Sharif Digital Repository

Xylene isomers have similar boiling points and, therefore, their separation by conventional distillation is not practical. The industrial separation of these isomers is generally performed by adsorption or crystallization processes, which are very energy consuming. In this work, the various methods of the separation of these isomers have been reviewed and the equilibrium adsorption of these components in liquid phase using two commercial types of zeolite including Z-700 and Na-BETA as adsorbent at 15, 25, and 35 oC and an initial concentration range of up to 50 wt% as well as in single and binary solutions was investigated. It was found that Z-700 adsorbent has no selectivity for the binary... 

In this research a novel palladium nanocatalyst was synthesized over single-wall carbon nanotube (SWNT) support and then applied in the selective hydrogenation of acetylene in an ethylene rich-flow stream. This nanocatalyst displayed a very promising selectivity toward ethylene production upon rising of the temperature, as well as suppressing oligomer formation during acetylene hydrogenation. It was rationalized that the overwhelming governing mechanism for the acetylene hydrogenation over the 0.48 wt% Pd/SWNT was the hydrogen transfer. Furthermore, new operating conditions for selective hydrogenation of acetylene in ethylene rich-flow were introduced through which the selective... 

Supported ionic liquid membranes are prepared by filling the pores of a porous membrane with ionic liquids. Permeability values of carbon dioxide and methane and also selectivity value of CO2⁄CH4 through ionic liquids stabilized on porous alumina membrane supports have been experimentally investigated. We have used [hmim][Tf2N] and two synthesized ionic liquids, 1,6-Di(3-methylimidazolium)hexane bis(trifluoromethylsulfonyl)imide (h[mim]2[Tf2N]2) and 1,3-Di(3-methylimidazolium)propane bis(trifluoromethylsulfonyl)imide (pr[mim]2[Tf2N]2) in our research. The experiments have been done in the temperature range of 27–45 ℃ and pressures of 10–50 kPa and the impact of the temperature and pressure... 

Because of higher hydrogen demand in recent years, study of hydrogen separation from gas mixtures is highly regarded. Because of some parameters such as high surface to volume ratio and ability to withstanding high pressure, polymeric hollow fiber membranes have a good potential of hydrogen recovery. So in this study, fabrication of single-layer and dual-layer hollow fiber membranes have been investigated. Selective polymer that used in both single and dual layer membranes is polyethersulfone. Membranes were fabricated by dry-wet phase inversion method and effects of extrusion rates and their ratio, composition and temperature of polymer solution, composition of bore fluid, coating and air... 

Nano and microsize H-ZSM-5 were synthesized by hydrothermal crystallization method with same batch composition to investigate the effect of crystallite size of H-ZSM-5 in the methanol conversion to propylene (MTP) process. The average particle size of nano and microsize H-ZSM-5 were obtained in the range of 0.15- 0.2 and 1- 2 µm, respectively. Also, optimized catalyst of Petrochemical Research and Technology Company was synthesized using terapropylammonium bromide as template. Nowadays, terapropylammonium bromide (TPABr) is cheeper than terapropylammonium hydroxide (TPAOH); therefore we used it as tamplate. Activity tests were conducted at operating conditions of T= 460˚C, P=1 atm and WHSV... 

Polymeric membranes based on polyaniline and PVDF were prepared by using cast-solvent film method. The effects of various parameters including polyaniline synthesis temparature, thickness of the PANI/PVDF films and feed pressure were investigated. The results obtained from exprimental data showed increasing permeability with reducing the thickness of the film and increasing feed pressure. Increasing polyaniline synthesis temprature increased the permeability of PANI/PVDF films. Reducing the films thikcness and increasing the feed pressure decreased the selectivity of films for the , and . The results showed increasing selectivity for PANI/PVDF films by using PANI produced at 10°C.... 

The aim of this study is to find a formulation to investigate the catalytic effect of the electric field on the kinetic pathway of a chemical reaction. The catalytic effects of the electric field can be explained by the effect of the external electric field on the stability of the transition state relative to the reactants.The effect of the external electric field on the reaction rate for redox reactions have been proven, but this effect seemed unlikely for non redox reactions. Recently, the role of the electric field in the rate of such chemical reactions, as well as its catalytic activity,has been demonstrated experimentally and computationally. In previous studies, reactive components... 

Selective molecule design is one of the great challenges in drug design. Recently, with the introduction of diffusion models, good progress has been made in discovering new pharmaceutical compounds. These tools can produce new and diverse compounds with desired biological properties and activities. In this research, we propose a new framework for designing a molecular linker, the goal of which is to connect two or more molecules with a linker that increases their binding affinity and selectivity. We use a graph neural network to encode molecular features and a diffusion model to generate linker candidates. Also, in this research, we apply the structural features of the protein pocket in graph... 

Hydrogen is emerging as a clean and ideal fuel. However, its dependency on freshwater resources will be a threat to a sustainable environment. Considering the abundance of seawater and the scarcity of freshwater resources, direct electrolysis of seawater to produce hydrogen fuel can be a promising and potential alternative to pure water electrolysis technologies. Seawater contains electrochemically active ions with the nature of competition with the oxidation reaction of water, thus affecting the catalytic activity and, subsequently, the selectivity. From the thermodynamic and kinetic aspect in the electrolysis of seawater, the unfavorable reaction related to the formation of chlorine... 

In this thesis, nitrogen-doped carbon quantum dots were synthesized from anhydrous trisodium citrate and arginine in water solvent by the hydrothermal method, which was used to develop an on-off-on fluorescence sensor. The hydrothermal method is a suitable method for the synthesis of nitrogen-doped carbon quantum dots due to its affordability, availability, rapidity, and safety. Characterization of nitrogen-doped carbon quantum dots was divided into two parts: in the first part, optical properties were investigated using fluorescence photoluminescence (PL) spectrometer and ultraviolet-visible spectrometer (UV-Vis), and in the second part, Fourier transform infrared spectrometry (FTIR),...