Accepted Manuscript Microwave hydrothermal synthesis and performance of NaA zeolite monolithic adsorbent with honeycomb ceramic matrix Yutang Fang, Yihao Hu, Xianghui Liang, Shuangfeng Wang, Shuangquan Zuo, Xuenong Gao, Zhengguo Zhang PII:
S1387-1811(17)30639-X
DOI:
10.1016/j.micromeso.2017.09.027
Reference:
MICMAT 8568
To appear in:
Microporous and Mesoporous Materials
Received Date: 10 June 2017 Revised Date:
30 August 2017
Accepted Date: 25 September 2017
Please cite this article as: Y. Fang, Y. Hu, X. Liang, S. Wang, S. Zuo, X. Gao, Z. Zhang, Microwave hydrothermal synthesis and performance of NaA zeolite monolithic adsorbent with honeycomb ceramic matrix, Microporous and Mesoporous Materials (2017), doi: 10.1016/j.micromeso.2017.09.027. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT Figure captions: 1. Fig. 1. SEM photos of NaA zeolite monolithic adsorbents prepared with different methods 2. Fig. 2. Effect of CaCl2 concentration on the appearance of honeycomb ceramic matrix
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3. Fig. 3. Effect of seed coating on synthesis of NaA zeolite monolithic adsorbent 4. Fig. 4a. XRD patterns of NaA zeolite monolithic adsorbents synthesized with different crystallization temperature
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5. Fig. 4b. Relationship of relative crystallinity and saturated adsorption ratio of NaA zeolite monolithic adsorbents synthesized with different crystallization temperature
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6. Fig. 4c. Relationship of relative crystallinity and saturated adsorption ratio of NaA zeolite monolithic adsorbents synthesized with different crystallization time 7. Fig. 5. Static Adsorption curves of NaA zeolite monolithic adsorbents with different preparing
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8. Fig. 6. TPD curves of NaA zeolite monolithic adsorbents prepared with different methods at
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Fig. 1 SEM photos of NaA zeolite monolithic adsorbents prepared with different methods
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Fig. 2 Effect of CaCl2 concentration on the appearance of honeycomb ceramic matrix
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Fig. 3 Effect of seed coating on synthesis of NaA zeolite monolithic adsorbent
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Fig. 4a XRD patterns of NaA zeolite monolithic adsorbents synthesized with different crystallization
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temperature
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Fig. 4b Relationship of relative crystallinity and saturated adsorption ratio of NaA zeolite monolithic
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adsorbents synthesized with different crystallization temperature
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Fig. 4c Relationship of relative crystallinity and saturated adsorption ratio of NaA zeolite monolithic
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adsorbents synthesized with different crystallization time
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Fig. 5 Static Adsorption curves of NaA zeolite monolithic adsorbents with different preparing
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Fig. 6 TPD curves of NaA zeolite monolithic adsorbents prepared with different methods at
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Microwave hydrothermal synthesis and performance of NaA zeolite monolithic adsorbent with honeycomb ceramic matrix
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Yutang Fang*, Yihao Hu, Xianghui Liang, Shuangfeng Wang Shuangquan Zuo, Xuenong Gao, Zhengguo Zhang
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Key Laboratory of Enhanced Heat Transfer and Energy Conservation of the Ministry of Education, South China University of Technology, Guangzhou 510640, People’s Republic
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of China
*Corresponding author. Tel./fax:+86-20-87113870
E-mail address:
[email protected] (Y. T. Fang),
Liang),
[email protected](S.
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Hu),
[email protected](X. H.
yihao_h @163.com (Y. H. F. Wang),
[email protected](S. Q. Zuo),
[email protected](X. N. Gao),
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[email protected] (Z. G. Zhang)
ACCEPTED MANUSCRIPT Abstract The NaA monolithic adsorbent composed of NaA zeolite and honeycomb ceramic matrix has been considered as an up-and-coming adsorbent for the utilization in adsorptive
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rotary dehumidification system. This contribution introduced a novel synthesis strategy of NaA monolithic adsorbent on the honeycomb ceramic matrix —— in situ microwave hydrothermal synthesis. Meanwhile, the influence of several key factors during the
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synthesis process, including CaCl2 concentration, seed coating, microwave temperature and
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time, on the performances of the adsorbent was systematically analyzed. The crystalloid phase and the morphology of the as-synthesized adsorbent were used to determine by X-ray powder diffraction and Scanning electronic microscope,and its adsorption and desorption performances were measured by static adsorption and temperature programmed desorption,
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respectively. The test results of X-ray powder diffraction and Scanning electronic microscope indicated that NaA zeolite with cubic form and particle size of about 0.9 µm could be quickly in situ synthesized on both the surface and the void of honeycomb ceramic
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matrix within 35–55min by microwave irradiation. Because of smaller size, more uniform
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distribution of NaA zeolite, the novel monolithic adsorbent synthesized by microwave method showed more excellent adsorption and desorption performances than that by traditional impregnation technology, which displayed a higher saturated adsorption ratio and faster early adsorption rate, as well as a lower desorption activation energy. Keywords: NaA zeolite monolithic adsorbent; Honeycomb ceramic matrix; In situ microwave synthesis; Adsorption performance; Desorption performance
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1
Introduction With the increasing demands of indoor environmental comfort and health of the society,
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the indoor air quality (IAQ) in air-conditioning and dehumidification field draws intensively attention [1-3]. Owing to the features of being free from Chlorofluorocarbons (CFCs), using low grade thermal energy and controlling humidity and temperature separately, adsorptive
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rotary dehumidification air conditioning system, which contains desiccant materials, is
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particularly suitable for improving IAQ and deep dehumidification situations [4]. Desiccant materials, which play a crucial role in the adsorptive rotary dehumidification system due to their characteristics, such as enormous affinity to sorb water and considerable ability to hold water, have a major impact on the performance of dehumidification and air conditioning
desiccant materials.
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system [5].Therefore, it is of primary importance to develop innovative high - performance
For rotary desiccant dehumidification, researchers are on the way looking for suitable
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desiccant materials. A variety of adsorbents such as activated carbon, activated alumina,
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lithium chloride, silica gel and molecular sieve have been investigated in recent years. For porous carbons, methanol, ethanol and ammonia are common adsorbates, which would make these adsorbents remain relatively attractive for absorptive air conditioning system [6-8]. Lithium chloride has a higher hygroscopic capacity and a lower reactivation temperature compares to porous solid adsorbents. However, the lyolysis phenomenon may happen in its application, resulting in the loss of desiccant and drop in the performance of the rotary desiccant dehumidification system. This often takes place after the formation of
ACCEPTED MANUSCRIPT solid crystalline hydrate of Lithium chloride [9]. Silica gel has the advantages of stable characteristics and low cost. Ti-doped silica gel prepared by Fang and co-workers [10] shows high adsorption rate in the early stage of adsorption process. However, the adsorption
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capacity of silica gel decreases quickly with the increase of temperature, especially under low partial pressure of water vapor. Metal-organic frameworks (MOFs) have been widely concerned thanks to their outstanding water-vapor adsorption rate as well as excellent
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adsorption capacity. The only prerequisite of using MOFs, which are considered potentially
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interesting for air conditioning system, is overcoming the obstacles of low hydrothermal stability, e.g., HKUST-1 and DUT-4 [11].
Novel adsorbents with specifically tailored properties for rotary desiccant dehumidification system are becoming increasingly demanding. Three key principles for
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selecting appropriate desiccant materials should be taken into consideration in adsorptive rotary dehumidification system: (1) the desiccant materials should possess large saturated adsorption amount and can be reactivated easily; (2) the adsorption performance of the
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desiccant materials should approach the Type 1M material [4]; and (3) the desiccant
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materials should maintain a long-term thermal stability. Thus, crystalline NaA molecular sieve which represents the optimum shape (isotherm
type I) with high water sorption uptake at relatively low humidity (RH10%) and high thermal stability in high temperature makes up rotary desiccant wheel that has been considered particularly suitable for rotary desiccant deep dehumidification application [12,13]. Usually, NaA zeolite monolithic adsorbent with honeycomb ceramic matrix is
ACCEPTED MANUSCRIPT prepared by impregnation method [14,15], namely, using inorganic glue such as water glass and silica sol as dispersant and adhesive, NaA zeolite is deposited on the surface and the void of ceramic matrix. However, some shortcomings exists in this process. Industrial NaA
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zeolite with large particle size (about 2µm) is easy to sedimentate, resulting in an uneven dispersion on the matrix. On the other hand, the use of inorganic glue with no adsorption ability reduces the content of NaA zeolite in the monolithic adsorbent, and results in
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adsorption performance decline. Therefore, in this contribution, a novel technical solution of
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NaA zeolite monolithic adsorbent with honeycomb ceramic matrix, namely in situ microwave hydrothermal synthesis strategy is proposed. So far, this research work has not been reported, however, the process is similar to the synthesis of NaA zeolite membrane [16]. NaA membrane is usually synthesized on the surface of dense α-Al2O3 tubular
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supports [17-19]. Significant differences exist between NaA zeolite monolithic adsorbent and NaA zeolite membrane. The substrate applied in our work is honeycomb ceramic fiber paper with high porosity. In addition, since NaA molecular sieve dispersed on both the
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surface and the void of honeycomb substrate, which can increase the membrane thickness adsorption capacity instead of
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and the NaA zeolite mass fraction, resulting in a high
improving pervaporation property of NaA zeolite membrane on the dense tubular support. There are various methods for the development of NaA zeolite membrane, including
in situ hydrothermal synthesis [20-22], secondary (seeded) growth [23,24], multi-stage synthesis [25] and microwave synthesis [26-28], etc. In situ hydrothermal synthesis is the best-studied method. The preparation of zeolite films by in-situ crystallization on the supports under hydrothermal conditions results in a strong interface due to the chemical
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controlling the seed size and density, the orientation of the final film can be varied [30]. The presence of seeds on support surface plays an important role in membrane formation. A new method named microwave synthesis has been developed for synthesis of zeolite membrane
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in recent years. Microwave heating has the advantages over conventional heating in
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promoting faster crystallization, uniform and small crystal sizes and broad synthesis composition by shortening the synthesis time [31]. However, it is not easy to prepare high performance zeolite membranes only by the use of microwave synthesis. Microwave techniques combining with different strategies could create some novel synthesis routes
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[32-35].
Therefore, we report a novel NaA zeolite synthesis strategy on the honeycomb ceramic matrix——in situ microwave synthesis together with secondary growth. Our goal is
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to synthesize NaA zeolite monolithic adsorbent with smaller particle size and uniform
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distribution on the ceramic matrix by microwave process, so as to improve the NaA zeolite adsorption and desorption performances. 2
Experimental
2.1 Materials and pretreatment 2.1.1 Materials NaA zeolite powder (Industrial grade) was purchased from UOP Co., America. The required chemical reagents (AR grade) of the synthesized NaA zeolite, including sodium
ACCEPTED MANUSCRIPT aluminate (NaAlO2), sodium metasilicate nonahydrate (Na2SiO3⋅9H2O) and sodium hydroxide (NaOH), and treating agent of the matrix (calcium chloride, CaCl2) were obtained from Shanghai Jingchun Scientifical Co., Ltd., China. All raw materials were used
2.1.2 Pretreatment Preparation of NaA zeolite seed crystal
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directly.
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A precursor gel mixture with a molar ratio of 1.0 Al2O3: 0.642 SiO2: 1.883 Na2O:
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227.7 H2O was evenly mixed, and the NaA seed crystal was synthesized by microwave hydrothermal method. The details followed the synthesis process of NaA zeolite monolithic adsorbent below. The 1% (mass fraction, the same as below) NaA zeolite seed crystal suspension was prepared by dispersing zeolite seed in deionized water followed by a
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KQ2200 Ultrasonic Cleaner (Kunshan Ultrasonic Instruments Co., Ltd., China) treatment. Treatment of honeycomb ceramic matrix Using silica sol as adhesive, the honeycomb ceramic matrix with a cylinder of 4
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(diameter) × 6(length) cm was rolled by single-faced corrugated paper from Qingdao HSJ treated in sequence with
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Environmental Protection Technology Co., Ltd. The matrix was
impregnation of 2% CaCl2 solution for 5 min, drying in oven for 24h, calcining at 600oC for 3h, and cleaning three times with deionized water. Seed coating
The pretreated honeycomb ceramic matrix was dipped in 1% seed crystal suspension for 5min in a glass breaker with ultrasonic treatment. The seed-coated matrix was then dried at 60 oC for 2h.
ACCEPTED MANUSCRIPT 2.2 Synthesis of NaA zeolite monolithic adsorbent A precursor gel mixture with a molar ratio of 1.0 Al2O3: 0.481SiO2: 1.732 Na2O: 230.1 H2O was evenly mixed by adding aluminate solution to silicate solution under vigorous
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stirring for 1h. The aluminate solution was prepared with NaOH and NaAlO2 dissolved in deionized water till a clear and homogenous solution was formed. The silicate solution was obtained by mixing Na2SiO3⋅9H2O in deionized water.
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For comparison, NaA zeolite monolithic adsorbent samples were accomplished by
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microwave irradiation and impregnation method, respectively. The typical microwave procedures were as follows: First, placed the seed-coating honeycomb ceramic matrix vertically in a 100 mL Teflon-lined autoclave, then poured the gel mixture into the autoclave and sealed it. Second, crystallization was conducted under autogenous pressure in a
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MDS-6G microwave oven (SINEO Microwave Chemistry Technology Co., Ltd, China) o under 160 C for 45min. Third, the coarse product was thoroughly washed with deionized
water, then dried at 60 oC overnight. Finally, the as-synthesized sample was activated at 550 C for 3 h. The procedures of impregnation method producing NaA zeolite monolith were
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o
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accomplished according to Ref. 19, and the sample was also activated at 550 oC for 3 h. Fig.1 shows scanning electronic microscope (SEM) images of NaA zeolite monolithic
adsorbents obtained by different synthesis methods. The industrial NaA zeolite monolith produced by impregnation method is shown in Fig. 1a (Front) . The ceramic fiber was clearly visible and some of which was covered by NaA zeolite with particle size of about 2 µm, cubic crystal form and an uneven distribution. It indicates that the interaction between the ceramic fiber and adsorbent is not compact, resulting in the zeolite easily fall off in the
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Fig.1b is the cross-section views of the monolithic adsorbents. There were significant differences between the two adsorbents obtained by different approaches in morphology despite the thickness of NaA zeolites were basically the same (about 400µm). The rough
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surface and bare fiber could be observed on the matrix after impregnation, while the surface
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was smooth and dense with good uniformity obtained by microwave synthesis. This
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explains why microwave heating method is used to prepare NaA zeolite crystals.
Fig. 1 SEM photos of NaA zeolite monolithic adsorbents prepared with different methods 2.3 Characterization and performance of the NaA monolithic adsorbents
ACCEPTED MANUSCRIPT X-ray powder diffraction (XRD, Shimadzu Analytic Instrument Co., Japan) data of the samples were collected on a XRD-6100 diffractometer with Cu Ka radiation (λ= 1.54056 Å) in the range of 2θ 5–50 Cwith step size of 0.02°. In order to quantitatively assess synthesis o
obtained by using the following formula:
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conditions, the concept of relative crystallinity is introduced in our work, which can be
Rc = (h1+h2+h3+h4)/ (H1+H2+H3+H4) ×100%
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where h1, h2, h3 and h4 refer to the intensity of the sequential four diffraction peak of
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synthesized NaA zeolite from left to right. H1, H2, H3 and H4 refer to the intensity of the sequential four peak of industrial NaA zeolite from left to right as standard. The surface morphology was characterized using a LEO 1530 VT field emission scanning electron microscope (SEM, LEO Electron Microscopy Ltd., England) with
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Au-target and accelerating voltage of 25 kV.
The adsorption performance of the activated NaA zeolite monolithic adsorbent was tested by the static adsorption experiment in a constant temperature and humidity Chamber
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(Young Chenn Instrument Co. Ltd., China) at 25 oC and 60% relative humidity (RH) to
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simulate the work condition of rotary desiccant dehumidification system. The weight change of the adsorbent at a suitable time interval (60s) was recorded using an electronic balance (Sartorius S201, Germany) until the saturation of adsorption (no significant successively weighing difference). The adsorption ratio (R) and saturated adsorption ratio (Rs) was obtained by using the following formula, respectively: R = (M-M2)/ (M2-M1) ×100% Rs = (M3-M2)/ (M2-M1) ×100%
ACCEPTED MANUSCRIPT where M and M3 refer to the weight of the adsorbent during adsorption and after adsorption saturation, respectively. M1 and M2 refer to the weight of honeycomb ceramic matrix and the activated NaA zeolite monolithic adsorbent, respectively.
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Desorption performance of the monolithic absorbents with different methods was measured by temperature-programmed desorption (TPD) spectra obtained on an Auto Chem II 2920 Chemisorption analyzer (Micromeritics instruments Co., Ltd., USA) [53]. High
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purity helium gas was used as carrier gas and water vapor as adsorbate. The programmed
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desorption was carried out in the temperature range of 300 – 600 K at constant heating rate of 4, 6, 8, 10 and 12 K min-1, respectively. 3
Results and discussion
By investigating a wide range of synthesis parameters such as CaCl2 concentration, seed
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coating, microwave heating temperature and time, pure and perfect NaA monolithic adsorbent was successfully synthesized using microwave technique combined with the secondary growth method in this work.
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3.1 Synthesis of NaA monolithic adsorbent
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3.1.1 Effect of CaCl2 concentration The honeycomb ceramic matrix was severely corroded when placed in precursor
solution due to the strong alkaline of synthesis solution, thus, the ceramic corrugated substrate should be modified. Impregnation with CaCl2 solution and then calcination will form a thin layer of calcium silicate gel on the surface of ceramic substrate, which can prevent from corrosion of alkaline solution. The appearance of synthesized NaA monolithic adsorbents is shown in Fig. 2. The edges of the matrix without impregnation of CaCl2
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adsorbents. Therefore, considering the economic and appearance factors, the 2% CaCl2
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solution is the best choice.
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Fig. 2 Effect of CaCl2 concentration on the appearance of honeycomb ceramic matrix
3.1.2 Effect of seed coating The presence of the seed crystal on the matrix surface plays an important role in the
synthesis of NaA zeolite, which gives flexibility to control the NaA zeolite formation process. Dipped coating of the seed crystal on the surface and the void of the support would induce the formation of NaA zeolite nuclei and the absorbent. Fig.3 shows the XRD patterns of NaA zeolite prepared by microwave heating. The
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the support and prevent its crystal phase transformation during microwave heating.
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Fig. 3 Effect of seed coating on synthesis of NaA zeolite monolithic adsorbent 3.1.3 Effect of crystallization temperature and time
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In order to investigate the effect of temperature and time on the crystallization of NaA
monolithic adsorbent, we examined the products taken from 90, 120, 140, 160 and 180 oC. Fig. 4a shows that at 90℃, no NaA zeolite crystal formed on the support. At 120 oC, very weak reflections indicated the presence of small amount of the NaA zeolite crystals. Increasing crystallization temperature to 160 oC, the XRD patterns of the crystals matched well with the standard patterns with high crystallinity. Thus, the resulting products are very sensitive to the o crystallization temperature. While phase transformation occurred at 180 C ,
the intensity of
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Fig.4b presents the relationship between relative crystallinity (Rc) and saturated adsorption ratio (Rs) of NaA zeolite monolithic in varied temperature, which keeps a similar
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trend at different synthesis temperature. The water adsorption ratio was almost 0% and no peak o was observed at 90 C, while the strongest Rc (74.2%) and the highest Rs (23.3%) of NaA
zeolite appeared at 160 C. After that, both crystallinity and adsorption ratio decreased with the o
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increasing temperature.
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Fig. 4c shows that the relationship of relative crystallinity and saturated adsorption ratio of the crystals taken from different time, which keeps a similar trend with crystallization temperature. After 25 min of microwave heating , NaA zeolite was already crystallized on the support, which could be confirmed by XRD (not shown here), while the crystallinity and
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saturated adsorption ratio of NaA zeolite was very low (below 10%). As for the 45 min results, not only the typical peaks of NaA zeolite appeared, but also the peaks of dense zeolite emerged with the highest saturated adsorption ratio. Prolonging the crystallization duration to 55 min led
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to decreased crystallinity and saturated adsorption ratio, despite the generation of the dense
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NaA zeolite phase. It turns out that the optional microwave heating time is 45 min under the temperature of 160 oC.
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Fig. 4a XRD patterns of NaA zeolite monolithic adsorbents synthesized with different
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crystallization temperature
Fig. 4b Relationship of relative crystallinity and saturated adsorption ratio of NaA zeolite monolithic adsorbents synthesized with different crystallization temperature
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Fig. 4c Relationship of relative crystallinity and saturated adsorption ratio of NaA zeolite monolithic adsorbents synthesized with different crystallization time
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3.2 Performance of NaA zeolite monolithic adsorbent 3.2.1 Static adsorption test
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The static adsorption curves of NaA monolithic adsorbents synthesized by different synthesis methods at 25 oC and 60% RH are shown in Fig. 5. The NaA zeolite monolithic
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adsorbent synthesized by microwave heating had a higher saturated adsorption ratio (23.3%) than that by impregnation method (20.9%). Besides, the former had a higher early adsorption rate than the later,which means the former is more fit for the adsorptive rotary dehumidification system. A possible reason is that the NaA zeolite monolithic adsorbent with smaller particle size obtained by microwave heating has larger specific surface area and shortens the distance among the pores, compared with industrial molecular sieve monolith with larger particle size produced by impregnation method. In addition, microwave synthesis may result in higher zeolite content in
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the matrix due to no addition of inorganic adhesive.
Fig. 5 Static Adsorption curves of NaA zeolite monolithic adsorbents with different
3.2.2 TPD analysis
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preparing methods
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The temperature programmed desorption (TPD) curves of NaA zeolite monolithic adsorbents obtained by different methods at different heating rates (β) are shown in Fig. 6. Based
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on Kissinger equation and the desorption temperature peak (Tp) of TPD curves at different β, a straight-line ln(RTP2/β) vs. 1/Tp with a slope equal to the ratio of desorption activation energy (Ed) and R can be obtained. The calculated Ed of NaA zeolite monolithic adsorbent prepared by impregnation method and microwave heating are 81.57 and 64.63 kJ⋅ mol-1, respectively. It can be seen that NaA monolithic adsorbent synthesized by microwave heating has relatively low desorption temperature and desorption activated energy, which is much more suitable for rotary desiccant dehumidification system.
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Fig. 6 TPD curves of NaA zeolite monolithic adsorbents prepared with different methods at
Conclusions
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different heating rate
This paper described a novel in situ microwave hydrothermal synthesis technique for the NaA zeolite monolithic adsorbent on honeycomb ceramic matrix. The synthesis process, the morphology and the adsorption/desorption performance of the monolithic adsorbent were
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investigated systematically. The XRD patterns indicated that seeding coating can induce the formation of pure NaA zeolite on the ceramic support and preventing NaA crystals from crystalline transformation, and the optimal synthesis process by microwave hydrothermal
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treatment was microwave time of 45 min and reaction temperature of 160 oC. SEM photos
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revealed that NaA zeolite synthesized by microwave heating had a uniform distribution and small particle size of about 0.9µm with cubic crystal form. The results of static adsorption showed that NaA monolithic adsorbent prepared by microwave irradiation had a faster early adsorption rate and higher saturated adsorption ratio for water vapor (23.3%) than that by impregnation method (20.9%). The results of TPD analysis also exhibited that NaA monolith obtained by microwave method had a lower desorption activated energy (64.63 kJ mol-1) than that by impregnation method (81.57 kJ mol-1), which means that novel in situ microwave
ACCEPTED MANUSCRIPT synthesized NaA zeolite monolithic adsorbent is much more suitable for rotary desiccant dehumidification system. Acknowledgments This work was supported by National Natural Science Foundation
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of China (No. 51536003, No.21471059).
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zeolite membranes, Micropor. Mesopor. Mater. 120 (2009) 170–176.
[18] M. Pera-Titus, R. Mallada, J. Llorens, F. Cunill, J. Santamaria, Preparation of innerside tubular zeolite NaA membranes in a semi-continuous synthesis system, J.Membr. Sci. 278 (2006) 401–409.
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[19] M. Pera-Titus, J. Llorens, F. Cunill, R. Mallada, J. Santamaria, Preparation of zeolite NaA membranes on the inner side of tubular supports by means of a controlled seeding technique, Catal. Today 104 (2005) 281–287.
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[20] Kondo M, Komori M, Kita H, et al. Tubular-type pervaporation module with
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zeolite NaA membrane[J]. Journal of Membrane Science, 1997, 133(1): 133-141. [21] Sterte J, Mintova S, Zhang G, et al. Thin molecular sieve films on noble metal substrates[J]. Zeolites, 1997, 18(5): 387-390. [22] Sano T, Yanagishita H, Kiyozumi Y, et al. Separation of ethanol/water mixture by silicalite membrane on pervaporation[J]. Journal of membrane science, 1994, 95(3): 221-228. [23]Lai R, Gavalas G R. Surface seeding in ZSM-5 membrane preparation[J].
ACCEPTED MANUSCRIPT Industrial & engineering chemistry research, 1998, 37(11): 4275-4283. [24]Boudreau L C, Kuck J A, Tsapatsis M. Deposition of oriented zeolite A films: in situ and secondary growth[J]. Journal of membrane science, 1999, 152(1): 41-59.
zeolite membrane, Sep. Purif. Technol. 25 (2001) 475–485.
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[25]X.C. Xu, W.S. Yang, J. Liu, L.W. Lin, Synthesis and perfection evaluation of NaA
[26] Y.S. Li, H.L. Chen, J. Liu, W.S. Yang, Microwave synthesis of LTA zeolite
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membranes without seeding, J. Membr. Sci. 277 (2006) 230–239.
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[27] Z.L. Cheng, Z. Liu, H.L. Wan, Microwave-heating synthesis and gas separation performance of NaA zeolite membrane, Chin. J. Chem. 23 (2005) 28–31. [28] Z.L. Cheng, Z.S. Chao, H.L. Wan, Synthesis of compact NaA zeolite membrane by microwave heating method, Chin. Chem. Lett. 14 (2003) 874–876.
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[29] Madhusoodana C D, Das R N, Kameshima Y, et al. Microwave-assisted hydrothermal synthesis of zeolite films on ceramic supports[J]. Journal of materials science, 2006, 41(5): 1481-1487.
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[30]Huang A, Lin Y S, Yang W. Synthesis and properties of A-type zeolite membranes
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by secondary growth method with vacuum seeding[J]. Journal of membrane science, 2004, 245(1): 41-51.
[31] Huang A, Yang W. Hydrothermal synthesis of NaA zeolite membrane together with microwave heating and conventional heating[J]. Materials Letters, 2007, 61(29): 5129-5132. [32] Li Y, Yang W. Microwave synthesis of zeolite membranes: a review[J]. Journal of Membrane Science, 2008, 316(1): 3-17.
ACCEPTED MANUSCRIPT [33] X.C. Xu, W.S. Yang, J. Liu, L.W. Lin, Synthesis of a high-permeance NaA zeolite membrane by microwave heating, Adv. Mater. 12 (2000) 195–196. [34] C.D. Madhusoodana, R.N. Das, Y. Kameshima, K. Okada, Preparation of ceramic
crystallization, Sci. Eng. Ceram. Iii 317–318 (2006) 697–700.
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honeycomb filter supported zeolite membrane modules by microwave-assisted in situ
[35] Y.S. Li, J. Liu, H.L. Chen, W.S. Yang, L.W. Lin, Preparation of LTA zeolite
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membranes with few non-zeolite pores using microwave heating, Chin. J. Catal. 27
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(2006) 544–546.
ACCEPTED MANUSCRIPT Highlights: 1. Novel in situ microwave hydrothermal synthesis strategy for NaA monolithic adsorbent. 2. Small particle size and uniform distribution.
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3. High saturated adsorption ratio and early adsorption rate.
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4. Low desorption activation energy.