【作者】 杨军；

【导师】 白鹏；

【作者基本信息】 中国石油大学(华东) ， 化学工程与技术， 2023， 硕士

【摘要】 丙烯作为高端化工和新材料的重要原料其需求量日益增长,利用载氧体选择性燃烧丙烷脱氢产生的氢气,实现化学链氧化脱氢（CL-ODH）过程进而打破热力学平衡,获得更高的丙烯收率成为了研究热点。Fe₂O₃由于其载氧量高、环境友好和价格低廉等显著优势成为了CL-ODH过程的理想载氧体,但是Fe₂O₃的氧化还原能力与丙烷脱氢催化剂使用条件不匹配,氧化态和还原态铁物种会与C3组分反应降低丙烯收率并且机械强度低,在使用中存在损耗。因此需要通过改性Fe₂O₃对其氧化还原性能和机械强度进行精确调控,从而与丙烷脱氢催化剂耦合实现丙烷CL-ODH。本课题利用钨酸钠改性实现了Fe₂O₃氧化还原能力的精确调控。实现了Fe₂O₃还原温度在400-600^oC范围内的调控。利用XRD、FT-IR、UV-Vis、XPS、TEM和密度泛函理论（DFT）计算对改性Fe₂O₃的氧化还原性能调控原因进行了分析,并对钠和钨改性剂在氧化还原性能调控中发挥的作用进行了系统的研究,同时通过SEM和EDS对Fe₂O₃改性前后的形貌以及改性剂的含量和分布进行了细致的研究。研究表明钠存在于Fe₂O₃表面并促进钨进入Fe₂O₃内部进而改变Fe₂O₃的表面吸附活性氧物种的占比、Fe³⁺占比、氧空位形成能和Fe-O键的键能,从而实现钠和钨对Fe₂O₃氧化还原性能的协同调控。同时改性剂大幅提高了Fe₂O₃的机械强度,达到了136 N/颗,这有望解决载氧体跑损的问题。通过H₂-TPR、反应器内的还原和脱氢反应以及TG-MS评价了改性前后Fe₂O₃的氧化还原性能和氢气选择性燃烧性能。实验结果显示改性Fe₂O₃的氧化还原性能可以匹配丙烷脱氢催化剂的使用条件。由于改性Fe₂O₃表面的钠物种增加了烃类组分在Fe₂O₃和Fe表面的吸附能,抑制了C3组分与氧化态和还原态的铁物种反应,实现氢气选择性燃烧。在丙烷化学链氧化脱氢反应中,载氧体将丙烷转化率提高了近5%。本研究为化学链氧化脱氢载氧体的设计提供了新的思路和方法,为改性剂对载氧体的氧化还原性能调控提供了新策略。改性Fe₂O₃载氧体具有工业应用前景,本课题研究结果为丙烷CL-ODH迈向工业化提供了理论基础和技术支撑。更多还原

【Abstract】 As an important raw material for high-end chemicals and new materials,the demand for propylene is ever-growing.It has become a research highlight to use oxygen carrier to selectively combust the hydrogen generated by propane dehydrogenation to realize its chemical looping oxidative dehydrogenation（CL-ODH）process and then break the thermodynamic balance to obtain higher propylene yield.Fe₂O₃ has become an ideal oxygen carrier for CL-ODH process due to its significant advantages of high oxygen content,environmental friendliness and low price.However,the redox property of Fe₂O₃ does not match the service conditions of propane dehydrogenation catalyst and exists deep oxidation of hydrocarbons,and there is loss in use due to its poor mechanical strength.Therefore,it is necessary to accurately control its redox property and mechanical strength through modifying Fe₂O₃ to realize propane CL-ODH by coupling with propane dehydrogenation catalyst.This topic uses sodium tungstate modification to achieve precise regulation of the redox property of Fe₂O₃ and realized the regulation of Fe₂O₃ reduction temperature within the range of 400-600^oC.The reasons for the regulation of the redox property of modified Fe₂O₃ were analyzed by using the XRD,FT-IR,UV-Vis,XPS,TEM and Density functional theory（DFT）calculation,and the role of sodium and tungsten modifiers in the regulation of redox property was systematically studied.Meanwhile,the morphology before and after the modification of Fe₂O₃,as well as the content and distribution of modifiers were carefully studied by SEM and EDS..It is indicated that sodium exists on the surface of Fe₂O₃ and promotes the entry of tungsten into the interior of Fe₂O₃,thereby changing the proportion of active oxygen species adsorbed on the surface of Fe₂O₃,the proportion of Fe³⁺,the formation energy of oxygen vacancies and the bonding energy of Fe-O bonds,thereby achieving synergistic regulation of sodium and tungsten on Fe₂O₃ redox property.Meanwhile,the modifier significantly improved the mechanical strength of Fe₂O₃,reaching 136 N/particle,which is expected to solve the problem of oxygen carrier loss.The redox property and selective hydrogen combustion performance of Fe₂O₃ before and after modification were evaluated by H₂-TPR,reduction and dehydrogenation experiment in reactor and TG-MS The experimental results show that the redox property of modified Fe₂O₃can match the conditions of use of propane dehydrogenation catalyst.Sodium species on the surface of modified Fe₂O₃ increased the adsorption energy of hydrocarbon components on Fe₂O₃ and Fe surfaces,which inhibits the reaction of C3 components with oxidized and reduced iron species,achieving selective combustion of hydrogen.In the chemical looping oxidative dehydrogenation reaction of propane,the oxygen carrier increases the conversion of propane by nearly 5%.This study provides new ideas and methods for the design of chemical looping oxidative dehydrogenation oxygen carriers,and provides a new strategy for modifying the redox property of oxygen carriers.The modified Fe₂O₃ oxygen carriers have the potentiality of industrial application.This research topic has provided theoretical basis and technical support for propane CL-ODH towards industrialize.更多还原