Recently, Microporus and Mesoporous Materials has published the latest research results from ZJUI on the rapid preparation of plate-like zeolite, which reduced the crystallization time of molecular sieves from a few days to 15 minutes. The first author of the paper is Li Pingping, a doctoral student jointly cultivated by ZJUI and the School of Materials Science and Engineering, ZJU, and the only corresponding author is Assist Prof. Kemal Celebi from ZJUI. Other authors include Prof. Donghun Kim from Chonnam National University and Han Lei, a doctoral student from the School of Materials Science and Engineering at Tsinghua University.
In Assist Prof. Kemal's research group, Li Pingping shared that she enjoyed excellent research platform and atmosphere, which greatly helped her expand her academic perspective and research ideas. Based on this research topic, she has attended three conferences in the past year, including two international conferences." (2023 ACS Annual Conference and 9th International Zeolite Membrane Metting), a domestic conference (16th National Thin Film Conference) and gave two English and one Chinese oral presentation at the conferences. Abundant communication opportunities enable her to discuss and exchange with peers and scholars in the field and inspire each other, continuously improving her academic level and research abilities.
This research, which once had little results yielded, troubled Li Pingping for a long time, "We spent nearly a year working on the rapid preparation strategy for two-dimensional molecular sieve materials, but we have not made significant progress. At that time, Assist Prof. Kemal patiently comforted and affirmed me, encouraging me not to lose heart, and contacted peer experts for help. Assist Prof. Kemal accompanied me to look for and solve problems. From being lost and unsure where to go, to now achieving phased results in our research and successfully publishing it", Li Pingping has deep feelings. Pingping said, "Although fundamental science research is difficult and tiring, Assist Prof. Kemal has provided great support in research and testing funds, as well as spiritual support. Although sometimes I may feel discouraged, as long as I persist, I will be able to keep up with it. I am very grateful to the self who never gave up hope, and I also sincerely thank Assist Prof. Kemal for providing me with comfort and support, which has kept me motivated to keep moving forward on the path of research. "
01
Research Background
Since energy consumption became an important contributor to climate change owing to carbon emissions, energy-saving behavior and expenditure at the household level have been attracting scholars’ and policymakers’ attention. In the fields of petrochemicals and energy, the maximum energy consumption mainly comes from the separation and purification of chemicals. Membrane separation is the ideal technology that can achieve low energy consumption and low-cost separation. However, so far, there is still a trade-off effect in the membrane separation, that is both high permeation and high selectivity cannot be achieved simultaneously. Therefore, the materials for membrane fabrication are important to improve the separation performance. Zeolite, molecular sieves, can separate molecules with size exclusion effect. Specially, they are widely used in chemical industries, such as catalysis and gas separation due to their inherent nanoscale microporous structure, high surface area, and high thermal stability. In recent years, b-oriented MFI zeolite, in particular, can enable fast molecular sieving across sub-nm intrinsic pores. However, there is still a lack of rapid controllable preparation technology for large 2D zeolites. Although thin zeolites can be obtained by exfoliation, it requires complicated processes and yields small lateral size. Meanwhile, current bottom-up synthesis methods can provide better yield at acceptable cost, albeit at high temperature and pressure, also requiring a timespan of days. Therefore, both above methods are difficult to achieve rapid preparation of molecular sieves and rapid optimization of morphology control.
02
Result Introduction
Here, the research group of Assist Prof. Kemal proposed a Fast Synthesis Strategy (FSS) using a mini stainless-steel reactor as a new reactor for the rapid preparation of zeolite. Due to the high heat transfer effect of stainless-steel material, the problem of heat transfer lag in traditional reactors is avoided, which can shorten the crystallization time of zeolite from a few days to 15 minutes. The rapid synthesis method can regulate the thickness and lateral size of molecular sieve nanosheets, greatly improving the efficiency of basic research.
▲ Fig. 1. Schematic diagram of rapid preparation of zeolite
In this work, a stainless-steel tubular reactor with a length of 15 cm, a diameter of 6 mm, and a wall thickness of 0.7 mm was used to produce crystalline MFI within a 15-minute hydrothermal synthesis, as shown in Figure 2a. The crystallinity and orientation of MFI nanosheets were also confirmed by X-ray diffraction patterns (Figure 2c) and high-resolution transmission electron microscopy (Figure 2b). In addition, the diffraction peak intensity of the sheet-like MFI crystals prepared by FSS did not increase at approximately 23o after 15 minutes, indicating that crystallization and growth were almost completed within 15 minutes. The results in Figure 2c also confirm this, where the size of the c-axis does not change over time and remains stable at ~1.3 µm from 15 minutes to 1 hour. However, the sheet-like MFI crystals obtained through FSS exhibit a similar morphology to conventional autoclave-synthesis (Figure 2d), but synthesis through an autoclave typically takes 2-3 days. If we use transportation to describe the synthesis of zeolite, the traditional synthesis method would be the old-fashioned train, the microwave method might be high-speed rail, and the rapid synthesis of FSS would be the Maglev.
▲ Fig. 2. Comparison of the FSS and the conventional synthesis method (a) Scanning electron microscopy (SEM) image of platelike MFI crystals prepared in the tubular reactor within 15 min hydrothermal treatment, inset: the white rectangle on the right is TEM image of small crystalline particles referred by the white arrow. (b) TEM image of platelike crystals prepared within 15 min hydrothermal treatment in the tubular reactor, inset: FFT pattern. (c) XRD spectra of the platelike MFI crystals obtained by the FSS and by the conventional autoclave, with synthesis times indicated on each spectrum. The inset describes the changes of average crystal dimensions along the a-axis and c-axis over the synthesis time in the tube. (d) SEM image of the platelike MFI crystals obtained from autoclave after 2 days. All experiments in (a-d) were conducted following the gel composition of 0.15 TPAOH: SiO2: 1.6 NH4F: 15 H2O. (e) Schematic of heat transfer in the tubular reactor and the autoclave. The tubular reactor is heated up in the oil bath and cooled down by water within 1~2 min. The autoclave is heated up and cooled down by air in the oven within 2 h. (f) The temperature profile for the tubular reactor (15 min) and the autoclave (2 days). The red and blue curves represent heating and cooling, respectively.
03
Conclusions
Fig. 2. Comparison of the FSS and the conventional synthesis method (a) Scanning electron microscopy (SEM) image of platelike MFI crystals prepared in the tubular reactor within 15 min hydrothermal treatment, inset: the white rectangle on the right is TEM image of small crystalline particles referred by the white arrow. (b) TEM image of platelike crystals prepared within 15 min hydrothermal treatment in the tubular reactor, inset: FFT pattern. (c) XRD spectra of the platelike MFI crystals obtained by the FSS and by the conventional autoclave, with synthesis times indicated on each spectrum. The inset describes the changes of average crystal dimensions along the a-axis and c-axis over the synthesis time in the tube. (d) SEM image of the platelike MFI crystals obtained from autoclave after 2 days. All experiments in (a-d) were conducted following the gel composition of 0.15 TPAOH: SiO2: 1.6 NH4F: 15 H2O. (e) Schematic of heat transfer in the tubular reactor and the autoclave. The tubular reactor is heated up in the oil bath and cooled down by water within 1~2 min. The autoclave is heated up and cooled down by air in the oven within 2 h. (f) The temperature profile for the tubular reactor (15 min) and the autoclave (2 days). The red and blue curves represent heating and cooling, respectively.
Article Link: https://doi.org/10.1016/j.micromeso.2023.112905
Research Group of Assist Prof. Kemal Celebi
Graphene and other 2D materials have recently attracted tremendous attention among membrane scientists due to their novel ultrafast membrane transport paradigm associated with their atomic-scale thickness. In the last few years, such membranes have been demonstrated to exhibit ultrahigh gas permeances, ultrafast selective proton transport and highly efficient water desalination. However, all such demonstrations have been small-scale proof-of-concept studies, due to the difficulties related to both preparing large scale monolayers without defects and controllably perforating such thin layers. The research group of Assist Prof. Kemal Celebi focuses on solving the bottlenecks for ultrathin membrane manufacturing by developing novel interfacial transfer methods and using intrinsically porous 2D materials. Assist Prof. Celebi has extensive experience in manufacturing atomically-thin membranes and testing fundamental transport properties – in particular, demonstrating one of the first nanoporous graphene membranes (Science 344, p289) and preparation of 2D material membranes by interfacial transfers.
Kemal Celebi is a materials scientist, with a background in physics and mechanical engineering. He obtained his BS and MS degrees in physics from Bilkent University, Turkey and from MIT, USA, respectively. He received his PhD degree in mechanical engineering from ETH Zurich in 2014, where his thesis focused on through-pore graphene membranes. After his PhD study, Dr. Celebi initially worked as a faculty member in the department of materials science at Bilkent University, and subsequently, as a senior scientist at ETH Zurich. Dr. Celebi’s research focuses on multiscale manufacturing of nanomaterials, ultrathin membranes and functional coatings.
