Chain Breaking Research Articles

Theoretical mechanism behind the higher efficiency of O than OH radicals in polypropylene surface modification: a molecular dynamics study

O and OH radicals are the most important reactive oxygen species in the plasma treatment of polymer surfaces. In our previous studies, we found that the modification efficiency of polypropylene (PP) surface by O radicals was approximately four times higher than that by OH radicals. This observation contrasts with the well-established fact that the chemical reactivity of O radicals with saturated hydrocarbons (C n H2(n + 1)) is 50–60 times lower than that of OH radicals. In this study, classical molecular dynamics simulations with a reactive force field were used to explain this contradiction. The results showed that the surface modification of PP by O or OH radicals is a Langmuir–Hinshelwood process. Both O and OH radicals penetrated the bulk PP, that is, physical adsorption occurred before the chemical reactions. The penetration depth of O radicals was greater than that of OH radicals. Compared to the case of OH radicals, alkoxy radicals (RO·) are more readily formed upon the interactions of the PP surface with O radicals. Furthermore, the β-scission (splitting of the C–C bonds) of RO· can be accelerated by the physically adsorbed O radicals, leading to earlier breakage of PP chains. The improved efficiency of the surface modification of PP upon exposure to O radicals, in contrast to that of OH radicals, can be attributed to the differences in the above three crucial processes. These findings are significant for modelling and understanding the mechanisms of plasma-polymer surface treatment at the atomic and molecular levels.

Detection model for key nodes of manufacturing industry chain stability under complex networks: a naval architecture and marine engineering equipment industry chain example

PurposeCurrently, China’s manufacturing industry chain still faces the danger of chain breakage due to the persistent “lack of technology” issue. The definition and detection of key nodes in the industry chain are significant to the enhancement of the stability of the industry chain. Therefore, detecting the key nodes in the manufacturing industry chain is necessary.Design/methodology/approachA complex network based on the links amongst listed manufacturing enterprises is built, and the authors analyse the network’s basic characteristics and vulnerability, taking into account the impact of scientific and technological innovation on the stability of the industry chain.FindingsIt is found that the high structural characteristic of midstream nodes in the naval architecture and marine engineering equipment industry chain determines their importance to stability, and the key status of upstream nodes is reflected in the weakness of technological innovation. The upstream nodes should focus on improving their independent innovation and R&D capability, whilst the midstream nodes should maintain a close supply–demand cooperation relationship.Originality/valueThe key node detection model for industry chain stability is constructed by considering various factors from the perspective of network and technological innovation. Empirical study is conducted to verify effectiveness of proposed method.

Mechanical strength changes of combustible municipal solid waste components during their early pyrolysis stage and mechanism analysis.

Implementation of municipal solid waste (MSW) source segregation leads to a more convenient recycle of combustible MSW components. Textiles, plastics and papers are commonly available combustible components in MSW. Their shredding is conducive to resources recovery. But these components usually have high tensile strengths and are difficult to shred. To understand their mechanical strength changes in their early pyrolysis stage will help to address this problem. In this study, a universal electronic testing machine was used to determine the breaking strengths of the materials including cotton towel, polyethylene glycol terephthalate (PET), ivory board (IB), kraft paper (KP) and wool scarf in the temperature range of 30-250°C under N2 atmosphere, and the mechanisms of their strength changes were explored. The reaction force field molecular dynamics (ReaxFF-MD) simulation was used to explain the decomposition behaviours of different sugar groups of hemicellulose in cotton and paper and the change of van der Waals energy of wool during their early pyrolysis stages. The results showed that breaking strengths of all the combustible MSW components reduced as the temperature increased. The breaking strength of PET was found to have the highest descent rate with increasing temperature, then the descent rates of wool and cotton came as the second and third, respectively. Compared with cotton, the breaking strengths of KP and IB decreased more slowly. As the temperature increased, the breaking strength of cotton reduced mainly due to the decomposition of the glucuronic acid in hemicellulose, and the reduction was characterized by CO2 release. The breaking strength reduction of PET was caused by its molecular chain being relaxed. The breaking strength reduction of wool was firstly caused by the decrease in the van der Waals energy between its molecules, and then caused by molecular chain breaking. In addition, in order to understand the influence of material size on the breaking strength change during thermal treatment, the breaking strengths of cotton yarn bundles were correlated with their yarn number and temperature. This study lays the foundation for understanding changes in mechanical strengths of combustible MSW components during their early pyrolysis stage.

RETRACTED: Construction of self-repairing polyethersulfone membrane with high density hydrophilic microregions by two dimensional restricted channels for enhanced dyes/salts selective separation

Based on the dye/salts separation efficiency and membrane injury caused by serious pollution of dye/salts wastewater, this study constructed a 2D tight ultrafiltration membrane that could both solve the membrane injury problem and improve the dye/salts separation efficiency, the compatibility of good self-healing performance and penetration performance by 2D material magnesium-aluminum Layered double hydroxide (MgAl-LDH). The self-repairing of physical injury was achieved through the swelling effect of AMPS-PAN, this property was proved by permeate flux, the retention performance of salts in dye/salts solution, the comparison of scanning electron microscope (SEM), and the mechanical strength after physical injury. The healing of chemical injury occured through the reaction of CC and polyethersulfone chain breakage, which was confirmed by X-ray photoelectron spectroscopy (XPS), permeate flux, the retention performance of salts in dye/salts solution, and mechanical property. The high separation efficiency of dye/salts was achieved through 2D material MgAl-LDH, which was proved by separation selectivity ɑ. The compatibility of good self-healing performance and penetration performance was obtained by 2D material MgAl-LDH, which was proved by the penetration and self-healing performance. Morever, the membrane illustrated excellent both permeability and dye/sals separation efficiency, just like the permeate flux, the retention performance of sodium sulfate in methyl blue/sodium sulfate solution, the retention performance of Na2SO4 in methyl blue/Na2SO4 solution, the retention rate of methyl blue were 99.1 L/m2h, 12.5%, 7.9%, 97.7%, respectively. The results of pollution index and contact angle also proved that the membrane had anti-pollution performance.

Shock and spallation behavior of ultrahigh molecular weight polyethylene

We investigate dynamic compression and fracture of ultra-high molecular weight polyethylene (UHMWPE) with plate impact experiments, high-speed velocimetry, and postmortem X-ray computed tomography. The Hugoniot equation of state of UHMWPE up to peak shock stress of ∼2.0 GPa is obtained via reverse impact. Spall strength and corresponding tensile strain rates are determined via symmetric impact. With increasing impact velocity, spall strength is nearly a constant (∼70 MPa) up at first, and then decreases continuously as a result of competition between increasing tensile strain rate, shock heating and strain softening; the damage degree increases first and then decreases rapidly at the expense of more damage nucleation sites. The void size distributions follow a power law. The small voids are closer to spheres and voids/cracks becomes flatter as void volume increases, likely because of the rearrangement and breakage of linear polymer chains of UHMWPE.

Improving the interfacial stability of ultrahigh-nickel cathodes with PEO-based electrolytes by targeted chemical reactions.

Benefiting from high energy density of ultrahigh-nickel cathode materials and good safety of PEO-based electrolytes, PEO-based ultrahigh-nickel solid-state lithium batteries (SLMBs) are considered to be new-generation energy storage devices. However, the incompatibility of ultrahigh-nickel cathode materials and PEO-based electrolytes is the main challenge due to serious interfacial side reactions. Therefore, the modification of the cathode/electrolyte interface is crucial. Herein, the residual lithium on the surface of LiNi0.9Co0.06Mn0.04O2 is utilized to construct an interfacial coating layer by reacting with H3BO3. The in situ formed xLi2O-B2O3 coating layer (LBO1-NCM) with high ionic conductivity can be regulated with different crystal structures during the sintering process. Besides, an all-solid-state three-electrode cell is fabricated, which verifies that the xLi2O-B2O3 coating can effectively stabilize the interface. Astonishingly, uneven Li anode deposition is observed in SLMBs, which is caused by the breakage of PEO molecular chains due to the strong oxidation of the cathode, while this crosstalk is also suppressed by the xLi2O-B2O3 coating layer. Consequently, Li|PEO|LBO1-NCM achieves a substantially improved electrochemical performance, exhibiting 90.5% of capacity retention after 100 cycles for the coin cell and 80.3% of capacity retention after 200 cycles for the pouch cell. Apparently, the targeted modification of interfaces should be paid as much attention as electrolyte optimization in SLMBs.

English

The use of hydrogen energy is considered to be an alternative energy that provides renewable fuel energy solutions. The production of bio-hydrogen with basic materials such as organic waste and industrial waste is easy to implement and seems to be promising as an energy source in the future. One method that can be done to produce hydrogen is a photocatalyst. To increase hydrogen production, photocatalysts were selected using activated carbon made from biomaterials, namely using onion peels. In onion peel, aromatic compounds / aromatic rings with hydroxyl functional groups are the main components of activated carbon to support the photocatalyst process. The method used in this study is using experimental methods involving several research variables including independent variables are the mass of activated carbon 2.7 and 16 grams and variations in light irradiation, namely purple, green, yellow and without light. The control variables include the length of light exposure time of 30 minutes, the volume of the solution is 100 mL and the dimensions of the catalyst are 60-200 mesh. The results stated that the mass variation of 16 grams with purple light irradiation was able to produce the highest hydrogen worth 749.18 μmol g-1. This result is influenced by the electrons contained in the aromatic ring being delocalized and causing electrons to move freely energetically throughout the structure, giving rise to properties such as conductivity. The electron delocalization process that occurs in activated carbon causes electrons to move energetically, thus affecting the O-H covalent bond found in H2SO4 solution and triggering the weakening of hydrogen bonds in acidic solutions. The reaction caused by the delocalization process takes place continuously, triggering the breaking of the hydrogen chain

Installing a Single Monomer within Acrylic Polymers Using Photoredox Catalysis.

Incorporating exactly one monomer at a defined position during a chain polymerization is exceptionally challenging due to the statistical nature of monomer addition. Herein, photoinduced electron/energy transfer (PET) enables the incorporation of exactly one vinyl ether into polyacrylates synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization. Near-quantitative addition (>96%) of a single vinyl ether is achieved while retaining >99% of the thiocarbonylthio chain ends. Kinetic studies reveal that performing the reactions at 2 °C limits unwanted chain breaking events. Finally, the syntheses of diblock copolymers are reported where molecular weights and dispersities are well-controlled on either side of the vinyl ether. Overall, this report introduces an approach to access acrylic copolymers containing exactly one chemical handle at a defined position, enabling novel macromolecular architectures to probe structure-function properties, introduce sites for de/reconstruction, store information, etc.

Application of Solvent-Assisted Dual-Network Hydrogel in Water-Based Drilling Fluid for Lost Circulation Treatment in Fractured Formation.

During oil and gas well construction, lost circulation caused substantial nonoperation time and extra costs, and hydrogel, resilient and environmentally friendly, was one of the major types of material for lost circulation treatment. To migrate the weak bonding and hydrothermal degradation of conventional single network hydrogels, dual network (DN) hydrogel was prepared and immersed in solvents of polyethylene glycol (PEG), ethylene glycol, and glycerol. The swelling of DN gels at different temperatures was studied with water content and swelling rate tests, and the gel structural and morphology was characterized with attenuated total reflectance infrared spectroscopy (ATR-IR) and scanning electron microscopy test. Then, the compression test and fracture plugging performance test were conducted to study the strength of the gel. The results show that compared to those in ethylene glycol and glycerin, DN gel after immersion in PEG (DN-PEG) exhibits greater compression strength and better plugging performance even at high temperatures. The compression strength of DN-PEG was twice that of DN hydrogel before immersion, and its fracture plug breaking pressure can reach over 10.0 MPa. After undergoing hydrothermal treatment at 90 °C, the compression strength of the DN-PEG was nearly 20 times that of the DN hydrogel, and the fracture plug breaking pressure was still 2.81 MPa. According to ATR-IR spectroscopy, as the molecular weight of the solvent increases, more hydroxyl groups in the PEG have better ability to bind with hydrogen bonds, which greatly inhibits the swelling and polymer chain breakage, thereby reducing hydrothermal degradation in the strength of the dual-network hydrogel. Our work proposed an effective method to reduce the degradation of hydrogel in water at high temperature, and the prepared DN-PEG hydrogel was a promising material for lost circulation treatments in fractured formation.

Antioxidant effectiveness between mechanisms of “Chain breaking antioxidant” and “Termination enhancing antioxidant” in a lipid model with essential oils

Lipid oxidation in foods is delayed through the use of antioxidants. The aim was to determine the oxidative stability of high oleic peanut oil and the effect of adding oregano and hop essential oils, with phenolic and no-phenolic terpenes, under 150 °C. The peanut oil was enriched with oregano and hop essential oils (0.02%). These treatments were compared with sunflower oil, high oleic peanut oil, and high oleic peanut oil with BHT (0.02%). Treatments were exposed at 150 °C for 8 h. Peroxide value (PV), conjugated dienes, and volatile oxidation compounds were measured. High oleic peanut oil was more stable than sunflower oil. Peanut oil obtained 61.9% less PV than sunflower oil. Oregano and hop essential oils protected the peanut oil; the peroxide values were 14.9 ± 0.4 and 14.6 ± 0.2 meq O2 kg−1 at 8 h, respectively. Both “Chain Breaking Antioxidant” And “Termination Enhancing Antioxidant” had similar antioxidant effects.

Durability of glass fiber reinforced thermoplastic polypropylene composite bars under the coupling effect of seawater and sea sand concrete environment and sustained bending

AbstractThe long‐term interfacial shear strength (IFSS) and flexural strength of GFPP bars under the coupling effect of bending and immersion in the simulated seawater and sea sand concrete (SWSC) solution were studied by an acceleration experiment. Three temperatures and three bending stress levels (0%, 9.8%, and 29.4% of the maximum flexural strain of GFPP bars) were used to accelerate the experiment. Results indicate that the degradation of mechanical properties of GFPP bars is relatively sensitive to the immersion temperature. Low bending stress did not accelerate the degradation of GFPP bars compared with unbent GFPP bars while high bending stress dramatically accelerated the degradation. Microscopic tests found there is corrosion of glass fibers and debonding between glass fibers and polypropylene but no obvious chain breaks of polypropylene occurred. Based on the Arrhenius theory, long‐term stable retention rates of the IFSS of GFPP bars with zero and low bending stress immersed in the simulated SWSC solution are 42.4% and 52.3%.Highlights Low‐stressed GFPP bars degraded similarly or even slower than unbent GFPP bars. GFPP bars degraded mainly due to interfacial debonding and fiber corrosion. Long‐term IFSS of GFPP bars under a coupling effect was predicted.

Failure behavior of dielectric films for peaking capacitor subjected to surface flashover under nanosecond pulses

The flashover failure and damage of polypropylene (PP) and polyester (PET) films under nanosecond current pulses were experimentally investigated. A nanosecond pulse current test platform was established to study the flashover characteristics, performance degradation, and structural damage of dielectric films under repeated nanosecond current pulses. The accumulation and emission of surface charge influenced by field distortion and trap distribution were analyzed to clarify the mechanism by which the flashover voltage increases linearly with gas pressure at low pressure and saturates at high pressure. The significant effects of pulse energy, gas pressure, and discharge gap on film damage behavior were investigated. The damage pattern of PP and PET films includes surface deformation, reduced flash-voltage tolerance, molecular chain breakage, and group shedding. The damage of PP films is manifested as fine furrows, while PET corresponds to mountainous bumps. With the increasing number of discharges, the breakdown voltage of PP films decreased significantly, while the flash tolerance performance of PET films was more stable. Under the conditions of high pulse current amplitude, small discharge gap, and low air pressure, the damage degree of the film intensifies, which is characterized by severe destruction to the molecular structure and a significant decrease in flashover withstand voltage. Polymer films, flashover, nanosecond current pulses; performance degradation; microstructural damage.

The role of elastic instability on the self-assembly of particle chains in simple shear flow

Flow-induced self-assembly (FISA) is the phenomena of particle chaining in viscoelastic fluids while experiencing shear flow. FISA has a large number of applications across many fields including materials science, food processing, and biomedical engineering. Nonetheless, this phenomena is currently not fully understood and little has been done in literature so far to investigate the possible effects of the shear-induced elastic instability. In this work, a bespoke cone and plate shear cell is used to provide new insights on the FISA dynamics. In particular, we have fine-tuned the applied shear rates to investigate the chaining phenomenon of micrometer-sized spherical particles suspended into a viscoelastic fluid characterized by a distinct onset of elastic instability. This has allowed us to reveal three phenomena never reported in literature before, i.e.,: (I) the onset of the elastic instability is strongly correlated with an enhancement of FISA; (II) particle chains break apart when a constant shear is applied for “sufficiently” long-time (i.e., much longer than the fluids' longest relaxation time). This latter point correlates well with the outcomes of parallel superposition shear measurements, which (III) reveal a fading of the elastic component of the suspending fluid during continuous shear flows.

Structure–property evolution of poly(ethylene terephthalate)/poly(trimethylene terephthalate) side‐by‐side self‐crimp filament

AbstractTo investigate the microstructure and mechanical properties of self‐crimping two‐component side‐by‐side bicomponent filament, this paper focuses on systematically investigating the structure–property evolution of poly(ethylene terephthalate) (PET)/poly(trimethylene terephthalate) (PTT) side‐by‐side bicomponent filament prepared via melt spinning with various component ratios, drawing and heating treatment. The investigation was operated upon the combination of morphology analysis, thermal analysis, crystallization, and orientation analysis. The variation of cross section and curl‐morphology, crystallization, and microstructures mainly containing lamellar and microfibrillar crystals as well as their effects on the mechanical and self‐crimping properties were discussed. As the draft ratio (DR) increases, the crystallinity, sonic orientation factor, tensile strength, and crimp‐recovery rate of the filaments were increased. The sonic orientation factor in the crystalline region decreases from 0.923 to 0.777 but increases from 0.677 to 0.903 in the amorphous region. In contrast to the variation of the DR, heating temperature has a limited effect on the tensile strength of the PET/PTT hybrid filaments. Crimp‐recovery rate, however, first increases to 11.8 and then decreases to 9.8 with an increasing heating temperature from 144 to 168°C. Most of these behaviors have been attributed to changes in the ratio of contractile stress for both PTT and PET components, originating from microstructural evolution in hybrid filaments, including crystal growth, breakage, deflection, and deformation of chains along the axial direction. As a summary, an interpretive diagrammatic sketch has been proposed to clarify the structure–property relationships of the commercial PET/PTT filaments.

Nanoscale Insights into the Mechanical Behavior of Interfacial Composite Structures between Calcium Silicate Hydrate/Calcium Hydroxide and Silica

The failure of the interfacial transition zone has been identified as the primary cause of damage and deterioration in cement-based materials. To further understand the interfacial failure mechanism, interfacial composite structures between the main hydration products of ordinary Portland cement (OPC), calcium silicate hydrate (CSH) and calcium hydroxide (Ca(OH)2), and silica (SiO2) were constructed while considering their anisotropy. Afterwards, uniaxial tensile tests were conducted using molecular dynamics (MD) simulations. Our results showed that the interfacial zones (IZs) of interfacial composite structures tended to have relatively lower densities than those of the bulk, and the anisotropy of the hydration products had almost no effect on the IZ being a low-density zone. Interfacial composite structures with different configurations exhibited diverse nanomechanical behaviors in terms of their ultimate strength, stress–strain relationship and fracture evaluation. A higher strain rate contributed to a higher ultimate strength and a more prolonged decline in the residual strength. In the interfacial composite structures, both CSH and Ca(OH)2 exhibited ruptures of the Ca-O bond as the primary atomic pair during the tensile process. The plastic damage characteristics of the interfacial composite structures during the tensile process were assessed by analyzing the normalized number of broken Ca-O bonds, which also aligned with the atomic chain break characteristics evident in the per-atom stress map.

Research on key risk chain mining method for urban rail transit operations: A new approach to risk management

To ensure the safety of urban rail transit operations and uncover the transmission dynamics of risk sources, a key risk chain mining method for urban rail transit operation is proposed. Firstly, the H-Apriori association rule algorithm is proposed for the characteristics of low frequency but high riskiness of high hazard degree risk sources in urban rail transit operation, which adds a new hazard degree evaluation index to the traditional Apriori algorithm and couples with support degree two-dimensionally to mine the strong association rules among risk sources. Secondly, we construct a weighted risk network with risk sources as network nodes and strong association rules as network edges, and propose a key risk chain mining method for urban rail transit operation based on path search theory to mine key risk chains from the weighted risk network. Finally, using the actual urban rail transit operation data of a city in China as an example, a total of 17 key risk chains are mined, and then 5 key risk sources and 8 key chain break locations are obtained by riskiness and frequency analysis of key risk chains, and control plans are proposed. The research outcomes introduce a novel approach to mining risk chains in urban rail transit operations, shedding light on the propagation mechanisms, triggering probabilities, and degrees of unsafety associated with risk sources. The results not only provide theoretical support but also offer methodological guidance for pinpointing locations of risk chain breaks and refining the control of risk sources.

Validación de la conservación de la cadena de frío durante la distribución de mezclas de nutrición parenteral

ObjectiveThis study aims to demonstrate the suitability of the process used to condition the extemporaneous mixtures of parenteral nutrition for distribution, considering the objective of preserving the cold chain during transport until it reaches the patient, necessary to ensure stability, effectiveness and safety of these mixtures. MethodConcurrent validation, design and implementation of a protocol for evaluating the process of packaging and distribution of MNPE developed by a pharmaceutical laboratory. Running tests, according to predefined acceptance criteria. It is performed twice, in summer and on routes that require longer transfer time. Evaluation of conservation of temperature by monitoring the internal temperature values of each type of packaging, recorded by data loggers calibrated equipment. ResultsThe different tests meet the established criteria. The collected data ensure the maintenance of the cold chain for longer than the transfer time to the most distant points. ConclusionsThis study establishes the suitability of the processes to maintaining the cold chain for transfer from the laboratory to the patient pharmacist. Whereas the breaking of cold chain can cause changes of compatibility and stability of parenteral nutrition and failures nutritional support, this study contributes to patient safety, one of the relevant dimensions of quality of care the health.

Investigation on bio-oil pyrolysis with Ni/Al2O3 blending: Influence of the blended catalyst on coke formation

Bio-oil can be converted into syngas, chemicals, and carbon materials via thermochemical and/or catalytic conversion routes. However, coking remains a significant challenge during the heating of bio-oil. In this study, we investigated the influence of pre-blending Ni/Al2O3 and bio-oil in an in-situ catalytic pyrolysis process on the coking behaviours of bio-oil. Our results indicate that the presence of Ni/Al2O3 significantly reduces coke yield and increases gas yield (for example, by a 14.2 % reduction in coke and a 44.1 % increase in gas at 700 °C). This is attributed to the suppression of the cross-linking reactions responsible for coke formation through the pre-elimination of O-containing groups into CO and CO2. Additionally, pre-blending of Ni/Al2O3 is highly desirable for transforming or stabilising the highly reactive substances in the early pyrolysis stage of bio-oil, minimising their tendency to polymerise. Furthermore, the presence of Ni/Al2O3 facilitates the cracking of C–H bonds and self-reforming of bio-oil, increasing H2 production (which is increased by 42.3 % at 700 °C), thereby promoting the breakage of side chains of lignin-derived aromatics and the hydrogenation of unsaturated structures, suppressing the formation of small aromatic systems in coke (<6 rings). Nevertheless, enhanced formation of alkyl-aryl C–C bonds during aromatisation leads to more condensed coke structures.

Исследование устойчивости химического реактора полимеризации этилена

The chemical reactor is the main and most complex object in the management of the technological process of polymerization. When designing chemical reactors, it is necessary to select design and operating parameters that will be able to provide the only or most stable state with the specified process characteristics. To study the stability of the ethylene polymerization process in an autoclave reactor with a stirrer, it is necessary to build a mathematical model based on the analysis of the physico-chemical laws of the process and search for the necessary steady-state conditions for the reactor. A solution based on a deterministic mathematical model of ethylene polymerization is proposed. The description of the process of polymer molecule formation, which includes the stages of initiation, growth and chain breakage; the mechanism of chemical kinetics of ethylene polymerization; a system of assumptions to simplify the construction of a mathematical model. The mathematical model of an ethylene polymerization reactor in an autoclave reactor with a stirrer is a system of differential equations. When calculating the static reactor mode, the mathematical description contains a system of nonlinear algebraic equations, the solution of which is implemented using numerical methods. It is noted that chemical reactors can have not one, but several stationary states at the same values of variables and parameters. Knowing the coordinates of the stationary states of the chemical process, you can choose the one that is more preferable from the point of view of productivity or the quality of the products produced. As a result of the simulation, the existence of a single solution under the conditions found that ensure a stable stationary state of the chemical ethylene polymerization reactor is confirmed.

Unveiling the complex effect of Fe2O3 on NOx precursors evolution mechanism during sludge protein pyrolysis based on product characteristics

The multiple influence mechanisms of Fe2O3 on nitrogen evolution during sewage sludge pyrolysis were systematically investigated by correlating temperatures. The results showed that Fe2O3 promoted the pyrolysis of the sludge. The activation energy of the pyrolysis was reduced by 12–110 kJ/mol. Fe2O3 acted oxidatively on sludge nitrogen in the following order Fe2O3→Fe3O4 (ca. 528 K)→FexNy (ca. 763 K)→FexC (ca. 1023 K). The oxidation target of Fe2O3 on nitrogen containing compounds varied as a function of temperature. At temperatures of 528 K and 623 K, Fe2O3 hindered the deamination of proteins in char to NH3, facilitated the condensation of pyridines to nitrile, and impeded the generation of HCN. At temperatures of 763 K and 1023 K, Fe2O3 facilitated the cleavage of amines, heterocycles, and nitrile in char. Additionally, it promoted the breaking of chains and cyclization of long chain amines in tar. This process theoretically leads to the production of a great amount of NH3 and HCN at the front. Overall, Fe2O3 inhibited the release of NOx precursors through inhibition of deamination, fixation of nitrogen in char and consumption of NH3 and HCN. This study will establish the effect mechanism of action of Fe2O3 on the nitrogen conversion of sewage sludge pyrolysis at relevant temperatures. It will provide a theoretical foundation for controlling NOx and the targeted regulation NH3 (carbon-free hydrogen energy carriers) in the high-value conversion of nitrogen-rich biomass.