Structure et dynamique de nanomatériaux industriels

Nous avons utilisé un choix de méthodes de chimie quantique ainsi que des simulations par dynamique moléculaire (MD) pour étudier les propriétés structurelles et dynamiques d'hydrocarbures aromatiques dans des matériaux nanoporeux d'intérêt industriels. Les énergies d'adsorption sont trouvées en bon accord avec les valeurs expérimentales disponibles. Cette modélisation à l'échelle microscopique permet de développer une vision cohérente des conditions dans le nanopore, en particulier des interactions entre molécules adsorbées et réseau. La dynamique des molécules invitées, en particulier la diffusion et les temps de résidence caractéristiques des différents sites ont été étudiés en fonction de la température et de la concentration

Zeolites and ordered porous solids: fundamentals and applications

Pérez Pariente, J.; Martínez Sánchez, MC. (2011). Zeolites and ordered porous solids: fundamentals and applications. Editorial Universitat Politècnica de València. http://hdl.handle.net/10251/11205Archivo delegad

Catalytic Conversion of Benzothiophene Over a H-ZSM5 Catalyst, Reactivity and a Kinetic Model

Nowadays and due to environmental legislations, a world-wide attention has been given towards clean transportation fuels with emphasis on sulfur contents reduction. These efforts on the other hand are challenged by the poor qualities of crude oils. The existing desulfurization technologies such as hydrodesulfurization are not capable to cope with new firm standards. Hence, it is extremely desirable to develop a catalytic desulfurization process to meet both sulfur limits and refining economics. As one aspect of this objective, it is of great importance to study and comprehend the behaviour and chemistry of individual sulfur species present in transportation fuels cuts. Zeolites namely, H-ZSM5 has shown a potential catalyst for a desulfurization process for gasoline fuel range. Acidity and shape selectivity of these zeolites make it viable for such a process eliminating the use of hydrogen. With aiming to light diesel fraction desulfurization, this dissertation provides insights and understanding of benzothiophene sulfur species conversion over a H-ZSM5 zeolite catalyst. The H-ZSM5 particles were dispersed in an inert silica-alumina matrix to diminish possible cracking of diesel model compound (n-dodecane). This catalyst was characterized using standard techniques including: a) NH3-TPD, b) N2 adsorption, c) Particle size distribution, d) X-ray diffraction, e) SEM-EDX, and f) Pyridine FTIR. Catalytic and thermal runs were performed in the CREC Riser Simulator that mimics the industrial FCC unit. This reaction system was operated at close to atmospheric pressure, 350°C – 450°C temperatures, and 3, 5, 7 seconds reaction times. Thermal cracking was found to be negligible under the studied reaction conditions. Experimental results from catalytic runs showed a higher benzothiophene conversion over n-dodecane conversion. This was true despite the difference in benzothiophene and n-dodecane molecular sizes. The experimental results of this PhD dissertation are also supported with a molecular dynamics (MD) simulation study that studies self diffusivity of benzothiophene and n-dodecane in ZSM-5 zeolite. In addition and using the obtained experimental data, a heterogeneous kinetic model is proposed for benzothiophene conversion over H-ZSM5 catalyst. Numerical non-linear regression leads to model parameters estimations with low confidence intervals suggesting the adequacy of this kinetic model

Deactivation of PtH-ZSM-5 Bifunctional Catalysts by Coke Formation during Benzene Alkylation with Ethane

The alkylation of benzene with ethane was studied at 370 oC over two Pt-containing ZSM-5 catalysts with SiO2/Al2O3 ratios of 30 and 80. While the benzene and ethane conversion decreased with time-on-stream for the PtH-ZSM-5(30) catalyst, the PtH-ZSM-5(80) catalyst demonstrated a stable performance. The deactivation of the PtH-ZSM-5(30) catalyst was found to be more significant, when compared to the PtH-ZSM-5(80) catalyst as a result of differences in the formation of coke. Results from gas sorption and x-ray diffraction experiments showed that coke is preferentially formed within the channel segments of the PtH-ZSM-5(30) catalyst as opposed to coke deposition on the outside surface of the PtH-ZSM-5(80) crystallites, subsequently blocking entrance to the zeolite channels. The location of the coke deposition was found to affect the product selectivity of the two PtH-ZSM-5 catalysts. The accessibility functions, derived from nitrogen and argon sorption data, suggested that, with prolonged time-on-stream, the coke molecules build up from the middle of the zeolite crystallites outwards towards the surface, as the reaction was carried out over the PtH-ZSM-5(30) catalyst. Partial blockage of the internal pore structure of the PtH-ZSM-5(30) catalyst decreased the diffusion length within the crystallites. In contrast to the typical effect of coking, where the selectivity of para- isomers would be enhanced with coke deposition, the effect of the reduction in the diffusion length of the PtH-ZSM-5(30) crystallites is consistent with the decreasing para-selectivity of the diethylbenzene (DEB) isomers with time-on-stream. n investigation of the causes of coke locations was conducted, and the results suggested that, the spatial distribution of Pt metal was responsible for the different locations of coke observed. Surface reactions initiated coking in the intercrystalline region of the PtH-ZSM-5(80) catalyst, as the Pt particles on the surface of the PtH-ZSM-5(80) crystallites increased the difficulty of access for reactants to the interior of the crystallites. Within the PtH-ZSM-5(30) catalyst, ethane dehydrogenation and benzene alkylation took place in the micropore network as a result of preferential intracrystalline deposition of Pt metal. Further conversions on the active sites within the PtH-ZSM-5(30) crystallites thus lead intracrystalline coking.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Investigation on the Low-Temperature Transformations of Poly(furfuryl alcohol) Deposited on MCM-41

MCM-41-type mesoporous silica was used as a support for poly(furfuryl alcohol) deposition. This material was produced by precipitation–polycondensation of furfuryl alcohol (FA) in aqueous slurry of the SiO2 support followed by controlled partial carbonization. By tuning the FA/MCM-41 mass ratio in the reaction mixture, various amounts of polymer particles were introduced on the inner and outer surface of the MCM support. The thermal decomposition of the PFA/MCM-41 composites was studied by thermogravimetry (TG) and spectroscopic techniques (DRIFT, XPS), whereas the evolution of textural parameters with increasing polymer content was investigated using low-temperature adsorption of nitrogen. The mechanism of thermal transformations of PFA deposited on the MCM-41 surface was discussed in detail. It was found that heating at a temperature of about 523 K resulted in opening of the furan rings and the formation of γ-diketone moieties, which were found to be the highest effective surface species for the adsorption of polar volatile organic compounds. A further increase in calcination temperature caused a drop in the amounts of surface carbonyls and the appearance of condensed aromatic domains.This work was supported by the Polish Ministry of Science and Higher Education under Grant N N507 553238. Rafał Janus thanks the Foundation for Polish Science MPD Programme cofinanced by the EU European Regional Development Fund for the financial support. The research was carried out with equipment purchased thanks to financial help from the European Regional Development Fund within the framework of the Polish Innovation Economy Operational Program (Contract POIG.02.01.00-12-023/08)