Yunpeng Xu

Effect of water on the ionothermal synthesis of molecular sieves

AlPO4-11 and AlPO4-5 molecular sieves are ionothermally prepared without addition of water by using anhydrous starting materials, such as NH4H2PO4, pseudoboehmite (AlOOH), and NH4F. The synthesis appears to be an autocatalytic process. Water has a remarkable effect on the synthesis process. Addition of reagent quantities of water (H2O/Al = 1, molar ratio) can enhance the crystallization kinetics greatly.

Ionothermal Synthesis of an Aluminophosphate Molecular Sieve with 20‐Ring Pore Openings

Crystalline porous materials with large or extralarge pores continue to be of particular significance in both industry and academia for their potential applications in shape-selective catalysis and adsorption/separation. Of these zeolitic materials, especially aluminosilicateand aluminophosphate-based molecular sieves are of prime interest because of their high stability associated with their widespread use in many established process and emerging applications. The materials VPI-5 (VFI framework type, 18-ring) and UTD-1 (DON framework type, 14-ring) were the first extra-large pore (pores constructed of more than 12 Tatoms) aluminophosphate and aluminosilicate materials discovered. The oxide frameworks are built up by corner-sharing [AlO4] and [PO4] tetrahedra as well as [AlO4] and [SiO4] tetrahedra. In the search for materials with even larger pores, an anionic open-framework aluminophosphate JDF-20 (20-ring) was reported; however, it could not be classified as a zeolite because its framework (with an Al/P ratio of 5:6) is unstable upon removal of the occluded protonated templates by calcination. Larger pore openings were also achieved using Ge or Ga as the framework Tatom in a high amount, for example in ECR-34 (ETR framework type, 18-ring), ITQ-33 (18-ring), cloverite (-CLO framework type, 20ring), and ITQ-37 (30-ring). In this context, the use of Ge or Ga as framework atoms as well as fluoride has been found to facilitate the formation of a double four-ring (D4R) unit. This is in agreement with the prediction by Brunner and Meier that structures with extra-large pores should contain a large number of threeand four-membered rings. Ionothermal synthesis, in which ionic liquids act as both the solvent and template, is a novel method that has attracted great interest in the synthesis of zeolitic and other porous materials. Besides the advantage of experimenting at ambient pressure, ionic liquids offer different chemistry and structural variety associated with the use of additional amines as structure-directing agents (SDA), and therefore open up new vistas for the synthesis of new porous materials. Herein, we report the ionothermal synthesis of the first aluminophosphate molecular sieve with 20-ring pore openings, denoted as DNL-1 (Dalian National Laboratory Number 1). This molecular sieve was confirmed as a structural analogue to the gallophosphate molecular sieve cloverite by using a combination of Rietveld refinement of powder X-ray diffraction (PXRD) data and NMR analysis. Moreover, in comparison to cloverite, DNL-1, as-synthesized and calcined, exhibits excellent stability. DNL-1 was synthesized in the ionic liquid 1-ethyl-3methylimidazolate bromide ([emim]Br) with 1,6-hexanediamine (HDA) as the co-SDA. The detailed synthetic procedure is described in the Experimental Section. The assynthesized DNL-1 material displays uniformly globular agglomerates of grainlike nanocrystals with a diameter of about 20 mm (see the Supporting Information). Analysis by energy dispersive X-ray spectroscopy (EDX) indicates the P/ Al/F molar ratio of approximately 3:3:1. The inductively coupled plasma (ICP) analysis gives the content (wt%) of Al 16.50 and P 16.65. The elemental and thermogravimetric (TG) analyses show the content (wt%) of C 9.72, N 3.64, H 3.29, and a total weight loss of 34%. Combined with the results of the structure refinement (see below), the chemical formula of DNL-1 was determined as j (C6N2H18)104(C6N2H11)80(H2O)910 j [Al768P768O2976(OH)192F288]. Using the initial structure model from cloverite, the Rietveld refinement of as-synthesized DNL-1 was successfully performed in space group Fm 3c with refined unit cell parameter a= 51.363(1) , which is comparable to that of cloverite a= 51.713 , considering the smaller ionic radius of Al. Similar results were observed in the all-silica and Gecontaining polymorph C of zeolite Beta. Figure 1 shows the very good agreement between observed and calculated PXRDpatterns, taking into account the limited signal to noise ratio, in particular for the data collected at a high angle which can be reflected from the expected R factor of 14.5%. These results adequately confirm that DNL-1 is a pure aluminophosphate analogue of the -CLO structure. The skeletal model of the refined framework structure is shown in Figure 2. The framework of DNL-1 shows the general features of the -CLO structure: 1) two nonintersecting three-dimensional channel systems with 20-ring and 8-ring windows, respectively, 2) four terminal hydroxy groups (Al [*] Y. Wei, Prof. Z. Tian, R. Xu, Dr. H. Ma, R. Pei, Prof. W. Zhang, Prof. Y. Xu, Dr. L. Wang, K. Li, Dr. B. Wang, G. Wen, Prof. L. Lin State Key Laboratory of Catalysis Dalian National Laboratory for Clean Energy Dalian Institute of Chemical Physics Chinese Academy of Sciences, Dalian 116023 (China) Fax: (+86)411-843-79151 E-mail: tianz@dicp.ac.cn

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.

Preparation of Mn substituted La-hexaaluminate catalysts by using supercritical drying

LaMnxAl12−xO19 catalysts were prepared from NH4OH and metal nitrates solutions. Supercritical drying (SCD) and conventional oven drying (CD) methods were used to extract the water in the hydrogel. The effects of drying methods on properties of the catalysts were investigated by means of TEM, N2-adsorption, thermogravimetry (TG)–differential thermal analysis (DTA) and X-ray diffraction. SCD method is beneficial to maintain high surface area and improving catalytic activity for methane combustion of the catalyst. The specific surface area and pore volume of LaMn 1Al11O19 catalyst prepared by SCD method are 28 m 2 /g and 0.23 cm 3 /g, respectively, and the ignition of methane could be carried out at 450 ◦ C. However, those of the CD catalyst prepared from the same precursor are 15 m 2 /g, 0.11 cm 3 /g and 530 ◦ C, respectively. Suitable Mn content (0 ≤ x ≤ 2) could promote the formation of LaMnAl11O19 hexaaluminate, while further addition of Mn (2

Ionothermal Synthesis of Magnesium‐Containing Aluminophosphate Molecular Sieves and their Catalytic Performance

Owing to their promising catalytic and adsorptive properties, microporous materials, often referred to as molecular sieves or open-framework materials, have attracted more and more attention in different research fields. Among them, microporous aluminiophosphate molecular sieves (designated AlPO4-n) have been extensively studied by many authors, owing to their wonderfully complex structures and broadly applications since their discovery in 1982. However, because the frameworks of these materials are neutral and lack of Bronsted acid sites, sometimes they can not be used in catalysis directly. Nevertheless, the lattice Al and/or P atoms in the AlPO4-n frameworks can be partially replaced by silicon (designated (SAPO-n) and/or other metal elements (designated MeAPO-n), to form frameworks with Bronsted acid sites and/or catalytically active metal centers. Commonly, AlPO4-n and MeAPO-n compounds are often crystallized from a gel under hydrothermal or solvothermal conditions. Recently, a novel synthetic route (ionothermal synthesis) provides a potential route to making these microporous materials. Ionothermal synthesis is the use of an ionic liquid or eutectic mixture as the reaction solvent and if necessary, the structure-directing agent in the synthesis of materials. Ionic liquids are special molten salts typically containing organic cations and inorganic anions. The peculiar properties of ionic liquids endow the ionothermal synthesis many interesting features and potential advantages over the traditional methods of molecular sieve synthesis. For example, the ionothermal synthesis can take place at ambient pressure because of the vanishingly small vapor pressure of ionic liquids, which eliminates the safety concerns associated with high pressures. In addition, the excellent microwave-absorbing property of ionic liquids allows the ionothermal synthesis being carried out under microwave conditions, leading to the rapid crystal-growth rate and high product selectivity. Although many AlPO4-based molecular sieves including some novel-framework topologies have been prepared using ionothermal method, the amount of the MeAPO-n structures synthesized ionothermally is relatively small. To date, only several SAPO-n and CoAPO-n 15] structures could be obtained by using this new synthetic technique. Moreover, the research on the applications of these MeAPO-n compounds to catalysis or gas adsorption has not been reported in the literature. Herein we demonstrate that the ionothermal synthesis method can be applied to the synthesis of MeAPO-n materials with excellent catalytic performance. In the present work, a magnesium compound was introduced into the reaction system of AlPO4-n and several Mg-containing aluminophosphate molecular sieves were successfully synthesized in 1-butyl 3-methylimidazolium bromide ionic liquid ([bmim]Br). Results are presented about the physical and chemical characterization (such as X-ray diffraction: XRD, X-ray fluorescence: XRF, scanning electron microscopy: SEM, Brunauer–Emmett–Teller: BET, NH3-temperature programmed desorption: NH3-TPD, thermogravimetric: TG, and NMR analysis) of the MAPO samples obtained with different Mg contents and amine as well as their catalytic evaluation in the hydroisomerization of n-docecane. Table 1 summarizes the details of the synthesis conditions and the products obtained ionothermally. Only the AlPO4tridymite dense phase could be obtained at 170 8C for 3 day without the addition of metal elements (Table 1, AlPO). [a] Dr. L. Wang, Dr. Y.-P. Xu, B.-C. Wang, Prof. Z.-J. Tian, Prof. L.-W. Lin Dalian National Laboratory for Clean Energy State Key Laboratory of Catalysis Dalian Institute of Chemical Physics, Chinese Academy of Sciences 457 Zhongshan Road, Dalian, 116023 (China) Fax: (+86)411-84379151 E-mail : wl7830@dicp.ac.cn tianz@dicp.ac.cn [b] Prof. S.-J. Wang, Prof. J.-Y. Yu Department of Chemical Engineering Dalian Institute of Light Industry Dalian, 116034 (China) Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/chem.200801383.

Ionothermal Synthesis of Aluminophosphate Molecular Sieve Membranes through Substrate Surface Conversion

Applications of zeolite membranes in separation, chemical sensors, and catalytic membrane reactors have led to extensive studies on their fabrication. To date, mainly silicatebased zeolite membranes of the structure types MFI, DDR, LTA, and FAU have been synthesized on different substrates and evaluated for singleor multiple-gas permeation. Routes for the synthesis of zeolite membranes can be broadly classified into two categories: in situ and secondary growth synthesis, both of which are derived from the strategy of hydrothermal zeolite synthesis. However, the high autogenous pressure associated with hydrothermal procedures is inconvenient for preparation of zeolite membranes, especially for large-scale production, due to safety concerns and the risk of molecular sieve collapse. On the other hand, although aluminophosphate and silicoaluminophosphate membranes for gas separation have been prepared, there are few reports on the preparation of aluminophosphate molecular sieve membranes, which suggests that hydrothermal preparation of such membranes may be difficult. Ionothermal synthesis, which uses ionic liquids as reaction media instead of water or organic solvents, allowed highly efficient preparation of aluminophosphate molecular sieves under ambient pressure. Ionic liquids (ILs) are commonly defined as salts that consist of organic cations and inorganic anions with melting temperatures below 100 8C. ILs are well known as environmentally benign and designable solvents, which endow ionothermal synthesis with interesting features and many potential advantages over the hydrothermal method. As a result of the negligible vapor pressure of ILs, ionothermal synthesis can take place at ambient pressure, which eliminates safety concerns. The organic cation of the IL can act as a structure-directing agent (SDA), or play a cooperative structure-directing role together with introduced amines and quaternary ammonium compounds. AEL, AFI, CHA, LTA, and CLO types of aluminophosphate molecular sieves have been successfully synthesized by ionothermal methods. Ionothermal synthesis is a promising method for the preparation of aluminophosphate molecular sieve membranes under ambient pressure. Yan and co-workers prepared AlPO-11 and SAPO-11 films on aluminum alloys as anticorrosion coatings by in situ ionothermal synthesis. To the best of our knowledge, no permeable membrane has been previously prepared on a porous substrate by the ionothermal method. Here we report an ionothermal method for the synthesis of permeable aluminophosphate molecular sieve membranes on porous alumina disks by substrate-surface conversion. Molecular sieve membranes of types AEL, AFI, CHA, and LTA were prepared by placing homemade d-alumina substrates (2.0 mm thickness, 20 mm diameter, and 10 nm average pore size; see Supporting Information for details) in a solution of IL, phosphoric acid, hydrofluoric acid, and, if required, organic amines with no additional source of Al. Table 1 lists the initial solution composition, crystallization

Synthesis of the high-surface-area CexBa1−xMnAl11Oy catalyst in reverse microemulsions using inexpensive inorganic salts as precursors

The high-surface-area CexBa1−xMnAl11Oy (x = 0, 0.1, 0.2, 0.3) catalysts were synthesized in the nonionic reverse microemulsion (ME), using the inorganic salts as the reactants. The supercritical drying (SCD) and conventional oven drying (CD) methods were used to remove the water in hydrogels, respectively. The CexBa1−xMnAl11Oy samples were characterized by N2-adsorption, transmission electron microscopy (TEM), TGA-DTA, and X-ray powder diffraction (XRD). The effects of the microemulsion composition, the drying method, the calcination temperature and the introduction of Ce on the catalysts were investigated. The results showed that the morphology of the catalyst was controlled by the microemulsion microstructure; and the homogeneity of the precursor was improved effectively by the reverse microemulsion method and the supercritical drying method. Due to the high homogeneity of the precursors, the initial formation temperature of the hexaaluminate phase decreased to lower than 1100 °C. The BaMnAl11O19 catalyst had high surface area (72.4 m2 g−1) and high catalytic activity (T10 = 445 °C) for methane combustion. When Ce was introduced, the CexBa1−xMnAl11Oy catalyst (x = 1) had the higher activity (T10 = 430 °C) than that of the BaMnAl11O19 one due to a synergetic effect between Ce and Mn.

Formation of a novel type of reverse microemulsion system and its application in synthesis of the nanostructured La0.95Ba0.05MnAl11O19 catalystElectronic supplementary information (ESI) available: Table 1, Figs. 1b, 5, 6 and 7. See http://www.rsc.org/suppdata/cc/b4/b404133j/

In the study, a novel microemulsion system, consisting of water, iso-propanol and n-butanol, was developed to synthesize the nanostructured La(0.95)Ba(0.05)MnAl(11)O(19) catalyst with high surface area and catalytic activity for methane combustion.

The production of light olefins by catalytic cracking of the microalga Isochrysis zhanjiangensis over a modified ZSM-5 catalyst

This study investigated the catalytic cracking of the microalga Isochtysis zhanjiangensis over a modifled ZSM-5 catalyst with the aim of producing C2-C4 light olefins. Compared with the thermal cracking process, the catalytic cracking of this microalga displayed higher selectivity for and greater yield of these olefins. The catalytic cracking of extracted lipids and the corresponding residues of the microalga was also examined, and the results showed that the lipids could be efficiently converted to light olefins. The catalytic cracking of lipids extracted by different solvents demonstrated that neutral lipids gave the highest yield of light olefins at 36.7%. The yields of light olefins obtained from catalytic cracking of the extraction residues were much lower than the yields obtained from lipids, and thus the lipids, especially the neutral lipids, are the primary contributors to the generation of light olefins. Isochrysis zhanjiangensis with an elevated neutral lipid content will therefore give the highest yield of light olefins through catalytic cracking

Catalytic pyrolysis of microalga Chlorella pyrenoidosa for production of ethylene, propylene and butene

This paper investigated the process of catalytic pyrolysis of lipid-rich microalga Chlorella pyrenoidosa for the production of light olefins (ethylene, propylene and butene). A modified ZSM-5 zeolite catalyst was used in the reactions, and it had high selectivity for the light olefins production. The catalytic pyrolysis performances of microalga Chlorella pyrenoidosa in nitrogen and steam reaction atmospheres were investigated. The catalytic pyrolysis performances in one-step and two-step processes were investigated and compared. The effects of reaction temperatures and water flow rates on the catalytic pyrolysis performances were also explored. The results showed that higher yield of light olefins was obtained in the steam reaction atmosphere as compared with that in the nitrogen atmosphere. The carbon yield of light olefins obtained from two-step catalytic pyrolysis was nearly three times that from one-step catalytic pyrolysis. The two-step catalytic pyrolysis process also facilitated the production of aromatic hydrocarbons in the liquid products. The maximum carbon yield of light olefins could reach 31.9% in the two-step process under the reaction temperature of 923 K and water flow rate of 30 ml h−1.