Influence of Silicon Content and Nature of the Template Molecule on Physico-Chemical and Catalytic Properties of SAPO-5

1992 ◽  
Vol 57 (4) ◽  
pp. 826-835 ◽  
Author(s):  
Jochen Jänchen ◽  
Vladimir Penchev ◽  
Elke Löffler ◽  
Barbara Parlitz ◽  
Helmut Stach
Keyword(s):  
Catalytic Activity ◽  
Molecular Sieves ◽  
Silicon Content ◽  
Silica Content ◽  
Template Molecule ◽  
Toluene Disproportionation ◽  
Physico Chemical ◽  
Adsorbed Ammonia ◽  
Temperature Programmed ◽  
Si Content

Two series of SAPO-5 molecular sieves were synthesized: (i) Using tripropylamine as a template and varying the Si content in the gel, and (ii) varying the template molecule at constant silicon content in the gel. The products were characterized physico-chemically and tested in toluene disproportionation. It was found that the rising silica content in the synthesis gel has only little influence on the SiO2 incorporation into the SAPO. Investigation of the acid character revealed that the concentrations of the adsorbed ammonia molecules are nearly constant and independent of the total silicon content of the crystals. The catalytic activity showed no correlation either with the silicon content of the catalysts or with the acidity measured by temperature-programmed desorption of ammonia. It is concluded that the incorporated silicon exists not only in a monomeric form and that the TPD of ammonia reflects not only the strong Bronsted acidity. The SAPO-5 sample synthesized with triethylamine possessed the strongest acidity corresponding to the highest catalytic activity. It is supposed that in the presence of TEA molecules silicon replaces mainly P atoms in the AlPO4-5 framework.

scholarly journals Selective Oxidation of Cyclohexane to KA Oil Over Ce-Alpo-18 Molecular Sieves

2018 ◽  
Vol 7 (4.5) ◽  
pp. 352
Author(s):  
M. Esther Leena Preethi ◽  
A. Umasankari ◽  
C. H.Rekha ◽  
M. Palanichamy ◽  
T. Sivakumar ◽  
...  
Keyword(s):  
Molecular Sieves ◽  
Diffuse Reflectance Spectroscopy ◽  
Complete Removal ◽  
Template Molecule ◽  
The Novel ◽  
X Ray Diffraction ◽  
Free System ◽  
Physico Chemical ◽  
Solvent Free System ◽  
Ft Ir

The novel catalysts Ce-AlPO-18 with Al/Ce = 25, 50, 75 &100 were synthesized using hydrothermal synthesis procedure. The newly synthesized catalysts were characterized using physico-chemical techniques such as, X-ray diffraction (XRD) which confirmed AEI structure, diffuse reflectance spectroscopy (DRS-UV) confirmed the presence of both Ce3+ and Ce4+ in the framework and Fourier transform infrared spectroscopy (FT-IR) confirmed the complete removal of template molecule. The synthesized catalysts were tested for the oxidation of cyclohexane using air as the oxidant in a solvent free system and the results were discussed.   

scholarly journals Alkalinity–silicon ratio as an assessment factor for the efficiency of silicate slags in wetland rice

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Thoppil Sreenivasan Sandhya ◽  
Nagabovanalli Basavarajappa Prakash
Keyword(s):  
Silicon Content ◽  
Chemical Properties ◽  
Magnesium Content ◽  
Wetland Rice ◽  
Agronomic Efficiency ◽  
Economic Production ◽  
Incubation Experiments ◽  
Calcium And Magnesium ◽  
Si Content ◽  
Assessment Factor

AbstractSilicate slags are one of the most widely used silicon (Si) source in agriculture. Even though the agronomic significance of slags has been demonstrated in several crops, only a few attempts were made to evaluate these Si sources based on their chemical composition. The main objective of this study was to characterize different silicate slags based on their chemical properties and to explore the effect of these chemical properties on the yield, and Si uptake in wetland rice, and dissolution of Si into the soil. Slags were characterised for pH, calcium and magnesium content (alkalinity, A), silicon content, 5 day Na2CO3 + NH4NO3 extractable Si content, and alkalinity to Si ratio (A/Si). Greenhouse and incubation experiments were also conducted using different silicate slags and wollastonite applied at the rate of 300 kg Si ha−1. Slags with A/Si < 3 were found to be ideal Si sources for the economic production of wetland rice and found consistent in increasing soil Si content and rice Si uptake. We conclude that the A/Si ratio of slags can be used as an important parameter to assess the agronomic efficiency of silicate slags in wetland rice.

scholarly journals Role of CO2 During Oxidative Dehydrogenation of Propane Over Bulk and Activated-Carbon Supported Cerium and Vanadium Based Catalysts

2021 ◽  
Author(s):  
Petar Djinović ◽  
Janez Zavašnik ◽  
Janvit Teržan ◽  
Ivan Jerman
Keyword(s):  
Catalytic Activity ◽  
Activated Carbon ◽  
Oxidative Dehydrogenation ◽  
Active Phase ◽  
Lattice Oxygen ◽  
Chemisorbed Oxygen ◽  
Catalytically Active ◽  
Temperature Programmed ◽  
Propane Cracking

AbstractCeO2, V2O5 and CeVO4 were synthesised as bulk oxides, or deposited over activated carbon, characterized by XRD, HRTEM, CO2-TPO, C3H8-TPR, DRIFTS and Raman techniques and tested in propane oxidative dehydrogenation using CO2. Complete oxidation of propane to CO and CO2 is favoured by lattice oxygen of CeO2. The temperature programmed experiments show the ~ 4 nm AC supported CeO2 crystallites become more susceptible to reduction by propane, but less prone to re-oxidation with CO2 compared to bulk CeO2. Catalytic activity of CeVO4/AC catalysts requires a 1–2 nm amorphous CeVO4 layer. During reaction, the amorphous CeVO4 layer crystallises and several atomic layers of carbon cover the CeVO4 surface, resulting in deactivation. During reaction, V2O5 is irreversibly reduced to V2O3. The lattice oxygen in bulk V2O5 favours catalytic activity and propene selectivity. Bulk V2O3 promotes only propane cracking with no propene selectivity. In VOx/AC materials, vanadium carbide is the catalytically active phase. Propane dehydrogenation over VC proceeds via chemisorbed oxygen species originating from the dissociated CO2. Graphic Abstract

scholarly journals CO oxidation over Pt-modified CuO catalysts in the presence of water vapour and SO2

2015 ◽  
Vol 18 (2) ◽  
pp. 187-196
Author(s):  
Tri Nguyen ◽  
Anh Cam Ha ◽  
Loc Cam Luu ◽  
Cuong Tien Hoang ◽  
Thi Thi Yen Trinh ◽  
...  
Keyword(s):  
Co Oxidation ◽  
Water Vapour ◽  
Co Adsorption ◽  
X Ray Diffraction ◽  
Active Centers ◽  
Highly Active ◽  
Transmission Electron ◽  
Physico Chemical ◽  
Adsorption Of Co ◽  
Temperature Programmed

The optimal Pt-modified CuO supported on γ-Al2O3 and γ-Al2O3 + CeO2 catalysts have been prepared. Physico-chemical characteristics of catalysts were investigated and determined by the methods of N2 adsorption (BET), X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), temperature-programmed reduction (TPR), and hydrogen pulse chemisorption (HPC). The characteristics of carbon monoxide (CO) adsorption on catalysts were defined by the method of infrared spectroscopy (IR) in the range of 4000 – 400 cm-1. The effect of the mixture of water vapour and SO2 on the activity of these catalysts for the CO oxidation was assessed. Reactions were conducted at 200oC and 350oC in the absence and presence of the mixture of water vapour (1.1 mol %) and SO2 (0.0625 mol %). Concentrations of O2 and CO in the gas mixture were 9.2 mol % and 0.5 mol %, respectively. The results showed that in the catalysts there exist highly active centers Cu1+ and Pt2+. On the catalysts the adsorption of CO on Cu2+, Pt2+, CeO2, and γ - Al2O3 centres was observed. Addition of CeO2 led to increase the reductivity, CO adsorption but decrease in specific surface area of catalyst. The result PtCu/CeAl catalyst shown higher active, but lower stability compared to PtCu/Al catalyst. The mixture of water vapour and SO2 showed the reversible poisoning toward the Pt-CuO catalysts at a temperature of 350oC, but irreversible at 200oC

The Silicon Content of Body Fluids

1982 ◽  
Vol 27 (1) ◽  
pp. 17-19 ◽  
Author(s):  
J. W. Dobbie ◽  
Mary J. B. Smith
Keyword(s):  
Comparative Study ◽  
Amniotic Fluid ◽  
Atomic Absorption ◽  
Absorption Spectroscopy ◽  
Pancreatic Juice ◽  
Atomic Absorption Spectroscopy ◽  
Silicon Content ◽  
Healthy Subjects ◽  
Clinical Procedures ◽  
Si Content

Samples of bile, pancreatic juice, cerebrospinal, pleural, peritoneal, synovial and amniotic fluid obtained from patients during routine clinical procedures were analysed for their silicon (Si) content by atomic absorption spectroscopy (AAS). Similar Si concentrations were found in each fluid, while these in turn were shown to be similar to the concentration of Si in the serum of 50 healthy subjects (mean serum Si 21.5 μmol/l, SD±4.5). The concentration of Si in 24-hour collections of urine from 50 healthy subjects was also determined (mean urinary Si 194 μmol/l, SD±94). A comparative study was made of serum Si levels in nine different species of domesticated animal.

Effect of Si, Sr Additions on Microstructure and Mechanical Properties of AZ91 Alloy

2007 ◽  
Vol 546-549 ◽  
pp. 179-182
Author(s):  
S.B. Li ◽  
Zhi Wen Zou ◽  
Shou Mei Xiong
Keyword(s):  
Mechanical Properties ◽  
Silicon Content ◽  
Room Temperature ◽  
Chinese Script ◽  
Az91 Alloy ◽  
Permanent Mold ◽  
Remarkable Effect ◽  
Mg2si Phase ◽  
Β Phase ◽  
Si Content

In present work, Si and Sr elements were added into AZ91 alloy and cast directly into test samples using permanent mold. Mechanical properties of the samples at room temperature were evaluated by tensile test and the microstructure was analyzed. The results show that β-phase (Mg17Al12) of AZ91 alloy decreases with the addition of Si element and Mg2Si phase forms at the same time. Irregular Mg2Si phase precipitates preferentially at the grain boundaries at a low silicon content level. With the increase of the Si content, Mg2Si phase shows a complicated “Chinese- script” shape distributed at the grain boundary which leads to a lower ultimate tensile strength. Subsequently, the addition of Sr element has a remarkable effect on the form and distribution of Mg2Si phase of AZ91-Si alloys.

Synthesis, characterization and catalytic activity of actinide Th-MCM-41 and U-MCM-41 hexagonal packed mesoporous molecular sieves

2001 ◽  
Vol 171 (1-2) ◽  
pp. 229-241 ◽  
Author(s):  
Rodica Tismaneanu ◽  
Biswajit Ray ◽  
Rafael Khalfin ◽  
Rafi Semiat ◽  
Moris S. Eisen
Keyword(s):  
Catalytic Activity ◽  
Molecular Sieves ◽  
Mesoporous Molecular Sieves ◽  
Mcm 41
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