Ti-Al复合载体载锰催化剂同时脱硝脱汞实验

doi:10.16085/j.issn.1000-6613.2020-0566

摘要/Abstract

摘要：

采用溶胶-凝胶法制备了一系列TiO₂、TiO₂-Al₂O₃（TiAl）、MnO₂/TiO₂（MnTi）和MnO₂/TiO₂-Al₂O₃（MnTiAl）样品，在固定床实验装置上研究了MnTi和MnTiAl催化剂的脱硝、脱汞性能，并对相应的样品进行了BET、XRD、H₂-TPR、XPS表征分析。表征结果表明，Al₂O₃掺入TiO₂后能极大提高载体的比表面积，提升催化剂氧化还原性能，且有利于高价态锰离子（Mn³⁺和Mn⁴⁺）和化学吸附氧（O*）在催化剂表面富集。固定床实验结果表明，在反应温度范围内，MnTiAl催化剂脱硝、脱汞性能均优于MnTi催化剂，MnTiAl催化剂在200℃时脱硝、脱汞效率分别高达88.5%和96.1%。MnTiAl脱除烟气Hg⁰过程中，将Hg⁰氧化为Hg²⁺的同时，催化剂表面Mn³⁺、Mn⁴⁺和O*浓度均被消耗，同时烟气中的O₂能将催化剂表面较低价态的锰离子（Mn²⁺和Mn³⁺）重新氧化为高价态锰离子（Mn³⁺和Mn⁴⁺），并且能补充催化剂表面的化学吸附氧（O*），进而实现催化剂催化氧化Hg⁰过程。

关键词: 催化剂, 煤燃烧, 选择性催化还原, 汞, 二氧化钛, 三氧化二铝

Abstract:

Sol-gel method was applied to synthesize TiO₂, TiO₂-Al₂O₃ (TiAl), MnO₂/TiO₂ (MnTi), and MnO₂/TiO₂-Al₂O₃(MnTiAl). The simultaneous removal of NO and Hg⁰ from the coal-fired flue gas over MnTi and MnTiAl catalysts were studied on a fixed-bed reactor system, and the corresponding samples were characterized and analyzed by BET, XRD, H₂-TPR, and XPS. The characterization results showed that the introduction of Al₂O₃ into TiO₂ could greatly increase the specific surface area of the support, improve the redox performance of the catalyst, and promote the enrichment of high-valence manganese ions (Mn³⁺ and Mn⁴⁺) and chemisorbed oxygen (O*) on the catalyst surface. The results of the reaction experiments showed that the MnTiAl catalyst exhibited better NO and Hg⁰ removal performance than the MnTi catalyst in the entire reaction temperature range. The efficiencies of denitrification and mercury removal by MnTiAl catalyst at 200℃ were as high as 88.5% and 96.1%, respectively, and the concentration of Mn³⁺, Mn⁴⁺, and O* on the surface of the catalyst were all consumed along with the oxidization of Hg⁰ to Hg²⁺. At the same time, the O₂ in the flue gas could re-oxidize the low-valence manganese ions (Mn²⁺and Mn³⁺) to high-valence manganese ions (Mn³⁺ and Mn⁴⁺), as well as recover and replenish the chemically adsorbed oxygen (O*) species on the surface of the catalyst, thereby realizing the catalytic Hg⁰ oxidation over the MnTiAl catalyst.

Key words: catalyst, coal combustion, selective catylitic reduction (SCR), mercury, titanium dioxide(TiO₂), aluminum oxide(Al₂O₃)

中图分类号:

X511

董璐, 黄亚继, 丁守一, 程好强, 王圣, 段钰锋. Ti-Al复合载体载锰催化剂同时脱硝脱汞实验[J]. 化工进展, 2021, 40(1): 234-241.

Lu DONG, Yaji HUANG, Shouyi DING, Haoqiang CHENG, Sheng WANG, Yufeng DUAN. Experimental on simultaneous NO and mercury removal over manganese modified Ti-Al composite catalyst[J]. Chemical Industry and Engineering Progress, 2021, 40(1): 234-241.

图/表 9

图1 模拟烟气固定床脱硝、脱汞实验装置

表1 样品的比表面积分析

样品	比表面积/m²·g^-1	比孔容/cm³·g^-1	孔径/mm
TiO₂	67.72	0.196	6.35
TiAl	135.83	0.322	4.16
MnTi	69.42	0.212	7.23
MnTiAl	141.22	0.335	4.21

图2 样品的XRD谱图

图3 MnTi和MnTiAl催化剂的H2-TPR分析

图4 MnTi和MnTiAl催化剂表面Mn 2p和O 1s XPS谱图

表2 催化剂表面原子物质的量分数 (%)

催化剂	O 1s		Mn 2p
催化剂	O_L/O^T	O*/O^T	Mn²⁺/Mn^T	Mn³⁺/Mn^T	Mn⁴⁺/Mn^T
新鲜MnTi	42.6	53.3	41.2	34.5	24.3
新鲜MnTiAl	24.5	69.4	19.6	38.6	41.8
反应后MnTiAl	44.8	53.2	42.7	30.7	26.6

图5 MnTi和MnTiAl催化剂的脱硝和脱汞效率（脱硝反应工况：N2+5% O2+0.03% NO+0.03% NH3；脱汞反应工况：N2+5% O2）

图6 反应后的MnTiAl催化剂表面Mn 2p和O 1s XPS谱图(反应工况：N2+5% O2，150℃)

图7 新鲜MnTiAl催化剂和反应后的MnTiAl催化剂表面Hg 4f XPS谱图(反应工况：N2+5% O2，150℃)

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