فهرست مطالب

Chemical Engineering - Volume:9 Issue: 3, Summer 2012

Iranian journal of chemical engineering
Volume:9 Issue: 3, Summer 2012

  • تاریخ انتشار: 1391/07/10
  • تعداد عناوین: 7
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  • S. H. Mahdaviani, M. Parvari, D. Soudbar Page 3
    The quantity of by-products and polymeric compounds produced in the ethylene dimerization reaction is a critical factor from the industrial viewpoint. It may lead to the shutting down of 1-butene reactors. It is, therefore, highly desirable to identify the factors that are responsible for the formation of polymeric materials and how the formation of these heavy compounds can be minimized or prevented. A significant way to overcome this drawback is by judicious choice of the catalyst and reaction conditions. In this regard, a systematic study has been carried out on a titanium-based catalyst using tetrahydropyran (THP) and tetrahydrofuran (THF) as modifiers, and bromoethane as a new efficient accelerator in combination with triethylaluminum (Et3Al) activator. The addition of bromoethane led to dramatic increases in the rate of reaction and yield, and remarkable decreases in the amounts of heavy and polymeric compounds. It is proposed that specific weak coordination of the halide to the dimeric Et3Al may result in breakage of the Et3Al dimer and the release of monomeric Et3Al. The latter is more reactive than Et3Al dimer and leads to the facile generation of an increased number of the active metal sites that are responsible for the dimerization reaction. Finally, the catalytic performance of the novel homogeneous system [titanium tetrabutoxide Ti(OC4H9)4)/THP/Et3Al/bromoethane] has been examined under various operating conditions.
    Keywords: Ethylene dimerization, Heavy Compounds, THP, Promoter, Bromoethane
  • F. Fakheri, J. Moghaddas Page 14
    Knowledge of mixing time is of fundamental importance for investigation of mixing efficiency in agitation systems. The mixing time obtained by using the correlation and formula in large scale mixing systems was incorrect. Again, the number of available correlations in this scale of mixing systems is limited. To predict the mixing time of stirred tanks with dual impellers commonly used in industry, a third-compartment mixing model was used. The time of homogenization of the charge (mixing time) was calculated from the time dependency of the local concentration of tracer measured at various locations. Experimental data on mixing time were obtained with a conductivity technique. In the present study distribution of tracer in the bulk of the liquid was described by compartment model (CM) as well as for stirred vessel with dual Rushton impellers. As for the model, a good agreement between the experimental data and the calculated values was apparent.
    Keywords: Mixing Time, Compartment Model, Rushton Turbine, Tracer, Conductivity
  • A. Ghanadzadeh, H. Ghanadzadeh, M. Alinejad Page 22
    Dielectric constant measurements were made on binary mixtures of ethyl acetate (EA) and butyl acetate (BA) with the two amyl alcohols (iso-amyl alcohol (IAA) and tert-butyl alcohol (TBA)) for various concentrations at T = 298.2 K and in a frequency of 100 kHz. In order to obtain valuable information about heterogeneous interaction (interactions between the unlike molecules), the Kirkwood correlation factor, the Bruggeman dielectric factor and the excess permittivity were calculated.
    Keywords: Dielectric Constant, Kirkwood Correlation Factor, Excess Permittivity
  • M. Abdolrahmani, M. Parvari, M. Habibpoor Page 31
    Lanthanum in the A-site of LaMn0.8Cu0.2O3 perovskite was partially substituted by silver. La1–xAgxMn0.8Cu0.2O3 samples (x=0, 0.1, 0.2, 0.3) were prepared by the two Pechini and sol–gel methods and their catalytic activity was evaluated for CH4 combustion and CO oxidation reactions. FT-IR analysis of different samples before calcination confirmed the formation of different complexes between the elements. Calcined samples were characterized using XRD, TPR, BET, SEM and XRF techniques. XRD results revealed that the Pechini method led to perovskite structures with higher purity and that segregation of Ag in samples prepared by the sol–gel method was higher. SEM images and EDS results for samples before and after catalytic tests showed that the Pechini samples had a lower particle size and better distribution of the elements. The catalytic results indicate that the oxidation activity increased with the amount of Ag in the oxide, but the stability of the structure decreased.
    Keywords: Perovskite, Pechini Method, Sol–Gel Method, Oxidation Catalyst
  • Y. Jafarzadeh, S. Shafiei, A. Ebadi, M. Abdoli Page 48
    The separation of immiscible liquids plays an important role in the oil and petrochemical industries. In the outlet stream of a catalytic reactor of dehydrogenation of ethyl benzene to styrene monomer, water is present because it is used as high pressure steam to provide reaction heat. Therefore, aqueous and immiscible organic phases should be separated in a horizontal separator before fractionation. The objective of this work is to study the separation of ethyl benzene, styrene, and water in a horizontal pilot scale separator. Experiments showed that the performance of the separator is affected by feed flow rate and composition. Furthermore, the thickness of mesh installed in the inlet zone of the separator has an effect on the hydrodynamic behavior of the separator and its performance.
    Keywords: Horizontal Separator, Phase Separation, Immiscible Liquids, Styrene Production
  • D. Saydi Hatamipour Page 55
    Spray dryer was used to produce potato powder from potato juice. Turning potatoes into powder will increase its substance durability, ease of transportation and the storage. The important factors affecting the powder produced by spray dryer include inlet air temperature, volumetric flow rates of feed and air. Experiments were conducted according to Taguchi’s method by considering 3 levels for each one of the mentioned parameters and 2 levels for atomizer’s nozzle diameter. The objective was to obtain the optimized process conditions for producing potato powder with desirable color. By analyzing the experimental results, the optimized conditions for producing potato powder by spray dryer were determined. It was also revealed that by adding 1 percent maltodextrin (dry mass basis) to the feed, the product’s adhesion will decrease significantly and the amount of product will be increased.
    Keywords: Potato Powder, Spray Dryer, Color
  • A. Telmadarreie, S. R. Shadizadeh, B. Alizadeh Page 63
    Marun oil field is located in the southwest of Iran and consists of two oil reservoirs named Asmari and Bangestan. Asmari oil reservoir has been producing sweet oil and gas since 1964, but for the first time a high amount of hydrogen sulfide gas was observed in one well of this reservoir in 1980. Moreover, the Bangestan oil reservoir is located deeper than the Asmari oil reservoir and has been producing sour oil and gas since 1972. This paper represents the conducted study on the determination of hydrogen sulfide oil pollution sources in the Asmari oil reservoir. There are two hypotheses for sources of hydrogen sulfide oil pollution in the Asmari oil reservoir; first, hydrogen sulfide gas migration from Bangestan oil reservoir and second, sour gas injection migration. Data of well souring history, hydrogen sulfide gas concentration of wells, volume of gas injection and RFT analysis were used to investigate these hypotheses. The results showed a similar trend of gas injection volume and hydrogen sulfide gas concentration of wells, which decreased over time. Also, the results demonstrated that the migration of gas injection is a source and cause of spreading of hydrogen sulfide gas in the Asmari oil reservoir.
    Keywords: Marun, Asmari, Hydrogen Sulfide, Reservoir souring, Sour gas injection