催化学报

催化学报 ›› 2016, Vol. 37 ›› Issue (6): 878-887.DOI: 10.1016/S1872-2067(15)61041-5

• 论文 • 上一篇    下一篇

一种新型高比表面积TiO2载体在NH3选择性催化还原反应中对V2O5分散性的促进作用

刘欣a, 李俊华a, 李想a, 彭悦a, 王虎b, 江晓明b, 王兰武c   

  1. a 清华大学环境学院环境模拟与污染控制国家重点联合实验室, 北京 100084;
    b 大唐南京环保科技有限责任公司, 江苏南京 211111;
    c 四川华铁钒钛科技股份有限公司, 四川攀枝花 617200
  • 收稿日期:2015-12-05 修回日期:2016-01-10 出版日期:2016-05-30 发布日期:2016-05-30
  • 通讯作者: Junhua Li
  • 基金资助:

    国家自然科学基金(21325731, 21221004); 国家高技术研究发展计划(863 计划, 2013AA065304); 国家环境保护大气复合污染来源与控制重点实验室.

NH3 selective catalytic reduction of NO: A large surface TiO2 support and its promotion of V2O5 dispersion on the prepared catalyst

Xin Liua, Junhua Lia, Xiang Lia, Yue Penga, Hu Wangb, Xiaoming Jiangb, Lanwu Wangc   

  1. a State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing 100084, China;
    b Datang Nanjing Environmental Protection Technology Co., Ltd., Nanjing 211111, Jiangsu, China;
    c Huatie Vanadium and Titanium Technology Co., Ltd. Panzhihua 617200, Sichuan, China
  • Received:2015-12-05 Revised:2016-01-10 Online:2016-05-30 Published:2016-05-30
  • Contact: Junhua Li
  • Supported by:

    This work was supported by the National Natural Science Foundation of China (21325731, 21221004), the National High Technology Research and Development Program of China (863 Program), and the State Environmental Protection Key Laboratory of Sources and Control of Air Pollution Complex.

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摘要：

燃煤电厂及工业窑炉的氮氧化物减排是改善空气质量的关键. 现阶段选择性催化还原氮氧化物是最有效的技术途径, 核心是采用以 TiO2 为载体的钒基催化剂净化烟气. 催化剂的活性是决定烟气净化效率的重要因素. 近些年的研究主要集中在活性组分的替换上, 但是由于其成本高昂, 抗水抗硫性能较差, 在实际中使用的效果不佳. 本文从载体入手, 制备了新型 TiO2 载体, 并采用特殊制备手段研发了新型高比表面积钒钛体系催化剂. 通过对载体和催化剂的物化表征, 研究了高比表面积 TiO2 载体对于活性组分钒在表面分散的促进作用, 及分散性的提高对氧化性和酸性的影响. 所制新型 TiO2 载体比表面积达到 380.5 m2/g, 较商业化 TiO2 载体提高了 5 倍. 以此为载体, 采用超声浸渍法和分段烧结的热处理方式, 制备了钒负载量为 5 wt% 的新型钒钛催化剂. 结果发现, 高比表面载体显著提高了钒基催化剂比表面积为 117.7 m2/g, 比传统钒钛催化剂提高了 38%. 计算结果表明, 这种方式还提高了钒物种在载体表面的分散性. XRF 结果表明, 超声浸渍法和普通浸渍法均可将 5 wt% 的钒成功地负载到了载体上. 通过模拟实际烟气成分对催化剂的脱硝效果进行了测试, 结果表明, 所制催化剂具备更宽的温度窗口及更好的 N2 选择性, NOx 转化率在 200-450 ℃ 时能保持在 80% 以上, 比传统方法制备的催化剂温度窗口宽 100 ℃. 且 N2 选择性在 400 ℃ 以上时也明显更高. 对两种催化剂样品的抗水抗硫能力进行了考察, 发现在烟气中存在 H2O 或 SO2 时, 高比表面积催化剂样品相较传统方法制备的催化剂具有更高的活性. Raman 结果发现, 在传统商业载体上钒物种由于分散不充分, 更易在烧结过程中形成 V-O-V 物种, 从而降低了催化剂的氧化还原性. 而新型催化剂表面的 V-O-Ti 及 V=O 物种数量更多, 这些物种活性更高, 从而使得催化剂在低温下具有更高的 NOx 转化率. 采用 NH3-TPD, H2-TPR 和 XPS 技术研究了活性提高与催化剂结构的关系. 结果发现, 高比表面积载体通过对钒物种的分散作用, 在载体表面由于二氧化钛载体的孔结构和钒物种的高活性, 也使得该催化剂具有较高的酸量和氧化还原性. 本文为制备新型烟气脱硝催化剂提供了理论依据, 该技术方法具有较高的应用价值.

关键词: 钒钛体系催化剂, 脱硝, 二氧化钛, 比表面积, 分散性

Abstract:

A titania support with a large surface area was developed, which has a BET surface area of 380.5 m2/g, four times that of a traditional titania support. The support was ultrasonically impregnated with 5 wt% vanadia. A special heat treatment was used in the calcination to maintain the large surface area and high dispersion of vanadium species. This catalyst was compared to a common V2O5-TiO2 catalyst with the same vanadia loading prepared by a traditional method. The new catalyst has a surface area of 117.7 m2/g, which was 38% higher than the traditional V2O5-TiO2 catalyst. The selective catalytic reduction (SCR) performance demonstrated that the new catalyst had a wider temperature window and better N2 selectivity compared to the traditional one. The NO conversion was >80% from 200 to 450 ℃. The temperature window was 100 ℃ wider than the traditional catalyst. Raman spectra indicated that the vanadium species formed more V-O-V linkages on the catalyst prepared by the traditional method. The amount of V-O-Ti and V=O was larger for the new catalyst. Temperature programmed desorption of NH3, temperature programmed reduction by H2 and X-ray photoelectron spectroscopy results showed that its redox ability and total acidity were enhanced. The results are helpful for developing a more efficient SCR catalyst for the removal of NOx in flue gases.

Key words: V2O5-TiO2 catalyst, Denitrification, Titania, Surface area, Dispersibility