IRANIAN JOURNAL OF SCIENCE AND TECHNOLOGY TRANSACTION B- ENGINEERING
Year:2006 | Volume:30 | Issue:B5|Papers Count:6

Unsymmetrical dimethyl hydrazine (UDMH) is a strong propellant, which due to its very good physical properties and high power of repellency has been utilized as a liquid fuel for fighter jet engines for so many years. There are different methods for production of this material.One of the more efficient ones which results in higher yields compared to others is the catalytic hydrogenation of Nitroso Dimethylamine (NDMA). In this work hydrogenation of NDMA to UDMH on a 5% Pd/C in aqueous solution of NDMA was studied experimentally. Experiments were carried out in a Semi-batch three phase STR reactor under constant pressure and temperature in the range of 40 to 70°C, pressures of up to 15 bar and an NDMA concentration of 40 to 70 wt%. Products were analyzed using the Gas Chromatographic (GC) technique. Effects of temperature, pressure and NDMA concentration on NDMA conversion and yield of UDMH product in the presence of undesired dimethylamine (DMA) were studied and the optimum conditions for the selective production of UDMH were sought. A kinetic model based on the general form of the Langmuir-Hinshelwood (LH) equation was developed. Further, it was assumed that the hydrogen adsorption is dissociative and non competitive. Comparison with experimental data showed that the Eley-Rideal (ER) model has very good predictive capabilities relative to LH rate equation and therefore, it was selected for further study. Based on this relation the reaction parameters for UDMH and DMA rate equations were estimated through the non linear regression method and activation energies of UDMH and DMA reactions were determined to be 15.97 and 64.98 KJ/mol, respectively.

The reaction kinetics and chemical equilibrium of the reversible catalytic hydrolysis reaction of a methyl acetate to acetic acid and methanol using a strongly acidic ion exchange resin catalyst named Amberlyst 15 were studied. To investigate the different behavior of Amberlyst 15 in the adsorption of reactants and product species, the equilibrium behavior of binary non-reactive liquid mixtures, consisting of one reactant and one product were studied experimentally. The Langmuir model was used to describe the equilibrium condition, quantitatively. Then the employed model was compared with the more complicated thermodynamic models to describe the equilibrium between the catalytic polymer resin and the liquid phase. The results indicated a good agreement. The effects of temperature, catalyst weight, and feed molar ratios on reaction kinetics were investigated. Results revealed that the reaction rate was strongly temperature dependent. The chemical equilibrium compositions were measured in a wide range of temperatures and feed molar ratios. Finally, pseudo homogeneous and LHHW (Langmuir Hinshelwood Hougen Watson) models were developed to calculate the rate of the reaction. Optimization of the model's parameters indicated that the use of activity instead of mole fraction, and also the use of LHHW rather than a pseudo homogeneous model resulted in much smaller residual errors. Also the equilibrium compositions obtained from the equation of rates were in good agreement with the experimental results.

New treatment technologies are currently being investigated for the treatment of contaminated drilling waste mud with oil. Supercritical fluid extraction is a promising technology that could be effectively used to extract this contaminated drilling waste mud. In this work, one step extraction efficiency of supercritical carbon dioxide to drilling waste mud of South Pars gas field has been investigated at a range of temperatures (55 to 79.5 °C), and over a pressure range of 160 to 220 bars. Extraction efficiencies were calculated based on cuttings weight loss. Results show that approximately 28.45 % of cuttings weight loss in one step extraction at a pressure of 200 bars and temperature of 60 °C can be extracted by supercritical carbon dioxide.

Natural and modified clays were applied as adsorbents for the removal of organic contaminants from wastewater. This study presents an investigation on the technical feasibility of using modified minerals that are named organoclay for treatment of dissolved substances, mainly polyphenols in olive mill wastewater. The different parameters such as applied cation dosage were effective on the removal of contaminants by these adsorbents (%CEC), pollutant concentration, Ph and particle size of minerals. In this investigation bentonite particles were modified by stirring the clay with a long chain quaternary ammonium cation. Doses of the applied cation varied from zero to 1.5 times the clay CEC. Results from tests using 40 g/L of natural minerals with CEC=90 miliequivalent/100g, ground clay with less than 0.2 mm size in solution, and pH=3, showed that the removal of polyphenols from olive mill wastewater and orthodiphenol from synthetic wastewater were 22% and 30% respectively. By using 40 g/L organo-bentonite modified with benzyl dimethyl hexadecyl ammonium bromide (BDHDA) and an applied cation dosage equal to 50% CEC for the removal of total polyphenols and orthodiphenol from industrial and synthetic wastewater, with particles less than 0.2 mm, after the mixture was shaken for about 24 h at room temperature and pH=3 using a rotary shaker resulted in 80% and 88% maximum reduction of contaminants from industrial and synthetic wastewater respectively.

Sarabs (spring-fed pools) are an important natural freshwater resource in Iran where they are used for potable, agricultural and recreational purposes. A survey of 17 Sarabs was undertaken in the Province of Kermanshah to obtain data on their water quality and biology which would help inform future management of these multifunctional resources. These Sarabs differed greatly in size (50-30000 m2 surface area) and were situated at altitudes of between 622 and 1697 m above sea level. The average dissolved oxygen content and pH of the water was between 4.5 and 10mg O2/l, and 6.95 and 7.6 respectively. The Sarabs differed particularly in their dissolved solids content from 100mS/cm (detectable limit) to 600 mS/cm. Four Sarabs appeared to be polluted by biodegradable organic matter. An Ekman grab was used in June 2003 to sample the benthic macroinvertebrate faunas. Average population densities, based on the numbers of animals retained by a 600μm mesh sieve, were between 2068 and 21531/m2. Fifty-eight taxa (mainly genera) were identified. Of these, 65% were molluscs, oligochaetes and chironomids. There was relatively little similarity amongst the faunas of the individual Sarabs, but seven taxa occurred in more than half those sampled: Gammarus pulex, Tanytarsus, Eukiefferiella, Tubifex, Erpobdella, Viviparus and Dugesia. The observed distribution of the macroinvertebrates recorded in this survey was largely unexplained by the water quality variables (COD, BOD5, DO, electrical conductivity, pH) measured. Taxon richness for the individual Sarabs differed from 5 to 21. Larger Sarabs tended to support more taxa than the smaller Sarabs.