沸石的碱处理溶解

晶体的溶解与晶体的生长存在着密切的联系，详细研究沸石晶体的溶解行为将有助于更好的理解沸石晶体的生长机理。鉴于目前对沸石晶体的碱处理溶解行为的研究尚处于初始阶段，所以从沸石碱溶解的几点关键内容出发，如沸石的硅铝比对沸石碱处理的影响，焙烧“活化”后沸石的碱处理溶解行为的变化，沸石与其无定形前驱物的溶解性差异以及沸石的溶解机理和溶解动力学方程方面，综述了有关沸石碱处理溶解研究方面的最新动态。     

New Preparation Method of CdS Clusters Encapsulated in Y-Type Zeolites

CdS clusters encapsulated in Y-type zeolite were prepared by a novel technique with non-aqueous systems. The mechanical mixture of CdCl₂· 2.5H₂O crystal with Y-type zeolite was heated at 773 K, followed by the H₂S treatment at 373 K, resulting in the formation of CdS clusters with the size <2.3 nm.     

Catalytic cracking of 1-butene to propene and ethene on MCM-22 zeolite

Catalytic cracking of butene to propene and ethene was investigated over HMCM-22 zeolite. The performance of HMCM-22 zeolite was markedly influenced by time-on-stream (TOS) and reaction conditions. A rapid deactivation during the first 1 h reaction, followed by a quasi-plateau in activity, was observed in the process along with significant changes in product distributions, which can be attributed to the fast coking process occurring in the large supercages of MCM-22.

Properly selected reaction conditions can suppress the secondary reactions and enhance the production of propene and ethene. According to the product distribution under different butene conversion, we propose a simple reaction pathway for forming the propene, ethene and by-products from butene cracking.

HMCM-22 exhibited similar product distribution with the mostly used high silica ZSM-5 zeolite under the same conversion levels. High selectivities of propene and ethene were obtained, indicating that the 10-member ring of MCM-22 zeolite played the dominant role after 1 h of TOS. However, MCM-22 exhibited lower activity and stability than that on high silica ZSM-5 zeolite with longer time-on-stream.     

清液体系中高性能T型沸石分子筛膜的合成

由摩尔组成为SiO2:Al2O3:Na2O:K2O:H2O=1:0.015:0.25:0.08:25的澄清溶液,在预涂晶种的管状莫来石支撑体上水热合成T型沸石分子筛膜.在高于100℃清液体系中合成出了高性能T型沸石分子筛膜.用X射线衍射(X-ray diffraction,XRD)仪和扫描电子显微镜(scanning electron microscope,SEM)对150℃下合成35 h的分子筛膜进行了表征.XRD谱表明:T型沸石分子筛成功地生长在预涂晶种的支撑体上.支撑体的外表面覆盖着20 μm厚有取向的晶体层.从SEM照片判断,起到分离作用的是生长致密的中间层,而不是表层.在150℃下制备的膜,对水/乙醇、水/异丙醇混合物具有高渗透汽化分离性能.优异的渗透汽化性能归因于在涂有晶种的多孔支撑体上生长了一层高结晶度且缺陷较少的T型沸石分子筛晶体层.     

ZrO2 和Al2O3支撑的MFI 型沸石分子筛膜:支撑体材料对膜性能的影响

采用水热合成法，以纯SiO2为源物质，在介孔Y2O3掺杂的ZrO2(YZ)及大孔α-Al2O3支撑体上制备出高质量的MFI型沸石分子筛膜，通过H2／n-C4H10气体混合物的渗透分离和p-xylene的蒸发研究了不同支撑体上MFI型沸石分子筛膜分离性能，在较低温度范围，YZ支撑的MFI型沸石分子筛膜中n-C4H10的渗透率比Al2O3支撑的膜高很多，最大n-C4H10与H2的分离率达到500，Al2O3支撑的膜中py-xylene的蒸发流量随时间下降很快，而YZ支撑的膜中的蒸发流量则变化缓慢，用XRD对膜的晶体结构进行分析，通过多种温度下热处理不同支撑体上的膜样品研究了其热稳定性与支持体材料的关系，YZ支撑的MFI型沸石分子筛膜的MFI结构在1000摄氏度后仍能保持，而Al2O3支撑的膜950摄氏度时已完全转变为石英相，研究结果表明，YZ支撑的MFI型沸石分子筛膜比Al2O3支撑的膜表现出更好的厌不性，热稳定性以及抗阻塞性。     

Impregnation of X Zeolite with Alkaline Hydroxide During the Synthesis

Enhancement of the basic properties of the X zeolite with FAU framework has been carried out during synthesis, without further treatment such as ion-exchange or impregnation. Control of the washing stage enables retention of the optimum amount of alkaline hydroxides, which increases the basic catalytic activity of X zeolite in the alkylation of toluene. This alkaline hydroxides neither affect the FAU framework nor the silicon/aluminium molar ratio of the X zeolite. The optimum (Na + K)/Al molar ratio of the improved catalyst was 1.06 corresponding to a washing volume of 200 mL. This X zeolite presented better catalytic activity than a cesium-zeolite prepared by ion-exchange. The presence of hydroxysodalite impurity in the X zeolite increased the amount of impregnated alkaline hydroxides but not the catalytic activity. The present study shows that it is possible to increase the basic properties of the X zeolite directly in the synthesis process.     

银型抗菌沸石的合成

沸石类抗菌材料是一种无机多功能材料，具有耐酸，耐碱，过滤除污，吸附除臭以及长效广泛的杀菌和抑菌效果，主要介绍液相，固相离子交换法将具有抗菌性能的银离子与沸石合成为抗菌沸石，用正交法确定两种方法的较佳条件，并进行比较，用红外光谱对沸石原样与抗菌沸石进行比较分析，同时对合成的抗菌沸石进行了抗菌性能测试。     

Study of the sorption and acidic properties of MTW-type zeolite

The acidity of H-MTW-type zeolite has been investigated using infrared spectroscopy of adsorbed pyridine. Pore volume has been measured by nitrogen andn-hexane adsorption. The zeolite exhibits infrared signals at 3612 and 3580 cm^–1 tentatively attributed to bridging hydroxyl groups vibrating in the main channel and in the six-membered rings of the structure, respectively. Both hydroxyl groups possess high acid strength and are readily accessible to pyridine. H-MTW shows an-hexane cracking activity at 350°C comparable to that obtained with MFI and BEA-type materials with a product selectivity between medium and large pore structural types.     

多孔ZSM-5沸石负载Ni2P催化剂对苯乙炔的选择性加氢性能

以酸性多孔ZSM-5沸石(HZSM-5-M)和高比表面积的氧化硅(SiO2)为载体，采用等体积浸渍法制备了负载Ni2P催化剂(Ni2P/HZSM-5-M和Ni2P/SiO2)，对比研究了它们在苯乙炔选择性加氢反应中的催化性能。采用XRD、N2吸附-脱附、NH3-TPD、H2-TPR、SEM和TEM对载体及其负载的Ni2P催化剂进行了表征。催化剂活性结果为：当反应时间为2 h，苯乙炔在Ni2P/HZSM-5-M催化剂的转化率为98.5%，而在Ni2P/SiO2催化剂上仅为45.6%。说明Ni2P/HZSM-5-M催化剂的加氢活性显著高于Ni2P/SiO2催化剂。这是因为，与Ni2P/SiO2催化剂相比，在Ni2P/HZSM-5-M催化剂上形成了小颗粒的Ni2P活性相。同时，Ni2P/HZSM-5-M催化剂的活性具有良好的重复性。     

EPR Study of CO Adsorption onto CoZSM-5 Zeolite: Evidence for Spin Crossover upon Coordination and |z2, 2A1〉 Ground State

Adsorption of CO onto dehydrated cobalt-exchanged ZSM-5 zeolite was studied by CW-EPR techniques. It is shown that the reversible formation of a low spin carbonyl ¹{Co(CO) _n }⁷ adduct upon addition of carbon monoxide at p _CO>50–60 Torr involves significant change in the spin state of Co²⁺ from S=3/2 to 1/2. The spin Hamiltonian parameters of the adduct g _x =2.222, g _y =2.184, g _z =2.011, |A _x |=3.8 mT, |A _y |=3.2 mT, |A _z |=7.9 mT were determined by a computer simulation and further discussed in terms of the possible ground state and molecular structure. It is shown that the ¹{Co(CO) _n }⁷ cage complex exhibits a C_2v symmetry with |z ²,²A₁ ground state.