Selahattin Yilmaz

Heterogeneous Fenton-like degradation of Rhodamine 6G in water using CuFeZSM-5 zeolite catalyst prepared by hydrothermal synthesis.

In this study, heterogeneous Fenton-like degradation of reactive azo dye Rhodamine 6G in water was investigated over a CuFeZSM-5 zeolite catalyst prepared by hydrothermal synthesis. At initial pH of 3.4, a color removal of 100% was achieved after a reaction time of 45 min. TOC elimination was measured to be 51.8% after 2 h of oxidation. Initial decolorization rate was described by an equation of -r(A0) = 4.56 x 10(2) e(-24.83/RT)C(R6G,0)C(0.35)(H2O2,0) where R is in kJ/mol. The leaching of iron and copper cations from zeolite structure into the solution during oxidation was dependent on pH strongly. The regulation of pH from 6.5 (dye solution pH) to 3.4, increased leaching for iron from 0.7 to 0.8 mg/dm3 and for copper from 1.4 to 2.1 mg/dm3. The copper was totally leached from the catalyst during the process at pH 3.4.

Fe Containing ZSM-5 Zeolite as Catalyst for Wet Peroxide Oxidation of Orange II

This study presents the catalytic performances of iron containing ZSM-5 zeolites, prepared by ion exchange or hydrothermal synthesis, in catalytic Fenton-like oxidation of Orange II in aqueous solution. The catalyst, ZSM-5 zeolite with Si/Al ratio of 42 loaded with iron by ion exchange, showed the highest activity. The decolorization of 99.7 percent, degradation of 87.0 percent and COD removal of 81.2 percent were achieved over this catalyst at an initial pH of 3.5. Incorporation of iron into ZSM-5 structure increased its catalytic activity. The hydrothermally prepared FeZSM-5 catalyst was more stable against leaching at low pH value due to the iron being in the framework.

Acylation of 2-methoxynaphthalene over ion-exchanged β-zeolite

Friedel-Crafts acylation of 2-Methoxynaphthalene was carried out over various ionexchanged β zeolites (Mn+β, where Mn+: In3+, Zn2+, Al3+, Fe3+, La3+) with various anhydride (acetic, propionic and benzoic anhydrides), or acyl chloride (acetyl, propionyl and benzoyl chlorides) acylating reagents. The results suggested that selectivity towards the 6-substituted products was higher with the larger size anhydrides, propionic and benzoic anhydrides. The metal cation type within the zeolite significantly influenced the extent of conversion and product distribution. That La3+ exchanged zeolite displayed higher selectivity for the 6-position acylated product with anhydrides ascribed mainly to narrowing of channels by the presence of La(OH)2+ ions that leave no room for the formation of more bulky isomeric forms and to enhanced Bronsted acidity of the zeolite. With acyl chlorides, the recovery of ketone products was found to be remarkably low. 1-Acyl-2-methoxynaphthalenes actively underwent deacylation when acyl chlorides were used as the acylation reagent.

Catalytic Activity of Heteropolytungstic Acid Encapsulated into Mesoporous Material Structure

The paper presents a spectroscopic and catalytic study of encapsulated Keggin type heteropoly acid (12-tungstophosphoric acid, HPW) in the mesopores of MCM-41 molecular sieves. Nitrogen physisorption, FTIR, SEM, XRD and catalytic methods have been used to characterize and compare the properties of the samples. Methanol conversion, ?-pinene isomerization and ethyl acetate oxidation have been applied as model reactions for the evaluation of acid site activity. The combined physicochemical and catalytic investigations clearly show that the introduction of 12-tungstophosphoric acid into MCM-41 causes significant changes in the properties of the sample.

Effects of Catalyst Precursor Type and Preparation Conditions, and Solvent Type on Activity and Selectivity of Pt/SiO2 Catalyst in Citral Hydrogenation

In this study, citral hydrogenation reaction in liquid phase over silica gel supported Pt catalysts was investigated. It was desired to hydrogenate carbonyl group selectively to produce valuable unsaturated alcohols, namely geraniol and nerol. Pt/SiO2 catalysts were prepared by impregnation method. The effects of parameters investigated in the present study included Pt precursor type (hexachloroplatinic acid (HCLPA), platinum II acetylacetonate (PAA)), catalyst activation temperature (350°C and 450°C), catalyst activation without calcination, catalyst washing with 0.1 M NaOH and solvent type (ethanol, 2-pentanol). The catalysts activities and selectivities were affected by the type of precursor and activation temperature. The maximum citral conversion (89.50 percent) was achieved at lower activation temperature (350°C) with PAA precursor based catalyst. It was observed that higher activation temperature provided lower citral conversion but higher selectivity to unsaturated alcohols; increasing the activation temperature to 450°C decreased citral conversion to 26.10 percent. But selectivity to unsaturated alcohols, geraniol and nerol, increased from 7.06 to 54.60 percent. Catalyst washing and 2-pentanol prevented acetal formation. Catalyst activation without calcination gave lower citral conversion (20.84 percent) and selectivity to unsaturated alcohols (30.00 percent).

HZSM-5 and H-Ferrierite Acidity Modification by Silylation and Their Activities in n-Butene Isomerisation

H-ZSM5 and H-Ferrierite acidities were modified by chemical liquid deposition using tetraethylorthosilicate (TEOS), silicontetratchloride (SiCl4) and triaminopropyltriethoxysilane (3-APTES). All depositions were carried out at room temperature for deposition times of 0.5 and 1 h. Reaction tests were performed in a tubular quartz fixed bed reactor at 375°C for weight hour space velocities of 22 h-1. Surface area and pore volume of the catalysts were decreased upon modifications. The least modification of acidity was achieved by TEOS. However, SiCl4 and 3-APTES deposition modification strongly decreased the number of Bronsted and Lewis acid sites. As the effect of the modification increased, total acidity of the SiCl4 modified catalyst decreased. The catalysts were tested in isomerization of n-butene. Modification decreased the activity of the catalysts, but improvement in selectivity was observed with TEOS deposition. TEOS deposition increased the selectivity of the catalysts; for synthesized H-ZSM5 from 57.95 to 63.74 percent, for commercial H-ZSM5-C from 26.78 to 32.52 percent, and for H-FER from 63.06 to 81.23 percent. However, modification with SiCl4 and 3-APTES decreased both conversion and selectivity of the parent catalysts.