INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
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2021
·
IF 5.816
Wenjuan Li,Shuo Yu,Liang Zhang,Jianfa Chen,Weiguo Cao,Yanhua Lan
The pyrolysis and combustion mechanism of the hydrocarbon fuel has important scientific and practical significance. However, it is difficult to detect the whole intermediates and products using traditional methods, which brings trouble to the analysis of the reaction process. In this paper, the microscopic reaction mechanism and the main products of n- eicosane (C 20 H 42 ) were simulated based on the reactive force field molecular dynamics (ReaxFF-MD). The effects of temperature (2000–3500 K) and oxygen on the initial decomposition, the distribution of main products, and the reactive pathways of C 20 H 42 fuel were studied to determine its reaction mechanism. The initial decomposition of C 20 H 42 was mainly initiated by small alkyl radicals in pyrolysis, and by the oxygen-containing radicals in combustion. The participation of oxygen had a greater effect on accelerating the decomposition reaction . The reactions involving oxygen of C 20 H 42 initial decomposition accounted for 87.5% of the total reactions at 2000 K. Moreover, the detailed distribution and formation pathways of the main products of H 2 , C 2 H 4 , CH 4 , H 2 O, CO, and CO 2 were depicted to construct the overall reaction mechanism of C 20 H 42 . •H radical formed from the composition of C 2 H 4 was exactly consistent with the •H radical consumed by the generation of CH 4 and H 2 in the pyrolysis stage. The feasibility of the simulation method was verified by the result of thermal analysis. The results are helpful for further research on the reaction mechanism of hydrocarbon fuels.
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高影响因子
RENEWABLE ENERGY
·
2021
·
IF 8.001
Jun Zhang,Chengyu Li,Haoran Yuan,Yong Chen
In the present study, Ru modified hierarchical zeolites x Ru-MZSM were developed for cellulose fast pyrolysis . Comprehensive catalyst characterizations including XRD , XPS , N 2 adsorption-desorption, Py-IR and so on, were performed to unveil the essential structural properties. The chemical modification and Ru decoration remarkably regulated the distribution of Brønsted/Lewis acid sites. The presence of RuO x species would supply abundant strong Lewis acid sites for participating catalytic cracking , dehydration, decarbonylation, decarboxylation, cyclization, aromatization, etc., in cooperation with Brønsted acid sites. In-situ generated active Ru 0 centers during cellulose pyrolysis might facilitate the proceeding of deoxygenation , hydride transfer, and dehydrogenation . Among the as-prepared catalysts screened, 2Ru-MZSM was much more efficient in aromatics production from cellulose fast pyrolysis compared to parent ZSM, wherein the total aromatics yield achieved 16.8% at temperature of 650 °C and heating rate of 10 °C/ms with corresponding E value as low as 23.40 kJ/mol. Also, plausible reaction mechanism for x Ru-MZSM involved cellulose fast pyrolysis was proposed in detail.
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高影响因子
ENERGY & FUELS
·
2021
·
IF 3.605
Bin Hu,Wen-luan Xie,Yang Li,Zhen-xi Zhang,Ji Liu,Bing Zhang,Ti-peng Wang,Qiang Lu
The lignin pyrolysis process involves complex interaction reactions, where the bimolecular concerted interactions have been rarely studied. In the present work, an extended concerted interaction mechanism, hydroxyl-assisted hydrogen transfer (hydroxyl-AHT), was proposed based on the pyrolysis of the typical nonsubstituted and α-hydroxyl-substituted β-O-4 type lignin models (2-phenylethyl phenyl ether, PPE, and 2-phenoxy-1-phenylethanol, α-OH-PPE). This hydroxyl-AHT mechanism was investigated and confirmed with the combined fast pyrolysis experiments and quantum chemistry modeling. The results indicate that phenolic, watery, alcoholic, and enolic hydroxy compounds all can act as mediators for the concerted hydrogen transfer process in lignin pyrolysis and have similar assistant effects. Whereas, the hydroxyl-AHT has a great influence on the competitiveness of different concerted reactions to break the Cβ–O, Cα–Cβ, and Cα–OH bonds, respectively. To compare the pyrolysis of PPE and α-OH-PPE, the α-hydroxyl substituent leads to a significant promotion to the Cβ–O cleavage based on hydroxyl-AHT because there are more hydroxyl mediators and more concerted reaction types that can be involved in the bimolecular hydrogen transfer in α-OH-PPE pyrolysis. Hence, more phenol derived from the Cβ–O breakage was detected in the pyrolysis experiment of α-OH-PPE than that of PPE. In addition, this bimolecular hydroxyl-AHT interaction mechanism is universal in the concerted pyrolysis processes of lignin, also accelerating the cleavage of α-O-4 linkage, β-1 linkage, etc.
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高影响因子
CHEMOSPHERE
·
2021
·
IF 7.086
Siyu Jiang,Lili Yan,Runkai Wang,Guanghui Li,Pinhua Rao,Mengcan Ju,Ling Jian,Xin Guo,Lei Che
Facile and low-cost preparation are essential in the conversation of agricultural waste into biochar. In this work, nitrogen-doped biochar (NBC-350-0.1) was prepared by thermal decomposition of urea (urea/biochar = 0.1:1 mass ratio) at a low temperature of 350 °C. NBC-350-0.1 showed good performance for Pb(II) removal with the maximum adsorption capacity of 130.87 mg g −1 at 25 °C, which was five times that of pristine biochar (BC). Adsorption kinetics, isotherms and thermodynamics studies indicated that the adsorption of Pb(II) by NBC-350-0.1 or BC was the homogeneous monolayer adsorption with chemical action as the rate-limiting step, and was accompanied by spontaneous endothermic. Further analysis showed that the removal of Pb(II) on NBC-350-0.1 and BC depended on the complexation with unsaturated carbon bonds and ion exchange with Ca(II). Moreover, graphitic- and pyridinic-N in NBC-350-0.1 exerted a key part in the adsorption of Pb(II). NBC-350-0.1 regenerated by NaOH exhibited excellent recycling performance keeping the original removal efficiency at 84% after five cycles. In addition, this N doping method is suitable for improving the performance of coffee grounds, sawdust, and bagasse biochar. These results would provide an idea for obtaining recyclable N-doped biochar to treat the Pb(II) polluted wastewater.
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PubMed
高影响因子
COMBUSTION AND FLAME
·
2021
·
IF 4.185
Wang Li,Jiu-Zhong Yang,Long Zhao,Dan Yu,Zhen-Yu Tian
With biofuels market expanding, amines, as an important compound class in biofuels, are attracting increasing attention. The pyrolysis of n-propylamine (NPA) was studied in a flow tube using tunable synchrotron photoionization and molecular-beam mass spectrometry techniques. 28 and 30 species, including nitrogenous compounds and hydrocarbons, were identified and quantified at 30 and 760 Torr, respectively. 1,3-Cyclopentadiene, 1,4-pentadiene, 2-methyl-1,3-butadiene and benzene, were newly detected compared with previous studies of methylamine and ethylamine. HCN, NH 3 , N 2 and methanimine were detected as the dominant nitrogenous products. Moreover, minor aliphatic and unsaturated amines were also identified, such as methylamine, ethylamine and acetaldimine. Ethylene achieved at the highest level among hydrocarbon products. With the pressure increasing, the onset temperature of NPA pyrolysis shifts towards low temperature region and NPA decomposes faster. A comprehensive detailed kinetic model involving 405 species and 2668 reactions was developed with reasonable predictions. According to rate-of-production analysis, H-abstractions, especially at C α position of NPA, are the major consumption pathways of NPA. In addition, unimolecular reaction breaking C α -C β bond is the important consumption channel of NPA at 30 Torr, while its positive effect is seriously weakened at 760 Torr. The H-abstraction at C α (NPA+ H CH 3 CH 2 CHNH 2 +H 2 ) plays a leading role for NPA consumption at 760 Torr. The reactions, CH 3 +CH 3 =C 2 H 5 + H and CH 3 CHCHNH 2 + H CH 2 CHCHNH 2 +H 2 , tend to present inhibiting effects on NPA consumption at 30 and 760 Torr, respectively. These results could provide a theoretical basis for further combustion kinetic studies of biofuels and amine fuels.
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ENVIRONMENTAL SCIENCE & TECHNOLOGY
·
2020
·
IF 7.864
Wenmei Tao,Xingwei Yang,Yan Li,Ruizhi Zhu,Xiaoxi Si,Bo Pan,Baoshan Xing
Persistent free radicals (PFRs) may cause negative impacts to human health and the environment because of the induced reactive oxygen species. We expect that PFRs could be generated in the condensable volatiles formed during lignocellulose biomass pyrolysis. Elucidating the structural origin and the formation mechanism of PFRs is important for an in-depth understanding of air pollutants from the pyrolysis or combustion of lignocellulose biomass. This work selected rice straw and pine sawdust to represent agricultural and forest biomass residues. The pyrolysis mechanism, volatile components, and PFR generation were discussed based on the analysis of thermogravimetry–Fourier transform infrared spectroscopy–mass spectrometry (MS), pyrolysis–gas chromatography/MS, and electron spin resonance (ESR). Levoglucosan, furans, and 2-methoxyphenols were the main pyrolytic compounds for cellulose (CL), hemicellulose (HC), and lignin (LG), respectively. Obvious ESR signals were detected in the condensable volatiles of LG, while no ESR signals were detected for those of CL and HC. Higher ESR signals were detected in lignocellulose with a higher content of LG. Therefore, LG was the main structural basis to generate PFRs in lignocellulose condensable volatiles, mostly attributed to the methoxyphenol components. This study provides useful information regarding the generation mechanisms of and the structures related to PFRs, which is essential to understand the risks of lignocellulose pyrolytic volatiles.
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PubMed
高影响因子
JOURNAL OF MATERIALS SCIENCE-MATERIALS IN ELECTRONICS
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2021
·Vol. 32
·期 4
·4125-4131
·
IF 2.478
Zheng Han,Liu Ying
Cu 2 ZnSnS 4 (CZTS), with a direct bandgap of 1.5 eV, is a primary candidate material for solar energy conversion applied in both photovoltaics and photocatalysis due to its tremendous reserves and environmental friendly components. Though the utilization of CZTS with phases of kesterite and wurtzite are extensive, until now, the synthesis and growth procedure of both phases are not clearly understood. In this work, we succeed in synthesizing CZTS microspheres with controlled phase through a facile method—ultrasonic spray pyrolysis (USP). By choosing ammonium thioglycolate and l -cysteine as sulfur source, which were found to be the key factor in the phase formation process, CZTS microspheres can be prepared in kesterite phase and wurtzite phase, respectively. After exposing the prepared CZTS microspheres under the Xe lamp irradiation, we found an apparently phase-dependent photocatalytic hydrogen evolution, in which the performance of kesterite phase CZTS sample was almost 2 times as high as that of wurtzite CZTS sample.
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高影响因子
AICHE JOURNAL
·
2021
·Vol. 67
·期 6
·e17197
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IF 3.993
Liyun Huang,Kui Wu,Qian He,Chao Xiong,Tao Gan,Xiaohui He,Hongbing Ji
Single atom catalysts (SACs), featured with atomically dispersed metal species, have been considered as one of the most promising catalytic materials because of the excellent performance in various high-value-added reactions. However, the large-scale and continuous-type production of such SACs is still challenging. Herein, a novel and facile microcapsule strategy for the quasi-continuous synthesis of iron SACs supported on S, N co-doped carbon (Fe/SNC) is developed, and the Fe species are presented as isolated active sites and stabilized as the FeN 3 S-like structure. The as-prepared Fe/SNC catalysts exhibit excellent catalytic properties for selective oxidation of arylalkanes, which followed pseudo-first-order kinetics with an E a = 41.5 kJ/mol. More importantly, the two Fe/SNC catalysts synthesized at different continuous times showed essentially identical catalyst structure and catalytic performance, demonstrating the superior reliability of our microcapsule strategy for the quasi-continuous production of SACs, which can be easily scaled up to industrial application.
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高影响因子
INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH
·
2020
·
IF 3.573
Zhirong Yang,Jing Zhang,Jiejie Huang,Gang Qian,Xuezhi Duan,Xinggui Zhou
To promote biomass-derived tar and coke upgrading, biomass pyrolysis intensification was utilized by the co-pyrolysis of biomass and caking coal with suitable particle size. The intensification led to a 15% increase in light tar fraction in tar, indicating a transformation from heavy tar to light components (phenols, aliphatic hydrocarbons). Moreover, the resulting coke achieved high strength (M25 > 80%) that can meet the requirement for moving bed gasification. To further facilitate tar upgrading and alleviate secondary reactions of volatiles that result in more secondary-coke and less gas, calcium-based Ca@Cu catalysts were synthesized and then loaded along the predicted coke cracks to improve tar quality without compromising coke granularity and strength. The results indicated that the catalytic upgrading mitigated the formation of pyrolytic water and secondary-coke, and dramatically improved tar quality as the light tar fraction in tar increased by 15–30%. Specifically, the upgraded light tar contains more phenols, naphthalenes, and anthracenes but less acids, ketones, and furfurals. It was postulated that selective cleavage of oxygen-containing functional groups (mainly ether bonds) promoted tar reconstruction to release more light aromatics during the catalysis. The coke strength continued to increase by 3–6%, possibly due to mitigation of H2O formation as indicated by more oxygen-containing groups retained in the aromatics during the Ca@Cu catalysis. The current study provided a new strategy to simultaneously upgrade coke and tar during catalytic pyrolysis of biomass for efficient utilization of the biomass.
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高影响因子
BIORESOURCE TECHNOLOGY
·
2020
·
IF 7.539
Yong Huang,Shasha Liu,Muhammad Asif Akhtar,Bin Li,Jianbin Zhou,Shu Zhang,Hong Zhang
To understand the potential origin of char activity responsible for volatile evolution during biomass pyrolysis, the interactions between benzyl phenyl ether (BPE, a typical lignin dimer) and pinewood chars prepared under a series of thermal, acidy, and steamy conditions were investigated. The results showed the activity of low-temperature char on BPE conversion was mainly attributed to the surface O-containing functional groups. The BPE conversion decreased as the temperature for char preparation raised, resulting from the elimination of char surface functional groups to a large degree at high temperature. The low activity of high-temperature char on BPE conversion could be recovered by acid-washing to release metal-occupied carbon based active sites (e.g., small aromatic rings), and further promoted by steam activation to modify the surface property and porous structure, finally achieving a full conversion of BPE and high selectivity to the products of phenol and toluene.
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PubMed
高影响因子
ENERGY
·
2019
·
IF 5.537
Shuai Guo,Tiecheng Liu,Jicheng Hui,Deyong Che,Xingcan Li,Baizhong Sun,Shaohua Li
The addition of CaO has been used to reduce the harmful NO x precursors (NH 3 and HCN) generated by the pyrolysis of municipal sewage sludge . However, the underlying reduction mechanism remains unclear. To address this issue, we systematically investigated the effects of temperature and CaO addition on the generation of NH 3 and HCN during the pyrolysis of sludge protein and a model protein. With increasing temperature from 300 to 900 °C, the inhibitory effect of CaO on NH 3 emission was observed to fluctuate, maximizing at 400 °C. The inhibition was attributed to the reaction of CaO with nitrogen in the produced char to form CaC x N y , resulting in enhanced fixation of the char pyridines and nitriles. The nitriles exhibited high thermal stability and inertness to CaO. The increased nitrile content at high temperatures was attributed to the formation of the species from amines and N-containing heterocycles . The CaC x produced by the thermal decomposition of CaC x N y above 700 °C was found to increase P–N fixation and decrease NH 3 formation. The observed poor inhibitory effect of CaO on NO x precursor formation at 650 °C was attributed to the production of NH 3 via HCN hydrolysis. Because HCN directly reacted with CaO, the inhibition of HCN formation was highest at 650–900 °C, preventing the conversion of char nitriles into HCN.
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高影响因子
Waste and Biomass Valorization
·
2016
·Vol. 9
·期 1
·123-130
·
IF 0.915
Cheng Xu,Tang Yijing,Wang Biao,Jiang Jianming
The utilization of waste rice husks for biochar production has received much attention due to the energy concerns and environmental issues. But how to increase the charcoal yield and quality remains a big challenge. In this work, a two-step pyrolysis of rice husks was carried out at atmospheric pressure, consisting of a first low heating rate step followed by a high heating rate step. The effects of operation conditions at each step, including temperature, heating rate and residence time, on changes in charcoal yield and quality based on fixed-carbon yield were investigated. At the first step, switch temperature and heating rate were the predominant factors that influenced charcoal and fixed-carbon yields. The increase of charcoal and fixed-carbon yields at the first step was attributed to the rate-determined decomposition of hemicellulose. Therefore, the switch temperature should be set at those lower than the decomposition temperature of celluloses. However, at the second step, decreasing final pyrolysis temperature and shortening residence time benefited the increase of charcoal yields. Whereas, a maximum value of fixed-carbon yield was observed at the final pyrolysis temperature of 600 °C, which could result from the aromatics formed from cellulose-derived volatiles. Therefore, the switch temperature should be lower than cellulose decomposition temperature in order to reduce the cycle time for biochar production. Moreover, the charcoal and fixed-carbon yields obtained by the optimized two-step pyrolysis were higher than those by one-step pyrolysis.
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高影响因子
危险品化学品经营许可证（带存储）