Browsing by Author "Rezgui, Y"

Now showing 1 - 7 of 7
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    A Detailed Chemical Kinetic Mechanism for Methanol Combustion in Laminar Flames1
    (Pleiades Publishing, 2011) Hamdane, S; Rezgui, Y; Guemini, M
    On the basis of existing detailed kinetic schemes a general and consistent mechanism of the oxi dation of methanol was compiled for computational studies covering a wide range of lean to rich flames. The proposed model, featuring 21 species and 115 reactions, has been validated using three data sets and the com puted reactants, products and intermediates mole fractions. This scheme was compared to those by Held⎯Dryer, Egolfopolous and Pauwels under the same conditions. The developed mechanism predicts well the concentrations of the major reactants, intermediates, and products at all the studied equivalence ratios and it gives the best calculated values, as compared to the other used models, as well. The production rates analysis of selected species allowed the identification of the major formation and depletion pathways. A reac tion path analysis snowed that the main channels in methanol consumption involved H, OH and O attack and the resulting radicals CH2OH and CH3O produced formaldehyde.
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    Benzene Combustion: A Detailed Chemical Kinetic Modeling in Laminar Flames Conditions1
    (Pleiades Publishing, 2014) Rezgui, Y; Guemini, M
    Models resulting from the merging of validated kinetic schemes were used to compile a new detailed mechanism for benzene combustion in laminar flames. The proposed model, featuring 215 species and 1313 reactions, has been validated using fuelrich, lowpressure, premixed benzene–oxygen–argon flames available in the literature. Good agreement between simulated and experimental data is achieved for the major reactants, intermediates, and products. However, computed maxima for some polyaromatic hydro carbons were lower than experimental ones.
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    Effect of acidity and metal content on the activity and product selectivity for n-decane hydroisomerization and hydrocracking over nickel–tungsten supported on silica–alumina catalysts
    (ELSEVIER, 2005) Rezgui, Y; Guemini, M
    Ni–W/silica–alumina based catalysts with different nickel and tungsten concentration (nickel ranging from 12 to 17% and tungsten ranging from 8 to 30%) were prepared by sol–gel method. The BET, temperature-programmed desorption of ammonia (TPDA) and inductively coupled plasma-atomic emission spectroscopy (ICP-AES) techniques were used to characterize the prepared solids. Afterwards, the catalysts were screened for activity and selectivity in the hydroconversion of n-decane. Under the experimental conditions, yields of isomers as well as cracking products were a function of both metal content and amount of acid sites. Up to 15% Ni content, nickel increased isomerization selectivity, afterwards, the catalytic selectivity decreased. Moreover, the higher the amount of medium acid sites present on the catalyst, the higher its activity and its deactivation.
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    Effect of ethanol addition on soot precursors emissions during benzene oxidation in a jet-stirred reactor
    (Springer-Verlag Berlin Heidelberg, 2014) Rezgui, Y; Guemini, M
    A constant volume reactor model (PSR) was used to investigate the effect of ethanol addition on the formation of some pollutants during benzene oxidation in a jet-stirred reactor. The blended fuels were formed by incrementally adding 4 % wt of oxygen (ethanol) to the neat benzene fuel and by keeping the inert mole fraction (nitrogen) and the equivalence ratio constants. The main objective of this work was to obtain fundamental understanding of the mechanisms through which the oxygenate compound affects soot precursor amounts. The modeling results showed that C2H2, C5H5, and C3H3 mole fractions decreased upon increasing the ethanol percentage in the fuel mixture.
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    Effect of pretreatment conditions on the catalytic performance of Ni-Pt-W supported on amorphous silica-alumina catalysts
    (ELSEVIER, 2008) Rezgui, Y; Guemini, M
    Activation procedures of Ni-W-Pt based catalysts, prepared by means of a hybrid technique: sol–gel and incipient wetness impregnation, were investigated in terms of their activity in reaction of n-hexane isomerization in a continuous fixed-bed quartz reactor operating at atmospheric pressure, by changing operating conditions such as time on stream, SiO2/Al2O3 and H2/n-hexane ratios. This study aims to understand the effects of the pretreatment conditions, such as calcination and reduction temperature, over some properties of these catalysts and to analyze the relationship between the metal content, the acidity (strength) of the samples and their catalytic performance. The chemical composition of the prepared solids have bas characterized by inductively coupled plasma-atomic emission spectroscopy (ICP-AES), their specific surface areas were measured using BET method, while their reduction behavior was characterized by temperature-programmed reduction and their acidity was assessed by means of ammonia temperature-programmed desorption. The collected data revealed that both BET surface areas and catalytic activity as well as surface acidity of these solids are strongly dependent on their pretreatment conditions. Besides, the reduction behavior of the prepared materials was related to nickel and platinum amounts, the higher the concentrations of these species the easier the reducibility of the samples. On the other hand, it was found that all (NixPty) catalysts deactivate with time on stream, with the conversion remaining steady after 100 min. Moreover, the obtained results on (Ni12Pt0,4)AC catalyst showed that the SiO2/Al2O3 ratio and H2 partial pressure affect isomerization selectivity positively while opposite effect was observed for activity (conversion). In addition, the main products in n-hexane hydroconversion were found to be monobranched isomers which dominate all practical conversions and their formation increases together with that of multibranched ones. Besides, the cracked products are not produced in significant amounts until about 30% conversion.
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    Hydroisomerization of n-decane over Ni–Pt–W supported on amorphous silica–alumina catalysts
    (ELSEVIER, 2010) Rezgui, Y; Guemini, M
    A series of NiPtW/silica–alumina catalysts (wt.%: Ni, 12–17; W: 10, Pt: 0.1–1) were prepared via a hybrid method: sol–gel and incipient wetness impregnation and characterized by inductively coupled plasmaatomic emission spectroscopy (ICP-AES), BET, temperature-programmed desorption of ammonia (NH3- TPD), pyridine adsorption followed by FTIR and TPO techniques. On these catalysts, n-decane hydroisomerization was carried out under the following conditions: fixed bed reactor, atmospheric pressure, temperature ranging from 150 to 300 8C, weight hourly space velocity of 4 h1 and molar hydrogen/hydrocarbon ratio of 5. Pt was found to promote activity and stability, the effect being optimal for 0.2 wt.% Pt. Isomers and cracking products yields were a function of both metal (Ni and Pt) content and conversion. Whatever n-decane conversion, monobranched isomers were found to be predominant. Besides, up to 10% conversion, the cracked products were not produced in significant amounts. For a time on stream of 100 min, the best results (47% conversion and 56% isomerization selectivity) were obtained at 250 8C over the catalyst containing 12% Ni, 10% W and 0.2% Pt).
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    Isomerization of n-heptane over Ni–WOx/SiO2–Al2O3 catalysts
    (2003) Rezgui, Y; Guemini, M; Tighezza, A
    Isomerization of n-heptane over Ni–WOx/Al2O3–SiO2 catalysts was carried out in a continuous flow fixed-bed reactor under atmospheric pressure. The first part of this study deals with the preparation of two series of catalysts (A and B) by the sol–gel method, while the second part deals with the isomerization of n-heptane. The principal objective of this study was to choose the catalyst giving the best isomer yield (diand tri-branched ones) with optimum reaction conditions (reaction temperature, reduction temperature and time on stream). From the results obtained, the optimum nickel content was found to be 15 wt% and it seems that the incorporation of tungsten (B series) leads to a significant enhancement in the activity of the prepared catalysts. After running on stream for 100 min, the catalyst with 15% nickel and 10% tungsten (B4 catalyst) gives the best results (29% conversion and 70% selectivity) at 250 8C.