Vanadium Oxide Based Nanostructured Materials: Novel Oxidative Dehydrogenation Catalysts

Novel vanadium oxide based catalyst derived from the open-framework solid, [Co₃V₁₈O₄₂(H₂O)₁₂(XO₄)]·24 H₂O (X = V, S) (1) catalyses oxidative dehydrogenation of propane to propylene. Catalyst activity was evaluated in the temperature range 250–400 °C with varying gas hourly space velocity (GHSV). At 350 °C and GHSV of 9786 h^?1 and at 1.3% propane conversion the selectivity to propylene was 36.8%. The major products obtained were propylene and CO _x (CO₂ and CO). The ratio of the propylene to CO _x depended directly on the catalytic sites present. Thus, as the amount of the catalyst was decreased, the conversion decreased with an increase in the propylene selectivity and a decrease in the selectivity to carbon oxides—CO _x . The catalyst has been characterized by temperature programmed reduction and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS).     

掺杂碳材料用于氧还原反应中的研究进展

燃料电池具有高效和洁净等突出优点,是最有发展前途的一种动力电池,可广泛用于移动电源和便携式电源。近年来,非铂催化剂成为燃料电池领域研究的热点,掺杂碳材料因其价格低廉,环境友好,具有良好的耐腐蚀性,高电导性以及在氧还原反应过程表现出良好的催化活性,被认为是燃料电池阴极氧还原反应的理想催化剂。本文主要介绍了氮,硫,硼,磷掺杂碳材料以及用于燃料电池氧还原反应催化剂的研究进展。     

Oxidative Dehydrogenation of Ethane Over Zirconia‐Supported Lithium Chloride Catalysts

A series of Li‐doped catalysts on zirconia or sulfated zirconia were prepared and investigated in the catalytic reaction of ethane oxidative dehydrogenation into ethylene. It is found that zirconia and sulfated zirconia supports prepared by different methods show varying nature and thus influence the catalytic performance of their supported Li catalysts in this reaction. Li catalysts doped on the sulfated zirconia prepared by a two‐step method can exhibit high ethane conversion, selectivity towards ethylene and ethylene yield as well as a stable catalytic performance. The Li precursors also affect the catalytic behavior. LiCl doped on sulfated zirconia can give high ethane conversion and ethylene selectivity. Addition of transitional and lanthanide metal oxides to the LiCl/SZ system significantly improves the activity and yield of ethylene in the oxidative dehydrogenation of ethane. Among the oxides studied, NiO and Nd₂O₃ demonstrate the best promoting effect in terms of catalytic conversion and ethylene yield.     

Factors Affect on the Reaction Performance of the Oxidative Dehydrogenation of n-Butene to 1,3-Butadiene Over Zn-Ferrite Catalysts

Two types of zinc ferrite catalysts have been prepared by physical mixing or coprecipitation and applied to the oxidative dehydrogenation of n-butene to 1,3-butadiene. It is observed that the catalytic activity is significantly dependent upon not only the crystallinity but also the composition of a ferrite catalyst. If crystallinity of a catalyst is too high, the oxygen spillover through the lattice is severely suppressed and results in low catalytic activity. On the other hand, the presence of α-Fe₂O₃ in ferrite structure may lead to decrease of the reaction performance. Coprecipitation with strong base such as NaOH is found to be one of the efficient methods to form a catalytically active ferrite structure in that it is advantageous to obtain pure ferrite composition with appropriate crystallinity. During catalyst preparation, complete removal of sodium is essential because the residual sodium in catalyst considerably reduces the reaction performance. Although the use of mild base such as NH₄OH is advantageous to prevent the exhaustive washing, the formation of mixed phase both α-Fe₂O₃ and ZnFe₂O₄ may reduce n-butene conversion as well as 1,3-butadiene selectivity.     

Correlation Between the Characteristics and Catalytic Performance of Ni–V–O Catalysts in Oxidative Dehydrogenation of Propane

Ni–V–O series catalysts for the oxidative dehydrogenation (ODH) of propane were prepared and characterized by BET, XRD, H₂-TPR, O₂-TPD-MS and electrical conductivity. At 425°C a C₃H₆ selectivity of 49.9% was observed on Ni_0.9V_0.1O _Y at a C₃H₈ conversion of 19.4%, and the obtained selectivity is almost two times higher than that over NiO at the roughly same conversion of C₃H₈. The mobile oxygen species created by the interaction of NiO and V₂O₅ has been found in the composite catalysts by O₂-TPD-MS and electrical conductivity studies, which seems to be responsible for the enhanced selectivity of the propane oxidative dehydrogenation.     

Propane Oxidative Dehydrogenation over Metal Pyrophosphates Catalysts

Metal pyrophosphates (M–P₂O₇, where M is V, Zr, Cr, Mg, Mn, Ni or Ce) have been found to catalyze the oxidative dehydrogenation of propane to propene. The reaction was conducted at 1 atm, 450–550°C and feed flowrate of 75 cm³/min (20 cm³/min propane, 5 cm³/min oxygen and the balance is helium). All catalysts showed increase in degrees of conversion and decrease in olefins selectivity with increase in reaction temperature. At 550°C, MnP₂O₇ exhibited the highest activity (40.7% conversion) and total olefins (C₃H₆ and C₂H₄) yield (29.3%). The other catalysts, indicated by their respective metals, may be ranked (based on olefins yield) as V (16.9%) < Cr (17.5%) < Ce (25.1%) < Zr (26.2%) < Ni (26.8%) < Mg (27.9%). The reactivity of the lattice oxygen was estimated from energy of formation of the corresponding metal oxides. Correlation between the selectivity to propene and the standard energy of formation was attempted. Although there was no clear correlation, the result suggested that the lattice oxygen play a key role in the selectivity-determining step.     

Study of Methanol‐tolerant Oxygen Reduction Reaction at Pt–Bi/C Bimetallic Nanostructured Catalysts

The nanostructured platinum–bismuth catalysts supported on carbon (Pt₃Bi/C, PtBi/C and PtBi₃/C) were synthesised by reducing the aqueous metal ions using sodium borohydride (NaBH₄) in presence of a microemulsion. The amount of metal loading on carbon support was found to be 10 wt.‐%. The catalyst materials were characterised by X‐ray diffraction (XRD), X‐ray fluorescence (XRF), transmission electron microscope (TEM) and electroanalytical techniques. The Pt₃Bi/C, PtBi/C and PtBi₃/C catalysts showed higher methanol tolerance, catalytic activity for oxygen reduction reaction (ORR) than Pt/C of same metal loading. The electrochemical stability of these nano‐sized catalyst materials for methanol tolerance was investigated by repetitive cycling in the potential range of –250 to 150 mV_MSE. Bi presents an interesting system to have a control over the activity of the surface for MOR and ORR. All Pt–Bi/C catalysts exhibited higher mass activities for oxygen reduction (1–1.5 times) than Pt/C. It was found that PtBi/C catalyst exhibits better methanol‐tolerance than the other catalysts.     

非贵金属氧还原电极催化剂研究进展

质子交换膜燃料电池(PEMFC)中普遍使用Pt作为阴极电催化剂,但由于Pt价格昂贵、储量稀少,PEMFC中使用大量的Pt,必然导致PEMFC制造成本的上升。因此,寻找一种能够部分或者完全达到Pt催化效果的非贵金属催化剂,成为一种可行的方法。本文对近年来非贵金属氧还原电极催化剂的研究进行了总结,特别是不同催化剂的制备方法、反应机理及活性中心进行了梳理,并对非贵金属氧还原电极催化剂的发展进行了展望。     

Oxidative Dehydrogenation Properties of Novel Nanostructured Polyoxovanadate Based Materials

Abstract  

A comparative study of the catalytic oxidative dehydrogenation of propane by a novel polyoxovanadate based open-framework material (Co-POV)—[Co₃V₁₈O₄₂(H₂O)₁₂(XO₄)]·24H₂O (X = V, S), which is composed of nanometer size vanadium oxide clusters interlinked by cobalt oxide {–O–Co–O–} motifs, showed that Co-POV has superior catalytic property as compared to its individual metal oxide constituents, vanadium oxide and cobalt oxide, and their mixture, with high propylene selectivity.     

Oxidative Dehydrogenation of n-Butane: Activity and Kinetics Over VO x /Al2O3 Catalysts

The catalytic activity of a VO _x /Al₂O₃ catalyst for the oxidative dehydrogenation of n-butane is investigated. The effects of reaction temperature, oxygen to n-butane ratio and GHSV on the catalytic performance are examined and optimized. Interestingly, this simple catalyst gives good conversion and selectivity. Butane was 22–24 %, and the selectivity to C₄ alkenes was 56 %, of which 20–22 % to 1,3-butadiene. Moreover, the catalyst is stable for at least 72 h on stream. Kinetic studies show that the activation barriers for the formation of (butene + butadiene), CO and CO₂ amount to 70.2, 65 and 81.3 kJ/mol respectively.     

Oxidative Dehydrogenation of n-Butane: Activity and Kinetics Over VO x /Al2O3 Catalysts

The catalytic activity of a VO _x /Al₂O₃ catalyst for the oxidative dehydrogenation of n-butane is investigated. The effects of reaction temperature, oxygen to n-butane ratio and GHSV on the catalytic performance are examined and optimized. Interestingly, this simple catalyst gives good conversion and selectivity. Butane was 22–24 %, and the selectivity to C₄ alkenes was 56 %, of which 20–22 % to 1,3-butadiene. Moreover, the catalyst is stable for at least 72 h on stream. Kinetic studies show that the activation barriers for the formation of (butene + butadiene), CO and CO₂ amount to 70.2, 65 and 81.3 kJ/mol respectively.

     

Oxidative Dehydrogenation of Propane with CO2 Over Cr/H[B]MFI Catalysts

Abstract  

Cr/silicalite-1 and Cr/H[B]MFI catalysts were prepared by the impregnation method, and Cr/H[B]MFI were further treated by steaming. The catalysts were employed for the oxidative dehydrogenation of propane to propylene with CO₂ as the oxidant. Cr/H[B]MFI showed significantly higher catalytic activity than Cr/silicalite-1, and steamed Cr/H[B]MFI was superior in the reaction stability to Cr/H[B]MFI. The nature of the supported chromium species have been characterized by a number of physicochemical techniques, such as Raman, UV–vis and NMR. It is concluded that the steaming led to the auto-reduction of some Cr⁶⁺ to Cr³⁺, and resultant Cr³⁺ species might be located near the boron center in the borosilicate framework to counterbalance the negative charge of the framework. The transformation of Cr⁶⁺ species to Cr³⁺ species, facilitated by the steaming process and the presence of boron in the catalyst, is responsible for the enhanced stability of oxidative dehydrogenation of propane to propylene with carbon dioxide as the oxidant.     

铁酸盐系列丁烯氧化脱氢催化剂研究进展

综述了铁酸盐系列催化剂(Fe系催化剂)在丁烯氧化脱氢反应中的应用研究进展,介绍了Fe系催化剂的活性中心和氧化脱氢机理,分析了催化剂的失活原因,详述了助剂对Fe系催化剂催化性能的影响,并对Fe系催化剂的发展方向进行了展望。开发出高反应活性、高选择性和高强度的新一代Fe系丁烯氧化脱氢制丁二烯的高效催化剂,是今后的主要研究方向,同时,开发资源利用率高、低投资、低生产成本和废水量少的丁烯氧化脱氢工艺也非常关键。     

Nanostructured Oxide Catalysts for Oxidative Activation of Alkanes

The valorization of light alkanes via catalytic oxidative dehydrogenation (ODH) and selective oxidation is, with a few exemptions, still not solved. Oxide catalysts play a foremost role in these reactions. The control of the nanostructure brings new ways to tune their catalytic properties, but to date this has been little explored for alkane activation. This paper offers an overview of the applications of nanostructured oxide catalysts to oxidative activation of alkanes. Relevant examples of their unusual performance, the improvement of activity and selectivity attained by these oxides, and the new features brought by ordered mesoporous oxides, are discussed. Application of nanotechnology to oxides brings both new challenges and opportunities for catalytic applications. To make the most of it, a broad multidisciplinary approach, and bridging the lack of communication among the various research areas (electronics, materials, catalysis) involved, are needed. Dedicated to the founders and the members of Institute of Catalysis and Surface Chemistry, on the 40th anniversary of its foundation.     

Role of CO2 During Oxidative Dehydrogenation of Propane Over Bulk and Activated-Carbon Supported Cerium and Vanadium Based Catalysts

Catalysis Letters - CeO2, V2O5 and CeVO4 were synthesised as bulk oxides, or deposited over activated carbon, characterized by XRD, HRTEM, CO2-TPO, C3H8-TPR, DRIFTS and Raman techniques and tested...     

Chromium Oxide Supported on Mesoporous SBA-15 as Propane Dehydrogenation and Oxidative Dehydrogenation Catalysts

The catalytic activity and selectivity of Cr₂O₃ supported on mesoporous SBA-15 for non-oxidative and oxidative dehydrogenation of propane by O₂ and CO₂ have been studied and compared with those of Cr₂O₃/ZrO₂ and Cr₂O₃/-Al₂O₃ catalysts. Cr₂O₃/SBA-15 and Cr₂O₃/ZrO₂/SBA-15 are more selective to propene and more resistant to coking in comparison with Cr₂O₃/ZrO₂ and Cr₂O₃/-Al₂O₃ for non-oxidative dehydrogenation of propane. In oxidative dehydrogenation of propane by O₂ and CO₂, Cr₂O₃/SBA-15 also displays better activity, selectivity and stability than the other two supported catalysts. The propane conversion and propene yield on Cr₂O₃/SBA-15 catalyst for oxidative dehydrogenation of propane by CO₂ at 823 K reach 24.2 and 20.3%, respectively. XPS and TG/DTA have been used to characterize the catalysts before and after reaction. The differences in catalytic behavior of various supported Cr₂O₃ catalysts in the reactions have been discussed on the basis of the characterization results.     

Oxidative Dehydrogenation of Cyclohexane to Cyclohexene over Mg-V-O Catalysts

The oxidative dehydrogenation of cyclohexane was studied over Mg-V-O catalysts with different Mg/V atomic ratios. Catalysts were prepared via citric acid complexation and characterized by N₂-adsorption, XRD, FT-IR, Raman spectroscopy, NH₃-TPD and H₂-TPR techniques. Among the pure magnesium vanadates, Mg₃(VO₄)₂ has the isolated active sites, weakly basic surface and lower reducibility of the metal cations, and could be recognized as the catalytic active phase. Furthermore, a series of mechanically mixed catalysts were studied in the reaction in attempting to investigate the synergetic effect. The finding revealed synergetic effects in the conversion, in the yield, and in the selectivity were observed in Mg₃(VO₄)₂ mixing with a suitable amount of MgO and Mg₂V₂O₇ due to a solid solution of MgO in the Mg₃(VO₄)₂ phase and the remote control mechanism, respectively. Among the biphasic catalysts, (7/4)MgVO catalyst exhibited a better catalytic performance, on which a cyclohexene selectivity of 45.7% at cyclohexane conversion of 13.9% was obtained.     

The Oxidative Dehydrogenation of Ethylbenzene. Cobalt Molybdate Catalysts

The role of the catalyst and feed composition in the conversion and product distribution in the oxidative dehydrogenation of ethylbenzene, using a series of cobalt molybdate catalysts, was investigated.