Large Zeolite H-ZSM-5 Crystals as Models for the Methanol-to-Hydrocarbons Process: Bridging the Gap between Single-Particle Examination and Bulk Catalyst Analysis
Large Zeolite H-ZSM-5 Crystals as Models for the Methanol-to-Hydrocarbons Process: Bridging the Gap between Single-Particle Examination and Bulk Catalyst Analysis
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DOI：
10.1002/chem.201203351
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发表时间：
2013-06-01
影响因子：
4.3
通讯作者：
Weckhuysen, Bert M.
中科院分区：
文献类型：
--
作者：
Hofmann, Jan P.;Mores, Davide;Weckhuysen, Bert M.
研究了350 ℃和500 ℃下大尺寸棺材形H-ZSM-5沸石在甲醇制烃（MTH）反应中的催化、失活和再生特性。在固定床反应器中，采用在线气相流出物分析和残留物检测的方法，考察了大型棺材型H-ZSM-5沸石晶体的整体性质，并将其作为MTH反应的模型催化剂。这些发现与在单个颗粒水平上通过使用偏振依赖性紫外-可见光谱和质谱技术在原位显微光谱反应池中反应后所作的观察有关。观察到光谱测量与通过对废催化剂材料的保留烃分析和飞行时间二次离子质谱法对烃沉积物的分析之间的极好的一致性。所获得的数据揭示了在更高的反应温度下朝向在沸石外表面上的更冷凝的焦炭沉积物的转变。沸石在固定床反应器设置经历了更多的焦炭沉积比那些在原位显微光谱反应池中反应。通过在550 ℃下在O2/惰性气体混合物中氧化进行大沸石晶体的再生研究。紫外-可见分光光度计测量使用苯乙烯衍生物的齐聚作为探针反应表明，强酸中心的分数减少再生过程中。这种变化伴随着再生后获得的初始转化率的略微降低。反应温度越高，H-ZSM-5失活越快。
The catalytic, deactivation, and regeneration characteristics of large coffin-shaped H-ZSM-5 crystals were investigated during the methanol-to-hydrocarbons (MTH) reaction at 350 and 500 degrees C. Online gas-phase effluent analysis and examination of retained material thereof were used to explore the bulk properties of large coffin-shaped zeolite H-ZSM-5 crystals in a fixed-bed reactor to introduce them as model catalysts for the MTH reaction. These findings were related to observations made at the individual particle level by using polarization-dependent UV-visible microspectroscopy and mass spectrometric techniques after reaction in an in situ microspectroscopy reaction cell. Excellent agreement between the spectroscopic measurements and the analysis of hydrocarbon deposits by means of retained hydrocarbon analysis and time-of-flight secondary-ion mass spectrometry of spent catalyst materials was observed. The obtained data reveal a shift towards more condensed coke deposits on the outer zeolite surface at higher reaction temperatures. Zeolites in the fixed-bed reactor setup underwent more coke deposition than those reacted in the in situ microspectroscopy reaction cell. Regeneration studies of the large zeolite crystals were performed by oxidation in O2/inert gas mixtures at 550 degrees C. UV-visible microspectroscopic measurements using the oligomerization of styrene derivatives as probe reaction indicated that the fraction of strong acid sites decreased during regeneration. This change was accompanied by a slight decrease in the initial conversion obtained after regeneration. H-ZSM-5 deactivated more rapidly at higher reaction temperature.