Char Yield Research Articles

Effects of solvent casted poly (lactic acid)/poly(ethylene glycol)/paraben derivative triazine films on antibacterial performance and cytotoxicity

AbstractA series of poly(lactic acid) (PLA) films that including fully paraben substituted triazine derivatives having anti‐bacterial properties have been prepared by utilizing the solvent‐casting method. PLA as biodegradable polymer, poly(ethylene glycol) (PEG) as a plasticizing agent and s‐triazine molecules (TA01, TA02, TA03, TA04, and TA05) behaving as an anti‐bacterial component have been utilized in the experiments. The influence of TA compounds on the antibacterial performance of PLA/PEG films was investigated for the first time against Gram‐negative Escherichia coli (E. coli) and Gram‐positive Staphylococcus aureus (S. aureus) bacteria via the contact active method. TA01‐03‐05 incorporated PLA/PEG films gave the best results against E.coli bacteria and log10 reductions of these films were 0.78, 0.64, and 0.65 respectively. The effect of TA compounds on the cell viability was investigated against cancer and non‐cancerous cell lines using an MTS assay. The results showed that TA compounds had a positive effect on cell growth in non‐cancerous cells, while they had a negative effect on cell growth in cancer cells. Furthermore, the addition of TA considerably increased the decomposition temperatures from 349° to 361° and char yield from 0.65 for PLA/PEG film to 2.3 for PLA/PEG/TA05. All of the films had good transparency and low opacity which was 7.2 for pure PLA used for control and the maximum opacity value was 11.2 observed for PLA/PEG/01. TA03 and TA04 caused a decrement of water vapor permission when compared to PLA/PEG films from 1439 to 749 and 664. It was also observed that pure PLA/PEG film lost weight rapidly over time during degradation tests. On the other hand, weight loss wasn't observed in PLA/PEG/TA films. This study focused on demonstrating the use of our new, flexible PLA/PEG derivatives in food and medical packaging.

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.

An Aspen plus process simulation model for exploring the feasibility and profitability of pyrolysis process for plastic waste management

Plastics, integral to various human activities, have led to a surge in production, posing substantial challenges in waste management. The persistent non-biodegradability of plastics, taking over a century to decompose, necessitates exploration into technologies for their conversion into sustainable fuels. Pyrolysis, an oxygen-free thermal decomposition process, emerges as a promising avenue for producing liquid fuels from plastic waste. This study's primary objective is to create and validate an Aspen Plus simulation model, enabling techno-economic evaluation and sensitivity analysis of pyrolysis for converting waste plastics into liquid fuels. Critical parameters—temperature, retention time, and particle size—are examined for their impact on product yield and quality. The methodology involves model development, validation, and subsequent simulations with various waste plastic types under different pyrolysis conditions. Experimental investigation using waste high-density polyethylene (HDPE) in an auger reactor yielded an oil yield of 61.29%, char yield of 10.98%, and syngas yield of 27.73% at 525 °C. Post-validation against this data, the model explored four plastic types, revealing significant influences of plastic type and reactor temperature on product yields. Polystyrene (PS) at 500 °C produced the highest oil content at 83.69%, with temperature affecting yield before secondary cracking. Techno-economic evaluation for a pyrolysis plant processing 10,000 tons of waste HDPE annually indicated a minimum selling price (MSP) of $302.50/ton, a net present value (NPV) of $12,594,659.7, and a 1.03-year payback period. This study provides crucial insights for designing an economically viable and sustainable pyrolysis process, guiding further research and industrial implementation.

High strength and high toughness Csf/SiC composites prepared by laser powder bed fusion/ reactive melt infiltration with the impregnation of boron-and silicone-containing phenolic resin

Laser powder bed fusion (LPBF) has emerged as an effective method for preparing complex structured silicon carbide (SiC) ceramics. However, the SiC components demonstrate low strength and high brittleness, which remain major challenges limiting its application. To overcome this limitation, short carbon fiber reinforced silicon carbide (Csf/SiC) composites are prepared by combining LPBF and phenolic resin binder impregnation (PRBI)-reactive melt infiltration (RMI), in which high char yield boron-and silicone-containing phenolic resin (BSiPF) impregnation is used to adjust the carbon density of green bodies and to reduce the pore size of green bodies. By optimizing the impregnation process, the carbon density can be brought close to the theoretical optimal value of 0.84 g/cm3, and the reduction of the pore size is conducive to the improvement of the reaction rate at the early stage of the reaction, which enhance the SiC phase content of Csf/SiC composites obtained by RMI. Meanwhile, the application of BSiPF results in a protective pyrolytic carbon (PyC) coating on the surface of Csf, which can reduce the erosion of Csf by molten Si during the RMI process, thus improving the fracture toughness of Csf/SiC composites. The final Csf/SiC composites exhibit the enhanced bulk density, bending strength and fracture toughness, reaching 2.90 ± 0.01 g/cm3, 257 ± 20 MPa, 3.52 ± 0.15 MPa m1/2, respectively. This study provides a new strategy for effective impregnation technique for the additive manufacturing (AM) of high strength and high toughness SiC composites.

Bio‐based benzoxazine composites derived from magnolol: Promising solution for sustainable alternatives for dielectric and superhydrophobic applications

AbstractTo alleviate the environmental hazard and minimize the practice of utilizing fossil fuel‐based precursors in the production of benzoxazines, sustainable bio‐phenol precursors namely magnolol and bio‐based amine furan‐2yl‐methanamine have been utilized to synthesize bio‐benzoxazine and was cured and characterized. The curing temperature of the synthesized bio‐benzoxazine monomer was found to be 216°C. Utilizing the carbon obtained from two different bio‐sources namely, chicken feather and cashew nut shell cake bio‐polybenzoxazine composites were prepared. The char yield of bio‐carbon reinforced bio‐polybenzoxazine composites was enhanced to 65% compared to that of neat polybenzoxazine (60%). The value of the dielectric constant of neat polybenzoxazine was found to be 5.52 which was further improved to a maximum of 8.9 and 7.8 on reinforcement of 15 wt% chicken feather carbon and 15 wt% cashew nut shell cake carbon respectively. The prepared bio‐polybenzoxazine composites exhibit a near superhydrophobic nature with the value of water repulsive angle at 150° than that of neat matrix (143°). From the obtained results, it is suggested that the sustainable bio‐carbon reinforced bio‐based benzoxazine will be a promising material for thermally stable, high dielectric, and water‐repellent applications.Highlights Eco‐friendly, sustainable magnolol‐based bio‐benzoxazine was synthesized. Waste valorization for bio‐carbon—poultry, and agricultural wastes were utilized. Bio‐carbon reinforcement marginally increases the thermal stability of composites. Bio‐carbon reinforced composites exhibit close to superhydrophobic nature. Incorporation of bio‐carbon enhances the value of dielectric constant.

Micro-fabrication of glassy carbon with low shrinkage and high char yield using high-performance photocurable phthalonitrile (PN) resins

Glassy carbons (GCs) are a significant class of materials that have attracted considerable attention in many scientific and technical fields due to their great thermal and chemical stability, excellent biocompatibility, and remarkable thermal and electrical conductivity. However, the thermal resistance and brittle nature of GCs pose limitations on their processing using conventional techniques such as melting extrusion or sintering. 3D printing as a rapidly developing technology advances product fabrication in prototyping and tooling provides a revolutionizing alternative of material processing with the advantage of accurately producing complex structures/shapes. This study demonstrates the micro-fabrication of GC objects based on novel photocurable high-performance phthalonitrile (PN) resins with a vat photopolymerization printing technology named as projection micro stereolithography (PμSL). In initial, soluble acrylate PN monomers are successfully developed and subsequently formulated into photopolymerizable resins. The resultant resins show excellent thermal and mechanical properties with Tg around 300 °C and flexural strength of 150 MPa after post thermal treatment. Being fabricated into 3D structures via PμSL printing, the obtained PN based objects are converted to GC products through pyrolysis in inert atmosphere with high char yield and low shrinkage. As a result, diverse microscale 3D GC objects are achievable and exhibit excellent structural integrity and fidelity. Our approach develops the micro-fabrication of dense and complex structured GC for the first time, providing a versatile functional platform for advancing next generation applications in medical tools, electrochemistry and precision micro-moulding as well as in energy and aerospace technologies.

Flame-Retardant Thermoplastic Polyether Ester/Aluminum Butylmethylphosphinate/Phenolphthalein Composites with Enhanced Mechanical Properties and Antidripping.

Aluminum butylmethylphosphinate AiBMP as a flame retardant and phenolphthalein as a synergistic agent were applied in a thermoplastic polyester elastomer (TPEE)) in the current study. The thermal properties, flame retardancy, crystallization and mechanical properties of TPEE/AiMBP with or without phenolphthalein were investigated using various characterizations, including the limiting oxygen index (LOI), vertical burning test (UL 94), thermogravimetric analysis TG, differential scanning calorimetry, microcombustion calorimeter (MCC), scanning electron microscopy (SEM), and mechanical tests. The results revealed that AiBMP alone is an efficient flame retardant of TPEE. Adding 15 wt.% AiBMP increases the LOI value of TPEE from 20% to 36%. The formula TPEE-15 AiBMP passed the UL 94 V-0 rating with no dripping occurring. The MCC test shows that AiBMP depresses the heat release of TPEE. In comparison with pure TPEE, the heat release rate at peak temperature and the heat release capacity of TPEE-15AiBMP are reduced by 46.1% and 55.5%, respectively. With the phenolphthalein added, the formula TPEE/13AiBMP/2Ph shows a higher char yield at high temperatures (>600 °C), and the char layer is stronger and more condensed than TPEE-15AiBMP.The tensile strength and elongation at break values of TPEE-13AiBMP-2Ph are increased by 29.63% and 4.8% in comparison with TPEE-15AiBMP. The SEM morphology of the fracture surface of the sample shows that phenolphthalein acts as a plasticizer to improve the dispersion of AiBMP within the matrix. The good char charming ability of phenolphthalein itself and improved dispersion of AiBMP make the TPEE composites achieve both satisfying flame retardancy and high mechanical properties.

Unleashing the potential of Boratrane and Silatrane: A game-changing approach for enhanced boron- and silicon- incorporation in phenol-formaldehyde resins and their thermal stability

In this study, we present an innovative and cost-effective method for the preparation of phenolic resin (PR) containing boron and silicon (BPR and BSiPR) using boratrane and silatrane. Through a one-pot synthesis via a sol-gel process, 3BPR and 3B5SiPR are successfully synthesized, utilizing boratrane and silatrane as the sources of boron and silicon. Our results demonstrate the effective introduction of boron and silicon elements into the PR matrix through the formation of BO4 (borate) and SiO4 (silicate) structures, as evidenced by Cph-O-B and B-O-Si linkages. Notably, the utilization of boratrane in the synthesis of 3BPR leads to the formation of a uniform structure of BO4, as confirmed by 11B-NMR analysis. Furthermore, the resulting resins exhibit an improved char yield of 72 % at 900 °C. The formation of borate and silicate species effectively reduces the content of phenolic hydroxyl groups, thus contributing to a decrease in weight loss during the carbonization process. Additionally, the migration of boron and silicon into the carbon structure promotes the formation of B4C and B8C crystal structures, resulting in the carbonization of resins and the formation of a graphene-like structure, as confirmed by Raman spectroscopy, which exhibits a broad 2D-band. The obtained carbon materials possess both Lewis acid and basic sites. The presence of Lewis acid sites was characterized through pyridine-adsorbed FTIR, while the Lewis basic sites and CO2 absorption were examined via TPD-CO2 analysis. The CO2 absorption capacities of 3BPR and 3B5SiPR were found to be 0.475 and 0.518 mmol/g, respectively.

Effects of multi-strain pretreatment on thermochemical properties and component structure of paulownia

This study aims to delve into the impact of long-term multi-strain pretreatment on the thermochemical characteristics of paulownia. The nine-month experimental analysis reveals that the fourth month marks a crucial turning point in the pretreatment process. From Stage I (0–4 months) to Stage II (4–9 months), the pyrolysis temperature range continuously narrows, reducing a maximum of 31.47%. The char yield initially increased by 10.25% and then decreased by 6.95%. Calorific value showed a slow initial decline of 3.98–4.08%, followed by a subsequent increase of 7.66%. The ignition point continued to rise by 5.61%− 5.78%. The compositional experimental results indicate that in the first stage, strain primarily depolymerize the high-polymer lignin, resulting in a decrease in calorific value. The increase in the relative content of syringyl lignin (S) contributes to the rise in char yield. In Stage II, the S units are converted into guaiacyl lignin (G), which has a lower char yield, while the exposed hemicellulose and cellulose undergo severe erosion. The relative content of lignin and enzymatic products with stubborn structures increases, leading to an increase in calorific value. However, the higher breaking temperature of bonds in these structures results in a continuous increase in the ignition point. This study clearly establishes that after nine months of pretreatment, the paulownia exhibits characteristics of rapid pyrolysis, high calorific value and ignition point, which provides a reliable basis for uncovering the potential reuses of paulownia.

Catalytic pyrolysis of lignocellulosic and algal biomass using NaOH as a catalyst

AbstractIn this work, the pyrolysis of barley straw (BS) and brown algae (BA) mixed with NaOH as a catalyst was compared. Four different catalyst‐to‐biomass mass ratios (i.e., 6:100, 8:100, 10:100, and 12:100) and five pyrolysis heating rates were examined. The kinetic parameters (e.g., the activation energy and pre‐exponential factor) were evaluated using the Friedman method and kinetic models. For noncatalytic pyrolysis, the average activation energies for BS and BA samples were 139.71 and 183.19 kJ mol−1, respectively. However, the addition of catalyst generally increased the average activation energy of BS samples but decreased that of BA samples. The enthalpy change and Gibbs free energy change revealed that both catalytic and noncatalytic pyrolysis processes were nonspontaneous and endothermic, and the inclusion of catalyst increased the average entropy change of the BS samples but decreased that of the BA samples. Char and biochar yields after pyrolysis were also analyzed quantitatively. These observations provide insight into the differences in catalytic pyrolysis between lignocellulosic and algal biomass species.

Influence of Temperature and Blending Ratio on Product Yield for Co-gasification of Torrefied Palm Kernel Shell and Low-Density Polyethylene

This study investigates the product yields produced from the co-gasification of torrefied palm kernel shell (TPKS) and low-density polyethylene (LDPE). Prior co-gasification, PKS was undergo pre-treatment process at different temperature. The optimum parameter for torrefaction was found at 250 °C for 60 min reaction time with 4.89 wt. % moisture content and 10.48 wt.% fixed carbon. Thus, the result indicated that TPKS a suitable fuel feedstock for futher thermal conversion. Then, TPKS and LDPE were gasified at temperature of 600, 800 and 1000 °C and blending ratio of 10:90, 50:50, 90:10 (TPKS:LDPE) for 60 min reaction time. Based on the findings found that, temperature plays an important role in co-gasification. Higher gasification temperature increases the carbon conversion which improves gasification rate. By varying temperature from 600 to 1000 °C, the gas yield increased whilst tar yield decreased sharply. For the effect of blending ratio, through blending of TPKS and LDPE, the gas and char yield increase, while tar decrease with increase torrefied TPKS ratio. Furthermore, it was observed that the product yields obtained from the co-gasification of TPKS and LDPE at 50:50 blending ratios produce the highest gas yield with low char and tar yield than another blending ratio. Therefore, based on the effect of temperature and blending ratio on product yield shows that the optimum parameter to produce maximum gas yield with minimum tar and char yield are at 50:50 (TPKS:LDPE) blending ratio at 800 °C for 60 minutes reaction time.

Enhancing Flame Retardancy and Thermal Insulation Performance of Silicone Rubber Composites Using Silicon Carbide

This study focuses on modifying silicone rubber using silicon carbide (SiC) to enhance the flame retardancy and thermal insulation properties of the composites. The study characterizes the thermal stability, mechanical properties, and flame retardancy of the composite materials. The results demonstrate the effective improvement in thermal stability achieved by incorporating SiC into the silicone rubber composites. At a SiC addition level of 6 wt.%, the composite material shows optimal thermal stability with an initial decomposition temperature of 487°C, which is 84°C higher compared to the pure matrix. Additionally, the SiC/SR composites system exhibits a char yield of 72.13% at 900°C, representing an approximately 9% increase compared to the pure SR matrix. Simultaneously, the incorporation of SiC significantly enhances the flame retardancy of silicone rubber. At a SiC addition level of 10 wt.%, the LOI (Limiting Oxygen Index) value increases by 10.5% to reach 30.4%, surpassing the non-additive sample. Moreover, the UL-94 classification of the composite material is V-0, meeting the standard for flame retardant materials.

Purification of Treated Wastewater Effluents from Residual Detergents using Activated Carbon Produced from Olive Seeds

This study reports the preparation and characterization of activated carbon derived from pulverized olive seeds, as well as its application in the elimination of detergents from wastewater effluents. The activated carbon was produced by carbonization followed by activation. The main characteristics of the prepared activated carbon viz. surface area, ash content, char yield and bulk density were determined. Batch studies were conducted to determine the primary factors influencing the removal efficiency of detergents. The factors considered were the contact time of adsorption, amount of adsorbent used, pH and the concentration of detergent. The characteristics of the produced activated carbon were surface area 546.0 ± 5.6 m2/g, ash content 1.30 ± 0.24%, char yield 23.85 ± 0.63% and bulk density 444.60 ± 3.25 kg/m3. The activated carbon effectively decreased the content of detergents to below 5 mg/L, which is the permissible limit for reusing in irrigation and recharging groundwater. This study indicates that the activated carbon derived from crushed olive seeds is effective in purifying treated wastewater effluents containing residual detergents.

The utilization of phytic acid as a reactive flame retardant in the preparation of a fully waterborne biobased epoxy system

AbstractA fully biobased waterborne flame‐retarded epoxy system was prepared using sorbitol polyglycidyl ether epoxy resin (SPE) and phytic acid (PA) as a reactive flame retardant (FR). The flame‐retardant efficiency was evaluated by comparing the reference SPE‐PA system with solventborne and waterborne SPE systems. Additional enhancement of intumescence and reduction of flammability was achieved by incorporating ammonium polyphosphate (APP) and melamine (MEL) into the SPE–PA system. PA, serving as a curing agent, contributed approximately 1% phosphorous content, resulting in an increased limiting oxygen index (LOI). UL‐94 flammability tests demonstrated improved FR properties with PA, and the addition of 2% phosphorous from APP to SPE‐PA achieved a self‐extinguishing V0 UL‐94 rating. Thermogravimetric analysis (TGA) revealed enhanced thermal stability and higher char yield with PA compared with other curing agents. Mass loss calorimetry (MLC) confirmed the superior charring effect of PA compared with other curing agents. The thermal insulation properties of the residual char were assessed by measuring the temperature on the back surface (Tb) of coated steel plates exposed to a 25 kW/m2 heat flux for 1 h. The PA sample containing 3%P of APP exhibited a Tb decrease of 130°C compared with the solventborne reference sample. Scanning electron microscopy analysis of the char morphology supported these findings, indicating the effectiveness of the intumescent FR system. Infrared spectra of the char residues and pyrolysis gaseous products were obtained to gain insights into the flame‐retardant mechanism of the different systems.

Preparation of thermally stable and flame‐retardant sugarcane bagasse‐ammonium dihydrogen phosphate/epoxy composites and their performance

AbstractEpoxy resin was often applied in fiber‐reinforced composite materials, adhesives, and encapsulation materials. However, epoxy was easily flammable and limited its usage in certain applications. The study recycled and reused agricultural waste sugarcane bagasse to prepare a halogen‐free bio‐based intumescent flame retardant and then mixed with epoxy resin to prepare a composite containing polymer with improved thermal properties and flame retardancy of the materials. The work followed the concept of circular economy and sustainability. Bagasse‐ammonium dihydrogen phosphate (ADP) flame retardant was added to an epoxy resin to prepare epoxy/bagasse‐ADP composites, an effective flame‐retarding composite material through hydrothermal method. Adding bagasse‐ADP increased the thermal stability and flame retardancy of the composite materials compared with that of pure epoxy. For the material with 30 wt% added bagasse‐ADP, the char yield was 32.3 wt%, which was 18.2 wt% higher than that of pure epoxy (14.1 wt%) through thermogravimetric analysis. In addition, the limiting oxygen index increased from 21% to 30%, and the UL‐94 classification improved from “Fail” to “V‐0.” This performance was attributed to the nitrogen, phosphorus, and silicon content of the flame retardant.

Synthesis and flame‐retardant analysis of a novel P/N containing flame retardant on epoxy resin composites

AbstractA new reactive flame‐retardant N′‐(1‐(4‐hydroxyphenyl)‐1‐(6‐oxido‐6H‐dibenzo[c,e][1,2]oxaphosphinin‐6‐yl)ethyl) benzohydrazide (DOPO‐BD) was synthesized via a two‐step reaction involving the Schiff base reaction between benzohydrazide and 4‐hydroxy acetophenone, followed by a reaction between the imine‐based condensation product and 9, 10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO). The chemical structure of DOPO‐BD was well characterized by Fourier transform infrared spectra (FTIR), 1H, 13C, 31P NMR, and high‐resolution mass spectrometry (HRMS). The DOPO‐BD was utilized as a reactive flame retardant and co‐hardener in DGEBA/DDS. The epoxy composites of varying phosphorus weight percentages were synthesized. UL‐94 and LOI tests were used to investigate the flammability of composites. The epoxy composites retained good transparency, which was measured by UV–vis spectroscopy. Thermogravimetric analysis (TGA) observed an increase in the thermal stability of epoxy composites in a higher temperature range with increased char yield. In the UL‐94 and LOI tests, EP/DOPO‐BD(1.5%P) sample gave a V‐0 rating and 30% LOI value. The cone calorimeter test indicated a decrease in total heat released (THR), peak of heat release rate (pHRR), and total smoke production (TSP) for EP/DOPO‐BD(1.5%P) in comparison with epoxy (EP). The mechanical properties and glass transition temperature (Tg) of the epoxy composites were determined by Dynamic mechanical analysis (DMA), which showed an increase in storage modulus and a decrease in Tg.

Characterization of cassia fistula seed and shell co-pyrolysis yield optimization by response surface methodology and compositional analysis

The primary objective of this study was to enhance the bio-oil yield from the seed, shell, and blend of Cassia fistula (CF) through the application of response surface methodology (RSM). The study focused on analysing the product composition, qualities and optimizing the process by altering the heating temperature, the heating rate, and CF seed to CF shell blend ratio. The physicochemical characteristics of biomass samples were evaluated through Fourier Transform Infrared, proximate analysis, elemental analysis, X-ray diffraction, higher heating value, fuel reactivity, thermogravimetric analysis, CHO index, etc. Analysis of variance established that the temperature during co-pyrolysis of the CF seed and shell was the most critical factor in determining the bio-oil yield. The optimal bio-oil yield, gas yield, and char yield were obtained at a heating temperature of 450 °C, a heating rate of 10 °C/min, and a blend ratio of 75%. A statistical model was constructed to examine the parameters identified through analysis of variance as having a substantial impact on the experimental results. This study provides insights into RSM approaches that lead to a more practical approach to process modelling. Gas chromatography-mass spectrometry revealed that the bio-oil was primarily composed of hydrocarbons, followed by ketones and phenolic compounds. The bio-oil analysed exhibited a carbon chain range of C2-C12.

Synthesis and Characterization of DOPO-Containing Poly(2,6-dimethyl-1,4-phenylene oxide)s by Oxidative Coupling Polymerization.

A set of polyphenylene oxides incorporating DOPO (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide) functionality, denoted as DOPO-R-PPO, was synthesized by copolymerization of 2,6-dimethylphenol (2,6-DMP) with various DOPO-substituted tetramethyl bisphenol monomers. In the initial step, a Friedel-Crafts acylation reaction was employed to react 2,6-DMP with different acyl chlorides, leading to the formation of ketone derivatives substituted with 2,6-dimethylphenyl groups. Subsequently, the ketones, along with DOPO and 2,6-DMP, underwent a condensation reaction to yield a series of DOPO-substituted bisphenol derivatives. Finally, polymerizations of 2,6-dimethylphenol with these DOPO-substituted bisphenols were carried out in organic solvents using copper(I) bromide/N-butyldimethylamine catalysts (CuBr/DMBA) under a continuous flow of oxygen, yielding telechelic PPO oligomers with DOPO moieties incorporated into the polymer backbone. The chemical structures of the synthesized compounds were characterized using various analytical techniques, including Fourier transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance (1H NMR), phosphorus nuclear magnetic resonance (31P NMR), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). When compared to conventional poly(2,6-dimethyl-1,4-phenylene oxide)s with a similar molecular weight range, all DOPO-PPOs exhibited higher glass transition temperatures, enhanced thermal degradability, and increased char yield formation at 800 °C without compromising solubility in organic solvents.

Development of a three-stage process for high coal desulfurization and char yield

Efficient pyrolytic desulfurization with high char yield is a promising yet challenging approach for the cleaner utilization of abundant high-sulfur coal reserves. In this study, we have discovered that a single pyrolysis process under either oxidizing or reducing conditions cannot efficiently remove various sulfur forms while preserving a high char yield. To address this challenge, we propose a three-stage desulfurization process: a low-temperature oxidative pyrolysis (LTOP), a high-temperature reductive pyrolysis (HTRP), and a dry magnetic separation process. LTOP operates in a fluidized bed for only a few minutes to oxidize the diamagnetic pyrite particle surface to Fe2O3 while minimizing char losses. HTRP occurs in another fluidized bed for an appropriate duration to substantially remove organic sulfur while reducing Fe2O3 to highly magnetic Fe3O4 or Fe. Partially magnetized pyrite particles are then removed from the char through magnetic separation. When applied to anthracite coal with a total sulfur content of 4.99%, this process achieves nearly 100% desulfurization for pyritic sulfur and 74.81% for organic sulfur. Ultimately, it recovers 94.5% of the original coal excluding volatiles as char, with 91.6% being low-sulfur char.

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.