سال:1388 | دوره: | شماره: |تعداد مقالات:15

The determination region of solubility of methanol with gasoline of high aromatic content was investigated experimentally at temperature of 288.2 K. A type 1 liquid-liquid phase diagram was obtained for this ternary system. These results were correlated simultaneously by the UNIQUAC model. The values of the interaction parameters between each pair of components in the system were obtained for the UNIQUAC model using the experimental result. The root mean square deviation (RMSD) between the observed and calculated mole percents was 3.57 % for methylcyclohexane + methanol + ethylbenzene. The mutual solubility of methylcyclohexane and ethylbenzene was also investigated by the addition of methanol at 288.2 K.

The distribution behavior of ofloxacin enantiomers was examined in the aqueous and organic solvent of a two-phase system containing chiral selector L-tartarate. The effect of extraction equilibrium time, buffer pH, organic solvents and length of alkyl chain of L-tartarate on the partition coefficients and enantioselectivity of racemic ofloxacin were investigated, respectively. The L-tartarate formed more stable complexes with R-ofloxacin than that with S-ofloxacin. The partition coefficients and enantioselectivity of racemic ofloxacin increased with increasing length of alkyl chain of L-tartarate. Solvents showed a large influence on enantioselectivity and partition coefficients. Optimum buffer pH was about 7 for separation of racemic ofloxacin by extraction.

Microbial cells are producers of natural polymers present in plant cells. Production of pullulan (an extracellular microbial polysaccharide) by Aureobasidium pullularia pullulans (P. pullulans) was studied under fermentation conditions, and kinetic parameters were determined. Pullulan formation obeyed a growth and non-growth associated term. PHB (polyhydroxybutyrates) an intracellular biopolymer production by Rastonia eutropha (Alcaligen eutrophus), R. eutropha was studied under different culture media, including synthetic and natural carbon sources. Molasses as a natural carbon source in the culture media presented high efficiency in cell and biopolymer accumulation.

In this research Na-Y was synthesized by hydrothermal method and used as support for preparation of Sn/Pt/Na-Y catalysts using two different tin precursors, Bu3Sn (Cl) and SnCl2.2H2O, by sequential impregnation, in which the Pt  was deposited first and in the next step Sn was deposited. The catalysts were characterized by H2 chemisorption, transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), X-ray powder diffraction (XRD) and, thermogravimetrical analysis (TG) techniques. Elemental analysis of the catalysts was also carried out by X-ray fluorescence analysis (XRF). Dehydrogenation of isobutane was studied in a reactor under atmospheric pressure at 848 K. The conversion, selectivity and the yield of product and the efficiency of prepared catalysts were calculated. The aim of this work was to investigate effect of different Sn precursor and Pt dispersion on the performance of the prepared catalysts.

Two sensitive spectrophotometric methods are presented for the assay of pantoprazole sodium sesqui hydrate (PNT) in bulk drug and in formulations using N-bromosuccinimide (NBS) and two dyes, methyl orange and indigo carmine, as reagents. The methods involve the addition of a known excess of NBS to PNT  in acid medium, followed by determination of unreacted oxidant by reacting with a fixed amount of either methyl orange and measuring the absorbance at 520 nm (method A) or indigo carmine and measuring the absorbance at 610 nm (method B). In both methods, the amount of NBS reacted corresponds to the amount of PNT and  the measured absorbance is found to increase linearly with the concentration of PNT  which is corroborated by the correlation coefficients of 0.9959 and 0.9985 for method A and method B, respectively. The systems obey Beer’s law for 0.1 - 2.0mg mL-1 and 0.5 - 6.0mg mL-1 for method A and method B, respectively. The limits of detection and quantification are also reported for both methods. Intra-day and inter-day precision, and accuracy of the methods have been evaluated. The methods were successfully applied to the assay of PNT in tablet preparations and the results were statistically compared with those of the reference method by applying Student’s t-test and F-test. No interference was observed from the common tablet excipients. The accuracy of the methods was further ascertained by performing recovery studies via standard-addition method.

The potential of carbon nanotubes (CNT) supported cobalt catalysts for Fischer-Tropsch (FT) reaction is shown. Using the wet impregnation method cobalt on carbon nanotubes catalysts were prepared with cobalt loading varying from 15 to 45 wt. %. The catalysts are characterized by different methods including: BET physisorption, X-ray diffraction, hydrogen chemisorption, and temperature-programmed reduction. The activity and product selectivity of the catalysts were assessed and compared with alumina supported cobalt catalysts using a continuous-stirred tank reactor (CSTR). Using carbon nanotubes as cobalt catalyst support was found to decrease the reduction temperature of Co3O4 to CoO from 440 to 347oC and that of CoO to Coo from 640 to 574oC. The strong metal-support interactions are reduced to a large extent and the reducibility of the catalysts improved by 67.7 %. CNT aided in well dispersion of metal clusters and average cobalt clusters size of the reduced cobalts is decreased from 5.3 to 4.9 nm. Results are presented showing that the hydrocarbon yield obtained by CNT supported cobalt catalyst is 74.6 % more than that obtained from cobalt on alumina supports. The maximum concentration of active surface Coo sites and FTS activity for CNT supported catalysts are achieved 40 wt.% cobalt loading. CNT caused a slight decrease in the FTS product distribution to lower molecular weight hydrocarbons.

In the present study, photocatalytic removal of p-nitrophenol has been carried out in the presence of ZnO by using a batch reactor with a UV-C lamp (15 W). The effects of applied ZnO concentration and UV light intensity have been studied. The increase of initial pollutant concentration decreases the removal rate, and the results indicate that the apparent reaction rate constant in the UV/ZnO process is a function of ZnO concentration. The kinetics of removal follows pseudo- first order. The influence of pollutant assisting chemicals such as NaCl, NaHCO3 and Na2CO3 on photocatalytic removal has been investigated. Addition of these chemicals reduces the removal rate. HPLC results showed that some intermediates appeared in the reaction course and were removed with increasing irradiation time. Therefore the results reveal that the mineralization of (p-NP) at optimum condition occurs and COD reduction of 80.0 % takes place after 150 min of irradiation.

Walnut (Juglans regia L.) were evaluated for some physical properties and chemical composition. Ripe fruits were determined for moisture (2.71%), crude protein (14.6%) crude fibre (1.8%) ash (1.57%), crude energy (576 Cal) ether soluble extract (24.71%), nut (10.5g) and kernel (5.09g) veights. Relative density, refractive index, free fatty acids, peroxide value, saponification number, unsaponifiable matter were established in the walnut oil. The main fatty acids identified by gas chromatography were palmtic (6,4%) oleic (13.4%), linoleic (55,3%) and linolenic (8,7%) acids. The mineral contents of walnuts were established by using Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES). Contents of A1, Ca, Fe, K, Mg, Mn, Na, P, Se and Zn were also determined in the fruits. The work attempts to contribute to knowledge of the nutritional properties of walnut kernels. The fruits were found to be rich in protein, oil, fibre, unsaturated fatty acids and minerals. These results may be useful for the evaluation of dietary information.

The combustion process of TiO2- 2Mg- C and 3TiO2-4Al-3C systems in a tubular furnace was investigated. TiC has been synthesized by the magnesiothermic reaction from a mixture of compacted powders of TiO2, Mg and charcoal as starting materials in the presence and absence of NaCl. The effects of temperature, pressure, and the stoichiometry ratio in the reaction yield have been studied. The results show that the synthesis of titanium carbide in the presence of sodium chloride has a better yield than other methods. Titanium carbide was also synthesized by aluminothermy reaction from a mixture of compacted powders of aluminum, titanium dioxide and charcoal. The reaction processes are modified to achieve a high yield of TiC. The final products were characterized by XRD and SEM.

Acid extract of Solanum tuberosum was tested as corrosion inhibitor for mild steel in 1 M HCl and H2SO4 media using different techniques: Weight loss (in different temperatures viz., 303, 313 and 323 K), Potentiodynamic polarization, Electrochemical Impedance Spectroscopy (EIS) and SEM techniques. The studies reveal that the plant extract act as good inhibitors in both the acid media and better in H2SO4 medium. Tafel polarization method indicated that the plant extract behaves as mixed mode inhibitor. Double layer capacitance and charge transfer resistance values derived from Nyquist plots obtained from AC impedance studies give supporting evidence for the anticorrosive effects of these plants. The inhibitive effect may be attributed to the adsorption of the inhibitor on the surface of MS following Temkin adsorption isotherm. Increase of inhibition efficiency with increase of temperature along with Ea values serve as proof for chemisorption. SEM studies provide the confirmatory evidence for the protection of MS by the green inhibitor. The study reveals the potential of the plant extract for combating corrosion which may be due to the adsorption of alkaloids and other phytoconstituents.

An experimental study has been made of the hydrodynamics of a stage mixer-settler to obtain appropriate design information. In this paper several tests were done according to full factorial design of experiments with high reliability, since each test recurs seven times and the results of  them are very close to each other(P=1 bar and T=25oC). Sauter diameter in each test is determined with photographing of both mixer and settler and holdup quantity is measured by vacuum pump at the end of each test. In each test, dispersion height and dispersion length are determined by photographing of settler. Sauter diameter has been compared with Calderbank model and finally, a model has been suggested.

Frothers have a profound effect on bubble size and also flotation efficiency. In present study the effect of type and dosage of frothers on the flotation response of coarse particles of quartz was investigated. Therefore, flotation response of coarse particles using frothers such as MIBC, pine oil, poly propylene glycol with concentration of 0, 25, 50 and 75g/t, was obtained respectively. For all used frothers, maximum recovery was obtained around frother dosage of 25 g/t and with increasing frother dosage, flotation recovery decreased. With increasing frother dosage, bubble diameter, d32, decreased and when Poly Propylene Glycol, MIBC and Pine Oil were used as frother, bubble diameter increased. Maximum bubble diameter was obtained around Pine Oil and frother dosage of 25 g/t and minimum bubble diameter was obtained around Poly Propylene Glycol and frother dosage of 75 g/t. As the particle size increased, the probability of collision increased and with using Poly Propylene Glycol, MIBC and Pine Oil, probability of collision increased, respectively. Maximum collision probability was obtained around 65.46 % with Poly Propylene Glycol dosage of 75 g/t and particle size of 545 microns and minimum collision probability was obtained around 1.43 % with Pine Oil dosage of 25 g/t and particle size of 256 microns.

Polygalacturonase production under different shear stress environments by Aspergillus sp. was studied. It was found that the rate of enzyme production in the stirred tank fermentor decreased with increasing the stirrer speed in the range 300-750 rpm. On the other hand, in a split cylinder air-lift fermentor, the rate of polygalacturonase production slightly increased with increasing in air rate from 1.5 to 2 v.v.m (volume air/culture volume/minute). The maximum enzyme titres at the end of the cultivation period in the airlift fermentor were 35 unit/ml and at least twice of that obtained in agitated fermentors. Measurement of main hyphal length in agitated and air-lift fermentors suggested break up of the mycelia in the higher shear environment of stirred fermentor especially at the higher agitation rates. The similarity in the trend of the enzyme production and main hyphal length suggested a possible relationship between the morphology and productivity of the Aspergillus sp. used in the present study.

In present investigation the biological leaching of aluminum by isolated fungi from red mud, the main waste product of the alkaline extraction of Al from bauxite was studied. Biological leaching experiments were carried out using indigenous, date and orange specimen fungi, Aspergillus Niger, Penicillium simplicissimum notatum. Savored Dextrose chloramphenicol Agar (SDA) was used as medium for the selected fungi. All microorganisms were tested for acid-production and leaching capabilities of aluminum from red mud. Leaching tests were performed in 250mL Erlenmeyer flasks at 28°C and at 150 rpm under aseptic conditions. Preheating of red mud and its impact on leaching process was investigated. Indigenous specimen fungi were the most efficient of the fungal cultures; 2082 mg of Al2O3/l was solubilized at 15 % pulp density of red mud. The metal content of leeching solution was determined by using wet chemical and atomic absorption spectrophotometer.