Oxidative Dehydrogenation of Ethane over Ce-based Monolithic Catalysts using CO2 as Oxidant

Highly active Ce-based monolithic catalysts for oxidative dehydrogenation of ethane with CO₂ were prepared and characterized by various techniques. The high oxidation state Ce⁴⁺ species had higher catalytic activity than the Ce³⁺ species in the monolithic catalysts. The Ce⁴⁺ species was reduced to Ce³⁺ species in the ethane dehydrogenation process, and the reduced Ce species was reoxidized to the Ce⁴⁺ species by treatment with CO₂ at 750 °C, the Ce redox cycle played an important role in the catalyst’s high activity.     

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.     

Continuous Oxygen Ion Transfer Medium as a Catalyst for High Selective Oxidative Dehydrogenation of Ethane

An oxygen permeable mixed ion and electron conducting membrane (OPMIECM) was used as an oxygen transfer medium as well as a catalyst for the oxidative dehydrogenation of ethane to produce ethylene. O^2- species transported through the membrane reacted with ethane to produce ethylene before it recombined to gaseous O², so that the deep oxidation of the products was greatly suppressed. As a result, 80% selectivity of ethylene at 84% ethane conversion was achieved, whereas 53.7% ethylene selectivity was obtained using a conventional fixed-bed reactor under the same reaction conditions with the same catalyst at 800 °C. A 100 h continuous operation of this process was carried out and the result indicates the feasibility for practical applications.     

A Comparison of Catalytic Oxidative Dehydrogenation of Ethane Over Mixed V-Mg Oxides and Over Those Prepared via a Mesoporous V-Mg-O Pathway

The catalytic oxidative dehydrogenation of ethane was investigated in a fixed-bed tubular microreactor at 500, 550 and 600 °C and a space velocity of 35 027ml g^-1h^-1. Two kinds of V-Mg oxides catalysts containing various V/Mg atomic ratios were employed. One group of catalysts was prepared by the solid reaction between fine powders of vanadium pentoxide and magnesium nitrate and the other ones were obtained from mesostructured V-Mg-Os. For the former catalysts, it was found that the selectivity to ethene increased and the conversion of ethane passed through a maximum with increasing V/Mg atomic ratio. For the catalysts obtained from the mesoporous materials, an optimum V/Mg atomic ratio was found, for which the conversion of ethane and the selectivity to ethene were maxima. Compared with the mixed-oxide catalysts, those obtained from the mesoporous materials exhibited much higher yields to ethene. Several new phases, such as pyro-Mg₂V₂O₇, ortho-Mg₃(VO₄)₂ and meta-MgV₂O₆, formed between magnesia and vanadia, were identified by XRD in the mixed V-Mg oxide catalysts; they may be responsible for the catalytic activity. In the catalysts prepared from mesoporous V-Mg-O, a V₂O₃ phase, which may contain highly dispersed magnesium, was identified and suggested to be responsible for the higher catalytic performance.     

Highly Selective Supported Alkali Chloride Catalysts for the Oxidative Dehydrogenation of Ethane

Binary, ternary and quaternary molten eutectic alkali chloride catalysts, supported on mildly redox active oxides, were investigated for the oxidative dehydrogenation of ethane. The influence of different support oxides, on the catalytic performance, as well as that of different anions (bromide vs. chloride) and cations in a chloride eutectic system were studied. Metal oxides which react with chlorides are not suitable and lead to substantial deactivation. Especially supports forming volatile chlorides induce irreversible chloride depletion. Bromides catalyze oxidative dehydrogenation of ethane with higher rates, but lower olefin selectivities, highlighting the similarities and differences of Cl^? and Br^? in the redox cycle. Two catalysts were identified having olefin selectivities up to 98 % at 70 % ethane conversion, which ranges among the highest selectivities reported for ethane ODH.     

乙烷催化氧化脱氢制乙烯催化剂研究进展

介绍了目前几种乙烯的制备技术,认为使用乙烷催化氧化脱氢来制乙烯的方法较好.分析了乙烷催化氧化脱氢制乙烯机理,叙述了此方法反应过程中使用的4类催化剂,即过渡金属氧化混合物类、碱金属及碱土金属类、稀土类和贵金属类,分别介绍了它们的研究进展情况,其中过渡金属氧化催化剂中的氧化镍类在较低的反应温度下有较高的选择性,且原料来源丰...     

Combinatorial Heterogeneous Catalysis: Oxidative Dehydrogenation of Ethane to Ethylene, Selective Oxidation of Ethane to Acetic Acid, and Selective Ammoxidation of Propane to Acrylonitrile

The application of combinatorial methods to three reactions catalyzed by multimetal oxides is described. Catalysts for the oxidative dehydrogenation of ethane to ethylene were tested using a 121- or 144-channel scanning mass spectrometer primary screening reactor and a 48-channel fixed bed secondary screening reactor; catalysts for the selective oxidation of ethane to acetic acid were tested using a 256-channel massively parallel microfluidic reactor primary screen alone, and catalysts for the selective ammoxidation of propane to acrylonitrile were tested using the massively parallel microfluidic reactor and an eight-channel fixed bed secondary/tertiary screening reactor. The details regarding catalyst design, synthesis, and screening are presented. This work has resulted in both the confirmation of published results and the generation of new lead materials for all three chemistries.     

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.     

Na-W-Mn-Zr-S-P/SiO_2催化剂上乙烷氧化脱氢反应

研究了甲烷氧化偶联六组分Na-W-Mn-Zr-S-P/SiO_2催化剂对乙烷氧化脱氢反应的催化性能.考察了不同原料气配比、温度和空速等条件下的催化剂活性.讨论了催化剂中S或P组分的含量对催化活性的影响.实验结果表明,S和P元素的加入可以提高催化剂的活性.660℃时六组分催化剂上乙烷的转化率为65.2%,乙烯的选择性为83.2%,此时得到的乙烯收率最高.乙烷与氧气比的增加有利于提高乙烯的选择性.较低反应温度时,空速的增加可以抑制碳氧化物(CO,CO_2)的生成,提高乙烯选择性.     

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...     

Surface Properties and Reactivity of Al2O3-Supported MoO3 Catalysts in Ethane Oxidative Dehydrogenation

The effect of MoO₃ loading on the properties and the catalytic performance of a series of alumina-supported molybdena catalysts (0–30 wt% MoO₃) was investigated in the oxidative dehydrogenation of ethane. The molybdena species on alumina were found to be amorphous at submonolayer coverages. At higher loadings, the formation of Al₂(MoO₄)₃ crystallites was detected by XRD. XPS revealed the existence of both Mo(VI) and Mo(V) sites on the catalyst surface, the concentration of which depends on the MoO₃ loading. In terms of catalytic performance, the activity increases with increasing loading in the submonolayer regime, decreasing for higher loadings. High selectivity to ethene is obtained even at relatively high conversion levels for catalysts exceeding monolayer coverage.     

Increasing the Equilibrium Yield of Oxidative Dehydrogenation with CO2 by Secondary Reactions

Oxidative dehydrogenation with carbon dioxide as an oxidant at low temperatures is strongly limited by its thermodynamic equilibrium. It is be shown that the equilibrium yield of the desired olefin can significantly be increased utilizing side reactions. This does not necessarily require the addition of another reactant, since this reactant can be formed in situ from the starting alkane. This effect allows for a decrease of the reaction temperature as well as the overall heat demand of the reaction. As a consequence, the exergy demand of the reaction system is reduced substantially.     

Multiple Oxidative Dehydrogenative Functionalization of Arylacetaldehydes Using Molecular Oxygen as Oxidant Leading to 2‐Oxo‐acetamidines

A novel copper‐catalyzed, multiple oxidative dehydrogenative functionalization of arylacetaldehydes leading to 2‐oxo‐acetamidine compounds has been developed. This transformation is highly efficient with dissociation of six hydrogens including two sp³ C H and one sp² C H bond activations. This method not only provides an efficient approach to 2‐oxo‐acetamidine compounds, but also offers a valuable mechanistic insight into this novel copper catalysis.     

Ozonated Multiwalled Carbon Nanotubes as Highly Active and Selective Catalyst in the Oxidative Dehydrogenation of Ethyl Benzene to Styrene

Purification and ozonation protocols for the functionalization of multiwalled carbon nanotubes (MWCNT) were developed to modify the surface with respect to increasing the catalytic activity of the samples in the oxidative dehydrogenation of ethyl benzene (ODEB) to styrene. The modification processes drastically enhance the Brunauer‐Emmett‐Teller surface area and the number of oxygen‐containing groups on the surface of the nanotubes. The modified MWCNT exhibit significantly improved conversion and styrene selectivity in the ODEB reaction. For instance, ozonation led to MWCNT‐based catalysts revealing conversion and selectivity values of 80 % and 92 %, respectively. An increase in surface oxygen accompanied by high catalytic activity observed on the catalysts suggests that oxygen‐containing groups are the dominant active sites for the reaction.     

改性VOx/MSU-1催化剂上CO2氧化异丁烷脱氢反应

以MSU-1为载体制备了一系列改性的VOx/MSU-1催化剂,并在CO2氧化异丁烷脱氢制异丁烯的反应中评价了催化剂的性能,发现稀土元素La、Ce的加入能提高催化剂的活性。采用XRD、H2-TPR及NH3-TPD方法对催化剂La2O3-VOx/MSU-1进行了深入的表征,发现La2O3的加入提高了载体MSU-1上活性组分VOx的分散度,同时也改善了催化剂表面的酸碱性,更加有利于异丁烷氧化脱氢反应的进行。优化了反应条件,在最佳反应条件下,异丁烷的转化率为63.6%,异丁烯的产率为52.3%。最后,通过8 h的稳定性实验,发现与VOx/MSU-1相比,催化剂La2O3-VOx/MSU-1具有更好的催化稳定性。     

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.     

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.

     

烃类晶格氧选择氧化制顺酐的强制周期操作反应技术

综述了烃类选择氧化制顺酐的生产工艺、反应技术。重点介绍了人为非定态催化反应技术的特点及在烃类晶格氧选择氧化反应中的应用 ,并对烃类选择氧化制顺酐反应提出了今后研究的方向。