催化学报

催化学报 ›› 2020, Vol. 41 ›› Issue (2): 276-285.DOI: 10.1016/S1872-2067(19)63444-3

• 论文 • 上一篇    下一篇

SiBeta负载的VOx催化剂在丙烷直接脱氢制丙烯中的活性位

陈冲a,b, 孙明磊a, 胡忠攀a, 刘玉萍b, 张守民b, 袁忠勇a,b   

  1. a 南开大学材料科学与工程学院, 国家新材料研究院, 天津 300350;
    b 南开大学化学学院, 先进能源材料化学教育部重点实验室, 天津化学化工协同创新中心, 天津 300071
  • 收稿日期:2019-05-26 修回日期:2019-07-09 出版日期:2020-02-18 发布日期:2019-11-04
  • 通讯作者: 袁忠勇
  • 基金资助:
    国家自然科学基金（21421001，21573115）；111计划（B12015）；煤炭高效利用与绿色化工国家重点实验室基金（2017-K13）.

Nature of active phase of VOx catalysts supported on SiBeta for direct dehydrogenation of propane to propylene

Chong Chena,b, Minglei Suna, Zhongpan Hua, Yuping Liub, Shoumin Zhangb, Zhong-Yong Yuana,b   

  1. a National Institute for Advanced Materials, School of Materials Science and Engineering, Nankai University, Tianjin 300350, China;
    b Key Laboratory of Advanced Energy Materials Chemistry (Ministry of Education), Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), College of Chemistry, Nankai University, Tianjin 300071, China
  • Received:2019-05-26 Revised:2019-07-09 Online:2020-02-18 Published:2019-11-04
  • Supported by:
    This work was supported by the National Natural Science Foundation of China (21421001, 21573115), the 111 project (B12015), and the Foundation of State Key Laboratory of High-efficiency Utilization of Coal and Green Chemical Engineering (2017-K13).

PDF

419

摘要： 丙烯是一种非常重要的化工基础原料，主要用来生产高价值的化学品，如丙烯腈，异丙醇和甘油等.丙烯的传统来源主要是石油的催化裂化反应，以及石脑油和轻柴油的裂解过程.随着石油资源的减少，丙烷直接脱氢制丙烯技术逐渐成为一条重要的丙烯生产渠道.V基催化剂在丙烷氧化脱氢反应中被广泛研究，但被用于丙烷直接脱氢反应的报道还较少，且V基催化剂在丙烷直接脱氢制丙烯中的活性位目前还没有统一定论，可能是由于V的活性物种与载体性质密切相关，因此研究V基催化剂在不同载体上的活性位具有重要意义.Beta沸石分子筛具有规则微孔结构，高的比表面积以及可调节的酸性，是一种理想的金属催化剂载体.本文采用脱铝后的Beta分子筛作为V催化剂载体，通过调节V的负载量探究丙烷直接脱氢活性和VOx结构的关系，以及催化剂的酸性对性能的影响.
活性测试结果显示，V负载量分别为3 wt%，7 wt%和10 wt%时（催化剂分别命名为3VSiBeta，7VSiBeta和10VSiBeta），三者的催化活性十分接近，此外，这些催化剂还具有较好的循环利用性，但碳沉积，丙烯选择性以及失活率都是随着V负载量的升高而增加.XRD和N2吸附结果揭示，VOx在SiBeta上呈高度分散状态，并且当V负载量从3 wt%升至10 wt%时，表面V密度发生明显变化，VOx物种在3VSiBeta中可基本实现孤立的单分散状态.同时，DR UV-vis，H2-TPR以及Raman测试结果表明，VOx物种的聚合程度随V负载量的升高逐渐增加.NH3-TPD结果表明，Beta载体在脱铝后本身的酸性位完全消除，但是负载V后引入了新的酸性位，并且3VSiBeta，7VSiBeta和10VSiBeta三者的酸量基本相当.尽管XPS结果显示，不同VSiBeta催化剂上的V价态分布有差异，但是相似的催化活性说明VSiBeta催化剂的活性位与形成的酸性位数目密切相关，而受V初始价态的影响不大.本文指出，酸性位可能是与V-O-Si键直接相关，V负载量从3 wt%增加到10 wt%，会逐渐形成无催化活性的V-O-V键，导致活性不能进一步提升.因此，3VSiBeta催化剂中可实现孤立的VOx物种单层分散在SiBeta载体上，形成了大量的酸性V-O-Si键，从而显示出和高负载量的VSiBeta催化剂相当的活性以及较高的脱氢稳定性.

关键词: 丙烷脱氢, 丙烯, VOx物种, SiBeta载体, 活性位

Abstract: The VOx catalysts supported on dealuminated Beta zeolite (SiBeta) with varying V loadings (from 0.5 to 10 wt%) are prepared and tested for their catalytic activities in the reaction of direct dehydrogenation of propane to propylene (PDH). It is characterized that the VSiBeta catalysts possess different kinds of vanadium species on the SiBeta support, including monomeric or isolated VOx species at a low V loading, and polynuclear VOx species in different polymerization degrees at higher V loadings. The 3VSiBeta catalyst (V loading is 3 wt%), containing isolated VOx species in monolayer, shows around 40% of propane conversion with 90% of propylene selectivity (reaction conditions:600 ℃, 4000 mL g-1 h-1) which are comparable to VSiBeta catalysts with higher V loadings. The catalytic activity exhibits a good linear relationship with the amount of generated acidic sites, which are derived from the interaction sites between VOx species and SiBeta support, and keeps stable after several regeneration cycles. Thus, as the VOx species directly contact with SiBeta support via V-O-Si bonds, a reactivity enhancement can be achieved. While, the initial valence state of V does not seem to influence the catalytic performance. Moreover, the aggregation degree of VOx species determines the propylene selectivity and deactivation rate, both of which increase as raising the V loading amount.

Key words: Propane dehydrogenation, Propylene, VOx species, SiBeta support, Active sites