Synthesis Of Aluminophosphate Molecular Sieves Research Articles

Synthesis of Aluminophosphate Molecular Sieves in Alkaline Media.

Unlike conventional aluminosilicate zeolites synthesized in alkaline media, aluminophosphate molecular sieves (AlPOs) have always been prepared under acidic conditions in the past three decades; this has been regarded as one of essential factors for synthesis, except for the case of silica-substituted analogues (SAPOs). For the first time, we demonstrate herein a simple and generalized route for synthesizing various types of aluminophosphate molecular sieves in alkaline media. A series of aluminophosphate sieves and their analogues have been prepared with different quaternary ammonium cations as structure-directing agents in this manner. The above successes have extended the systematic media from acidic or neutral to alkaline for the preparation of a series of aluminophosphate molecular sieves, which possibly open an alternative route for the synthesis of aluminophosphate molecular sieves.

Synthesis of Aluminophosphate Molecular Sieves by Ball Milling and Recrystallization

Synthesis of Aluminophosphate Molecular Sieves by Ball Milling and Recrystallization

Cooperative structure-directing effect in the synthesis of aluminophosphate molecular sieves in ionic liquids

In situ two-dimensional NMR and fluorescence emission spectroscopy were employed to investigate the cooperative structure-direction effect of organic amine such as morpholine in the synthesis of aluminophosphate molecular sieves in ionic liquids. In situ rotating frame nuclear Overhauser effect spectra (ROESY) together with fluorescence measurements demonstrate that the aggregates between imidazolium cations and morpholines through intermolecular hydrogen bonds can be formed in the gel during the crystallization of molecular sieves. Combining with the characterizations of the solid products by solid-state NMR, it is verified that different aggregates of organic amines with imidazolium cations, which is similar to self-assembled supramolecular analogues, could act as the structure-directing agents for selective tuning of the framework topologies such as AEL, AFI and LTA in the final solid products.

New Insights into the Role of Amines in the Synthesis of Molecular Sieves in Ionic Liquids

A combination of state-of-the art in situ one- and two-dimensional NMR spectroscopy and density functional theory (DFT) calculations have been employed for the first time to investigate the role of amines in the synthesis of aluminophosphate molecular sieves in ionic liquids (ILs). In situ rotating-frame nuclear Overhauser effect spectroscopy (ROESY) was used to demonstrate that the hybrid of imidazolium ionic liquids with organic amines, such as morpholine, connected through a hydrogen bond can be formed in the gel during the crystallization of molecular sieves. By combining the characterizations of the final solid products obtained by using XRD analyses, solid-state NMR spectroscopy, thermogravimetric analysis, and DFT calculation results, it was verified that the hybrid between morpholine and the imidazolium cation in the initial preparation stage can act as the structure-directing agent (SDA) for the synthesis of AFI-structured aluminophosphate molecular sieves. Our findings may suggest a synthesis mechanism of molecular sieves in ionic liquids in which the IL-organic amine hybrid is required in the nucleation step, whereas the crystal growth occurs through the occlusion of ionic liquids in the zeolite channels.

Microwave‐Enhanced Ionothermal Synthesis of Aluminophosphate Molecular Sieves.

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Microwave‐Enhanced Ionothermal Synthesis of Aluminophosphate Molecular Sieves

Schnell und sicher: Die Kombination von Mikrowellen mit ionischen Flüssigkeiten bietet eine neue Möglichkeit, Alumophosphat-Molekularsiebe herzustellen (siehe Bild). Diese Methode ermöglicht eine Synthese bei Normaldruck und zeichnet sich durch eine rasche Kristallisation und eine hohe Strukturselektivität aus. Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2001/2006/z600054_s.pdf or from the author. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Microwave‐Enhanced Ionothermal Synthesis of Aluminophosphate Molecular Sieves

Microwave‐Enhanced Ionothermal Synthesis of Aluminophosphate Molecular Sieves

Structure-Directing Role of Amines in the Ionothermal Synthesis

The structure-directing effect of amine has been observed in the ionothermal synthesis of aluminophosphate molecular sieves in 1-butyl-3-methylimidazolium bromide ionic liquid. The seven different amines we tested have an influence on the crystallization dynamics and the final product, leading to the formation of pure AFI and ATV structures.

Synthesis of aluminophosphate molecular sieves with AFI topology substituted by alkaline earth metal and their application to solid acid catalysis

Metalloaluminophosphate molecular sieves with AFI topology, in which a part of aluminum is substituted isomorphously to alkaline earth metals: Mg, Ca, Sr, and Ba (MAPO-5; M = Mg, Ca, Sr and Ba), were synthesized by hydrothermal synthesis (HTS) method and two types of dry–gel conversion (DGC) methods: vapor-phase transport (VPT) and steam-assisted conversion (SAC) methods, using triethylamine (Et 3N) as a structure-directing agent (SDA). Systematic studies were carried out by varying the synthesis parameters such as gel composition including content of alkaline earth metals and SDA, amount of external bulk water, and heating time. It has been observed that MO/Al 2O 3 ratio of starting gel plays an important role in the crystallization of the molecular sieves. The ratios from 0.025 to 0.10 gave pure MAPO-5 with AFI topology; however, MAPO-34 with CHA topology was observed as an impurity with further increase of the Mg content. The amount of Et 3N also played important role for the crystallization: Et 3N/Al 2O 3 ratios from 0.38 to 0.76 gave pure MgAPO-5 and CaAPO-5, whereas SrAPO-5 and BaAPO-5 were obtained as pure phase from 0.76 to 1.52. MAPO-5 molecular sieves were crystallized even in the absence of external bulk water. Period for crystallization was studied from 3 to 48 h; the highest intensities were observed between 12 and 18 h for all cases. The occluded SDA was removed by calcination at 550 °C. The molecular sieves were characterized by XRD, ICP, TG-DTA, SEM, FT-IR, N 2 and pyridine adsorption, and NH 3-TPD. Alkaline earth metals, at least a part of them, are isomorphously substituted in the framework of AFI topology judging from NH 3-TPD, unit cell parameters, and their FT-IR spectra of adsorbed pyridine. The substitution of alkaline earth metal with aluminum produced acidic sites in the molecular sieves: substitution of Al 3+ to Mg 2+ enhanced the appearance of strong acidity; however, only weak acidities appeared for CaAPO-5, SrAPO-5, and BaAPO-5 in small amount. The isopropylation of benzene and biphenyl was examined over MAPO-5 by VPT method to characterize their acidic properties. Their catalytic activity decreases in the order: MgAPO-5 ≫ CaAPO-5 ⩾ SrAPO-5 ⩾ BaAPO-5; ≫ APO-5; moderate to good selectivity for 4,4′-DIPB was observed in the level of 50–70% for all MAPO-5. These catalytic properties support strongly the incorporation of alkaline earth metals in the AFI framework.

Combinatorial Methods for the Synthesis of Aluminophosphate Molecular Sieves.

Automatic dispensing of reagents into autoclave blocks followed by synthesis, isolation, and automated structure analysis with X-ray diffractometry represents an efficient methodology for the combinatorial synthesis of microporous materials. The figure shows a typical diffractogram of as-synthesized AFI-type molecular sieves taken with a CCD camera.

Effect of the addition of methylene blue to the reaction mixture for the hydrothermal synthesis of aluminophosphate molecular sieves on their morphology

The morphology of aluminophosphate hosts prepared by hydrothermal synthesis with the addition of methylene blue (MB) to the reaction mixture was compared with that of dye-free samples by means of adsorption and electron microscopy methods. With AIPO 4-5, SAPO-5, and FAPO-5 (AFI structure type), no effect of the addition of MB has been found. With AIPO 4-l1 (AEL structure type), MB has caused a 50% contamination with some nonadsorbing material. With AIPO 4-20 and SAPO-34 (SOD and CHA structure types), MB strongly influences the morphology of crystals.

The role of gel chemistry in synthesis of aluminophosphate molecular sieves

The efficiency and product purity of aluminophosphate molecular sieves by the hydrothermal synthesis are affected by the gel chemistry of a reaction mixture. A suitable gel chemistry appears to be a prerequisite for hydrothermally crystallizing the molecular sieves from hydrous gel mixtures. Factors that determine the gel chemistry are the source of aluminum and phosphorus, mixing procedure, gross chemical composition of gel including the water content, and pretreatment of gel. With all these factors specified, the pH of the reaction mixture seems to reflect the gel evolution and crystallization of molecular sieves. Besides the structure-templating effect, organic bases play an important role in determining the gel chemistry. With the addition of organic bases, the pH of the reaction mixture rises to the desirable range of 3.5–6.0. From the properly prepared gel within this pH range, the formation of aluminum phosphate dense phases is eliminated while microporous aluminophosphate is formed as a metastable phase during the hydrothermal crystallization.