İrfan Ar

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.

Kinetics of H2S Sorption on Manganese Oxide and Mn-Fe-Cu Mixed Oxide Prepared by the Complexation Technique

Hydrogen sulfide sorption activities of manganese oxide and Mn-Fe-Cu mixed oxide sorbents were examined in a fixed bed reactor. Sulfur retention capacity of Mn-O sorbent was found to be quite high at 600 °C both in the absence and presence of hydrogen gas (0.17 and 0.14 g S/g sorbent, respectively). This sorbent has a high porosity and a relatively high surface area. Best regeneration temperature of this sorbent was found as 700 °C, with a gas stream containing 6% oxygen in nitrogen. Mn-Fe-Cu mixed oxide sorbent had a lower sulfur retention capacity (0.07 g S/g sorbent). However, both of these sorbents gave quite high initial sorption rate constants, resulting very sharp breakthrough curves. Deactivation model was shown to give good agreement with the experimental H2S breakthrough curves.

Synthesis of Magnesium Borohydride from Its Elements and Usage in the Hydrogen Cycle

Abstract In this study, magnesium borohydride synthesis was studied for the storage and transportation of hydrogen. Synthesis was carried out by using elemental magnesium and boron by a ball-milling method. The effects of the magnesium-boron ratio and pressure on the hydrogen storage capacity of the synthesized hydride were investigated. It was observed that an increase in the pressure causes a significant increase in the hydrogen absorption of the hydride. The amount of hydrogen evolved in the catalytic method was found to be 100 times higher than the hydrogen evaluation in the thermal method. It was also observed that the amount of hydrogen evolved in the catalytic method is three times higher than the hydrogen absorbed by the hydrides. This result may be explained by the hydrolysis of the water, which was used for hydrogen desorption from the metal hydride.

Development of Low Cost Heterogeneous Catalysts for Biodiesel Processes

Abstract Although homogenous catalysts result in higher yields in biodiesel processes, a multitude of factors, such as saponification, excess reactant consumption, and additional separation costs, present disadvantages. Hence, we are witnessing an increase in efforts to implement high yield, reusable, non-saponifying heterogeneous catalysts. In the present work, possible use of a low cost volcanic tufa-based catalyst as a support material in the methyl ester reaction was studied and the results were compared with the yields obtained with MCM-41. KI and Mg (NO3)2 were loaded onto this support by soaking. Effects of temperature, concentration, methanol to oil ratio, reaction time, support materials, particle size distribution, and nature of the active material on esterification yield was studied. The highest yield was obtained with a catalyst of a 500-μm particle size volcanic tufa prewashed with pure water and loaded with 90 mg KI/g oil active material. The most suitable reaction conditions were found with 0.08 g support/g oil catalyst at 1.1 g methanol/g oil reaction medium at 220°C and reaction duration of 3 h when a methyl ester yield of 91.06 was obtained.

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.