The selective oxidation of n-butane to maleic anhydride (MA) on a vanadium-phosphorus oxide (VPO) catalyst was studied using on-line gas-chromatography combined with mass spectrometry(GC-MS) and transient response tec...The selective oxidation of n-butane to maleic anhydride (MA) on a vanadium-phosphorus oxide (VPO) catalyst was studied using on-line gas-chromatography combined with mass spectrometry(GC-MS) and transient response technique. The reaction intermediates, buterie and furan, were found in the reaction effluent under near industrial feed condition (3% butane+15%O2), while dihydrofuran was detected at high butane concentration (12% butane, 5%O2). Some intermediates of MA decomposition were also identified. Detection of these intermediates shows that the vanadium phosphorus oxides are able to dehydrogenate butane to butene, and butene further to form MA. Based on these observations, a modified scheme of reaction network is proposed. The transient experiments show that butane in the gas phase may directly react with oxygen both on the surface and from the metal oxide lattice, without a proceeding adsorption step. Gas phase oxygen can be adsorbed and transformed to surface lattice oxygen but it can not participate in selective oxidation. Adsorbed oxygen leads to deep oxidation, while lattice oxygen leads to selective oxidation.展开更多
Selective oxidation of n-butane to maleic anhydride(MA)is considered an effective approach to realize the utilization of lighter alkanes into useful chemical products.Currently,vanadium phosphorus oxide(VPO)is the mos...Selective oxidation of n-butane to maleic anhydride(MA)is considered an effective approach to realize the utilization of lighter alkanes into useful chemical products.Currently,vanadium phosphorus oxide(VPO)is the most widely used catalyst for the selective oxidation of n-butane to MA owing to its abundant active sites and oxygen species.However,the development of efficient VPO catalysts remains urgent,as the MA yield is limited by the inherent“trade-off”effect between n-butane conversion and MA selectivity.This review systematically summarizes the progress in the rational design and precise regulation of VPO catalysts,with a particular focus on the influence of physicochemical properties on catalytic performance.More importantly,advanced synthesis routes and modification strategies are discussed in detail.These strategies for modulating the geometric and electronic structures of VPO catalysts are highlighted,accompanied by a discussion of the structure-activity relationship.Finally,the challenges of VPO catalysts are discussed,and future research directions are proposed.展开更多
The utilization of lighter alkanes into useful chemical products is essential for modern chemistry and reducing the CO_(2)emission.Particularly,n-butane has gained special attention across the globe due to the abundan...The utilization of lighter alkanes into useful chemical products is essential for modern chemistry and reducing the CO_(2)emission.Particularly,n-butane has gained special attention across the globe due to the abundant production of maleic anhydride(MA).Vanadium phosphorous oxide(VPO)is the most effective catalyst for selective oxidation of n-butane to MA so far.Interestingly,the VPO complex exists in more or less fifteen different structures,each one having distinct phase composition and exclusive surface morphology and physiochemical properties such as valence state,lattice oxygen,acidity etc.,which relies on precursor preparation method and the activation conditions of catalysts.The catalytic performance of VPO catalyst is improved by adding different promoters or co-catalyst such as various metals dopants,or either introducing template or structural-directing agents.Meanwhile,new preparation strategies such as electrospinning,ball milling,hydrothermal,barothermal,ultrasound,microwave irradiation,calcination,sol-gel method and solvothermal synthesis are also employed for introducing improvement in catalytic performance.Research in above-mentioned different aspects will be ascribed in current review in addition to summarizing overall catalysis activity and final yield.To analyze the performance of the catalytic precursor,the reaction mechanism and reaction kinetics both are discussed in this review to help clarify the key issues such as strong exothermic reaction,phosphorus supplement,water supplement,deactivation,and air/n-butane pretreatment etc.related to the various industrial applications of VPO.展开更多
Vanadium phosphorus oxide(VPO)catalyst is a promising candidate for the condensation reaction of formaldehyde(FA)and acetic acid(HAc)to produce acrylic acid(AA).However,the complexity of the active phases and their dy...Vanadium phosphorus oxide(VPO)catalyst is a promising candidate for the condensation reaction of formaldehyde(FA)and acetic acid(HAc)to produce acrylic acid(AA).However,the complexity of the active phases and their dynamic interconversion under redox conditions has led to controversies regarding the actual active phase in this reaction.To address this,this study systematically investigates the phase transition and underlying mechanism of VPO catalysts under reaction conditions.X-ray diffraction(XRD)patterns,Raman spectra,transmission electron microscopy images and X-ray photoelectron spectroscopy collectively demonstrated that the V^(4+)phase(VO)_(2)P_(2)O_(7)retained the bulk phase structure throughout the reaction,with only minor surface phase transition observed.In contrast,the V^(5+)phase underwent reduction to other phases in both bulk and surface regions.Specifically,theδ-VOPO_(4)phase rapidly transformed into theαII-VOPO_(4)phase,which could reversibly convert into the R1-VOHPO_(4)phase(V^(4+)).Controlled variable experiments,H_(2)-temperature programmed reduction and in-situ XRD experiments in a hydrogen atmosphere further demonstrated that these phase transitions were primarily attributed to the loss of lattice oxygen.The presence of V^(4+)phase in VPO catalysts enhanced the selectivity of acrylic acid,while the existence of V^(5+)phase promoted the activation of acetic acid.This work elucidates the redox-driven phase evolution of VPO catalysts and offers valuable insights for designing efficient catalysts for FA-HAc cross-condensation by balancing phase stability and activity.展开更多
基金Supported by the National Natural Science Foundation of China (No. 29792073-3).
文摘The selective oxidation of n-butane to maleic anhydride (MA) on a vanadium-phosphorus oxide (VPO) catalyst was studied using on-line gas-chromatography combined with mass spectrometry(GC-MS) and transient response technique. The reaction intermediates, buterie and furan, were found in the reaction effluent under near industrial feed condition (3% butane+15%O2), while dihydrofuran was detected at high butane concentration (12% butane, 5%O2). Some intermediates of MA decomposition were also identified. Detection of these intermediates shows that the vanadium phosphorus oxides are able to dehydrogenate butane to butene, and butene further to form MA. Based on these observations, a modified scheme of reaction network is proposed. The transient experiments show that butane in the gas phase may directly react with oxygen both on the surface and from the metal oxide lattice, without a proceeding adsorption step. Gas phase oxygen can be adsorbed and transformed to surface lattice oxygen but it can not participate in selective oxidation. Adsorbed oxygen leads to deep oxidation, while lattice oxygen leads to selective oxidation.
基金supported by the Sichuan Science and Technology Program,the Fundamental Research Funds for Central Universities(Grant No.20826041H4212)the Sichuan Scientific and Technological Achievements Transfer and Transformation Demonstration Project(Grant No.24ZHSF0549).
文摘Selective oxidation of n-butane to maleic anhydride(MA)is considered an effective approach to realize the utilization of lighter alkanes into useful chemical products.Currently,vanadium phosphorus oxide(VPO)is the most widely used catalyst for the selective oxidation of n-butane to MA owing to its abundant active sites and oxygen species.However,the development of efficient VPO catalysts remains urgent,as the MA yield is limited by the inherent“trade-off”effect between n-butane conversion and MA selectivity.This review systematically summarizes the progress in the rational design and precise regulation of VPO catalysts,with a particular focus on the influence of physicochemical properties on catalytic performance.More importantly,advanced synthesis routes and modification strategies are discussed in detail.These strategies for modulating the geometric and electronic structures of VPO catalysts are highlighted,accompanied by a discussion of the structure-activity relationship.Finally,the challenges of VPO catalysts are discussed,and future research directions are proposed.
基金supported by the National Key Research and Development Program of China(2017YFA0206803)the innovation Academy for Green Manufacture of Chinese Academy of Science(IAGM2020C17)+3 种基金the Key Programs of the Chinese Academy of Sciences(KFZD-SW-413)the National Nature Science Foundation of China(21808223)the Key Programs of Fujian Institute of Innovation,CAS(FJCXY18020203)Chinese Academy of Sciences,the One Hundred Talent Program of CAS。
文摘The utilization of lighter alkanes into useful chemical products is essential for modern chemistry and reducing the CO_(2)emission.Particularly,n-butane has gained special attention across the globe due to the abundant production of maleic anhydride(MA).Vanadium phosphorous oxide(VPO)is the most effective catalyst for selective oxidation of n-butane to MA so far.Interestingly,the VPO complex exists in more or less fifteen different structures,each one having distinct phase composition and exclusive surface morphology and physiochemical properties such as valence state,lattice oxygen,acidity etc.,which relies on precursor preparation method and the activation conditions of catalysts.The catalytic performance of VPO catalyst is improved by adding different promoters or co-catalyst such as various metals dopants,or either introducing template or structural-directing agents.Meanwhile,new preparation strategies such as electrospinning,ball milling,hydrothermal,barothermal,ultrasound,microwave irradiation,calcination,sol-gel method and solvothermal synthesis are also employed for introducing improvement in catalytic performance.Research in above-mentioned different aspects will be ascribed in current review in addition to summarizing overall catalysis activity and final yield.To analyze the performance of the catalytic precursor,the reaction mechanism and reaction kinetics both are discussed in this review to help clarify the key issues such as strong exothermic reaction,phosphorus supplement,water supplement,deactivation,and air/n-butane pretreatment etc.related to the various industrial applications of VPO.
文摘Vanadium phosphorus oxide(VPO)catalyst is a promising candidate for the condensation reaction of formaldehyde(FA)and acetic acid(HAc)to produce acrylic acid(AA).However,the complexity of the active phases and their dynamic interconversion under redox conditions has led to controversies regarding the actual active phase in this reaction.To address this,this study systematically investigates the phase transition and underlying mechanism of VPO catalysts under reaction conditions.X-ray diffraction(XRD)patterns,Raman spectra,transmission electron microscopy images and X-ray photoelectron spectroscopy collectively demonstrated that the V^(4+)phase(VO)_(2)P_(2)O_(7)retained the bulk phase structure throughout the reaction,with only minor surface phase transition observed.In contrast,the V^(5+)phase underwent reduction to other phases in both bulk and surface regions.Specifically,theδ-VOPO_(4)phase rapidly transformed into theαII-VOPO_(4)phase,which could reversibly convert into the R1-VOHPO_(4)phase(V^(4+)).Controlled variable experiments,H_(2)-temperature programmed reduction and in-situ XRD experiments in a hydrogen atmosphere further demonstrated that these phase transitions were primarily attributed to the loss of lattice oxygen.The presence of V^(4+)phase in VPO catalysts enhanced the selectivity of acrylic acid,while the existence of V^(5+)phase promoted the activation of acetic acid.This work elucidates the redox-driven phase evolution of VPO catalysts and offers valuable insights for designing efficient catalysts for FA-HAc cross-condensation by balancing phase stability and activity.
