Catalysts
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2016
·Vol. 6
·期 2
·19
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IF 2.964
Guozhu Liu,Yunxia Zhao,Jinhua Guo
High selectively catalytic conversion of lignin-based phenols (m-cresol,p-cresol, and guaiacol) intopara-/m-xylene was performed over Pt/HZSM-5 through hydrodeoxygenation andin situmethylation with methanol. It is found that thep-/m-xylene selectivity is uniformly higher than 21%, and even increase up to 33.5% form-cresol (with phenols/methanol molar ratio of 1/8). The improvedp-/m-xylene selectivity in presence of methanol is attributed to the combined reaction pathways: methylation ofm-cresol into xylenols followed by HDO intop-/m-xylene, and HDO ofm-cresol into toluene followed by methylation intop-/m-xylene. Comparison of the product distribution over a series of catalysts indicates that both metals and supporters have distinct effect on thep-/m-xylene selectivity.Keywords:m-cresol;hydrodeoxygenation;methanol;p-/m-xylene;methylation
研究领域:
化学工程
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催化科学
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高影响因子
Chemical Engineering and Processing-Process Intensification
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2017
·
IF 2.234
Haofan Yang,Yufeng Hu
The separation of para -xylene ( p -xylene) from its mixtures with meta -xylene ( m -xylene) using aqueous hydroxypropyl- β -cyclodextrin (HP- β -CD) solution by a two-step liquid–liquid extraction process has been experimentally investigated. The results show that HP- β -CD can form inclusion complexes of different strengthes with p -xylene and m -xylene. It is shown that the different strengthes stem from the differences in size, relative alkalinity and dipole moment between the two xylene isomers. The optimum separation condition has been determined as follows: the concentrations of HP- β -CD and initial xylene mixture are 0.1448 g (g H 2 O) −1 and 0.4 g (g H 2 O) −1 , respectively. Under this condition, the separation factor α, which is the most important evaluation index in extraction process, is 1.469. The ratio of the formation constants, K PX / K MX , has been determined to be slightly greater than α, consistent with the theoretical prediction. Moreover, a new method for calculation of α has been developed. The experimental results demonstrate the almost perfect reusability of aqueous HP- β -CD solution. For the experiment that begins with a 1:1 mixture of p -xylene and m -xylene, the p -xylene concentration in the extraction phase is 59.71 wt%. After repeating the extraction process 4 times, the concentration of p -xylene in the extraction phase can reach 81.48 wt%.
研究领域:
化学工程
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分离科学
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DOI
高影响因子
Catalysis Science & Technology
·
2023
·Vol. 13
·期 10
·3060-3068
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IF 5
Guanghua Liang,Jianyi Chen,Tao Dou,Zhijie Wu,Xiaofeng Li,Yuanshuai Liu
EU-1 zeolite is employed as an active component of a catalyst for isomerization or hydroisomerization of C8 aromatics (i.e., xylenes, ethylbenzene) in petrochemical processes to increase the para-xylene yield. However, conventional manufacturing of EU-1-based catalysts involves the production of mother liquors for zeolite synthesis which usually contain plentiful unreacted raw materials, or the negative impact of incorporated binders in mass transfer during reactions over shaped catalysts. Herein, we developed a novel route to prepare the monolithic EU-1 zeolite, and used it as an active component of a catalyst for hydroisomerization of ethylbenzene with meta-xylene. Recrystallization of the shaped zeolite precursors composed of incompletely crystallized zeolites with amorphous silica and alumina powders as binders in recycled mother liquor led to formation of the monolithic EU-1 zeolite. Transformation of binder species to a full-zeolitic phase was corroborated comprehensively by characterization methods. Compared with the conventionally fabricated counterpart, the monolithic EU-1 zeolite possessed similar mechanical strength, high crystallinity, and high acidity and, in particular, enhanced mesoporosity, which led to improved catalytic performances in hydroisomerization reactions. Our developed synthetic strategy provides an effective way to produce the monolithic EU-1 zeolite, but is also a reference for the sustainable production of other types of zeolitic materials for energy-related applications.
研究领域:
化学工程
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催化材料科学
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DOI
高影响因子
PROCESS SAFETY AND ENVIRONMENTAL PROTECTION
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2023
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IF 7.8
Hang Yao,Gang Fu,Yuqing Ni,Lei Ni,Juncheng Jiang,Han Zhang,Zhen Cheng,Zhiquan Chen
Nitro-m-xylenes (NMX) was synthesized in semi-batch mode via m-xylene nitration using nitric acid-acetic anhydride (HNO 3 -Ac 2 O) as nitrating reagent in this work. The nitration process was optimized by response surface methodology . The yield of NMX could reach 92.40% under the optimal conditions of jacket temperature of 20 °C, 0.15 mol of HNO 3 and 0.19 mol of Ac 2 O. Corresponding large reaction enthalpy (Δ H =240.9 kJ/mol) and adiabatic temperature rise (Δ T ad,r =398.1 K) indicated the serious hazards of nitration in a thermal runaway scenario. Pyrolysis of nitration products occurred at about 320–400 °C by differential scanning calorimetry tests. The reaction order of the pyrolysis was determined to be 1.2 by adiabatic kinetic analysis . Thermal risk of the nitration process was assessed to be acceptable and level 1 via the risk matrix and Stoessel criticality diagram analyses, respectively. Furthermore, detailed nitration mechanisms for NO 2 + generation and aromatic substitution were presented. The activation free enthalpy and free energy parameters for each step were calculated by density functional theory (DFT). These findings can help understand the exothermic sources of m-xylene nitration and guide the intrinsically safer design and scale-up of the process.
研究领域:
化学工程
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安全科学
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理论化学
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DOI
高影响因子
JOURNAL OF SOLUTION CHEMISTRY
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2023
·Vol. 52
·期 7
·762-789
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IF 1.2
Li Min,Zhang Xiaocheng,Yu Yingmin,Liu Lanmu
The extractive distillation was used to separate ethylbenzene and m-xylene. After the solvent screening, 1,2,4-trichlorobenzene was chosen as the extractive solvent. The vapor–liquid equilibrium (VLE) of binary mixtures of m-xylene, ethylbenzene, and 1,2,4-trichlorobenzene was measured at 101.33 kPa. The measurements were taken with a modified Rose equilibrium still. The Wisniak’s test was used to assess the thermodynamic consistency of the VLE experimental results. To obtain the binary interaction parameters, the binary VLE experimental data were correlated with the NRTL, Wilson, and UNIQUAC activity coefficient models. The results showed that three models all fit the experimental values of three binary systems well, and the ternary VLE data of m-xylene + ethylbenzene + 1,2,4-trichlorobenzene were estimated using Aspen Plus V11 based on these model parameters. The experimental data agree well with the estimation values generated from three models. Finally, the effect of 1,2,4-trichlorobenzene as an extractant was analyzed, and it is proved to have a good influence on the separation of ethylbenzene from mixed xylenes by extractive distillation.
研究领域:
化学工程
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分离技术
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DOI
高影响因子
JOURNAL OF MOLECULAR LIQUIDS
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2024
·
IF 5.3
Hang Yao,Jialei Huang,Yuqing Ni,Gang Fu,Lei Ni,Juncheng Jiang,Yong Pan
Selection of appropriate solvents is of great significance for achieving efficient and safe m-xylene nitration . In this study, the exothermic behavior of m-xylene nitration under twelve organic solvents were studied by reaction calorimetry. The process hazards were assessed by calculation of thermal safety parameters. The reaction selectivity was quantified. The anhydrides exhibited the prominent promotion as water absorbent and active reagent in nitration, followed by selected aliphatic hydrocarbons, chlorinated hydrocarbons. While acetic acid, propionic acid and ethyl acetate had negative effects. The maximum yield of 95.6 % was achieved in nitric acid-acetic anhydride (HNO 3 -Ac 2 O) system. The thermal weight loss of the products appeared at around 150−230 °C by thermogravimetry experiments. The activation energy was determined to be 192.9 kJ/mol through adiabatic kinetic calculations. Furthermore, the solvent effects were analyzed by calculating the solvent polarity and its interaction energy with HNO 3 . The different action mechanisms of Ac 2 O and Pc 2 O on NO 2 + generation were revealed. The density functional theory calculations were in agreement with the experimental results. These findings can provide guidance for understanding of the solvent effect on the reaction hazards and selectivity of m-xylene nitration, and provide experimental and theoretical basis for solvent screening for the nitration of similar aromatic compounds.
研究领域:
化学工程
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理论化学
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DOI
高影响因子
SEPARATION AND PURIFICATION TECHNOLOGY
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2025
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IF 9
Wei Chen,Pengfei Wang,Weike Jia,Huidan Zeng
Silicalite-1 zeolites/polymer composite membranes are among the most reliable materials for the pervaporation separation of m-X from xylene isomers. However, the separation factors of the present silicalite-1 zeolites/polymer composite membrane are low. This work has succeeded in fabricating dense and defect-free silicalite-1/PVA composite membrane for first improving the pervaporation separation performance of m-X/p-X isomers. The silicalite-1/PVA composite membrane was prepared by combining solution scraping and vacuum thermal crosslinking methods with fumaric acid as a crosslinker (denoted as silicalite-1/PVA-V). The silicalite-1/PVA-V composite membrane with a thickness of 15.3 μm, prepared with a fumaric acid/monomeric unit of PVA molar ratio of 0.05 after vacuum thermal crosslinking at 160 ℃ for 2 h, exhibited dense and defect-free structure with extremely low xylene swelling degree, good structural stability and mechanical properties as well as excellent pervaporation separation performance. Compared to the pure PVA membrane, the silicalite-1/PVA-V composite membrane exhibited better selective separation performance of m-X isomer. The temperature, amount of fumaric acid, crosslinking degree and membrane thickness significantly influenced the pervaporation separation performance. The optimum selective separation factor of m-X/p-X isomers and the corresponding total permeate flux were about 9.85 and 59.15 g·m −2 ·h −1 (60 ℃), respectively. The pervaporation experiments of long-time and repetitively prepared membrane demonstrated that the silicalite-1/PVA-V composite membrane had long-term structural stability and reproducibility. To demonstrate scalability, we showed that our strategy could produce large-size silicalite-1/PVA-V composite membrane with an area of 1000 cm 2 , which exhibited m-X separation performance similar to that of small membrane coupons. The present work provided a potentially scalable method for producing high-quality silicalite-1/PVA composite membrane for enhancing the pervaporation separation performance of m-X from xylene isomers.
研究领域:
材料科学
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化学工程
✓ 已验证
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DOI
高影响因子
JOURNAL OF MOLECULAR LIQUIDS
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2024
·
IF 5.3
Hang Yao,Jialei Huang,Yuqing Ni,Zhen Cheng,Gang Fu,Lei Ni,Juncheng Jiang,Yong Pan
Five imidazole based SO 3 H-functionalized ionic liquids (SFILs) with different anions were selected as catalysts to achieve efficient m-xylene nitration. The acidity and thermal stability of the ILs were characterized by UV–vis and thermogravimetry. The reaction selectivity of the m-xylene nitration catalyzed by five ILs was compared. [MIMBs]HSO 4 had the best catalytic activity with the maximum yield of 98.1 %. The effect of ILs on the exothermic behavior of m-xylene nitration was explored by reaction calorimeter. The reaction enthalpy (Δ H ) and adiabatic temperature rise (Δ T ad ) were calculated to evaluate process hazards. The reaction order for the decomposition of different nitration products under adiabatic conditions was essentially close to 1. The process risk level for m-xylene nitration with the introduction of selected ILs was essentially downgraded from conditionally acceptable to acceptable, and the criticality was reduced from class 3 to 1. Furthermore, the acidic active sites of the ILs were predicted by the electrostatic potential. The solubility of m-xylene in the IL was investigated through the calculation of interaction energy. The roles of ILs as solvents and catalysts in nitration were resolved by density functional theory calculations. These findings could contribute to the understanding of the effect of ILs in modulating the process hazards and improving the selectivity of m-xylene nitration, and provide theoretical guidance for elucidating the catalytic mechanism of ILs in nitration.
研究领域:
化学工程
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催化化学
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DOI
高影响因子
JOURNAL OF CHEMICAL THERMODYNAMICS
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2015
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IF 2.679
Xianyang Meng,Xiaoyun Gu,Jiangtao Wu,Velisa Vesovic
The compressed liquid viscosities of ortho -xylene, meta -xylene, para -xylene and ethylbenzene were measured using a vibrating-wire viscometer at different temperatures and pressures. The measurements were performed over the temperature ranges of (273 to 373) K for o -xylene and m -xylene, (293 to 373) K for p -xylene and (253 to 373) K for ethylbenzene, at pressures from (0.1 to 30) MPa, except for ethylbenzene for which the pressure range was up to 35 MPa. The combined expanded uncertainty of the reported viscosity is better than 2% with a confidence level of 0.95 ( k = 2). The experimental data were correlated with the empirical Andrade–Tait equation which reproduced the results with the average absolute percentage deviations of (0.25, 0.15, 0.16 and 0.23)% for o -xylene, m -xylene, p -xylene and ethylbenzene, respectively. The present results are in good agreement with most of the literature values.
研究领域:
化学工程
·
物理化学
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DOI
高影响因子
MICROPOROUS AND MESOPOROUS MATERIALS
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2024
·
IF 4.8
Wei Chen,Pengfei Wang,Weike Jia,Huidan Zeng
Improving the zeolite adsorption separation efficiency of individual xylene isomer with high purity from their mixture is still a pressing challenge in the fine chemical industry. Herein, plate-like silicalite-1 (p-S-1) zeolite crystals with short b-axis thickness have been successfully synthesized by combination of tributylphosphine oxide (TBPO) modifier and F − -assisted crystallization method to first investigate the separation property of xylene isomers. The morphology and structure of the p-S-1 zeolite crystals were characterized by XRD, FTIR, BET, SEM and TEM. The results showed that the p-S-1 zeolite crystals with thickness of about 50 nm along the b-axis and high crystallinity, as well as extremely rich micropores, were obtained by crystallizing the gels with TBPO/SiO 2 ≥ 0.04. By static adsorption experiment and fixed bed experiment, xylene isomers selective adsorption separation property of the p-S-1 zeolite crystals prepared at TBPO/SiO 2 = 0.04 was investigated. The static adsorption experiment demonstrated that the p-S-1 zeolite crystals exhibited higher adsorption capacity of p-xylene (p-X) and more excellent xylene isomers separation performance than that of the bulk coffin-shaped silicalite-1 (c-S-1) zeolite crystals because of the shorter mass transfer channel and larger diffusivity differences between p-X and o-X/m-X/EB. The dynamic adsorption experiment in simulated five-component solutions diluted by isooctane (IO) indicated that the p-S-1 zeolite crystals had excellent xylene isomers selective adsorption separation performance. The optimum dynamic xylene isomers selective adsorption separation factors for p-X/o-X, p-X/m-X and p-X/EB were 25.41, 36.45 and 11.57 at 150 °C, respectively. The regeneration experiment also indicated that the p-S-1 zeolite crystals had more stable structure and longer lifetime. This work suggested that the p-S-1 zeolite crystals had great potential as new adsorbent for selective adsorption separation of xylene isomers.
研究领域:
材料科学
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化学工程
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DOI
高影响因子
COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS
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2024
·
IF 4.9
Shu-Huan Chen,Huma Javeria,Xu-Hui Sun,Zhen-Xia Du
With the proliferation of vehicles in households, people are spending more and more time in their cars, so it is important to ensure the air quality and safety of the car. In this research, environmentally friendly, green PET@PDA@MIL-101(Fe) (PPM) was prepared by in-situ solvothermal growth and acid etching methods, which was categorized by SEM, FTIR, XRD, XPS, and BET. PPM was used to adsorb benzene, toluene, and m-xylene at low concentrations. The maximum amount of adsorption of PET@PDA@MIL-101(Fe) (PPM) for benzene, toluene, and m-xylene was 68.72 mg/g, 91.63 mg/g, and 78.47 mg/g respectively. The adsorption process of PPM is well fitted by the pseudo-first-order kinetic model and Langmuir isothermal adsorption model. Furthermore, PPM exhibited excellent toluene removal performance in simulated vehicles and excellent cycling capability in adsorption-desorption experiments. As a result, PPM can be used to treat and manage toluene volatile organic compounds (VOCs) at low concentrations.
研究领域:
环境科学
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材料科学
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化学工程
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产品关联
DOI
高影响因子
Environmental Science-Water Research & Technology
·
2024
·
IF 3.5
Jingwei Wang,Shuang Shan,Jihong Song,Da Li,Qiao Ma,Shuzhen Li
With the expanding use of antibacterial and disinfection products, chloroxylenol (para-chloro-meta-xylenol, PCMX) has been detected in various environments, especially in sewage treatment plants. However, the influence of PCMX has received limited attention, with only sporadic studies available. Over a period of 110 days, efforts were undertaken to restore the performance of PCMX-affected anaerobic sludge through the addition of nanoscale zero-valent iron (nZVI) and the reduction of PCMX concentration. nZVI addition promoted COD removal efficiency under a high PCMX concentration (50.0 mg L−1, GH) and accelerated the anaerobic digestion process under a low PCMX concentration (0.5 mg L−1, GL). The slow recovery in GH highlighted the difficulty in restoring the functionality of municipal anaerobic sludge under the prolonged influence of high PCMX concentrations. Microbial communities exhibited distinct succession patterns under different treatments. nZVI demonstrated efficacy in mitigating the decline in microbial richness induced by PCMX. Shannon and Pielou evenness and niche breadth increased as the PCMX concentration decreased, suggesting an enhanced restorative capacity of the microbial community when alleviating the stress imposed by PCMX. Bacteroidetes, Proteobacteria, Actinobacteria, Firmicutes, and Chloroflexi were predominant functional phyla in the anaerobic digestion process. Olsenella, Rectinema, Desulfovibrio, Azonexus, and Methanobacterium were key genera responding to nZVI and PCMX. PCMX markedly diminished community resistance and resilience, while nZVI mitigated the damage of PCMX on community stability. Altogether, this study contributes to a better understanding of the performance and microbial succession in anaerobic sludge through the addition of nZVI and variations in PCMX concentration.
研究领域:
环境科学
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微生物学
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DOI
高影响因子
危险品化学品经营许可证（带存储）