ChemInform Abstract: Crystal Phase, Spectral Features, and Catalytic Activity of Sulfate- Doped Zirconia Systems.

ChemInform ◽  
2010 ◽  
Vol 27 (7) ◽  
pp. no-no
Author(s):  
C. MORTERRA ◽  
G. CERRATO ◽  
F. PINNA ◽  
M. SIGNORETTO
Keyword(s):  
Catalytic Activity ◽  
Crystal Phase ◽  
Spectral Features

Crystal Phase, Spectral Features, and Catalytic Activity of Sulfate-Doped Zirconia Systems

1995 ◽  
Vol 157 (1) ◽  
pp. 109-123 ◽  
Author(s):  
C. Morterra ◽  
G. Cerrato ◽  
F. Pinna ◽  
M. Signoretto
Keyword(s):  
Catalytic Activity ◽  
Crystal Phase ◽  
Spectral Features

Catalytic Activity of Manganese Oxide Anchored on to Alumina and Zirconia for the Synthesis of Dihydropyrimidinones: Role of Acidity, Crystal Phase and Morphology

2014 ◽  
Vol 3 (1) ◽  
pp. 88-102 ◽  
Author(s):  
Mahadevaiah Rekha ◽  
Hagalahalli Hareesh ◽  
Nagaraju Kathyayini ◽  
Narasimaiah Nagaraju
Keyword(s):  
Catalytic Activity ◽  
Manganese Oxide ◽  
Crystal Phase

scholarly journals Effects of metallic cobalt crystal phase on catalytic activity of cobalt catalysts supported on carbon nanotubes in Fischer–Tropsch synthesis

2019 ◽  
Vol 44 (4) ◽  
pp. 316-323 ◽  
Author(s):  
Ali Nakhaei Pour ◽  
Mohammadreza Housaindokht
Keyword(s):  
Catalytic Activity ◽  
Cobalt Catalysts ◽  
Crystal Phase ◽  
Microemulsion System ◽  
Face Centered Cubic ◽  
Metallic Cobalt ◽  
Fischer Tropsch ◽  
Fischer Tropsch Synthesis ◽  
Hexagonal Close Packed ◽  
Face Centered

The effects of metallic cobalt crystal phase on catalytic activity of cobalt catalysts in the Fischer–Tropsch synthesis were investigated in a continuous spinning basket reactor. The cobalt catalysts were prepared by impregnation of the cobalt active phase in a microemulsion system on multiwall carbon nanotube supports. A series of cobalt catalysts with different Co particle sizes was prepared by variation of the water-to-surfactant molar ratio from 2 to 12 in the microemulsion system. The X-ray diffraction results validate a complex composition of cobalt phases containing cobalt oxides and metallic cobalt with hexagonal close-packed and face-centered cubic phases. The results show that larger cobalt particles exhibit more face-centered cubic and less hexagonal close-packed metallic cobalt. The experimental results show that the catalysts with higher fractions of hexagonal close-packed phase exhibited higher conversion in the Fischer–Tropsch reaction.

Synthesis, Characterization and Kinetic Evaluation of Manganese Oxide Nanoparticles for the H2O2 Catalytic Decomposition

2008 ◽  
Vol 6 (1) ◽  
Author(s):  
Manuel D Delgado Vigil ◽  
Francisco Paraguay Delgado ◽  
Virginia Collins Martínez ◽  
Alejandro López Ortiz
Keyword(s):  
Particle Size ◽  
Catalytic Activity ◽  
Manganese Oxides ◽  
Catalytic Decomposition ◽  
Intrinsic Rate ◽  
Xrd Analysis ◽  
Crystal Phase ◽  
Bet Surface Area ◽  
Synthesis Process ◽  
Kinetic Evaluation

Nanostructured manganese oxides were synthesized towards the catalytic decomposition of hydrogen peroxide. The effect of the type of precipitant (Na2CO3 and NH4OH) over the particle size and crystallographic phase was determined. Also, the influence of particle size and crystal phase over the catalytic activity was established. Characterization of the obtained nanoparticles was performed through XRD analysis, BET surface area and TEM microscopy. Catalytic activity was followed through gasometry of the oxygen evolution [H2O2(l) ? H2O(l) + O2 (g)] at 25°C. Na2CO3 (Mn-1) and NH4OH (Mn-2) precipitants produced nanoparticles with average sizes of 5-10 nm and 20 nm, respectively. This result was attributed to higher pH stability of precipitant Na2CO3 during the synthesis process. XRD results revealed the presence of ß-MnO2, Mn5O8 and Mn3O4 crystal phase mixture for Mn-1 and Mn5O8 for Mn-2 catalyst. Catalytic activity resulted in intrinsic rate constants (kint = min-1m-2) of 5.2 and 2.3 for Mn-1 and Mn-2, respectively. The greater catalytic activity of Mn-2 catalyst was attributed to the presence of the Mn55O8 phase.

Effect of Ru crystal phase on the catalytic activity of hydrolytic dehydrogenation of ammonia borane

2018 ◽  
Vol 396 ◽  
pp. 148-154 ◽  
Author(s):  
Guozhu Chen ◽  
Ruyue Wang ◽  
Wei Zhao ◽  
Baotao Kang ◽  
Daowei Gao ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Ammonia Borane ◽  
Crystal Phase

High resolution electron microscopy of lanthanum phosphate crystals

1978 ◽  
Vol 36 (1) ◽  
pp. 274-275
Author(s):  
J. C. Wheatley ◽  
J. M. Cowley
Keyword(s):  
Electron Microscopy ◽  
Catalytic Activity ◽  
High Resolution ◽  
Petroleum Industry ◽  
High Resolution Electron Microscopy ◽  
Lanthanum Phosphate ◽  
Good Catalyst ◽  
Resolution Electron ◽  
Good Catalytic Activity ◽  
Physical And Chemical

Rare-earth phosphates are of particular interest because of their catalytic properties associated with the hydrolysis of many aromatic chlorides in the petroleum industry. Lanthanum phosphates (LaPO4) which have been doped with small amounts of copper have shown increased catalytic activity (1). However the physical and chemical characteristics of the samples leading to good catalytic activity are not known.Many catalysts are amorphous and thus do not easily lend themselves to methods of investigation which would include electron microscopy. However, the LaPO4, crystals are quite suitable samples for high resolution techniques.The samples used were obtained from William L. Kehl of Gulf Research and Development Company. The electron microscopy was carried out on a JEOL JEM-100B which had been modified for high resolution microscopy (2). Standard high resolution techniques were employed. Three different sample types were observed: 669A-1-5-7 (poor catalyst), H-L-2 (good catalyst) and 27-011 (good catalyst).

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

2019 ◽  
Vol 9 (3) ◽  
pp. 811-821 ◽  
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.

Prolonged Expression of Procoagulant Activity of Human Platelets Degranulated by Thrombin

1995 ◽  
Vol 74 (03) ◽  
pp. 958-961 ◽  
Author(s):  
Raelene L Kinlough-Rathbone ◽  
Dennis W Perry
Keyword(s):  
Catalytic Activity ◽  
Thrombus Formation ◽  
Annexin V ◽  
Human Platelets ◽  
Procoagulant Activity ◽  
Prothrombinase Complex ◽  
Arterial Thrombus ◽  
Flowing Blood

SummaryPlatelets are exposed to thrombin when they take part in arterial thrombus formation, and they may return to the circulation when they are freed by fibrinolysis and dislodged by flowing blood. Thrombin causes the expression of procoagulant activity on platelets, and if this activity persists, the recirculating platelets may contribute to subsequent thrombosis. We have developed techniques to degranulate human platelets by treatment with thrombin, and recover them as single, discrete platelets that aggregate in response to both weak and strong agonists. In the present study we examined the duration of procoagulant activity on the surface of thrombin-degranulated platelets by two methods: a prothrombinase assay, and the binding of 125I-labeled annexin. Control platelets generated 0.9 ± 0.4 U thrombin per 107 platelets in 15 min. Suspensions of thrombin-degranulated platelets formed 5.4 ± 0.1 U thrombin per 107 platelets in this time. Binding of 125I-annexin V was also greater with thrombin-treated platelets than with control platelets (controls: 1.7 ±0.1 ng annexin/107 platelets; thrombin-degranulated platelets: 6.8 ± 0.2 ng annexin/107 platelets). With thrombin-degranulated platelets, increased procoagulant activity and annexin binding persisted for at least 4 h after degranulation and resuspension, indicating that the catalytic activity for the prothrombinase complex is not reversed during this time. These platelets maintained their ability to aggregate for 4 h, even in response to the weak agonist, ADP. Thus, platelets that have taken part in thrombus formation and returned to the circulation may contribute to the promotion of further thrombotic events because of the persistence of procoagulant activity on their surface.

Enhanced catalytic activity of low-Pt content nanocatalysts supported on hollow carbon spheres for the ORR in alkaline media

MRS Advances ◽  
2020 ◽  
Vol 5 (57-58) ◽  
pp. 2961-2972
Author(s):  
P.C. Meléndez-González ◽  
E. Garza-Duran ◽  
J.C. Martínez-Loyola ◽  
P. Quintana-Owen ◽  
I.L. Alonso-Lemus ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Anion Exchange ◽  
Average Particle Size ◽  
Synthesis Method ◽  
Alkaline Media ◽  
High Catalytic Activity ◽  
Average Particle ◽  
Carbon Spheres ◽  
Hollow Carbon ◽  
Hollow Carbon Spheres

In this work, low-Pt content nanocatalysts (≈ 5 wt. %) supported on Hollow Carbon Spheres (HCS) were synthesized by two routes: i) colloidal conventional polyol, and ii) surfactant-free Bromide Anion Exchange (BAE). The nanocatalysts were labelled as Pt/HCS-P and Pt/HCS-B for polyol and BAE, respectively. The physicochemical characterization of the nanocatalysts showed that by following both methods, a good control of chemical composition was achieved, obtaining in addition well dispersed nanoparticles of less than 3 nm TEM average particle size (d) on the HCS. Pt/HCS-B contained more Pt0 species than Pt/HCS-P, an effect of the synthesis method. In addition, the structure of the HCS remains more ordered after BAE synthesis, compared to polyol. Regarding the catalytic activity for the Oxygen Reduction Reaction (ORR) in 0.5 M KOH, Pt/HCS-P and Pt/HCS-B showed a similar performance in terms of current density (j) at 0.9 V vs. RHE than the benchmark commercial 20 wt. % Pt/C. However, Pt/HCS-P and Pt/HCS-B demonstrated a 6 and 5-fold increase in mass catalytic activity compared to Pt/C, respectively. A positive effect of the high specific surface area of the HCS and its interactions with metal nanoparticles and electrolyte, which promoted the mass transfer, increased the performance of Pt/HCS-P and Pt/HCS-B. The high catalytic activity showed by Pt/HCS-B and Pt/HCS-P for the ORR, even with a low-Pt content, make them promising cathode nanocatalysts for Anion Exchange Membrane Fuel Cells (AEMFC).

Catalytic Activity of Binary and Triple Systems Based on Redox Inactive Metal Compound, LiSt and Additives of Monodentate Ligands-Modifiers: DMF, HMPA and PhOH, in Selective Ethylbenzene Oxidation with Dioxygen

2016 ◽  
Vol 10 (3) ◽  
pp. 259-270
Author(s):  
Ludmila Matienko ◽  
◽  
Larisa Mosolova ◽  
Vladimir Binyukov ◽  
Gennady Zaikov ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Triple System ◽  
Metal Compound ◽  
Ethylbenzene Oxidation ◽  
Catalytic Systems ◽  
Triple Systems ◽  
Lithium Compound ◽  
Mechanism Of Catalysis ◽  
Monodentate Ligands

Mechanism of catalysis with binary and triple catalytic systems based on redox inactive metal (lithium) compound {LiSt+L2} and {LiSt+L2+PhOH} (L2=DMF or HMPA), in the selective ethylbenzene oxidation by dioxygen into -phenylethyl hydroperoxide is researched. The results are compared with catalysis by nickel-lithium triple system {NiII(acac)2+LiSt+PhOH} in selective ethylbenzene oxidation to PEH. The role of H-bonding in mechanism of catalysis is discussed. The possibility of the stable supramolecular nanostructures formation on the basis of triple systems, {LiSt+L2+PhOH}, due to intermolecular H-bonds, is researched with the AFM method.

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