Water‐Induced Structural Dynamic Process in Molecular Sieves under Mild Hydrothermal Conditions: Ship‐in‐a‐Bottle Strategy for Acidity Identification and Catalyst Modification

2020 ◽  
Vol 132 (46) ◽  
pp. 20853-20862
Author(s):  
Tantan Sun ◽  
Shutao Xu ◽  
Dong Xiao ◽  
Zhiqiang Liu ◽  
Guangchao Li ◽  
...  
Keyword(s):  
Dynamic Process ◽  
Molecular Sieves ◽  
Hydrothermal Conditions ◽  
Structural Dynamic ◽  
Catalyst Modification

scholarly journals Performance Enhanced SAPO-34 Catalyst for Methanol to Olefins: Template Synthesis Using a CO2-Based Polyurea

Catalysts ◽  
2018 ◽  
Vol 9 (1) ◽  
pp. 16 ◽  
Author(s):  
Yuehong Yu ◽  
Jiaxiang Qin ◽  
Min Xiao ◽  
Shuanjin Wang ◽  
Dongmei Han ◽  
...  
Keyword(s):  
Molecular Sieves ◽  
Catalytic Performance ◽  
Coke Deposition ◽  
Light Olefins ◽  
Bet Surface Area ◽  
Intrinsic Diffusion ◽  
Hydrothermal Conditions ◽  
Mto Reaction ◽  
And Control ◽  
Heterogeneous Size

Introducing mesopores into the channels and cages of conventional micropores CHA (Chabazite) topological structure SAPO-34 molecular sieves can effectively improve mass transport, retard coke deposition rate and enhance the catalytic performance for methanol to olefins (MTO) reaction, especially lifetime and olefins selectivity. In order to overcome the intrinsic diffusion limitation, a novel CO2-based polyurea copolymer with affluent amine group, ether segment and carbonyl group has been firstly applied to the synthesis of SAPO-34 zeolite under hydrothermal conditions. The as-synthesized micro-mesoporosity SAPO-34 molecular sieve catalysts show heterogeneous size distribution mesopores and exhibit slightly decrease of BET surface area due to the formation of defects and voids. Meanwhile, the catalysts exhibit superior catalytic performance in the MTO reaction with more than twice prolonged catalytic lifespan and improvement of selectivity for light olefins compared with conventional microporous SAPO-34. The methodology provides a new way to synthesize and control the structure of SAPO-34 catalysts.

scholarly journals Synthesis of Small-Sized SAPO-34 Crystals with Varying Template Combinations for the Conversion of Methanol to Olefins

Catalysts ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 570 ◽  
Author(s):  
Yanjun Zhang ◽  
Zhibo Ren ◽  
Yinuo Wang ◽  
Yinjie Deng ◽  
Jianwei Li
Keyword(s):  
Molecular Sieves ◽  
Crystal Size ◽  
Ammonium Hydroxide ◽  
Methanol Conversion ◽  
29Si Mas Nmr ◽  
Hydrothermal Conditions ◽  
N2 Adsorption ◽  
Ft Ir ◽  
Ir Analysis ◽  
Adsorption Desorption

SAPO-34 molecular sieves were synthesized under hydrothermal conditions using different combinations of tetraethyl ammonium hydroxide (TEAOH)/morpholine (Mor)/triethylamine (TEA) as templates, with different silicon:aluminum ratios. The physicochemical properties of the synthesized SAPO-34 were characterized using XRD, SEM, N2 adsorption–desorption, XRF, TG, NH3-TPD, FT-IR, and 29Si MAS NMR analyses. According to the SEM and the N2 adsorption–desorption of the catalysts produced by the ternary template exhibited a larger surface area and a smaller crystal size than those produced by the single or binary templates. The FT-IR analysis indicated the increased acidity of the catalyst prepared by the ternary template. A high activity and selectivity to olefins (C2= + C3=) and an optimal silicon to aluminum ratio of 0.4 were obtained from the catalyst synthesized with the ternary template. At the reaction temperature of 450 °C, the methanol conversion approached 100% and the ethylene–propylene selectivity and the lifetime of the catalyst reached maximums of 89.15% and 690 min, respectively.

Unraveling the Crystallization Mechanism of CoAPO-5 Molecular Sieves under Hydrothermal Conditions

2005 ◽  
Vol 127 (41) ◽  
pp. 14454-14465 ◽  
Author(s):  
Didier Grandjean ◽  
Andrew M. Beale ◽  
Andrei V. Petukhov ◽  
Bert M. Weckhuysen
Keyword(s):  
Molecular Sieves ◽  
Crystallization Mechanism ◽  
Hydrothermal Conditions

Thorough investigation of varying template combinations on SAPO-34 synthesis, catalytic activity and stability in the methanol conversion to light olefin

RSC Advances ◽  
2014 ◽  
Vol 4 (91) ◽  
pp. 49762-49769 ◽  
Author(s):  
Mehdi Sedighi ◽  
Hussein Bahrami ◽  
Jafar Towfighi Darian
Keyword(s):  
Catalytic Activity ◽  
Molecular Sieves ◽  
Methanol Conversion ◽  
Hydrothermal Conditions ◽  
Light Olefin ◽  
Tetraethylammonium Hydroxide ◽  
Structure Directing Agents

Crystals of SAPO-34 molecular sieves were synthesized under hydrothermal conditions by using tetraethylammonium hydroxide, morpholine and a mixture of them as structure-directing agents.

scholarly journals Effects of Synthesis Parameters on the Crystallization Profile and Morphological Properties of SAPO-5 Templated by 1-Benzyl-2,3-Dimethylimidazolium Hydroxide

Crystals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 279
Author(s):  
Ismail Alhassan Auwal ◽  
Fitri Khoerunnisa ◽  
Florent Dubray ◽  
Svetlana Mintova ◽  
Tau Chuan Ling ◽  
...  
Keyword(s):  
Molecular Sieves ◽  
Ostwald Ripening ◽  
Heating Time ◽  
Morphological Properties ◽  
Hexagonal Prism ◽  
Hydrothermal Conditions ◽  
Synthesis Parameters ◽  
Temperature Heating ◽  
Synthesis Approach

The formation of SAPO-5 molecular sieves is studied under hydrothermal conditions in the presence of a new templating agent, 1-benzyl-2,3-dimethylimidazolium hydroxide ([bzmIm]OH). The syntheses were carried out by varying the synthesis parameters, viz. crystallization temperature, heating time and reactants molar composition (SiO2, Al2O3, P2O5, [bzmIm]+, H2O) in order to investigate the role of each synthesis parameter on the formation of SAPO-5. The results showed that these synthesis parameters had significant influences on the entire crystallization process (induction, nucleation, crystal growth, and Ostwald ripening) and physicochemical properties of SAPO-5 (morphology and crystal size). Moreover, this study also demonstrated a fast hydrothermal synthesis approach where a SAPO-5 molecular sieve with hexagonal prism morphology could be crystallized within 10 h instead of days using a novel [bzmIm]OH heterocyclic template, thus offering an alternative route for synthesizing zeolite-like materials for advanced applications.

Influence of Alkalinity on the Synthesis of Zeolite A and Hydroxysodalite from Metakaolin

2020 ◽  
Vol 61 ◽  
pp. 51-60
Author(s):  
Raphael Cons Andrades ◽  
Roberto Freitas Neves ◽  
Francisco Rolando Valenzuela Díaz ◽  
Antonio Hortencio Munhoz Júnior
Keyword(s):  
Molecular Sieves ◽  
Amorphous Material ◽  
Reaction Medium ◽  
Added Value ◽  
Nanometer Scale ◽  
Zeolite A ◽  
X Ray Diffraction ◽  
Paper Coating ◽  
Hydrothermal Conditions ◽  
Wide Range

Kaolin is a cheap and abundant source of silica and alumina, which may be used as precursors for the production of zeolites, molecular sieves with pores in the nanometer scale. Brazil, one the largest producers of kaolin, generates tons of kaolin waste in the paper coating process. That waste may be used to synthesize zeolite A and hydroxysodalite, greater added value materials with a wide range of applications. In this work, Zeolite A and hydroxysodalite were synthesized from kaolin waste of processing industries for paper coating. Kaolin was calcined to dehydroxylate kaolinite and obtain metakaolin, an amorphous material with Si/Al ratio equal to 1, being suitable for production of zeolite A and hydroxysodalite. Zeolites were synthesized under static hydrothermal conditions by reacting metakaolin with NaOH solutions of different concentrations. The zeolitic products were characterized by means of X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM). The results showed that the higher the NaOH concentration in the reaction medium, the higher the proportion of hydroxysodalite in the zeolitic samples.

Syntheses of Bulky Y-Zeolite by Hydrothermal Hot-Pressing (HHP) Technique

2006 ◽  
Vol 317-318 ◽  
pp. 97-100 ◽  
Author(s):  
S. Takezoe ◽  
Kazuyuki Hosoi ◽  
Masahiko Tajika ◽  
Yuki Yamasaki ◽  
Atsushi Nakahira
Keyword(s):  
Single Crystal ◽  
Hot Pressing ◽  
Molecular Sieves ◽  
Single Phase ◽  
High Density ◽  
Y Zeolite ◽  
Hydrothermal Conditions ◽  
Precipitation Mechanism ◽  
Naoh Solution ◽  
Dissolution And Precipitation

Synthesis of bulky Y-zeolite was attempted by a hydrothermal hot-pressing (HHP) method. These bulky products synthesized under hydrothermal conditions were identified as Y-zeolite single phase. Especially, bulky Y-zeolite having translucency, high density and large surface area was obtained by HHP treatment at 423K for 2h with 17wt% of 5M-NaOH solution. This solidified zeolite like single-crystal was considered to be made by dissolution and precipitation mechanism. High-density bulky zeolites can be expected as novel molecular sieves and catalysts with high activity.

Study of Fibrous AlPO4-5 via Hydrothermal Conditions: Morphology Evolution and Growth Mechanism

2012 ◽  
Vol 535-537 ◽  
pp. 2535-2539
Author(s):  
Chun Xia Zhao ◽  
Yun Xia Yang ◽  
Wen Chen ◽  
Paul Webley ◽  
Jin Qiao Cao
Keyword(s):  
Hydrothermal Method ◽  
Growth Mechanism ◽  
Molecular Sieves ◽  
Molar Ratio ◽  
Structure Evolution ◽  
Morphology Evolution ◽  
Hydrothermal Conditions ◽  
Morphology And Structure ◽  
Fibrous Morphology ◽  
Morphology Development

Aluminophosphate molecular sieves (AlPO4-5s) with fibrous morphology were readily prepared via hydrothermal method at 180 °C with the initial molar ratio of Al(OiPr)3: H3PO4: TrPA: HF: H2O as 1: 0.83: 1: 0.8: 70. The morphology and structure of the prepared AlPO4-5s were characterized by XRD, SEM, TEM and nitrogen sorption measurement. The morphology development and structure evolution mechanism were proposed.

Phase-Selective Synthesis of a Silicoaluminophosphate Molecular Sieve with 3-Aminopropyltriethoxysilane as the Silica Source

2014 ◽  
Vol 1061-1062 ◽  
pp. 109-111
Author(s):  
Ya Dong Bai ◽  
Hai Rong Zhang ◽  
Pei Wan Bai ◽  
Hong Yan Liu ◽  
Shen Hua Han ◽  
...  
Keyword(s):  
Amorphous Phase ◽  
Molecular Sieves ◽  
Molecular Sieve ◽  
Xrd Analysis ◽  
Similar Reaction ◽  
Selective Synthesis ◽  
Hydrothermal Conditions ◽  
Silicon Source ◽  
Silica Source ◽  
Phase Selectivity

Silicoaluminophosphate (SAPO) molecular sieves with CHA and AFI structures have been synthesized under hydrothermal conditions from similar reaction mixtures using 3-Aminopropyl-triethoxysilane as silicon source. The XRD analysis indicated that the phase selectivity could follow the sequence of SAPO-34→SAPO-34+ SAPO-5→SAPO-5 →amorphous phase with increasing the amount of the silicon source. The phase selectivity can be explained by the increasing alkalinity of the medium with the 3-Aminopropyltriethoxysilane concentration.

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