JOURNAL OF THE AMERICAN CERAMIC SOCIETY
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2023
·
IF 3.9
Zhe Zhao,Cheng Han,Xiaozhou Wang,Yingde Wang
Metallopolymers containing refractory metal in the main chain are highly desired but rarely reported as oxygen-free single-source precursors for preparing ultrahigh-temperature ceramics. Herein, a novel single-source precursor of poly-hafnium-borocarbosilane (PHBCNS) with an Hf–N–B backbone molecular structure was synthesized through the dehalogenation reaction between HfCl 4 and B(NHCH 3 ) 3 . The polymeric Hf–N–B chain with large bond angle and conjugated molecular structure endowed the PHBCNS precursor to be relatively stable, dissolvable, and meltable. Subsequent precursor pyrolysis up to 1800°C resulted in an HfC/HfB 2 nanocomposite comprising an Hf content of 87.54 wt%, with the average grain size of HfC and HfB2 to be 34.9 and 74.1 nm, respectively. The ceramization mechanism and phase evolution from the PHBCNS precursor to HfC/HfB 2 composite ceramics were thoroughly investigated. This work not only highlights a novel Hf–N–B backbone polymer with high metal content and good shaping properties but also provides fresh insights of designing single-source precursors for ultrahigh-temperature composite ceramics.
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RSC Advances
·
2019
·Vol. 9
·期 1
·377-388
·
IF 3.049
Tianyu Wu,Wenqing Zhang,Xin Jin,Xiangyi Liang,Gang Sui,Xiaoping Yang
Carbon fiber-reinforced polymer composites have been widely used in various fields and have inevitably produced large amounts of composite waste. The recycling of carbon fibers with high value has become an active research topic at related institutions and production enterprises. In this paper, the catalytic pyrolysis of T700 carbon fiber/epoxy composites in molten salt was studied. Due to the efficient solubility of molten ZnCl2 for the epoxy matrix and catalytic fracture of the C–N bonds by the action of Zn2+ ions, the epoxy composites can be completely degraded at 360 °C in 80 min under standard pressure, and the reclamation efficiency was significantly enhanced compared with conventional pyrolysis reclamation without a catalyst. The types and contents of the main oxygen-containing functional groups on the surfaces of the fibers reclaimed with ZnCl2 were similar to those of the virgin fibers, and the graphitization structure of the carbon fibers was not destroyed in the pyrolysis process. The tensile strength of a monofilament of the fibers reclaimed with ZnCl2 was obviously higher than that of fibers reclaimed in air; it reached a high retention rate that was about 95% that of the virgin fibers. The fibers reclaimed with ZnCl2 after sizing exhibited a desirable reinforcing effect on the flexure performance and interlaminar shear strength of unidirectional carbon fiber/epoxy composites which was close to the performance levels of composite samples containing commercial T700 carbon fibers. Therefore, efficient technology to reclaim high-quality carbon fibers from epoxy matrices has been devised.
研究领域:
材料科学
·
化学工程
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JOURNAL OF ALLOYS AND COMPOUNDS
·
2026
·
IF 6.7
Man Wang,Shichao Chen,Kang Wang,Song Song,Xitao Wang
A Ru-doped CoFe MOF-derived Co 3 O 4 -Fe 2 O 3 heterostructure was fabricated via mild pyrolysis. • The low-temperature strategy preserves the 2D MOF nanosheet scaffold. • Ru incorporation modulates Co/Fe electronic states and suppresses structural aggregation during mild pyrolysis. • Ru 0.024 CoFe MOF-250 requires only 227 mV at 20 mA cm −2 with a Tafel slope of 33.67 mV dec −1 . • Excellent durability is demonstrated by only 8.3 mV potential increase after 100 h at 20 mA cm −2 . Metal-organic frameworks (MOFs) are promising for the oxygen evolution reaction (OER), yet they suffer from framework collapse and active-site aggregation during high-temperature pyrolysis. Herein, a Ru-doped CoFe MOF is grown in situ on nickel foam (NF) and subsequently annealed at 250 °C, forming a Co 3 O 4 -Fe 2 O 3 @Ru 0.024 CoFe MOF heterostructure. The incorporation of Ru modulates the local electronic structure of the Co/Fe centers, while mild annealing at 250 °C generates Co 3 O 4 -Fe 2 O 3 nanophases within the partially preserved MOF nanosheet scaffold. This creates intimate heterointerfaces that facilitate rapid charge transfer. In 1.0 M KOH, the optimized electrode delivers a current density of 20 mA cm -2 at an overpotential of only 227 mV, exhibits a low Tafel slope of 33.67 mV dec −1 , and achieves an electrochemical surface area (ECSA) of 133.5 cm 2 . After 100 h of operation at 20 mA cm −2 , the potential increases by merely 8.3 mV. This work presents an effective strategy that combines Ru doping with mild pyrolysis to construct efficient and stable MOF-based OER electrocatalysts.
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FUEL
·
2023
·
IF 7.4
Ruolin Li,Yang Ren,Chengyang Cao,Chao He,Hongyun Hu,Xian Li,Hong Yao
Recently, waste tires gain a growing recognition of the potential as value-added fuel via pyrolysis. In the present study, molten salt was proposed to be used for the waste tires pyrolysis, aims to enhance heat transfer efficiency, and then reduce energy input for the mechanical shredding of waste tires into small particles before pyrolysis. In detail, the conversion and products formation behavior of two waste tires (of different particle sizes) were compared by a constructed molten salt thermal treatment system. Results show that H 2 and CH 4 contents of the pyrolysis gas increased substantially, and smaller tire particles produced more H 2 and CH 4 (up to 500%), while CO 2 content dropped to zero. Also, the contents of benzene increased remarkably with molten salt added (growth rate is between 1100% and 1800%) for electro-mobile tires, while caprolactam was disappeared. Specifically, benzene yield increases and then decreases with increasing particle size. In addition, molten salts were also effective in removing sulfur and ash from pyrolytic char, with more than 60% of the sulfur fraction being removed. These findings could provide theoretical support for the development of low-cost thermal treatment technology for waste tires.
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INDUSTRIAL CROPS AND PRODUCTS
·
2023
·
IF 5.9
Bo Wang,Kai Li,Cheng-bo Zhang,Ting Huang,Ti-peng Wang,Qiang Lu
A series of regenerated cellulose (RC) were prepared by a H 3 PO 4 -H 2 O system with different H 3 PO 4 concentrations. The effects of H 3 PO 4 concentrations on the physicochemical properties of RCs were studied, including crystallinity index (CrI), hydrogen bond energy (E H ), accessibility, and degree of polymerization (DP). The catalytic pyrolysis experiments of RCs were executed with a pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) instrument and a lab-scale device, to investigate the regulatory function of cellulose structure on the LGO formation. The results indicated that the H 3 PO 4 -H 2 O system could transform the cellulose crystal form from Ⅰ to amorphous form, reduce its CrI and E H significantly, improve its accessibility, while had slight effects on the DP. These changes made RC more appropriate for the selective preparation of LGO, and the corresponding optimal catalyst loading and pyrolytic temperature were also decreased significantly. With phosphoric acid activated carbon as the catalyst, the highest yield of LGO from RC in Py-GC/MS experiments reached 21.50 wt% at catalyst/cellulose (Cat/Cel) ratio of 1/5 and 270 °C, which was much higher than the 18.16 wt% of LGO gained from untreated cellulose at Cat/Cel ratio of 1/3 and 300 °C. In the lab-scale device, the maximum LGO yield from RC was 17.09 wt% at 270 °C and Cat/Cel ratio of 1/6.
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Nanoscale
·
2023
·Vol. 15
·期 39
·16188-16198
·
IF 6.7
Qingxue Lai,Hongmei Zheng,Wanying Zhang,Yi Sheng,Luanjie Nie,Jing Zheng
Fe–N–C catalysts with highly dispersed metal active centers were developed as promising non-precious metal materials for acidic oxygen reduction reaction (ORR) electrocatalysis. However, such kind of novel catalysts still suffer from major challenges in the manipulation of dispersion, utilization, and stability of the Fe-based metal centers. Herein, a N-rich molecular dual-guided pyrolysis strategy was proposed to develop an efficient yolk-shelled Fe–N–C ORR electrocatalyst. A unique yolk-shelled nanostructure with a relatively ordered shell and disordered yolk of a carbon skeleton was controllably constructed via this guided-pyrolysis route from the precursor of Fe-doped zeolitic imidazolate framework-8 (Fe-ZIF-8). Moreover, the atomic-level dispersion of Fe element in the carbon skeleton could be achieved via the dual guidance from phenanthroline and melamine molecules. The optimized Fe–N–C catalyst demonstrated a half-wave potential of 0.78 V vs. RHE in acid media, close to commercial 30% Pt/C, along with a small negative shift of 19 mV after an accelerated durability test. These enhanced electrocatalytic properties could be attributed to the preferred transformation of the Fe precursors to atomically dispersed Fe–Nx active configurations, as well as the enhanced three-phased interfacial reaction kinetics.
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Asia-Pacific Journal of Chemical Engineering
·
2021
·Vol. 16
·期 3
·e2609
·
IF 1.447
Siliang Gao,Wencheng Tang,Ming Zhao,Siyuan Qie,Weiwei Pang,Longsheng Tian
Highly efficient separation of benzene, toluene, and xylenes (BTXs) from pyrolysis gasoline is very important in petrochemical industries. Though the extractive distillation (ED) process is simpler and consumes less energy compared with liquid–liquid extraction process, it is difficult for a single solvent, for example, sulfolane, to achieve both high purity and high yield of BTXs. In this work, methylsulfonylethane (MSE) was chosen as a cosolvent to improve the selectivity of sulfolane after solvent screening, and factors that may affect the selectivity of the composite solvent were fully investigated, such as the content of cosolvent, solvent to feed ratio, the composition of the feed, and temperature. Furthermore, 240 h of continuous extractive distillation and solvent recovery experiment was carried out using sulfolane (85 wt%)–MES (15 wt%) mixture as solvent. The purity of mixed aromatics obtained was 99.83%, and the yield was as high as 99.7%.
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Journal of Cleaner Production
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2021
·
IF 9.297
Ya Gao,Tong Yue,Wei Sun,Dongdong He,Chenglong Lu,Xinzhuang Fu
Acid recovering and iron recycling from pickling waste acid are the desired goal of the steel mills for current ecological requirements and economic benefit. This study proposed a novel method to treatment the pickling waste acid using extraction separation of ferric chloride and hydrochloric acid , following by the spray pyrolysis of ferric chloride stripping liquor. Comparing the Ruthner method, the significant technical advantages of this method is the lower treatment load and operating costs for the spray pyrolysis process, attributing to the reuse of most hydrochloric acid without iron powder neutralizing. Different extractants (TBP, CYC, IA, OA, and PA) are compared to extract ferric ion from high-concentration hydrochloric acid solution and the optimum conditions are researched. Spectroscopic analysis is performed to characterize iron state in extractants. For the stripped solution, spray pyrolysis is employed to produce high-purity Fe 2 O 3 fine particles, meanwhile hydrochloric acid is recovered for following pickling procedure. The results showed that the effect of CYC under lower O/A ratio was better than that of TBP, and the opposite occurred at higher ratios. Three-stage extraction efficiency can reach over 80% at O/A = 2:1. The final O/A ratio of 1:1 was chosen for the stripping of iron-loaded extractants. Raman and UV–visible found that it was [FeCl 4 ] - anion that existed in Fe-loaded TBP and CYC. Spray pyrolysis at 1000 °C can obtain fine pure Fe 2 O 3 and hydrochloric acid. Eventually, a feasible technological process was put forward to recycle all chemicals and achieve zero emission of water and solid waste in the whole process.
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ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH
·
2021
·Vol. 28
·期 36
·50500-50509
·
IF 4.223
He Qian,Huang Shengxiong,Luo Wei,Su Yifeng,Xia Mao,Zhou Nan,Zhou Zhi
In-situ catalytic pyrolysis has simple process configuration and low cost. Ex-situ catalytic pyrolysis can optimize the pyrolysis capacity and upgrade catalysis, and the catalytic can be reused. But there have been few studies researched on compare in-situ and ex-situ catalytic pyrolysis of the OS performed in similar reactor with two kinds of catalytic. This paper study the pyrolysis of oily sludge (OS) uses CaO and oily pyrolysis char as catalytic at 700 °C. Through analysis the pyrolysis oil (PO), pyrolysis solid (PS) and pyrolysis gas (PG) during pyrolysis procedure to research the difference between in-situ and ex-situ catalytic pyrolysis. The gas chromatography-mass spectrometry (GC-MS) results show that CaO was conducive to the synthesis of aromatics, which content more than aliphatics and heterocyclics in CaO-i (i: in-situ) and CaO-e (e: ex-situ) groups. However, char greatly inhibits the production of aromatic compounds and promotes the production of aliphatic compounds. Gas chromatography (GC) results present that the char and CaO can greatly increase the content of combustible gas and the content reach to 85.85%, the pyrolysis gas (PG) keep at the highest combustion performance in char-CaO-i group. Meanwhile, compared with uncatalyzed groups, the content of CH 4 and CO increased about 2.05% and 3.93%, respectively. Fourier transform infrared spectroscopy (FT-IR) show that char and CaO reduce the function groups number of pyrolysis solid (PS), and it shows that the pyrolysis reaction is more complete. This research is expecting to provide theory support for catalytic pyrolysis of OS.
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JOURNAL OF ANALYTICAL AND APPLIED PYROLYSIS
·
2021
·
IF 5.541
Shengxiong Huang,Yifeng Su,Wei Luo,Qian He,Sheng Huang,Nan Zhou,Zhi Zhou
Pyrolysis is a research hotspot for realizing Chinese Herb residue (CHR) treatment and resource utilization, but there is little reported about in-situ no support catalytic pyrolysis of CHR. In this work, kinetics and no support catalytic pyrolysis characteristics of CHR were studied using a thermogravimetric analyzer and a fix-bed reactor system, respectively. Three groups: Ni-Fe, Ni-Cu and Ni-Co add into CHR and three kinetic methods: Coats-Redfern (CR) method, Flynn-Wall-Ozawa (FWO) method and Distributed Activation Energy Model(DAEM)use for calculate the activation energy, then analyses the gas, bio-oil and char of CHR pyrolysis. The results show that, catalysts can reduce the pyrolysis reaction activation energy. In FWO and DAEM model, the reaction activation energy will increase sharply if the conversion over 0.7. Compare with no catalyst group, add catalyst can restrain gas generation but good for oil production and char formation. Meanwhile, the surface of char is smoother than no catalyst. After test the char, we find that, metals of Ni, Fe, Cu and Co almost enrich in char, which may reuse as catalytic. This study may provide a feasible direction for the industrial application of CHR.
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Scientific Reports
·
2020
·Vol. 10
·期 1
·1-14
·
IF 3.998
Liu Quanyou,Peng Weilong,Meng Qingqiang,Zhu Dongya,Jin Zhijun,Wu Xiaoqi
Thermochemical sulfate reduction (TSR) is common in marine carbonate gas reservoirs, leading to complicated isotope characteristics of TSR-altered gas. This study aims to better understand how TSR affects the geochemical and isotopic compositions of alkanes in pyrolysis products. Pyrolysis of TSR were conducted with crude oil, nonane (C 9 ) and methylnaphthalene (MN) in the presence of MgSO 4 solution at temperatures of 350 °C, 360 °C, and 370 °C for different durations of 4–219 h in a closed system. Results show that carbon and hydrogen isotope compositions of alkane gas resulting from TSR (pyrolysis with crude oil and MgSO 4 ) became heavier with increasing carbon number, i.e., δ 13 C 1 < δ 13 C 2 < δ 13 C 3 and δ 2 H–C 1 < δ 2 H–C 2 < δ 2 H–C 3 . Compared with the δ 13 C 1 , δ 13 C 2 and δ 13 C 3 increased in a much wider range as heating continued. Carbon and hydrogen isotopes of alkane gas produced by TSR became heavier with increasing gas souring index. Values for δ 13 C 1 –δ 13 C 2 and δ 2 H–C 1 – δ 2 H–C 2 typically decreased as oil and C 9 underwent thermal cracking. Comparative experiments using C 9 in the presence of MgSO 4 produced partially reversed carbon isotope series (δ 13 C 1 > δ 13 C 2 ), which, for the first time, confirmed the ability of TSR to cause isotopic reversal from pyrolysis. The residual heavy alkanes gradually became 13 C-enriched during TSR, which increased δ 13 C 2 values and changed the partially reversed isotope sequence to a positive sequence (δ 13 C 1 < δ 13 C 2 ). The discovery of a partial reversal of the carbon isotope series of alkane gases through pyrolysis will further deepen the understanding of TSR-altered natural gas.
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Applied Sciences-Basel
·
2020
·Vol. 10
·期 21
·7607
·
IF 2.474
Yizhi Liu,Xu Liu,Ping Hu
A novel approach was proposed to increase the compactness, shorten the preparation period, and reduce the preparation cost by introducing acetone to optimize the polycarbosilane impregnation process. The porosity in internally derived SiC ceramics decreased and pore size was limited by using this new method, which led to higher compactness. Meanwhile, with the increase in acetone content, the viscosities of polycarbosilane and the wetting angles of polycarbosilane/graphite decreased appreciably, and the viscosity was 6.0 mPa·s with 40 wt.% acetone added—a factor of about 30 lower than that of original polycarbosilane. The wetting angle between polycarbosilane and graphite significantly decreased by 40%, which resulted in an enhancement in the impregnation efficiency of liquid polycarbosilane and a much shorter preparation period. This work provides a convenient and efficient method that is assistant during the practical production process of carbon fiber reinforced ceramic matrix composites (CMCs).Keywords:polycarbosilane;acetone;viscosity;wettability;impregnation efficiency
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