紫外拉曼光谱研究FeAlPO_4-5分子筛的合成机理

利用紫外共振拉曼光谱和紫外-可见漫反射光谱对不同铁含量的 FeAlPO4-5 分子筛进行了研究. 结果表明, FeAlPO4-5 分子筛的骨架铁有 4 个特征的拉曼谱峰, 分别位于 630, 1060, 1140 和 1210 cm?1. 当凝胶中 Al/Fe 比小于 380 时, 只有一部分铁离子可以进入分子筛形成四配位的骨架铁物种; 而另一部分则以骨架外六配位的铁物种存在, 其特征拉曼谱峰位于 285 cm?1. 结合紫外拉曼光谱、紫外-可见漫反射光谱和 X 射线衍射研究了 Al/Fe 比为 760 时 FeAlPO4-5 分子筛的晶化过程. 结果发现, 在分子筛晶化前, 铁物种以六配位的形式存在, 它为分子筛前体中的一维链状磷酸铝添加了一个惰性端基, 六配位的 Fe-O 键不利于它与其它磷酸铝物种发生反应; 当分子筛开始晶化时, 带有铁离子端基的磷酸铝链与其它磷酸铝链进一步反应形成分子筛骨架. 同时, 六配位的铁离子和邻近的磷酸铝物种反应转化为四配位的骨架铁物种.     

AM-6分子筛的快速合成及原子线形成机理研究

报道了一种4 h快速合成AM-6分子筛的方法,考察了凝胶中K+含量和起始凝胶碱度对AM-6分子筛纯度以及晶化度的影响.结果表明,向合成体系中引入适量K+可以抑制杂相的生成,在n(K+)/n(V4+)=3和pH=12.5条件下,制备的样品为纯相且晶化度最高.结合紫外-可见吸收光谱和紫外拉曼光谱研究了AM-6分子筛的形成过...     

晶种导向下干胶法合成ZSM-5分子筛

以廉价水玻璃为硅源,在晶种替代有机模板剂的条件下采用干胶法合成了ZSM-5分子筛。利用XRD、SEM、TEM、FTIR、N_2吸附-脱附和NH_3-TPD等分析方法对合成样品进行了表征和测试,考察了合成条件对ZSM-5分子筛晶化过程的影响。结果表明,在硅铝比(n/n)为30~70,钠硅比(n/n)为0.12~0.20时都可以得到结晶度良好的ZSM-5分子筛。研究发现,干胶法合成ZSM-5,在不引入外加水的情况下也可以得到ZSM-5样品,外加水的引入能够有效地提高晶化速率;与水热法合成ZSM-5分子筛相比,干胶法可以显著地缩短晶化时间,同时,合成样品的晶体尺寸也有所减小。     

以一种新型Gemini表面活性剂作为介孔模板剂通过转晶过程合成介孔ZSM-5分子筛

将一种新型Gemini表面活性剂,丙撑基双(十八烷基二甲基氯化铵)[C18H37(CH3)2–N+–(CH2)3–N+–(CH3)2C18H37]Cl2(C18-3-18),作为介孔模板剂用于水热法合成介孔ZSM-5分子筛.结果表明,在130 oC低温晶化即可高效合成介孔ZSM-5分子刷.C18-3-18的加入量可影响到所合成介孔ZSM-5分子筛的相对结晶度和织构性质,它的形成遵从一个转晶过程.在合成初期,凝胶中介孔模板剂C18-3-18的使用导向了介孔材料的生成;随后在TPABr的模板作用下,介孔材料慢慢转晶生成具有MFI结构的介孔ZSM-5;然后所合成的介孔ZSM-5晶粒进一步长大并聚集形成块状颗粒,同时产生晶间介孔.C18-3-18作为介孔导向剂不仅可用于合成介孔ZSM-5分子筛,也可用于其它介孔分子筛的合成中.     

晶种导向下干胶法合成ZSM-5分子筛

以廉价水玻璃为硅源,在晶种替代有机模板剂的条件下采用干胶法合成了ZSM-5分子筛。利用XRD、SEM、TEM、FTIR、N₂吸附-脱附和NH₃-TPD等分析方法对合成样品进行了表征和测试,考察了合成条件对ZSM-5分子筛晶化过程的影响。结果表明,在硅铝比（n/n）为30~70,钠硅比（n/n）为0.12~0.20时都可以得到结晶度良好的ZSM-5分子筛。研究发现,干胶法合成ZSM-5,在不引入外加水的情况下也可以得到ZSM-5样品,外加水的引入能够有效地提高晶化速率;与水热法合成ZSM-5分子筛相比,干胶法可以显著地缩短晶化时间,同时,合成样品的晶体尺寸也有所减小。     

低成本原料一步直接合成小晶粒ZSM-5分子筛

以硫酸铝、水玻璃、正丁胺、水、晶种、NaCl、浓硫酸等低成本试剂为原料,一步直接合成法制备了高结晶度小晶粒ZSM-5分子筛,详细考察了凝胶陈化方式、滴加顺序、晶化时间、晶化温度、水量及原料硅铝比对分子筛结晶度及粒度的影响.通过XRD、SEM等对合成的分子筛进行了详细表征.研究结果表明:采用低温水浴回流搅拌陈化方式、在160～170℃、晶化30 h可获得高结晶度小晶粒ZSM-5分子筛.正反加顺序对分子筛结晶度影响不大.     

在含乙醇的硅铝凝胶中合成ZSM-5沸石

用含乙醇的硅铝凝胶水热晶化合成ZSM-5沸石.实验表明,乙醇能够促进ZSM-5沸石晶体的成核和生长,具有明显的模板剂作用.向含乙醇的凝胶中加入晶种可以进一步缩短晶化诱导期和晶化时间,并减小分子筛的晶粒度.晶种的粒度与分子筛产物的晶粒度有一定对应关系.采用搅拌晶化也能明显地减小ZSM-5沸石的晶粒度,同时影响晶体形貌.通过优化晶化条件和凝胶组成,成功合成出硅铝比在30～240范围内、结晶度较高的ZSM-5沸石分子筛,所得沸石孔道畅通,热稳定性、水热稳定性高,且具有较强酸性,具有良好的应用前景.     

混合胺体系中 MCM-49/ZSM-35 复合分子筛的晶化过程

 采用 X 射线衍射、N2 吸附-脱附、扫描电镜和傅里叶变换红外光谱等技术, 研究了 MCM-49/ZSM-35 复合分子筛在 Na2O-SiO2-Al2O3-CHA (环己胺)-HMI (六亚甲基亚胺)-H2O 合成体系中, 先在低温 80 ?C 老化 4 h, 再经 160 ?C 晶化不同时间的演变过程. 结果表明, 在该混合胺体系中, 首先生成 MCM-49 分子筛, 随着晶化时间的延长, 形成 ZSM-35 含量逐渐增加的 MCM-49/ZSM-35 复合分子筛, 最后生成纯 ZSM-35 分子筛; ZSM-35 的生成是以 MCM-49 分子筛的消耗为代价的.     

ZSM-5分子筛结晶度及晶粒大小的影响因素

以硅溶胶为硅源,偏铝酸钠为铝源,用晶种法制备ZSM-5分子筛.考察了物料混合方式、陈化时间、晶化时间、晶化温度、碱度和水量等对ZSM-5分子筛相对结晶度和晶粒大小的影响.用X射线衍射仪(XRD)、扫描电子显微镜(SEM)和激光粒度分析等对所合成样品进行了表征.结果表明:在一定的高碱度条件下形成高浓度的硅铝酸盐凝胶,才能合成出晶化良好的样品,ZSM-5分子筛是按固相机理形成的;合成ZSM-5分子筛的相对结晶度和平均颗粒度均随晶化温度的升高及硅铝酸盐凝胶浓度的增加而增大,在室温陈化24 h、180℃晶化12～24 h时相对结晶度最高,平均颗粒度基本上与陈化时间无关.     

异相晶种诱导快速合成低硅菱沸石分子筛

在不含有机模板剂体系(OSDAs)中,利用异相晶种(T型分子筛)诱导快速合成出纯相的低硅菱沸石分子筛。采用XRD、SEM、TEM、27Al MAS NMR和紫外拉曼等手段表征分子筛的结构属性和形貌特点。详细研究了菱沸石分子筛的晶化过程以及晶种添加量、nAl2O3/nSi O2、nH2O/nSiO2和碱度对菱沸石分子筛晶化的影响,并探讨T型分子筛晶种诱导合成菱沸石分子筛的晶化机理。原位合成体系中仅形成L型分子筛晶相,而一定量T型分子筛异相晶种的加入诱导溶胶快速制备出纯相的菱沸石分子筛。T型分子筛晶体在一定的水热条件下不断溶解而释放的六元环(6R)和四元环(4R)迅速形成菱沸石分子筛特征笼(CHA笼),抑制了L型分子筛特征单元和特征笼(不含四元环的CAN笼)的形成。     

Studies on the Synthesis, Properties andPreparation Methods of Zeolite ZK-4

IntroductionIn 1961 Kerr et al. LI] first synthesized a new zeolite designated ZK-4 whose crystal structure is similar to that of zeolite A, but whose chemical composition differs significantly fromthat of zeolite A. Like zeolite A, ZK-4 contains 24 tetrahedra in a cubic unit cell. However,zeolite ZK--4 has a ratio of silicon to aluminium greater than 1. 0. This increases the siliconcontent of the new zeolite, resulting in smaller unit cell parameters than those of zeolite A.Because the …     

Preparation, crystal structure, and thermal stability of the cadmium sulfide nanoclusters Cd6S44+ and Cd2Na2S4+in the sodalite cavities of zeolite A (LTA)

The crystal structure and thermal stability of two cadmium sulfide nanoclusters prepared in zeolite A (LTA) have been studied by XPS, TGA, and single-crystal and powder XRD. The crystal structures of Cd2.4Na3.2(Cd6S4)0.4(Cd2Na2S)0.6(H2O)> or =5.8[Si12Al12O48]-LTA (a = 12.2919(7) A, crystal 1 (hydrated)) and /Cd4Na2(Cd2O)(Na2O)/[Si12Al12O48]-LTA (a = 12.2617(4) A, crystal 2 (dehydrated)) were determined by single-crystal methods in the cubic space group Pm3m at 294(1) K. Crystal 1 was prepared by ion exchange of Na12-LTA in an aqueous stream 0.05 M in Cd2+, followed by washing in a stream of water, followed by reaction in an aqueous stream 0.05 M in Na2S. Crystal 2 was made by dehydrating crystal 1 at 623 K and 1 x 10(-6) Torr for 3 days. In crystal 1, Cd6S4(4+) nanoclusters were found in and extending out of about 40% of the sodalite cavities. Central to each Cd6S4(4+) cluster is a Cd4S4 unit (interpenetrating Cd2+ and S2- tetrahedra with near Td symmetry, Cd-S = 2.997(24) A, Cd-S-Cd = 113.8(12) degrees, and S-Cd-S = 58.1(24) degrees). Each of the two remaining Cd2+ ions bonds radially through a 6-ring of the zeolite framework to a sulfide ion of this Cd4S4 unit (Cd-S = 2.90(8) A). In each of the remaining 60% of the sodalite cavities of crystal 1, a planar Cd2Na2S4+ cluster was found (Cd-S/Na-S = 2.35(5)/2.56(14) A and Cd-S-Cd/Na-S-Na = 122(5)/92(7) degrees). Cd6S4(4+) and Cd2Na2S4+ are stable within the zeolite up to about 700 K in air. Upon vacuum dehydration at 623 K, all sulfur was lost (crystal 2). Instead as anions, only two oxide ions remain per sodalite unit. One bridges between two Cd2+ ions (Cd2O2+, Cd-O = 2.28(3) A) and the other between two Na+ ions (Na2O, Na-O = 2.21(10) A).     

Y沸石水热转晶为ECR-1沸石的研究

ECR-1具有十二元孔道, 其通常是在有机模板存在下合成的, 我们曾报道了在无有机模板剂的条件下合成沸石ECR-1, 本文报道在无有机模板剂存在的条件下Y沸石水热转晶为沸石ECR-1的研究结果. 因为Y沸石具有合成简单、价格低廉和不使用有机模板等特点, 所以对由Y沸石转晶为ECR-1的研究, 对其在工业上的应用具有重要意义.     

Effects of ammonium exchange and Si/Al ratio on the conversion of methanol to propylene over a novel and large partical size ZSM-5

One type of ZSM-5 zeolite with large partical size was prepared and characterized by XRD, SEM, N2 adsorption-desorption, XRF, Py-IR and NH3-TPD techniques. Effects of ammonium exchange and SiO2/Al2O3 molar ratios on the reaction of methanol to propylene (MTP) over Na-ZSM-5 and H-ZSM-5 zeolites have been studied in a fixed-bed flow reactor under the operating conditions of T = 500 °C, P = 1 atm, and WHSV = 6 h-1. Ammonium exchange led to a rapid decrease in Na content for Na-ZSM-5 zeolite. The reaction results indicated that Na-ZSM-5 and H-ZSM-5 with different SiO2/Al2O3 molar ratios all exhibited high activity for methanol conversion. Ammonium exchange and the decreased SiO2/Al2O3 molar ratio of ZSM-5 zeolite led to an increase both in strong acid sites and weak acid sites. Na-ZSM-5 with high SiO2/Al2O3 molar ratio was favorable for the formation of propylene. The highest propylene selectivity (45.9%) was obtained over Na-ZSM-5 zeolite catalyst with SiO2/Al2O3 molar ratio of 220.     

超低硅铝比多级孔ZSM-5分子筛的无模板剂合成

以水玻璃为硅源、Al₂(SO₄)₃·18H₂O为铝源,投料硅铝比SAR=n(SiO₂)/n(Al₂O₃)=40,前躯体凝胶pH=11.2、Na₂O/SiO₂=0.18、 H₂O/SiO₂=43、m(晶种)/m(SiO₂)=0.16,不添加任何模板剂条件下合成了具有多级孔结构的超低硅铝比ZSM 5分子筛,其结构经²⁷Al NMR, SEM-EDS, Py-IR, NH₃-TPD, XRD和N₂-吸脱附表征。SEM结果表明ZSM-5分子筛晶体为侧面呈“维管束”状的长方体;EDS分析表明其表面硅铝分布具有显著不均一性：顶底表面SAR=20,侧面SAR=13。NH₃-TPD分析表明：该ZSM-5分子筛整体具备可观的弱酸总酸量(1.9 mmol·g^-1),且以Lewis酸为主。N₂吸脱附实验表明：ZSM-5分子筛存在明显的介孔结构,属同时含有微孔-介孔结构的多级孔、超低硅铝比ZSM-5分子筛。     

Synthesis of high-silica EU-1 zeolite in the presence of hexamethonium ions: a seeded approach for inhibiting ZSM-48

A seeded approach was developed to synthesize high-silica EU-1 zeolite via inhibiting the co-crystallization of ZSM-48 in the presence of hexamethonium (HM) ions. A systematic study was carried out to determine factors such as seed content and SiO(2)/Al(2)O(3) ratio, which influenced the crystallization of high-silica EU-1 and transformation of EU-1 into ZSM-48. Using EU-1 seeds, not only well-crystallized pure EU-1 zeolites with SiO(2)/Al(2)O(3) ratios more than 500 were synthesized, but also the co-crystalline of ZSM-48/EU-1 or pure ZSM-48 was obtained in control from silica-rich mixture gels. Furthermore, the kinetic features of the seeded synthesis of EU-1 zeolites with SiO(2)/Al(2)O(3) ratios of 55, 190, and 500 were examined. It was found that seeds played crucial roles in the decrease of apparent activation energy of EU-1 nucleation and inhibiting the transformation of EU-1 into ZSM-48. The HM and Al species performed synergistic roles to inhibit the formation ZSM-48 during high-silica EU-1 nucleation and crystal growth.     

EFFECTS OF SYNTHESIS PARAMETERS ON ZEOLITE ZSM-48 IN A SOLID REACTION MIXTURE SYSTEM

IntroduCtionReCently,zcoliteZSM-48hasbeenspehesizedinapurelysolidsystemll1.Thismethedusedtosynthesizezcolitescangndlyincreasetheyieldofpnductsperunitvolume,simplifythepr0cedresanddecreasethecnvironmentalpolluti0n.ThisincreasestheacualPOssibilityofsynthesisofhigh-silicazcolitesinchemicalindustry.MoreOver,itisalsohelpfulforstUdyingthezeolitecrystalliZai0nmechanism.ItiswellknownthatthesamewneofzeolitessynthesizedindifferentsystemshasdifferentcatalyticpropertiesduetothechangesoftheirfinestruC…     

沸石合成过程中的溶剂效应

沸石合成过程中的溶剂效应窦涛，冯芳霞，王晓钟，萧墉壮，曹景慧（太原工业大学精细化工研究所，太原０３００２４）刘建宇钟炳（山西省化工设计院，太原０３００２４）（中国科学院山西煤炭化学研究所，太原０３０００１）关键词ＺＳＭ－５，ＺＳＭ－３５，方钠石，溶剂...     

低硅铝比ZSM-5分子筛上C4烃的催化裂解反应

以低硅铝比(n(SiO2)/n(Al2O3)=20-45)的ZSM-5分子筛为催化剂, 研究了混合C4烃的催化裂解反应, 并对不同硅铝比的ZSM-5分子筛进行了酸性表征. 混合C4烃的催化裂解反应结果表明, 低硅铝比的ZSM-5分子筛具有较高的低温催化活性, 高硅铝比ZSM-5分子筛催化剂上乙烯和丙烯的收率高于低硅铝比ZSM-5分子筛催化剂, 低硅铝比ZSM-5分子筛上苯和甲苯的收率高于高硅铝比ZSM-5分子筛催化剂. 在反应温度为625 ℃时, 硅铝比为20的ZSM-5分子筛催化剂上乙烯、丙烯、苯和甲苯的总收率可达79.42%. 酸性表征结果表明, 硅铝比低的ZSM-5分子筛具有更多的Bronsted(B)酸酸量、Lewis(L)酸酸量及总酸酸量, 这是低硅铝比ZSM-5分子筛具有低温高活性及高的苯和甲苯收率的原因.