Staining of Fluid-Catalytic-Cracking Catalysts: Localising Bronsted Acidity within a Single Catalyst Particle
Staining of Fluid-Catalytic-Cracking Catalysts: Localising Bronsted Acidity within a Single Catalyst Particle
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DOI：
10.1002/chem.201102949
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发表时间：
2012-01-01
影响因子：
4.3
通讯作者：
Weckhuysen, Bert M.
中科院分区：
文献类型：
--
作者：
Buurmans, Inge L. C.;Ruiz-Martinez, Javier;Weckhuysen, Bert M.
采用时间分辨原位显微光谱技术，以酸催化苯乙烯齐聚反应为探针反应，在单颗粒水平上研究了流化催化裂化（FCC）催化剂的Br φ nsted酸性质.单个FCC组分（沸石、粘土、氧化铝和二氧化硅）的反应性通过UV/维斯显微光谱监测，并且显示只有粘土和沸石（Y和ZSM-5）含有强到足以催化4-氟苯乙烯转化成碳阳离子物质的Br Phnsted酸位点。通过将相同的方法应用于完整的FCC催化剂颗粒，已经发现沸石UV/维斯光谱的指纹是清楚可识别的。这种几乎排他的沸石活性由以下事实证实：对于不含沸石的FCC颗粒几乎没有观察到任何反应性。FCC催化剂颗粒的共聚焦荧光显微镜图像揭示了反应后具有高荧光信号的不均匀分布的微米级沸石结构域。通过在统计方法中检查实验室失活的FCC催化剂颗粒，观察到随着失活方法的严重性增加，沸石域的荧光强度和因此的布朗斯台德酸度降低的明显趋势。通过比较用反应性不同的两种苯乙烯获得的平均荧光强度，发现含有ZSM-5的FCC催化剂颗粒内的布朗斯台德酸位点强度比含有沸石Y的那些更均匀，如用氨的程序升温脱附所证实的。
A time-resolved in situ micro-spectroscopic approach has been used to investigate the Br phi nsted acidic properties of fluid-catalytic-cracking (FCC) catalysts at the single particle level by applying the acid-catalysed styrene oligomerisation probe reaction. The reactivity of individual FCC components (zeolite, clay, alumina and silica) was monitored by UV/Vis micro-spectroscopy and showed that only clay and zeolites (Y and ZSM-5) contain Br phi nsted acid sites that are strong enough to catalyse the conversion of 4-fluorostyrene into carbocationic species. By applying the same approach to complete FCC catalyst particles, it has been found that the fingerprint of the zeolitic UV/Vis spectra is clearly recognisable. This almost exclusive zeolitic activity is confirmed by the fact that hardly any reactivity is observed for FCC particles that contain no zeolite. Confocal fluorescence microscopy images of FCC catalyst particles reveal inhomogeneously distributed micron-sized zeolite domains with a highly fluorescent signal upon reaction. By examining laboratory deactivated FCC catalyst particles in a statistical approach, a clear trend of decreasing fluorescence intensity, and thus Br phi nsted acidity, of the zeolite domains is observed with increasing severity of the deactivation method. By comparing the average fluorescence intensities obtained with two styrenes that differ in reactivity, it has been found that the Br phi nsted acid site strength within FCC catalyst particles containing ZSM-5 is more uniform than within those containing zeolite Y, as confirmed with temperature-programmed desorption of ammonia.