Search results for "ZEOLITE"
showing 10 items of 203 documents
Converting olefins to propene: Ethene to propene and olefin cracking
2018
ABSTRACTDemand for propene as a petrochemical building block keeps growing, while its availability has been decreased by the adoption of shale gas resources, among others. Efforts to optimize its production by conventional means (including modified fluid catalytic cracking) and new on-purpose production technologies (including ethene to propene (ETP) and olefin cracking) are being pursued. This work reviews the progress made on olefin conversion processes, including the ETP reaction, which is still under development, and the cracking of butenes and higher olefins (C5–C8). The factors analyzed include the catalytic performance of different zeolite materials and their modifications to increas…
Ship-in-a-bottle synthesis of triphenylamine inside faujasite supercages and generation of the triphenylamminium radical ion
2005
Abstract The ship-in-a-bottle synthesis of triphenylamine encapsulated within basic X zeolite has been accomplished by reacting sodium diphenylamide with bromobenzene in the presence of a bifunctional palladium (Hartwig–Buchwald conditions). The presence of incarcerated triphenylamine was demonstrated by dissolving the zeolite with concentrated HF and analyzing the organic material in the dichloromethane extract. Laser flash photolysis (266 nm) gives rise to the generation of triphenylamminium radical cation detected as a transient species decaying in hundreds of microseconds. Upon repetitive cyclic voltammograms, zeolite encapsulated triphenylamine shows a reversible oxidation–reduction pr…
γ-Fe2O3 nanoparticle in NaY-zeolite matrix: Preparation, characterization, and heterogeneous catalytic epoxidation of olefins
2010
Abstract Nano-sized crystals of maghemite iron oxide (γ-Fe 2 O 3 ) were synthesized onto the surface of NaY-zeolite crystals by immobilizing a polynuclear iron complex [Fe 4 O 2 (O 2 CCH 3 ) 7 (bpy) 2 ](ClO 4 ) (bpy = 2,2′-bipyridine) and subsequent calcination of the material in oxygen. Superparamagnetic γ-Fe 2 O 3 particles with sizes ∼5 nm were formed on the surface of the zeolite matrix. The nano-composite, γ-Fe 2 O 3 @NaY has been subsequently subjected for thorough characterization with several spectroscopic techniques as well as magnetic and transmission electron microscopic measurements. This confirms the formation of maghemite nanoparticles on a NaY-zeolite surface. γ-Fe 2 O 3 @NaY…
Synthesis of a novel zeolite through a pressure-induced reconstructive phase transition process
2013
et al.
Water-Hydrophobic Zeolite Systems
2012
Water intrusion-extrusion in hydrophobic microporous AFI, IFR, MTW and TON pure silica zeolites (zeosils) has been investigated through molecular dynamics (MD) simulations. It was found that intruded water volumes correlate with the free volume of the zeosil unit cells. Calculated adsorption isotherms allowed us to estimate the amounts of water intruded, and deviations from experiments (lower experimental with respect to calculated intrusion pressures) have been;explained in terms of connectivity defects in the synthesized materials. Water phase transitions in defectless zeosils occur in a narrow range at high pressure. On the basis of a simple model, we derived a thermodynamic equation tha…
Computational screening of structure directing agents for the synthesis of zeolites. A simplified model
2018
Abstract Zeolite micropores become more energetically stable by the occlusion of organic structure directing agents (templates). This energetic stabilisation, if approximated by van der Waals zeo-template interactions, can be calculated in a fast way by using modern computing techniques incorporating big data handling algorithms for massive screening. A software suite is presented which calculates an arbitrarily large 2-D matrix (template×zeolite) giving the zeo-template van der Waals interaction energy corresponding to the minimum energy conformation assuming one template molecule in a pure silica zeolite unit cell. With the goal of simplicity, the software only needs two coordinate input …
Ultra-small gold nanoclusters assembled on plasma polymer-modified zeolites: a multifunctional nanohybrid with anti-haemorrhagic and anti-inflammator…
2021
Refereed/Peer-reviewed Hemostatic agents are pivotal for managing clinical and traumatic bleeding during emergency and domestic circumstances. Herein, a novel functional hybrid nanocomposite material consisting of plasma polymer-modified zeolite 13X and ultra-small gold nanoclusters (AuNCs) was fabricated as an efficient hemostatic agent. The surface of zeolite 13X was functionalised with amine groups which served as binding sites for carboxylate terminated AuNCs. Protein corona studies revealed the enhanced adsorption of two proteins, namely, coagulation factors and plasminogen as a result of AuNCs immobilization on the zeolite surface. The immune response studies showed that the hybrid na…
New force field for GCMC simulations of D 2 /H 2 quantum sieving in pure silica zeolites
2020
International audience; We report a study on adsorption and coadsorption of H2 and D2 in FAU, MFI and CHA pure silica zeolites having different pore sizes and shapes. Adsorption capacities, selectivities, enthalpies and entropies are determined by combining experiments and GCMC simulations. We show that the force fields available in the literature cannot predict the adsorption equilibria below 77 K with sufficient accuracy. Here we propose a new force field adjusted by using our experimental data obtained for the pure silica MFI zeolite at 65 K and 77 K. With this new force field, it is possible to predict the adsorption and coadsorption equilibria on the three zeolite structures in a tempe…
Structural incorporation of nitrogen into zeolites, and alpos: ab initio molecular orbital calculations on stability and basicity
1998
Ab initio molecular orbital calculations (HF/6-31G*) are used to obtain thermodynamical information on the possibility to form NH-bridging or NH2-terminal groups in amorphous and crystalline materials containing Si–O–Si and Al–O–P structures, such as for instance, zeolites and aluminophosphates. We have employed dimeric model clusters Si–O–Si and Al–O–P which contain NH2-terminal groups or an oxygen atom substituted by a NH bridging unit. The Bronsted basicity and the softness–hardness of these structures have been determined using the proton affinity and the HOMO energy, respectively. The obtained results indicate that for both Si–O–Si and Al–O–P linkages and from a thermodynamic standpoin…
IM-5 zeolite for steam catalytic cracking of naphtha to produce propene and ethene. An alternative to ZSM-5 zeolite
2013
Steam catalytic cracking of naphtha in smaller FCC units can be considered an option to produce more ethene and propene. These units will operate at high reaction temperatures and in the presence of steam. The profitability of these units could be improved with the use of new catalysts with higher activity and hydrothermal stability, without compromising the selectivity to light olefins. We have explored the possibilities of IM-5 zeolite for high temperature steam catalytic cracking (SCC) of a naphtha, as an alternative to commonly used ZSM-5 zeolite. So, we compare the catalytic activity, the effect of operating variables of the process and the yields of interest products between the two z…