Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 49 for “"catalyst deactivation"”.
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3D modelling by computational fluid dynamics of local interactions of momentum, mass and heat transfers with catalyst deactivation in gas-solid catalytic reactors of low aspect ratios
… models. This project investigates non-uniform catalyst deactivation in packed bed reactors of low aspect ratios under steady-state and dynamic operations. Low aspect ratio packed beds were selected as they are known to generate non-uniform distribution of local flow. Detailed knowledge of flow …
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Developing an energy efficient steam reforming process to produce hydrogen from sulfur-containing fuels
… transportation fuel. A Rh-Pt/SiO2-ZrO2 catalyst has demonstrated good activity for the E85 steam reforming reaction. An industrial steam reforming process is often run less efficiently, with more water and at higher temperatures, in order to prevent catalyst deactivation. Therefore, it …
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Studies on the deactivation and reactivation of spent hydroprocessing catalyst
A study is reported on the deactivation of hydroprocessing catalysts and their reactivation by the removal of coke and metal foulants. The literature on hydrotreating catalyst deactivation by coke and metals deposition, the environmental problems associated with spent catalyst disposal, and its …
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Modeling and optimization of a two-stage regenerator fluid catalytic cracking unit
… and lighter products. In the FCCU process, the catalyst becomes deactivated in the reactor by heavy carbon deposits called coke. Catalyst activity is restored in the regenerator by burning off the coke with air. Steam formation during high temperature single-stage regeneration can cause …
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Change Of Metal Oxidation State At High Temperature, Impact Of Temperature And Reactive Gases
… catalysis, the use of metal doped heterogeneous catalysts are essential in achieving selectivity and conversion performance for chemical synthesis to emissions abatement. Typically, these metal alloys must withstand temperatures up to 1000 °C at pressures near 30 bar continuously for 8000 hours …
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Modeling and interpreting the observed effects of ash on diesel particulate filter performance and regeneration
… to investigate the process of ash transport and catalyst deactivation with increasing ash load level. DPF ash aging is found to have negative effect on passive regeneration due to the catalyst deactivation and diffusion resistance of ash cake layer. Besides, at given amount of ash load, the …
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The photo-oxidation of benzyl alcohol over TiO2 and Pt TiO2 and the effect of reaction conditions
… as the precursor salt. The synthesized platinum catalysts were characterized using PXRD, TEM, BET, ICP – OES. The spent catalysts were characterized using TEM, Raman, TGA and ATR-FTIR. The catalysts were tested for their activity and selectivity in the aerobic oxidation of benzyl alcohol in a …
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The effect of activation on the deactivation of a precipitated iron based catalyst
… on the performance and lifetime of an iron-based catalyst during the low temperature Fischer-Tropsch process. In particular, the effect of the activation procedure on the lifetime of the iron-based catalyst (deactivation behaviour) was investigated...
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Catalytic Hydrodeoxygenation of Guaiacol over Noble Metal Catalysts
… removal from pyrolysis bio-oils and noble metal catalysts have shown promising activities, especially as compared to the traditional hydrodesulphurization catalysts (e.g. CoMo/Al2O3 and NiMo/Al2O3). However, further understanding and development of the catalysts through improving robustness, …
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ΜΕΛΕΤΗ ΤΗΣ ΑΠΟΔΡΑΣΤΙΚΟΠΟΙΗΣΗΣ ΚΑΤΑΛΥΤΩΝ ΚΑΤΑ ΤΗΝ ΥΔΡΟΓΟΝΟΑΠΟΘΕΙΩΣΗ ΥΠΟΛΕΙΜΜΑΤΩΝΑΠΟΣΤΑΞΗΣ ΑΡΓΟΥ ΠΕΤΡΕΛΑΙΟΥ ΘΑΣΟΥ
… OIL (THASSOS) CARRIED OUT WHILE AT THE SAME TIME CATALYST DEACTIVATION PHENOMENA WERE QUANTIFIED. A LABORATORY CHEMICAL REACTOR EQUIPPED WITH FOUR CATALYST BASKETS AND OF TOTAL INTERNAL VOLUME OF 890 CM3 WAS USED IN THE INVESTIGATION. AT BASKET RETATION RATES ABOVE 2500 RPM THE HDS RATEPROVED TO …
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Deactivation and regeneration of immobilized titanium dioxide photocatalysts during treatment of pharmaceutical micropollutants in groundwater
… in short-term batch experiments using fresh catalysts in laboratory solutions devoid of non-target constituents that are often abundant in natural water matrices (e.g., Ca2+, HCO3-, natural organic matter). In this contribution, we describe the results of an investigation of the long-term …
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Zeolite deactivation during hydrocarbon reactions: characterisation of coke precursors and acidity, product distribution
… of heavy by-products, called coke, which causes catalyst deactivation. This deactivation is due to the poisoning of the acid sites and/or pore blockage. The formation of coke on hydrocarbon processing catalysts is of considerable technological and economic importance and a great deal of work has …
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ADVANCED BIFUNCTIONAL CORE-SHELL CATALYSTS FOR METHANE REFORMING USING CARBON DIOXIDE
… operational challenges stemming from rapid catalyst deactivation by sintering, formation of coke or poisoning by contaminants severely limit the industrial implementation of this technology. The research presented in this PhD thesis aims at developing Ni-containing catalysts with high …
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Catalytic Cracking Of Hydrocarbons With Novel Metal Traps
Nickel and vanadium poison FCC catalysts with destruction of zeolites. This is reflected by a lower gas oil conversion and lower gasoline selectivity. Ni and V also affect hydrogen transfer resulting in more coke formation and reducing light gases.;New catalysts, so-called FCCT (catalysts for FCC …
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The Chemical Kinetics of the Hydrogenation of Coal Extract Solutions
… stirred tank reactor with slurried catalyst. The reactor system and experimental programme were designed so that many of the process variables affecting the rate of hydrogenation of coal extract solutions and suspected reaction intermediates could be investigated. These variables …
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Gas-solid chromatographic studies of two well-known catalysts
… to investigate various possible systems. Two catalysts were chosen for study. The dehydration of alcohols over alumina catalysts has been extensively studied and found to be ideally suited to studies by gas chromatography. The effect of modification of the catalyst by inorganic ions and by …
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Homogeneous Cobalt Catalyzed Oxidations
… a Co-O(,2) species and a phenoxy radical. Catalyst deactivation studies revealed benzoquinone and water do not inhibit the reaction, but rather acids produced as oxidized side products eventually deactivate the catalyst. Thus, the addition of non-coordinating bases to the reaction medium …
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A comparative study of PtCo/C Alloys and Pt/C as cathode catalysts for fuel cell applications
… fuel cells for automotive applications requires catalysts with both improved activity, particularly for the cathodic oxygen reduction reaction (ORR), and stability over commercial platinum only catalysts. This requires a detailed understanding of both desirable catalyst structure and mechanistic …
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Development of Deactivation-Resistant Catalysts for Pd-Catalyzed C–N Cross-Coupling Reactions
… in a variety of fields, and Pd-based catalysts are among the most effective for these reactions. However, certain classes of compounds, including very bulky substrates as well as those containing coordinating functional groups, can be very difficult to couple. The choice of the …
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Experimental and modeling studies using packed bed reactors: Liquid phase ethylene production by hydrogenation of acetylene
… has green oil formation, which leads to catalyst deactivation and sometimes reactor runaway risks due to high exothermicity. To overcome these issues as well as to increase the selectivity and conversion, liquid-phase hydrogenation of acetylene was investigated in packed bed reactors …
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