钒基催化剂上丙烷氧化脱氢制丙烯研究进展:从有氧到无氧

与已经工业化的丙烷直接脱氢制丙烯技术相比,丙烷氧化脱氢制丙烯因其放热反应的特点,可以在较低的温度下完成反应从而降低了能耗,且氧气的存在抑制了催化剂的积炭等优点而备受关注。然而,在过去三十年的研究历程里,丙烯的低选择性和低收率始终是该技术工业化面临的主要问题。本文从钒基催化剂上丙烷氧化脱氢的反应机理入手,对比了有氧和无氧条件下的丙烷氧化脱氢反应,分析了氧气的存在对丙烯选择性造成的不利影响,介绍了近几年所采用的提高丙烯选择性和收率的新的工艺方法,简述了颇具工业化前景的流化床反应器和膜反应器在丙烷氧化脱氢反应中的应用。氧气的存在是造成丙烯选择性低的重要原因,实现无氧条件下的丙烷氧化脱氢反应过程和催化剂的循环再生过程同时进行有望成为新的研究趋势。     

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。     

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。     

丙烷催化脱氢制丙烯技术研究进展

丙烯是一种重要的有机化工原料和石油化工原料中间体。由于能源结构的改变,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、经济环保等优势,成为当前丙烯生产工艺研究的焦点。本文列举了几种常用的丙烷直接脱氢制丙烯的工艺,对技术方法进行了对比,并对催化剂进行了简述。在此基础上,对丙烷催化脱氢新技术以及催化剂发展前景进行了展望。     

丙烷脱氢制丙烯技术研究

介绍了几种丙烷脱氢制丙烯技术：催化脱氢、氧化脱氢、膜反应器脱氢。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虽已实现了工业化，但其催化剂的性能需进一步提高；综述了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，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。     

碳基硼基催化体系丙烷氧化脱氢催化剂的研究进展

以碳基硼基为代表的非金属催化剂氧化能力不如金属氧化物,这使得非金属催化体系如碳基和硼基催化剂对于丙烷氧化脱氢反应具有独特的优势。本文综述了应用廉价环保型改性碳基和硼基的非金属丙烷脱氢催化剂将丙烷转化为丙烯的技术前沿,阐述了有序介孔炭材料,纳米碳材料（纳米纤维、石墨烯、碳纳米金刚石等）和六方氮化硼材料各自的丙烷氧化脱氢机理以及通过杂原子改性后提高其催化活性的情况。并对其未来的发展方向以及丙烷氧化脱氢新材料领域的发展做了展望。     

丙烷CO_2氧化脱氢制丙烯研究进展

丙烷氧化脱氢反应不受热力学平衡限制,焓变小于零,为放热反应,可节省能源。但氧化脱氢制丙烯因为有O2存在,导致丙烷和丙烯深度氧化,使丙烯选择性下降。可通过以下途径改进:(1)通过添加助剂或改变活性组分限制丙烯的深度氧化;(2)改变反应气氛,用氧化性较弱的氧化剂(如CO2和N2O等)代替O2。近年来,在低碳烷烃脱氢领域以CO2为氧化剂的研究较多,CO2可以避免深度氧化。综述在丙烷氧化脱氢反应中通过引入CO2,将丙烷直接脱氢反应与逆水煤气反应进行偶合,打破了丙烷直接脱氢反应平衡,消除积炭,提高催化剂稳定性,推动反应向生成丙烯的方向进行,丙烯收率提高;在低温(270℃)区域,副反应可提高丙烷CO2氧化脱氢反应的丙烯平衡收率,丙烷二氧化碳脱氢反应的催化剂体系主要包括铬系催化剂、镓系催化剂、钒系催化剂及其他催化剂。     

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。     

丙烷脱氢工艺对比

丙烷脱氢制丙烯的工艺主要有催化脱氢、氧化脱氢和无机膜催化脱氢三大类,详细对比丙烷催化脱氢技术中Oleflex工艺、Catofin工艺、FBD工艺、STAR工艺、Linde工艺的反应机理、工艺流程、催化剂、工艺特点、操作条件等内容,指出丙烷催化脱氢工艺具有良好的工业应用前景,未来需重点加强丙烷脱氢催化剂的研究开发工作,进一步优化工艺流程,提升整体经济性。     

丙烷脱氢制丙烯催化剂研究进展

丙烷作为天然气和页岩气等的重要成分,其高效催化转化不仅具有重要的理论研究意义,而且具有广阔的应用前景。丙烷直接脱氢制丙烯已成为增产丙烯的有效手段。对丙烷脱氢反应的铂基催化剂、铬基催化剂、碳基催化剂以及钒基催化剂进行综述,重点介绍载体及助剂对铂基及铬基催化剂活性和稳定性的影响,并提出目前丙烷脱氢反应催化剂研究的关键问题,对其发展前景进行展望。     

The selective oxidative dehydrogenation of propane on vanadium aluminophosphate catalysts

VAPO-5 and V/ ALPO-5 catalysts have been tested for the oxidative dehydrogenation of propane. Depending on the vanadium contents and the preparation procedure, different vanadium species and different catalytic behavior are observed. The catalyst containing V⁵⁺ species with a tetrahedral coordination presents the higher yield of propene in the oxidative dehydrogenation of propane. The same yields of CO₂ are observed on all vanadium aluminophosphate catalysts, while the higher the yield of propene the lower the yield of CO is.     

Influence of the different dechlorination time on catalytic performances of PtSnNa/ZSM-5 catalyst for propane dehydrogenation

Catalytic dehydrogenation of propane has recently received considerable attention because of the increasing demand for propene. Among several catalysts, PtSnNa/ZSM-5 catalyst is one of the most suitable ones. In this study, PtSnNa/ZSM-5 catalysts with different content of chlorine were prepared by changing the time of catalyst dechlorination. The obtained catalysts were characterized by X-ray fluorescence (XRF), XRD, nitrogen adsorption, ²⁷Al MAS NMR, NH₃-TPD, H₂ chemisorption and TPR. It was found that with the increase of treatment time, more framework aluminum atoms were removed from tetrahedral positions, leading to the loss of Sn species and the decrease of catalyst acidity. Meantime, the porous properties and the interactions between Pt and Sn of the catalysts changed remarkably, which was disadvantageous to the reaction. Compared with the dechlorinated catalysts, the fresh sample with suitable content of chlorine exhibited the best reaction activity and stability. The average yield of propene was about 30.4% over 45 h for the reaction of propane dehydrogenation at 590 °C. Finally, a model was proposed for the influence of dechlorinated treatment on catalytic properties of PtSnNa/ZSM-5 catalyst for propane dehydrogenation.     

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.     

Kinetic parameter estimation for supported vanadium oxide catalysts for propane ODH reaction: Effect of loading and support

Kinetic parameters are estimated for a sequential Mars van Krevelan (MVK) reaction model occurring over several supported vanadium oxide (vanadia) catalysts involved in the propane oxidative dehydrogenation (ODH) reaction. The estimated kinetic parameters, pre-exponential factors and activation energies, are used to understand the effect of vanadia loading and oxide support. The pre-exponential factors and vanadia normalized pre-exponential factors vary with vanadia loading and oxide support. The monotonic increase in normalized pre-exponential factors with vanadia loading and the variation of pre-exponential factors with oxide support appears to be related to the change in acidity/basicity of the catalyst and the redox nature of the catalyst, respectively. The activation energy for propene degradation does not significantly change with catalyst; however, the activation energy for propane oxidation is different for the V₂O₅/Al₂O₃ catalyst. It appears that two important considerations are required for the development of an efficient propane ODH catalyst: a high rate constant associated with the propane oxidation reaction, and a high ratio of the rate constant for propene formation to degradation reaction. Based on the observations in the present study it is proposed that a higher TiO₂ support surface area will assist in increasing the propane oxidation activity and propene yield.     

硼基催化剂丙烷氧化脱氢制丙烯

自2016年Hermans课题组发现六方氮化硼（h-BN）在丙烷氧化脱氢制丙烯（ODHP）反应中优异的烯烃选择性,各类硼基材料引起了研究者强烈的研究兴趣并广泛地用于ODHP反应。与传统金属与金属氧化物基催化剂不同,非金属硼基催化体系能够有效抑制CO _x 等过度氧化产物,提高烯烃产率,具有较广阔的工业应用前景。本综述对硼基丙烷氧化脱氢催化剂从催化剂的设计、合成策略和反应性能等方面进行了系统地讨论,阐明了催化剂的构效关系;总结了反应路线、关键中间体、决速步以及催化动力学行为,加深了硼基催化剂催化丙烷氧化脱氢活性位点和机理的理解。指出三配位B—O/B—OH活性位点的有效构建及实现表面与气相自由基反应的协同催化是提高硼基催化剂丙烷脱氢性能的关键。基于目前的研究现状和存在的问题,对硼基催化剂体系研发前景和未来工业化应用进行了展望。     

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.     

Effect of alkali metals additives to V2O5/TiO2 catalyst on physicochemical properties and catalytic performance in oxidative dehydrogenation of propane

The effect of alkali metal additives Li, K, and Rb to V₂O₅/TiO₂ catalyst on the rate of catalyst reduction with propane and reoxidation with oxygen, sorption of propene, and the electron work function has been examined. The results have been correlated with the catalytic performance in oxidative dehydrogenation, ODH, of propane. It has been found that the rates of reduction, reoxidation and the ODH of propane decrease in the order: VTi>LiVTi>KVTi>RbVTi. The activation energies of the reduction and reoxidation are not, however, affected by the presence of the alkali metals. The same sequence has been observed for the work function values of the catalysts. It is argued that alkali metal poisons the centres of the hydrocarbon activation. The yield and selectivity to propene in the ODH of propane increase, however, for the promoted catalysts, following the above sequence. This effect is ascribed to the decrease in the heat of the propene adsorption, which is due to the increase in the basicity and decrease in acidity on the promoted catalysts.