丙烷脱氢制丙烯催化剂烧焦过程的模型化

在丙烷脱氢制丙烯反应过程中,由于焦的沉积使催化剂活性不断降低,而且失活速度很快,催化剂需频繁烧焦再生。在研究了丙烷脱氢催化剂烧焦过程内外扩散影响的基础上,采用内扩散效率因子修正的均匀烧焦物理模型,建立了综合考虑内外扩散影响的绝热固定床非均相动态烧焦数学模型,用于指导反应器的设计和操作优化。通过对Cr₂O₃/Al₂O₃脱氢催化剂烧焦过程模拟,可更深入地认识烧焦过程的变化规律。     

非贵金属催化剂用于丙烷脱氢的研究进展

丙烯是一种重要的工业原料，主要用于生产聚丙烯、丙烯腈、异丙醇、丙酮和环氧丙烷等。随着对丙烯需求的日益增长，丙烷脱氢技术已被广泛应用于丙烯工业生产中。铂基、铬基催化剂虽然在丙烷脱氢反应中的活性很高，却容易中毒失活。金属氧化物作为可替代型非贵金属催化剂被人们广泛关注。首先，介绍金属氧化物催化丙烷脱氢的反应路径及失活机理，指出增强C—H活化能力、缓解活性组分重构及还原是提高金属氧化物丙烷脱氢性能的关键。然后，对几种代表性的金属氧化物催化剂进行了详细的综述，总结归纳各类催化剂的作用机制及活性物种，并分析讨论相应催化剂存在的问题。最后提出未来丙烷脱氢催化剂的重点研究方向，有望为低碳烷烃活化直接制取化学品提供新的思路。     

丙烷脱氢制丙烯用单原子催化剂研究进展

丙烯是一种重要的有机化工原料和石油化工原料中间体,近年来在国内外市场的需求量持续增长。丙烷直接脱氢制丙烯技术具有收率高、技术成熟、经济环保等优点,备受研究者们的广泛关注。文中综述了丙烷直接脱氢制丙烯用单原子催化剂的研究进展,介绍了单原子催化剂的丙烷脱氢反应机理,探讨了单原子催化剂的失活行为,总结了活性组分、助剂及载体对单原子催化剂催化丙烷脱氢性能的影响,并分析讨论了单原子催化剂在当前研究中存在的问题。最后针对单原子催化剂虽具有优异的丙烯选择性和稳定性,但存在丙烷脱氢活性依旧不足的问题,提出了调控单原子催化剂电子结构促进丙烷脱氢活性的设计思路,为未来丙烷脱氢制丙烯高效单原子催化剂的设计提供了指导方向。     

铂基丙烷脱氢催化剂研究进展

丙烷脱氢（PDH）是一种直接生产丙烯的工业技术，受到了广泛的关注并实现了大规模应用。目前，商用铂基催化剂由于活性物质烧结和焦炭沉积而存在快速失活和稳定性差的问题。基于此，首先分析了铂基催化剂催化丙烷脱氢的反应动力学及活性位点，并指出铂基催化剂的分散性和稳定性是决定脱氢性能的关键因素。然后，从调控催化剂活性中心和载体修饰两个角度出发系统地总结了提高铂基丙烷脱氢催化剂稳定性策略。最后，对丙烷脱氢催化剂未来发展前景进行了展望，指出基于反应机理对铂基催化剂结构进行精准设计以及开发新型可替代铂基催化剂是目前丙烷脱氢工艺研究的重要方向，为丙烷脱氢制丙烯的进一步工业应用提供新的思路。     

苯酚直接羟化制备苯二酚催化剂失活过程研究

催化剂失活是一个复杂的物理和化学过程,失活原因多种多样,催化剂失活对催化过程的工艺流程、设备以及操作条件等的选择起着决定性的作用。本文对苯酚羟化用铁复合氧化物催化剂的失活情况进行了研究,考察了催化剂的寿命和催化剂活性随时间的变化关系,改变实验条件进行了催化剂活原因的分析。结果表明,催化剂8h左右开始失活,催化剂完全时间约为70h,催化剂失活的主要原因是由于活性组分从催化剂载体上流失引起。为了计算连续搅拌反应器中化催化剂的活性分布,便于反应器的设计和操作优化,关联了催化剂活性与时间的函数关系。     

丙烷催化脱氢反应宏观动力学模型

在温度580～640 ℃、压力0.1 MPa、原料气空速1000～6000 h－1条件下,采用Pt-Sn催化剂,在固定床积分反应器中进行了丙烷催化脱氢实验,建立了脱氢反应宏观动力学模型。根据实验数据,采用多元线性回归分析得到宏观动力学模型的参数,丙烷脱氢反应的活化能约为78.4 kJ/mol。经统计检验,结果表明所建立的丙烷催化脱氢宏观动力学方程是可靠的。     

GS-11催化剂催化乙苯脱氢制苯乙烯反应性能

为研究GS-11催化剂在绝热床反应器中催化乙苯脱氢制苯乙烯的反应性能,实验考察了反应温度、水比、压力和空速对乙苯脱氢制苯乙烯反应的影响。结果表明,提高水比或降低压力同时有利于乙苯转化率和苯乙烯选择性,提高温度或降低空速有利于乙苯转化率,不利于苯乙烯选择性。催速老化实验结果显示,GS-11催化剂的失活速率慢于参比催化剂,提高反应温度增强了GS-11催化剂耐低水比的能力。水比过低造成活性下降后,采取提温、低负荷活化或停乙苯通水蒸气处理,GS-11催化剂的性能得到恢复。     

镓对Pt-K/Al2O3催化剂在丙烷脱氢中活性的影响

以Al_2(SO_4)_3和NaAlO_2为原料,采用双铝法合成拟薄水铝石,再经高温焙烧制备了活性氧化铝载体。采用分步等体积浸渍法,在氧化铝载体上负载Ga、K和Pt,制备催化剂,并考察催化剂对丙烷脱氢制丙烯的催化性能。通过BET比表面分析,简单探讨了催化剂结构与催化剂失活再生的关系。结果表明,同时添加质量分数为1.5%的Ga和1.5%的K,制备的0.3Pt-1.5Ga-1.5K/Al_2O_3催化剂,对丙烷脱氢制丙烯有较高的催化活性,反应1h后,丙烷的转化率和丙烯的选择性分别为46.2%和81.3%。催化剂失活的主要原因是积碳覆盖了活性位,再生后,催化剂活性基本可以恢复到初始状态。     

Cr系丙烷脱氢催化剂研究进展

综述了Cr系丙烷脱氢催化剂的研究状况,介绍了使用Cr系丙烷脱氢催化剂的工艺和催化剂脱氢机理,探讨了Cr系催化剂的活性中心和失活原因,总结了影响铬铝催化剂催化性能的因素,包括制备、载体、助剂、积炭及工艺条件,对Cr系催化剂的研究前景进行了展望。     

丙烷脱氢制丙烯技术研究

介绍了催化脱氢、氧化脱氢、膜反应器脱氢等几种丙烷脱氢制丙烯技术，综述了丙烷催化脱氢制丙烯催化剂的研究现状，虽然丙烷催化脱氢生产丙烯已实现了工业化，但其催化剂的性能需进一步提高；对丙烷氧化脱氢制丙烯反应催化剂的研究现状及膜反应器在丙烷脱氢反应上所具有的优越性进行了描述，认为研发具有高稳定性和高透氢性能的氢分离膜，将有望能大幅度提高丙烯的收率。     

Oxidative dehydrogenation of propane to propene, 1: Kinetic study on V/MgO

The reaction kinetics of the oxidative dehydrogenation of propane to propene over a V/MgO catalyst were studied. Both propane and propene oxidation kinetics were measured independently to quantify the rates of the parallel and consecutive reactions to propene and carbon oxides. Specific experiments to evaluate reaction products effects showed that water inhibited reaction rates but co‐feeding CO₂ or propene had no measurable effect on selectivity or conversion. Kinetic data generated under integral reactor conditions and over an inert membrane reactor have also been used to estimate the kinetic parameters. Selectivity decreased as the oxygen partial pressure increased; however, propene yield was relatively insensitive to oxygen concentration. A dual site Mars‐van Krevelen model characterizes the reaction kinetics well. The role of lattice oxygen was established by alternating pulses of propane and oxygen. This redox model is able to predict the experimental tendencies observed in the three types of reactor studied.     

Oxidative dehydrogenation of propane in a perovskite membrane reactor with multi‐step oxygen insertion

A membrane reactor incorporating a hollow fiber with successive parts of oxygen permeable and passivated surface segments has been developed and was used for the oxidative dehydrogenation (DH) of propane. This membrane geometry allows a controlled oxygen feeding into the reactor over its axial length. In the oxidative DH, the thermodynamic limitation of propane DH can be overcome. By using this novel hollow fiber membrane reactor with a Pt/Sn/K DH catalyst, oxygen separation and propene formation could be established even at temperatures as low as 625°C with long‐term stability. Combining the hollow fiber membrane and the DH catalyst, the highest propene selectivity of 75% was observed at a propane conversion of 26% and 625°C whereas the best propene yield of 36% was obtained at 675°C (48% propene selectivity). The performance of this reactor is evaluated by applying various reaction conditions. © 2010 American Institute of Chemical Engineers AIChE J, 2010     

丙烷氧化脱氢制丙烯研究进展

开发新型丙烯制备工艺对于满足人们日益增长的丙烯需求具有重要意义。由于商业化无氧脱氢技术存在热力学平衡限制、反应温度高、催化剂易积炭等不足,近年来,人们将研究重心转向了丙烷氧化脱氢技术。本文简述了丙烷氧化脱氢制丙烯的发展现状,综述了近年来文献报道的丙烷氧化脱氢催化剂体系（V基、Cr基、Co基、Ni基、Mo基、Pt基、Ce基和非金属基催化剂）、机理研究和不同氧化剂选择,并对各自的优势和不足进行了简单分析。分析发现,虽然目前丙烷氧化脱氢催化剂的种类非常广泛,但产物丙烯的收率仍有待提高,机理研究也需要更加系统和深入。最后指出,系统研究丙烷氧化脱氢机理,并在此基础上开发先进催化剂,进一步提高丙烯的选择性和收率是未来丙烷氧化脱氢研究的重要方向。     

Selective conversion of propane to propene by the catalytic oxidative dehydrogenation over cobalt and magnesium molybdates

Catalytic performances of various metal molybdates were tested in the oxidative dehydrogenation of propane to propene with molecular oxygen under an atmospheric pressure. Most of the molybdates tested promoted the selective oxidative conversion of propane to propene and among them cobalt and magnesium molybdates were found highest in the activity and selectivity. It was also found that their catalytic activities were highly sensitive to the catalyst composition, and it turned out that Co_0.95MoO _x and Mg_0.95MoO _x catalysts which have slightly excess molybdenum showed the highest activity in the oxidative dehydrogenation of propane. Under the optimized reaction conditions, higher reaction temperatures and lower partial pressures of oxygen, these catalysts gave 60% selectivity to propene at 20% conversion of propane. Since the molybdates having the surface enriched with molybdenum oxide tended to show high activity for the propane oxidation, surface molybdenum oxide clusters supported on metal molybdate matrix seem to be the active sites for the selective oxidative dehydrogenation of propane.     

Simulation of Propane Dehydrogenation to Propylene in a Radial‐Flow Reactor over Pt‐Sn/Al2O3 as the Catalyst

Catalytic paraffin dehydrogenation for manufacturing olefins is considered to be one of the most significant production routes in the petrochemical industries. A reactor kinetic model for the dehydrogenation of propane to propylene in a radial‐flow reactor over Pt‐Sn/Al₂O₃ as the catalyst was investigated here. The model showed that the catalyst activity was highly time dependent. In addition, the component concentrations and the temperature varied along the reactor radius owing to the occurring endothermic reaction. Moreover, a similar trend was noticed for the propane conversion as for the propylene selectivity, with both of them decreasing over the time period studied. Furthermore, a reversal of this trend was also revealed when the feed temperature was enhanced or when argon was added into the feed as an inert gas.     

丙烷脱氢制丙烯研究新进展

介绍了丙烷催化转化制丙烯的研究状况,综述了丙烷催化脱氢制丙烯的铬系催化剂、铂系催化剂及其助剂Sn的研究进展;评述了丙烷氧化脱氢反应机理低温和高选择性的催化剂及膜反应器在丙烷脱氢反应上所具有的优越性,认为研发具有高稳定性和高透氢性能的氢分离膜,将有望能大幅度提高丙烯的收率。     

Oxidative dehydrogenation of propane over catalysts based on carbon nanofibers

Carbon nanofibers (CNF) and CNF-supported phosphoric oxides were tested as the catalysts for oxidative dehydrogenation of propane (ODP). The catalysts were characterized by SEM, TEM, X-ray diffraction (XRD), N₂ adsorption and temperature-programmed surface reaction (TPSR). CNF itself is an effective catalyst for ODP, but the high propene yield can only be achieved at high reaction temperature, which would cause CNF gasification. CNF-supported phosphoric oxides can operate at 500 °C without gasification and a 39.63% propene selectivity could be reached at a 42.07% propane conversion. Carbonyl-like groups on the CNF surface could be the active sites for ODP.     

Comparison of different catalysts in the membrane-supported dehydrogenation of propane

Dehydrogenation of propane is studied in a high temperature packed bed catalytic membrane reactor with a hydrogen-selective silica membrane. The silica membrane is prepared by a two-step sol–gel process. The removal of hydrogen in the membrane reactor results in higher propane conversion and higher propene yields in comparison to an equivalent fixed-bed reactor. Unfortunately, as a result of the H₂ removal coking is favoured in the membrane reactor. Therefore, the higher propene yields are found only for the first 100–120 min time on stream. However, the lower selectivity of the membrane reactor due to coking is compensated to some extend by a reduced hydrogenolysis. Two commercial dehydrogenation catalysts of different activity were tested in the membrane reactor: Cr₂O₃/Al₂O₃ and Pt–Sn/Al₂O₃. The two catalysts show a different activity, coking, and regeneration behaviour in the membrane-supported propane dehydrogenation.     

Propane Oxidative Dehydrogenation Over Ln–Mg–Al–O Catalysts (Ln = Ce, Sm, Dy, Yb)

Ln–Mg–Al mixed oxide catalysts (Ln = Ce, Sm, Dy, Yb) were prepared from layered double hydroxide precursors, characterized using XRD, N₂ adsorption, TG-DTG, EDX, H₂-TPR and CO₂-TPD techniques and tested in the oxidative dehydrogenation of propane in the temperature range 450–600 °C. For all the catalysts the conversion increases with increasing the reaction temperature while the propene selectivity decreases to the benefit of carbon oxides for Ce-based system and of cracking products for the others. The best yields in propene were obtained with Dy- and Sm–Mg–Al–O catalysts. No correlation between the reducibility of the rare-earth cation and the catalytic performances was observed. A linear correlation between the catalyst basicity and the propene selectivity was evidenced.     

Bismuth‐Doped Ceria,Ce0.90Bi0.10O2: A Selective and Stable Catalyst for Clean Hydrogen Combustion

Bismuth‐doped cerias are successfully applied as solid “oxygen reservoirs” in the oxidative dehydrogenation of propane. The lattice oxygen of the ceria is used to selectively combust hydrogen from the dehydrogenation mixture at 550 °C. This process has three key advantages: it shifts the dehydrogenation equilibrium to the desired products side, generates heat, aiding the endothermic dehydrogenation, and simplifies product separation (water vs. hydrogen). Furthermore, the process is safer, since it uses the catalyst’s lattice oxygen instead of gaseous oxygen. We show here that bismuth‐doped cerias are highly active and stable towards hydrogen combustion, and explore four different approaches for optimising their application in the oxidative dehydrogenation of propane: first, the addition of extra hydrogen which lowers hydrocarbon conversion by suppressing both combustion and coking; second, the addition of tin which completely inhibits coking; third, the addition of platinum which increases selectivity, but at the expense of lower activity. The best results are obtained through tuning the reaction temperature. At 400 °C, high activity and selectivity were obtained for the bismuth‐doped ceria Ce_0.90Bi_0.10O₂. Here, 90% of the hydrogen feed is converted at 98% selectivity. This optimal reaction temperature can be rationalised from the hydrogen and propene temperature‐programmed reduction (TPR) profiles: 400 °C lies above the reduction maximum of hydrogen, yet below that of propene. That is, this temperature is sufficiently high to facilitate rapid hydrogen combustion, but low enough to prevent hydrocarbon conversion.