鸟巢状CuCeZrOx三元复合氧化物的合成及其对碳烟颗粒的催化氧化性能研

doi:10.15541/jim20160662

摘要/Abstract

摘要：

采用尿素均相沉淀法合成了CuCeZrO_x(CCZ)三元复合氧化物催化剂。采用X射线衍射分析(XRD)、N₂-吸脱附测试、X射线光电子能谱(XPS)、扫描透射电镜(STEM)、程序升温还原(脱附、氧化)等技术, 考察煅烧温度对催化剂的物化性质和催化碳烟燃烧活性的影响。结果表明: 350℃煅烧产物CCZ-350表现出最优的催化活性: 在空速为12000 mL/(g_catalyst·h), O₂浓度为10vol%, NO浓度为500×10^-6, 催化剂和碳烟以10︰1质量比松散接触条件下, 碳烟颗粒最大燃烧速率温度T₅₀ = 407℃, 同时表现出极佳的抗水汽中毒和抗SO₂中毒性能, 这与活性组分的高度分散以及催化剂表面大量高活性吸附氧物种的存在有关。此外, 催化剂材料具有疏松多孔的鸟巢状结构, 有利于催化剂和碳烟颗粒的充分接触。该催化剂在柴油车尾气排放温度范围内(150~400℃)还能完全催化氧化柴油车尾气中CO、C₃H₆和C₃H₈等其他污染物, 显示出优异的催化净化柴油车尾气的综合性能。

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关键词: 三元复合氧化物催化剂, CuCeZrOx, 碳烟氧化, 抗水抗硫性能

Abstract:

A series of ternary composite oxides CuCeZrO_x calcined at different temperatures were prepared by a homogeneous precipitation method using urea as the precipitant. X-ray diffraction (XRD), N₂ adsorption-desorption analysis, X-ray photoelectron spectroscopy (XPS), scanning transmission electron microscope (STEM), and temperature-programmed reduction (or desorption, oxidation) (TPR, TPD or TPO) measurements were utilized to investigate the influence of calcination temperatures on the physicochemical property and catalysis performance towards soot catalytic oxidation. The CCZ-350 (calcined at 350℃) sample exhibits the optimized catalysis performance: temperature at the maximum rate of soot oxidation (T₅₀) = 407℃, under test conditions of space velocity = 12000 mL/(g_catalyst·h), c(O₂) = 10vol%, c(NO) = 500×10^-6, and mass ratio of (loosely contacted) catalyst/soot = 10/1. It is believed that theabundant high-reactive adsorbed oxygen species on CCZ-350 surface contribute much to its outstanding catalysis performance. Besides, CCZ-350 with a loose-packing and porous morphology favors its sufficient contact with soot, thus further benefiting the catatlytic activity towards soot combustion. More importantly, CCZ-350 also presents good water vapor and SO₂ resistence performance as well as good capability of eliminating other pollutants in diesel exhaust at low temperatures (150-400℃), such as CO, C₃H₆ and C₃H₈.

Key words: ternary composite oxides catalyst, CuCeZrOx, soot oxidation, water vapor and SO₂resistence

中图分类号:

TQ174

赵晗, 周晓霞, 潘琳钰, 陈航榕. 鸟巢状CuCeZrO_x三元复合氧化物的合成及其对碳烟颗粒的催化氧化性能研[J]. 无机材料学报, 2017, 32(9): 923-930.

ZHAO Han, ZHOU Xiao-Xia, PAN Lin-Yu, CHEN Hang-Rong. Birdnest-like CuCeZr Mixed Oxides: Synthesis and Excellent Catalysts for Diesel Exhaust Oxidatio[J]. Journal of Inorganic Materials, 2017, 32(9): 923-930.

图/表 11

图1 不同煅烧温度下所得产物CCZ-x的XRD图谱(x = 300-1000)

Fig. 1 XRD patterns of the different CCZ-x catalysts(x = 300-1000)

表1 不同温度煅烧产物CCZ-x的晶胞参数、比表面积、孔容和孔径(x = 300~1000)

Table 1 Structural properties of different CCZ-x catalysts (x = 300-1000)

Sample	Lattice parameter /nm ^a	S_BET/ (m²·g^-1) ^b	V_BJH/ (cm³·g^-1) ^c	D_p/nm ^c
CCZ-300	5.416	198.0	0.960	33.8
CCZ-350	5.415	186.0	0.900	32.6
CCZ-400	5.420	160.0	0.850	33.6
CCZ-500	5.418	128.0	0.800	32.5
CCZ-600	5.420	110.0	0.700	32.9
CCZ-800	5.415	12.0	0.150	49.0
CCZ-1000	5.389	0.1	0.001	No data

图2 CCZ-x(x=300-1000)催化碳烟氧化过程的(a)碳烟转化率曲线, (b)特征温度T90、T50及CO2选择性随煅烧温度的变化

Fig. 2 Temperature-programmed oxidation of soot catalyzed by different CCZ-x catalysts (x = 300-1000): soot conversion curves (a), and the change in characteristic temperatures (T90 and T50) and selectivity to CO2 () with increasing calcination temperature (b)

图3 CCZ-x (4: x = 300, 3: x = 350, 2: x = 500, 1: x = 800) 的XPS谱图: Ce 3d (a), Cu 2p (b), Zr 3d (c), O 1s (d)

Fig. 3 Ce 3d (a) , Cu 2p (b), Zr 3d (c), and O 1s (d) XPS patterns of CCZ-x (4: x = 300, 3: x = 350, 2: x = 500, 1: x = 800)

表2 不同煅烧温度产物CCZ-x(x = 800, 500, 350, 300)表面化学组分的XPS分析

Table 2 XPS surface analyses of different CCZ-x (x = 800, 500, 350, 300)

Sample	Cu: Ce: Zr ^a	O_ads/(O_ads+O_latt)
CCZ-800	0.17: 0.60: 0.23	0.23
CCZ-500	0.15: 0.65: 0.20	0.46
CCZ-350	0.12: 0.67: 0.21	0.64
CCZ-300	0.12: 0.69: 0.19	0.57

图4 不同煅烧温度产物CCZ-x (x = 300, 350, 500, 800)的H2-TPR 曲线 (括号中的数据为H2-TPR曲线的积分面积)

Fig. 4 H2-TPR profiles of the selected CCZ-x catalysts (x= 300, 350, 500, and 800) Data in the brackets indicate the integrated area of the H2-TPR curves

图5 不同煅烧温度产物CCZ-x (x = 300, 350, 500, 800)的O2-TPD曲线 (括号中的数据为O2-TPD曲线的积分面积)

Fig. 5 O2-TPD profiles of the selected CCZ-x catalysts (x= 300, 350, 500, and 800) Data in the brackets indicate the integrated area of the O2-TPD curves

图6 CCZ-350的STEM (a, b) 图像和元素分布图(c-e)

Fig. 6 Dark-field (a) and bright-field (b) STEM images and elements mapping (c-e) (corresponding to TEM image in b) of CCZ-350 Scale bars: 100 nm

图7 CCZ-350催化碳烟燃烧过程中鸟巢结构“过滤+催化”作用示意图(a), 活性氧物种对碳烟氧化的催化作用机制(b)

Fig. 7 Schematic representation of (a) the role of the “nest structure” of CCZ-350 in soot combustion process, and (b) the soot combustion in NOx/O2 over CCZ-350 catalyst

图 8 CCZ-350催化碳烟燃烧活性的耐水耐硫性测试

Fig. 8 Water vapor and SO2 resistance properties of catalytic activity towards soot oxidation for CCZ-350

图 9 CCZ-350催化氧化CO、C3H6、C3H8测试结果

Fig. 9 Catalytic co-oxidation of CO, C3H6 and C3H8 over CCZ-350

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