Burhanettin Çiçek

Flash pyrolysis of polystyrene wastes in a free-fall reactor under vacuum

Abstract Plastic waste minimization and recycling are important for both economical and environmental reasons. In this flash pyrolysis study, polystyrene wastes were degraded in a free-fall reactor under vacuum to regain the monomer. A set of experiments varied the temperature between 700 and 875°C and determined its effects on the phase yields, the benzene, styrene, toluene, and naphthalene distribution of the liquid output and C1–C4 content of the gaseous output. The liquid yield maximized around 750°C and the styrene yield at 825°C. In general, operating at higher temperatures lessened the solid residue and increased the gaseous yield and total conversion. Employing waste particles in four size ranges, a second set of runs indicated that the finer the waste particles fed the higher the gaseous yield and total conversion. This recycling method can be made more promising if the feed particles are allowed more time for degradation and the removal of the primary products speeded up thereby preventing their decomposition. Ways are suggested to obviate these residence time problems.

Chemical structures of fuel-rich and fuel-lean flames of CCl4/CH4 mixtures

Abstract Temperature and species mole fraction profiles were obtained for atmospheric-pressure, premixed, laminar, flat flames of CCl 4 /CH 4 mixtures under both fuel-lean and fuel-rich conditions. Mole fraction profiles were determined using microprobe sampling coupled to on-line gas chromatography/mass spectrometry for the reactants and for CO, CO 2 , HCl, H 2 O, COCl 2 , CH 3 Cl, CH 2 Cl 2 , CHCl 3 , CCl 4 , C 2 H 3 Cl, 1,1-C 2 H 2 Cl 2 , 1,2-C 2 H 2 Cl 2 , C 2 HCl 3 , 1,1,1,2-C 2 H 2 Cl 4 , C 2 Cl 4 , C 2 Cl 6 , C 2 H 2 , C 2 H 4 , C 2 H 6 , C 4 H 4 , C 4 H 2 , C 6 H 6 , and C 6 H 5 Cl. The role of these species, in view of our current understanding of the mechanism of combustion of CCl 4 and CH 4 , was discussed.

Some DI- and Trinuclear Zinc Complexes: Anion Induced Complex Formation

Abstract Complexes of N,N′-bis(salicylidene)-1,3-diaminopropane, an ONNO type ligand, with ZnX2 (X = AcO−, NO3-, Cl−, Br−, I−) salts were prepared. Molecular structures of these complexes were identified using elemental analyses, IR spectrometry and X-ray diffraction techniques. It has been observed that the reactions between zinc ions and the said ligand tend to produce polynuclear complexes and depending on the anion present either di- or trinuclear complexes are formed. Thus, it can be deduced from the results presented in this article that trinuclear complexes form when the zinc salt used was the acetate or nitrate and dinuclear complexes form if the anion in the zinc salt is a halogen.

INVESTIGATIONS ON SOME HETERO-TRINUCLEAR COMPLEXES OF NICKEL(II) AND COPPER(II)

Ni(II) and Cu(II) complexes of N,N′-bis(salicylidene-1,3-diaminopropane) were prepared and found to form linear and non-linear trinuclear complexes. Elemental analyses, IR spectroscopy, thermogravimetry and X-ray diffraction techniques applied to the complexes yielded valuable information about their moleculer structures. It was observed that μ-bridges in these trinuclear complexes form through the phenolic oxygens of the ligand or through anions present in the medium. In the presence of acetate, nitrate or nitrite, μ-bridges form between a pair of atoms resulting in linear trinuclear complexes. However, the presence of chloride or bromide results in μ-bridges involving the phenolic oxygens of N,N′-Bis(salicylidene)-1,3-diaminopropane.

Desulphurization of coals by flash pyrolysis followed by magnetic separation

Abstract Removal of inorganic sulphur from a Turkish lignite (Tuncbilek) by flash pyrolysis and magnetic separation was investigated. Pyrite is slightly paramagnetic, however, its paramagnetism is not sufficient to affect the separation from coal. Depending on the pyrolysis temperature pyrite, FeS 2 , converts to a variety of iron sulfides, among which the ferrimagnetic pyrrhotite, Fe 7 S 8 , forms at 973 K. In this study, the highest rate of sulphur removal was observed at 923 K. For the particle size of −0.1 mm, a 35% sulphur reduction was achieved by flash pyrolysis and this reduction was further enhanced to 48% by magnetic separation.

Fullerene Production in a Graphite Tubular Reactor

Abstract Effects of operational parameters on the production yield of fullerenes have been detailed by many researchers and up to 20% fullerene yields were attained at optimized pressure, current, and electrode gap. Many of the tests were carried out under static helium pressure and no reference was made to helium flow during the arcing process. It is, however, known that helium flow enhances the fullerene yield. In this study, a tubular graphite reactor was placed into a stainless steel chamber and the arc was generated inside the tubular reactor. Fresh helium was fed at one end of the tubular reactor and vacuum was applied to the other end. Changing the helium flow rate affected the residence time of the particles in the reactive zone. Fullerene yields were obtained to be as high as 32%, which is much above the literature stated values.

SIMULTANEOUS DETERMINATION OF C60 AND C70 FULLERENES BY A SPECTROPHOTOMETRIC METHOD

In all fullerene-producing systems, reaction products were black soot extracts reported to contain a 5–25% fullerene mixture. Toluene extraction of the soot results in a solution of C60, C70, and higherc fullerenes. Without separation, absolute determination of the contents is not possible, leaving the researcher to comment only on the C60/C70 ratio of the solution. High-performance liquid chromatography, nuclear magnetic resonance, and scanning tunneling microscopy imaging techniques were reported in the literature for determining the C60/C70 ratio of the mixtures. These methods require tedious experiments and produce slightly differing results as well. In this communication, a new and relatively quick method is proposed for the simultaneous determination of the yields of C60 and C70 (not the ratio) in fullerene-containing solutions by ultraviolet-visible spectrophotometric analysis.

Chemical structures of fuel-rich, premixed, laminar flames of C6H5Cl/CH4/O2/Ar mixtures

Abstract Chemical structures of atmospheric-pressure, fuel rich (sooting) premixed, laminar, flat flames of C6H5Cl and CH4 have been investigated using a flat flame burner. Species mole fraction profiles were determined by using micro-probe sampling coupled to on-line gas chromatography/mass spectrometry. In addition to those of reactants, mole fraction profiles have been determined for CO, CO2, HCl, H2O, H2, C2H6, C2H4, C2H2, C4H2, C4H4, C5H6, C6H6, C6H5CH3, C6H5C2H3, C6H5C2H, C6H5OH, ClC6H4OH, ClC6H4CH3, C6H4Cl2, and C10H8. In a fuel lean flame of pure C6H5Cl highly chlorinated hydrocarbons such as CCl4, Cl2C6H3OH, C5HCl4, C2HCl3, C6H3Cl3 and C2Cl4 were also observed. The roles of these species, in view of the current ideas of the mechanism of combustion of C6H5Cl are discussed.

Effect of O-methylation on solubility and swelling of coals

Abstract Zonguldak bituminous coal and Mugla–Yatagan, Seyitomer and Bolu–Goynuk lignites were O -methylated with potassium hydroxide–dimethyl sulphate (KOH–DMS) and acetone–potassium carbonate–dimethyl sulphate (acetone–K 2 CO 3 –DMS) methods. Effects of O -methylation on the swelling ratio and on the tetrahydrofuran (THF) solubility were studied. Methoxyl contents of coals were found to be larger after O -methylation with acetone–K 2 CO 3 –DMS (a) while O -methylation with acetone–K 2 CO 3 –DMS (b) resulted in significantly lower methoxyl formation. Coals O -methylated with acetone–K 2 CO 3 –DMS (b), although showed lower methoxyl contents, have comparably larger solubility than those treated according to the other two methods. Yet, no strong correlation with the methoxyl contents of coals and their swelling and solubility can be claimed. It can be reported here that the swelling and solubility, although dependent on the methoxyl content, are greatly influenced by the structure of the coal.

Synthesis of carbon nanotubes by a plasma based pulsed electron beam generator

Carbon nanotubes (CNTs) were synthesized by using a plasma based electron beam generator, which has a fast filamentary discharge formed from the superposition of an ordinary low-pressure dc glow and a high-current pulsed discharge. To our knowledge, CNTs are synthesized for the first time by this method. Acetylene was used as the carbon source and the iron catalyst coated silica substrates were prepared by the sol-gel technique. The silica plates were first coated with an appropriate iron (III) nitrate solution. After calcination and reduction with hydrogen nano iron particles were formed on the plates. The products were collected from two different zones of the e-beam generator. The products were characterized by transmission electron microscopy and Raman spectroscopy.