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Haodong Tang - One of the best experts on this subject based on the ideXlab platform.
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confinement of alf3 in mof derived structures for the formation of 4 fold coordinated al and significantly improved Dehydrofluorination activity
Chemical Engineering Journal, 2020Co-Authors: Aimin Chen, Lichun Li, Haodong Tang, Ying Li, Chunshan Lu, Geshan Zhang, Xiaonian LiAbstract:Abstract Dehydrofluorination is the major process for the production of fluorinated monomers and treatment of synthetic greenhouse gases. It is usually catalyzed by the Lewis acids, such as AlF3, MgF2 and fluorinated Cr2O3. The activity and stability remain the challenges of catalysts. For metal fluorides, Lewis acidic sites are derived from the unsaturated coordination of metal sites. This work reports the confinement of AlF3 into the cavity of quasi MOF structures. Due to the confinement effect and interaction of AlF3 with coordinatively unsaturated Cr-O nodes (oxygen vacancy), significant amounts of 4-fold coordinated Al in AlF3 can be achieved. Consequently, the Lewis acidity of AlF3 could be dramatically enhanced. As the catalyst of the gas-phase Dehydrofluorination of HFC-245fa (1,1,1,3,3-pentafluoropropane) to tetrafluoropropene (HFO-1234ze, a new generation of green refrigerant) at 350 °C with the GHSV of 750 h−1, it exhibited the activity of 9 times higher than that of supported AlF3. After reaction of 35 h, no noticeable deactivation was detected. The present work provides a potential strategy for the preparation of metal fluoride Lewis acid catalysts with high efficiency.
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thermally conductive sic as support of aluminum fluoride for the catalytic Dehydrofluorination reaction
Catalysis Communications, 2020Co-Authors: Jiaqin Lu, Haodong Tang, Wei Yu, Hong Yang, Ying LiAbstract:Abstract Aluminum fluoride (AlF3) 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 AlF3-based catalysts. Herein, SiC with high thermal conductivity and resistance to HF corrosion is suggested as a candidate support of AlF3 catalyst. The interaction between AlF3 and SiC leads to uniform distribution of the catalytic phase, and as a result of this, AlF3/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.
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Preparation and characterization of chromium-doped magnesium fluoride catalysts via an aqueous sol–gel method
Journal of Sol-Gel Science and Technology, 2019Co-Authors: Haodong Tang, Chaoyu Zou, Wenfeng Han, Lichun Li, Yuzhen Li, Nan Zhou, Tao Hu, Ying LiAbstract:High surface area Cr3+-doped MgF2 catalysts were synthesized from an aqueous sol–gel method under mild conditions. The amount of Cr3+ doped in the investigated CrF3/MgF2 catalysts covered a wide range of mole concentration ranging from 0 to 25 mol% to reveal its effect on the properties of the catalysts. The physio-chemical properties of the CrF3/MgF2 catalyst were examined by means of N2 gas sorption, X-ray powder diffraction (XRD), energy dispersive spectrometer (EDS), and temperature-programmed desorption (TPD) of NH3. XRD analysis indicates that the doping of Cr3+ resulted in reduced crystallinity but did not change the original crystalline structure of MgF2. Doping of Cr3+ (8–25 mol%), on the other hand, can increase the surface area of CrF3/MgF2 significantly to ~300 m2/g from ~50 m2/g of the nondoped MgF2. There is also significant amount of Lewis acid sites formed upon incorporation of Cr3+ into MgF2 lattice, which was evidenced from the NH3-TPD results. The catalytic activity of the 25 mol% Cr3+-doped MgF2 catalyst on the Dehydrofluorination reaction of 1,1-difluoroethane (HFC-152a, CH3CHF2) has reached a conversion rate of ~57%, which is over two times higher than the undoped MgF2 catalyst. Furthermore, the 25 mol% Cr3+-doped MgF2 catalyst has been successfully tested over 210 h upon the Dehydrofluorination of CH3CHF2 at 300 °C with the conversion rate remain greater than ~45%. HighlightsA novel aqueous sol–gel method was evaluated for the preparation of HS-CrF3/MgF2 catalysts.The effects of Cr3+ dopant concentration on physio-chemical properties of HS-CrF3/MgF2 have been investigated.With dopant concentration below 25%, dopant (Cr3+) has incorporate into the lattice of the host (MgF2).25 mol% Cr3+-doped MgF2 catalyst has been used for the Dehydrofluorination of CH3CHF2 for 210 h at 300 °C with the conversion rate still being greater than ~45%.
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rational design of mgf2 catalysts with long term stability for the Dehydrofluorination of 1 1 difluoroethane hfc 152a
RSC Advances, 2019Co-Authors: Haodong Tang, Lichun Li, Yuzhen Li, Ying Li, Mingming Dang, Xiaonian LiAbstract:In this study, three different approaches, i.e. the sol–gel method, precipitation method and hard-template method, were applied to synthesize MgF2 catalysts with improved stability towards the Dehydrofluorination of hydrofluorocarbons (HFCs); the in situ XRD technique was employed to investigate the relationship between the calcination temperature and the crystallite size of precursors to determine optimal calcination temperature for the preparation of the MgF2 catalysts. Moreover, the physicochemical properties of MgF2 catalysts were examined via BET, XRD, EDS and TPD of NH3 and compared. Undoubtedly, the application of different methods had a significant influence on the surface properties and catalytic performances of MgF2 catalysts. The surface areas of the catalysts prepared by the precipitation method, sol–gel method and template method were 120, 215 and 304 m2 g−1, respectively, upon calcination at 200 °C. However, the surface area of the MgF2 catalysts decreased significantly when the calcination temperatures of 300 and 350 °C were applied. The catalytic performance of these catalysts was evaluated via the Dehydrofluorination of 1,1-difluoroethane (HFC-152a). The MgF2 catalyst prepared by the precipitation method showed the lowest catalytic activity among all the MgF2 catalysts. When the calcination temperature was above 300 °C, the MgF2 catalysts prepared via the template method demonstrated the highest catalytic conversion rate with catalytic activity following the order: MgF2-T (template method) > MgF2-S (sol–gel method) > MgF2-P (precipitation method). The conversion rate generally agreed with the total amount of acid on the surface of the catalysts, which was measured by the NH3-TPD technique. The MgF2-T catalysts were further examined for the Dehydrofluorination of HFC-152a for 600 hours, and a conversion rate greater than 45% was maintained, demonstrating superior long-term stability of these catalysts.
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quasi metal organic framework with highly concentrated cr2o3 molecular clusters as the efficient catalyst for Dehydrofluorination of 1 1 1 3 3 pentafluoropropane
Applied Catalysis B-environmental, 2019Co-Authors: Xiliang Li, Lichun Li, Haodong Tang, Ying Li, Chunshan Lu, Xiaonian LiAbstract:Abstract Metal-organic frameworks (MOFs) are promising platforms for the application of catalysis with hierarchical porous structures and high surface areas. However, the stability is one of the key challenges for the reactions at elevated temperatures. In the present work, we demonstrate the preparation of Quasi MIL-101 structures with high concentration of Cr 2 O 3 molecular clusters (21.7 wt%˜54.2 wt%) via calcination in N 2 atmosphere at temperatures between 350 °C and 500 °C. Cr 2 O 3 clusters show high activity and stability for the Dehydrofluorination of 1,1,1,3,3-pentafluoropropane (HFC-245fa) to 1,3,3,3-tetrafluoropropene (HFO-1234ze). Dehydrofluorination of HFC-245fa is an efficient route for the synthesis of HFO-1234ze. With calcination temperature of 450 °C, the reaction rate of Cr 2 O 3 molecular clusters is almost 4 times higher than that of commercial Cr 2 O 3 and no significant deactivation was observed. Therefore, this study provides a competitive strategy for the preparation of molecular clusters catalysts with high thermal stability.
Ying Li - One of the best experts on this subject based on the ideXlab platform.
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confinement of alf3 in mof derived structures for the formation of 4 fold coordinated al and significantly improved Dehydrofluorination activity
Chemical Engineering Journal, 2020Co-Authors: Aimin Chen, Lichun Li, Haodong Tang, Ying Li, Chunshan Lu, Geshan Zhang, Xiaonian LiAbstract:Abstract Dehydrofluorination is the major process for the production of fluorinated monomers and treatment of synthetic greenhouse gases. It is usually catalyzed by the Lewis acids, such as AlF3, MgF2 and fluorinated Cr2O3. The activity and stability remain the challenges of catalysts. For metal fluorides, Lewis acidic sites are derived from the unsaturated coordination of metal sites. This work reports the confinement of AlF3 into the cavity of quasi MOF structures. Due to the confinement effect and interaction of AlF3 with coordinatively unsaturated Cr-O nodes (oxygen vacancy), significant amounts of 4-fold coordinated Al in AlF3 can be achieved. Consequently, the Lewis acidity of AlF3 could be dramatically enhanced. As the catalyst of the gas-phase Dehydrofluorination of HFC-245fa (1,1,1,3,3-pentafluoropropane) to tetrafluoropropene (HFO-1234ze, a new generation of green refrigerant) at 350 °C with the GHSV of 750 h−1, it exhibited the activity of 9 times higher than that of supported AlF3. After reaction of 35 h, no noticeable deactivation was detected. The present work provides a potential strategy for the preparation of metal fluoride Lewis acid catalysts with high efficiency.
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thermally conductive sic as support of aluminum fluoride for the catalytic Dehydrofluorination reaction
Catalysis Communications, 2020Co-Authors: Jiaqin Lu, Haodong Tang, Wei Yu, Hong Yang, Ying LiAbstract:Abstract Aluminum fluoride (AlF3) 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 AlF3-based catalysts. Herein, SiC with high thermal conductivity and resistance to HF corrosion is suggested as a candidate support of AlF3 catalyst. The interaction between AlF3 and SiC leads to uniform distribution of the catalytic phase, and as a result of this, AlF3/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.
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Preparation and characterization of chromium-doped magnesium fluoride catalysts via an aqueous sol–gel method
Journal of Sol-Gel Science and Technology, 2019Co-Authors: Haodong Tang, Chaoyu Zou, Wenfeng Han, Lichun Li, Yuzhen Li, Nan Zhou, Tao Hu, Ying LiAbstract:High surface area Cr3+-doped MgF2 catalysts were synthesized from an aqueous sol–gel method under mild conditions. The amount of Cr3+ doped in the investigated CrF3/MgF2 catalysts covered a wide range of mole concentration ranging from 0 to 25 mol% to reveal its effect on the properties of the catalysts. The physio-chemical properties of the CrF3/MgF2 catalyst were examined by means of N2 gas sorption, X-ray powder diffraction (XRD), energy dispersive spectrometer (EDS), and temperature-programmed desorption (TPD) of NH3. XRD analysis indicates that the doping of Cr3+ resulted in reduced crystallinity but did not change the original crystalline structure of MgF2. Doping of Cr3+ (8–25 mol%), on the other hand, can increase the surface area of CrF3/MgF2 significantly to ~300 m2/g from ~50 m2/g of the nondoped MgF2. There is also significant amount of Lewis acid sites formed upon incorporation of Cr3+ into MgF2 lattice, which was evidenced from the NH3-TPD results. The catalytic activity of the 25 mol% Cr3+-doped MgF2 catalyst on the Dehydrofluorination reaction of 1,1-difluoroethane (HFC-152a, CH3CHF2) has reached a conversion rate of ~57%, which is over two times higher than the undoped MgF2 catalyst. Furthermore, the 25 mol% Cr3+-doped MgF2 catalyst has been successfully tested over 210 h upon the Dehydrofluorination of CH3CHF2 at 300 °C with the conversion rate remain greater than ~45%. HighlightsA novel aqueous sol–gel method was evaluated for the preparation of HS-CrF3/MgF2 catalysts.The effects of Cr3+ dopant concentration on physio-chemical properties of HS-CrF3/MgF2 have been investigated.With dopant concentration below 25%, dopant (Cr3+) has incorporate into the lattice of the host (MgF2).25 mol% Cr3+-doped MgF2 catalyst has been used for the Dehydrofluorination of CH3CHF2 for 210 h at 300 °C with the conversion rate still being greater than ~45%.
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rational design of mgf2 catalysts with long term stability for the Dehydrofluorination of 1 1 difluoroethane hfc 152a
RSC Advances, 2019Co-Authors: Haodong Tang, Lichun Li, Yuzhen Li, Ying Li, Mingming Dang, Xiaonian LiAbstract:In this study, three different approaches, i.e. the sol–gel method, precipitation method and hard-template method, were applied to synthesize MgF2 catalysts with improved stability towards the Dehydrofluorination of hydrofluorocarbons (HFCs); the in situ XRD technique was employed to investigate the relationship between the calcination temperature and the crystallite size of precursors to determine optimal calcination temperature for the preparation of the MgF2 catalysts. Moreover, the physicochemical properties of MgF2 catalysts were examined via BET, XRD, EDS and TPD of NH3 and compared. Undoubtedly, the application of different methods had a significant influence on the surface properties and catalytic performances of MgF2 catalysts. The surface areas of the catalysts prepared by the precipitation method, sol–gel method and template method were 120, 215 and 304 m2 g−1, respectively, upon calcination at 200 °C. However, the surface area of the MgF2 catalysts decreased significantly when the calcination temperatures of 300 and 350 °C were applied. The catalytic performance of these catalysts was evaluated via the Dehydrofluorination of 1,1-difluoroethane (HFC-152a). The MgF2 catalyst prepared by the precipitation method showed the lowest catalytic activity among all the MgF2 catalysts. When the calcination temperature was above 300 °C, the MgF2 catalysts prepared via the template method demonstrated the highest catalytic conversion rate with catalytic activity following the order: MgF2-T (template method) > MgF2-S (sol–gel method) > MgF2-P (precipitation method). The conversion rate generally agreed with the total amount of acid on the surface of the catalysts, which was measured by the NH3-TPD technique. The MgF2-T catalysts were further examined for the Dehydrofluorination of HFC-152a for 600 hours, and a conversion rate greater than 45% was maintained, demonstrating superior long-term stability of these catalysts.
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quasi metal organic framework with highly concentrated cr2o3 molecular clusters as the efficient catalyst for Dehydrofluorination of 1 1 1 3 3 pentafluoropropane
Applied Catalysis B-environmental, 2019Co-Authors: Xiliang Li, Lichun Li, Haodong Tang, Ying Li, Chunshan Lu, Xiaonian LiAbstract:Abstract Metal-organic frameworks (MOFs) are promising platforms for the application of catalysis with hierarchical porous structures and high surface areas. However, the stability is one of the key challenges for the reactions at elevated temperatures. In the present work, we demonstrate the preparation of Quasi MIL-101 structures with high concentration of Cr 2 O 3 molecular clusters (21.7 wt%˜54.2 wt%) via calcination in N 2 atmosphere at temperatures between 350 °C and 500 °C. Cr 2 O 3 clusters show high activity and stability for the Dehydrofluorination of 1,1,1,3,3-pentafluoropropane (HFC-245fa) to 1,3,3,3-tetrafluoropropene (HFO-1234ze). Dehydrofluorination of HFC-245fa is an efficient route for the synthesis of HFO-1234ze. With calcination temperature of 450 °C, the reaction rate of Cr 2 O 3 molecular clusters is almost 4 times higher than that of commercial Cr 2 O 3 and no significant deactivation was observed. Therefore, this study provides a competitive strategy for the preparation of molecular clusters catalysts with high thermal stability.
Xiaonian Li - One of the best experts on this subject based on the ideXlab platform.
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confinement of alf3 in mof derived structures for the formation of 4 fold coordinated al and significantly improved Dehydrofluorination activity
Chemical Engineering Journal, 2020Co-Authors: Aimin Chen, Lichun Li, Haodong Tang, Ying Li, Chunshan Lu, Geshan Zhang, Xiaonian LiAbstract:Abstract Dehydrofluorination is the major process for the production of fluorinated monomers and treatment of synthetic greenhouse gases. It is usually catalyzed by the Lewis acids, such as AlF3, MgF2 and fluorinated Cr2O3. The activity and stability remain the challenges of catalysts. For metal fluorides, Lewis acidic sites are derived from the unsaturated coordination of metal sites. This work reports the confinement of AlF3 into the cavity of quasi MOF structures. Due to the confinement effect and interaction of AlF3 with coordinatively unsaturated Cr-O nodes (oxygen vacancy), significant amounts of 4-fold coordinated Al in AlF3 can be achieved. Consequently, the Lewis acidity of AlF3 could be dramatically enhanced. As the catalyst of the gas-phase Dehydrofluorination of HFC-245fa (1,1,1,3,3-pentafluoropropane) to tetrafluoropropene (HFO-1234ze, a new generation of green refrigerant) at 350 °C with the GHSV of 750 h−1, it exhibited the activity of 9 times higher than that of supported AlF3. After reaction of 35 h, no noticeable deactivation was detected. The present work provides a potential strategy for the preparation of metal fluoride Lewis acid catalysts with high efficiency.
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rational design of mgf2 catalysts with long term stability for the Dehydrofluorination of 1 1 difluoroethane hfc 152a
RSC Advances, 2019Co-Authors: Haodong Tang, Lichun Li, Yuzhen Li, Ying Li, Mingming Dang, Xiaonian LiAbstract:In this study, three different approaches, i.e. the sol–gel method, precipitation method and hard-template method, were applied to synthesize MgF2 catalysts with improved stability towards the Dehydrofluorination of hydrofluorocarbons (HFCs); the in situ XRD technique was employed to investigate the relationship between the calcination temperature and the crystallite size of precursors to determine optimal calcination temperature for the preparation of the MgF2 catalysts. Moreover, the physicochemical properties of MgF2 catalysts were examined via BET, XRD, EDS and TPD of NH3 and compared. Undoubtedly, the application of different methods had a significant influence on the surface properties and catalytic performances of MgF2 catalysts. The surface areas of the catalysts prepared by the precipitation method, sol–gel method and template method were 120, 215 and 304 m2 g−1, respectively, upon calcination at 200 °C. However, the surface area of the MgF2 catalysts decreased significantly when the calcination temperatures of 300 and 350 °C were applied. The catalytic performance of these catalysts was evaluated via the Dehydrofluorination of 1,1-difluoroethane (HFC-152a). The MgF2 catalyst prepared by the precipitation method showed the lowest catalytic activity among all the MgF2 catalysts. When the calcination temperature was above 300 °C, the MgF2 catalysts prepared via the template method demonstrated the highest catalytic conversion rate with catalytic activity following the order: MgF2-T (template method) > MgF2-S (sol–gel method) > MgF2-P (precipitation method). The conversion rate generally agreed with the total amount of acid on the surface of the catalysts, which was measured by the NH3-TPD technique. The MgF2-T catalysts were further examined for the Dehydrofluorination of HFC-152a for 600 hours, and a conversion rate greater than 45% was maintained, demonstrating superior long-term stability of these catalysts.
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quasi metal organic framework with highly concentrated cr2o3 molecular clusters as the efficient catalyst for Dehydrofluorination of 1 1 1 3 3 pentafluoropropane
Applied Catalysis B-environmental, 2019Co-Authors: Xiliang Li, Lichun Li, Haodong Tang, Ying Li, Chunshan Lu, Xiaonian LiAbstract:Abstract Metal-organic frameworks (MOFs) are promising platforms for the application of catalysis with hierarchical porous structures and high surface areas. However, the stability is one of the key challenges for the reactions at elevated temperatures. In the present work, we demonstrate the preparation of Quasi MIL-101 structures with high concentration of Cr 2 O 3 molecular clusters (21.7 wt%˜54.2 wt%) via calcination in N 2 atmosphere at temperatures between 350 °C and 500 °C. Cr 2 O 3 clusters show high activity and stability for the Dehydrofluorination of 1,1,1,3,3-pentafluoropropane (HFC-245fa) to 1,3,3,3-tetrafluoropropene (HFO-1234ze). Dehydrofluorination of HFC-245fa is an efficient route for the synthesis of HFO-1234ze. With calcination temperature of 450 °C, the reaction rate of Cr 2 O 3 molecular clusters is almost 4 times higher than that of commercial Cr 2 O 3 and no significant deactivation was observed. Therefore, this study provides a competitive strategy for the preparation of molecular clusters catalysts with high thermal stability.
Jiqing Lu - One of the best experts on this subject based on the ideXlab platform.
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high performance v2o5 mgf2 catalysts for gas phase Dehydrofluorination of 1 1 1 3 3 pentafluoropropane support induced evolution of new active sites
Journal of Catalysis, 2018Co-Authors: Jiandong Song, Tongyang Song, Tingting Zhang, Yun Wang, Jiqing LuAbstract:Abstract A series of supported V2O5/MgF2 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 V2O5 in MgF2 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 MgF2 support triggered the transformation of V2O5 to vanadium oxyfluoride (VOFx) species via the reaction between V2O5 and HF, and such species were responsible for the improved activity as they had much higher turnover frequencies (TOFs) than the MgF2 (0.762 s−1 v.s. 0.026 s−1 at 320 °C). The kinetic results indicated that the 3.1V2O5/MgF2 had much lower activation energy (44.6 ± 1.9 kJ mol−1) than the MgF2 (69.0 ± 0.8 kJ mol−1). Accordingly, reaction mechanism on the V2O5/MgF2 catalyst was proposed, which included slow Dehydrofluorination on MgF2 and fast Dehydrofluorination on the VOFx species.
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High performance V2O5/MgF2 catalysts for gas-phase Dehydrofluorination of 1,1,1,3,3-pentafluoropropane: Support-induced evolution of new active sites
Journal of Catalysis, 2018Co-Authors: Jiandong Song, Tongyang Song, Tingting Zhang, Yun Wang, Jiqing LuAbstract:Abstract A series of supported V2O5/MgF2 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 V2O5 in MgF2 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 MgF2 support triggered the transformation of V2O5 to vanadium oxyfluoride (VOFx) species via the reaction between V2O5 and HF, and such species were responsible for the improved activity as they had much higher turnover frequencies (TOFs) than the MgF2 (0.762 s−1 v.s. 0.026 s−1 at 320 °C). The kinetic results indicated that the 3.1V2O5/MgF2 had much lower activation energy (44.6 ± 1.9 kJ mol−1) than the MgF2 (69.0 ± 0.8 kJ mol−1). Accordingly, reaction mechanism on the V2O5/MgF2 catalyst was proposed, which included slow Dehydrofluorination on MgF2 and fast Dehydrofluorination on the VOFx species.
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pd alf3 catalysts for catalytic Dehydrofluorination of 1 1 1 3 3 pentafluoropropane
Chemical Research in Chinese Universities, 2015Co-Authors: Fang Wang, Wenxia Zhang, Yan Liang, Yuejuan Wang, Jiqing LuAbstract:A series of Pd/AlF3 catalysts was prepared by an impregnation method and tested for vapor-phase Dehydrofluorination of 1,1,1,3,3-pentafluoropropane(HFC-245fa) to synthesize 1,3,3,3-tetrafluoropropene(HFO-1234ze). The highest activity was obtained over Pd/AlF3 catalyst containing 1.0%(mass fraction) of Pd, with an HFC-245fa conversion of 79.5% and an HFO-1234ze selectivity of 99.4% after the reaction at 300 °C for 100 h. The reactivity was related to the surface acidity, as AlF3 provided active sites for the reaction. With the addition of Pd, the catalyst stability could be significantly improved. Raman spectroscopic and thermal-gravimetric analysis results reveal that there was less carbon deposit on spent Pd/AlF3 catalyst surface because Pd could effectively pyrolyse it. Thus, Pd/AlF3 catalysts were bi-functional for Dehydrofluorination of HFC-245fa.
Mingyi Liao - One of the best experts on this subject based on the ideXlab platform.
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study on the Dehydrofluorination of vinylidene fluoride vdf and hexafluoropropylene hfp copolymer
Polymer Degradation and Stability, 2018Co-Authors: Donghan Li, Mingyi LiaoAbstract:Abstract 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), 1H nuclear magnetic resonance (NMR), 19F 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.
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Dehydrofluorination mechanism structure and thermal stability of pure fluoroelastomer poly vdf ter hfp ter tfe terpolymer in alkaline environment
Journal of Fluorine Chemistry, 2017Co-Authors: Donghan Li, Mingyi LiaoAbstract:Abstract This study evaluates the Dehydrofluorination mechanism, structure and thermal stability of pure fluoroelastomer which was dissolved by organic solvent and reacted with different concentrations of KOH at 20 ∼ 60 °C. The sequence types and contents of double bonds and other oxygen-containing groups of samples were analyzed and investigated by Attenuated total reflectance/Fourier transform infrared (ATR-FTIR), 1H nuclear magnetic resonance (NMR), 19F-NMR spectroscopy and chemical titration method; thermal decomposition temperatures of samples were analyzed by thermogravimetric analysis (TGA). The results revealed that Dehydrofluorination of fluoroelastomer would accompain with oxidation reaction whereby some double bonds conforming to Hofmann’s rule had been converted to hydroxyl groups, wherein the temperature and alkali concentration were the important factors. The double bonds generated in seven positions of molecular chains, sequence types were mainly conformed to Hofmann’s rule and Zaitsev’s rule supplemented. With the increase of reaction temperature and concentration of KOH, the thermal stability of fluoroelastomer decreased obviously since hydroxyl groups had a greater effect on it. Finally, the mechanism of reaction was also deduced.