摘要
丙烷脱氢(PDH)是一种高效的丙烯生产工艺.近年来随着页岩气产量的增加,PDH逐渐成为替代石油催化裂化增产丙烯的重要方法之一.Pt基双金属催化剂在催化PDH领域被广泛研究.其中,PtZn合金双金属催化剂因较好的催化活性和较强的经济可行性,被认为是PDH反应的理想催化剂之一.PtZn合金主要有Pt_(1)Zn_(1),PtZn1.7和Pt3Zn等,其中Pt_(1)Zn_(1)催化PDH反应的活性最好.采用传统共浸渍法制备的PtZn双金属催化剂的金属物种容易分布不均匀,并且成分组成复杂,可能会有多种PtZn合金以及金属单质生成,因此催化活性不理想.如何制备高分散的Pt_(1)Zn_(1)合金催化剂对于PDH工艺的发展有着重要的意义.本文报道了一种分子筛脱金属-还原诱导的策略,将高分散的PtZn合金纳米颗粒负载到Beta沸石上用于PDH反应.首先,在乙二胺的辅助下通过一步水热法合成了杂原子分子筛Zn@Beta.X射线衍射、高分辨透射电镜和紫外-可见光(UV-vis)光谱等结果证明Zn@Beta被成功合成,并且Zn主要以单分散的骨架Zn物种存在.随后,通过简单的浸渍法负载金属Pt.UV-vis光谱、X射线光电子能谱(XPS)、傅里叶变换红外光谱和氢气程序升温还原等结果表明,在浸渍的过程中骨架Zn物种从分子筛骨架移出,并与游离的Pt物种产生了强相互作用.再经H2还原最终得到催化剂0.3Pt1Zn@Beta (Pt和Zn的负载量分别为0.3 wt%和1 wt%).XPS、同步辐射吸收谱和球差矫正电镜结果表明,0.3Pt1Zn@Beta形成了以Pt_(1)Zn_(1)合金物种为主的金属纳米颗粒,而通过共浸渍法制备的PtZn双金属催化剂0.3Pt1Zn/Beta中除了Pt_(1)Zn_(1)合金以外,还有大量的金属Pt单质生成.PDH催化性能评价结果表明,与0.3Pt1Zn/Beta和单金属催化剂0.3Pt/Beta相比,0.3Pt1Zn@Beta表现出更好的PDH催化活性和稳定性.550°C反应时,0.3Pt1Zn@Beta催化生成丙烯的速率为128 mmol/gcat./h,而0.3Pt1Zn/Beta和0.3Pt/Beta催化生成丙烯的仅�
Developing efficient bimetallic Pt-based catalyst is highly desired for propane dehydrogenation(PDH) process.Typical co-impregnation method often results in inhomogeneous distributions of metal species on supports.Herein,we reported a facile method to support Pt Zn bimetal alloy nanoparticles onto Beta zeolite,mainly existing as highly dispersed Pt_1Zn_(1) alloy species.Zn@Beta was first synthesized by hydrothermal method with the aid of ethylenediamine(EDA),leading to the introduction of Zn atoms into zeolite lattice.An impregnation process was subsequently employed to support Pt species.During this process,skeleton Zn atoms migrated out of the framework and were then reduced together with Pt in flowing H_2,leading to the formation of Pt Zn alloy with mainly Pt_1Zn_(1) structures.Cs-corrected high-angle annular dark-field scanning transmission election microscope and X-ray absorption fine structure analyses revealed that this method was more conducive to the formation of Pt Zn alloy compared with the co-impregnation method.The obtained catalyst of 0.3Pt1Zn@Beta exhibited initial propane conversion of 36.8% and propylene selectivity of 99.3% combined with low deactivation rate(0.004 h^(–1)) over 24 h with propane WHSV of 4.7 h^(–1) at 550 °C.The catalyst also exhibited good PDH performance in a long-term reaction(180 h) and robustness during regeneration reactions by simply flushing hydrogen.
作者
张龙康
马跃
刘昌呈
万志鹏
翟承伟
王新
徐浩
关业军
吴鹏
Longkang Zhang;Yue Ma;Changcheng Liu;Zhipeng Wan;Chengwei Zhai;Xin Wang;Hao Xu;Yejun Guan;Peng Wu(Shanghai Key Laboratory of Green Chemistry and Chemical Processes,School of Chemistry and Molecular Engineering,East China Normal University,Shanghai 200062,China;State Key Laboratory of Petroleum Molecular and Process Engineering(SKLPMPE),Sinopec Research Institute of Petroleum Processing Co.,LTD.,Beijing 100083,China;SINOPEC Research Institute of Petroleum Processing Co.,Ltd.,Beijing 100083,China)
基金
国家重点研发计划(2021YFA1501401)
国家自然科学基金(22222201,21972044).
