scholarly journals Energetic Characterization of Faujasite Zeolites Using a Sensor Gas Calorimeter

Catalysts ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 98
Author(s):  
Volker Mauer ◽  
Christian Bläker ◽  
Christoph Pasel ◽  
Dieter Bathen
Keyword(s):  
Heterogeneous Catalysis ◽  
Adsorption Mechanism ◽  
Heat Of Adsorption ◽  
Adsorption Sites ◽  
Energetic Characterization ◽  
Low Degree ◽  
Gas Calorimeter ◽  
Heat Released ◽  
Faujasite Zeolite

In addition to the adsorption mechanism, the heat released during exothermic adsorption influences the chemical reactions that follow during heterogeneous catalysis. Both steps depend on the structure and surface chemistry of the catalyst. An example of a typical catalyst is the faujasite zeolite. For faujasite zeolites, the influence of the Si/Al ratio and the number of Na+ and Ca2+ cations on the heat of adsorption was therefore investigated in a systematic study. A comparison between a NaX (Sodium type X faujasite) and a NaY (Sodium type Y faujasite) zeolite reveals that a higher Si/Al ratio and therefore a smaller number of the cations in faujasite zeolites leads to lower loadings and heats. The exchange of Na+ cations for Ca2+ cations also has an influence on the adsorption process. Loadings and heats first decrease slightly at a low degree of exchange and increase significantly with higher calcium contents. If stronger interactions are required for heterogeneous catalysis, then the CaNaX zeolites must have a degree of exchange above 53%. The energetic contributions show that the highest-quality adsorption sites III and III’ make a contribution to the load-dependent heat of adsorption, which is about 1.4 times (site III) and about 1.8 times (site III’) larger than that of adsorption site II.

scholarly journals A Brief Overview of Recent Progress in Porous Silica as Catalyst Supports

2021 ◽  
Vol 5 (3) ◽  
pp. 75
Author(s):  
Preeti S. Shinde ◽  
Pradnya S. Suryawanshi ◽  
Kanchan K. Patil ◽  
Vedika M. Belekar ◽  
Sandeep A. Sankpal ◽  
...  
Keyword(s):  
Heterogeneous Catalysis ◽  
High Surface ◽  
High Surface Area ◽  
Porous Silica ◽  
Textural Properties ◽  
Silica Particles ◽  
Catalyst Supports ◽  
Silica Supports ◽  
Low Degree ◽  
Transfer Properties

Porous silica particles have shown applications in various technological fields including their use as catalyst supports in heterogeneous catalysis. The mesoporous silica particles have ordered porosity, high surface area, and good chemical stability. These interesting structural or textural properties make porous silica an attractive material for use as catalyst supports in various heterogeneous catalysis reactions. The colloidal nature of the porous silica particles is highly useful in catalytic applications as it guarantees better mass transfer properties and uniform distribution of the various metal or metal oxide nanocatalysts in solution. The catalysts show high activity, low degree of metal leaching, and ease in recycling when supported or immobilized on porous silica-based materials. In this overview, we have pointed out the importance of porous silica as catalyst supports. A variety of chemical reactions catalyzed by different catalysts loaded or embedded in porous silica supports are studied. The latest reports from the literature about the use of porous silica-based materials as catalyst supports are listed and analyzed. The new and continued trends are discussed with examples.

Bentonite-Based Organoclays as Innovative Flame Retardants Agents for SBS Copolymer

2008 ◽  
Vol 8 (12) ◽  
pp. 6316-6324 ◽  
Author(s):  
M. Comes Franchini ◽  
P. Fabbri ◽  
A. Frache ◽  
G. Ori ◽  
M. Messori ◽  
...  
Keyword(s):  
Flame Retardants ◽  
Morphological Characterization ◽  
Tem Analysis ◽  
Important Functional Property ◽  
Octadecyltrimethylammonium Bromide ◽  
Nitrogen Containing Compounds ◽  
Styrene Butadiene ◽  
Heat Released

Two organophilic bentonites, based on nitrogen-containing compounds, have been synthesised via ion exchange starting from pristine bentonite with octadecyltrimethylammonium bromide (OTAB) and with synthetic melamine-derived N2,N4-dihexadecyl-1,3,5-triazine-2,4,6-triamine (DEDMEL). The chemical and morphological characterization of the organoclays was based on XRD, TEM, Laser Granulometry, X-Ray Fluorescence and CEC capacity. Copoly(styrene-butadiene-styrene)-nanocomposites (SBS-nanocomposites) were obtained by intercalation of the SBS-copolymer into these new organoclays by melt intercalation method. XRD and TEM analysis of the organoclays and of the micro/nano-composites obtained are presented. The effect of the organoclays on the SBS-nanocomposite's flammability properties was investigated using cone calorimeter. An encouraging decrease of 20% in the peak heat released rate (PHRR) has been obtained confirming the important role of melamine's based skeleton and its derived organoclays to act as effective fire retardants and for the improvement of this important functional property in SBS copolymers.

scholarly journals HDPE/SILICA COMPOSITES- PART I: PREPARATION AND CHARACTERIZATION OF METHYLSILANE AND OCTYLSILANE-MODIFIED SILICAS

2019 ◽  
Vol 16 (32) ◽  
pp. 263-278
Author(s):  
Vanessa Machado Babinski RAMOS ◽  
Maurício Gammertt RÖHNELT ◽  
Rodrigo BRAMBILLA
Keyword(s):  
Silica Gel ◽  
Morphological Characteristics ◽  
Specific Area ◽  
Sem Images ◽  
Adsorption Sites ◽  
Pyrogenic Silica ◽  
The Mean ◽  
Complementary Techniques ◽  
Adsorption Desorption

This paper reports the main results concerning the synthesis and characterization of methylsilane and octylsilane-modified silicas. The modification of the silicas with these groups aims to make the silica surface hydrophobic and thus compatible with high-density polyethylene (HDPE) in HDPE/silica composites. In the present work, two types of silica were organofunctionalized: a pyrogenic silica and a silica gel. The silicas were characterized by a series of complementary techniques with the objective of investigating the nature of the surface species and their textural and morphological characteristics. The SEM images showed that the modification of the silicas with organosilanes has been not resulted in changes on the morphology and on the size of silica particles. In relation to the texture properties, determined by N2 adsorption-desorption porosimetry, the silica modification resulted in a decrease of the specific area (SBET) and the mean pore volume, a behavior attributed to the partial coverage of the adsorption sites by the organosilane molecules. The TGA analysis showed that both the methylsilane groups and the octylsilane groups on the surface of silica and silica gel are thermally stable up to 200 ° C, which enables the organofunctionalized silicas in terms of thermal stability, for the process of preparing the composites by extrusion. The results of applying these organofunctionalized silicas in the development of HDPE/silica composites will be presented in a subsequent article, part II of this research.

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