Effect of steam treatment on catalytic performance of HZSM-5 catalyst for ethanol dehydration to ethylene

2013 ◽  
Vol 110 ◽  
pp. 73-78 ◽  
Author(s):  
Qingtao Sheng ◽  
Kaicheng Ling ◽  
Zhenrong Li ◽  
Liangfu Zhao
Keyword(s):  
Catalytic Performance ◽  
Steam Treatment ◽  
Ethanol Dehydration

Steam treatment of a hollow lithium phosphate catalyst: enhancing carbon deposition resistance and improving the catalytic performance of propylene oxide rearrangement

RSC Advances ◽  
2016 ◽  
Vol 6 (62) ◽  
pp. 57000-57008 ◽  
Author(s):  
Yanan Wang ◽  
Zhishan Li ◽  
Weihua Ma ◽  
Grace Kinunda ◽  
Hongxia Qu ◽  
...  
Keyword(s):  
Reaction Mechanism ◽  
Propylene Oxide ◽  
Carbon Deposition ◽  
Catalytic Performance ◽  
Steam Treatment ◽  
Lithium Phosphate

The reaction mechanism of propylene oxide rearrangement on a hollow lithium phosphate catalyst in the presence of steam.

scholarly journals Non-Hydrolytic Sol-Gel Route to a Family of Hybrid Mesoporous Aluminosilicate Ethanol Dehydration Catalysts

2020 ◽  
Author(s):  
Ales Styskalik ◽  
Imène Kordoghli ◽  
Claude Poleunis ◽  
Arnaud Delcorte ◽  
Denis Dochain ◽  
...  
Keyword(s):  
Gas Phase ◽  
Sol Gel ◽  
Catalytic Performance ◽  
Silica Matrix ◽  
Ethanol Dehydration ◽  
One Pot ◽  
Water Contact ◽  
Hybrid Silica ◽  
Mesoporous Aluminosilicate ◽  
Improved Performance

Organic-inorganic hybrid materials are nowadays intensely studied for potential applications in heterogeneous catalysis because their properties and catalytic behavior differ from pristine inorganic counterparts. The organic groups at the catalyst surface can modify not only its hydrophilicity, but also acidity, hydrothermal stability, porosity, etc. In some cases, such properties alteration leads to improved catalytic performance in terms of activity, selectivity, or stability. However, the choice of organic groups stays relatively narrow, as most reports focus on pendant methyl groups. Here, a series of mesoporous hybrid aluminosilicate materials containing various organic groups was prepared in one pot by non-hydrolytic sol-gel (NHSG). Both aromatic and aliphatic, pendant and bridging organic groups were incorporated. The presence of the organic groups in the bulk and at the outermost surface of the materials was verified by solid-state NMR and ToF-SIMS, respectively. Aluminum is mostly incorporated in tetrahedral coordination in the hybrid silica matrix. The organically modified mesoporous aluminosilicate samples were tested as catalysts in the gas phase ethanol dehydration (which relies on solid acids) and most of them outperformed the purely inorganic catalyst benchmark. While a direct influence of surface hydrophilicity or hydrophobicity (as probed by water sorption and water contact angle measurements) appeared unlikely, characterization of acidity (IR-pyridine) revealed that the improved performance for hybrid catalysts can be correlated with a modification of the acidic properties. In turn, acidity is determined by the quality of the dispersion of Al centers in the form of isolated sites in the hybrid silica matrix. All in all, this study establishes a "ranking" for a variety of organic groups in terms of their effect on gas-phase ethanol dehydration to ethylene; ethylene yield decreases in this order: bridging xylylene ≈ pendant methyl > pendant benzyl > bridging methylene ≈ inorganic benchmark (no organic groups) > bridging ethylene.<br>

Effect of Steam Treatment on Catalytic Performance of La2O3-HZSM-5 for Methylation of Toluene with Methanol

2012 ◽  
Vol 629 ◽  
pp. 381-385 ◽  
Author(s):  
Jun Hui Li ◽  
Zhong Hua Hu ◽  
Ya Nan Wang ◽  
Hao Xiang ◽  
Zhi Rong Zhu
Keyword(s):  
High Selectivity ◽  
Fixed Bed ◽  
Shape Selectivity ◽  
Catalytic Performance ◽  
Acid Sites ◽  
Fixed Bed Reactor ◽  
Steam Treatment ◽  
By Products ◽  
Poor Stability ◽  
Excellent Catalytic Performance

Methylation of toluene with methanol to synthesize p-Xylene was performed in a fixed-bed reactor. HZSM-5 zeolite as a catalyst was prepared by modification with La2O3. In addition, effect of steam treatment for La2O3-modified HZSM-5 on its catalytic performance was investigated as well. The properties of as-prepared catalysts were characterized by XRD, BET and NH3-TPD. The results indicate that modification with La2O3can narrow the size of HZSM-5 channel effectively. And more than 90% selectivity of p-Xylene is obtained over HZSM-5 with loading of 24% and 30% La2O3. However, above La2O3-modified HZSM-5 with high-selectivity exhibit a poor stability for time on-stream of the methylation reaction. Steam treatment of La2O3-modified HZSM-5 can improve its stability and shape selectivity, decreasing by-products. These effects can be attributed to distortion & narrowing of HZSM-5 channel and reduction of HZSM-5 strong Bronsted acid sites during steam treatment. As a result, the excellent catalytic performance is obtained over 24.0% La2O3-modified HZSM-5 by steam treatment at 773 K for 1.0 h, being 23% conversion of toluene, 93% selectivity of p-Xylene during time on-stream.

scholarly journals Catalytic Performance of Submicro ZSM-5 in Ethanol Dehydration to Ethylene at High Reaction Pressure

2014 ◽  
Vol 3 (3) ◽  
pp. 292-296 ◽  
Author(s):  
Xiangping Li ◽  
Hongpeng Zhang ◽  
Sen Lin ◽  
Yuan Fang ◽  
Hongchuan Xin ◽  
...  
Keyword(s):  
Catalytic Performance ◽  
Ethanol Dehydration ◽  
Reaction Pressure ◽  
High Reaction

Enhanced Catalytic Performances by Desilication and Subsequent Steam Treatment of ZSM-5 Zeolite

1996 ◽  
Vol 454 ◽  
Author(s):  
R. Le Van Mao ◽  
N. Borsuk ◽  
D. Ohayon ◽  
A. Ramsaran ◽  
S. T. Le ◽  
...  
Keyword(s):  
Acid Site ◽  
Subsequent Treatment ◽  
Steam Treatment ◽  
Acid Form ◽  
Ethanol Dehydration ◽  
Zeolite Framework ◽  
Site Density ◽  
Catalytic Performances

ABSTRACTControlled desilication of ZSM-5 zeolite increases the acid site density of its acid form. A subsequent treatment with steam at 300 °C results in a material with single-sized and slightly larger micropores when compared to the parent zeolite. This is likely the cause of a second increase of the yields of MTBE (methyl terbutyl ether) and ethylene when the steamed desilicated zeolite is used as catalyst in the MTBE synthesis and ethanol dehydration, respectively. Steam appears to be capable of “healing” the zeolite framework at a temperature much lower than that normally required when the desilicated ZSM-5 zeolite is solely heated in air.

scholarly journals Non-Hydrolytic Sol-Gel Route to a Family of Hybrid Mesoporous Aluminosilicate Ethanol Dehydration Catalysts

2020 ◽  
Author(s):  
Ales Styskalik ◽  
Imène Kordoghli ◽  
Claude Poleunis ◽  
Arnaud Delcorte ◽  
Denis Dochain ◽  
...  
Keyword(s):  
Gas Phase ◽  
Sol Gel ◽  
Catalytic Performance ◽  
Silica Matrix ◽  
Ethanol Dehydration ◽  
One Pot ◽  
Water Contact ◽  
Hybrid Silica ◽  
Mesoporous Aluminosilicate ◽  
Improved Performance

Organic-inorganic hybrid materials are nowadays intensely studied for potential applications in heterogeneous catalysis because their properties and catalytic behavior differ from pristine inorganic counterparts. The organic groups at the catalyst surface can modify not only its hydrophilicity, but also acidity, hydrothermal stability, porosity, etc. In some cases, such properties alteration leads to improved catalytic performance in terms of activity, selectivity, or stability. However, the choice of organic groups stays relatively narrow, as most reports focus on pendant methyl groups. Here, a series of mesoporous hybrid aluminosilicate materials containing various organic groups was prepared in one pot by non-hydrolytic sol-gel (NHSG). Both aromatic and aliphatic, pendant and bridging organic groups were incorporated. The presence of the organic groups in the bulk and at the outermost surface of the materials was verified by solid-state NMR and ToF-SIMS, respectively. Aluminum is mostly incorporated in tetrahedral coordination in the hybrid silica matrix. The organically modified mesoporous aluminosilicate samples were tested as catalysts in the gas phase ethanol dehydration (which relies on solid acids) and most of them outperformed the purely inorganic catalyst benchmark. While a direct influence of surface hydrophilicity or hydrophobicity (as probed by water sorption and water contact angle measurements) appeared unlikely, characterization of acidity (IR-pyridine) revealed that the improved performance for hybrid catalysts can be correlated with a modification of the acidic properties. In turn, acidity is determined by the quality of the dispersion of Al centers in the form of isolated sites in the hybrid silica matrix. All in all, this study establishes a "ranking" for a variety of organic groups in terms of their effect on gas-phase ethanol dehydration to ethylene; ethylene yield decreases in this order: bridging xylylene ≈ pendant methyl > pendant benzyl > bridging methylene ≈ inorganic benchmark (no organic groups) > bridging ethylene.<br>

Ultrastructure of Some Planktonic Formainifera

1974 ◽  
Vol 32 ◽  
pp. 190-191
Author(s):  
William H. Zucker
Keyword(s):  
Cell Biology ◽  
Water Mass ◽  
Planktonic Foraminifera ◽  
Uranyl Acetate ◽  
Ethanol Dehydration ◽  
Globigerinoides Ruber ◽  
Light Microscope Level ◽  
Globigerina Bulloides ◽  
Glutaraldehyde Solution ◽  
Diamond Knife

Planktonic foraminifera are widely-distributed and abundant zooplankters. They are significant as water mass indicators and provide evidence of paleotemperatures and events which occurred during Pleistocene glaciation. In spite of their ecological and paleological significance, little is known of their cell biology. There are few cytological studies of these organisms at the light microscope level and some recent reports of their ultrastructure.Specimens of Globigerinoides ruber, Globigerina bulloides, Globigerinoides conglobatus and Globigerinita glutinata were collected in Bermuda waters and fixed in a cold cacodylate-buffered 6% glutaraldehyde solution for two hours. They were then rinsed, post-fixed in Palade's fluid, rinsed again and stained with uranyl acetate. This was followed by graded ethanol dehydration, during which they were identified and picked clean of debris. The specimens were finally embedded in Epon 812 by placing each organism in a separate BEEM capsule. After sectioning with a diamond knife, stained sections were viewed in a Philips 200 electron microscope.

The significance of SEM in the diagnosis of haematopoietic malignancies

1978 ◽  
Vol 36 (2) ◽  
pp. 314-315
Author(s):  
Etienne de Harven ◽  
Nina Lampen
Keyword(s):  
Room Temperature ◽  
Culture Medium ◽  
Cell Attachment ◽  
Ethanol Dehydration ◽  
Moist Chamber ◽  
Efficient Alternative ◽  
Mononuclear Leucocytes ◽  
Fast Quenching ◽  
Freeze Dryer ◽  
Scanning Electron

Samples of heparinized blood, or bone marrow aspirates, or cell suspensions prepared from biopsied tissues (nodes, spleen, etc. ) are routinely prepared, after Ficoll-Hypaque concentration of the mononuclear leucocytes, for scanning electron microscopy. One drop of the cell suspension is placed in a moist chamber on a poly-l-lysine pretreated plastic coverslip (Mazia et al., J. Cell Biol. 66:198-199, 1975) and fifteen minutes allowed for cell attachment. Fixation, started in 2. 5% glutaraldehyde in culture medium at room temperature for 30 minutes, is continued in the same fixative at 4°C overnight or longer. Ethanol dehydration is immediately followed by drying at the critical point of CO2 or of Freon 13. An efficient alternative method for ethanol dehydrated cells is to dry the cells at low temperature (-75°C) under vacuum (10-2 Torr) for 30 minutes in an Edwards-Pearse freeze-dryer (de Harven et al., SEM/IITRI/1977, 519-524). This is preceded by fast quenching in supercooled ethanol (between -90 and -100°C).

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