TS-1 Zeolite with Homogeneous Distribution of Ti Atoms in the Framework: Synthesis, Crystallization Mechanism and its Catalytic Performance

The structure–property relationship of catalytic supports for the deposition of redox-active transition metals is of great importance for improving the catalytic efficiency and reusability of the catalysts. In this work, the role of alumina support precursors of Cu-Fe/Al2O3 catalysts used for the total oxidation of toluene as a model volatile organic air pollutant is elucidated. Surface characterization of the catalysts revealed that the surface area, pore volume and acid site concentration of the alumina supports are important but not the determining factors for the catalytic activity of the studied catalysts for this type of reaction. The determining factors are the structural order of the support precursor, the homogeneous distribution of the catalytic sites and reducibility, which were elucidated by XRD, NMR, TEM and temperature programed reduction (TPR). Cu–Fe/Al2O3 prepared from bayerite and pseudoboehmite as highly ordered precursors showed better catalytic performance compared to Cu-Fe/Al2O3 derived from the amorphous alumina precursor and dawsonite. Homogeneous distribution of FexOy and CuOx with defined Cu/Fe molar ratio on the Al2O3 support is required for the efficient catalytic performance of the material. The study showed a beneficial effect of low iron concentration introduced into the alumina precursor during the alumina support synthesis procedure, which resulted in a homogeneous metal oxide distribution on the support.

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Thermal Modification Effect on Supported Cu-Based Activated Carbon Catalyst in Hydrogenolysis of Glycerol

Materials ◽

10.3390/ma13030603 ◽

2020 ◽

Vol 13 (3) ◽

pp. 603 ◽

Cited By ~ 1

Author(s):

Juan Seguel ◽

Rafael García ◽

Ricardo José Chimentão ◽

José Luis García-Fierro ◽

I. Tyrone Ghampson ◽

...

Keyword(s):

Activated Carbon ◽

Specific Surface ◽

Hydrogen Adsorption ◽

Carbon Support ◽

Catalytic Performance ◽

Homogeneous Distribution ◽

Surface Groups ◽

Carbon Supports ◽

Surface Areas ◽

Oxygen Surface

Glycerol hydrogenolysis to 1,2-propanediol (1,2-PDO) was performed over activated carbon supported copper-based catalysts. The catalysts were prepared by impregnation using a pristine carbon support and thermally-treated carbon supports (450, 600, 750, and 1000 °C). The final hydrogen adsorption capacity, porous structure, and total acidity of the catalysts were found to be important descriptors to understand catalytic performance. Oxygen surface groups on the support controlled copper dispersion by modifying acidic and adsorption properties. The amount of oxygen species of thermally modified carbon supports was also found to be a function of its specific surface area. Carbon supports with high specific surface areas contained large amount of oxygen surface species, inducing homogeneous distribution of Cu species on the carbon support during impregnation. The oxygen surface groups likely acted as anchorage centers, whereby the more stable oxygen surface groups after the reduction treatment produced an increase in the interaction of the copper species with the carbon support, and determined catalytic performances.

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Metal Chlorides Grafted on SAPO-5 (MClx/SAPO-5) as Reusable and Superior Catalysts for Acylation of 2-Methylfuran Under Non-Microwave Instant Heating Condition

Processes ◽

10.3390/pr8050603 ◽

2020 ◽

Vol 8 (5) ◽

pp. 603

Author(s):

Ismail Alhassan Auwal ◽

Ka-Lun Wong ◽

Tau Chuan Ling ◽

Boon Seng Ooi ◽

Eng-Poh Ng

Keyword(s):

Thermochemical Treatment ◽

Nitrogen Adsorption ◽

Catalytic Performance ◽

Acid Sites ◽

Homogeneous Distribution ◽

Covalent Bonds ◽

Metal Chlorides ◽

Promising Alternative ◽

Highly Active ◽

Catalyst Reusability

Highly active metal chlorides grafted on silicoaluminophosphate number 5, MClx/SAPO-5 (M = Cu, Co, Sn, Fe and Zn) catalysts via simple grafting of respective metal chlorides (MClx) onto SAPO-5 are reported. The study shows that thermochemical treatment after grafting is essential to ensure the formation of chemical bondings between MClx and SAPO-5. In addition, the microscopy, XRD and nitrogen adsorption analyses reveal the homogeneous distribution of MClx species on the SAPO-5 surface. Furthermore, the elemental microanalysis confirms the formation of Si–O–M covalent bonds in ZnClx/SAPO-5, SnClx/SAPO-5 and FeClx/SAPO-5 whereas only dative bondings are formed in CoClx/SAPO-5 and CuClx/SAPO-5. The acidity of MClx/SAPO-5 is also affected by the type of metal chloride grafted. Thus, their catalytic behavior is evaluated in the acid-catalyzed acylation of 2-methylfuran under novel non-microwave instant heating conditions (90–110 °C, 0–20 min). ZnClx/SAPO-5, which has the largest amount of acidity (mainly Lewis acid sites), exhibits the best catalytic performance (94.5% conversion, 100% selective to 2-acetyl-5-methylfuran) among the MClx/SAPO-5 solids. Furthermore, the MClx/SAPO-5 solids, particularly SnClx/SAPO-5, FeClx/SAPO-5 and ZnClx/SAPO-5, also show more superior catalytic performance than common homogeneous acid catalysts (H2SO4, HNO3, CH3COOH, FeCl3, ZnCl2) with higher reactant conversion and catalyst reusability, thus offering a promising alternative for the replacement of hazardous homogeneous catalysts in Friedel–Crafts reactions.

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Crystallization mechanism and catalytic performance of TS-1 synthesized by an aerosol-assisted method

CrystEngComm ◽

10.1039/c7ce00364a ◽

2017 ◽

Vol 19 (19) ◽

pp. 2695-2701 ◽

Cited By ~ 6

Author(s):

Zhendong Guo ◽

Guang Xiong ◽

Liping Liu ◽

Wancang Song ◽

Qianying Jia

Keyword(s):

Catalytic Performance ◽

Crystallization Mechanism

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CHA-Type Zeolite Prepared by Interzeolite Conversion Method Using FAU and LTL-Type Zeolite: Effect of the Raw Materials on the Crystallization Mechanism, and Physicochemical and Catalytic Properties

Catalysts ◽

10.3390/catal10101204 ◽

2020 ◽

Vol 10 (10) ◽

pp. 1204

Author(s):

Toshiki Nishitoba ◽

Takuya Nozaki ◽

Sungsik Park ◽

Yong Wang ◽

Junko N. Kondo ◽

...

Keyword(s):

Catalytic Properties ◽

Raw Materials ◽

Ammonium Hydroxide ◽

Catalytic Performance ◽

High Thermal Stability ◽

Crystallization Mechanism ◽

Raw Material ◽

Organic Structure ◽

Type Zeolite ◽

Low Solubility

The effect of the raw materials including parent zeolite as aluminosilicate sources and organic structure-directing agents (OSDAs) on the crystallization mechanism, and physicochemical and catalytic properties of the CHA-type aluminosilicate zeolite was investigated. For this purpose, the FAU-type and the LTL-type zeolites were used as raw material, and trymethyladamantyl ammonium hydroxide and tetraethyl ammonium hydroxide were used as OSDAs. We firstly found that the CHA-type aluminosilicate zeolite was crystallized from the combination of the LTL-type zeolite and tetraethyl ammonium hydroxide as raw materials. The crystallization behaviors were also monitored in detail. The crystallization was delayed by using the LTL-type zeolite as the starting material regardless of the type of OSDA because of the low solubility of the LTL-type zeolite compared to the FAU-type zeolite. We have found that the Al distribution in the CHA framework was dependent on the raw materials. Thus, the prepared CHA-type aluminosilicate zeolite from the LTL-type zeolite exhibited a high thermal stability and catalytic performance in the methanol to olefins reaction.

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Collagen fibrillogenesis in vitro: interaction of types I and V collagen

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100142670 ◽

1986 ◽

Vol 44 ◽

pp. 210-211

Author(s):

Arthur J. Wasserman ◽

Kathy C. Kloos ◽

David E. Birk

Keyword(s):

Type I Collagen ◽

Corneal Stroma ◽

Minor Component ◽

Homogeneous Distribution ◽

Type I ◽

Type V Collagen ◽

Fibril Morphology ◽

Type V ◽

In Vitro Interaction

Type I collagen is the predominant collagen in the cornea with type V collagen being a quantitatively minor component. However, the content of type V collagen (10-20%) in the cornea is high when compared to other tissues containing predominantly type I collagen. The corneal stroma has a homogeneous distribution of these two collagens, however, immunochemical localization of type V collagen requires the disruption of type I collagen structure. This indicates that these collagens may be arranged as heterpolymeric fibrils. This arrangement may be responsible for the control of fibril diameter necessary for corneal transparency. The purpose of this work is to study the in vitro assembly of collagen type V and to determine whether the interactions of these collagens influence fibril morphology.

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The design and catalytic performance of molybdenum active sites on an MCM-41 framework for the aerobic oxidation of 5-hydroxymethylfurfural to 2,5-diformylfuran

Catalysis Science & Technology ◽

10.1039/c8cy02291g ◽

2019 ◽

Vol 9 (3) ◽

pp. 811-821 ◽

Cited By ~ 7

Author(s):

Zhao-Meng Wang ◽

Li-Juan Liu ◽

Bo Xiang ◽

Yue Wang ◽

Ya-Jing Lyu ◽

...

Keyword(s):

Catalytic Activity ◽

Active Sites ◽

Aerobic Oxidation ◽

Catalytic Performance ◽

Mcm 41

The catalytic activity decreases as –(SiO)3Mo(OH)(O) > –(SiO)2Mo(O)2 > –(O)4–MoO.

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Optimizing electron density of nickel sulfide electrocatalysts through sulfur vacancy engineering for alkaline hydrogen evolution

Journal of Materials Chemistry A ◽

10.1039/d0ta05594h ◽

2020 ◽

Vol 8 (35) ◽

pp. 18207-18214

Author(s):

Dongbo Jia ◽

Lili Han ◽

Ying Li ◽

Wenjun He ◽

Caichi Liu ◽

...

Keyword(s):

Hydrogen Evolution ◽

Electron Density ◽

Rational Design ◽

Nickel Sulfide ◽

Catalytic Performance ◽

Sulfide Catalysts ◽

Sulfur Vacancy

A novel, rational design for porous S-vacancy nickel sulfide catalysts with remarkable catalytic performance for alkaline HER.

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Catalytic Resonance Theory: Parallel Reaction Pathway Control

10.26434/chemrxiv.10271090 ◽

2019 ◽

Author(s):

M. Alexander Ardagh ◽

Manish Shetty ◽

Anatoliy Kuznetsov ◽

Qi Zhang ◽

Phillip Christopher ◽

...

Keyword(s):

Chemical Reactions ◽

Active Site ◽

Active Sites ◽

Reaction Pathway ◽

Control Strategies ◽

Oscillation Amplitude ◽

Catalytic Performance ◽

Parallel Reaction ◽

Resonance Theory ◽

Static Conditions

Catalytic enhancement of chemical reactions via heterogeneous materials occurs through stabilization of transition states at designed active sites, but dramatically greater rate acceleration on that same active site is achieved when the surface intermediates oscillate in binding energy. The applied oscillation amplitude and frequency can accelerate reactions orders of magnitude above the catalytic rates of static systems, provided the active site dynamics are tuned to the natural frequencies of the surface chemistry. In this work, differences in the characteristics of parallel reactions are exploited via selective application of active site dynamics (0 < ΔU < 1.0 eV amplitude, 10<sup>-6</sup> < f < 10<sup>4</sup> Hz frequency) to control the extent of competing reactions occurring on the shared catalytic surface. Simulation of multiple parallel reaction systems with broad range of variation in chemical parameters revealed that parallel chemistries are highly tunable in selectivity between either pure product, even when specific products are not selectively produced under static conditions. Two mechanisms leading to dynamic selectivity control were identified: (i) surface thermodynamic control of one product species under strong binding conditions, or (ii) catalytic resonance of the kinetics of one reaction over the other. These dynamic parallel pathway control strategies applied to a host of chemical conditions indicate significant potential for improving the catalytic performance of many important industrial chemical reactions beyond their existing static performance.

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Gamma knife surgery for vestibular schwannoma: 10-year experience of 195 cases

Journal of Neurosurgery ◽

10.3171/sup.2005.102.s_supplement.0087 ◽

2005 ◽

Vol 102 (Special_Supplement) ◽

pp. 87-97 ◽

Cited By ~ 19

Author(s):

Wen-Yuh Chung ◽

Kang-Du Liu ◽

Cheng-Ying Shiau ◽

Hsiu-Mei Wu ◽

Ling-Wei Wang ◽

...

Keyword(s):

Mr Imaging ◽

Gamma Knife ◽

Vestibular Schwannoma ◽

Tumor Volume ◽

Radiation Effect ◽

Gamma Knife Surgery ◽

Homogeneous Distribution ◽

Content Type ◽

Fine Print

Object. The authors conducted a study to determine the optimal radiation dose for vestibular schwannoma (VS) and to examine the histopathology in cases of treatment failure for better understanding of the effects of irradiation. Methods. A retrospective study was performed of 195 patients with VS; there were 113 female and 82 male patients whose mean age was 51 years (range 11–82 years). Seventy-two patients (37%) had undergone partial or total excision of their tumor prior to gamma knife surgery (GKS). The mean tumor volume was 4.1 cm3 (range 0.04–23.1 cm3). Multiisocenter dose planning placed a prescription dose of 11 to 18.2 Gy on the 50 to 94% isodose located at the tumor margin. Clinical and magnetic resonance (MR) imaging follow-up evaluations were performed every 6 months. A loss of central enhancement was demonstrated on MR imaging in 69.5% of the patients. At the latest MR imaging assessment decreased or stable tumor volume was demonstrated in 93.6% of the patients. During a median follow-up period of 31 months resection was avoided in 96.8% of cases. Uncontrolled tumor swelling was noted in five patients at 3.5, 17, 24, 33, and 62 months after GKS, respectively. Twelve of 20 patients retained serviceable hearing. Two patients experienced a temporary facial palsy. Two patients developed a new trigeminal neuralgia. There was no treatment-related death. Histopathological examination of specimens in three cases (one at 62 months after GKS) revealed a long-lasting radiation effect on vessels inside the tumor. Conclusions. Radiosurgery had a long-term radiation effect on VSs for up to 5 years. A margin 12-Gy dose with homogeneous distribution is effective in preventing tumor progression, while posing no serious threat to normal cranial nerve function.

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