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Pan F.,CAS Institute of Process Engineering | Lu X.,CAS Institute of Process Engineering | Lu X.,United Research Center for Resource and Materials | Zhu Q.,CAS Institute of Process Engineering | And 5 more authors.
Journal of Materials Chemistry A | Year: 2014

Nano-sized ZSM-5 aggregates have been rapidly synthesized from leached metakaolin by solid-like state conversion. The influence of synthesis conditions such as TPA+/SiO2, NaOH/SiO2 and SiO2/Al2O3 molar ratios on the final products was investigated. The properties of nano-sized ZSM-5 aggregates were characterized by XRD, SEM, HRTEM, 29Si and 27Al MAS NMR, NH3-TPD, TG, N2 adsorption-desorption and particle size analysis. The results clearly showed that nano-sized ZSM-5 aggregates could be obtained within 2 h via solid-like state conversion. SEM revealed that the obtained ZSM-5 aggregates were irregular spheres that consisted of nano-sized crystallites with 30-50 nm. The crystallization process indicated that the size of flaky raw materials gradually decreased and formed nano-sized particles as time prolonged. Therefore, the transformation mechanism followed the solution mediated mechanism, though only a little water was contained in the system. Compared with the conventional hydrothermal route, the solid-like state conversion not only significantly shortened the crystallization time, but also totally avoided the emission of waste liquids. In addition, for the methanol dehydration reaction, the nano-sized ZSM-5 aggregates obtained by this method showed much better catalytic performance, C2-C4 olefin selectivity and longer lifetime to endure coke deposition than the sample obtained by the hydrothermal route. © The Royal Society of Chemistry 2014. Source


Zhang Z.,Chinese Academy of Sciences | Lu X.,Chinese Academy of Sciences | Lu X.,United Research Center for Resource and Materials | Wang T.,Chinese Academy of Sciences | And 3 more authors.
Journal of Analytical and Applied Pyrolysis | Year: 2014

The dehydration of MgCl2·6H2O in MgCl2·6H2O-NH4Cl-KCl system was investigated. The dehydration process was characterized by X-ray diffraction and chemical analysis. The dehydration effects of MgCl2·6H2O in different systems were compared. The dehydration mechanism of MgCl2·6H2O in MgCl2·6H2O-NH4Cl-KCl system was proposed and discussed. The formation of NH4ClMgCl2·nH2O (6 > n ≥ 0) below 300 °C can effectively suppress hydrolysis. The anhydrous KMgCl3 formed above 400 °C is more stable than anhydrous MgCl2 at elevated temperature, which can effectively protect the dehydration product from hydrolyzing at high temperature. The content of MgO in anhydrous MgCl2 was 0.02 wt.% when dehydrating MgCl2·6H2O in MgCl2·6H2O-KCl-NH4Cl system with the molar ratio of MgCl2·6H2O:KCl:NH4Cl was 1:2.87:1. © 2014 Elsevier B.V. All rights reserved. Source


Chen S.,CAS Institute of Process Engineering | Chen S.,University of Chinese Academy of Sciences | Lu X.,CAS Institute of Process Engineering | Lu X.,United Research Center for Resource and Materials | And 2 more authors.
Journal of Polymer Research | Year: 2015

High modulus and thermal stability of polyimide (PI)/reactive halloysite nanotubes (HNTs) nanocomposites were prepared by in situ polymerization. The pristine HNTs were firstly handled with the tetraethoxysilane (TEOS) and secondly grafted with the silane agent. The fourier transform infrared spectroscopy (FTIR) approved that TEOS was beneficial for the silane agent to modify the HNTs. Scanning electron microscopy (SEM) showed the differences of the morphology between the reactive HNTs and pristine HNTs. PI/reactive HNTs nanocomposites exhibited lower moisture absorption than pure polyimide. The reactive HNTs reduced the transmittance of the nanocomposites. Significant improvements in the thermal stability and glass transition temperature (Tg) of PI/reactive HNTs nanocomposites were achieved by addition of only a small amount of reactive HNTs. It was noteworthy that both the tensile strength and Young’ modulus of PI/reactive HNTs nanocomposites were significantly enhanced. A 62.8 % increase in tensile strength and a 63.7 % increase in Young’ modulus of the nanocomposites with 3 wt.% of the reactive HNTs were achieved. Finally, the preparation mechanism to obtain PI/reactive HNTs nanocomposites was proposed. © 2015, Springer Science+Business Media Dordrecht. Source


Zhang Z.,Chinese Academy of Sciences | Lu X.,Chinese Academy of Sciences | Lu X.,United Research Center for Resource and Materials | Chen S.,Chinese Academy of Sciences | And 3 more authors.
Metallurgical and Materials Transactions B: Process Metallurgy and Materials Processing Science | Year: 2016

To reduce the content of MgOHCl in anhydrous MgCl2, MgOHCl was converted to anhydrous MgCl2 by solid-state reaction. Factors that affect the conversion effects were investigated, including the mol ratio of NH4Cl to MgOHCl, thickness of covering agent, reaction temperature, and reaction time. The conversion process was characterized by XRD analysis and chemical analysis. The solid-state reaction mechanism was studied and discussed. The MgO content in anhydrous MgCl2 achieved 0.05 pct under the optimal conditions: the mol ratio of NH4Cl to MgOHCl was 3:1, thickness of Al2O3 powder 2 cm, reaction temperature 623 K (350 °C), and reaction time 1 hour. © 2015, The Minerals, Metals & Materials Society and ASM International. Source


Zhang C.,CAS Institute of Process Engineering | Zhang C.,University of Chinese Academy of Sciences | Lu X.,CAS Institute of Process Engineering | Lu X.,United Research Center for Resource and Materials | Wang T.,CAS Institute of Process Engineering
Journal of Energy Chemistry | Year: 2015

SAPO-34 molecular sieves were synthesized by the addition of β-cyclodextrin (β-CD) as crystal growth inhibitor using metakaolin as silicon and aluminum sources. Properties of the obtained samples were characterized by XRD, SEM, N2 adsorption-desorption, FTIR, XRF, EDX, NH3-TPD and 29Si MAS NMR. When β-CD was added, crystal size of the SAPO-34 crystals decreased. Variation of Si content from the crystal center to surface decreased while total Si content hardly changed. 29Si MAS NMR results showed that β-CD contributed to better Si dispersion and decreased the size of Si(4Si) patches. Moreover, the MTO (methanol-to-olefin) process was conducted to investigate the influence of β-CD on catalytic performance. The synthesized sample with molar ratio of β-CD/Al2O3 equaling 0.055 remained active for 610 min while the sample synthesized without β-CD for only 280 min, which indicates that the lifetime of catalyst synthesized with β-CD is greatly prolonged. © 2015 Science Press and Dalian Institute of Chemical Physics. All rights reserved. Source

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