Synthesis and Characterization of the Large Pore Molecular Sieves VPI-5 and Si-VPI-5

The large pore molecular sieves VPI-5 and Si VPI-5 were synthesized by using three organic amines (dipropylamine, diisopropylamine and dipentylamine) as the structure-directing agents. Compared with general alumlnophosphate molecular sieves, the synthesis of the molecular sieves of VPI-5 type ls of many unique features. Both VPI-5 and Si-VPI-5 were characterized by XRD, IR, TG-DTA, and MAS-NMR.     

影响水热合成VPI-5及Si-VPI-5的因素

使用二正丙胺(DPA)和二正丁胺(DBA)作结构导向剂合成出VPI-5和Si-VPI-5,并以二异丙胺(DIPA)为结构导向剂成功地合成出高结晶度的超大孔磷酸铝分子筛VPI-5,其XRD谱图中未检测出其他杂质峰.VPI-5分子筛不同于一般中微孔磷酸铝分子筛,合成条件极其苛刻,为此对原料组成、成胶条件、陈化时间和温度、晶化时间和温度、结构导向剂种类、pH等合成条件对VPI-5分子筛结晶度的影响作了较为详尽的研究,结果表明有机胺在晶化过程中具有结构导向作用,但不起空间填充作用,加有机胺前的陈化过程是必要的.     

超大孔磷酸铝分子筛的合成及性能

1988年Davis等首次报道了以二正丙胺和四丁基氢氧化铵为结构导向剂合成出一种命名为VPI-5的新型磷酸铝超大孔分子筛。它是一族具有相同三维拓朴学骨架的磷酸铝系分子筛,该结构的对称性属六方晶系,P6_3cm空间群,单位晶胞由36个TO_2组成,晶胞参数α=1.8989nm,c=0.8112nm,其主孔道由18员环构成,孔直径约为1.2-1.3nm。     

SAPO-34分子筛催化丁烯转化制丙烯的研究

通过水热法合成SAPO-34分子筛,将其制成催化剂用于催化丁烯转化制取丙烯,考察了反应温度、空速和铝磷比等对催化性能的影响;还比较了SAPO-34分子筛与ZSM-5分子筛催化该反应的差异.结果表明,在实验范围内,反应温度升高会使得丁烯的转化率明显增高,且丙烯选择性提高;而空速增加,则丁烯的转化率和丙烯选择性降低;铝磷比越大,对丙烯的选择性越差.在有效的反应时间内,SAPO-34分子筛催化效果好于ZSM-5分子筛,但单程寿命较ZSM-5分子筛短.     

Raman and 29Si MAS NMR spectroscopy of framework materials containing three-membered rings

Raman and ²⁹Si MAS NMR spectroscopies are evaluated for the identification of three-membered rings (3MR) in framework oxide materials. Raman and ²⁹Si MAS NMR spectra from the 3MR-containing materials euclase, phenakite, clinohedrite, willemite, lovdarite, VPI-7, ZSM-18 and dipotassium zinc tetrasilicate are presented. The Raman spectra from these materials do not exhibit common bands representing vibrational modes assignable to individual 3MR. The dense beryllosilicate and zincosilicate minerals exhibit ²⁹Si MAS NMR resonances indicative of silicon positioned in 3MR while the molecular sieves lovdarite and VPI-7 give ²⁹Si MAS NMR resonances that can be assigned to silicons located at the center of “spiro-5” units that are constructed from two 3MR. Silicon atoms located in isolated 3MR in the molecular sieves ZSM-18 and dipotassium zinc tetrasilicate do not exhibit ²⁹Si MAS NMR resonances that can be distinguished from those assigned to silicons residing in 4MR and larger.The ²⁹Si MAS NMR spectra from the new materials VPI-8, VPI-9 and VPI-10 do not exhibit ²⁹Si MAS NMR resonances indicative of “spiro-5” units. The presence of isolated 3MR in these materials cannot be ruled out from the ²⁹Si MAS NMR spectroscopic results.     

大孔磷酸铝分子筛VPI—5与MCM—9的合成与表征

1988年,Davis等首次合成了一种具有十八元环、孔道直径大于10~(-7) cm的新型VPI-5分子筛。次年7月,他们又详细报道了以四丁基氢氧化铵为结构导向剂合成的VPI-5分子筛。以二正丙胺(DPA)为结构导向剂也可合成VPI-5,但文献对这一合成产物没有给予必要的结构表征。MCM-9是Derouane等首先合成的,他们在反应混合物中加有正己醇,并采用液-固相反应方法制备了这种与VPI-5结构相似的磷酸硅铝分子筛。我们以二正丙胺为结构导向剂,用水热晶化法合成了VPI-5和MCM-9 2种大孔分子筛,并对其进行了结构表征。     

The Influence of Heteroatom M(M = B, Al, Ge, Ga, Fe)on the Adsorption Properties of M-ZSM-12 Zeolites

Heteroatom M-ZSM-12 zeolites(M=B, Al, Ge, Ga, Fe) are hydrothermally synthesized and it is proved that the heteroatom M is involved in the framework of synthesized molecular sieves by means of XRD, IR spectra. The results of adsorption and diffusion experiments indicate that the heteroatom M modifies the pore volume, specific surface area, and the channel of ZSM-12 molecular sieves.     

杂原子分子筛(Ⅱ)——B-Si Pentasil型沸石分子筛晶体结构的研究

应用多晶X射线衍射法测定了B-SiPentasil型沸石分子筛的晶体结构并经Rietveld法修正.其晶胞参数为:α=19.983(1)Å;b=19.973(1)Å;c=13.303(1)Å.空间群为D_2h¹⁶-P_nma.晶体的骨架结构与所报导的Si-AlZSM-5相似.结构测定的结果表明:硼原子进入了沸石分子筛的骨架.     

Hetero-Atom Zeolite (Ⅱ)——Studies on the Crystal Structures of B-Si Pentasil zeolite Molecular Sieves

The crystal structure of B-Si pentasil zeolite molecular sieve was determined by means of the x-ray diffraction for polycrystalline samples and refined by Rietveld method.The parameters of the unit cell are e=19.983(1)A;b=19.773(1)A;c=13.303(1)A.Its space group is D2h1G-Pnma The framework topology found agrees with reported Si-Al ZSM-5zeolite molecular sieves.It is concluded from the structural determination that B is introduced into the framework of this sample.     

ZSM-5/MCM-41复合分子筛的合成与表征

以碱处理的ZSM-5浆液为硅铝源,通过水热自组装过程合成了介孔-微孔复合孔道结构的分子筛,并采用XRD、BET、HRTEM、Py-IR和水热处理等手段对合成分子筛进行了表征。结果表明,碱处理ZSM-5时的苛刻程度是影响复合分子筛合成的重要因素,适宜的碱处理条件为NaOH浓度1 mol/L、80℃时处理1 h。表征结果表明,复合分子筛具有规整互通的微孔-介孔梯级复合孔道结构,孔容、比表面积和平均孔径分别为0.63 mL/g,684 m²/g和3.76 nm,属典型的MCM-41结构;与MCM-41相比,复合分子筛的B酸(尤其是强B酸)酸量明显增强,水热稳定性显著提高。     

预先负载原料法合成ZSM-5/SAPO-5复合分子筛

采用预先负载原料法合成了一系列ZSM-5/SAPO-5(核/壳)双结构分子筛, 研究了预负载磷酸的条件对核壳结构分子筛的形成及性质的影响, 采用X射线衍射、扫描电子显微镜、X射线能量散射谱和红外光谱等手段对样品进行了表征. 结果表明, 负载原料的预处理条件明显影响磷与ZSM-5间的作用力及复合分子筛的结晶度和颗粒形貌等特性. 与常规合成方法相比, 在适宜的条件下采用这种方法更有利于小颗粒SAPO-5分子筛的形成及其在ZSM-5表面的生长.     

The influence of pore structure on reaction mechanism of propylene dimerization in zeolite: A theoretical viewpoint

Molecular sieves have been widely used in the petrochemical industry as environment-friendly catalysts. The pore structure is an important factor influencing the catalytic performance of the zeolite. In this work, a combined Our own N-layered Integrated molecular Orbital and Molecular mechanics method was used to study the mechanism of propylene dimerization in four zeolites (ZSM-5, BEA, MCM-22, and MOR) with different pore structures. Comparing the stepwise mechanism and the concerted mechanism, it is found that the two mechanisms compete with each other in the macroporous BEA, MCM-22, and MOR zeolites, and both mechanisms are possible. However, in ZSM-5 zeolite with medium pore size, the propylene dimerization reaction tends to proceed according to the stepwise mechanism. Furthermore, no matter which mechanism is adopted, the activation energy of propylene dimerization reaction in MCM-22 is the smallest in the four zeolites, indicating that its MWW-type structure (A framework type defined by the International Zeolite Association) may be the most favorable pore structure for the reaction and possesses the highest catalytic activity.     

利用ＳＢＡ-１５介孔内纳米碳合成含介孔的ＺＳＭ-５分子筛

SBA-15介孔分子筛内填充蔗糖并炭化后, 分别在碱性和弱酸性条件下, 用含铝源及TPABr的溶液浸渍,将SBA-15分子筛孔壁的无定形结构转化成ZSM-5分子筛的晶体结构, 除碳后得到含介孔的ZSM-5分子筛. 用X射线衍射、 N_2吸附-脱附、 ~(27)Al MAS NMR、 NH_3-TPD、 TEM、 SEM等对样品进行了表征, 考察了晶化时间等参数对样品的影响. 结果表明, 碱性条件下合成的ZSM-5分子筛晶体中含有少量孔径约3.2～4.2 nm的介孔孔道, 其酸强度接近与常规ZSM-5分子筛的酸强度;弱酸性条件下合成的ZSM-5分子筛晶体中含有大量孔径约1.4～1.6 nm的孔道, 其酸强度明显低于常规ZSM-5分子筛的酸强度.     

系列微孔磷酸镓的合成与结构研究

目前,新型微孔无机固体化合物的合成是一个活跃的研究领域,本文报道在R-Ga₂O₃-P₂O₅-H₂O体系中(R=有机模板剂)系列磷酸镓分子筛的合成与结构的研究。     

Ortho-selectivity in aluminophosphate molecular sieves: A molecular simulation study

Monte Carlo adsorption simulations of xylenes have been performed in aluminophosphate molecular sieve structures. A new force field fitted for o-xylene in AlPO₄-5 was used. It is shown that force fields have good transferability among the aluminophosphate sieves series and the new force field adequately describes the experimentally observed adsorption isotherms for xylene/AlPO₄-5. A previous investigation of adsorption isotherms and structural analysis has been extended to AlPO₄-8 and VPI-5 sieves. In AlPO₄-8, like in AlPO₄-5, the variations in the channels diameters and the corresponding interaction energy of the molecule-crystal lattice drive all molecular positioning. In VPI-5, the modulation between wide and narrow regions becomes negligible due to the larger pore diameter, so no ortho-selectivity was observed. The simulations confirm the ortho-selectivity mechanism proposed to aluminophosphates.     

具有MFI结构的La-Si ZSM-5分子筛的合成

首次合成了稀土元素掺杂的具有MFI结构的La-Si ZSM-5分子筛,并采用各种技术对所合成的分子筛进行了表征.XRD衍射表明所合成的微孔材料具有典型的MFI结构,N2吸脱附、FT-IR及SEM测试结果均表明镧原子进入了分子筛骨架.     

晶种和溶剂对复合分子筛形成的影响

采用包埋法合成ZSM-5/SAPO-5核壳结构复合分子筛,研究了凝胶组成对该材料性能的影响,并利用X射线衍射和扫描电镜等手段对其进行了表征。结果表明,合成的分子筛是以ZSM-5为核,SAPO-5为壳的双结构复合分子筛。通过向凝胶中加入晶种或者调节溶剂性质可以明显改变复合材料的结晶度和颗粒形貌。引入晶种合成材料的颗粒形貌以椭圆型为主,分子筛的结晶度增加;以醇和水混合物为溶剂合成分子筛的颗粒仍以球形为主,分子筛的结晶速率降低,结晶度的最高值降低。     

两阶段晶化合成复合分子筛

采用低温与高温相结合的两阶段晶化方式合成了一系列ZSM-5(core)/SAPO-5(shell)双结构分子筛, 研究了合成条件对核壳结构分子筛的形成及性质的影响, 并采用X射线衍射、扫描电镜、X射线能量散射谱、红外光谱及N₂静态吸附等手段对样品进行表征. 实验结果表明, 与直接高温晶化相比, 两阶段晶化方式在短晶化时间内合成的复合材料中SAPO-5的结晶度较低, 而合成纯SAPO-5分子筛的结晶度却明显较高; 两阶段晶化的方式能适当促进核壳结构型复合分子筛的形成, 减少SAPO-5的独立生长.     

在无有机导向剂条件下采用乙醇为助剂合成高硅沸石

高硅沸石具有优异的热稳定性、水热稳定性、大的微孔体积、高表面积和均匀的微孔孔道,因而广泛应用于催化领域.然而,高硅沸石的合成往往需要使用有机结构导向剂,不但增加了沸石合成成本,而且还产生了大量的三废排放.为了解决这个问题,我们发展了在无有机导向剂存在条件下采用沸石晶种诱导合成沸石的方法,但是该方法合成的沸石产物骨架富铝...     

ZSM－35分子筛的合成及模板效应的研究

以1,6-己二胺为模板剂合成了ZSM-35分子筛,通过对比ZSM-35、ZSM-5和丝光沸石的合成条件,采用化学组成分析、热重分析及¹³CNMR等技术研究了1,6-己二胺和乙二胺的模板效应。结果表明,二者均对ZSM-35有较好的模板作用,而1,6-己二胺对ZMS-5的模板效应更佳。