Modeling of liquid hydrocarbon products from syngas

International Journal of Coal Science & Technology - The modeling of hydrocarbon selectivity and CO conversion of the Fischer–Tropsch synthesis over Fe–Ni/Al2O3 catalyst by using...     

Reducing of heat loss of rubber compound using natural zeolite filler: effect of partially substitution of fillers on compound properties

The main objective of this work was reducing the heat loss of styrene butadiene rubber by partial substitution of carbon black with natural zeolite as a filler. Reducing the usage of carbon black in the rubber industry is a good strategy to decrease fossil fuel usage and global warming. There are different mineral fillers like silica and clay to be used instead of carbon black. Effect of application of natural zeolite on reducing the heat loss of rubber compound based on SBR was investigated by melt mixing of natural zeolite in rubber matrix in an internal mixer. Natural zeolite was selected as 5, 10, 15, and 20 phr. Carbon black was partially substituted with zeolite and the effect of natural zeolite content and structure on different aspects of the compound including heat buildup, hardness, elongation, and modulus were evaluated. It was shown that although cross-link density and mechanical properties of the compounds decreased a little, but a significant improvement was observed in the fatigue resistance of the compounds beside a favorable decrease in the heat buildup and abrasion loss with an increase in the natural zeolite loading. The rate of improvement in properties was slowed down at zeolite contents higher than 5 phr.     

Bioleaching of copper from smelter dust in a series of airlift bioreactors

Bioleaching of copper from the flue dust of the Sarcheshmeh copper smelter has been investigated. A series of continuous tests were carried out in two-stages of airlift bioreactors inoculated with the acidophilic, iron and sulfur oxidizing bacteria, initially derived from acid mine drainage. The effects of different parameters such as pulp density, retention time and temperature on the mesophile bioleach performance of the copper sulfide rich dust were evaluated after pre-leaching with dilute acid. Pulp densities of 2% and 4% gave the same oxidation–reduction potential in both reactors. However, increasing the average pulp density to 7% generated an unstable oxidation–reduction potential in the first bioreactor at 34 °C. Overall copper extractions calculated for 2%, 4% and 7% pulp densities were 90%, 89% and 86% with mean retention times of 2.7, 4 and 5 days, respectively. The process is net acid consuming and has the potential for further development and feasibility studies.     

A rapid and efficient method for the radiosynthesis and purification of [125I]SCH23982

The radiosynthesis of (1R)-(+)-1-phenyl-3-methyl-7-[125I]iodo-8-hydroxy- 2,3,4,5-tetrahydro-1H-3-benzazepine (commonly referred to as SCH23982) and its use as a high affinity D1 dopamine antagonist ligand have been reported previously. We now provide a simple and inexpensive protocol for the rapid and efficient synthesis of this radioligand based on the Cloramine-T-catalyzed reaction between the commercially available precursor (R)-(+)-1-phenyl-3-methyl- 8-hydroxy-2,3,4,5-tetrahydro-1H-3-benzazepine and carrier-free sodium [125I]iodide. [125I]SCH23982 is separated rapidly (within 20 min) from the precursor and reaction byproducts (e.g., chlorinated precursor, SCH23390) by reverse-phase HPLC on a C-8 column. The major iodinated product has been identified as SCH23982 based on co-chromatography with authentic SCH23982, UV spectral characteristics, and biological activity. The chromatographic effluent containing the active product is adsorbed on a C-18 Sep-Pak cartridge to remove mobile-phase constituents and permit it to be eluted and diluted to the desired concentration; this technique is used also for periodic repurification. Our synthesis protocol results in final purified product that incorporates ca. 50% of the initial 125I (tested using starting quantities of 1-10 mCi Na125I); the final product has a specific activity of ca. 2500 +/- 350 Ci/mmol. Data from in vitro receptor autoradiographic and homogenate studies with this radioligand are consistent with previously reported values in terms of expected receptor distribution, affinity, and density (KD of 1.0 nM, Bmax of 1400 fmol/mg protein in rat striatal membranes).     

Out-of-plane free vibration of functionally graded circular curved beams in thermal environment

A first known formulation for the out-of-plane free vibration analysis of functionally graded (FG) circular curved beams in thermal environment is presented. The formulation is based on the first order shear deformation theory (FSDT), which includes the effects of shear deformation and rotary inertia due to both torsional and flexural vibrations. The material properties are assumed to be temperature dependent and graded in the direction normal to the plane of the beam curvature. The equations of motion and the related boundary conditions, which include the effects of initial thermal stresses, are derived using the Hamilton’s principle. Differential quadrature method (DQM), as an efficient and accurate numerical method, is adopted to solve the thermoelastic equilibrium equations and the equations of motion. The formulations are validated by comparing the results, in the limit cases, with the available solutions in the literature for isotropic circular curved beams. In addition, for FG circular curved beams with soft simply supported edges, the results are compared with the obtained exact solutions. Then, the effects of temperature rise, boundary conditions, material and geometrical parameters on the natural frequencies are investigated.     

Determination of selectivity equations heavy and light product of petroleum on iron based catalysts in Fischer-Tropsch synthesis

The optimal control of selectivity is an important method to trigger catalyst activity in the Fischer-Tropsch synthesis to produce favorable products. The determination of a model that will show the extent of product dependence on various parameters is of great importance in the Fischer-Tropsch synthesis. Efforts to increase a product in industry can be economical. In this research, a comprehensive method was evaluated to create a selectivity model of catalyst Fe/Cu/K/SiO₂ of hydrocarbon products under conditions of temperature, pressure, and space velocity in a fixed-bed reactor. The response surface methodology was used in order to optimize process conditions and the relation of continuous functions between variables, so that the obtained model showed the selectivity of methane, light olefin hydrocarbons, heavy hydrocarbons products by factors such as temperature, pressure, and space velocity. A comparison of the models showed space velocity, among all the other factors, had a considerable effect on the increase selectivity of light hydrocarbons. On the other hand, the selectivity of methane indicates that temperature decrease parameter has the minimum effect on production. Whereas, the temperature rise cause reduces heavy hydrocarbons. The goal is to maximizing light hydrocarbon and minimizing methane and heavy hydrocarbon products.

• Highlights

• ? Comprehensive equations to achieve selectivity model of hydrocarbon products.

• ? The response surface methodology was used in order to optimize process conditions.

• ? The optimum products condition was obtained by using the obtained equations.

     

Kinetics studies of nano-structured cobalt–manganese oxide catalysts in Fischer–Tropsch synthesis

The nano-structured cobalt/manganese oxide catalyst was prepared by thermal decomposition of [Co(NH₃)₄CO₃]MnO₄ precursor, and was tested for the Fischer–Tropsch reaction (hydrocarbon forming) in a fixed-bed micro-reactor. Experimental conditions were varied as follow: reaction pressure 1–10 bar, H₂/CO feed ratio of 1–2 and space velocity of 3600 h^?1 at the temperature range of 463.15–523.15 K. On the basis of carbide and/or enolic mechanisms and Langmuir–Hinshelwood–Hougen–Watson (LHHW) type rate equations, 30 kinetic expressions for CO consumption were tested and interaction between adsorption HCO and dissociated adsorption hydrogen as the controlling step gave the most plausible kinetic model. The kinetic parameters were estimated with non-linear regression method and the activation energy was 80.63 kJ/mol for optimal kinetic model. Kinetic results indicated that in Fischer–Tropsch synthesis (FTS) rate expression, the rate constant (k) has been increased by decreasing the catalyst particle size. The catalyst characterization was carried out using different methods including powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and Brunauer–Emmett–Teller (BET) surface area measurements.     

Para-xylene adsorption separation process using nano-zeolite Ba-X

The liquid phase adsorption process was studied on nano-zeolite Ba-X for separating para-xylene from a feed mixture containing all C₈ aromatics. Nano-zeolite Ba-X with different ratios of SiO₂/Al₂O₃ was synthesized through hydrothermal process and ion-exchanged with barium. The product was characterized by X-ray diffraction, scanning electron microscopy (SEM), nitrogen adsorption and in situ Fourier transform infrared (FTIR) spectroscopy. The adsorption process was carried out in a breakthrough system at temperature range of 120–160 °C under 4–7 atm pressure. The influence of nano-zeolite water content on the separation process was studied. The optimization of adsorption process was also investigated by changing the operation conditions. The adsorption isotherm for all C₈ aromatic isomers and also desorbents indicated the typical Langmuir type. The selectivity factor of adsorbent for para-xylene and the adsorption capacity at saturation of the different adsorbate samples with each component from C₈ aromatic mixture were determined. It was observed that the selectivity of para-xylene increased by barium ion-exchange of cationic sites in nano-zeolite X and the adsorbent selectivity for para-xylene relative to each of meta-xylene, ortho-xylene and ethyl-benzene under the optimum conditions was found to be 7.191, 2.819 and 3.745, in the order given. It was also studied the influence of desorbent type on its selectivity for para-xylene compared to each isomer from the C₈ aromatic mixture.     

Parametric investigation of γ-alumina granule preparation via the oil-drop route

Taguchi M₃₂ experimental design was implemented to investigate the effect of operating variables on the structural and textural properties γ-alumina granules produced via the oil-drop route. Aluminum powder and hexamethylenetetramine (HMTA) were used as precursor and gelling agent, respectively. Nitric acid (HNO₃) was tested to dissolve aluminum powder as a novel digestive media. Response surface methodology (RSM) was employed to analyze the results of experimental design. The synthesized samples were characterized, by Thermo-gravimetric analysis (TGA/DTA), X-ray diffraction (XRD), nitrogen physisorption, energy dispersive X-ray (EDX), scanning electron microscopy (SEM), and transmitting electron microscopy (TEM). The output of RSM which is a multivariate linear regression model was examined to find out the effect of each factor on the response, namely the total surface area of γ-alumina granules to reach the optimum conditions. The optimized samples possess superior characteristics, e.g. highest surface area, magnificent sphericity, mesoporous structure, monotonous crystalline network, and broad pore size distribution. Based on the results, the surface area of γ-alumina granules relied too much on the temperature of aging solution, aging time and interactions between the factors. The role of heat treatment on the texture properties and morphology evolution of the samples were also precisely discussed.