Catalytic activity of high-silicon TsVK and Y type zeolites

Conversion of paraffins on TsVK and Y zeolites follow a similar mechanism yielding the same intermediates. Low selectivity of Y zeolites with respect to aromatic hydrocarbons is attributed to the strong adsorption of these hydrocarbons on zeolites. It is assumed that the centers of strong adsorption are Al³⁺ ions in cationic positions in zeolite.

---

, . . , Al³⁺ .

     

Sequence of stages in the aromatization of ethylene on high-silicon zeolites

Conclusions Based on a study of the rate and selectivity of the reaction of aromatization of ethylene on high-silicon zeolite, the agreement of the experimentally observed distribution of the groups of products expected from the stoichiometry of the reaction was established for the temperature range studied.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1492–1497, July, 1986.     

Heats of adsorption of CO2 on high-silicon zeolites ZSM-5 and silicalite

The heat of adsorption of C0₂on NaZSM-5 at zero occupancy is 50.0 kJ/mole. The differential heats have two linearly descending segments, corresponding to the formation of two types of adsorption complexes with one or two C0₂ molecules, on the average. The heat of adsorption on silicalite coincides with the heat of adsorption of CO₂ on the noncationic segment of the NaZSM-5 zeolite structure (28–29 kJ/mole). The adsorbate-adsorbate interaction forces are not evident on the zeolites up to 1.5 mmole/g occupancy. The isotherms for the adsorption of C0₂ on zeolite NaZSM-5 and silicalite at 303 K in the occupancy region of 0–1.5 and 0–0.5 mmole/g are completely described by VMOT equations.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2636–2638, November, 1989.     

Contact ion-exchange interactions in systems involving zeolites

Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1505–1506, August, 1994.     

Synthesis of dimethyl sulfide in the presence of zeolites

In the presence of zeolites, dimethyl sulfide is produced either through CH₃OH interaction with H₂S or via CH₃SH decomposition. In accordance with their activities, in both reactions, zeolites arrange in the same sequence: HZSMHNaY>NaXNaY. Realization of the reaction CH₃OH+H₂S is more difficult compared to methanethiol decomposition.

---

CH₃OH H₂S CH₃SH. : HZSMHNaY>NaXNaY. CH₃OH+H₂S , .

     

核壳结构的Beta-Y复合分子筛的合成与表征

采用两种不同的水热晶化法合成Beta-Y复合分子筛,并采用XRD、SEM-EDS、FT-IR、N₂ 吸附-脱附技术对其进行表征。结果表明,以Beta分子筛为唯一硅源合成的sample A具有Y和Beta分子筛两种晶型结构,为机械混合形式;而以Beta分子筛母液为前躯体合成的sample B为核壳结构的复合分子筛,具有Y和Beta分子筛两种晶型结构,其核相为Beta分子筛,壳层为Y型分子筛,其晶体中具有介孔结构,并且介孔孔径比较集中。     

Synthesis and immobilization of quaternary ammonium cations in acidic zeolites

A general method for the synthesis of quaternary ammonium cations in acidic zeolites by a direct reaction of tertiary amines and alcohols is described.     

微孔分子筛主-客体复合体系及其电子转移过程

沸石分子筛是一类带有规则微孔结构的硅铝酸盐晶体,因其骨架具有独特的电子给受能力而备受关注．由此,许多以微孔分子筛为主体的电子转移体系被构建并深入研究．与溶液相中自由基的快速衰减不同,产生于微孔分子筛内部的自由基受其纳米孔道的限制,具有有限的迁移率和较长的寿命,有助于人们利用传统光谱技术确定反应机理．本文主要对当前微孔分子筛主-客体复合体系中的电子转移过程和机制的研究现状加以论述．     

FER型沸石的合成、结构与吸附性质

在TMEDA(四甲基乙基二胺)-Na2O-SiO2-Al2O3-H2O体系(I),Na2O-K2O-Al2O3-SiO2-H2O-HCO3^--CO3^2^-体系(II)及Py(吡啶)-PrNH2(正丙胺)-HF-SiO2-H2O体系(III)中, 分别合成了纯相FER沸石及FER硅沸石。用粉末XRD, FT-IR, 29Si MAS NMR及TG/DTA等表征其结构性质, 并用超微量电子真空吸附天平测定这些沸石样品对正己烷, 甲醇和水的吸附等温线。结果表明: 各体系合成的样品虽然结晶度高, 呈现出FER沸石的典型结构特征, 但由于它们的组成和晶格微结构不同, 热稳定性与吸附性质有明显的差异。在(I)体系中合成的FER沸石层错缺陷少, 晶格完美, 正己烷与甲醇的吸附量可达到理论值, 结构破坏温度为1190℃。红外精细谱及29Si MAS NMR高分辨谱证明FER硅沸石具有十分完美的骨架结构。由于晶胞收缩, 它对正己烷与甲醇吸附量略低于理论值, 并呈现出高度的疏水性。它的结构破坏温度高于1300℃。在(II)体系中合成的FER型沸石结构缺陷多, 沸石孔中的钾离子不易被质子完全交换。它的正己烷与甲醇吸附量均较低, 而水的吸附量相对较高。吸附现象表明, 正己烷和甲醇都被吸附于FER沸石的十元环主孔道中, 分压较高时, 甲醇可通过八元环进入小笼, 而水的吸附性质则主要与各样品的Si-OH缺陷及骨架中的阳离子含量有关。     

复合分子筛的合成及其在纤维素水解反应中的应用

采用水热晶化法制备了HUSY@MFI核壳结构复合分子筛。通过XRD、SEM、N_2吸附-脱附、NH_3-TPD及吡啶吸附红外等手段表征催化剂的结构和性质。结果表明,HUSY@MFI晶粒在形貌上呈椭球状,表面是鳞片状结构的MFI型分子筛,里面是光滑的HUSY型分子筛,焙烧模板剂前几乎没有或只有很少量的N_2能进入其孔道结构,致密的壳层MFI覆盖在HUSY型分子筛表面,形成了新的弱酸位,而中强酸强度和酸类型并没有受到影响,复合分子筛的表面酸量及总酸量减少。将所制备的HUSY@MFI复合分子筛催化剂应用于以离子液体1-乙基-3-甲基咪唑氯盐([Emim]Cl)为溶剂的纤维素水解反应中,与HUSY催化的纤维素水解相比,HUSY@M FI复合分子筛催化纤维素水解反应的速率较慢,葡萄糖收率由30.9%提高到41.3%。     

封装型Pt/SOD分子筛的合成及表征

基于封装型贵金属分子筛的合成,充分利用其择形性和氢溢流特性构建新型加氢催化剂,选定Pt作为活性组分,方钠石作为载体,通过水热合成法直接将金属前驱体Pt(NH_3)_4Cl_2引进SOD合成母液中进行晶化,合成了不同封装量的Pt/SOD分子筛。采用苯加氢反应测试样品的催化活性,并运用XRD、SEM、TEM和H_2-TPD对样品进行表征。结果表明,合成的不同封装量的Pt/SOD样品均具有良好的催化活性,与溢流氢受体HZSM-5间均具有良好的氢溢流效应。其中,当金属前驱体Pt(NH_3)_4Cl_2的用量为(Pt(NH_3)_4Cl_2)∶(Si-Algel)比为0.030 g/g时,所合成的Pt/SOD样品最佳,催化苯加氢反应的苯转化率可达54.38%。     

Synthesis and application of colloidal nanocrystals of the MFI-type zeolites

The colloidal dispersion containing the nanosized zeolites with the MFI topology has been successfully prepared. A pre-aging process of the mother gel at 80°C for 24 h before the crystallization was important for the formation of the nanosized zeolites. We have also found that silicalite-1 nanocrystals av. 62 nm in size were formed by the addition of acidic amino acids into the mother gel. The particle size of the zeolites can be controlled ranging from 62 to 530 nm by changing the amount of water, aging process, crystallization time and temperature and the addition of organic molecules. Furthermore, nanosized titanium silicalite-1 (TS-1) with the size of 50-130 nm has been successfully synthesized by the addition of a Ti source into the synthesis gel of the silicalite-1 nanocrystals. The nanosized TS-1 exhibits a higher catalytic activity in the epoxidation of cyclohexene than the microsized ones. Finally, we demonstrate the preparation of thin films of the silicalite-1 and TS-1 nanocrystals onto a silicon substrate by a dip-coating technique.     

Synthesis of ultra-high-silica ZSM-5 zeolites with tunable crystal sizes

Using silicalite-1 suspension as seed crystals and a small amount of tetraallkylammonium bromide as additional structure-directing agent, highly crystallized ZSM-5 with SiO₂/Al₂O₃ ratios higher than 100 was obtained. The crystal sizes could be easily tuned from tens of nanometers to about several micronmeters by merely adjusting the amount of the seeding suspension. Seeding suspension synthesized from different silica sources and the additional structure-directing agent may also affect the crystal sizes. The synthesized samples were characterized by powder X-ray diffraction, scanning electron microscopy, N₂ adsorption–desorption and inductively coupled plasma. When tetraethylammonuim bromide was used as additional structure-directing agent, crystals with silica-rich cores were observed, while additional nucleation could be found when tetrapropylammonium bromide was used as auxiliary template.     

Diffusion of p-xylene in single and binary systems in zeolites investigated by FTIR spectroscopy

A novel method based on Fourier transform infrared spectroscopy (FTIR) is applied to study sorption and sorption kinetics of p-xylene in ZSM-5-type zeolites as a single component and in a binary-component system, in the presence of benzene under conditions close to those of a catalytic run. From the change of intensities of IR bands characteristic for the adsorbates, diffusivities of p-xylene in the single-component system as well as in the binary-component system are determined at various temperatures and loadings. In comparison with benzene measured as a single component in the same system, the diffusivities of p-xylene are higher by a factor of 2 to 3. This is in agreement with the literature data. In the binary system, the presence of benzene reduces the diffusivities of p-xylene by 30 to 50%. Isotherms, isosteres and isosteric heats of adsorption are determined from the measurements. The isosteric heats of adsorption agree well with the literature data.     

高质量AlPO4-5分子筛单晶的螯合剂法合成与表征

考察了几种螯合剂对AlPO4-5分子筛单晶合成的影响，结果表明，用邻苯二酚，乙酰丙酮，水杨醛为螯合剂可以得到高质量的，尺寸较大的分子筛单晶，其作用机理可能与它们加入到分子筛合成体系中，改变了溶胶中铝的配位数或产生了铝的螯合物有关。     

同晶外延生长法合成MFI型核壳复合分子筛

采用二次热液结晶法,以四丙基氢氧化铵水溶液预处理过的低硅ZSM-5分子筛为晶核,通过调控p H值、水量和晶化时间等二次结晶条件,在晶核上外延生长了高硅ZSM-5壳,制备了MFI/MFI核壳型复合分子筛。通过X射线衍射、扫描电镜、能量色散谱仪、透射电子显微镜、N2吸附-脱附和NH3-程序升温脱附等手段表征了所合成的核壳分子筛的晶体结构、表面形态及核/壳界面,并对它们的结构参数以及酸性进行了初步评估。结果表明,核壳复合分子筛的壳层由多层200 nm的MFI沸石晶粒组成;高硅ZSM-5分子筛壳层的生成,引入了介孔结构,显著增大了外比表面积;同时,核壳结构的形成降低了复合分子筛酸性和外表面的酸密度,但增加了弱酸量。当二次晶化母液p H值为8.5,H2O/SO2物质的量比为30,晶化时间为24 h时,高硅分子筛壳层更易可控生长。     

Faujasite-type zeolites modified with iron perfluorophthalocyanines: Synthesis and characterization

The synthesis and characterization of hexadeca- or perfluorophthalocyanine complexes of iron(II) (FeF₁₆Pc) in synthetic faujasite-type zeolites is reported. The encapsulation of FeF₁₆Pc in NaY zeolite by the template synthesis method as well as the synthesis of NaX around FeF₁₆Pc are discussed. A spectroscopic (UV—VIS, IR) and electrochemical analysis of the modified zeolites, providing evidence for encapsulation, is presented and compared with the unsubstituted FePc complex.