Study on the structure-reactivity correlation of SO42-/ZrO2-Al2O3 in n-butane isomerization reaction
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摘要: 采用“沉淀-浸渍”法制备一系列不同硫酸负载量的SO42-/ZrO2-Al2O3催化剂，利用N2吸附-脱附、Py-FTIR、XRD等手段对催化剂进行表征。在常压、200 ℃、H2：C4=2：3和质量空速为3 h-1的反应条件下，在固定床微型反应评价装置上考察了硫酸负载量对SO42-/ZrO2-Al2O3催化正丁烷异构化反应性能的影响。Py-FTIR结果表明，硫酸化处理为催化剂表面提供了丰富的Brønsted酸性位，其中，强Brønsted酸性位在正丁烷异构化反应中起重要作用，因此，硫酸化处理可显著提高正丁烷异构化活性，而Lewis酸性位与之没有直接关系。
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关键词:
- SO42-/ZrO2-Al2O3 /
- 酸性位 /
- 正丁烷 /
- 异构化
Abstract: A series of alumina-promoted sulfated zirconia catalysts were prepared by precipitation-impregnation method. The catalysts were characterized by N2 sorption, pyridine adsorption Fourier transform infrared spectroscopy (Py-FTIR), X-ray diffraction (XRD). Their catalytic performance in n-butane isomerization was evaluated in a continuous flow type fixed-bed micro-reactor at atmospheric pressure, 200℃, and H2:C4=2:3, with a weight hourly space velocity of n-butane (WHSV) of 3 h-1. The structure-reactivity relationship between surface acidity and catalytic behavior was revealed. Py-FTIR indicates that the sulfated treatment enhances the strength and density of catalytic Brønsted acid sites, which are essential for n-butane isomerization. Therefore, sulfated treatment can significantly improve the activity of n-butane isomerization, and Lewis acidity has no direct effect on it.-
Key words:
- SO42-/ZrO2-Al2O3 /
- acidity /
- n-butane /
- isomerization
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图 1 不同硫酸负载量催化剂的XRD谱图
◆: tetragonal ZrO2; ●: monoclinic ZrO2
Figure 1 XRD patterns of different samples
图 2 不同硫酸负载量催化剂的吡啶吸附红外光谱谱图
Figure 2 Py-FTIR spectra of adsorbed pyridine on different samples
图 3 不同硫酸负载量的催化剂正丁烷异构化反应性能
Figure 3 Catalytic performances of n-butane isomerization over different samples
(reation conditions: t=200 ℃, p=1.01×105 Pa, H2:C4=2:3)
图 4 催化剂表面Brønsted和Lewis酸性位数目与正丁烷转化率的关系
Figure 4 Relationship between the conversion of n-butane and the number of Brønsted or Lewis acid sites
图 5 不同温度处理后催化剂的吡啶吸附红外光谱谱图
Figure 5 Py-FTIR spectra of samples treated at different temperatures
图 6 ZrO2表面羟基分布及Brønsted和Lewis酸性位相互转化示意图
Figure 6 Distribution of hydroxyl on the surface of ZrO2 and the mutual transformation between Brønsted and Lewis acidity
图 7 硫酸化氧化锆表面硫酸物种、Brønsted和Lewis酸性位结构模型
Figure 7 Structural model of sulfate species, Brønsted and Lewis acid on the surface of SO42-/ZrO2-Al2O3
表 1 不同硫酸负载量的催化剂结构特性
Table 1 Textural properties of samples
表 2 不同硫酸负载量催化剂的表面实际硫含量
Table 2 Actual sulfur content of different samples
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