Iron Uniform-Size Nanoparticles Dispersed on MCM-41 Used as Hydrocarbon Synthesis Catalyst

Author(s):  
S. G. Marchetti ◽  
M. V. Cagnoli ◽  
A. M. Alvarez ◽  
J. F. Bengoa ◽  
N. G. Gallegos ◽  
...  
2006 ◽  
Vol 6 (11) ◽  
pp. 3442-3445
Author(s):  
Jeong-Rae Ko ◽  
Wha-Seung Ahn

MWNTs (multi-walled carbon nanotubes) were made by catalytic CVD process using iron-containing mesoporous silica, Fe-MCM-41, with 4 mol% Fe loading prepared by direct synthesis route. Uniform 5 nm size Fe2O3 nano-particles impregnated onto a mesoporous silica support, SBA-15 were also prepared for CNTs synthesis. The catalysts were characterized using XRD, SEM/TEM, N2 physisorption, UV-vis diffuse reflectance and FT-IR spectroscopies. Acetylene gas was introduced as a carbon source, and the gas mixture of Ar:H2:C2H2 = 14:5:1 pyrolyzed at 750 °C for 60 min was found to be the optimum synthesis condition. Fe-MCM-41 due to higher dispersion of nano-sized Fe-species was efficient as catalyst for MWNTs with more uniform size distribution. Cobalt-impregnated Fe-MCM-41 (Co/Fe = 1) produced a small fraction of SWNTs of ca. 2 nm diameter mixed with MWNTs.


2011 ◽  
Vol 10 (04n05) ◽  
pp. 1131-1135 ◽  
Author(s):  
H. SHANKAR ◽  
R. SARAVANAN ◽  
A. STEPHEN ◽  
V. NARAYANAN

Nanocrystalline titanium dioxide, TiO2 , is a well studied and commonly used material for photocatalytic applications. However, the control of particle size, monodispersity, large catalytic surface for sufficient adsorption of organic pollutants, recovery and recycle of TiO2 nanoparticles are challenging tasks. Hence in this work, titania has been introduced into the nanopores (2–10 nm size) of MCM-41 to produce stable nanoparticles of uniform size and shape. Further, the photocatalytic efficiency can be improved by lengthening the life time of the excited electrons/holes during photoreaction. This could be achieved by incorporating molybdenum in to the MCM-41 silica matrix in addition to titania loading. In the present study, the synthesis and the photocatlaytic efficiency of a new photocatalyst TiO2@Mo -MCM-41 (25 wt.% TiO2 loaded Mo incorporated MCM-41) are reported. Mo -MCM-41, with different ratios of Si to Mo ( Si/Mo = 25,50,75), is synthesized by hydrothermal method and loaded with 25 wt.% TiO2 using sol–gel method. The photocatalytic activity of the prepared samples was evaluated using methyl orange as a model organic compound. X-ray diffraction (XRD), Transmission Electron Microscopy (TEM) and nitrogen adsorption–desorption isotherm (BET analysis) measurements were used to investigate the effects of the incorporated elements in the structure of MCM-41. It was found that the photodegradation ability of 25% TiO2 loaded Mo -MCM-41 was highly related to the amount of Mo atoms present in the sample with the optimum atomic ratio of Si to Mo being 50.


Author(s):  
C. J. Chan ◽  
K. R. Venkatachari ◽  
W. M. Kriven ◽  
J. F. Young

Dicalcium silicate (Ca2SiO4) is a major component of Portland cement. It has also been investigated as a potential transformation toughener alternative to zirconia. It has five polymorphs: α, α'H, α'L, β and γ. Of interest is the β-to-γ transformation on cooling at about 490°C. This transformation, accompanied by a 12% volume increase and a 4.6° unit cell shape change, is analogous to the tetragonal-to-monoclinic transformation in zirconia. Due to the processing methods used, previous studies into the particle size effect were limited by a wide range of particle size distribution. In an attempt to obtain a more uniform size, a fast quench rate involving a laser-melting/roller-quenching technique was investigated.The laser-melting/roller-quenching experiment used precompacted bars of stoichiometric γ-Ca2SiO4 powder, which were synthesized from AR grade CaCO3 and SiO2xH2O. The raw materials were mixed by conventional ceramic processing techniques, and sintered at 1450°C. The dusted γ-Ca2SiO4 powder was uniaxially pressed into 0.4 cm x 0.4 cm x 4 cm bars under 34 MPa and cold isostatically pressed under 172 MPa. The γ-Ca2SiO4 bars were melted by a 10 KW-CO2 laser.


2019 ◽  
Vol 9 (3) ◽  
pp. 811-821 ◽  
Author(s):  
Zhao-Meng Wang ◽  
Li-Juan Liu ◽  
Bo Xiang ◽  
Yue Wang ◽  
Ya-Jing Lyu ◽  
...  

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


2000 ◽  
Vol 10 (PR7) ◽  
pp. Pr7-99-Pr7-102 ◽  
Author(s):  
G. Dosseh ◽  
D. Morineau ◽  
C. Alba-Simionesco
Keyword(s):  

2000 ◽  
Vol 10 (PR7) ◽  
pp. Pr7-95-Pr7-98 ◽  
Author(s):  
D. Morineau ◽  
F. Casas ◽  
C. Alba-Simionesco ◽  
A. Grosman ◽  
M.-C. Bellissent-Funel ◽  
...  

TAPPI Journal ◽  
2013 ◽  
Vol 12 (3) ◽  
pp. 17-23 ◽  
Author(s):  
WANHEE IM ◽  
HAK LAE LEE ◽  
HYE JUNG YOUN ◽  
DONGIL SEO

Preflocculation of filler particles before their addition to pulp stock provides the most viable and practical solution to increase filler content while minimizing strength loss. The characteristics of filler flocs, such as floc size and structure, have a strong influence on preflocculation efficiency. The influence of flocculant systems on the structural characteristics of filler flocs was examined using a mass fractal analysis method. Mass fractal dimensions of filler flocs under high shear conditions were obtained using light diffraction spectroscopy for three different flocculants. A single polymer (C-PAM), a dual cationic polymer (p-DADMAC/C-PAM) and a C-PAM/micropolymer system were used as flocculants, and their effects on handsheet properties were investigated. The C-PAM/micropolymer system gave the greatest improvement in tensile index. The mass fractal analysis showed that this can be attributed to the formation of highly dense and spherical flocs by this flocculant. A cross-sectional analysis of the handsheets showed that filler flocs with more uniform size were formed when a C-PAM/micropolymer was used. The results suggest that a better understanding of the characteristics of preflocculated fillers and their influence on the properties of paper can be gained based on a fractal analysis.


2020 ◽  
Vol 8 (1) ◽  
pp. 11-24
Author(s):  
Wei Xiong ◽  
Ping Cheng ◽  
Zhiyuan Ma ◽  
Xiaojun Quan ◽  
Wei Yao

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