类水滑石型催化剂用于二氧化碳气氛下乙苯脱氢

通过焙烧类水滑石前驱体制备催化剂载体,采用浸渍法制备了铁系列催化剂.实验结果表明,这种结构对于乙苯脱氢有促进作用,而且活性组分Fe附载在载体上时的活性比直接作为结构中的离子时的活性更好.此外,脱氢反应随着CO2分压增加,乙苯的转化率先升高后降低,最后保持在39%左右.     

Supported Vanadia Catalysts for Dehydrogenation of Ethylbenzene with CO2

Alumina supported vanadia catalysts (V/Al) for selective oxidehydrogenation of ethylbenzene with CO₂ were prepared by impregnation method. During preparation the effect of promoters and calcined temperature was investigated, it was found these two items had a strong influence on the activity of V/Al catalysts. Dehydrogenation reaction with CO₂ was happened in the fixed-bed reactor at 450 °C. Results showed that 15.2% ethylbenzene conversion and 99.2% styrene selectivity were acquired when V₂K/Al catalyst was used.     

Novel Perovskite-Type Oxide Catalysts for Dehydrogenation of Ethylbenzene to Styrene

We investigated novel LaMnOx perovskite-oxide (ABO₃) catalysts for effective catalytic dehydrogenation of ethylbenzene to produce styrene monomer. Comparison with industrial Fe–K catalyst, our La_0.8Ba_0.2Mn_0.6Fe_0.4O_3-δ catalyst showed higher activity. Results show that the A-site in perovskite-type oxides affected catalytic dehydrogenation activities and that the B-site affected stability of the activities.     

苯乙烯及乙苯脱氢制苯乙烯催化剂的现状和发展

对国内外苯乙烯的生产能力和市场需求进行了评述,并着重探讨乙苯脱氢制苯乙烯催化剂的研究现状,分析了该领域的发展趋势,指出了国内催化剂存在的差距和新品开发原则,提出了催化剂的开发建议。     

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.     

Oxidative Dehydrogenation of Ethylbenzene with Carbon Dioxide over Metal-Doped Titanium Oxides

Various metal-doped (Fe, V, Zr, Mg) titanium oxides were prepared by an acid-catalyzed sol–gel method and their properties as catalysts were investigated for oxidative dehydrogenation of ethylbenzene in the presence of carbon dioxide. The characterization techniques, XRD, BET, TGA were employed to analyze the features of catalyst. Fe₃Ti catalyst was found to be quite effective among the catalysts tested at 823 K, 39.8% ethylbenzene conversion and 98% styrene selectivity were acquired.     

乙苯氧化脱氢制苯乙烯催化机理及催化过程分析

采用乙苯氧化脱氢过程不仅可以突破热力学平衡的限制, 并且降低了生产过程的能耗。该过程的关键是开发出高活性及高选择性的催化剂。以V-Mg-O为代表的金属氧化物型催化剂遵循典型的Redox机理。影响催化剂性能的主要因素有催化剂的晶相组成、表面电子特性和表面酸行, 同时工艺条件诸如反应温度、O₂浓度、EB空速及水蒸汽用量等也影响着催化剂的性能, 其中催化剂的晶相组成起着决定性作用。     

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。     

Iron Oxide Catalysts for Dehydrogenation of Ethylbenzene in the Presence of Steam

Catalyst research for ethylbenzene (EB) dehydrogenation has been interest to many chemical manufacturers because styrene monomer is such a large-volume chemical and a steady growth of styrene markets is predicted. EB is relatively easy to dehydrogenate and the reaction may be effected by a simple thermal gas-phase process as observed by Berthelot in 1869 [l]. However, a much higher selectivity to styrene is obtained by contact catalysts. The historical evolution of EB dehydrogenation processes has been summarized by Kearby [21 and others [3].     

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.     

Promoted NiO Catalysts for the Oxidative Dehydrogenation of Ethane

Metal oxide promoted NiO catalysts with a Ni/(Me + Ni) atomic ratio 0.92 have been investigated for the oxidative dehydrogenation of ethane. These materials have been characterized by several techniques (N₂-adsorption, X-ray diffraction, X-ray photoelectron spectroscopy and Fourier transformed infrared spectroscopy of adsorbed CO and ethylene). The nature of surface sites is strongly influenced by the valence and the acid/base characteristics of the metal oxide promoters, which have a great impact on the selectivity to ethylene. Accordingly, a clear correlation between selectivity to ethylene and the valence of the promoter has been observed in the present work. Additionally, the acidity of the catalyst also enhances the selectivity to ethylene.     

锂对二氧化碳气氛下乙苯脱氢催化剂铁(Fe)/活性炭(AC)的促进作用

研究了助剂Li对CO2气氛下活性炭负载的Fe氧化物(Fe/AC)催化剂上的乙苯脱氢性能的影响和CO2的作用。助剂Li的添加提高了Fe/AC催化剂在CO2气氛下的乙苯脱氢活性和稳定性;CO2气氛下的苯乙烯收率明显高于N2气氛下,表明CO2显著促进了乙苯脱氢反应。     

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.     

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).     

Study of Mn-based Catalysts for Oxidative Dehydrogenation of Cyclohexane to Cyclohexene

The gas-phase oxidative dehydrogenation (ODH) of cyclohexane to cyclohexene in the presence of molecular oxygen has been studied over various Mn-based catalysts. It is found that LiCl/MnO_x/PC (Portland cement) catalyst exhibits the highest catalytic performance, and a 42.8% cyclohexane conversion, 58.8% cyclohexene selectivity and 25.2% cyclohexene yield can be achieved under 600 °C, 20,000 h⁻¹ and C₆H₁₂/O₂/N₂=14/7/79. There are good correlations between the selectivities to cyclohexene and the electrical conductivities of Li doped Mn-based catalysts, from which it is deduced that the non-fully reduced oxygen species (O₂⁻, O₂²⁻, O⁻) involved in a new phase of LiMn₂O₄ might be responsible for the high selectivity toward cyclohexene, whereas the Mn₂O₃ crystal phase results in the CO_x formation. The selectivity to cyclohexene increases with increasing molar ratio of Li to Mn in LiCl/MnO_x/PC.     

Dehydrogenation of Ethylbenzene in the Presence of CO2 over V Catalysts Supported on Nano-sized Alumina

Carbon-covered alumina (CCA) were synthesized from mesoporous alumina and a series of carbon sources (including sucrose, furfuryl alcohol, and benzene). They had structural properties of alumina and surface characteristics of carbon. When they were used as supports for molybdenum carbide, nitride, and phosphide catalysts, significantly higher activities were obtained in hydrazine decomposition as compared to those supported on the conventional alumina. The difference in the interactions of catalytic active sites with the CCA and with the alumina supports was preliminarily deemed to be the main cause of the better performance of CCA supported catalysts. Carbon contents on alumina and carbon sources were found to be important for CCA to be a good support. Carbon deposited on alumina in a near monolayer form showed the best activities. In contrast with sucrose and furfuryl alcohol, benzene as the carbon source readily yielded CCA supports with a hydrophobic surface, which resulted in relatively low dispersions of metal and, in turn, decreased activity of the supported catalysts.