介孔材料为硅源合成多级孔Mo/H-IM-5催化剂及其在甲烷无氧芳构化反应中的应用

在IM-5分子筛的合成体系中以介孔材料KIT-6作为硅源,制备出了多级孔IM-5复合分子筛(IM-5-K)。利用X射线衍射、扫描电镜、透射电镜、比表面积分析、NH3-TPD等手段对样品的物理性质和酸性进行表征。将经过钼修饰的Mo-IM-5-K催化剂应用于甲烷无氧芳构化反应中,考察其活性。催化测试结果显示,多级孔Mo-IM-5-K催化剂的最高甲烷转化率和芳烃产率为12.4%和6.9%,高于常规Mo-IM-5-C催化剂。同时,Mo-IM-5-K催化剂有更好的稳定性。催化剂反应活性和稳定性的差异是由于其具有不同的孔道结构和酸性所致。介孔的存在会影响活性Mo物种的落位及分布状态,有利于反应物与活性位的接触和芳烃产物的扩散,进而提高催化剂的活性和稳定性。     

多级孔IM-5分子筛的简易制备及其在甲烷芳构化中的催化性能

采用一步水热晶化法、不添加第二模板剂、仅通过控制合成条件,制备了具有多级孔道结构的IM-5-H分子筛。多级孔IM-5-H材料展现了与常规IM-5-C分子筛不同的形貌、结构和酸性质。由于IM-5-H分子筛载体介孔结构的促进作用,钼基Mo-IM-5-H催化剂在甲烷无氧芳构化反应中表现出较高的甲烷转化率（13.1%）、芳烃产率（7.5%）和稳定性。该研究为合成多级孔IM-5材料提供了一种简便的方法,同时扩展了微孔-介孔复合材料在甲烷芳构化反应中的应用。     

不同方法制备的Mo/HZSM-5催化剂上甲烷的芳构化反应

 采用机械混合、机械混合后焙烧和机械混合后微波处理等方法制备Mo／HZSM－5催化剂,并对催化剂上甲烷芳构化反应性能进行了考察．结果表明,与浸渍法相比,用机械混合法、固相反应法和微波法制备的催化剂,在保持甲烷转化率不变的前提下,能明显提高芳烃选择性并减少积炭的生成;不同方法制备的Mo／HZSM－5催化剂上Mo物种的落位不同,机械混合法、固相反应法和微波法使Mo物种较多地落位于分子筛外表面．结合反应结果可以得出,落位于分子筛外表面的Mo物种对甲烷芳构化反应更为有利,而且明显减少积炭的生成．     

MoO3/HBZSM-5催化剂上甲烷的无氧芳构化反应

以含硼杂原子分子筛HBZSM-5为载体,考察了其担载MoO3后催化甲烷无氧芳构化反应的性能,并结合XRD,IR,TG和SEM等手段对催化剂进行了表征.实验结果表明,MoO3/HBZSM-5催化剂具有较高的甲烷芳构化活性,但稳定性较差.随着引入分子筛骨架中硼量的增大,甲烷的极值转化率增高;随着反应温度的升高,MoO3/HBZSM-5催化剂的甲烷芳构化活性升高.从产物分布的变化来看,硼的引入对于催化剂上乙烯的选择性影响较大;与MoO3/HZSM-5催化剂相比,MoO3/HBZSM-5催化剂上乙烯选择性大大提高.     

Effect of the formation of secondary pores in zeolite ZSM-5 on the properties of molybdenum-zeolite catalysts for methane aromatization

A study is performed of 4% Mo/ZSM-5 (30) catalysts for methane aromatization prepared by solid-phase synthesis with mechanical mixing of a zeolite with MoO₃ followed by calcination at 550°C. Zeolite etched with sodium hydroxide solutions and dealuminated with aluminum nitrate solutions is used as a support. Catalytic studies of the catalysts are conducted. The effect of treating the initial zeolite on the properties of catalysts in methane aromatization is determined. The effect subsequently treating a zeolite support has on the acid sites of a catalyst is confirmed by means of temperature-programmed reduction and the temperature-programmed desorption of NH3. The formation of molybdenum ions in the +5 oxidation state during catalysis and the presence of graphitized carbon deposits on a spent catalyst’s surface are confirmed by EPR and temperature-programmed oxidation.     

HZSM-5结晶度和晶粒度对甲烷无氧芳构化催化剂性能的影响

使用高能球磨机通过研磨法制备了Ｍｏ／ＨＺＳＭ－５催化剂，对不同球磨时间下的催化剂结构进行了表征，并考察了其催化甲烷芳构化性能。结果表明，球磨使ＨＺＳＭ－５分子筛的粒度变小，且使Ｍｏ与骨架发生了同晶置换，导致ＺＳＭ－５骨架破坏；球磨时间越长，结晶度越低，其催化甲烷芳构化活性和苯选择性越差。因此，较高的结晶度和较大的晶粒度对甲烷的无氧芳构化反应更有利。     

Control of the properties of catalysts for methane aromatization by synthesizing ZSM-5 zeolites with different crystallite sizes

MFI zeolite materials (ZSM-5) with crystal sizes in the range from 0.10 to 1.70 μm have been synthesized. Acidic and surface properties, phase and morphological composition of the prepared zeolites have been studied by the IR sprectroscopy, nitrogen porosimetry, XRD, and scanning electron microscopy. Increasing crystal size was shown to decrease the general acidity of the zeolite. Synthesized zeolites served as supports for molybden-containing catalysts for methane aromatization prepared by using the solid phase synthesis approach. Diffuse reflectance IR spectroscopy, thermoprogrammed desoption of ammonia and ²⁷Al NMR spectroscopy were used to characterize the physicochemical properties of the catalysts. An increase in the crystallite size of the zeolite favors a decrease in the acidity of the catalysts and inhibits the formation of alumina molybdate during the catalyst preparation. As a result, a tendency to coke formation is suppressed and the performance of the catalysts in methane aromatization improved: methane conversion and aromatic hydrocarbon yield increase.     

Ga、Zn改性方法对HZSM-5催化剂丙烯芳构化性能的影响

以浸渍法和水热合成法对ZSM-5分子筛进行Ga、Zn改性,制得不同酸性的分子筛催化剂。采用XRD、SEM、NH3-TPD和XPS等表征手段,研究考察了Ga、Zn和不同引入方法对催化剂的孔结构、骨架结构特性和表面酸性的影响,并以丙烯芳构化为模型反应,考察了Ga、Zn改性对ZSM-5催化剂烯烃芳构化催化性能的影响。研究结果表明,Ga、Zn改性对催化剂形貌影响较小,但能明显改变催化剂的表面酸性和烯烃芳构化性能。Zn改性能降低催化剂的酸性,而Ga改性与其引入的方式有关,浸渍法引入催化剂的中强酸位略有下降,而水热合成法引入则显著增加了催化剂的总酸量。Ga、Zn改性均提高了芳构化反应的活性和芳烃选择性,并抑制催化剂表面积炭。     

甲烷在MoO_3／HZSM－5分子筛催化剂上的非氧催化转化

研究了反应温度、空速、Ｍｏ担载量和焙烧温度对ＭｏＯ３／ＨＺＳＭ－５催化剂上甲烷的芳构化反应的影响．ＨＺＳＭ－５分子筛的Ｂｒｏｎｓｔｅｄ酸性、孔道结构和Ｍｏ在分子筛中的分布是影响催化性能的重要因素．ＨＺＳＭ－５上Ｍｏ担载量为２～３％时活性最佳，在１０１３Ｋ反应温度下甲烷转化率可达９％，芳烃选择性大于９０％．空速影响的实验表明乙烯是反应的初始产物．在此基础上提出了＂甲烷酸助异裂活化＂的新概念、＂金属钼类碳烯中间物＂的新观点和甲烷芳构化的可能机理．     

纳米HZSM-5沸石的骨架热稳定性及其作为催化剂的可再生性

采用高温焙烧和积炭失活-空气烧炭再生方法研究了纳米ZSM-5沸石的骨架热稳定性和用纳米HZSM-5沸石制成的芳构化催化剂的再生重复使用性能,还采用XRD、TG、FTIR、NH3-TPD和N2物理吸附,以及C4液化气固定床临氢芳构化反应对沸石和催化剂样品的物化性质作了表征.结果表明:纳米ZSM-5沸石具有良好的骨架热稳定性,在马弗炉的静止空气气氛中恒温焙烧800℃时仍可保持骨架结构.纳米HZSM-5型芳构化催化剂在C4液化气固定床临氢芳构化反应中不但活性稳定性好,而且可以再生重复使用,具有很高的工业应用价值.     

The synergic effect between Mo species and acid sites in Mo/HMCM-22 catalysts for methane aromatization

The acid properties of Mo/HMCM-22 catalyst, which is the precursor form of the working catalyst for methane aromatization reaction, and the synergic effect between Mo species and acid sites were studied and characterized by various characterization techniques. It is concluded that Br?nsted and Lewis acidities of HMCM-22 are modified due to the introduction of molybdenum. We suggest a monomer of Mo species is formed by the exchange of Mo species with the Br?nsted acid sites. On the other hand, coordinate unsaturated sites (CUS) are suggested to be responsible for the formation of newly detected Lewis acid sites. Computer modelling is established and coupling with experimental results, it is then speculated that the effective activation of methane is properly accomplished on Mo species accommodated in the 12 MR supercages of MCM-22 zeolite whereas the Br?nsted acid sites in the same channel system play a key role for the formation of benzene. A much more pronounced volcano-typed reactivity curve of the Mo/HMCM-22 catalysts, as compared with that of the Mo/HZSM-5, with respect to Mo loading is found and this can be well understood due to the unique channel structure of MCM-22 zeolite and synergic effect between Mo species and acid sites.     

ZSM-5分子筛的脱硅改性及加氢改质性能

考察了水热与碱联合处理过程中两者的先后顺序对ZSM-5分子筛酸性和孔结构的影响,并与单独的水热和碱处理进行了比较。结果表明,水热后的碱处理对ZSM-5分子筛具有骨架脱硅、骨架补铝和清除非骨架铝物种三重作用,而碱处理后的水热处理具有骨架脱铝和部分骨架稳定化双重作用。与先水热处理再碱处理相比,先碱处理后的水热处理在优化分子筛酸性和产生介孔方面更加有效。基于水热-碱联合处理的HZSM-5分子筛所制备的催化剂对催化裂化汽油的加氢改质表现出适中的异构化活性、较高的烯烃芳构化活性以及最高的稳定性。     

分子筛性质对Mo／HZSM－5催化剂上甲烷无氧脱氢芳构化反应的影响

 通过改变合成条件与合成体系，考察了不同硅源合成的HZSM－5分子筛对Mo／HZSM－5催化剂上甲烷无氧脱氢芳构化反应性能的影响．结果表明，用水玻璃合成的HZSM－5分子筛负载Mo后，其催化性能优于用硅溶胶合成的分子筛．1HMASNMR测定结果表明，前者的Br¨onsted酸 浓度较后者大．通过改变合成条件，减小HZSM－5分子筛的粒度，可以提高催化剂在甲烷无氧脱氢芳构化反应中的稳定性．     

甲烷在Mo/HZSM-5催化剂上的脱氢聚合反应

对不同Mo含量的Mo／HZSM－5催化剂的结构进行了表征，并对这些催化剂的甲烷非氧气氛下的转化反应进行了考察．催化剂的BET比表面积及酸性随Mo含量的增加而降低，当Mo含量大于5％时，Mo对ZSM－5分子筛的晶型有影响，并出现MoO3物相．甲烷在700℃时可高选择性地生成苯和乙烯，最佳Mo含量大约为2％．纯的MoO3或HZSM－5上该反应几乎不进行，因此，可能是分散的钼氧离子和分子筛的酸中心是甲烷转化的活性中心，只有二者的协同作用才能促进甲烷的转化．反应后催化剂中的钼物种被还原了．催化剂上的积炭可能是催化剂失活的主要原因之一，烧炭后催化剂活性基本恢复．     

Aromatization ofn-butane over Ni-ZSM-5 and Cu-ZSM-5 zeolite catalysts prepared by using Ni and Cu impregnated silica, fiber

The reaction ofn-butane aromatization was carried out over Ni-ZSM-5 and Cu-ZSM-5 zeolite catalysts prepared by using Ni and Cu impregnated silica fiber during the process of ZSM-5 zeolite synthesis. The catalysts prepared were characterized by X-ray powder diffraction, nitrogen adsorption and X-ray fluorescency. The acidic properties of the catalysts were investigated by temperature-programmed desorption of ammonia using a mass spectrometer equipped with a QTMD detector. The effect of catalyst pretreatment, reaction temperature, and time on stream on the reaction ofn-butane to aromatic hydrocarbons were investigated. The modification of ZSM-5 by Ni and Cu increased the selectivity to aromatic hydrocarbons. The state of Ni and Cu and their stabilization in the ZSM-5 structure was highly influenced by the mode of catalyst pretreatments.     

甘油辅助HZSM-5分子筛的制备及其甲烷无氧芳构化催化性能研究

以正硅酸乙酯(TEOS)为硅源,甘油为辅助剂,在水热条件下合成HZSM-5分子筛。考察甘油添加量、晶化时间对HZSM-5分子筛的晶粒尺寸、相对结晶度和酸性等性质及其甲烷无氧芳构化催化性能的影响。利用X射线衍射(XRD)、扫描电镜(SEM)、氨程序升温脱附(NH₃-TPD)等分析手段对不同条件合成的HZSM-5分子筛样品进行表征。结果表明,在添加一定量的甘油辅助剂的条件下,通过调控晶化时间,可以提升HZSM-5分子筛的相对结晶度,在一定程度上抑制无定型SiO₂的产生,增加其酸量。在甲烷无氧芳构化反应中,甘油辅助合成的HZSM-5分子筛催化剂表现出优良的催化性能,与未添加甘油合成的HZSM-5分子筛催化剂相比,甲烷转化率、苯选择性和芳烃选择性均有较大提高,且具有较强的稳定性与容炭能力。     

Non-oxidative aromatization of C1 to C3 hydrocarbons over Pd-promoted Ga/HZSM-5 catalyst under mild conditions

The Pd-promoted Ga/HZSM-5 catalyst was prepared by impregnation method and its catalytic activity for non-oxidativearomatization of C1 to C3 hydrocarbons was assessed using a microreactor-GC system operated with temperature at 823 K andspace velocity at 410 h1.The catalyst is more catalytically active for methane conversion than Ga/HZSM-5.The massspectroscopy analyses confirmed that13CH4 was converted to aromatic products.     

稀土对HZSM—5上正己烷芳构化性能的影响

以正己烷为原料,在连续流动常压反应装置上考察了稀土改性HZSM－5沸石催化剂的芳构化和裂解性能,用红光谱,X射线衍射,X光电子能谱等研究了这些离子改性的沸石催化剂的表面性质,比较了机械混合法和浸渍法引入稀土对催化剂性能的影响,稀土可提高混合法制备的改性催化剂的芳构化性能,B酸中心是正已烷构化的活性中心,L酸中心则对正己烷的裂解起重要作用。     

ECNU-13: A High-Silica Zeolite with Three-Dimensional and High-Connectivity Multi-Pore Structures for Selective Alkene Cracking

A high-silica zeolite ECNU-13 (Si/Al=23) with a new three-dimensional (3D) pore system and a nanosized morphology has been developed, consisting of multitudes of 10-membered ring (10-R) medium pores and one set of 8-R small pores. A phase-discrimination strategy was proposed to synthesize ECNU-13 by regulating the gel compositions and nucleation processes that were used for preparing 12-R large-pore germanosilicate IM-20 with the known UWY topology. The crystallization was directed towards forming one set of single four-ring (s4r) composite building units together with one set of double four-ring (d4r) rather than two different types of d4r units in IM-20. The electron crystallographic investigations elucidated that the ECNU-13 structure was composed of two kinds of polymorphs as a result of distinct atomic positionings in s4r units. In catalytic cracking of 1-butene, ECNU-13 exhibited high propene selectivity (55.6 %) and propene to ethylene molar ratio (>4.7) superior to well-studied conventional ZSM-5 zeolite catalyst.     

27Al和29Si MAS-NMR对Mo/HZSM-5催化剂的研究

使用＾２９Ａｌ固体离分辨核磁技术对甲烷无氧芳构化催化剂Ｍｏ／ＨＺＳＭ－５分子筛进行了研究，发现ＨＺＳＭ－５分子筛本体中仅含有少量非骨架Ａｌ，Ｍｏ物种与分子筛骨架Ａｌ的相互作用随Ｍｏ担载量以及焙烧的温度的升高而增加，在高温焙烧下，Ｍｏ物种会使分子筛骨架严重脱铝，并且生成Ａｌ２（ＭｏＯ４）３新相，最终导致分子筛骨架塌陷，催化性能下降。