Microwave vs. conventional synthesis of analcime from clear solutions

Tatlıer, Melkon; Cıǧızoǧlu, K. Barış; Tokay, Begüm; Erdem-Şenatalar, Ayşe

doi:10.1016/j.jcrysgro.2007.04.056

Cited by 29 publications

(16 citation statements)

References 11 publications

(14 reference statements)

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“…However, too dilute solution inhibited the intergrowth The shape of crystals were similar to those reported for ANA zeolite 14) , which existence was observed by XRD. Table 1 shows the influence of hydrothermal synthe- for PV tests due to large defects in the membranes.…”

Section: Preparation Of Sodalite Seed Crystalssupporting

confidence: 81%

【Original Contribution】 Dehydration Performance of Sodalite Membranes

et al. 2015

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Zeolites are crystalline aluminosilicates with welldefined pores and channels of molecular size. Intensive research efforts have been made in the last decades to shape various kinds of zeolite in thin films. Zeolite membranes have been examined in separating liquid mixtures and gaseous mixtures, including dehydration 1) , CO 2 /CH 4 2, 3) , NH 3 /H 2 4) , isomer separations 5) and other separations 6, 7). Successful commercial application of zeolite membranes is reported with LTA-type and T-type zeolite membranes in dehydration 8). One of the unique properties of zeolite is the variety of zeolitic pore size. Sodalite has one of the smallest zeolitic pore size of 0.28 nm 9) , allowing only small molecules, such as water, helium and hydrogen, penetrate into. Accordingly, defect-free sodalite membranes are expected to show significantly high selectivity of small molecules. Several attempts have been made to prepare sodalite membranes 10, 11). However, single gas permeations of helium and nitrogen through sodalite membranes followed Knudsen diffusion mechanism, suggesting a large contribution of inter-crystalline pathways 10). Recently, hydroxyl sodalite membranes are reported to show dehydration peformance 12, 13). Surface-polished flat supports used in these studies may facilitate oriented nucleation and growth of sodalite crystals, and enhanced intergrowth. From the point of scaling up the membrane preparation process, we focused on preparing sodalite membranes on symmetric tubular ceramic supports. Effects of synthesis solution composition, synthesis temperature and crystallization time on the formation of sodalite membranes were studied. Membrane performance was evaluated in pervaporation with ethanol and iso-propanol solutions at 348 K, 0.1 MPa. Influence of feed compositions was also examined. 2. Experimental 2.1 Synthesis of sodalite seed crystals Sodalite crystals were prepared by hydrothermal synthesis with solution having molar composition of 1.00 SiO2: 0.50 Al2O3: 0.96 Na2O: 0.65 NaCl: 20.50 H2O. Alumina hydroxide (Al(OH)3, 100%, Wako), sodium hydroxide (NaOH, 97%, Wako) and distilled water were mixed and heated until the solution became transparent. After cooling the solution to room temperature, sodium chloride (NaCl, 99.99%, Wako) and colloidal silica (Ludox HS-40, Aldrich) were added

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Section: Preparation Of Sodalite Seed Crystalssupporting

confidence: 81%

【Original Contribution】 Dehydration Performance of Sodalite Membranes

et al. 2015

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“…For instance, lower temperatures (<100 °C) favor FAU formation, whereas ANA or cancrinite (CAN) preferentially form at higher temperatures (>100 °C) . Crystallization of GIS (P1 polymorph) in binary mixtures with FAU, SOD, or ANA has been reported by others, though it is unclear why multiphase regions form within such narrow (and often unexpected) regions of the kinetic phase diagram . The presence of multiphase regions also makes it is difficult to draw definitive boundaries within the diagram separating pure phases of each GIS polymorph.…”

Section: Resultsmentioning

confidence: 99%

Synthesis Strategies for Ultrastable Zeolite GIS Polymorphs as Sorbents for Selective Separations

Oleksiak

Ghorbanpour

Conato

et al. 2016

Chemistry A European J

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What is the most significant result of this study? In this study,w ed iscovered that subtle differences in crystal poly-morph structure can have ap rofound influence on material properties. The remarkable aspect of the two polymorphs in this particular study-GIS types P1 and P2-is the fact that their topology is nearly identical, yet as light rotation in the framework along with the replacement of one aluminum atom in the unit cell with as ili-con atom is sufficient to change the thermal stability of the material by more than af actor of two. This unexpected result could potentially impact the design of zeolites for ah ost of applications requiring (hydro)thermally robust isostructures. What was the inspiration for this cover design? When designing the cover,w ew anted to accomplish two objectives. The first was to highlight the hierarchical nature of our col-laborative research that spanned multiple length scales:t hat is, from macroscopic adsorption studies and microscopic materials characterization to atomistic modeling. The cover image highlights bulk sorbents that can be used for separations, am icroscopic image of az eolite crystal framework, and an individual pore operating as as ize-exclusion sieve. As econd aspect that we wanted to emphasize was the relevance of our findings to applications in the energy and chemicals industries. In our study,w eu sed ac ommer-cially viable approach to prepare GIS-type zeolites. To this end, their performance as selective sorbents may prove beneficial for expanding this work beyond the benchtop to be of practical use in industrial separations or adsorption technologies. What other topics are you working on at the moment? The research programs of the three principal investigators-Grabow,M otkuri, and Rimer-all fall under the general umbrella of nanoporous materials. Each of us studies zeolites, but for different applications-Grabow and Rimer focus on catalysis, whereas Mot-kuri, in addition to zeolites, is also interested on metal-organic frameworks for their sorption/separation applications. We are continuing to investigate aw ide range of open framework materials for these applications. An underlying theme of our work is the elu-cidation of structure-performance relationships, and the design of novel pathways to generate new/improved materials in pursuit of advancing these fields of research beyond current state-of-the-art technologies. Invited for the cover of this issue are the groups of R. K. Motkuri and J. D. Rimer at the Pacific Northwest National Laboratory and University of Houston, respectively.T he image depicts bulk sorbents that can be used for separations, am icroscopic image of az eolite crystal framework,a nd an individualp ore operating as as ize-exclusion sieve. Read the full text of the ar

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“…However, aluminum did not accumulate and was found to be the limiting element for zeolite growth. It is clear that the accumulation of Si as the waste was reused favored the formation of analcime [ 25 ]. This indicated that in order to further increase the crystallinity of the final analcime product, both crystallization time and the Si/Al ratio of the reacting slurry needs to be optimized.…”

Section: Resultsmentioning

confidence: 99%

Waste Minimization Protocols for the Process of Synthesizing Zeolites from South African Coal Fly Ash

2013

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Production of a high value zeolite from fly ash has been shown to be an avenue for the utilization of South African fly ash which presently constitutes a huge disposal problem. The synthesis of zeolites Na-P1 and analcime on a micro-scale has been successful and preliminary investigation shows that scale-up synthesis is promising. However, the post-synthesis supernatant waste generated contains high levels of NaOH that may constitute a secondary disposal problem. A waste minimization protocol was developed to reduce the volume of waste generated with a view to enhancing the feasibility of the scale synthesis. Series of experiments were conducted in 100 mL jacketed batch reactors. Fly ash was reacted with 5 Mol NaOH on a 1:1 mass basis during the aging step, followed by hydrothermal treatment in which ultrapure water was added to the slurry. This study shows that by re-introducing the supernatant waste into the experiments in such a way that it supplies the required reagent (NaOH) for the zeolite synthesis, zeolite Na-P1 and analcime can be synthesized. It also shows that the synthesis process can be altered to allow up to 100% re-use of the supernatant waste to yield high value zeolitic products. This study effectively constructed two protocols for the minimization of waste generated during the synthesis of zeolites from South African coal fly ash. This result could be used to establish a basis for legal and environmental aspects involved in the commission of a full-scale plant synthesizing zeolites NaP1 and analcime.

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Microwave vs. conventional synthesis of analcime from clear solutions

Cited by 29 publications

References 11 publications

【Original Contribution】 Dehydration Performance of Sodalite Membranes

【Original Contribution】 Dehydration Performance of Sodalite Membranes

Synthesis Strategies for Ultrastable Zeolite GIS Polymorphs as Sorbents for Selective Separations

Waste Minimization Protocols for the Process of Synthesizing Zeolites from South African Coal Fly Ash

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