scholarly journals Prevention in Thermal Crack Formation in Chabazite (CHA) Zeolite Membrane by Developing Thin Top Zeolite and Thick Intermediate Layers

Nanomaterials ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 2113
Author(s):  
Min-Zy Kim ◽  
Syed Fakhar Alam ◽  
Devipriyanka Arepalli ◽  
Aafaq ur Rehman ◽  
Won-Youl Choi ◽  
...  
Keyword(s):  
Intermediate Layer ◽  
Secondary Growth ◽  
Particle Diameter ◽  
Zeolite Membrane ◽  
Average Particle ◽  
Alumina Support ◽  
Infiltration Process ◽  
Zeolite Membranes ◽  
Thermal Cracks ◽  
Intermediate Layers

Chabazite (CHA) zeolite membranes with an intermediate layer of various thicknesses were prepared using planetary-milled seeds with an average particle diameter of 300, 250, 200, 140, and 120 nm. The 120 nm seed sample also contained several smaller particles with a diameter of 20 nm. Such small seeds deeply penetrated into the pore channels of the α-alumina support during the vacuum-assisted infiltration process. During the secondary growth, the penetrated seeds formed a thick intermediate layer exiting between the zeolite layer and support. A decrease in seed size increased the penetration depth of seeds and the thickness of the intermediate layer, while the thickness of seed coating and zeolite layers was decreased. CHA zeolite membranes with a thin top zeoliate layer and a thick intermediate layer showed an excellent water/ethanol separation factor (>10,000) for 90 wt.% ethanol at 70 ℃ with a total flux of 1.5 kg m−2 h−1. There was no observation of thermal cracks/defects on the zeolite separation layer. The thick intermediate layer effectively suppressed the formation of thermal cracks during heating, since the tensile stress induced in the zeolite layer was well compensated by the compressive stress on the support. Therefore, it was successfully proven that controlling the microstructure of top surface and intermediate layers is an effective approach to improve the thermal stability of the CHA zeolite membrane.

Microwave-Assisted Synthesis and Permeation Performance of NaA Zeolite Membrane by Secondary Growth Method

2014 ◽  
Vol 1053 ◽  
pp. 389-393
Author(s):  
Zhi Lin Cheng ◽  
Ying Ying Liu
Keyword(s):  
Gas Permeability ◽  
Knudsen Diffusion ◽  
Secondary Growth ◽  
Zeolite Membrane ◽  
Microwave Assisted Synthesis ◽  
Vapor Phase Transport ◽  
Zeolite Membranes ◽  
Synthesis Time ◽  
Naa Zeolite ◽  
Naa Zeolite Membrane

The highly intergrown NaA zeolite membranes on seeded α-Al2O3substrate were synthesized by microwave heating method. The preparation of seeds with the size of ca.120nm employed the vapor phase transport method (VPT). The XRD patterns indicated that the pure NaA zeolite membranes formed on the seeded α-Al2O3substrate for varied synthesis times. However, the peak intensity of NaA zeolite membrane with synthesis time of 50min obviously decreased, suggesting that the NaA membrane could take place the dissolution at that time. The SEM images indicated that the NaA zeolite membranes with synthesis time of 15-30min had a good integrity and consisted of highly intergrown zeolite crystals, but the NaA membrane with synthesis time of 50min appeared some large defects, further verifying the result of XRD pattern. The gas permeability showed that the maximum of H2/N2and H2/C3H8permselectivities attained 4.23 and 8.24, respectively, higher than those of the corresponding Knudsen diffusion. These results suggested that the diffusion of gases, at least in part, are affected by the pore size of zeolite and the function of molecular sieving can be embodied on the synthesized membrane.

Synthesis of MCM-22 Zeolite Membrane on a Porous Alumina Support

2014 ◽  
Vol 805 ◽  
pp. 272-278 ◽  
Author(s):  
Antonielly dos S. Barbosa ◽  
Antusia dos S. Barbosa ◽  
Meiry Glaucia F. Rodrigues
Keyword(s):  
Porous Alumina ◽  
Mercury Porosimetry ◽  
Secondary Growth ◽  
Molecular Size ◽  
Zeolite Membrane ◽  
X Ray Diffraction ◽  
Alumina Support ◽  
X Ray ◽  
Ceramic Support ◽  
Separation Of Mixtures

Much interest has been aroused in the application in industrial processes using zeolite membrane, due to its crystalline structure, and narrow pore diameters. These features enable the continuous separation of mixtures based on differences in molecular size and shape and also based on different adsorption properties. This paper reports the synthesis of MCM-22 zeolite membrane, using the method of secondary growth. The MCM-22 zeolite was synthesized by the hydrothermal method and characterized by spectroscopy Energy Dispersive X-ray (EDX), X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM).The ceramic support (α-alumina) was prepared using the technique of forming powder and then subjected to the sintering temperature of 1400 °C/1h and characterized by XRD. The zeolite membrane preparation was performed by the method of secondary growth and characterized by XRD, SEM and mercury porosimetry. The obtained zeolite membrane could be confirmed by X-ray diffraction. From, the obtained SEM pictures it was possible to observe the formation of a homogeneous film on the zeolite surface of the ceramic support (α-alumina).

Template-free synthesis of beta zeolite membranes on porous α-Al2O3 supports

2014 ◽  
Vol 50 (64) ◽  
pp. 8834-8837 ◽  
Author(s):  
Yanting Tang ◽  
Xiufeng Liu ◽  
Shifeng Nai ◽  
Baoquan Zhang
Keyword(s):  
Seed Layer ◽  
Secondary Growth ◽  
Zeolite Membrane ◽  
Beta Zeolite ◽  
Zeolite Membranes ◽  
Organic Templates ◽  
Template Free ◽  
Α Al2o3

The preferentially (h0l)-oriented beta zeolite membrane was prepared on the porous α-Al2O3 support by secondary growth of a beta seed layer in the absence of organic templates.

scholarly journals Study the Effect of Seeding Suspension Concentration of DD3R Particles on the Modified Surface of Α-Alumina Support for Preparing DD3R Zeolite Membrane with High Quality

2018 ◽  
Vol 2 (1) ◽  
Author(s):  
Aynaz Meshkat ◽  
Mohammad Javad Vaezi ◽  
Ali Akbar Babaluo
Keyword(s):  
Secondary Growth ◽  
Dip Coating ◽  
Sem Analysis ◽  
Gas Permeation ◽  
Zeolite Membrane ◽  
Alumina Support ◽  
Suspension Concentration ◽  
Coating Method ◽  
Growth Method ◽  
Modified Surface

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.

scholarly journals Synthesis and Performance of Deca- Dodecasil 3 Rhombohedral (DDR)-Type Zeolite Membrane In CO2 Separation– A Review

2015 ◽  
Vol 14 (2) ◽  
pp. 48 ◽  
Author(s):  
Muhammad Mubashir ◽  
Yeong Yin Fong ◽  
Lau Kok Keong ◽  
Mohd. Azmi Bin Sharrif
Keyword(s):  
Secondary Growth ◽  
High Energy ◽  
Zeolite Membrane ◽  
Co2 Separation ◽  
Inorganic Membranes ◽  
Zeolite Membranes ◽  
Type Zeolite ◽  
And Performance ◽  
Cryogenic Distillation ◽  
Growth Methods

CO2 capture technologies including absorption, adsorption, and cryogenic distillation are reported. Conventional technologies for CO2 separation from natural gas have several disadvantages including high cost, high maintenance, occupy more space and consume high energy. Thus, membrane technology is introduced to separate CO2 due to their several advantages over conventional separation techniques. Inorganic membranes exhibit high thermal stability, chemical stability, permeability and selectivity for CO2 and CH4 separation as compared to other type of membranes. Zeolite membranes are potential for CO2 separation due to their characteristics such as, well define the pore structure and molecular sieving property. Among the zeolite membranes, DDR membranes exhibit highest selectivity for CO2 and CH4 separation. DDR membranes are synthesized by conventional hydrothermal and secondary growth methods. These methods required very long synthesis duration (25 days) due to extremely low nucleation and crystal growth rate of DDR zeolite. In this review, synthesis and performance of DDR membrane in CO2 separation from CH4 reported by various researchers are discussed. Challenges and upcoming guidelines related to the synthesis DDR membrane and performance of DDR membrane also included.

H2/CO2 Gas Separation Characteristic of Zeolite Membrane at High Temperature

2007 ◽  
Vol 26-28 ◽  
pp. 267-270
Author(s):  
Woo Teck Kwon ◽  
Soo Ryong Kim ◽  
Eun Bi Kim ◽  
Seong Youl Bae ◽  
Y. Kim
Keyword(s):  
Gas Separation ◽  
Coal Gasification ◽  
Hydrothermal Reaction ◽  
Low Cost ◽  
Porous Alumina ◽  
Hydrogen Permeability ◽  
Combined Cycle ◽  
Zeolite Membrane ◽  
Alumina Support ◽  
Zeolite Membranes

Due to the need for CO2 sequestration associated with H2 production from fossil fuels, zeolite membrane are very promising due to their low cost, high stability and high permeance. Recently, the faujasite(FAU), the silica/aluminophophate(SAPO-4) framework family of zeolite have been studied for CO2 gas separation. In our study, ZSM-5 membrane was prepared on the porous alumina support using a hydrothermal technique. The thickness of zeolite membrane was controlled by the hydrothermal reaction time and temperature. The prepared zeolite membranes were characterized with SEM and thin film XRD. The hydrogen permeability and selectivity toward carbon dioxide gas were 0.6x 10-6 mole/m2.s.pa and 3.16, respectively. The hydrogen selective zeolite membranes show promising application in hydrogen separation from coal gasification such as Integrated Gasification Combined Cycle (IGCC).

Preparation of ZSM-5 Zeolite Membranes by Combined Hydrothermal Synthesis and Electrophoretic Deposition

2015 ◽  
Vol 654 ◽  
pp. 47-52 ◽  
Author(s):  
Hideyuki Negishi ◽  
Stephanie Reuß ◽  
Wilhelm Schwieger ◽  
Aldo Roberto Boccaccini
Keyword(s):  
Hydrothermal Synthesis ◽  
Electrophoretic Deposition ◽  
Deposition Time ◽  
Secondary Growth ◽  
Zeolite Membrane ◽  
Zeolite Membranes ◽  
Porous Stainless Steel ◽  
Seeding Method ◽  
Micron Size

The preparation of a ZSM-5 zeolite membrane on porous stainless steel disk by hydrothermal synthesis with electrophoretic deposition (EPD) as a seeding method was investigated. Micron size ZSM-5 crystal powder was seeded by EPD on the support disk by using ZSM-5 powder dispersed in ethanol. The seeded amounts were easily controlled by the deposition time during EPD. The membrane after secondary growth had a low amount of zeolite in comparison with the in situ seeding method and the permeance of single gas such as He, N2 and CO2 was also low in comparison with that of the in situ seeding method.

Adsorption of safranine T from aqueous medium by nano mesoporous MCM-41: adsorption equilibrium, kinetics, and thermodynamics

2020 ◽  
Vol 10 ◽  
Author(s):  
Xiao-Dong Li ◽  
Qing-Zhou Zhai
Keyword(s):  
Electron Microscopy ◽  
Ph Value ◽  
Particle Diameter ◽  
Spherical Particles ◽  
Practical Significance ◽  
Average Particle ◽  
Average Pore ◽  
Kinetics And Thermodynamics ◽  
Safranine T ◽  
Mcm 41

Introduction: In industrial production, a small amount of saffron T emissions will cause increase of water color and increase of chemical oxygen consumption, so study of the decolorization of saffron T wastewater has an important practical significance. Methods: MCM (Mobil Composition of Matter)-41 molecular sieve was synthesized by hydrothermal method. Power Xray diffraction and scanning electron microscopy were used to characterize the sample. Safranine T dye was adsorbed from water by the MCM-41 prepared. Kinetics and thermodynamics of the adsorption were studied. Results: The MCM-41 sample presented spherical particles and regular. The BET (Brunner-Emmett-Teller) specific surface area of the sample determined by 77 K low temperature nitrogen adsorption-desorption isotherm was 932 m2 /g. Its average particle diameter was 110 nm. TEM (transmission electron microscopy) results showed that the sample structure presented a honeycomb pore structure and the average pore diameter was 3.0 nm. The results showed that when room temperature was 20 ± 1 ℃, adsorbate safranine T: adsorbent MCM-41 = 20 : 1，the optimum pH value of adsorption was 4.0 and contact time was 20 min, the adsorption rate reached 98.29% and the adsorption capacity was 19.66 mg/g. The entropy change and enthalpy change of the adsorption system are respectively ΔS0 = 157.5 J/(mol·K); ΔH0 = 21.544 kJ/mol. When temperature was 277.15, 293.15, 303.15 K，the free energy change was respectively △G1 0 = -22.107 kJ/mol, △G2 0 = -24.627 kJ/mol, △G3 0 = -26.202 kJ/mol. Conclusion: The adsorption of safranine T by MCM-41 belongs to a pseudo-second-order adsorption. This adsorption accords with the Freundlich equation and belongs to a heterogeneous adsorption. The adsorption is an endothermic reaction of entropy increase, being spontaneous.

scholarly journals A Comparative Evaluation of Nanohydroxyapatite-Enriched Hydrogen Peroxide Home Bleaching System on Color, Hardness and Microstructure of Dental Enamel

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 3072
Author(s):  
Riccardo Monterubbianesi ◽  
Vincenzo Tosco ◽  
Tiziano Bellezze ◽  
Giampaolo Giuliani ◽  
Mutlu Özcan ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Particle Diameter ◽  
Dental Enamel ◽  
Sem Analysis ◽  
Control Group ◽  
Average Particle ◽  
Color Analysis ◽  
Enamel Microstructure ◽  
Prismatic Structure ◽  
20 Nm

This study aimed to evaluate two hydrogen peroxide (HP)-based at-home bleaching systems in order to analyze whether nano-hydroxyapatite (nHA) addition may represent a reliable and safe solution for tooth whitening without altering dental microstructure and hardness. Human third molars (N = 15) were treated with two bleaching agents, one containing 6%HP (6HP) and the other 6% HP nHA-enriched (6HP-nHA) with average particle diameter ranging from 5–20 nm. Their effects on enamel were assessed using a spectrophotometer, Vickers microhardness (VMH) test and Scanning Electron Microscopy (SEM), comparing the treated groups with the non-treated control group (CTR). Color analysis revealed improvement in whiteness in both groups compared to CTR. VMH test results showed no differences among the groups. SEM analysis highlighted no evident changes in the enamel microstructure of tested groups compared to CTR. At high magnification, in 6HP group, a slight increase in irregularities of enamel surface morphology was observed, while 6HP-nHA group displayed removal of the aprismatic layer but preservation of the intact prismatic structure. These results suggest that the 6HP-nHA agent may be recommended to provide reliable whitening treatment, without damaging the enamel micromorphology and hardness.

Separation of Methane from Shuttle Tanker Vents Gases by Adsorption on a Polyurethane/Zeolite Membrane

2017 ◽  
Vol 733 ◽  
pp. 42-46
Author(s):  
Habiba Shehu ◽  
Edidiong Okon ◽  
Edward Gobina
Keyword(s):  
Carbon Dioxide ◽  
Physical Properties ◽  
Crude Oil ◽  
Deep Water ◽  
Separation Factor ◽  
Gas Permeation ◽  
Zeolite Membrane ◽  
Alumina Support ◽  
Molar Flux

Shuttle tankers are becoming more widely used in deep water installations as a means of transporting crude oil to storage plants and refineries. The emissions of hydrocarbon vapours arise mainly during loading and offloading operations. Experiments have been carried out on the use of polyurethane/zeolite membrane on an alumina support for the separation of methane from carbon dioxide and oxygen. The physical properties of the membrane were investigated by FTIR. Single gas permeation tests with methane, propane, oxygen and carbon dioxide at a temperature of 293 K and pressure ranging from 0.1 to 1.0 x 10-5 Pa were carried out. The molar flux of the gases through the membrane was in the range of 3 x 10-2 to 1 x 10-1 molm-2s-1. The highest separation factor of CH4/CO2 and CH4/O2 and CH4/C3H8 was determined to be 1.7, 1.7 and 1.6 respectively.

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