Catalysis Science & Technology
·
2017
·Vol. 7
·期 24
·6000-6012
·
IF 5.773
Wenfeng Han,Chunpeng Zhang,Haili Wang,Shenglan Zhou,Haodong Tang,Luteng Yang,Zhikun Wang
Hydrofluorocarbons (HFCs) which are usually potent greenhouse gases are regulated by the Montreal Protocol and its amendments, especially the recent Kigali Amendment. Dehydrofluorination of HFCs is an efficient route for the conversion of these greenhouse gases to value added and environmentally benign chemicals. Although AlF3 with strong Lewis acidity catalyzes dehydrofluorination, it also favors carbon deposition. MgF2 with weak acidity inhibits coking significantly. Unfortunately, MgF2 sinters dramatically at temperatures below 300 °C leading to the low activity for dehydrofluorination. In the present work, we report that sub-nano MgF2 embedded in carbon fibers and electrospun MgF2 fibers prevent sintering of MgF2 during dehydrofluorination reaction. Via simple and one-step electrospinning and calcination in a N2 (for embedded MgF2) or air (for MgF2 fibers) atmosphere, embedded MgF2 with particle sizes between 3–6 nm and pure MgF2 fibers with diameters of around 100 nm were fabricated. No sintering was observed following reaction at 450 °C. The fine MgF2 particles and MgF2 fibers facilitate the formation of under coordinated Mg species in MgF2 which are the weak acid sites. By embedding MgF2 or fabrication of MgF2 fibers, weak acid sites are increased significantly, while strong acid sites remain almost unchanged. Hence, they show significantly higher reaction rates than MgF2 prepared by precipitation of Mg(CH3COO)2·4H2O with NH4F for the dehydrofluorination of 1,1,1-trifluoroethane (HFC-143a) to VDF (CH2CF2) at 450 °C.
研究领域:
材料科学
·
催化化学
✓ 已验证
产品关联
DOI
高影响因子
CATALYSIS COMMUNICATIONS
·
2020
·
IF 3.612
Jiaqin Lu,Wenfeng Han,Wei Yu,Yongnan Liu,Hong Yang,Bing Liu,Haodong Tang,Ying Li
Aluminum fluoride (AlF 3 ) is a typical catalyst for dehydrofluorination of hydrofluorocarbons (HFCs) to fluoroolefins with high heat of reaction. Consequently, heat supply and sintering are the key challenges for AlF 3 -based catalysts. Herein, SiC with high thermal conductivity and resistance to HF corrosion is suggested as a candidate support of AlF 3 catalyst. The interaction between AlF 3 and SiC leads to uniform distribution of the catalytic phase, and as a result of this, AlF 3 /SiC exhibits high catalytic activity and stability for the dehydrofluorination of 1,1-difluoroethane to vinyl fluoride. This study proposes a novel catalyst support (SiC) for strong endothermic catalytic reactions involving HFCs for the first time to the best of our knowledge.
研究领域:
化学工程
·
材料科学
✓ 已验证
DOI
高影响因子
JOURNAL OF FLUORINE CHEMISTRY
·
2024
·
IF 1.7
Xiaoli Wei,Yiwei Sun,Jianhai Jiang,Zhen Wang,Wei Zhang,Bing Liu,Shucheng Wang,Xiaodan Yang,Wanjin Yu,Jianjun Zhang,Wenfeng Han
Al 2 O 3 exhibits high activity for the resource utilization of potent greenhouse gases, hydrofluorocarbons via dehydrofluorination or F/Cl exchange. However, it experiences completely fluorination under corrosive HF environment, leading to thorough fluorination of F-Al-O active site into F-Al-F, accompanied with serious carbon deposition. In this work, we successfully confined Al 2 O 3 in SiC (Al 2 O 3 @SiC) via treating Al 2 O 3 /SiC under high temperatures (>800 °C). The results showed that different with simple loaded Al 2 O 3 (Al 2 O 3 /SiC), during high temperature treatment, reaction between Al 2 O 3 and SiC occurred, leading to the confinement effect. Then, contributed by the interaction, desired F-Al-O species could be stabilized on the surface of SiC. While for Al 2 O 3 /SiC, it thoroughly turned into AlF 3 under identical reactive conditions, leading to inferior stability during CH 3 CHF 2 dehydrofluorination. Furthermore, the reaction rate of 5 %Al 2 O 3 @SiC is nearly up to 4 folds higher than that of traditional AlF 3 . Facilitated by the suitable Lewis acid intensity, less carbon deposition formed on Al 2 O 3 @SiC. Thus, constructing strong interaction between F-Al-O and stable SiC provides a potential strategy to stabilize unstable active centers.
研究领域:
化学工程
·
环境科学
✓ 已验证
产品关联
DOI
高影响因子
CHEMICAL PHYSICS LETTERS
·
2023
·
IF 2.8
Wujian Zhang,Xiangdong Zhou,Hui Sun,Zhenxiang Li,Kangjun Wang,Panpan Zhang,Wenfeng Han,Ying Li,Haodong Tang
The activated alumina with different specific surface areas and different acidity was used to catalyze the dehydrofluorination reaction of CF 3 CH 2 F (HFC-134a). The catalytic performance of the alumina catalysts was rationalized by analyzing the relationship between specific surface area and acidity before and after fluorination. A series of physiochemical techniques, including Scanning Electron Microscope (SEM), X-ray diffraction (XRD), and N 2 physical adsorption (BET), were used to investigate the changes in catalyst structure and surface morphology before and after being tested for the dehydrofluorination reaction. The Al 2 O 3 catalyst prepared from the precipitation method (Al 2 O 3 -P) demonstrated the best stability among all the Al 2 O 3 catalysts. Results from XRD techniques showed that Al 2 O 3 catalysts were fully or partially fluorinated into AlF 3 after the dehydrofluorination reaction. Al 2 O 3 -B catalyst and Al 2 O 3 -S catalyst containing mainly α-AlF 3 deactivate easier than the Al 2 O 3 -P catalyst, which has primarily β-AlF 3 . In addition, it can be concluded the high surface area Al 2 O 3 -P catalyst still has the highest specific surface area and pore size when fluorinated to AlF 3 , while forming the β-AlF 3 crystalline phase. Therefore, it has the optimum catalytic performance for dehydrofluorination of HFC-134a. This provides a new idea for designing alumina catalysts with reasonable structure.
研究领域:
化学工程
·
催化科学
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF HAZARDOUS MATERIALS
·
2021
·
IF 10.588
Jiaxin Zhu,Yihua Chen,Yurong Gu,Hang Ma,Mingyue Hu,Xinlei Gao,Tongzhou Liu
The discharge of widely used per- and poly-fluorinated compounds (PFCs) leads to their environmental prevalence, bioaccumulation and biotoxicity; and attracts researches focusing on their treatment in wastewater. Electrochemical reductive treatment is a promising alternative due to its milder reaction conditions and easy operation. The feasibility of electrochemical reductive decomposition of PFOA using a Rh/Ni cathode was explored. The Rh/Ni cathode was fabricated by coating Rh 3+ on Ni foil through electrodeposition . The Rh coating was primarily elemental and in a Rh(111) crystalline form. PFOA decomposition and defluorination were observed when using the Rh/Ni cathode where DMF was the solvent and the cathode potential was −1.25 V. A hydrodefluorination reaction was considered having occurred. Because possessing d electrons and empty d orbitals, the Rh coating enhanced PFOA adsorption onto the cathode surface and facilitated C F bond activation through Rh···F interactions. Moreover, the Rh(111) crystal helped chemisorb the generated H* and supply it participating in PFOA decomposition. With the continuous interaction of cathode-supplied electrons, C F bond would ultimately dissociate and transform to C H bond by H* substitution. Adding FeCp 2 * as a supporting electrolyte enhanced PFOA decomposition by working as the shuttle facilitating PFOA migration to the cathode surface.
研究领域:
环境科学
·
电化学
·
污染治理
✓ 已验证
产品关联
DOI
PubMed
高影响因子
APPLIED SURFACE SCIENCE
·
2019
·
IF 5.155
Xiu-Xiu Fang,Wen-Min Liao,Jian-Dong Song,Wen-Zhi Jia,Yun Wang,Ji-Qing Lu,Meng-Fei Luo
A series of 3V-xFe/MgF 2 catalysts with different V/Fe molar ratios were prepared by a sol-gel method, and the effect of Fe promotion on the catalytic performance of gas-phase dehydrofluorination of 1,1,1,3,3-pentafluoropropane (HFC-245fa) was investigated. It was found that proper V/Fe ratio was helpful to improve the activity. The 3V-0.5Fe/MgF 2 catalyst (with a V/Fe ratio of 6/1) gave a HFC-245fa conversion of 76.6% at 320 °C, which was 13.4% higher than that on the 3V/MgF 2 (63.2%). The synergy between V and Fe species resulted in enhanced surface acidity which accounts for the enhanced activity. The VO x and FeO x species in the fresh catalyst could be transformed to VOF x and FeF 3 species during the reaction, which were regarded as the active sites. However, higher content of Fe in the catalyst resulted in the partial coverage of V species, which led to decline of surface acidity and thus the suppressed activity. Also, surface carbon deposition was responsible for the slight catalyst deactivation .
研究领域:
催化化学
·
材料科学
✓ 已验证
DOI
高影响因子
POLYMER DEGRADATION AND STABILITY
·
2018
·
IF 3.193
Donghan Li,Mingyi Liao
This study evaluates the dehydrofluorination of fluoroelastomer (poly(VDF-co-HFP) copolymer) which was dissolved by organic solvent and reacted with different concentrations of KOH and different amount of phase transfer catalyst (PTC) at 20–60 °C.The structures, sequence types and contents of double bonds of samples were analyzed and investigated by Attenuated Total Reflection Fourier Transform Infrared Spectroscopy(ATR-FTIR), 1 H nuclear magnetic resonance (NMR), 19 F NMR spectroscopy and chemical titration method. The results revealed that dehydrofluorination of the studied fluoroelastromers could be carried out at room temperature in alkaline environments, wherein the temperature and alkali concentration were the great factors. And the dehydrofluorination of poly(VDF-co-HFP) copolymer conformed mainly to Zaitsev's rule and partially to Hofmann's rule. The double bonds (–C=C–) would generate in five positions of molecular chains and contents could be controlled. With increase of alkali concentration or reaction temperature, there would be dehydrofluorination accompanied with oxidation reaction whereby some –C=C– converted to hydroxyl groups . Finally, the mechanism of reaction was also deduced.
研究领域:
材料化学
·
高分子科学
✓ 已验证
产品关联
DOI
高影响因子
WATER RESEARCH
·
2014
·
IF 5.323
Huajun Feng,Xueqin Zhang,Yuxiang Liang,Meizhen Wang,Dongsheng Shen,Yangcheng Ding,Baocheng Huang,Jiali Shentu
p -Fluoronitrobenzene ( p -FNB) tends to accumulate in industrial effluents because of its recalcitrant properties. Approaches to the removal of p -FNB always encounter conflicts between treatment efficiency and economic efficiency. A bioelectrochemical system (BES) was established to facilitate the removal and mineralization of p -FNB. The treatment cost was reduced by using inexpensive electrode materials and reducing the electrical energy used. p -FNB was effectively removed using the BES, and the reaction rate was higher than the sum of the rates of two control systems, i.e., a biological system (BS) and an electrocatalytic system (ECS), by a maximum of 62.9% under a voltage of 1.4 V. The voltage is a crucial kinetic factor for the BES performance; as the voltage increased from 0 to 1.4 V, the reaction rate constants for p -FNB removal and defluorination increased from 0.0520 to 0.1811 h −1 and 0 to 0.0107 h −1 . The synergistic effect of multistrains gave a TOC removal efficiency in the BES of about 34.05%, yet the removal efficiencies were low for the two control. The defluorination reaction rate was significantly slower than the p -FNB removal rate, which indicated that defluorination lagged p -FNB removal, and p -FNB transformation to p -fluoroaniline ( p -FA) was the fastest step. The electrochemical assistance provided electrons and accelerated the electron transfer rate in the microbial reduction of p -FNB to p -FA. In this study, the critical voltage for defluorination in the BES was 0.8 V, which was approximately 0.2 V lower than that in the ECS. The decrease in the critical voltage for defluorination was based on the production of p -FA, which is more electrocatalytically activated. These results demonstrate the mechanism of efficient p -FNB removal and mineralization in a BES.
研究领域:
环境科学
·
微生物学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
JOURNAL OF CATALYSIS
·
2018
·
IF 6.759
Jian-Dong Song,Tong-Yang Song,Ting-Ting Zhang,Yun Wang,Meng-Fei Luo,Ji-Qing Lu
A series of supported V 2 O 5 /MgF 2 catalysts were prepared and tested for dehydrofluorination of 1,1,1,3,3-pentafluoropropane (HFC-245fa) to synthesize 1,3,3,3-tetrafluoropropene (HFO-1234ze). The addition of V 2 O 5 in MgF 2 resulted in up to 5-fold increase in HFC-245fa conversion (from 19.2 to 95.2%) and much enhanced catalyst stability. Characterization results revealed that the dehydrofluorination initiated on the MgF 2 support triggered the transformation of V 2 O 5 to vanadium oxyfluoride (VOF x ) species via the reaction between V 2 O 5 and HF, and such species were responsible for the improved activity as they had much higher turnover frequencies (TOFs) than the MgF 2 (0.762 s −1 v.s. 0.026 s −1 at 320 °C). The kinetic results indicated that the 3.1V 2 O 5 /MgF 2 had much lower activation energy (44.6 ± 1.9 kJ mol −1 ) than the MgF 2 (69.0 ± 0.8 kJ mol −1 ). Accordingly, reaction mechanism on the V 2 O 5 /MgF 2 catalyst was proposed, which included slow dehydrofluorination on MgF 2 and fast dehydrofluorination on the VOF x species.
研究领域:
催化化学
·
材料科学
·
环境化学
✓ 已验证
产品关联
DOI
高影响因子
Catalysts
·
2020
·Vol. 10
·期 3
·355
·
IF 3.52
Wucan Liu,Yongnan Liu,Kabozya M. Mardochee,Zhikun Wang,Shucheng Wang,Wei Yu,Jianjun Zhang,Wenfeng Han
SrF2promotes the dehydrochlorination (DeHCl) of 1,1-difluoro-1-chloroethane, which is the key process for the manufacture of VDF (vinylidene fluoride), one of the most typical fluorinated monomers. However, the selectivity is low as dehydrofluorination (DeHF) to VCF (vinylidene chlorofluoride) competes with the formation of VDF. In this study, SrF2@C (SrF2embedded in carbon) and SrF2@NC (N-doped carbon) catalysts were fabricated following calcination in N2with SrC2O4, PVDF (poly vinylidene fluoride) and urea as the precursors. The catalysts were characterized by XRD, SEM, TEM, and XPS. The results show that both the calcination temperature and N-doping play an important role in the conversion of HCFC-142b and the selectivity to VDF and VCF. Calcination at elevated temperatures enhances the Sr-C interaction. For SrF2@C, improved interaction facilitates withdrawing electrons from Sr by the carbon support. By contrast, the strong interaction of Sr with N-doped carbon supply electrons from N species to Sr. The electron deficiency of Sr is favorable for the adsorption of F with higher electronegativity and consequently, DeHF reaction forming VCF. The supply of electrons to Sr by the support improves the formation of VDF (DeHCl). The present work provides a potential strategy for the improvement of selectivity to the target product.Keywords:dehydrochlorination;dehydrofluorination;metal–support interaction;strontium fluoride;vinyl difluoride
研究领域:
化学工程
·
材料科学
✓ 已验证
产品关联
DOI
高影响因子
APPLIED SURFACE SCIENCE
·
2017
·
IF 3.387
Jian-Wei Luo,Jian-Dong Song,Wen-Zhi Jia,Zhi-Ying Pu,Ji-Qing Lu,Meng-Fei Luo
Catalytic dehydrofluorination of 1,1,1,3,3-pentafluoropropane to 1,3,3,3-tetrafluoropropene was performed on a series of fluorinated NiO/Cr 2 O 3 catalysts. The NiO/Cr 2 O 3 catalysts were more active than the Cr 2 O 3 because the new acid sites provided by NiF 2 had higher turnover frequencies (9.43 × 10 −3 − 12.08 × 10 −3 s −1 ) than those on the Cr 2 O 3 (4.55 × 10 −3 s −1 ). Also, the NiO/Cr 2 O 3 was more stable than the Cr 2 O 3 due to its lower density of surface acid sites, which alleviated the coke deposition on the catalyst as evidenced by the Raman spectroscopic results. The kinetic results revealed that the15NiO/Cr 2 O 3 had much lower activation energy (63.6 ± 4.5 kJ mol −1 ) than the Cr 2 O 3 (127.6 ± 3.8 kJ mol −1 ). Accordingly, different reaction pathways on the two catalysts were proposed, which involved the cleavage of the C F and C H bonds on the surface acid and base sites, respectively.
研究领域:
化学工程
·
催化科学
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF NANOPARTICLE RESEARCH
·
2015
·Vol. 17
·期 9
·1-12
·
IF 2.184
Han Wenfeng,Li Xiaojuan,Tang Haodong,Wang Zhikun,Xi Miao,Li Ying,Liu Huazhang
Abstract A Cr 2 O 3 hexagonal prism structure synthesized via the reaction of aqueous CrCl 3 solution with NaBH 4 solution at room temperature followed by calcination of the precipitate in N 2 atmosphere at 500 °C is investigated as an efficient catalyst for dehydrofluorination of 1,1-difluoroethane producing vinyl fluoride. With the assistance of scanning electron microscopy, transmission electron microscopy, and high-resolution transmission electron microscopy, experimental results revealed that the uniform hexagonal prism has a prism length of 285 ± 43 nm and width of 233 ± 33 nm. It is in the form of loose and net-like aggregation of nano-Cr 2 O 3 with diameter less than 3–5 nm with polycrystalline structure. NH 3 temperature programmed desorption and chlorodifluoromethane dismutation experiments confirm the existence of relatively abundant and strong acidic sites. As a catalyst for dehydrofluorination of 1,1-difluoroethane, compared with commercial Cr 2 O 3 , much higher activity and stability were observed due to the evolution of CrO
x
F
y
species and much higher surface area and mesoporous structure. No significant morphology changes or sintering of the catalyst are observed after 70-h reaction. Compared with the commercial Cr 2 O 3 , we suggest that the much smaller size of Cr 2 O 3 crystalline which possesses higher surface energy, lower strength, and more abundant Lewis acidity and the formation of CrO
x
F
y
during reaction over hexagonal prism catalyst probably contributes to the activity and stability difference between these two catalysts. Graphical Abstract
研究领域:
材料科学
·
催化化学
✓ 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）