AlMCM-41负载Ni催化剂的正十二烷加氢转化反应性能研究

采用N_2脱附、XRD，NH_3-TPD和H_2-TPR等手段表征中孔分子筛AlMCM-41负载 Ni催化剂。结果表明，AlMCM-41负载Ni后会导致中孔分子筛骨架部分塌陷，孔道有 序度降低，而且，Ni与载体的相互作用随着载体中铝含量的增加而增强。此外，催 化剂的表面酸性以弱酸和中强酸为主。正十二烷加氢转化反应评价表明，在催化剂 Si/Al比为17.4 ～ 38.7范围内，随着铝含量的减少，氢解副反应加剧，正十烷的 转化率逐渐升高，异构选择率则以先增加后减小的趋势变化，在Si/Al=23.2时达到 最大值。当Si/Al比为17.4时，催化剂的酸/金属功能呈现较好的匹配，正十二烷裂 解产物以C_6为中心呈对称分布且i/n-(C_4～C_9)比例较高。     

Characterization of Ni／AlMCM-41 Catalysts and Their Catalytic Performance in n-Dodecane Hydroconversion

A series of Ni/AIMCM-41 catalysts with different nickel contents was prepared via the incipient wetness impregnation method. The effects of the nickel content on the structure, acidity and metal function of the catalysts were studied by using different techniques. In the test of n-dodecane hydroconversion, it was found that the metal and acid functions were well balanced over a 2.0%Ni (mass fraction)/AIMCM-41 catalyst, which gave the maximal isomerization selectivity and a homolytic cleavage products.     

Thermal stability of food additives of glutamate and benzoate type

Summary An unsaturated polyester/sisal flame retardant composite was formulated using decabromine diphenyl oxide associated with antimony trioxide as additives. The development and use of natural or vegetable fiber reinforced composites is increasing worldwide, since natural fibers come from renewable sources and their use contributes to the so-called 'green technology'. In the present study, the synergic effect of a bromine/antimony (3:1 molar ratio) based flame retardant system with 7.5% Br (mass/mass) added to composites investigated by TG, UL-94V and pyrolysis on a coupled Pyr-GC/MS device. The efficiency of the flame retardant system is confirmed by TG and UL-94V test where the composite containig flame retardant system obtained the highest classification (V-0).     

Esterification of Glycerol by Oleic Acid and Selective Hydrogenation of Oleic Acid Methylester Over Acid and Ru-Sn-B Supported Mesoporous AlMCM-41

Demand for large pore size molecular sieves has given rise to great interests in a new family of silica-based mesoporous materials designated as M41s, which expand typical molecular sieves into an extra-large pore range and generate the potential for the applications of these materials in catalysis and sorption for very bulky molecules1-6. MCM-41 possesses a hexagonal arrangement of uniform mesopore ranging from 15 to 100 ? and can be prepared with varied Si/Al ratios. The investigations of …     

Kinetic study of template removal of MCM-41 nanostructured material

The siliceous MCM-41 molecular sieve was synthesized starting from a hydrogel with the following molar composition: 4.58SiO₂:0.437Na₂O:1CTMABr:200H₂O. The cetyltetramethylammonium bromide (CTMABr) was used as structure template. A kinetic study of template removal after the syntheses was performed by Vyazovkin model-free kinetic method obtaining apparent activation energy of 166±8.2 kJ mol^-1. This revised version was published online in August 2006 with corrections to the Cover Date.     

AlMCM-41负载Ni催化剂的正十二烷加氢转化反应性能研究

采用N_2脱附、XRD，NH_3-TPD和H_2-TPR等手段表征中孔分子筛AlMCM-41负载 Ni催化剂。结果表明，AlMCM-41负载Ni后会导致中孔分子筛骨架部分塌陷，孔道有 序度降低，而且，Ni与载体的相互作用随着载体中铝含量的增加而增强。此外，催 化剂的表面酸性以弱酸和中强酸为主。正十二烷加氢转化反应评价表明，在催化剂 Si/Al比为17.4 ～ 38.7范围内，随着铝含量的减少，氢解副反应加剧，正十烷的 转化率逐渐升高，异构选择率则以先增加后减小的趋势变化，在Si/Al=23.2时达到 最大值。当Si/Al比为17.4时，催化剂的酸/金属功能呈现较好的匹配，正十二烷裂 解产物以C_6为中心呈对称分布且i/n-(C_4～C_9)比例较高。     

HZSM-5型分子筛硅铝比对一步法合成二甲醚的影响

以Cu/Zn/Al(摩尔比为6∶3∶1)甲醇合成催化剂与HZSM-5型分子筛混合,制备了一步法二甲醚合成催化剂。通过改用三种不同Si/Al摩尔比（摩尔比为25、38和50）的HZSM-5型分子筛,考察了催化剂中脱水组分（HZSM-5分子筛）的酸性对二甲醚合成的影响。结果表明,随着催化剂Si/Al摩尔比的降低,分子筛的酸性增强,使得CO单程转化率提高。当催化剂Si/Al＝38时,CO对二甲醚的选择性最高,可达到68.13％,其次是催化剂Si/Al＝50,选择性最差的是Si/Al＝25的催化剂。在553 K、 3 MPa和4 000 h－1的条件下,Si/Al＝25和Si/Al＝38的催化剂CO单程转化率和DME的选择性接近一致。在此条件下,两者的时空产率达到试验的最大值,分别为0.38 gDME/(gcat·h)和0.36 gDME/(gcat·h),在试验范围内,一步法合成二甲醚催化剂最佳的Si/Al摩尔比为25。     

以CTMABr和CTMAOH为共模板剂合成MCM-41

采用共模板剂水热合成了MCM-41.分别用X射线粉末衍射(XRD)、固体核磁共振(²⁷AlMASNMR)和N₂吸附等温线技术考察了用该方法和传统方法所制备的Si-MCM-41和Al-MCM-41样品的晶相结构、孔结构以及Al在分子筛中的化学环境.结果表明,用共模板剂方法合成的MCM-41样品,其纯度和孔径均一性显著提高,特别是当样品中Al含量较高时,仍可保证Al原子以四配位结合在MCM-41的硅骨架上.还就采用共模板剂的理论依据进行了讨论.     

5,10,15,20-四羟基苯基卟啉醋酸钴在Si-MCM-41中瓶中造船法组装及表征

用瓶中造船法将5,10,15,20-四羟基苯基卟啉醋酸钴组装在Si-MCM-41中.通过ICP元素分析、DTA差热分析及XRD、EPR、XPS、UV-Vis光谱等对组装前后样品的含量、热稳定性、醋酸钴与5,10,15,20-四羟基苯基卟啉的配位情况、钴卟啉配合物在分子筛中的水热稳定性进行了研究.结果表明,醋酸钴与5,10,15,20-四羟基苯基卟啉完全能在Si-MCM-41中进行配位,配合物在Si-MCM-41中具有良好的水热稳定性及热稳定性.     

不锈钢金属网支撑的X型沸石膜的制备与表征

以不锈钢金属网为载体, 采用预涂晶种的二次生长法, 在水热条件下制备了连续、无明显缺陷的X型分子筛膜. 考察了反应物中水的含量、碱度、硅铝比和反应时间等制备条件对形成X型分子筛膜的影响, 优化了X型分子筛膜的制备条件, 利用扫描电子显微镜(SEM)对不同反应条件下制备的X型分子筛膜的形貌进行了观察, 并对结果进行了分析.     

Studies on the Surface Properties of MCM-41

IntroductionMCM- 41 ,a member of the M41 S family ofmesoporous silicate/ aluminosilicates,possesses aone dimensional structure[1] with hexagonallyarranged uniform pores.The unique structuralcharacteristics of this material,such as its largeBET surface area,high porosity,and controllablepore size with a narrow distribution suggest thatMCM- 41 may be full of promise as a catalyst[2 ] ,catalyst support[3 ] or as a host for host- guestencapsulation[4] .MCM- 41 has therefore attracted agreat d…     

Kinetic parameters determination in non-isothermal conditions for the crystallisation of a silica-soda-lead glass

Two integral isoconversional methods (Flynn–Wall–Ozawa and Kissinger–Akahira–Sunose) and the invariant kinetic parameters method (IKP) were used in order to examine the kinetics of the non-isothermal crystallisation of a silica-soda-lead glass. The objective of the paper is to show the usefulness of the IKP method to determine both the activation parameters and the kinetic model of the investigated process. Thismethod associated with the criterion of coincidence of kinetic parameters for all heating rates and some procedures of the evaluation of the parameter from Johnson–Mehl–Avrami–Erofeev–Kolmogorov (JMAEK) equation led us to the following kinetic triplet: activation energy, E=170.5±2.5 kJ mol^–1 , pre-exponential factor, A=1.178±0.350·10 10 min^–1 and JMAEK model (A _m) m=1.5.     

不同Si/Al比对Mo/ZSM-5催化性能的影响

采用浸渍法在不同Si／Al比的HZSM-5上制备了3种MoO3含量相同的Mo／ZSM-5样品，并在相同的实验条件下对其进行了活性测试，同时运用XRD、XPS、NO—TPD等技术分别对催化剂的体相和表面结构进行了表征．实验结果表明，Si／Al比对Mo／ZSM-5上NO的选择性催化还原性能有明显的影响，Si／Al比为28的1#样品其转化率在530℃达到94％以上，而Si／Al比较大的2#和3#样品最高转化率只有48％和41％．对3种Mo／ZSM-5样品的XRD表征只发现有HZSM-5和MoO3两种物相存在，分子筛骨架差异不大；而XPS表征却发现1#样品的表面M03d5／2含量远大于2#和3#样品，并且有Mo^4 和(或)Mo＼ 5 存在，表明3种样品的表面性质存在很大差异．在3种样品中，1#样品具有最大的NO吸附能力，这与表面特性差异相吻合．     

Controlled release of Ibuprofen from dealuminated faujasites

Four dealuminated faujasite samples have been employed as matrices for Ibuprofen adsorption and in vitro drug delivery with the aim of adapting the pore size to the size of the drug molecule and to study the influence of Al content upon the drug delivery. Ca. 15 wt% of Ibuprofen is adsorbed in the zeolite cavities. FTIR shows that the zeolite hydroxyl groups interact with Ibuprofen and, in addition, carboxylate species bonded to extraframework Al species are detected in the most dealuminated samples. Two stages are observed in the Ibuprofen delivery. In the first hours, the release is governed by a diffusion process, showing a similar delivery rate independently of the Al content. However, after this stage, the Al content is determinant in drug delivery, being the release faster when the framework Si/Al ratio increases up to 22, and then decreases for Si/Al=62. The behaviour of the highly dealuminated material is probably due to the predominance of Van der Waals interaction between the drug and the siliceous zeolite framework.     

An overview of studies on the highly dispersed uranium oxide species occluded within mesoporous MCM-41 and MCM-48 host materials

In this article we have consolidated our recent studies on anchoring of uranyl groups and encapsulation of highly dispersed nano-particles of -U₃O₈ in mesoporous MCM samples. The size of uranium oxide crystallites and the binding of uranyl groups at framework sites of host matrix depended on the preparation method, viz. wet impregnation, exchange of template cations, and the hydrothermal route. These uranium species contributed individually to the catalytic oxidation of organic molecules, such as methanol, toluene and benzyl alcohol; the uranyl groups playing a more important role at lower reaction temperatures. Also, the size and the lattice oxygen of uranium oxide crystallites played a vital role, not only in the lowering of reaction onset temperature but also in deciding the nature and the reactivity of the transient surface species formed during the oxidation of above mentioned organics. For instance, the results of in situ IR spectroscopy experiments have shown that while larger-size U₃O₈ crystallites help in the growth of certain oxymethylene (–OCH₂) and polymerized oxymethylene (–OCH₂)_n species, adsorption of methanol on smaller size particles helped in the additional formation of formate-type complexes. Thus, a relationship was found between the size of uranium oxide crystallites, the nature of the transient species formed and the catalytic conversion of methanol to form CO₂, CO and methane. In addition, the uranyl ions anchored within the pore system of host matrix are found to serve as efficient heterogeneous photocatalysts for the sunlight-assisted deep oxidation of organic molecules in the vapor phase and at room temperature. The reaction mechanisms, accounting for the catalytic properties of occluded UO_x species without and in the presence of radiation, are discussed in the light of the above mentioned results.     

2D versus 3D MFI zeolite: The effect of Si/Al ratio on the accessibility of acid sites and catalytic performance

Through the synthesis of 2D MFI zeolite samples of Si/Al ratio ranged from 13 to 74 with inter-crystalline mesoporosity and their reference 3D counterparts, we have systematically studied and revealed the impact of Si/Al ratio on the inter-dependence of core intrinsic properties of structural porosity and acidity. It is apparent that mesopores in the 2D MFI zeolite play a critical role, dictating the accessibility and distribution of specific acid sites. It was found that, compared to their 3D counterparts, the 2D samples possess a three-times larger accessible surface area owing to the mesopores. Although having a slightly lower total number of acid sites, the 2D samples enjoy a higher percentage of accessible strong acid sites and weak Lewis acid sites. Consequently, in three selected liquid phase reactions, which had different acidity demands and molecular diffusion constraints, the 2D samples demonstrated much higher catalytic activities and resistance to deactivation. This study has, for the first time, established the relationship between Si/Al ratio and acidity for the 2D MFI zeolite, thus enabling rational selection of a Si/Al ratio for a targeted application.     

Al-MCM-48中Al含量对高密度聚乙烯催化裂解的影响

本文用常温合成方法合成了不同硅铝比的Al-MCM-48,并研究了硅铝比不同对Al-MCM-48催化裂解高密度聚乙烯(HDPE)的影响.发现Al-MCM-48存在的催化裂解可以提高HDPE的转化率和液体收率;硅铝比的变化对转化率和液体收率有较明显的影响,转化率和液体收率随硅铝比的增加而增加,当硅铝比达到100时达最大值,然后液体收率和转化率开始逐步下降;液体产物中的烯烃的含量随硅铝比的增加而增加;重复实验表明Al-MCM-48具有较好的稳定性,不易结焦.     

微波辐射法合成SAPO-5分子筛中硅铝比对产物结晶度和甲苯吸附性能的影响

采用硅溶胶作硅源, 用微波辐射法在酸性条件下(pH=4.5-5.0)合成了SAPO-5分子筛, 利用X射线衍射(XRD), 傅立叶变换红外光谱(FT-IR), 扫描电镜(SEM)和Brunauer-Emmett-Teller (BET)比表面积分析对样品的结晶度、形貌和比表面等进行表征, 考察了晶化原料硅铝比对分子筛结晶度和晶体颗粒长径比(c/a)的影响, 测定了分子筛对甲苯的吸附性能. 结果显示, 采用微波辐射法合成的SAPO-5分子筛, 在硅铝摩尔比为0.50附近生成产物的结晶度最好, 晶体颗粒的长径比最小(约为1.0). 尽管不同硅铝比条件下得到的样品比表面测定结果变化不大, 但对甲苯的吸附实验显示, 在硅铝比为0.50时样品的吸附速率和饱和吸附量均达到了最大值. 这与表征所得的结晶度和长径比的变化一致, 即结晶度好,长径比小的SAPO-5分子筛具有更好的甲苯吸附性能.     

Solid-state NMR spectra of paramagnetic silica-based materials: observation of 29Si and 27Al nuclei in the first coordination spheres of manganese ions

Some silica-based solids, prepared by the sol/gel method in the presence of high Mn2+ concentrations, have been characterized by the 29Si, 27Al MAS NMR spectra and 29Si T1 measurements. The single-pulse 29Si and 27Al MAS NMR spectra have shown broad spinning sideband patterns that are interpreted in terms of anisotropic bulky magnetic susceptibility (BMS) and dipole-field effects. In the absence of paramagnetic isotropic shifts, the 29Si and 27Al nuclei observed in the single-pulse NMR spectra have been assigned to nuclei remote from paramagnetic centers. It has been demonstrated that the 29Si and 27Al nuclei, which are in the vicinity of the manganese ions, can be detected by the Hahn-echo MAS NMR experiments at different carrier frequencies.     

硅铝比对完全液相法制备的一步法二甲醚合成催化剂反应性能的影响

采用完全液相法制备了不同Si/Al摩尔比的浆状一步法二甲醚合成催化荆,在搅拌式反应釜中对其催化性能进行了评价.通过XRD,NH3-TPD-MS,H2-TPR和XPS等方法表征了催化剂的体相结构和表面性质.结果表明,完全液相法制备的CuZnSiAl催化剂在反应前其活性组分Cu主要以低价态存在,Cu晶粒大小是影响其活性的主...