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 Propane on Calcium Hydroxyapatites Partially Substituted with Vanadate

Solid solutions of phosphate and vanadate calcium hydroxyapatites were synthesized and the catalytic activities for the oxidative dehydrogenation of propane to propylene on those catalysts were examined. Although the conversion of propane and the selectivity to propylene were 7.6 and 3.5% on calcium hydroxyapatite (CaHAp), the incorporation of vanadate to CaHAp by V/P=0.05 (atomic ratio) resulted in the enhancement of the conversion and the selectivity to 17.2 and 52.4%, respectively, corresponding to those on Mg₂V₂O₇ under the same reaction conditions (14.0 and 50.9%, respectively).     

Oxidative Dehydrogenation of Propane over Mesoporous HMS Silica Supported Vanadia

Vanadium-containing mesoporous HMS catalysts have been prepared and characterized for the oxidative dehydrogenation (ODH) of propane. It is demonstrated that the vanadium supported HMS catalysts exhibit a much higher catalytic activity than the literature results obtained over the vanadium supported MCM-41 catalysts in the ODH of propane. The improved catalytic activity of the V-HMS catalysts has been attributed to the presence of high concentration of well-dispersed vanadium species on the surface of the mesoporous HMS materials.     

PtSnNa/Al2O3催化剂丙烷脱氢反应性能研究

采用氢化学吸附、热重和程序升温还原等多种物理化学手段结合微型催化反应研究了添加Na＋对负载型PtSn/γ-Al2O3催化剂丙烷脱氢反应性能、催化剂表面酸性、金属表面性质以及负载组分-载体相互作用的影响.发现添加一定量的Na＋可以减少催化剂的积炭量,提高催化剂的金属表面裸露度,从而改善催化剂的脱氢反应稳定性.而引入较多的Na＋虽可以提高催化剂抗积炭性能,但破坏了Pt-Sn-Al2O3之间的相互作用,锡组分易被还原,催化剂活性表面减小,从而对催化剂脱氢反应活性有抑制作用.     

丙烷临氢脱氢催化剂的研究进展

综述了以Al2O3为催化剂载体的丙烷脱氢催化剂的研究进展,重点阐述了Pt-Sn／γ-Al2O3催化剂的研究现状;论述了ZSM-5和尖晶石载体的特殊结构和性质以及适应高温、低压的反应条件,制得具有良好的反应活性和稳定性的催化剂的方法;对丙烷临氢脱氢制丙烯催化剂的研究前景进行了展望。     

丙烷氧化脱氢负载型催化剂的研究

制备了V2O5/TiO2和V2O5/TiO2 ZrO2负载型催化剂,并对催化剂进行了反应评价和BET、XRD、H2-TPR表征。通过研究验证了利用溶胶凝胶技术制备的负载TiO2催化剂有较好的低温反应活性,在250℃下反应得到2 2%的丙烯收率。对TiO2进行离子掺杂后催化剂活性组分能够和混合氧化物载体进行键合,形成稳定的O—V—Zr键和O—V—Ti键,使催化剂的还原温度从480℃增加到650℃,在350℃下反应得到12%的丙烷转化率和55%的丙烯选择性。     

Effect of Tetrachloromethane on Redox Behaviors of Copper(II) Oxide in the Oxidative Dehydrogenation of Propane

The oxidative dehydrogenation of propane on CuO has been investigated at 723 K in the presence and absence of tetrachloromethane (TCM). Under oxygen-limiting conditions, the conversion of propane and the selectivity to propylene were enhanced by the introduction of TCM. The catalyst converted to metallic Cu during the oxidation in the absence of TCM while no conversion of CuO was observed in the sample used in the presence of TCM. In contrast, the conversion of propane dramatically decreased upon addition of TCM into the feedstream for the oxidation of propane under the oxygen-excess conditions. The catalyst used under the oxygen-excess conditions was not reduced to metallic Cu, regardless of the addition of TCM. It is suggested that an abstraction of lattice oxygen from the catalyst is strongly influenced by the concentration of oxygen in the feed, resulting in the different effect of TCM on the oxidative dehydrogenation of propane.     

Highly Effective Oxidative Dehydrogenation of Propane Over Vanadia Supported on Mesoporous SBA-15 Silica

Vanadia-containing mesoporous SBA-15 catalysts were prepared and characterized for the oxidative dehydrogenation (ODH) of propane. It is demonstrated that the vanadia-supported SBA-15 catalysts exhibit a much higher catalytic activity than those reported in the literature obtained over vanadium-supported mesoporous MCM-41 catalysts in the ODH of propane. The high catalytic performance of the mesoporous SBA-15 catalysts is attributed to the particularly large pore diameters and low surface acidity.     

碱金属离子对丙烷脱氢催化剂中活性组分与载体间作用的影响

用程序升温还原（TPR）研究了添加Li^ 、Na^ 、K^ 等碱金属离子对丙烷脱氢催化剂中活性组分与载体间作用的影响。结果表明，Li^ Na^ 的引入对Sn-Al2O3之间的作用影响很小，而K^ 引入很大程度地削弱了PtSn/Al2O3催化剂中Sn组分与载体之间的相互作用，使得锡离子容易还原成金属态的Sn，易形成PtSn合金，使催化剂中毒。     

丙烷脱氢制丙烯经济及技术分析

丙烯是重要的有机化工原料，除用于生产聚丙烯外，还是生产丙烯腈，丁醇、辛醇、环氧丙烷、异丙醇、丙苯、丙烯酸、羧基醇及壬基酚等产品的主要原料，丙烯的齐聚物是提高汽油辛烷值的主要成分，丙烷催化脱氢制丙烯比烃类蒸气裂解能产生更多的丙烯。当用蒸气裂解生产丙烯时，丙烯收率最多只有33％、而用催化脱氢法生产丙烯，总收率可达74％－86％，用唯一原料生产唯一产品，催化脱氢的设备投资比烃类蒸气裂解低33％。并且采用催化脱氢的方法，能有效地得用液化石油气资源使之转变为有用的烯烃。     

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.     

纳米氧化镍的乙烷氧化脱氢催化性能研究

采用溶胶-凝胶法制备了纳米氧化镍催化剂,其具有较好的低温催化乙烷氧化脱氢(ODHE)性能,通过SEM和XRD表征了该催化剂的形貌和结构,并研究了纳米NiO催化下ODHE反应的影响因素.     

环己烷气相氧化脱氢催化剂的研究进展

为了尽可能多地获得环己烯和充分利用苯选择加氢反应的副产物环己烷,环己烷氧化脱氢反应在近 20 年内得到迅速发展.环己烷氧化脱氢反应催化剂体系的选择对于获得较高的环己烯产率和选择性、较低的氧化脱氢反应温度以及最优的反应路径尤为重要.详细阐述了阳离子沸石催化剂、复合金属氧化物催化剂以及贵金属丝网催化剂等在环己烷氧化脱氢制取...     

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。     

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.     

Redox Behaviors of Magnesium Vanadate Catalysts During the Oxidative Dehydrogenation of Propane

In order to examine the mobility of lattice oxygen in magnesium vanadates, these catalysts were employed for the oxidative dehydrogenation of propane in the absence of oxygen for 2.25h, followed by the addition of gaseous oxygen into the feedstream. Depending on the degree of the abstraction of lattice oxygen from these catalysts during the oxidation in the absence of the gaseous oxidant, oxygen in the effluent was detected at approximately 1.4 and 9min with Mg₃V₂O₈ and Mg₂V₂O₇ respectively, after the addition of gaseous oxygen under the present reaction conditions. However, no oxygen was detected with MgV₂O₆ even after 18.5min from the addition of gaseous oxygen. ⁵¹V MAS NMR was also employed for the observation of redox behaviors of vanadium species in these catalysts during the reaction.     

The Oxidative Dehydrogenation of Propane Using Vanadium Oxide Supported on Nanocrystalline Ceria

Nanocrystalline ceria was prepared as a support for vanadium oxide catalysts and tested for the oxidative dehydrogenation of propane. Nanocrystalline ceria is very active for the total oxidation of propane under conditions used for oxidative dehydrogenation. The addition of vanadium results in a switch of activity to produce propene with appreciable selectivity. The catalyst performance depends on the vanadium loading. Lower vanadium loadings resulted in catalysts with highly dispersed vanadia species, which were selective towards propene production. Higher vanadium loadings resulted in the formation of a mixed cerium–vanadium phase, which was also active for propane selective oxidation. A catalyst with an intermediate loading was far less selective. Catalysts were characterised by a range of techniques (including XRD, laser Raman, TPR, SEM/EDX and XPS), and the activity of the catalysts can be related to their structure and chemistry.     

Evaluating the Catalytic Performances of SAPO-34 Catalysts for the Oxidative Dehydrogenation of Ethane

Acid silicoaluminophosphate SAPO-34 catalysts with a chabasite-related (CHA) structure were tested for the oxidative dehydrogenation of ethane in the temperature range 550-700 °C achieving very interesting catalytic performances (about 70% C₂H₄ selectivity at 45% ethane conversion) which were related to both Lewis and Brønsted acid sites, as found by a NH₃-TPD study.     

Oxidative dehydrogenation of n-butane over mesoporous VO x /SBA-15 catalysts

Mesoporous VO _x /SBA-15 catalysts with different V contents were evaluated for the oxidative dehydrogenation of n-butane and characterized by N₂ adsorption, XRD, HRTEM, H₂-TPR, NH₃-TPD, XPS, and EPR techniques. Compared to conventional V₂O₅/SiO₂ catalysts, the VO _x /SBA-15 catalysts showed better performance. The good performance can be attributed to the good dispersion of V species, presence of V⁴⁺ species and the pore structure.     

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.