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DD3R zeolite powder was synthesized within a brief period using tetramethyl orthosilicate through a sonochemical method combined with hydrothermal treatment. The highest crystallinity with average particle size of 47 nm was achieved within five days. This nano-sized powder was used for seeding the surface of a support modified with TiO2-Boehmite, facilitating the synthesis of a thin (less than 5 µm) and uniform DD3R zeolite layer. The resulting membrane exhibited perm-selectivities of N2 and CO2 over CH4 that were 3 and 4 times greater than those reported in literature. The surface modification of the synthesized layer using a polydimethylsiloxane solution further improved the perm-selectivity of N2/CH4 and CO2/CH4 by up to 12 and 260, respectively. The straightforward synthesis of the initial layer before modification positively influenced the perm-selectivity of N2/CH4, achieving a three-fold increase compared to similar works in the literature.

In this paper, the capability of the Computational Fluid Dynamics (CFD) approach is evaluated to reliably predict the fluid dynamic and the separation performance of Pd membranes modules for gas mixture separation. In this approach, the flow fields of the pressure and velocity for the gas mixture and the species concentration distribution in the selected three-dimensional domains are obtained by simultaneous and numerical solution of continuity, momentum, and species transport (especially, gas-through-gas diffusion term that derived from the Stefan–Maxwell formulation) equations. Therefore, the calculation of the hydrogen permeation depends on the local determination of the mass transfer resistance caused by the gas phase and membrane, which is modeled as a permeable surface of known characteristics. The applicability of the model to properly predict the separation process under a wide range of pressure, feed flow rate, temperature, and gas mixtures composition is assessed through a strict comparison with experimental data. Moreover, in this work, the influence of inhibitor species on the module performance is discussed, which is obtained by implementing the CFD model. The results of the simulation showed that increasing the pressure on the feed side increases the molar fraction of hydrogen gas, the feed inlet flow on the shell side, and the hydrogen permeation through the membrane in the tube side. Comparison of simulation results with laboratory data showed good agreement. The model was obtained with an error of less than 3% at 450K and below 6% for 475K and 500K.

Palladium doped silica membranes were synthesized by the sol-gel method using two different procedures. The first palladium-doped silica membrane (M1) was synthesized with a coating of four layers of silica-palladium sol. The second membrane (M2) was synthesized with a coating of two silica layers followed by a coating of two silica-palladium layers. Scanning electron microscopy (SEM) proved the formation of uniform γ-alumina interlayers on the supports. SEM results for M1 showed that synthesis of a membrane with this procedure leads to the formation of crack on the membrane selective layer. Single gas permeation measurements of H2 and N2 were carried out at room temperature, 100 °C and 550 °C. Gas permeation results revealed that Knudsen diffusion was dominant in permeation of these gases through membrane M1 while the dominant mechanism in permeation of gases through membrane M2 was activated transport which has exhibited different behavior in comparison with M1. This result is due to the activated sublayers of membrane M2. In this case, H2 permeance increases and N2 permeance decreases with increasing temperature, leading to better separation perforamce of membrane M2 over M1 in separation of H2. Therefore, using the activated silica sublayer in the synthesis of M2 can be used as a high potential method to synthesize a selective palladium-doped silica membrane.

A palladium membrane was prepared using the electroless plating technique (ELP) for the separation and purification of hydrogen from a gas mixture. Depending on operating conditions, hydrogen flux from the membrane was in the range of 0.012-0.023 mol.m-2.s-1. The membrane performance in the presence of CO2 was investigated. The results of the GC analysis showed that at a feed concentration of 10% CO2 and a difference pressure of 1-2 bar, no traces of CO2 was observed in the permeate side. However, hydrogen permeation through the membrane decreased due to the occupation of the catalytic active sites by CO2.. At the concentration of 20% CO2 and a difference pressure of 1-2 bar, a peak of methane was detected in the permeate side by the GC analysis, this is related to the diffusion of carbon from the feed side to the permeation side. Study on the topography of the membrane surface showed short height hills and wide valleys on its surface. This topology of the surface conduced high chemical resistance of the membrane, so that the effect of CO2 poisoning was reversible without defect creation on the membrane. Recovery of the poisoned membrane was done by exposing it to hydrogen atmosphere at 500 °C for an hour. The obtained results show that the recovery of hydrogen permeation was up to 99%.

In this study, seeding of DD3R particles as an important step in the synthesis of DD3R membrane with secondary growth method was investigated. Dip-coating method is used for seeding of DD3R particles on the modified surface of α-alumina supports. 0.1, 0.2 and 0.3 wt% aqueous suspensions of the DD3R seeds were prepared and each support was coated three times with dipping time of 240 s. Scanning electron microscopy (SEM) analysis was used for the investigation of the quality of seed layer formed on the support. It is shown that the uniform layer of seeds was formed with 0.2 wt% seed suspension concentration. DD3R zeolite membrane was synthesized via hydrothermal method on the support seeded with 0.2 wt% seed suspension concentration. The X-ray diffraction and SEM analysis confirmed the synthesis of uniform DD3R zeolite membrane layer on the support which can be due to the uniform distribution of the DD3R seeds. Single gas permeation tests of N2, CO2 and CH4 were carried out, so that good perm-selectivity for gas mixtures was observed.

In this present study, various types of TiO2 nanostructures were synthesised via hydrothermal method from a commercial titanium dioxide. The effects of the initial concentration of titanium dioxide and the reaction time on the morphology of synthesised nanostructures were investigated. The TiO2 nanostructures were calcined at 500 °C and examined for the photocatalytic performance by decomposing formic acid as an organic pollutant. Scanning electron microscopy, transmission electron microscopy, Brunauer–Emmett–Teller and X-ray diffraction were employed to characterise the synthesised TiO2 nanostructures. The outcomes showed more influence of reaction time rather than initial TiO2 concentration on the properties of TiO2 nanostructures. Various TiO2 nanostructures such as, nanorods and nanotubes were fabricated at different initial TiO2 concentrations and reaction times. In addition, the synthesised nanorod structures showed higher photocatalytic activity than the nanotubes. This is owing to the presence of rutile–anatase combined crystalline phases in the nanorod structures.

In this research, Polyether block amide (PEBA) containing different loadings of α-Al2O3 particles was deposited on top of the polysulfone (PSf ) supports to form PEBA 1657‒α-Al2O3/PSf multilayer composite mixed matrix membranes (MCMMMs). Multilayer Composite structure was used to overcome the sedimentation of fillers in the polymer matrix. Moreover, alpha phase of the Al2O3 particles was applied to improve the distribution of these particles at higher loadings. SEM, XRD, and FTIR tests were applied to study morphology, crystalline structure, and chemical structure of the membranes, respectively. Gas permeation properties of the membranes were also measured using three different pure gases (CO2, CH4, and N2) at the pressure of 7 bar and temperature of 25 ºC. CO2 permeance and ideal selectivity of CO2/CH4, and CO2/N2 for the optimum MCMMM with 20 wt% loading of α-Al2O3 particles were 25% (117.5 Barrer), 81.5 % (32), and 86.5% (57) higher than that of multilayer composite neat membrane (MCNM), respectively. The molecular simulation results confirmed the results of the experimental studies and approved that the α-Al2O3 particles are right candidates for improving the PEBA performance for CO2 separation. [ABSTRACT FROM AUTHOR]

The hydroisomerization of pure n-pentane over H-mordenite supported Pt-catalyst was investigated in a fixed bed reactor by changing reaction parameters such as temperature, pressure, and WHSV, as well as the H2/HC ratio. The maximum yield of isopentane over Pt/mordenite catalyst was achieved at 220 °C and a relatively low reaction pressure. To address the effect of feed composition on the catalytic performance of the samples, the catalysts were assessed for activity and selectivity in the isomerization of a mixture consisting of n-pentane (70 wt.%) and isopentane (30 wt.%) at 220 °C. The effects of pressure, WHSV, and H2/HC ratio on the catalyst performance were also studied using binary mixtures of the pentane isomers as a feedstock. It was observed that an effect of WHSV and H2/HC on the catalytic performance was similar to its behavior in pure n-pentane isomerization, while the conversion of n-pentane in the binary mixture showed a different trend and had a minimum value at 1.5 bar. It could be due to the presence of isopentane in feed and adsorption phenomenon of binary mixture on mordenite-supported catalyst.

A palladium composite membrane was prepared via electroless plating technique using organic-inorganic method during activation process. The ceramic support surface was modified by two TiO2-boehmite and one γ-alumina layers to avoid Pd penetration in support pores. Thin and defect-free Pd composite membrane was obtained by creating a relative smoothness on the ceramic support and using Pd nanoparticles in the activated layer. The resulting membrane showed an infinite selectivity for H2/Ar with H2 flux in the range of 0.005-0.035 mol/m2s depending on operating conditions. The hydrogen flux was linearly proportional to the pressure difference across the membrane at different temperatures and then the pressure exponent n was very close to 1. According to linear relationship of Arrhenius plot, the activation energy Ea of Pd membrane was calculated to be 22.54 kJ/mol. H2 permeance kept over 0.023 mol/m2s and the separation factor of H2/Ar over infinite at 773 K for 240 h, confirming high potential of the prepared membrane in H2 purification at high temperatures.

The main goal of this work was to synthesize and evaluate the effect of dehydration temperature on the potential application of hydroxy sodalite zeolite membrane. Hydroxy sodalite zeolite membranes were synthesized via direct hydrothermal method onto a tubular alumina support without seeding in a hot air oven. The synthesized membranes were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Permeation tests of H2 and CO2 were carried out in order to investige the applied dehydration temperature effect on the performance of the synthesized membranes. The performance of the synthesized membrane dehydrated at 100 ºC tended to high selectivity compared to that of the rest samples and the maximum separation factor (~21) was achieved with acceptable permeances about 3.810-8 and 1.8*10-9 mol.m-2.Pa-1.s-1 for H2 and CO2, respectively. The low selectivities observed for two other synthesized membranes (dehydrated at 150 and 200 ºC), indicating the formation of defects during the dehydration of these membranes at high temperatures.

In this study the catalytic dehydrogenation of ethylbenzene to styrene was investigated in a simulated tubular sodalite membrane reactor. The high quality microporous sodalite membrane was synthesized by direct hydrothermal method and characterized by single gas permeation measurements. The performance of the prepared membrane showed high potential for application in a dehydrogenation membrane reactor (MR). The performance of the MR was evaluated using a pseudo-homogeneous model of the fixed bed that was developed in this purpose. The obtained results were evaluated in comparison with corresponding predictions for a plug flow reactor (PFR) operated at the same conditions. The modeling results confirmed the high performance of a MR over a conventional PFR. Ethylbenzene conversion and styrene yield increased about 3.45% and 8.99% respectively which is attributed to the effect of hydrogen removal from reaction side. The results demonstrate that the styrene yield in the MR is predicted to be more effective than that of in the conventional PFR.