Samer Aouad

Study of the Ru/Ce system in the oxidation of carbon black and volatile organic compounds

The relationship between the state of Ru on CeO2 and catalytic activity in the oxidation of carbon black (CB) and some volatile organic compounds (VOCs) was investigated for Ru/CeO2 catalysts prepared by wet impregnation. It was demonstrated that the addition of ruthenium to ceria significantly improved the reactivity of the latter. The temperature programmed reduction (TPR) experiments of Ru/CeO2 showed that the oxygen species of RuO2 was reduced at low temperatures. In addition, Electronic Paramagnetic Resonance (EPR) studies of outgassed samples at different temperatures showed an anisotropic signal indicating that Ru(IV) was reduced to intermediate valence states like Ru(III) before its total reduction to metallic Ru. It was concluded that Ru-O-Ce bonds in the well-dispersed Ru species are highly fragile and its mobile oxygen is the active species in the catalytic oxidation process.

Determination and assessment of total mercury levels in local, frozen and canned fish in Lebanon.

Fish is an important constituent of the Lebanese diet. However, very little attention in our area is given to bring awareness regarding the effect of the toxicity of mercury (Hg) mainly through fish consumption. This study aimed to report analytical data on total mercury levels in several fish species for the first time in thirty years and to also made individuals aware of the presence and danger from exposure to mercury through fish consumption. Fish samples were selected from local Lebanese markets and fisheries and included 94 samples of which were fresh, frozen, processed, and canned fish. All values were reported as microgram of mercury per gram of fish based on wet weight. The level of mercury ranged from 0.0190 to 0.5700 microg/g in fresh samples, 0.0059 to 0.0665 microg/g in frozen samples, and 0.0305 to 0.1190 microg/g in canned samples. The data clearly showed that higher levels of mercury were detected in local fresh fish as opposed to other types thus placing consumers at higher risk from mercury exposure. Moreover, the data revealed that Mallifa (yellowstripe barracuda/Sphyraena chrysotaenia), Sargous (white seabream/Diplodus sargus), Ghobbos (bogue/Boops boops), and shrimp (Penaeus sp.) were among the types containing the highest amounts of mercury. On the other hand, processed fish such as fish fillet, fish burger, small shrimp and crab are found to contain lower levels of mercury and are associated with lower exposure risks to mercury. Lebanese population should therefore, be aware to consume limited amounts of fresh local fish to minimize exposure to mercury.

Carbon black oxidation mechanism in loose and tight contacts with Al2O3 and CeO2 catalysts

The catalytic combustion of carbon black was investigated in the presence of CeO2 and Al2O3. The influence of contact type between carbon particles and these oxides was examined by thermal analysis, the BET specific area, and EPR spectroscopy. For tight contact carbon black-catalyst mixtures, a new paramagnetic species is observed and can be considered as a fingerprint of the contact between the two solids. These new paramagnetic species increase the reactivity of the catalytic reaction of carbon black (CB) combustion and take part in the oxidation mechanism of CB.

Hydrogen Production by Methane Steam Reforming Over Ru and Cu Supported on Hydrotalcite Precursors

Co6Al2 oxide was prepared using the hydrotalcite route. The obtained solid was thermally stabilized at 500°C and then impregnated with 5 wt.% copper or 1 wt.% ruthenium nitrate solution followed by calcination at 500°C under an air flow. X-ray diffraction results showed that the calcination of the impregnated solids led to the formation of various oxides (CuO, RuO2, Co3O4, CoAl2O4, CoAl2O4). The different impregnated and non impregnated solids were tested in the methane steam reforming reaction (MSR). Methane conversion did not exceed 5% at 800°C in the case of the non impregnated solid, whereas the impregnation strongly enhanced the reactivity: ~89% and ~92% conversions were reached at 600°C for Cu and Ru respectively. The good reactivity of ruthenium impregnated catalyst was attributed to the formation of easily reducible ruthenium and cobalt oxide species at the surface of the support. The addition of ruthenium made the reduction of surface and bulk cobalt oxides possible at lower temperatures.

Detection of adsorbed O2− species on CeO2 solid impregnated with Ag2+ ions during its thermal treatment under a H2 atmosphere, an EPR study

10% Ag/CeO2 solid was prepared by the impregnation method. When the solid is calcined at 400 °C, three types of Ag2+ species are formed. One of them is more thermally stable compared to the others. The adsorption on the solid of O2 or H2 molecules gives an adsorbed O2- species on the surface, detected by electron paramagnetic resonance (EPR). The mobility of oxygen in CeO2 and the nature of cations loaded on this support can be the origin of the adsorbed O2- species particularly when the solid is treated under H2 molecules.

Physicochemical characteristics, mutagenicity and genotoxicity of airborne particles under industrial and rural influences in Northern Lebanon

In this work, the main objectives were to assess the mutagenic and genotoxic effects of fine particulate matter collected in an industrial influenced site in comparison with a non-industrial influenced one (rural site) and to relate the particulate matter (PM) composition to the observed genotoxic effects. At the industrial influenced site, higher concentrations of phosphates, trace metals, and polycyclic aromatic hydrocarbons (PAHs) in particles could be related to the contributions of quarries, fertilizer producer, cement plants, and tires burning. Gasoline and diesel combustion contributions were evidenced in particles collected at both sites. Particles collected under industrial influence showed a higher mutagenic potential on three tested strains of Salmonella typhimurium (TA98, YG1041, and TA102), and especially on the YG1041, compared to particles from the rural site. Furthermore, only particles collected in the vicinity of the industrial site showed a tendency to activate the SOS responses in Escherichia coli PQ37, which is indicative of DNA damage as a result of exposure of the bacteria cells to the action of mutagenic samples. The mutagenicity and genotoxicity of the industrial PM2.5–0.3 particulates may be attributed to its composition especially in organic compounds. This study showed that proximity of industries can affect local PM composition as well as PM genotoxic and mutagenic potential.

Catalytic Oxidation of Propylene, Toluene, Carbon Monoxide, and Carbon Black over Au/CeO2 Solids: Comparing the Impregnation and the Deposition-Precipitation Methods

Au/CeO2 solids were prepared by two methods: deposition-precipitation (DP) and impregnation (Imp). The prepared solids were calcined under air at 400°C. Both types of catalysts have been tested in the total oxidation of propylene, toluene, carbon monoxide, and carbon black. Au/CeO2-DP solids were the most reactive owing to the high number of gold nanoparticles and Au+ species and the low concentration of Cl− ions present on its surface compared to those observed in Au/CeO2-Imp solids.

Effect of alcohol type and amount on the total energy consumption and yield of the free fatty acids esterification reaction with simultaneous adsorptive water removal

ABSTRACT The present work investigates the energy consumption and yield of the esterification reaction of free fatty acids (waste oil pretreatment) under a simultaneous water removal by adsorption. The reaction was performed under methanol, ethanol, and 1-propanol at the optimum reaction temperature of 100°C. The higher boiling point temperature of 1-propanol reduced the energy requirement of the reaction by 36.3 and 34.4% compared to methanol and ethanol, respectively. Moreover, despite the higher reactivity associated with alcohols having lower carbon chains, the reaction yield was approximately 16.4% higher under 1-propanol than the other two alcohols. This can be ascribed to the ability to use higher amounts of 1-propanol while maintaining lower energy consumption. The results also indicated that the reaction at 100°C under methanol and ethanol had a similar energy consumption and yield, favoring the use of the renewable ethanol over the widely used nonrenewable methanol. Finally, these findings highlight the importance of investigating the energy consumption of novel oil pretreatment processes and not solely focus on their ability to convert free fatty acids to biofuel.

Dry reforming of methane over NixMg6−xAl1.8La0.2 catalysts

Two Ni_xMg_6-xAl_1.8La_0.2 (x=0,2) catalysts were synthesized via hydrotalcite route and calcined at 800°C. For comparison, a second Ni_xMg_6-xAl_1.8La_0.2(x=2) was also prepared via hydrotalcite route but with hydrothermal treatment to evaluate the difference between conventional preparation and preparation with hydrothermal treatment. Physico-chemical characterizations were conducted before and after calcination. These characterization techniques included X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and Temperature Programmed Reduction (TPR). The catalytic performance of these catalysts was also tested in the Dry Reforming of Methane (DRM). Catalytic test results of the more efficient catalyst were compared to the results of a similar NixMg_6-xAl₂ catalyst such as to evaluate the role of lanthanum doping and its impact on the catalytic activity of the catalysts. It was found that the addition of lanthanum resulted in improved catalytic activity in the DRM reaction. This improvement can be attributed to the formation of more basic sites and the presence of La₂O₃ after calcination which reduces coke formation.

Steam reforming of toluene for hydrogen production over NiMgALCe catalysts prepared via hydrotalcite route

Ni_xMg_6-xAl_1.8Ce_0.2 (with 0 ≤ x ≤ 6) mixed oxides catalysts were prepared by hydrotalcite route. All the oxides were calcined at 800°C and characterized by different physicochemical methods and their catalytic performances were tested toward steam reforming of Toluene. In the steam reforming process, reducing pretreatment is a necessary step to activate the catalyst. Ni₂Mg₄Al_1.8Ce_0.2 shows the better toluene conversion and the best performance (H₂ production) among all the catalysts.