Kinetics study of CO hydrogenation on a precipitated iron catalyst

The kinetics of the gas–solid Fischer–Tropsch synthesis over a precipitated Fe/Cu/La/SiO₂ catalyst was studied in a well mixed, continuous spinning basket reactor. A wide range of synthesis gas conversions have been obtained by varying experimental conditions. Several Langmuir–Hinshelwood–Hougen–Watson type rate equations were derived based on detailed sets of possible reaction mechanisms originating from the carbide, enolic and combined enol/carbide mechanisms. Three models for the Fischer–Tropsch reaction rate were fitted to the experimental reaction rates. Kinetic parameters of models are determined using the genetic algorithm approach (GA), followed by the Levenberg–Marquardt (LM) method to make refined optimization, and are validated by means of statistical analysis. Simulations using the optimal kinetic models derived showed good agreement with experimental data.     

RSM optimized self-cleaning nano-finishing on polyester/wool fabric pretreated with oxygen plasma

In this study, polyester/wool blended fabric was coated with titanium dioxide nanoparticles. To enhance the adsorption and loading of nanoparticles on wool and polyester fibers, the samples were pretreated by low-temperature oxygen plasma. Citric acid was used to fix the TiO₂ nanoparticles on the fibers. The self-cleaning property of the finished samples was tested under UV-A light. The effect of plasma treatment time besides the concentrations of TiO₂ nanoparticles and citric acid on the self-cleaning properties of the samples was analyzed and optimized using response surface methodology. The surface chemistry and morphology of the samples were studied using Attenuated total reflectance-fourier transform infrared spectorscopy (ATR-FTIR) and field emission scanning electron microscope, respectively. The results showed that plasma treatment has a great effect on the loading of the nanoparticles on the surface of the fibers and enhancing the self-cleaning properties of the finished samples. The plasma-treated samples showed better water absorbency, enhanced tensile strength and approximately the same handle compared to raw samples after coating with TiO₂ nanoparticles.     

A statistical approach of heat transfer coefficient analysis in the slurry bubble column

Heat transfer plays an important role in slurry bubble column reactors (SBCRs). Design of heat transfer equipments for SBCRs is a limiting step in sizing and scale up of them. In order to study the convection heat transfer coefficient (CHTC) in industrial SBCRs, a proper column was designed and manufactured in pilot scale with a special convection heat transfer coefficient measurement probe (CHTC MP). In this study, influence of effective parameters such as solid fraction, superficial gas velocity, radial and vertical position of the column was investigated on CHTC. The design of experiments was performed using a full factorial method including 3¹ × 2² × 9¹ = 108 experiments, to determine the main effects, binary and ternary interactions of variables. Study of the curvature functionality of CHTC versus gas velocity and effect of flow regime transition from homogeneous to heterogeneous flow was the other goal of this work. A statistical model including the main variables and their significant binary and ternary interactions was explained for CHTC with a good fitness with experimental data. Interactions of four effective parameters including solid fraction, superficial gas velocity, radial and vertical position of the column was studied for the first time in the SBCRs. A dimensionless correlation for local Stanton number was developed as a function of Pr, Re, Fr, non-dimensional radial position and non-dimensional distance from the sparger. Considering local positions in the correlation is a novel work and this correlation has good agreement with experimental data.     

Synthesis route and three different core-shell impacts on magnetic characterization of gadolinium oxide-based nanoparticles as new contrast agents for molecular magnetic resonance imaging

Despite its good resolution, magnetic resonance imaging intrinsically has low sensitivity. Recently, contrast agent nanoparticles have been used as sensitivity and contrast enhancer. The aim of this study was to investigate a new controlled synthesis method for gadolinium oxide-based nanoparticle preparation. For this purpose, diethyleneglycol coating of gadolinium oxide (Gd₂O₃-DEG) was performed using new supervised polyol route, and small particulate gadolinium oxide (SPGO) PEGylation was obtained with methoxy-polyethylene-glycol-silane (550 and 2,000 Da) coatings as SPGO-mPEG-silane550 and 2,000, respectively. Physicochemical characterization and magnetic properties of these three contrast agents in comparison with conventional Gd-DTPA were verified by dynamic light scattering transmission electron microscopy, Fourier transform infrared spectroscopy, inductively coupled plasma, X-ray diffraction, vibrating sample magnetometer, and the signal intensity and relaxivity measurements were performed using 1.5-T MRI scanner.As a result, the nanoparticle sizes of Gd₂O₃-DEG, SPGO-mPEG-silane550, and SPGO-mPEG-silane2000 could be reached to 5.9, 51.3, 194.2 nm, respectively. The image signal intensity and longitudinal (r₁) and transverse relaxivity (r₂) measurements in different concentrations (0.3 to approximately 2.5 mM), revealed the r₂/r₁ ratios of 1.13, 0.89, 33.34, and 33.72 for Gd-DTPA, Gd₂O₃-DEG, SPGO-mPEG-silane550, and SPGO-mPEG-silane2000, respectively.The achievement of new synthesis route of Gd₂O₃-DEG resulted in lower r₂/r₁ ratio for Gd₂O₃-DEG than Gd-DTPA and other previous synthesized methods by this and other groups. The smaller r₂/r₁ ratios of two PEGylated-SPGO contrast agents in our study in comparison with r₂/r₁ ratio of previous PEGylation (r₂/r₁ = 81.9 for mPEG-silane 6,000 MW) showed that these new three introduced contrast agents could potentially be proper contrast enhancers for cellular and molecular MR imaging.     

Comparison of essential oil compositions of Salvia mirzayanii obtained by supercritical carbon dioxide extraction and hydrodistillation methods

Essential oil of Salvia mirzayanii cultivated in Iran was obtained by hydrodistillation and supercritical (carbon dioxide) extraction methods. The oil was analysed by capillary gas chromatography using flame ionization and mass spectrometric detections. The compounds were identified according to their retention indices and mass spectra (EI, 70 eV). The effects of different parameters such as pressure, temperature, modifier volume and extraction times (dynamic and static) on the supercritical fluid extraction (SFE) of S. mirzayanii oil were investigated. The results showed that, under a pressure of 35.5 MPa, temperature of 35 °C, 6% methanol, dynamic extraction time of 50 min and static extraction time of 30 min, extraction was more selective for the linalyl acetate. Thirty four compounds were identified in the hydrodistilled oil. The major components of S. mirzayanii were linalyl acetate (7.6%), 1,8-cineole (8.0%), linalool (9.0%) and 8-acetoxy linalool (11.0%). However, by using supercritical carbon dioxide in optimum conditions, only three components contain more than 63% of the oil. The yield of the obtained oil based on hydrodistillation was 2.20% (v/w). Extraction yield based on the SFE varied in the range of 1.50–9.67% (w/w) under different conditions. The results revealed that, in Iranian S. mirzayanii oil, linalyl acetate is a major component.     

Oxidation of benzyl alcohols to the corresponding carbonyl compounds catalyzed by copper (II) meso-tetra phenyl porphyrin as cytochrome P-450 model reaction

The oxidation of benzyl alcohols has been studied in the presence of isobutyraldehyde as co-catalyst, molecular oxygen as oxidant and copper (II) meso-tetra phenyl porphyrin (CuTPP) as catalyst. The CuTPP catalyst exhibits good activity and high selectivity under mild conditions. The effects of temperature and solvents have also been investigated in this catalyst system.     

Structure Stability and Oxygen Permeability of Perovskite-type Oxides of Ba_(0.5)Sr_(0.5)Co_(0.8)Fe_(0.1)R_(0.1)O_ (3-δ)(R=Al,Mn,Fe,Ce,Cr,Ni,Co)

Perovskite-type Ba 0.5 Sr 0.5 Co 0.8 Fe 0.1 R 0.1 O 3 δ (R=Al,Mn,Fe,Ce,Cr,Ni,Co) oxide membranes were exploited and synthesized.Oxygen behavior,order-disorder transition and phase stability of these composite oxides were investigated by combined analysis of X-ray diffraction (XRD),temperature programmed desorption (TPD),thermogravimetric-differential thermal analysis (TG-DTA).Oxygen permeation through these membranes was studied by the gas chromatography (GC) method using a high-temperature permeation cell in a wide temperature range from 700 to 950 C.High permeation fluxes were observed for these materials.The high permeation flux was about 3.19 ml·min 1 ·cm 2 under air/He gradients at 950 C,which was achieved for Ba 0.5 Sr 0.5 Co 0.8 Fe 0.1 Ni 0.1 O 3 δ (BSCFNiO) membrane.The results of analysis showed no phase transition for BSCFNiO oxide with increasing temperature and XRD pattern of this material after O 2-TPD indicated to sustain a pure perovskite structure after oxygen permeation process.     

Incorporation of Iron Nanoparticles into Silicon Carbide Nanoparticles as Novel Antimicrobial Bimetallic Nanoparticles

Silicon - Zero valent iron nanoparticles have an attracting and ever growing interest in various research fields due to the fascinating potential. In the present work, antimicrobial activity of...