were discussed. It was suggested that n-hexane was dominantly consumed by the H-abstraction reactions by the attack of OH radical in this work. The 1-NP-initiated pyrolysis of n-hexane mainly proceeded via reactions to produce C3H6 + C3H7, or 1-C4H8 + C2H5, or 1-C5H10 + CH3.

Catalytic pyrolysis of oil shale using tailored Cu@zeolite catalyst and molecular dynamic simulation

This study synthesized a novel Cu@4 A zeolite nano-catalyst, which exhibited excellent catalytic pyrolysis performance on oil shale. The catalytic pyrolysis behaviors of oil shale were investigated, results show the initial pyrolysis temperature of organics decreased from 410 °C to 360 °C after catalytic treatment, and the activation energy declined from 190.73 to 147.95 kJ/mol. The oil and gas yields increased by 7.61% and 19.69% after catalysis treatment by Cu@4 A, respectively; the yields of H2 and ethylene catalyzed by Cu@4 A zeolite climbed to 15% and 21%. Cu@4 A shows a prominent selectivity on light alkanes and alkenes compared with metal catalysts. The configurations of hydrocarbons in nano-pore were investigated by Molecular Dynamics simulations, the first density peak of C3H6 declined by 68.3% after catalyzed by Cu@4 A at a temperature of 573 K. The interaction energy of hydrocarbon would decrease when the system temperature increases. Finally, the catalytic mechanism was elucidated, kerogen would decompose into macromolecule aromatic hydrocarbons via the β-cleavage of carbenium ions over the acidic sites of the prepared catalyst, then followed by the dehydrocyclization, oligomerization, and aromatization.