Synthesis and Characterization of ZSM-5/β Co-Crystalline Zeolite

ZSM-5/β co-crystalline zeolites with different content of ZSM-5 have been synthesized by adding different amount of ZSM-5 to the synthetic system of β zeolite with NaAlO2, silica sol as the source of aluminum and silica, respectively, and TEA as the template under controlled condition of the synthesis. The ZSM-5/β co-crystalline zeolite was studied by XRD, SEM, BET and NH3-TPD. The reaction activity of toluene alkylation was investigated with a mixture of toluene-methanol as the feedstock in a pulse micro-reactor over the ZSM-5/β co-crystalline zeolite. It is found that ZSM-5/β co-crystalline zeolite has two kinds of zeolite structure including ZSM-5 and β zeolite, not in the form of a physical mixture. The pore structure of ZSM-5/β co-crystalline zeolites is different from that for β zeolite, ZSM-5 and their physical mixture. In addition, the peaks of both high and low temperature desorption of ammonia over the ZSM-5/β co-crystalline zeolite shift 23 ℃ to lower temperatures and the acid amount of its strong acid is 3% more than the physical mixture. So the ZSM-5/β co-crystalline zeolite produces the highest content of xylene, which is 10.4% higher than the physical mixture. And the ZSM-5/β co-crystalline zeolite has better selectivity for toluene alkylation and weaker de-methylation than β zeolite, ZSM-5 and their physical mixture.     

Theoretical Study of Ethanethiol Adsorption on HZSM-5 Zeolite

The density functional theory and the cluster model methods have been employed to investigate the interactions between ethanethiol and HZSM-5 zeolites. Molecular complexes formed by the adsorption of ethanethiol on silanol H3SiOH with two coordination forms, model Bronsted acid sites of zeolite cluster H3Si(OH)Al(OH)2SiH3 interaction with ethanethiol, aluminum species adsorbed ethanethiol have been comparatively studied. Full optimization and frequency analysis of all cluster models have been carried out using B3LYP hybrid method at 3-21G basis level for hydrogen atoms and 6-31G(d) basis set level for silicon, aluminum, oxygen, carbon, and sulfur atoms. The structures and energy changes of different coordination forms of H3Si(OH)Al(OH)2SiH3-ethanethiol, silanol-ethanethiol and Al(OH)3-ethanethiol have been studied. The calculated results showed the nature of interactions was van der Waals force as exhibited by not much change in geometric structures and properties. The preference order of ethanethiol adsorbed on HZSM-5 zeolite may be residual aluminum species, bridging hydroxyl groups and silanol OH groups from the adsorption heat. The adsorbed models of protonized ethanethiol on bridging hydroxyl OH groups and linear hydrogen bonded ethanethiol on bridging OH groups suggested in literature might not exist as revealed by this theoretical calculation. Possible adsorption models were obtained for the first time.     

Effects of Calcination Temperature on the Acidity and Catalytic Performances of HZSM-5 Zeolite Catalysts for the Catalytic Cracking of n-Butane

The acidic modulations of a series of HZSM-5 catalysts were successfully made by calcination at different treatment temperatures, i.e. 500, 600, 650, 700 and 800 ℃, respectively. The results indicated that the total acid amounts, their density and the amount of B-type acid of HZSM-5 catalysts rapidly decreased, while the amounts of L-type acid had almost no change and thus the ratio of L/B was obviously enhanced with the increase of calcination temperature (excluding 800 ℃). The catalytic performances of modified HZSM-5 catalysts for the cracking of n-butane were also investigated. The main properties of these catalysts were characterized by means of XRD, N2 adsorption at low temperature, NH3-TPD, FTIR of pyridine adsorption and BET surface area measurements. The results showed that HZSM-5 zeolite pretreated at 800 ℃ had very low catalytic activity for n-butane cracking. In the calcination temperature range of 500-700 ℃, the total selectivity to olefins, propylene and butene were increased with the increase of calcination temperature, while, the selectivity for arene decreased with the calcination temperature.The HZSM-5 zeolite calcined at 700 ℃ produced light olefins with high yield, at the reaction temperature of 650 ℃ the yields of total olefins and ethylene were 52.8% and 29.4%, respectively. Besides, the more important role is that high calcination temperature treatment improved the duration stability of HZSM-5zeolites. The effect of calcination temperature on the physico-chemical properties and catalytic performance of HZSM-5 for cracking of n-butane was explored. It was found that the calcination temperature had large effects on the surface area, crystallinity and acid properties of HZSM-5 catalyst, which further affected the catalytic performance for n-butane cracking.     

Ceric ammonium nitrate supported HY-zeolite：An efficient catalyst for the synthesis of 1, 8-dioxo-octahydroxanthenes

Ceric ammonium nitrate （CAN） supported HY-zeolite has been used as an efficient catalyst for the one- pot synthesis of 1,8-dioxo-octahydroxanthenes from the readily available 1,3-diketone and aromatic aldehydes under solvent-free conditions. The present methodology is cost-effective in addition to other advantages like high yields of products in shorter reaction time and simple workup procedure without the use of any injurious solvents.     

多酸结构对纳米钛硅TS-1沸石催化氧化脱硫性能的影响

采用浸渍法合成了纳米钛硅TS-1沸石负载的钼系列多金属氧酸盐(POM)复合催化剂,采用扫描电子显微镜(SEM)、傅里叶红外光谱(FT-IR)、固体紫外漫反射(UV-Vis)、X-ray粉末衍射(XRD)、氮气吸附脱附(BET)、³¹P和²⁹Si魔角核磁共振(MAS-NMR)等对催化剂的结构进行表征。 研究结果表明,在低温焙烧或烘干条件下,负载后催化剂多酸的结构保持,钼酸铵高温(550 ℃)焙烧后转变为三氧化钼。 以有机硫化物噻吩(TH)、苯并噻吩(BT)和二苯并噻吩(DBT)的正辛烷溶液为模拟油品评价了催化剂的氧化脱硫性能。 实验结果表明,纳米TS-1沸石载体上不同结构多酸作为脱硫催化剂对硫化物的脱除活性顺序为:Keggin型Mo-POM＞Anderson型Mo-POM＞Dawson型Mo-POM＞Mo-金属氧化物。以上述负载的多酸为催化剂,在反应条件为:V(模拟油)=V(乙醇)=10.0 mL,m(催化剂)=0.2 g,n(H₂O₂)∶n(S)=10∶1,温度60 ℃,硫化物按照由易到难的脱除顺序为TH＞DBT＞BT,与常规的TS-1沸石或者多酸催化剂的脱除顺序存在明显差异。 这是纳米TS-1沸石对于有机硫分子氧化反应的择形效应和POM催化氧化脱硫的电子云密度影响综合作用的结果。 Keggin型Mo-POM催化剂具有良好的循环使用性能,是一类制备方法简单、催化活性高且稳定性好的绿色环保型催化剂。     

无溶剂热处理固相转化法简易制备沸石咪唑酯骨架材料

设计开发了一种无需溶剂,通过热处理固相转化制备沸石咪唑酯骨架材料(ZIFs)的简易方法.该方法无需溶剂及其它预处理,只需将金属源与有机配体固相混合后于低温(200℃)热处理即可实现多孔晶体材料的制备.所合成材料H-ZIF-67为具有方纳石拓扑结构的纳米晶体,与传统方式合成的ZIFs材料一致.粉末X射线衍射(PXRD)分析结果表明产物的晶体结构与标准ZIFs谱图一致.通过扫描电子显微镜(SEM)、透射电子显微镜(TEM)、N₂吸附-脱附分析、热重分析(TGA)和傅里叶变换红外光谱(FTIR)等手段对合成的材料进行了表征,发现H-ZIF-67材料具有与ZIFs材料类似的特性.该方法经济、高效,摒弃了传统方法合成ZIFs材料周期长、处理过程复杂的弊端,为ZIFs材料的量产提供了新思路.     

用环境友好催化剂H-β沸石制备紫罗兰酮

用环境友好催化剂Ｈ－β沸石催化假性紫罗兰酮环化制备紫罗兰酮。考察了催化剂的用量、反应温度和时间对反应的影响,并测定了假性紫罗兰酮环化反应的速率常数和活化能（３６．４ｋＪ／ｍｏｌ）．Ｈ－β沸石能被回收、再生和重复使用,且与用新鲜Ｈ－β沸石时几乎有相同的紫罗兰酮产率。     

丝光沸石骨架中Fe的XAFS表征

通过水热法合成了骨架含铁的杂原子丝光沸石,采用XRD,FT-IR及TPR等表征技术确认铁进入了分子筛骨架。利用XAFS地分子筛中铁的精细结构和配位环境进行了表征和计算,近边吸收的Fe-K边前跃迁证实铁在分子筛骨架中位于四面体配位环境中,与邻近原子存在共价键作用;铁-氧配位键长为0.188～0.189nm.     

键阻断原理构建中孔A型沸石

采用不同类型的有机硅烷化SiO₂作为基本合成单元, 制备了具有晶内中孔的A型沸石。考察了反应碱度、Si/Al比、晶化时间等合成条件对产品的影响。结果表明, 甲氨基丙基三甲氧基硅烷是合成中孔A型沸石的最佳硅烷化试剂;硅烷化试剂的应用, 使中孔沸石晶化过程可以通过“键阻断原理”有效控制;沸石的中孔尺寸可以通过不同类型的有机硅烷化试剂进行调控; 一定范围内, 其外比表面积、中孔体积随SiO₂表面硅烷化度的增加而增加。通过沸石晶化过程中的“键阻断”, 可以制备具有晶内中孔的A型沸石。     

制备方法对Co-MOR催化剂CH4选择还原NO性能的影响

采用离子交换法、浸渍法制备一系列的Co-MOR 催化剂, 并将其用于CH₄选择性催化还原 NO_x(CH₄-SCR)反应. 运用X 射线衍射(XRD)、X 射线荧光光谱(XRF)、扫描电子显微镜(SEM)、紫外-拉曼(UVRaman)光谱、X射线光电子能谱(XPS)、NO程序升温脱附(NO-TPD)等手段对催化剂进行了表征. 结果表明, 浸渍法制备的催化剂, Co以Co₃O₄形式存在; 而离子交换法制备的催化剂, Co以离子形式进入丝光沸石(MOR)骨架之中, 在催化剂上形成更多的Co²⁺和[Co-O-Co]²⁺, 形成更均匀NO吸附中心和CH₄-SCR反应活性中心. 催化剂活性评价表明离子交换法制备的催化剂具有更宽的活性温度区间, Co(0.30)-MOR 催化剂在327-450℃温度范围内NO转化率大于50%.