Cobalt promoted Ni/MgAl2O4 catalyst in lean methane catalytic oxidation

In the present research, magnesium aluminate spinel was prepared as catalyst support using a novel, facile, and efficient mechanochemical method. The Co-promoted catalysts with 20 wt.% of Ni were fabricated using an impregnation route and the samples were analyzed by the X-ray diffraction (XRD), N₂ adsorption/desorption (BET), temperature-programmed reduction and desorption (H₂-TPR and O₂-TPD), and field emission scanning electron microscopy (FESEM) tests. The results confirmed that all samples have a mesoporous structure with a high specific surface area and the presence of cobalt caused complete CH₄ oxidation at low temperatures, and no side reactions were observed. The results indicated that the 3%Co-20%Ni/MgAl₂O₄ catalyst was the optimal sample among the prepared catalysts, owing to the improvement of reduction features and oxygen mobility. The 50 and 90% of methane conversion was obtained at 530 and 600 °C, respectively. Also, the influence of calcination temperature, GHSV, and feed ratio was determined on the catalytic activity. The obtained outcomes revealed that the calcination temperature has a significant effect on the textural properties and catalytic efficiency. The sample calcined at 700 °C showed the weakest performance, which was related to the sintering of particles at high temperatures. The catalytic stability showed that the 3%Co-20%Ni/MgAl₂O₄ has acceptable stability during 600 min time of reaction.

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Development of the ANN–KIM composed model to predict the nanofluid energetic thermal conductivity via various types of nano-powders dispersed in oil

Journal of Thermal Analysis and Calorimetry - Artificial neural network/kriging interpolation method optimization method which is evaluated concerned the hybrid nanofluid composed of iron oxide...     

Headspace SPME–GC Method for Acetone Analysis and its Biomedical Application

A new method for extraction and analysis of acetone in human urine based on headspace solid phase microextraction using a mixture of activated carbon and zeolite as sorbents in a PVC matrix coated on a silver wire and its application to the determination of ketone bodies is described. Unlike commercial fibers, which are coated on fused silica, the coating adheres strongly to the silver wire and is thermally stable up to 250 °C. After optimization of coating composition and microextraction conditions the fiber was used for the analysis of acetone in human urine.     

Thermodynamic properties of transition metals in aqueous solution. 2. The enthalpies of mixing of aqueous solutions of CoCl2, CuCl2, and MnCl2 with NaCl at varying ionic strength at 25°C

Enthalpies of mixing (_m H) aqueous solutions of CoCl₂, CuCl₂, and MnCl₂ with NaCl solutions were measured at constant ionic strengths of 0.5, 1.0, and 3.0 molal at 25°C. The excess enthalpy equations of Pitzer were then fit to the resulting _m H data. The resulting parameters are the temperature derivatives of the activity coefficient mixing parameters in the Pitzer system. The heat of mixing data for CoCl₂ and CuCl₂ were in agreement with earlier isomolal results by other workers.     

The effect of the physical and chemical characteristics of activated carbons on the adsorption energy and affinity coefficient of Dubinin equation

The dependency of adsorption energy (E) and affinity coefficient (beta) of Dubinin equations (Dubinin-Radushkevich (DR) or Dubinin-Astakhov (DA)) on surface chemistry and porosity of activated carbons was investigated by analyzing adsorption of nitrogen, benzene, trichloroethylene (TCE), and water vapor by several surface-modified activated carbons and carbon fibers. For all studied nonpolar adsorbates, carbons with smaller average micropores showed higher adsorption energies independent of their surface chemistry. For water vapor, carbons with higher surface polarities showed higher adsorption energies due to specific adsorbate-adsorbent interactions. Adsorption energies increased with decreasing average micropore widths. betaN2,DR for different carbons were observed to vary in the 0.292-0.539 range. Carbons with higher degrees of mesoporosity had higher betaN2,DR values, while no dependency was observed between betaN2,DR and surface chemistry. A comparison of DR and DA cases indicates that: (1) the average value of betaN2,DA is considerably above the classical value of this parameter; and (2) the range of betaN2,DA values were smaller compared to betaN2,DR, despite a wide range of mesoporosity of carbons examined. Obtained beta(TCE,DR) values varied in the 0.952-1.243 range, with an average value of 1.085+/-0.083, independent of surface chemistry or porosity of activated carbons. A similar result was observed for beta(TCE,DA). betaH2O,DR values of different granular and fibrous activated carbons changed in the range of 0.081-0.271. They depended more on the carbon surface chemistry and less on the porosity. A similar result was obtained when DA equation was considered.     

Joule-Thomson inversion curve prediction by using equation of state

In this paper five equations of state are tested for checking their ability to predict the Joule-Thomson inversion curve.These five equations of state are:Mohsennia-Modarres-Mansoori(MMM),Ji-Lemp(JL),modified Soave-Redlich-Kwang(SRK)equation of state by Graboski(MSRK1),modified SRK equation of state by Peneloux and Rauzy(MSRK2),and modified Peng-Robinson (PR)equation of state by Rauzy(PRmr).The investigated equations of state give good prediction of the low-temperature branch of the inversion curve,except for MMM equation of state.The high-temperature branch and the peak of the inversion curve have been observed,in general,to be sensitive to the applied equation of state.The values of the maximum inversion temperature and maximum inversion pressure are calculated for each component used in this work.     

Semi-micro solvent extraction as a rapid and efficient preconcentration technique for the determination of n-alkanes in oil-contaiminated water and soil samples by capillary gas chromatography

Summary In this study, a rapid and efficient semi-micro extraction procedure is presented for the extraction of some higher n-alkanes from water and soil samples. In the case of water samples n-hexane was used as the organic phase in a phase volume ratio (volume of aqueous phase/volume of organic phase) higher than 285, while in the case of soil samples, extraction with n-hexane was carried out in the presence of an excess of 2 M NaCl solution. The extraction rate from soil samples is very high and is better than Soxhlet extraction, comparable with supercritical fluid extraction. High preconcentration factor in water samples allows the limits of detection to be in the ng.mL⁻¹ level with the use of gas chromatographic analysis. Flame ionization detector was used for monitoring the analytes. The obtained recoveries of all studied compounds from both water and soil samples are higher than 90%. This method was successfully used to determine some n-alkanes in municipal wastewater and contaminated soil.