ACS Catalysis
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2021
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IF 13.084
Jinqiu Guo,Zongjing Feng,Jun Xu,Jie Zhu,Guanghui Zhang,Yaping Du,Hongbo Zhang,Chunhua Yan
Ethanol transformation with high product selectivity is a great challenge, especially for high weight molecules. Here, we show a combination study of kinetic, thermodynamic, and in situ spectroscopy measurements to probe the selective upgrading of ethanol over lamellar Ce(OH)SO4·xH2O catalysts, with 60–70% Ce3+ preserved during the catalysis. High methyl phenols (MPs) selectivity at ∼80% within condensation products was achieved at ∼50% condensation yield (3.0 kPa C2H5OH, 15 kPa H2, Ar balanced, 693 K, 1 atm, gas hourly space velocity (GHSV) ∼5.4 min–1), with acetaldehyde, acetone, 4-heptanone, and 2-pentanone as the key reaction intermediates. Kinetic measurements with the assistance of isotope labeling proved that MPs generated from the kinetically relevant step (KRS) of C–C bond coupling of enolate nucleophilically attacks surface C2H4O following a Langmuir–Hinshelwood model. Low ethanol and water pressures and high acetaldehyde and hydrogen pressures were proved to be favored for MPs generation rather than dehydration, in which hydrogen could reduce the amount of lattice oxygen and facilitate the preparation of MPs while water and ethanol both compete with acetaldehyde for active sites during catalysis. On the basis of in situ X-ray diffraction (XRD), quasi-in situ X-ray photoelectron spectroscopy (XPS), and Raman characterizations, the Ce(OH)SO4 crystal structure was proved to be maintained along with ethanol activation, and the Ce3+–OH Lewis acid–base pair was proved to be the active species for the selective C–C bond coupling. The KRS assumption was also supported by the apparent activation energy assessment within the reaction network on dehydration, dehydrogenation, aldol condensation, and cyclization and a series of negligible kinetic isotope effects (KIEs). This system can be easily extended to some other systems related to C–C bond coupling and is attracting attention on converting oxygenate platform molecules over lanthanide species.
研究领域:
化学工程
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催化
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材料科学
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物理化学
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产品关联
DOI
高影响因子
CHEMICAL ENGINEERING JOURNAL
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2019
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IF 8.355
Shizong Wang,Jianlong Wang
Coking wastewater concentrate (CWC) generated during the membrane filtration process is difficult to treat mainly due to its higher chloridion concentration. Advanced oxidation process is ineffective in treating CWC because of the quenching effect of chloridion on hydroxyl radicals. In this study, peroxymonosulfate (PMS)/chloridion process was developed to treat CWC, and 2,4-dimethyphenol (DMP) was selected as targeted pollutant to investigate the reaction mechanism of PMS/chloridion process. Unlike the traditional view that hypochloride acids are the main active species during the PMS/chloridion process, it was found that singlet oxygen, hypochloric acids and chlorine radicals contributed to the degradation of DMP, which was evidenced by the quenching experiments, electron paramagnetic resonance spectroscopy and identified degradation products. Based on the degradation products, the possible degradation pathway of DMP was tentatively proposed. The PMS/chloridion process can be applied in a wide pH range from 3 to 8. The optimal ratio of PMS to chloridion was 1:1 for mineralizing DMP in which the maximum mineralization of DMP reached 33.3%. The PMS/chloridion process can effectively remove COD and colourity of actual CWC. However, the ratio of PMS to chloridion varied with the initial COD concentration of CWC. This study provides a novel treatment process for CWC, and an insight into the removal mechanism of the PMS/chloridion process.
研究领域:
环境工程
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化学工程
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废水处理
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产品关联
DOI
高影响因子
ENVIRONMENTAL SCIENCE & TECHNOLOGY
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2018
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IF 6.653
Yuan Chen,Xu Zhang,Shixiang Feng
Contributions of excited triplet state of humic acid (3HA*) and superoxide radical anion (O2•–), which is mainly generated via the reaction of O2 with HA-derived reducing intermediates (HA•–), to phenol transformation were revealed using acetaminophen, 2,4,6-trimethylphenol and tyrosine as probe molecules. Phenol transformation was initiated by 3HA*, leading to the formation of the phenoxyl radical (PhO•), but the distribution of transformation intermediates was codetermined by 3HA* and HA•–. The influence of HA•– essentially resulted from the production of O2•–, which affected the fate of PhO•. PhO• could undergo dimerization, or react with O2•–, leading to either phenol peroxide formation (radical addition) or phenol regeneration (electron transfer). In addition, PhO• could bind to HA or react with HA radicals, particularly in the absence of O2 and O2•–. These PhO• reactions were dependent on the reduction potential and structure of PhO•. This study also proved that the reaction of phenol with 1O2 and the reaction of PhO• with O2•– lead to the same oxidation product. The contributions of 3HA* and its generated 1O2, HA•– and its generated O2•– to phenol transformation were pH-dependent.
研究领域:
环境化学
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物理化学
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分析化学
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产品关联
DOI
PubMed
高影响因子
ENVIRONMENTAL POLLUTION
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2021
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IF 8.071
Belay Tafa Oba,Xuehao Zheng,Moses Akintayo Aborisade,Ashenafi Yohannes Battamo,Akash Kumar,Sheila Kavwenje,Jiashu Liu,Peizhe Sun,Yongkui Yang,Lin Zhao
Calcium peroxide (CaO 2 ) has been proven to oxidize various organic pollutants when they exist as a single class of compounds. However, there is a lack of research on the potential of unactivated CaO 2 to treat mixed chlorinated organic pollutants in soils. This study examined the potential of CaO 2 in treating soils co-contaminated with p-dichlorobenzene (p-DCB) and p-chloromethane cresol (PCMC). The effects of CaO 2 dosage and treatment duration on the rate of degradation were investigated. Furthermore, the collateral effects of the treatment on treated soil characteristics were studied. The result showed that unactivated CaO 2 could oxidize mixed chlorinated organic compounds in wet soils. More than 69% of the pollutants in the wet soil were mineralized following 21 days of treatment with 3% (w/w) CaO 2 . The hydroxyl radicals played a significant role in the degradation process among the other decomposition products of hydrogen peroxide. Following the oxidation process, the treated soil pH was increased due to the formation of calcium hydroxide. Soil organic matter , cation exchange capacity, soil organic carbon , total nitrogen, and certain soil enzyme activities of the treated soil were decreased. However, the collateral effects of the system on electrical conductivity, available phosphorus, and particle size distribution of the treated soil were not significant. Likewise, since no significant release of heavy metals was seen in the treated soil matrix, the likelihood of metal ions as co-pollutants after treatment was low. Therefore, CaO 2 can be a better alternative for treating industrial sites co-contaminated with chlorinated organic compounds.
研究领域:
环境科学
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土壤化学
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污染控制
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DOI
高影响因子
Journal of Cleaner Production
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2024
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IF 9.7
Jialiang Yang,Leilei Cheng,Jing Gu,Shaonan Tian,Jun Yang,Taoli Huhe,Haoran Yuan,Yong Chen
The pyrolysis products of epoxy resin consist of mixed phenolic compounds, which can be transformed into methylated phenolic compounds, pentamethylbenzene, hexamethylbenzene, and other high-value chemicals through methylation. However, the mechanism of methylation for pyrolysis products of epoxy resin remains unclear. In this study, using thermosetting epoxy resin and waste wind turbine blades as feedstocks, we investigated the methylation performance of different solid acid catalysts (γ-Al 2 O 3 , α-Al 2 O 3 , ZSM-5, MCM-41) through a pyrolysis-methylation cascade reactor. The study unveils the impact of reaction temperature and reaction time on the pyrolysis reaction and the product distribution. The optimal reaction parameters are determined to be 500 °C and a reaction time of 20 min. Under these conditions, the reforming products exhibited the highest selectivity for methylated phenolic compounds and hexamethylbenzene (42.57 wt%). The proposed methyl substitution reaction pathway for isopropenylphenol was supported by a 13 C methanol isotope experiment. On nanoscale γ-Al 2 O 3 catalyst, the methylation reaction displays a non-position-selective methylation pattern. Methyl substitution occurs by directly replacing the methylating agent on the isopropyl/isopropenyl group, leading to the breaking of the C arom -C aliph bond. Additionally, Density Functional Theory (DFT) simulations reveal that methyl serves as an intermediate in the methylation substitution reaction. The study also conducted a material flow assessment for the recycling of epoxy resin waste through the pyrolysis-methylation pathway.
研究领域:
材料科学
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化学工程
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环境科学
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催化
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可再生能源
✓ 已验证
产品关联
DOI
高影响因子
危险品化学品经营许可证（带存储）