Iranian Journal of Chemistry and Chemical Engineering
Volume:24 Issue: 3, May-Jun 2005

Aluminum anodes have been widely used in the cathodic protection of marine structures. However there are conditions in which these anodes become passivated or face some localized or unwanted corrosion, which influences their efficiency. Addition of alloying elements such as Zn and In not only have improved the efficiency of the anodes but also the effect of casting parameters such as ultra melt temperature Tm, mold temperature and grain refiners can adversely influence the capacity of aluminum anodes. In this work the effects of ultra melt temperature and mold temperature have been studied on the potential and current capacity of Al-Zn-In anodes. Electrochemical polarization and NACE standard methods were used to evaluate the anodic behavior, potential and current capacity of the anodes. It is shown that metallic molds having higher temperatures could provide better condition for obtaining homogenous structures with minor inclusions. The optimum condition of anode operation may be provided where mold and pouring temperatures equal to 400 ºC and 710 ºC respectively, in which a fine structure, phase distribution and lack of casting faults are obtained. The microstructures that can provide a homogenous anodic dissolution bring by itself optimum efficiency of the anodes.

An extensive study of Fischer-Tropsch synthesis (FTS) on alumina-supported cobalt catalysts promoted with different amounts of ruthenium and rhenium is reported. Up to 2 wt% of promoters, are added to the catalyst by coimpregnation. The catalysts are characterized by different methods including: BET physisorption, X-ray diffraction, hydrogen chemisorption, and temperature-programmed reduction. The effect of the promoters on the reducibility of the cobalt oxide species, dispersion of the cobalt, and activity and selectivity of FTS is investigated. The Re enhances the reducibility of the CoO to Co0 and small cobalt oxide particles with higher interaction with the support. However, Ruthenium was found to enhance the reducibility of Co3O4 to CoO and that of CoO to Co0 and small cobalt oxide particles with higher interaction with the support. 1wt% Ru and 1.4wt% Re increased the activity of the catalyst by a factor of 2.8 and 2.5 respectively. Both promoters enhance the selectivity of Fischer-Tropsch synthesis towards the higher molecular weight hydrocarbons. However, the effect of Re is less pronounced.

Numerous investigations have been devoted towards understanding the hydrodynamics of gas jets in fluidized beds. However, most of them address the problem from macroscopic point of view, which does not reveal the true behavior in the jet region at the single particle level. The present work aims to understand the jet behavior from a more fundamental level, i.e. the individual particle level. A thin rectangular gas fluidized bed, constructed from acrylic glass, with a vertical jet nozzle located at the centre of the distributor was used in the work. A high speed camera with a speed up to 10,000 frames per second was used to observe the jet behavior. Analysis of large quantity of images allowed determination of solids flux, solids Velocity and solids concentration in the jet region. The model present in this work has shown better agreement with the experimental data in compare with the previous models presented in the literature.

The main aim of this research is to determine optimal leaching conditions; Eh, pH and complexing agent concentrations, for recovery of Copper from hydroxide sludges such as those produced by electroplating shops, metal finishers, treatment of acid mine drainage, and industrial wastewater in general. This has been preceded by a theoretical approach and numerical and computer calculation. Potential-pH diagrams for the copper-water-ammonia, copper-water-cyanide, copper-water-glycine, copper-water-ethylenediamine (En) and copper-water-ethylene-diaminetetraacetic acid (EDTA) systems are derived at different total copper and complexing agent concentrations. The originality of our method is the introduction of a rigorous calculating method; we don’t neglect any equilibrium or species for Eh-pH diagrams and with the free concentration of complexing agent (pL-pH) diagram to show the stable regions of soluble copper species.

A bacterial strain (strain PS) was isolated from the textile effluents carrying Serilene Black BNFS® (C.I. Disp. Blk. Mix) disperse dye. The isolate was able to decolorize the dye without the need for any exogenous carbon source. Full sequencing of its 16S rRNA indicated that Bacillus sp strain PS is related to Bacillus cereus groups. Silica- gel-thin layer chromatography of Serilene black dye showed that its main component is a blue dye. FT- IR analysis of this blue fraction showed that its structure corresponds to azoic dyes. Thus Bacillus sp, strain PS was used to decolorize methyl orange as a model azo dye, which it did after 2 days of incubation under aerobic conditions on a shaker incubator (30°C, 140 rpm). Comparing TLC and GC-MS analyses with the authentic sample main showed that its decomposition product is N, N-dimethyl 1, 4- phenylene diamine. Experiments with N, N-dimethyl 1, 4-phenylene diamine as a co-substrate in mineral medium showed that this component disappeared after 7 day incubation. These observations confirm that the decomposition of Serilene dye occurs in a manner similar to that of methyl orange.

The solvent free route for the synthesis of diaryl sulfoxides from arenes and thionyl chloride in the presence of Lewis acids such as aluminum chloride and ferric chloride on silica gel are described.

The interaction between 4, 7, 13, 16, 21, 24 - hexaoxa-1,10 - diazabicyclo [8.8.8] hexacosane (C222) and 7,7,8,8- teracyanoquinodimethane (TCNQ) has been studied in chloroform at 25°C. The results indicate a two step mechanism. At the first step, two adducts (assign as P1 and P2) are formed through equilibrium reactions. In continue and through nonequilibrium reactions the adducts are converted to a final product (assign as P3). Based on the comparison of the spectra of C222-TCNQ mixture with that of Na-18C6-TCNQ mixture, the C222+TCNQ¯, C222+TCNQ¯ TCNQo and (C222+)2(TCNQ¯)2 are suggested as the P1, P2, and P3, respectively. IR specra of C222 and TCNQ are compared with the spectrum of solid 1:1 TCNQ-C222 complex and the effect of complexation on absorption bands are discussed.

Changes in the physicochemical conditions of process unit, even under control, may lead to what are generically referred to as faults. The cognition of causes is very important, because the system can be diagnosed and fault tolerated. In this article, we discuss and propose an artificial neural network that can detect the incipient and gradual faults either individually or mutually. The main feature of the proposed network is including the fault patterns in the input space. The scheme is examined through a sample unit with five probable occurring faults. The simulation results indicate that the proposed algorithm can detect both single and two simultaneous faults properly

Alkali and alkaline earth metals hydrogen sulfate catalyzed the one-pot three component condensation reaction of aldehydes, 1,3-dicarbonyl compounds and urea or thiourea under solvent-free conditions leading to 3,4-dihydropyrimidin-2(1H)-ones in high yields at 80 °C. Our results showed that Biginelli reaction not only is pH dependent, but the cation of catalyst plays an important role.