Evaluating and understanding the hydrothermal stability of alumina aerogel doped with yttrium oxide and used as a catalyst support for the thermo-catalytic cracking (TCC) process

2008 ◽  
Vol 86 (2) ◽  
pp. 146-160 ◽  
Author(s):  
Nabil Al-Yassir ◽  
Raymond Le Van Mao
Keyword(s):  
Catalytic Cracking ◽  
Surface Defects ◽  
Sol Gel ◽  
Catalyst Support ◽  
Supercritical Drying ◽  
Hydrothermal Stability ◽  
Oh Groups ◽  
Gel Method ◽  
Sol Gel Method ◽  
Alumina Aerogel

The current work presents results concerning the hydrothermal stability of yttria-doped alumina aerogel, which was prepared by the sol–gel method using a supercritical drying technique. The influence of atmospheric steam at 750 and 1000 °C on the rate of sintering of yttria-doped alumina aerogel with various yttria contents was investigated. BET N2 adsorption measurements, X-ray diffraction, thermogravimetric analysis, FTIR of adsorbed pyridine, and 1H and 27Al MAS NMR were used for characterization of solid samples. It was found that the hydrothermal stability of yttria-doped alumina aerogel was greatly improved compared with alumina aerogel and conventional alumina. This was evident from the decrease in the loss of surface area and pore volume, and the minimization of structural transformations. These significant improvements were attributed to the combined effect of sol–gel method and the presence of yttrium ions. Yttria-doped alumina aerogel with various yttria loadings, when compared with undoped alumina aerogel, exhibited lower concentrations of surface –OH groups, higher amounts of bridged –OH groups, and lower degrees of crystallinity with smaller particle sizes. It was also observed that the thermal and hydrothermal stabilities of both yttria-impregnated alumina aerogel and conventional alumina were improved but to a much lower extent. These improvements were attributed to the presence of yttria, and subsequently the formation of surface yttrium aluminate. This structure was found to be more thermally stable than bare alumina owing to the presence of less surface defects and –OH groups. Therefore, it was concluded that to observe the most effective role of yttria, it is quite essential to incorporate it into the alumina structure via the sol–gel technique.Key words: thermo-catalytic cracking (TCC), yttria-doped alumina aerogel, yttria-impregnated alumina, hydrothermal stability, surface –OH groups, Lewis sites.

scholarly journals Catalytic myrtenol amination over gold, supported on alumina doped with ceria and zirconia

2018 ◽  
Vol 5 (1) ◽  
pp. 49-58 ◽  
Author(s):  
Yu.S. Demidova ◽  
I.L. Simakova ◽  
E.V. Suslov ◽  
K.P. Volcho ◽  
N.F. Salakhutdinov ◽  
...  
Keyword(s):  
Metal Oxides ◽  
Sol Gel ◽  
Gold Catalyst ◽  
Catalyst Support ◽  
Acid Sites ◽  
One Pot ◽  
Gel Method ◽  
Sol Gel Method ◽  
Alcohol Activation ◽  
The One

Abstract In the current work gold catalysts supported on both commercial oxides and oxides synthesized by the sol-gel method were used for the one-pot alcohol amination of myrtenol. In general, utilization of metal oxides synthesized by the sol-gel method as the gold catalyst support enhanced the knowledge regarding key parameters determining catalytic behavior. Synthesized alumina was characterized by stronger acid sites favoring primary amine accumulation on the catalyst surface, as compared to the commercial oxide. Utilization of mixed metal oxides synthesized by the sol-gel method resulted in the non-additive behavior of different oxides enhancing the catalytic activity. Introduction of ceria into alumina modified the support basicity resulting in more efficient alcohol activation.

Influence of Stabilizer on the Microstructures and Photocatalytic Performance of ZnO Nanopowder Synthesized by Sol-Gel Method

2017 ◽  
Vol 50 ◽  
pp. 57-71 ◽  
Author(s):  
Xiao Nan Xu ◽  
Qiu Ping Zhang ◽  
Brain T.M. Ong ◽  
Huan Yuan ◽  
Yu Chen ◽  
...  
Keyword(s):  
Methyl Orange ◽  
Surface Defects ◽  
Sintering Temperature ◽  
Sol Gel ◽  
Microstructural Analysis ◽  
Volume Ratio ◽  
Gel Method ◽  
Sol Gel Method ◽  
Photocatalytic Effect ◽  
Degradation Of Methyl Orange

Utilizing zinc acetate as precursor, and monoethanolamine (MEA), diethanolamine (DEA) and triethanolamine (TEA) as stabilizers, respectively, ZnO nanoparticles with uniformly distributed grains were synthesized by sol-gel method at different sintering temperatures. Analysis of the degradation of methyl orange by photocatalysis shows that utilizing MEA as the stabilizer and 550°C as the sintering temperature results in smaller grain size, greater surface-to-volume ratio, and a density of surface defects suitable for a photocatalyst. The greatest photocatalytic degradation of methyl orange was achieved under UV irradiation. Based on our microstructural analysis and photocatalysis, the microstructure of ZnO particles and, in turn, their photocatalytic effect are affected significantly by the stabilizer type and the sintering temperature.

A new aerogel based CO2adsorbent developed using a simple sol–gel method along with supercritical drying

2014 ◽  
Vol 50 (81) ◽  
pp. 12158-12161 ◽  
Author(s):  
Yong Kong ◽  
Guodong Jiang ◽  
Maohong Fan ◽  
Xiaodong Shen ◽  
Sheng Cui ◽  
...  
Keyword(s):  
Sol Gel ◽  
Supercritical Drying ◽  
Gel Method ◽  
Sol Gel Method

Structural, Optical and Luminescent Properties of ZnO:Eu3+ Nanocrystals Prepared by Modified Sol-Gel Method

2009 ◽  
Vol 1174 ◽  
Author(s):  
Segundo R. Jauregui-Rosas ◽  
Oscar Perales-Perez ◽  
M. S. Tomar ◽  
Wei-Ji Jia ◽  
O. Vasquez ◽  
...  
Keyword(s):  
Surface Defects ◽  
Sol Gel ◽  
Luminescent Properties ◽  
Blue Shift ◽  
Exciton Peak ◽  
Wurtzite Phase ◽  
Gel Method ◽  
Sol Gel Method ◽  
Red Luminescence ◽  
Optical And Luminescent Properties

AbstractHighly monodisperse ZnO:Eu3+ nanocrystals have been synthesized by modified sol-gel method from ethanolic solutions. The effect of Eu3+ ions (x=0.05-0.30) concentration on the structural, optical and luminescent properties has been evaluated. No other than the ZnO-wurtzite phase was observed at all dopant levels, which was confirmed by FT-IR and Raman spectroscopy techniques. A blue shift of the exciton peak and the increase on the corresponding band gap were observed at increasing Europium contents, which would indicate an interaction between Eu3+ ions and the development of the ZnO host structure. The luminescence properties were also dependent on Europium contents; a systematic blue shift and enhancement of the intensity of visible luminescence peak, attributed to an increment of surface defects, was observed by a rising Europium concentration. The red luminescence band, representing the 5D0→7F0 transition, was clearly observed in nanocrystals after annealing at 300OC for one hour. The presence of this band could be considered as an evidence of the effective energy transfer from ZnO to Eu3+ ions.

SiO2 aerogels modified by perfluoro acid amides: a precisely controlled hydrophobicity

RSC Advances ◽  
2016 ◽  
Vol 6 (84) ◽  
pp. 80766-80772 ◽  
Author(s):  
S. A. Lermontov ◽  
N. A. Sipyagina ◽  
A. N. Malkova ◽  
A. V. Yarkov ◽  
S. G. Vasil'ev ◽  
...  
Keyword(s):  
Sol Gel ◽  
Supercritical Drying ◽  
Gel Method ◽  
Sol Gel Method

Five series of novel fluorinated aerogels based on acylated (3-aminopropyl)trimethoxysilane (APTMS) (MeO)3Si(CH2)3NHC(O)RF were prepared by a sol–gel method followed by supercritical drying in four different solvents.

Characterization of SiO2 Aerogel/SiO2 Fiber Composites Prepared by Sol-Gel Method

2016 ◽  
Vol 697 ◽  
pp. 409-413 ◽  
Author(s):  
Ping Zhai ◽  
Xiao Feng Duan ◽  
Qing Li Zhang ◽  
Hong Sheng Wang ◽  
Hong Hao Cheng ◽  
...  
Keyword(s):  
Moisture Absorption ◽  
Sol Gel ◽  
Acid Catalyst ◽  
Supercritical Drying ◽  
Fiber Composites ◽  
Vacuum Impregnation ◽  
Gel Method ◽  
Sol Gel Method ◽  
Properties Of Composites

Quartz fiber composites filled with nanosized SiO2 were prepared by sol-gel method with vacuum impregnation , supercritical drying and surface modification. The silica sol for vacuum impregnated were made from tetraethyl orthosilicate (TEOS), anhydrous ethanol, water and acid catalyst as the starting materials. The water adsorption rate, apparent porosity and electrical properties of composites were investigated by means of archimedes method and waveguide method while the surface area and pore size of the aerogel samples were tested by BET, the mechanism of hydrophobicity was also discussed. The results showed that the moisture absorption rate of products was decreased to 1.21% from 17.36% that without filled with nanosized SiO2, with a decreasing range of 93%. Additional coating could make the rate even as low as 0.052%.The dielectric constant had no significant change while the loss tangent decreased from 3.1╳10-3 to 1.4╳10-3,with a decreasing range of 51.2%.

Sign in / Sign up

Export Citation Format

Share Document