Ahmet Alicilar

Improvement of Diesel fuel properties by using additives

Abstract In this study, organic compounds of Mn, Mg, Cu and Ca metals were synthesized, and their solutions were used as Diesel fuel additives. The additives that achieved the greatest decrease in freezing point of Diesel fuel, its optimum rate of dosage and other performance effects were tested. The results showed that the organic based manganese gave the greatest decrease in freezing point. This additive reduced the freezing point to 12.4°C at the rate of dosage of 54.2 μ mol Mn/l Diesel fuel. It was established that the cetane number of Diesel fuel without the additive was 46.22, whereas the cetane number was 48.24 for Diesel fuel with the optimum amount of dosage. It was observed that the organic based manganese drops the viscosity and flash point and improves the contents of the exhaust gases.

The relation between wetting efficiency and liquid holdup in packed columns

Liquid holdup and wetting efficiency in packed columns were determined using a tracer method. A new model was developed considering axial dispersion, and analysis was made using the moment technique. The saturated solution of KG was used as an inert tracer and total liquid holdups were determined in the first part of experiments. As an adsorbable tracer, dioxane was utilized in the second part of the work and wetting efficiencies were obtained. Adsorption equilibrium constant was determined by the experiments conducted in a liquid full bed. A model proposed between liquid holdup and wetting efficiency gave good agreement with the experimental results. Axial dispersion effects were also taken into account during the work. It was also shown that axial dispersion of liquid phase should be considered especially in the small scale trickle bed reactors. @KEYWORDS:Packed beds,Wetting efficiency,Liquid holdup,Tracer method,Moment technique,Trickle bed reactors.

The removal of cyanides from water by catalytic air oxidation in a fixed bed reactor

The removal of cyanides from water by catalytic air oxidation was studied. Experiments were separately performed in a fixed bed reactor with co- and counter-current flow. Effects of concentration, flow type, liquid and gas flow rates on oxidation yield were investigated. It was consequently observed that the yield was increased with decreasing gas flow rate. The yields attained at countercurrent conditions were higher than those of cocurrent ones. The yield was not significantly affected by the change in concentration and liquid flow rate. The reaction was found to be of zero-order with respect to cyanide in water. Although this study was carried out at a continuously operating system, a yield of 99% was achieved at low gas flow rates and countercurrent conditions.

Phase Transitions, Order Parameters and Threshold Voltages in Liquid Crystal Systems Doped with Disperse Orange Dye and Carbon Nanoparticles

At the first part of this work, three different textile dyes (disperse orange 11, 13 and 37) were separately doped (1% w/w) to the nematic liquid crystal (E7). Single‐walled nanotube and fullerene C60 in a small amount (0.05% w/w) were mixed to these solutions at the second stage. Order parameters, threshold voltages, textures and clearing temperatures for all of mixtures were determined. Co‐use of dyes and nanoparticles as dopant was resulted in notable increases in order parameters. While threshold voltages required for the change of order parameter decreased, an important change in the texture and clearing temperature of the liquid crystal was not observed.

Alignment and Reorientation in Nematic Liquid Crystals Doped with Red Dye and Carbon Nanotube

Four different dyes (Methyl red, Disperse red 1, 13 and 60) were separately doped to each of four different nematic liquid crystals (E7, E8, E63 and ZLI-1132). Their solubilities, textures, phase transition temperatures and order parameters were determined. At the second stage, single-walled nanotubes in a small amount were separately added to each of these solutions, and the experiments were repeated as similar to previous ones. The solubility of dyes was sufficient for using in experiments. When adding dyes and nanotubes, an appreciable change in textures of liquid crystals was not observed. The phase transition temperatures stayed within the limitations required. The changes observed in order parameters depending on the voltage were very small. The highest value of order parameter (0.77) was attained when co-using red 60 dye and nanotube as dopants in the liquid crystal E63.

Orientation in Nematic Liquid Crystals Doped with Orange Dyes and Effect of Carbon Nanoparticles

Some properties of nematic liquid crystal E7 doped with two disperse orange dyes used together and effect of addition of carbon nanoparticles (single walled carbon nanotube or fullerene C60) on them were studied. Two dyes (disperse orange 11 and 13) having high solubility and order parameter were used as co-dopants. A notable increase in order parameter was obtained comparing to that of liquid crystal doped with single dye. When carbon nanoparticles were used as dopant, a decrease in order parameter was observed at low temperatures while it increased at high temperatures. When applied voltage changed, the order parameter abruptly increased in its threshold value and saturated in higher voltages as expected. An appreciable change in textures was not observed with addition of dopants. This addition gave rise to an increase in nematic-isotropic phase transition temperatures compared with that of pure liquid crystal.

Effects on molecular orientation and phase transition of addition of carbon nanotubes into liquid crystalline matrix

For practical guest–host applications, it is important to choose dyes with a high ability of orientation in the liquid crystal (LC) matrix. In this experimental work, two different azo-structured dyes (disperse yellow 3 and 7) were separately doped to each of two different nematic LCs (E7 and ZLI-1132). Their solubilities, textures, phase transition temperatures and order parameters were determined. At the second stage, single-walled carbon nanotubes (SWCNTs) in a small amount were separately added to each of these solutions, and the experiments were repeated as similar to the previous ones. The solubilities of dyes in the LC E7 were lower than those of ZLI-1132. Moreover, the highest order parameter value was attained with yellow 7 dye in ZLI-1132 nematic host. Co-use of nanoparticles (CNTs) as dopant resulted in notable increases in order parameters. These dyes and CNTs did not significantly destabilise the mesomorphic phase of nematic hosts. An appreciable change in textures was not monitored with addition of dopant(s). In addition, it was observed that the narrowing on the temperature range of the LC did not take place with the addition of dopants to the crystal; on the contrary, an increase was recorded.

Cellulosic tent fabric coated with boron nitride nanosheets

This study concerns with the preparation of flame retardant and hydrophobic cellulosic fabric by using hexagonal boron nitride nanosheets (h-BNNs). h-BNNs were prepared from hexagonal boron nitride (h-BN) using two different exfoliation methods. These methods include direct sonication (aq-BNNs) and sonication after pretreatment with Hummers method (Hum-BNNs) in aqueous medium. The characterization of h-BNNs was carried out by x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), limited oxygen index (LOI), and water contact angle (WCA) analysis. The surface morphologies of h-BNNs were investigated via atomic force microscope (AFM). The coating with the h-BNNs was proved by scanning electron microscopy (SEM). Hummers method is considered to be more effective reaction by gained functionality to h-BN structure. In this way, it will easily provide physical or chemical interaction between the functionalized h-BN and cellulosic structure. A nanometric-sized large layers and slightly functionalized h-BNNs were obtained using Hummers method. Hum-BNNs dispersions were sprayed onto the surface of cellulosic tent fabric to show flame retardance properties. However, it was observed that the flame retardant effect of nanolayered h-BNNs prepared by both methods were insufficient. In addition, ultrahydrophobic surfaces were almost obtained using aq-BNNs and Hum-BNNs. It was conclusively proposed that a few amounts of Hum-BNNs can be used as hydrophobic coating for cellulosic fabric surface with this way.

Air Oxidation of Aqueous Cyanides in a Countercurrent Fixed Bed Reactor

This study was conducted to discuss the removal of cyanides from water by air oxidation. Experiments were carried out in a countercurrent fixed bed reactor for three different values of temperature, concentration, gas and liquid flow rates. It was operated at pH 12 by using delrin (formaldehyde polymer) as packing material. Effects of some operating parameters on the conversion were studied, and it was observed that the conversion percent increased by increasing temperature and decreasing gas and liquid flow rates. Effect of concentration was not steady. A conversion of 89% was achieved under optimum conditions while it ranges from 44 to 79% at room temperature.

Removal of Cyanides from Water by Air Oxidation in a Cocurrent Downflow Fixed Bed Reactor

A method for removal of cyanides from water is described. The method involves the air oxidation of cyanides in a fixed bed reactor with cocurrent downflow. Effects of parameters such as temperature, concentration, gas and liquid flow rates on the oxidation yield are studied. It was observed that the yield increases by increasing temperature and decreasing gas and liquid flow rates. Altering the concentration had no clear effect on the yield. A yield of 86 % was achieved at high temperature (60°C) while the maximum yield was 68 % at room temperature.