Sharif Digital Repository

The mass transfer coefficients of single drops in liquid-liquid extraction systems were studied using a single drop apparatus both with and without packing. The chemical system of n-butanol-succinic acid-water and the Structured Packing (SMV.350Y) were used in the liquid-liquid extraction. Based on the experimental results obtained for both mass transfer directions, in most cases, the structured packing had considerably enhanced the mass transfer coefficient by increasing the contact area between two phases and also increasing the contact time, especially in the contaminated systems. This is an abstract of a paper presented at the 18th International Congress of Chemical and Process... 

Adsorption is one of the most sophisticated separation processes widely used in oil, gas and petrochemical facilities, and there is no doubt in the environmental and technological significant of this technology. But, the key to design an efficient adsorption service is to accurately select a suitable adsorbent that strongly dependent to the feed composition, product specification, and operating conditions. During the last 30 years, different classes of solid adsorbent have been manufactured; but, they should be meticulously chosen accordingly. In this paper, the specification and main charac-teristics of adsorbents generally used in oil, gas and petrochemical processes including activated... 

Titanium type lithium ion-sieve nanotubes synthesized by the hydrothermal method were extensively explored over recent years due to its promising properties. However, on account of nanotubes′ tangled structure impeding the lithium adsorption in the interior nanotube walls, unalterable dimensions of the synthesized nanotubes, and a long period of annealing, the anodizing technique was proposed. It is shown that lithium uptake and adsorption capacity is improved because of easier mass transfer during the ion exchange process. This work focuses on a novel anodizing method for nanotube ion-sieve synthesis. The optimum anodizing condition was discovered by altering anodizing voltage, time, and... 

In this study, graphene oxide fibers are introduced as new graphene oxide (GO) membranes with the capability of ion selectivity. Graphene oxide fibers, like other macro structured membranes, are always associated with cavities and defects. To solve this problem, a 50% combination of graphene oxide suspension including small sheets with an average size of ~ 0.5 µm2 and large sheets with an area of more than 10 µm2 was used. According to the morphological results of scanning electron microscopy, as well as the amount of ionic transport through the fiber, reduction of cavities and its defects were confirmed. Moreover, it was found that ionic current through fibers consist of large and small GO... 

Glucose was acylated with palmitic acid using two kinds of lipases. The reactions were performed in the presence of an organic solvent. Solvent effect and molecular sieve effect and also the effect of enzyme amount and influence of molar ratio of substrates on glucose palmitate production with lipase from Rhizomucor miehei (Palatase® M) were studied. Application of molecular sieves together with open system increased palmitic acid conversion in the reaction mixture. Glucose palmitate was obtained in 41.18% conversion in hexane at 40°C with Palatase® M. Glucose palmitate was also synthesized with lipase from Candida antarctica (Novozyme 435). Esterification of palmitic acid with glucose... 

Adsorption equilibrium data for CO, CO2, CH4 and C2H4 on 5A molecular sieve were obtained at (303, 373 and 573) K and at partial pressures up to 1000 kPa. An accurate and simple volumetric apparatus was used to measure gas sorption. The Langmuir and Sips equations were used to correlate the experimental data. In spite of the relative simplicity of both isotherms, the correlation between experimental and theoretical data is good. The Sips equation with three parameters has expected a better fit than the Langmuir isotherm with two parameters. Based upon the Langmuir equation the enthalpy of adsorption and pre-exponential factor in the van't Hoff correlation were derived for all four gases. ©... 

In this paper, we present an extension of dissipative particle dynamics method in order to study the mixed electroosmotic/pressure-driven micro- or nano-flows. This method is based on the Poisson-Boltzmann equation and has a great potential to resolve the electric double layer (EDL). Hence, apart from studying the bulk flow, it also provides a strong capability in order to resolve the complex phenomena occur inside the EDL. We utilize the proposed method to study the pure electroosmotic and also the mixed electroosmotic/pressure-driven flow through the straight micro-/nano-channels. The obtained results are in good agreement with the available analytical solutions. Furthermore, we study the... 

The 3A zeolites are excellent adsorbents for industrial-scale gas dehydration because of the low energy required for regeneration and ease of operation. A computational study of the dehydration of an industrial feed stream containing ethane and water was performed using an in-house code that included an appropriate equilibrium adsorption isotherm. The validated computational model was used to examine the impact of particle size on the process dynamics and the corresponding pressure drop. The water concentration along the adsorption column was also investigated. To increase the process capacity, the packed adsorption bed was divided into two distinct layers, which were operated with different... 

This paper deals with the modeling and simulation of binary liquid-phase adsorption of methyl mercaptan and hydrogen sulfide from a liquid butane stream by zeolite molecular sieve 13X in a fixed bed. The model equations account for the effect of axial dispersion and the inter- and intraparticle, mass-transfer resistances at isothermal operating conditions. Orthogonal collocation and Gill's fourth-order Runge-Kutta methods were used to solve the dimensionless general forms of the 4N-eoupled ordinary differential equations for simultaneous adsorption of the solutes by the adsorbent in a fixed bed. The model predictions were compared to the commercial-scale plant data of an Iranian... 

The separation of xylene isomers is an important application in separation processes that is based on their adsorption properties on different adsorbents. In this work, the Price and Danner method was employed with a neural network to investigate the adsorption behavior of binary systems of p-xylene/m-xylene, p-diethyl benzene/m-xylene, and p-diethyl benzene/p-xylene and the ternary system of p-diethyl benzene/m-xylene/p-xylene at 130 and 175°C. The Redlich-Kister, Wilson, and NRTL models were used to determine the activity coefficients in the adsorbed phase. Comparison with experimental data from the literature indicated that the proposed thermodynamic model would best determine surface... 

Low silicon content SAPO-34 was successfully synthesized using the conventional hydrothermal crystallization in the static condition. Effects of different synthesis conditions including crystallization temperature and the silicon source were investigated through X-ray diffraction patterns. It was concluded that the silicon source had a significant effect on silicon incorporation into the alumino-phosphate building blocks in the course of crystallization. Using precipitated silica instead of silica sol resulted in the formation of impurities of alumino-phosphates phases whose crystalline structures collapse at the high temperature of calcination. For the low silicon SAPO-34 synthesis, the... 

Comparison of the traditional linear heating method of TPD with an original stepwise heating scheme was reported for the first time. Stepwise heating TPD was carried out by keeping the temperature constant as soon as ammonia desorption signal rises until the signal returns to the baseline. More ammonia desorption peaks on a SAPO-34 catalyst were identified using TPD with stepwise heating. The effect of temperature ramp on desorption peak broadening in TPD curve was also addressed. The more distinct ammonia desorption peaks in stepwise TPD indicates that ammonia adsorbs in about five or six different ways on SAPO-34, and attribution of different adsorptions may be explained considering some... 

Nanostructured graphene based membranes demonstrated excellent capabilities in various applications in nanofiltration and energy conversion due to unique atomically smooth surfaces and adjustable pore size or interlayers spacing at Angstrom scales. There are some reports on the osmotic power generation using physical confinements and electrostatic interactions between ions and GO membranes. However, the results indicated insufficient power densities (˂1 W/m2) can be achieved because of swelling of interlayer spacing of the GO membranes upon exposure to aqueous solutions which results in reducing the influence of confinement on ionic motilities. Here, the GO fibers is presented as one... 

Polymeric membrane technology has received extensive attention in the field of gas separation, recently. However, the tradeoff between permeability and selectivity is one of the biggest problems faced by pure polymer membranes, which greatly limits their further application in the chemical and petrochemical industries. To enhance gas separation performances, recent works have focused on improving polymeric membranes selectivity and permeability by fabricating mixed matrix membranes (MMMs). Inorganic zeolite materials distributed in the organic polymer matrix enhance the separation performance of the membranes well beyond the intrinsic properties of the polymer matrix. This concept combines...