Sonocatalytic oxidative desulfurization of thiophene and its derivatives

Currently, the sulfur level in diesels is limited to 10 and 15 ppm in Europe and USA respectively, since the organosulfur compounds available in fuels emit corrosive SO2 gases into atmosphere during combustion, thus leading to acid rain. A lot of processes such as hydrodesulfurization (HDS), oxidative desulfurization (ODS) etc. have been used to reduce sulfur level in fuels and ODS, which is alternative to conventional HDS, is much more efficient in removing benzothiophene (BT), dibenzothiophene (DBT) and their alkyl derivatives as compared with HDS and more economical. One of very powerful oxidation systems used in ODS is H2O2-formic acid and removal of alkyl-substituted derivatives of T, BT and DBT with this oxidation system is easier than that with H2O2-phosphotungstic acid catalyst system due to the steric hindrance of alkyl groups adjacent to sulfur atom because phosphotungstic acid is a bulky catalyst. In this work, oxidative desulfurization reactions of the model compounds, thiophene (T), 2-methylthiophene (2-MT) and 2,5-dimethylthiophene (2,5-DMT), which have the lowest reactivity in ODS, on sonication at low H2O2 (O) / F (formic acid) / S (organosulfur solution) volume ratios were carried out sequentially in the presence of tetrabutylammonium bromide (TBAB) as phase transfer catalyst at 30 and 40 degrees C. First, the solution of the relevant model sulfur compound in n-heptane was put into a steel batch reactor and later, reactions were performed by adding mixture of 35 % H2O2, formic acid and TBAB onto the organic phase. After each reaction cycle, the aqueous phase was removed by a separation funnel and the oxidative desulfurization reaction of the remaining treated organic phase was repeated three or four times with reuse of the same amounts of fresh hydrogen peroxide, formic acid and TBAB as in the first reactions at 30 and 40 degrees C for 15 min. After every reaction cycle, the sulfur compounds in heptane were analyzed by using GC with Sulfur Chemiluminescence Detector. Afterwards, the oxidative desulfurization reactions of the model sulfur compounds in heptane were performed for only one cycle in sonoreactor with total amount of oxidation reagents H2O2, formic acid and the same amount of TBAB used in the former multi-cycle reactions at 30 and 40 degrees C for 15 and 60 min. It was observed that the total conversions of model sulfur compounds obtained from multicycle reactions were higher than its conversions obtained from single-cycle reactions with total amount of oxidation reagents used in the multicycle reaction. The same method was also applied to diesel fuel sample and it was shown that high sulfur removal is reached. (C) 2012 Published by Elsevier Ltd

Investigation of glass transition temperatures of Turkish asphaltenes

Asphaltenes are a major concern in production operations, due to their role in conversion of vacuum residues by processes such as coking, catalytic cracking and hydroconversion. Six Turkish asphaltenes were characterized by elemental content, proton NMR, carbon NMR, GPC, DSC. Differential scanning calorimetry (DSC) provides parameters for comparing the glass transition temperatures, endothermic behavior of asphaltene and a hypothetical melting temperature of the asphaltenes which is within the range of the pyrolysis temperature of asphaltenes. The glass transition temperatures points (T-g) of asphaltenes were determined using DSC. Hypothetical melting point temperature (T,,,) of the asphaltenes was also calculated. Among all the asphaltenes tested, Bati Raman showed much higher glass transition temperatures than the others. (c) 2007 Elsevier Ltd. All rights reserved

The effects of fatty acids on the particle size distribution of the Portland cement

The cement has to be ground fine enough and have the optimum particle size distribution (PSD) to meet the requirements such as strength properties and setting times in current standards. As it takes quite a long time to determine especially the late strength, grinding has to be based on the cement fineness and the PSD. In this study, the effects of fatty acids were investigated on the PSD of Portland cement. Experimental results showed that the fineness of the cement was decreased for that replaced with 0.025 wt.% lauric acid (LA), myristic acid (MA) and sunflower oil acid (SO), then increased for the other additions. The fineness measurements revealed that the cement grains aggregated for an amount of 0.025 % (w) during the grinding. Also, when the PSD of the ground cement is examined, the relationship between the saturated and the unsaturated components is evident that milling the cement clinker together with 0.1% (w) LA and 0.1 wt. % MA gave the finer cement from that with 0.1 wt.% SO

Catalytic dehydrogenation of tetradecanol over copper/barium oxide catalysts

The liquid phase dehydrogenation of tetradecanol to tetradecanal has been studied over a series of CuO/BaO catalysts. Catalytic activity and selectivity to tetradecanal was found to depend on the ratio of easily reducible copper sites to less easily reducible copper sites. The catalysts have been characterized by X-ray diffraction, temperature programmed reduction, and thermo-gravimetric analysis. TPR results have shown that there were at least two types of copper oxides with varying reducibility. The relationship between the activity and area ratio of various copper oxide sites and a scheme for the conversion of tetradecanol were discussed

Preparation and characterization of Ni based catalysts for the catalytic partial oxidation of methane: Effect of support basicity on H-2/CO ratio and carbon deposition

The catalytic partial oxidation of methane (CPOM) was studied on Ni based catalysts Catalysts were prepared by wet impregnation method and characterized by using AAS BET XRD HRTEM TPR TPO Raman Spectroscopy and TPSR techniques The prepared catalysts showed nearly 95% CH4 conversion and nearly 96% H-2 selectivity under the flow of 157 500 (L kg(-1) h(-1)) with the ratio of CH4/O-2 = 2 by using air as an oxidant at 1 atm and 800 C Support basicity greatly influenced the H-2/CO ratio and carbon deposition It was found that the lowest carbon deposition occurred on Ni impregnated MgO catalyst Considering the results it was found that Ni/MgO catalyst with 10% Ni content would be the best catalyst amongst Ni/Al2O3 Ni/MgO/Al2O3 Ni/MgAl2O4 and Ni/Sorbacid for the CPOM only under more reductive conditions Under optimum conditions Ni/MgO showed poor performance and therefore Ni/Sorbacid would be the ideal catalyst because of its greater carbon resistance than the other catalysts (C) 2010 Professor T Nejat Veziroglu Published by Elsevier Ltd All rights reserve

Effect of the calcination temperature on Ni/MgAl2O4 catalyst structure and catalytic properties for partial oxidation of methane

Effect of calcination temperature on Ni/MgAl2O4 catalyst was investigated in order to evaluate changes on structural and catalytic properties for catalytic partial oxidation of methane. The catalysts were calcined at different temperatures after impregnation of nickel salt solution on MgAl2O1 support. The prepared catalysts showed nearly 89% CH4 conversion and 99% H-2 selectivity under the flow of 157,000 (l kg(-1) h(-1)) with the ratio of CH4/air = 0.44 at 1 atm and 800 degrees C. However, turnover frequency values of the catalysts were between 8.2 and 42.3 s(-1) and increased according to Ni particle size. Lewis basicity/acidity ratio increased from 2.14 to 4.46 with increasing calcination temperature. It was found that coking rate on the catalysts depends on Ni particle size and surface basicity/acidity. The experimental results showed that calcination temperature and time have a significant influence on both structural and catalytic properties of the catalysts that show strong metal oxide support interaction. It could be claimed that high calcination temperatures could be beneficial to obtain highly active, selective and stable Ni/MgAl2O4 catalysts, which possess strong metal oxide support interaction, by maintaining Ni dispersion high after reduction, increasing surface basicity and enhancing the stability of Ni particles against sintering. (C) 2013 Elsevier Ltd. All rights reserved

Studies on oxidative coupling of methane using Sm2O3-based catalysts

The effects of Mn/Na2WO4, Li, and CaO loading on the monoclinic Sm2O3 catalyst were investigated for the oxidative coupling of methane using O-2 or N2O as an oxidant. The catalysts were prepared by wet impregnation method and characterized by XRD, BET, CO2-TPD, and XPS analysis. Impregnation of Mn/Na2WO4 on monoclinic Sm2O3 resulted in the formation of Sm2-xMnxO3 phase, decreasing the catalytic performance. Li impregnation increased the C-2 selectivity but decreased the catalytic activity. The SmLiO2 formation increased the catalytic activity and selectivity. High amounts of CaO impregnation increased the C-2 selectivity of monoclinic Sm2O3 without a loss in catalytic activity. 6Li/m-Sm2O3 were found unstable due to the Li loss from the catalyst. The 15CaO/m-Sm2O3 was quite stable and showed 8.2% ethylene yield with N2O use, much higher than that was obtained with the well-known 2Mn/5Na(2)WO(4)/SiO2 and 4Li/MgO catalysts. N2O was more selective than O-2 as an oxidant and enhanced ethylene formation

The preparation and characterization of poly(acrylic acid-co-methacrylamide) gel and its use in the non-competitive heavy metal removal

Poly(acrylic acid-co-methacrylamide), P(AA-co-MAAm), and poly(acrylic acid), PAA, gels were prepared and the use of these gels in the non-competitive removal of Pb(2+), Cu(2+), and Cd(2+) ions from aqueous solutions was investigated at room temperature. Characterization of the polymers was performed by FTIR spectroscopy both before and after adsorption of metal ions on P(AA-co-MAAM) or PAA. The equilibrium swelling values (ESVs) of both polymers were determined by gravimetric method. During the adsorption of metal ions on both polymers, residual metal ion concentration in the solution (by atomic absorption spectrophoto meter (AAS)) and the solution pH were measured. The kinetics of the adsorption process was determined from the experimental results. Pseudo-first and second-order plots and the correlation coefficients showed that the kinetics of non-competitive adsorption of Pb(2+), Cu(2+), and Cd(2+) ions on P(AA-co-MAAM) or PAA is correlated best with pseudo-second-order process. While the removal order in the non-competitive adsorption of heavy metal ions on PAA was Pb(2+) (2.60 mmol g(-1)) > Cu(2+) (1.04 mmol g(-1)) > Cd(2+) (0.88 mmol g(-1)), it was in the order of Pb(2+) (1.85 mmol g(-1)) > Cd(2+) (0.70 mmol g(-1)) > Cu(2+) (0.64 mmol g(-1)) for P(AA-co-MAAM) copolymer. The introduction of MAAm into PAA decreased the metal ion removal capacity of copolymer for Pb(2+) and Cu(2+) ions considerably, but it did not significantly affect that for Cd(2+) ion. Copyright (C) 2008 John Wiley & Sons, Ltd

Preparation and characterization of Ca-Sm-Ce mixed oxides via cellulose templating method for solid oxide fuel cell applications

SmxCa0.2 xCe0.8Oy materials are synthesized by changing mol ratios of the composition as x ¼ 0, 0.05, 0.1, 0.15 and 0.2, respectively, with a fast and facile cellulose templating method for the ? rst time. Micro- structures of the calcined and sintered samples are characterized by XRD and SEM-EDX. Density measurements are actualized by using Archimedes method. The electrical conductivity of the samples is obtained from two-probe impedance spectroscopy. Maximum solubility limit of CaO in CeO2 is found to be 9.4 mol% from the XRD results. Incorporation of CaO slightly increases the sinterability of the samples. It is observed that Smþ 3 expands the CeO2 lattice more than Caþ 2. 10 mol% CaO incorporated sample show the highest total conductivity with the value of 0.032 S cm 1 at 800 C. Obtained results show that Sm0.1Ca0.1Ce0.8Oy can be an excellent candidate for intermediate temperature solid oxide fuel cell applications due to its lower cost and higher performance compared to Sm0.2Ce0.8Oy at 800 C. Addi- tionally, cellulose templating method can be used as an effective method in order to prepare mixed oxide structures since the performances of the samples are higher than the samples which are prepared by more complex or costly hydrothermal and co-precipitation methods in literature

Effect of sol-gel modifications on formation and morphology of nanocrystalline lanthanum aluminate

Oksuzomer, Faruk/0000-0003-0827-8667; Koc, Serkan Naci/0000-0003-4472-4337WOS: 000242522000015LaAlO3 powders are prepared by sol-gel method. The effect of preparation conditions on morphological properties and crystal formations are investigated. iso-Propanol/tert-butanol and ethyl acetoacetate/ethylene glycol monomethylether are used solvents and complexing agents, respectively. Samples are dried with conventional and freeze-drying methods and calcined between 600 and 1000 degrees C. TGA, DTA, XRD, SEM and TEM methods are used for characterization. It is observed that freeze-dried sample prepared with tert-butanol has the lowest LaAlO3 formation temperature and uniform rhombohedral crystals. But conventionally dried sample, prepared with iso-propanol has smallest agglomerates at 1000 degrees C and does not show clear crystallization temperature in DTA analysis. The XRD peaks of LaAlO3 crystal are observed at 600 degrees C for all samples prepared by various sol-gel conditions. (C) 2006 Elsevier Ltd. All rights reserved