Suna Balci

Ammonium ion adsorption with sepiolite: use of transient uptake method

Extent of environmental pollution is increased by technological development. Especially in industrialized areas, ecological equilibrium is affected by wastewater formed with industrial wastes. The more important pollutants for water are nitrogen compounds, which are threatening the human health. Ammonium removal from solution was investigated using Turkish sepiolite, having average particle dimension of 2.05 mm. Ammonium uptake experiments for two different adsorbent quantities were performed for the solutions having initial solution concentrations in the range of 8.333–222.23 mmol NH4+/l, and equilibrium isotherms were performed at 25°C. Around 60% ammonium removal, of which 90% was achieved within 500 s, was observed. Maximum adsorbed amount was 3.50 mmol NH4+/g. The exponential decrease model for the variation of the solution concentration with time, gave reasonably good agreement with the experimental data. The effective diffusion coefficients were estimated around 1.4×10−10 m2/s.

Thermal decomposition of sepiolite and variations in pore structure with and without acid pre‐treatment

Sepiolite is a high surface area clay mineral containing channels of molecular dimensions. In industrial applications as an adsorbent or catalyst support, the mineral should have thermal stability. In this study, the effect of heat treatment on sepiolite structure was investigated. Thermal decomposition of raw sepiolite and acid pre-activated sepiolite samples were carried out with a thermogravimetric analyser. Approximately 24% weight loss was observed till 900°C. This value decreased to 14% for acid pre-treated samples. The surface area value of the original sepiolite was 148 m 2 g -1 , and it increased to 263 m 2 g -1 at 100°C. Further increase in temperature caused channel plugging and crystal structure deformation, as a result the surface area values showed a decrease with temperature. On the other hand, acid pre-treatment caused a change in pore size distribution by increasing the surface area 2.5 times. Acid pre-treatment also restricted the possible crystal structure deformations during temperature changes. While the surface area of the original mineral which was heated up to 900°C was 60 m 2 g -1 , the corresponding value of the acid pre-treated sepiolite was 360 m 2 g -1 .

Sulfation reaction between SO2 and limestone: application of deactivation model

Abstract Among the several efficient methods for in combustion sulfur dioxide removal methods, sulfation with carbonate based systems are the most widely used one due to its low cost. In this study sulfation reaction kinetics was investigated using limestones of different origin. Limestones pre-calcinated at 900°C in inert atmosphere were subjected to 0.35% by volume SO2. It was observed that sulfation reaction rate was high in the early stages. The conversion for the sulfation of Kinik and Goynuk limestones increased with increasing reaction temperature. For temperatures of 850°C and lower the sulfation reaction was in kinetic control regime. The occurred pore plugging caused a considerable decrease in the rate of sulfation with the extent of the reaction under the all studied conditions. For the sulfation reactions carried out at high temperatures, the model estimating the increase of activation energy with conversion were found to be in agreement with the experimental data. Activation energies of the sulfation reactions for Kinik and Goynuk limestones were estimated around 12 179 and 11 543 cal/mol, respectively. Deactivation model gave good estimates of the conversion especially at high sulfation reaction temperatures.

Effects of drying methods and calcination temperatures on the physical properties of iron intercalated clays

In this study, intercalation of the bentonite clay mineral mined from Middle Anatolian was studied using iron pillar agents. Effects of the pillar solution preparation methods on the quality of the pillared intercalated layered clays (PILCs) and the variations in the pillared structure with drying types and calcination temperatures were investigated. Thermal behaviors of the starting mineral and the final product were investigated by thermogravimetric technique. Fe-PILC showed a more and lasting weight losses. Surface areas of the samples were measured using nitrogen sorption technique under continuous nitrogen–helium flow. Fe-PILC product having basal spacing as 13.79 A was obtained at 100 °C. The reasonably high surface area, which was measured as 95 m2 g−1 at 450 °C, confirmed that the preserving of thermal stability.

Activity Comparison of MCM-41 and V-MCM-4 Catalysts for Ethanol Selective Oxidation and DRIFTS Analysis

The activity of a V-MCM-41 catalyst with a V/Si molar ratio of 0.04 was compared with the activity of a pure MCM-41 catalyst and some DRIFTS studies were performed in order to understand the mechanism of selective oxidation of ethanol. V-MCM-41 was found to be much more active than pure MCM-41, favouring the formation of high amounts of ethylene over 300°C. MCM-41, on the other hand, was found to favour the formation of acetaldehyde over ethylene at all studied temperatures. It was shown by reaction findings that over V-MCM-41, ethylene was produced mainly in the presence of gas phase oxygen whereas acetaldehyde was produced using the lattice oxygen even in the absence of gas phase oxygen. DRIFTS studies indicated the formation of acetaldehyde molecules from acetate-like surface species which were formed by the removal of a hydrogen atom from the ?-carbon of chemisorbed ethoxy species by the help of the lattice oxygen. On the other hand, removal of a hydrogen atom from the ?-carbon of the ethoxy species, in the presence of gas phase oxygen, resulted in the formation of vinyl-like surface species which then yielded ethylene molecules.

Catalytic properties and activity of copper and silver containing Al-pillared bentonite for CO oxidation

W carried out the research on the supported gold nanoparticles catalyzed aminolysis of ester with inert tertiary amine by C-O and C-N bond activations. Compared with homogeneous catalyst-Pd(OAc)2, the most outstanding feature of supported Au nanoparticles catalyst is their superior ability in catalyzing aminolysis reactions at room temperature. And the catalytic performance of AuNPs didn’t apparently decreased even after recycling five times. On the other hand, we carried out the research on the supported palladium nanoparticles catalyzed ortho-directed CDC reaction of alkylbenzenes and orthodirected CDC reaction of aldehydes. It is found for the first time that metallic state palladium, Pd0, can catalyze the orthodirected CDC reaction of alkylbenzenes or aldehydes for the synthesis of aromatic ketones via a Pd0/PdII/PdIV catalytic cycle.β Cβ-tetrasubstituted α-amino acid derivatives are commonly serviceable structural motifs in biologically active natural products and pharmaceuticals. Several efficient methods have been established to construct β-tetrasubstituted α-amino acids. Nevertheless, a rapid access to construction of these complex molecules from simple starting materials under mild conditions are urgently in demand. Multi-component reactions (MCRs) have provided such an approach to realize this goal. Here, a synergistic rhodium(II)/phosphoric acid catalyzed three component reaction of 3-diazooxindoles, alcohols and N-benzhydryl-α-imino ester is successfully developed to provide an efficient strategy for the rapid construction of chiral β-alkoxy Cβ-tetrasubstituted α-amino acid derivatives with high diastereoselectivity (up to 20:1 dr) and excellent enantioselectivity (up to 98:2 er) from simple starting points under mild conditions (Scheme 1). The resulting multi-component products 4 readily afforded 3-spirocyclic oxindole 5 under the standard hydrogenation conditions followed a cyclization with CSCl2 in a good yield remaining excellent enantioselectivity.W have been exploring the selective functionalization of unactivated hydrocarbons. We have developed a catalytic enantioselective allylic amination of unactivated olefins via a [2,3]-rearrangement (Scheme 1). In this method, a diimido-sulfur reagent serves as the source of nitrogen, and it reacts selectively with terminal olefins through a hetero-ene reaction. The resulting zwitterionic ene adduct undergoes a Pd-catalyzed enantioselective [2,3]-rearrangement to generate chiral amines in high enantiomeric excess. Our approach is conceptually distinct from other enantioselective allylic amination strategies. The synthetic utility of our process is being explored by converting simple and inexpensive terminal olefins into functional materials, such as the pharmaceutical drugs Vigabatrin and Januvia. Based on this chemistry, we have also developed a copper-catalyzed allylic alkylation of unactivated olefins and dienes (Schemes 2 and 3). This represents a general method for functionalizing unactivated hydrocarbons with aromatic, aliphatic, and vinyl Grignard reagents. Our recent discoveries represent a conceptual framework for the generalized functionalization of unactivated olefins. Scheme 1. Allylic Amination of Unactivated OlefinsR and enantioselective photodimerization of naphthols and derivatives is attained within a chiral Ru(II)-metalloligandbased palladium(II) nanocage for the first time. The chiral octahedral Ru(II) catalytic centers on the ΔΔΔΔΔΔΔΔ-/ ΛΛΛΛΛΛΛΛ-cage walls convert naphthol derivatives into the exclusive S-/R-napthoquinone products with much higher chiral induction in comparison to the chiral RuL3 catalysts in bulk solution. The enhanced stereoselectivity is rationalized by the interplay of confined-space effect and aryl-aryl interactions between host and guest, which could stereo-control the transition state structures. The reaction mechanism has been investigated by Electron Spin Resonance (ESR) spectra, Cyclic Voltammetry (CV), UV/Vis absorption and fluorescence spectra. The results support the fact that the Ru(II) cage undergoes photoexcitation and subsequent oxidation by O2 to give OH radicals and a Ru(III) intermediate cage. The Ru(III) intermediate is then capable of oxidizing naphthol substrate and removing an electron to provide the arene radical species, which is coupled with OH radical to give the naphthalene-1,2-dione intermediate, followed by rearomatization with the arene radical, and then form a C-C bond to obtain the napthoquinone product without any significant observable byproduct. This dimerization reaction constitutes a very rare example of high asymmetric induction in oxidative biaryl coupling from a chiral photocatalyst, which closely resembles to biological systems.