Iranian Journal of Chemistry and Chemical Engineering
Year:2010 | Volume:29 | Issue:3|Papers Count:16

The effects of confinement in carbon nanotubes on Fischer-Tropsch (FT) activity, selectivity and lifetime of Carbon NanoTubes (CNTs) supported iron catalysts are reported. A method was developed to control the position of the catalytic sites on either inner or outer surface of carbon nanotubes. TEM analyses revealed that more than 80% of iron oxide particles can be controlled to be positioned at inner or outer surface of the nanotubes. Deposition of iron oxide inside the nanotube pores decreased the average size of the iron oxide particles from 14 to 7 nm and shifted the reduction peak temperature of iron oxide species to lower temperatures (from 389 to 371o C, 428 to 413o C and 580 to 530o C) and improved the reducibility of the catalyst by 25%. Catalytic performances of the catalysts in terms of FT experiment were tested in a fixed-bed micro reactor; the catalyst with catalytic sites inside the pores showed 23% higher initial activity than the catalyst with catalytic sites outside the pores. Also, the catalyst with catalytic sites inside the pores exhibited higher selectivity to heavier hydrocarbons (40.5% vs.32.9% C5+selectivity). In addition, deposition of catalytic sites on interior surface of the nanotubes resulted in a more stable catalyst, while its counterpart experienced 46.4% deactivation within a period of 720 h due to catalytic sites sintering.It is concluded that encapsulation of the catalytic nanoparticles inside the nanotubes prevents the catalytic site agglomeration.

TiCl4, ammonia, inorganic salts as raw material, nanometer composite-crystal TiO2 powders were synthesized by two-step chemical method. Precursors were crystallized with different phase and stable composite-crystal TiO2 with anatase and rutile phase was prepared at low temperature. Quantitative control of crystal phase was realized. Remarkable factors including reaction pH value, reaction time, which affected the phase content, microstructure, morphology were discussed. Applied experiments of photo-degradation organic dyes illuminated by sunshine showed higher photocatalytic activity of composite-crystal than that of pure anatase, pure rutile and mechanical mixture of both, nanometer composite-crystal TiO2 as photocatalyst.

The photocatalytic decolorization of aqueous solutions Brown NG, a commercial textile dye, was studied using titana Degussa P-25 as a catalyst for the first time. The experiments were carried out in a batch reactor with the use of artificial light sources (UV-C). The effects of various process variables on decolorization performance of the process have been investigated. The photodegradation of Brown NG was enhanced by the addition of proper amounts of hydrogen peroxide, but it was inhibited by ethanol. Inhibiting effect of ethanol showed that hydroxyl radicals play a significant role in the photodegradation of the dye. In addition, the decolorization efficiency increased with decrease in pH, which implies that the pH is a very important parameter in dye adsorption. The efficiency is inversely related to the dye concentration. Results of TOC analysis show that the organic compounds were degraded, too.

Effect of scale on the hydrodynamics of gas-solid fluidized beds was investigated in two fluidized beds of 152 mm and 78 mm in diameter. Air at room temperature was used as the fluidizing gas in the bed of sand particles. The Radioactive Particle Tracking (RPT) technique was employed to obtain the instantaneous positions of the particles at every 20 ms of the experiments. These data were used to calculate hydrodynamic parameters, such as mean velocity of upward and downward-moving particles, jump frequency, cycle frequency and axial and radial diffusivities, which are representative of solid mixing and diffusion of particles in the bed. These hydrodynamic parameters were compared in both scales in order to determine the scale effect on the hydrodynamics of the gas-solid fluidized bed. In all cases, it was shown that solid mixing and diffusivity of particles increase by increasing column diameter. The results of this study would help to understand solid mixing which might be critical in industrial fluidized bed reactors.

Fine particles Silicoaluminophosphate-34 were synthesized by hydrothermal sol-gel method. The effect of crystallization time, as one of the important synthesis factors on particle size and crystallinity, kinetic and equilibrium adsorption, and selectivity of CO2 / CH4 has been studied in this work. The adsorption isotherms are obtained at moderate gauge pressures (100 - 3000 kPa) and temperatures (278, 288 and 298 K), and the equilibrium adsorption parameters as well as heat of adsorption are determined for the synthesized SAPO-34. The observed adsorption selectivity of CO2 to CH4 was determined to be around eight for that sample with higher degree of crystallinity. The crystallinity, isotherm parameters, adsorption selectivity and heat of adsorption confirm that the synthesized fine particle of SAPO-34 could be a good candidate for separation of CO2 from CH4.

The subject handled in this study is the determination of antioxidant activities of extracts obtained from the Urginea maritima (L. ) Baker plant’s leaves and tubers. Extractions which were obtained using various solvents as methanol, ethanol, acetone and benzine. The antioxidant activity of the extracts was determined using β-karotene-linoleic acid system. Moreover, the free radical scavenging activity values were tested with DPPH. The concentrations of phenolic compounds in all extracts of UM, expressed as microgram of pyrocatechol equivalents (PEs) were determined with Folin-Ciocalteu reagent (FCR). The results demonstrated that the highest antioxidant activity in the U. maritima (L. ) Baker showed in the tubers with ethanol solvent (%72, 67) and the lowest in the benzine extract from the tubers (%31, 12). The free radical scavenging activity of the methanol extract from the tubers of the U. maritima (L. ) Baker plant (%66.89) was found lower than the BHT value (%91.12) but still the highest. However, the amount of total phenolic compounds of acetone extract of U. maritime (L. ) Baker tubers was 6 times more than ethanol extract. This study demonstrated that U. maritime (L. ) Baker species have high rate antioxidant capacity.

In this study, a functional colorant, Berberine, extracted from Berberis vulgaris wood was applied onto wool fiber using the extract of roots of Rumex Hymenosepolus as biomordant. The effect of treatment variables on the color strength of dyed fibers was examined. The fastness properties of dyed wool against washing, light, dry and wet rubbing were evaluated. Dyed samples were tested for antibacterial activity using AATCC test method 100-2004. Tannin present in the roots of Rumex hymenosepolus when used as a biomordant on wool increased the color strength of the dyed goods. Increase in dyeing time, temperature and pH caused deeper shades. Biomordanting, increased light fastness, rub fastness and wash fastness of dyed samples. The dyed wool represented a high level of antibacterial activity. The extract of the Berberis vulgaris can be considered as a natural dye of acceptable fastness properties together with excellent antibacterial activity for woolen textiles.

In this paper, the fuzzy system has been used for fault detection and diagnosis of a yeast fermentation bioreactor based on measurements corrupted by noise. In one case, parameters of membership functions are selected in a conventional manner. In another case, using certainty factors between normal and faulty conditions the optimal values of these parameters have been obtained through the genetic algorithm. These two cases are compared based on their performances in fault diagnosis of a yeast fermentation bioreactor for three different conditions. The simulation results indicate that the fuzzy-genetic system is superior in multiple fault detection for the conditions where the minimum and maximum deviations from normal conditions occur in the process variables.

5 (6) -Carboxy-rhodamine 110 isomers were rapidly synthesized by condensation of 3-aminophenol and trimellitic anhydride using microwave irradiation as heating method. After esterification of the two isomers, separation and hydrolyzation provided target products, 5-carboxy-rhodamine 110 and 6-carboxy-rhodamine 110, in high yields. The results shows microwave irradiation can effectively reduce the reaction time and the demanding of condensed H2 SO4.

Polycaprolactone (PCL) and poly (butylene terephthalate) (PBT) blend was prepared by melt processing. The PCL/PBT blend showed similar morphology with that of pure PCL. The crystallization temperature of PCL was increased by the incorporation of PBT. It was also observed that the peak height in the DSC thermograms decreased and then disappeared by adding 40% or more PBT which might be due to the transestrification between – OH end groups of PCL and ester groups of PBT. The size of PCL spherulites was about 13 μm which decreased highly in the case of blends due to the nucleation effect. The thermal stability of the PCL/PBT blend was higher than pure PCL.

In this study prediction of the steady-state flow of branched polymer melts in pipe geometry with finite volume method is presented. Our analysis in this study revealed that; for normal-stress tqq , the XPP model can predict this tensor unlike the other viscoelastic models such as PTT or Gieskus which can not predict t qq for viscoelastic fluid in two dimensional pipe flows. The fluid is modelled using a modification of the Pom-Pom model known as the single eXtended Pom-Pom (XPP) where viscoelastic fluid is typically a commercial low-density polyethylene. In finite volume method, the operator-integration is used to discretize the governing equations in space or control volume. An iterative solution algorithm that decouples the computation of momentum from that of stress is used to solve the discrete equations. Numerical results are presented, including the profiles of all relevant stresses, the axial velocity, stretch and the viscosity across the gap, demonstrating the performance of the model predictions. The influence of elasticity parameter on flow behaviour is studied, which demonstrates in particular, the dependence of velocity and stresses distribution as a function of Weissenberg number is analyzed. Also, the effect of Weissenberg number on pressure gradient has been considered. Finally, verification of the present model was made by comparing to the Generalized Newtonian Fluid (GNF) model.

In this paper, the turbulent air droplet flow inside a single passage of a curved type vane separator has been studied numerically. The simulation is based on the Eulerian - Lagrangian method. For turbulent air flow calculations, a computer code was developed to solve the Reynolds Averaged Navier Stokes (RANS) equations together with the equations of Reynolds Stress Transport Model (RSTM) on collocated unstructured meshes. Finite volume method was applied for discretization of the gas flow equations. Also, the low Reynolds modification has been applied for RSTM and the results have been compared with those obtained by Standard RSTM. For droplet trajectory calculation, the Eddy Interaction Model (EIM) was applied to take the turbulent dispersion of droplets into account. The performance of the code has been evaluated by comparing the simulations results with experimental data. The results show that by including the wall reflection terms in transport equations of the Reynolds stresses, better predictions can be achieved than those obtained by RSTM without wall reflection terms. The enhanced wall treatments can further improve the results. Finally, the pressure loss and droplet removal efficiency for different plate spacings have been calculated using the developed codes. The numerical results show that for plate spacings in the range of 25 mm to 35 mm, the pressure loss is approximately constant. On the other hand, the increment in plate spacing reduces the droplet removal efficiency. Therefore, in the mentioned range, 25mm spacing gives the best performance for this type of the vane separator.

Production of highly viscous tar sand bitumen using Steam Assisted Gravity Drainage (SAGD) with a pair of horizontal wells has advantages over conventional steam flooding. This paper explores the use of Artificial Neural Networks (ANNs) as an alternative to the traditional SAGD simulation approach. Feed forward, multi-layered neural network meta-models are trained through the Back-Error-Propagation (BEP) learning algorithm to provide a versatile SAGD forecasting and analysis framework. The constructed neural network architectures are capable of estimating the recovery factors of the SAGD production as an enhanced oil recovery method satisfactorily. Rigorous studies regarding the hybrid static-dynamic structure of the proposed network are conducted to avoid the over-fitting phenomena. The feed forward artificial neural network-based simulations are able to capture the underlying relationship between several parameters/operational conditions and rate of bitumen production fairly well, which proves that ANNs are suitable tools for SAGD simulation.

In this work we introduce a practical use of synthesized Schiff base metal complex in sensing application. A new perchlorate-selective electrode based on the complex N, N' -4-nitrophenylmethanebis- ( salicylaldiminato) copper (II) [CuL] as the membrane carrier was developed. The electrode exhibits a good Nernstian slope of -55.0± 1.0 mV/decade and a linear range of 7.0 ×10 -7 - 1.0 ×10-1M for perchlorate. The limit of detection is 3.0 ×10-7 M. It has a fast response time < 15s and can be used for more than three months. The selective coefficients of Perchlorate-selective electrode were determined by the Fixed Interference Method (FIM) and Fixed Primary ion Method (FPM), and could be used in the pH range 4.0-9.0. It was employed as an indicator electrode for direct determination of perchlorate in real samples.

The structure of N, N' -bis (2-hydroxybenzylidene) -2, 2-dimethyl-1, 3-propanediamine, C19H22N2O2, has been studied at low temperature (120K) by means of single-crystal X-ray diffraction. Solving the structure shows an orthorhombic unit cell, with P212121 space group, Z=4, a=6.1046 (4) Å, b=15.8349 (11) Å, c=17.2898 (12) Å and V=1671.3 (2) Å3. There are two relatively strong hydrogen bonds (average O—H···N, 2.59 Å), involving the hydroxyl group and the nearest N atom of the imine groups is an indicative of intra-molecular hydrogen bonding within each salicylideneimine moiety. C-H…p interactions connect the neighboring molecules together, stabilizing the crystal network. No significant p-p interactions are present in the crystal structure.

An experimental study has been conducted on the hydrodynamics of a stage mixer-settler to obtain an appropriate design. In this paper several tests was performed to investigate full factorial design of experiments. Since each test was repeated seven times, the repeatability of the test was confirmed (P=1 bar and T=25°C). Sauter diameter was determined by photographing both the mixer and settler in each test. The Sauter diameter was compared with the Calderbank model; finally, a model was suggested. Holdup quantity was measured by a vacuum pump at the end of each test. Another aim of this paper is the evaluation of separation mechanism under different impeller speeds and volume fractions. The effect of impeller speed in constant ratio of phases flow rate, and hold up are evaluated, and the effect of phase flow rate ratios in constant impeller speed on extraction efficiency, mass transfer coefficient and distribution coefficient were determined.