Facile Construction of Furanoacenes by a Three-Step Sequence Going through Disilyl-exo-cyclic Dienes

Facile synthesis of various benzonaphthofurans was achieved by intramolecular hydroarylation of 1,4-disilyl-2-aryloxy-1,3-enynes followed by cycloaddition with arynes or alkenes and finally desilylaromatization. The three-step transformation can be operated sequentially in one-pot, providing with a range of furanoacenes easily and highly effectively.     

Increasing the yield of aromatic hydrocarbons in aromatization of n-butane over Ga/H-ZSM-5 zeolite using a palladium membrane

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不同温度予处理Pt／Al2O3催化剂对其表面结构和反应性能的影响

由于链烷烃在Pt/Al_2O_3催化剂上反应的复杂性,许多学者为了深入研究包括催化剂制备、反应机理等的内在规律,进行了大量的研究,取得了许多重要成果。近几年来,较多的工作着重从分散态金属的几何和电子因素,及金属同担体的相互作用进行考察,在催化剂制备方面,更多的注意添加第2、第3组元、杂质或毒物等对金属催化性能的调变作用,以期开发出高选选择性催化剂。而对不同气氛、不同还原温度下     

Gallium-containing zeolites: characterization of catalytic role of gallium species in converting light paraffins to aromatics

The structures and the chemical nature of gallium species in gallium-containing zeolite catalysts prepared by hydrothermal synthesis and post-synthesis treatments are discussed based on the results of X-ray absorption spectroscopy (XAS), including X-ray absorption near edge structure (XANES) and Extended X-ray absorption fine structure (EXAFS), and nuclear magnetic resonance (NMR) investigations. The in-situ analysis of properties of gallium active sites during oxidation/reduction cycles has been found to be further helpful on the understanding of the catalytic role of gallium species in the aromatization of alkanes.     

十元环分子筛在甲醇芳构化反应中催化性能的研究

合成了ZSM-5、ZSM-22、EU-1、MCM-22和ITQ-13具有十元环孔道结构的5种分子筛,研究了分子筛结构、酸性分布等因素对其在甲醇芳构化反应中催化性能的影响。研究表明,不同结构分子筛的形貌、酸性及孔径均存在较大差异,进而影响了其在甲醇制芳烃反应中的催化活性和稳定性。研究的5种分子筛中,ZSM-5表现出最佳的芳构化活性,芳烃收率达34.8%,MCM-22芳烃收率约为21.9%,而其他3种结构的分子筛催化剂基本未表现出甲醇芳构化活性。通过添加具有芳构化性能的Ga物种对ZSM-5和MCM-22进行改性,可显著提升芳烃收率,Ga/ZSM-5上芳烃收率达到40.8%,Ga/MCM-22上芳烃收率可提高到27.1%。另外,采用TG/DTA、GC等方法研究了失活催化剂的积炭情况,发现分子筛结构对积炭量、积炭组成及积炭分布存在显著影响。     

Efficiently Aerobic Dehydrogenation of N-Heterocycles and Hydrocarbons over MnAl Oxides

Dehydrogenation of saturated N-heterocycles and hydrocarbons provides an important route to corresponding aromatic compounds. Herein, an efficient and selective MnAlO-catalyzed aerobic oxidative dehydrogenation of five- and six-membered N-heterocycles, imines and hydrocarbons is presented. The reaction features excellent yields of the products, mild reaction conditions, readily available and reusable catalyst. Various N-heterocycles and hydrocarbons can be tolerated by the reaction system and transformed to the corresponding aromatic counterparts. Mechanistic studies revealed that the reaction proceeds mainly through an electron transfer mechanism.     

ZSM-5酸改性对甲醇芳构化性能的影响

利用硝酸、草酸和酒石酸溶液对ZSM-5分子筛进行改性,并采用XRD、SEM、NH₃-TPD、XRF、²⁷Al MAS NMR、吡啶吸附红外光谱和N₂吸附-脱附对ZSM-5分子筛结构、酸量、比表面积及孔体积等物化性质进行表征分析。在反应温度为422℃,甲醇质量空速为4.74 h^-1的条件下,考察了ZSM-5分子筛的催化活性。结果表明,采用不同酸改性ZSM-5分子筛,影响了分子筛的比表面积、酸性及孔体积,从而改变了催化剂的催化性能。在甲醇芳构化（MTA）反应中,酸改性后的分子筛表现出良好的催化活性,且草酸改性后的催化剂表现出较高的催化活性及选择性,反应8 h时,芳烃及BTX收率分别达到57.40%和39.40%。     

Activation of Mo/HZSM-5 for methane aromatization

The effect of Mo/HZSM-5 pretreatment at 973 K in inert (He), oxidizing (artificial air), and carbu-rizing (CH4/He mixture) atmospheres on its performance in non-oxidative methane dehydroaroma-tization (MDA) was investigated. The effect of post-synthesis silylation on deactivation of external acid sites was also studied. Precarburization resulted in increased aromatic selectivity and im-proved catalyst stability. The benzene selectivity was the highest for the silylated Mo/HZSM-5 cata-lyst (benzene+naphthalene selectivity after 1 h on stream was close to 100%). The deactivation of precarburized zeolites was less pronounced than that of zeolites heated in air or He. During heating in air or He, larger fractions of the molybdenum oxide species diffused into the micropores than during heating in methane. Carburization of the molybdenum oxide species in the micropores dur-ing MDA resulted in the formation of molybdenum carbide particles, and these contributed to pore blocking, making the Br?nsted acid sites inaccessible. The formation of molybdenum carbides dur-ing heating in methane resulted in a less mobile Mo phase. It is argued that the presence of molyb-denum carbide particles in the micropores contributes to rapid catalyst deactivation, in addition to the formation of hard coke on the external surface.     

Ga改性ZSM-5分子筛催化丙烷芳构化性能研究

用离子交换法制备Ga改性ZSM-5双功能催化剂,并结合XRD、SEM、BET、NH₃-TPD、Py-IR及ICP、XPS等多种技术进行表征,考察分子筛硅铝比(Si/Al)和催化剂氧化还原预处理条件对分子筛的酸性质、Ga物种的存在状态及其丙烷芳构化催化性能的影响。研究表明,硅铝比不仅可以改变分子筛的酸性,也会影响分子筛中非骨架Ga物种与分子筛表面的相互作用程度,进而影响含Ga分子筛的丙烷芳构化性能。在质量空速1.0 h^-1、反应温度550℃ 下,Si/Al比为30的Ga-HZSM-5分子筛丙烷转化率和芳烃收率最高。Ga物种的引入可以提高丙烷的转化率和芳烃的选择性,并抑制烷烃、烯烃的裂解。H₂还原处理,将分子筛表面Ga₂O₃还原为低价的Ga⁺和GaH⁺₂物种,促进了Ga物种向分子筛微孔迁移;还原-氧化处理后,Ga⁺和GaH⁺₂物种氧化成GaO⁺,占据分子筛孔道离子交换位,显著提高了催化剂的芳构化活性。