Fluoride-free hydrothermal synthesis of nanosized Sn-Beta zeolite via interzeolite transformation for Baeyer-Villiger oxidation

Journal Pre-proof Fluoride-free hydrothermal synthesis of nanosized Sn-Beta zeolite via interzeolite transformation for Baeyer-Villiger oxidation Zhiguo Zhu, Haikuo Ma, Mingtong Li, Ting Su, Hongying Lu¨

PII:

S0926-860X(19)30525-3

DOI:

https://doi.org/10.1016/j.apcata.2019.117370

Reference:

APCATA 117370

To appear in:

Applied Catalysis A, General

Received Date:

12 October 2019

Revised Date:

29 November 2019

Accepted Date:

30 November 2019

Please cite this article as: Zhu Z, Ma H, Li M, Su T, Lu¨ H, Fluoride-free hydrothermal synthesis of nanosized Sn-Beta zeolite via interzeolite transformation for Baeyer-Villiger oxidation, Applied Catalysis A, General (2019), doi: https://doi.org/10.1016/j.apcata.2019.117370

This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. 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. © 2019 Published by Elsevier.

Fluoride-free hydrothermal synthesis of nanosized Sn-Beta zeolite via interzeolite transformation for Baeyer-Villiger oxidation Zhiguo Zhu,*a Haikuo Ma,a Mingtong Li,b Ting Su,a Hongying Lü*a

Corresponding Address: a

Green Chemistry Centre, College of Chemistry and Chemical Engineering, Yantai University,

ro of

30 Qingquan Road, Yantai 264005, Shandong, China b

School of Environmental and Material Engineering, Yantai University, 30 Qingquan Road,

-p

Yantai 264005, Shandong, China

re

E-mail address: [email protected] (H. Lü); [email protected] (Z. Zhu)

lP

Graphical abstract

The nanosize structured Sn-Beta zeolite is hydrothermally synthesized via interzeolite

na

transformation from siliceous FAU zeolite with steam-assisted conversion under environmentally unfriendly fluoride-free conditions. Such Sn-Beta zeolite demonstrates unique

Jo

TBHP.

ur

catalytic activity in the Baeyer-Villiger oxidation of ketones in particular with bulky oxidant of

1

Research Highlights 

Sn-Beta zeolite is simply hydrothermally synthesized via interzeolite transformation.



This direct synthesis is not assisted by environmentally-unfriendly fluoride.



The obtained Sn-Beta zeolite possesses high isolated Sn contents and smallest crystal sizes. Thus Sn-Beta demonstrates unique Baeyer-Villiger oxidation performances.

ro of



ABSTRACT

-p

Sn-containing Beta (Sn-Beta) zeolite is extensively applied in industrially-relevant reactions as a highly active and robust Lewis acid heterogeneous catalyst. Nonetheless, environmentally-

re

unfriendly fluoride is generally required to the directly hydrothermal synthesis of Sn-Beta. In

lP

this work, an innovative strategy of interzeolite transformation with steam-assisted conversion is provided to directly synthesize Sn-Beta zeolite in the absence of fluoride. Silica source of FAU

na

and steam-assisted conversion were two necessary factors for the successful synthesis of Sn-Beta zeolite. It was found that highly crystallized Sn-Beta zeolite with isolated framework Sn ions was

ur

hydrothermally synthesized via degradation of siliceous FAU zeolite and recrystallization of

Jo

degraded silicate species. As far as we know, the crystal of Sn-Beta in this work was minimum in size among all present directly hydrothermal synthesized ones. More importantly, the Sn contents in Sn-Beta could achieved to 2.39 wt % (Si/Sn = 81), breaking through the Sn content restriction of conventional fluoride-mediated method. In addition, the hydrophobicity of this resultant Sn-Beta zeolite was slightly inferior to Sn-Beta-F obtained via traditional fluorideassisted route. Whereas the smaller crystal size of this Sn-Beta gave rise to relatively good 2

diffusion performance for organics, which made it reveal high activities in the Baeyer-Villiger oxidant of ketones in particular employing bulky tert-butyl hydroperoxide as the oxidant. The current strategy provides an alternative and environmentally-friendly method for the hydrothermal synthesis of Sn-Beta without the assistance of fluoride and alkali metal ions, which can guide further development in metallosilicates crystal engineering in terms of greenization.

ro of

Keywords: Sn-Beta zeolite, Fluoride-free, FAU zeolite, Interzeolite transformation, BaeyerVilliger oxidation

-p

1. Introduction

Heteroatom-containing zeolites, containing isolated metal atoms such as Sn [1], Ti [2], Hf [3],

re

Nb [4], and Zr [5] isomorphously substituted in the silicious framework, have gained significant

lP

attention as they are extensively applied in the production of fine chemicals. As a classic representative of metallosilicates, Sn-Beta, with the *BEA topology structure of 3-dimension 12-

na

membered ring, possesses unique Lewis acidity even in the aqueous phase likely resulting from hydrophobic framework environment [6]. Combined with the particular feature of selectively

ur

active the carbonyl group, Sn-Beta zeolite catalyst shows unique activities in various reaction

Jo

processes including the Baeyer–Villiger (B–V) oxidation [1], the Meerwein–Pondorf–VerleyOppenauer redox [7], C–C coupling reactions [8], the Diels–Alder reaction [9], the transformation of xylose to xylulose [10], isomerization-esterification reaction [11], the formation of 5-(hydroxymethyl)furfural (5-HMF) [12,13], and the isomerization of glucose [14,15]. Recently, it was found that Sn-Beta zeolite was also capable to efficiently catalyze ringopening hydration of epoxide [16], aldol reaction [5], ethanol dehydration [17], aminolysis of 3

epoxide [18]. It is believed that the exploration of new applications for Sn-Beta is still on the way. Up to now, although a large number of Sn-related materials have been reported [19–25], Sn-Beta zeolite is still the state-of-the-art Lewis acid solid catalyst and is usually considered to be a benchmark material primarily due to its open pore systems, relatively stable framework structure as well unique Lewis acidity. Thus, the success synthesis of Sn-Beta is a milestone in the design of large pore zeolite catalyst, which will be groundbreaking in the development of

ro of

metallosilicates.

Although Sn-Beta zeolite bears the potential for industrialization, unlike titanosilicates, it suffered from the difficulty in Sn atom isomorphously substituted in the siliceous framework

-p

probably due to the relatively larger ions size (0.71 Å) and T-O bond length (1.912 Å) of Sn4+

re

than these (0.68 Å and 1.892 Å, respectively) of Ti4+ and the incompatible hydrolysis rate of the silica source to the Sn source [26]. Sn-Beta zeolite was generally hydrothermally synthesized

lP

with the assistance of fluoride and/or alkali metal ions [1,26]. The traditional synthesis route for

na

Sn-Beta in the presence of fluoride caused environment concerns and gived an upper-limited isolated Sn content (generally Si/Sn molar ratio > 100) due to the retarded effect of Sn4+ for this

ur

hydrothermal synthesis [1,26–34]. Moreover, the utilization of fluoride in the synthesis resulted in large crystals with microsized magnitude and a long synthetic time (> 14 d) because of its

Jo

difficulty in spontaneous nucleation in the primary synthesis stage [1]. On the other hand, the synthesis process for alkali metal ions mediated Sn-Beta was inevitable to perform ion-exchange with ammonium ions for several times to preserve the framework structure, resulting in a large amount of waste water [26,27]. Considering these existing issues, much endeavour in terms of directly hydrothermal synthesis 4

and post-synthesis methods had been made to improve the synthesis process of Sn-Beta. The highly crystalline Sn-Beta was found to be synthesized within only 2 d through uniformly distributing seeds in the synthetic gels [28]. Zhang et al. decreased the synthesis time to 24 h for Sn-Beta with the molar Si/Sn ratio of 100 via gel conversion method [29]. Subsequently, the synthetic influence factors were also systematically investigated by the same group [30]. This gel conversion method was also capable to give Sn-Beta in an alkali metal ions medium, while

ro of

the poor hydrophobic nature led to lower catalytic performances in isomerization of glucose to fructose in comparison with conventional fluoride-mediated Sn-Beta [26]. Takayuki et al. synthesized Sn-Beta zeolite with a high Sn content of 3.17 wt % (Si/Sn = 60) employing a Si-Sn

-p

mixed oxide composite as the starting material [31]. Very recently, our group reported that the

re

synthesis of Sn-Beta was achieved by interzeolite transformation from all-silica MWW silicate within 3 d, giving a high Sn content (Si/Sn = 63) [32]. Inspired by this innovative idea, highly

lP

active Sn-Beta was further hydrothermally constructed utilizing the highly dealuminated

na

siliceous Beta zeolite as silica source, which possessed higher isolated Sn contents and hydrophobicity (based on (SiO)3SiOH contents in 29Si MAS NMR and adsorption water amounts

ur

in thermogravimetric analysis) than traditional fluoride-mediated Sn-Beta zeolite [33]. Followed by this, a complicated and commercially unavailable organic structure-directing agent (OSDA)

Jo

of N-cyclohexyl-N,N-dimethylcyclohexanaminium hydroxide was tried to prepare Sn-Beta in the presence of seeds and alkali metal ions, which showed relatively good catalytic performances in the Baeyer-Villiger oxidation and isomerization-esterification [27]. Xiong et al. made use of the aerosol-seed-assisted method for the preparation of Sn-Beta to lower the amount of fluoride and template [34]. From these reported literatures, we know that the utilization of fluoride and/or 5

alkali metal ions are inevitable in the present synthesis of Sn-Beta zeolite. Post-synthesis method, involving the formation of silanol nests by removing ions in the framework and thereafter insertion of Sn ions into these sites, could be adopted to synthesize SnBeta under alkali metal ions and fluoride free conditions. Depending on the existing states of Sn source, this approach is divided into three specific subclasses, that is, gas-solid isomorphous substitution [35,36], liquid-solid grafting method [37,38], and solid-state ion-exchange method

ro of

[39,40]. However, it is nearly impossible to make the defect sites completely closed through the insertion of framework Sn because the Sn sources were low mobility and the type as well as contents of silanol nests generated during the acid treatment process could not be precisely

-p

modulated. In addition, yielding poor surface nature, forming Sn oxide species, and requiring

re

dangerous operations were also observed for the post-synthesis method [35–41]. Therefore, further development of an innovative strategy for the directly hydrothermal synthesis of Sn-Beta

lP

zeolite in an alkali metal ions and fluoride free medium is intensively desired but still a great

na

challenge.

The failure of direct synthesis of Sn-Beta zeolite was mainly attributed to the difficulties in the

ur

preparation of all-silica Beta zeolite without the assistance of alkali metal ions and/or fluoride and the isomorphous substitution of Sn ions in the zeolitic framework. Interzeolite

Jo

transformations have attracted great interest as they open up a new idea for the rapid zeolite synthesis even without OSDAs [42,43]. Previously, targeted zeolites are generally aluminosilicate versions [44,45]. Very recently, our group reported that all-silica Beta zeolite was directly hydrothermal synthesized via this strategy under fluoride and alkali metal ions free conditions [46]. 6

Based on previous studies by our group, in this manuscript, we provide a novel strategy of interzeolite transformation with steam-assisted conversion to directly synthesize nanosized SnBeta zeolite without the aid of fluoride and alkali metal ions, as graphically illustrated in Scheme 1. Herein, the highly crystalline Sn-Beta zeolite with crystal size in nanometer magnitude (50– 150 nm) was smoothly synthesized via degradation of siliceous FAU zeolite and recrystallization of degraded silicate species. The crystallization process and textural properties such as Sn4+

ro of

coordination state and crystal surface nature of the resultant Sn-Beta were systematically investigated. The catalytic activity of Sn-Beta zeolite catalyst was evaluated in comparison with that of the classic fluoride-mediated one in the Baeyer–Villiger oxidation of ketones employing

-p

aqueous H2O2 or bulky tert-butyl hydroperoxide (TBHP) as oxidants.

re

2. Experimental section 2.1. Materials

lP

The following chemicals were used as provided without further purification: Nitric acid

na

(HNO3, 65 %, Sinopharm Chemical Reagent Co., Ltd), tetraethylammonium hydroxide (TEAOH, 25 %, TCI), tetraethylammonium bromide (TEABr, 98 %, Macklin), ammonium fluoride (NH4F,

ur

96 %, Sinopharm Chemical Reagent Co., Ltd), Stannic chloride hydrated (SnCl4·5H2O, 99 %, Aladdin), tetraethoxysilane (TEOS, 100 %, TCI), 2-adamantanone (98 %, Macklin),

Jo

chlorobenzene (99 %, Macklin), benzonitrile (99 %, Macklin), tert-butyl hydroperoxide (TBHP in water, 70 %, Macklin), tert-butyl hydroperoxide (TBHP in decane, 5.5 M, Sigma-Aldrich). 2.2. Preparation of siliceous FAU zeolite and Beta seeds Commercially available H-type USY (Si/Al = ca. 6, particle size of 0.5–1 μm confirmed by Fig. S1) and Beta (Si/Al = ca. 11, 60–130 nm shown in Fig. S2) zeolites, provided by Shanghai 7

Xinnian Petrochemical Additives Co., Ltd., were highly dealuminated by acid treatment to extract Al species in zeolites, giving rise to nearly siliceous FAU and Beta zeolites, respectively. With respect to USY zeolite, it was refluxed in a 6 M HNO3 solution with a liquid-to-solid of 30 based on weight at 408 K for 12 h under vigorously stirring. The product was obtained by filtration, dried at 383 K for 3 h, and then calcined at 873 K for 6 h with the heating rate and gas flow rate per mass catalyst of 2 oC min−1 and 20 mL min−1, respectively. Subsequently, this entire

ro of

dealumination process was repeated for two more times. The resultant product was denoted as USY-DA with Si/Al molar ratio of 516, detected by ICP. USY-DA would be used as the silica source for synthesizing Sn-Beta.

-p

The dealuminated process of Beta zeolite was similar to that of USY. Note that this acid

re

treatment was processed only once. The obtained sample was designated as Beta-DA with Si/Al molar ratio of above 1900, acting as zeolite seeds for the synthesis of the following Sn-Beta

lP

zeolite if added. Additionally, as can be seen from Figs. S1–S4, the particle size and morphology

na

for the two zeolite materials were nearly not changed during the dealumination process, at the same time the corresponding framework structures were all preserved.

ur

2.3. Direct synthesis of Sn-Beta by interzeolite conversion Sn-Beta zeolite was hydrothermally synthesized employing USY-DA as the starting material

Jo

with the steam-assisted conversion method. In a typical synthesis, USY-DA silicate and Beta-DA seeds (10 wt % with respect to USY-DA), were mixed into the solution of TEAOH under stirring at room temperature for 30 min. Then SnCl45H2O was added into the mixture, followed by magnetically stirring for 1 h at room temperature. The ultima molar composition of the gel was SiO2 : x SnO2 : 0.5 TEAOH : 8.0 H2O, where x indicates the Sn/Si molar ratio in the gel. 8

Subsequently, the water in the gel was evaporated at 353 K for about 12 h, achieving a dry gel state (H2O/SiO2 molar ratio of about 0.8). The dry gel was ground into fine powder, shifted into a small Teflon cup of about 25 mL, and then the cup was put into a 100 mL Teflon-lined stainless steel autoclave. A small amount of water (0.25 g deionized water per mass dry gel) was further introduced into the lining outside the cup to prevent water directly contacting with dry gel. And then the autoclave was head-up transferred into an oven at 413 K for crystallization. After

ro of

crystallization, the as-synthesized sample was recovered by filtration, desiccated at 353 K for 8 h, and then calcined at 873 K for 6 h with the heating rate and gas flow rate per mass catalyst of 2 oC min−1 and 20 mL min−1, respectively, to remove organics occluded in the zeolitic pores. The

-p

resultant product was designated as Sn-Beta-SAC-m, where m is equal to the reciprocal of x.

re

Siliceous Beta (denoted as Beta-SAC) was also synthesized without adding Sn source into synthetic systems.

lP

The synthesis of traditional fluoride-mediated Sn-Beta (denoted as Sn-Beta-F-n, where n

na

indicates the Si/Sn molar ratio in the gel), was also performed according to literature reported previously [1]. Note that this Sn-Beta-F was synthesized with the addition of Beta-DA seeds (10

ur

wt % with respect to SiO2) employing benign ammonium fluoride as a fluorine source. 2.4. Characterizations

Jo

The X-ray diffraction (XRD) patterns were collected on a X-ray diffractometer of Rigaku

Ultima IV type with a Cu-Kα radiation (λ=1.5405 Å) at voltage and electric current of 35 kV and 25 mA, respectively. Scanning electron micrographs (SEM) were undertaken from Hitachi S4800 microscopy. Transmission electron microscopes (TEM) were performed on a JEOL-JEM2100 microscope. The adsorption isotherms of N2 and water vapor were determined through a 9

BELSORP-MAX equipment connected with a precise sensor for low-pressure measurement at 77 K for N2 and at 298 K for water. The samples were activated at 573 K at least for 6 h under vacuum prior to measurement. The Si, Al, and Sn contents were obtained with inductively coupled plasma (ICP) technology using an atomic emission spectrometer of Thermo IRIS Intrepid II XSP type after solubilizing each sample in a HF solution. Once cooling the calcined samples down to the temperature below 373 K, UV–visible (UV–vis) diffuse reflectance spectra

ro of

were performed on a Shimadzu UV-2700 spectrophotometer with the reference of barium sulfate. FT-IR spectra were carried out on a Nicolet Nexus 670 spectrometer with a resolution of 4 cm−1 in the absorbance mode. For the pyridine adsorption spectra, after the self-supported wafer of

-p

measured sample was fabricated by compression, it was then fixed in a quartz cell sealed with

re

CaF2 windows. The cell was connected with a vacuum system. The pyridine adsorption was achieved through exposing the wafer to the pyridine vapor at room temperature for 1 h after the

lP

wafer was dehydrated at the temperature of 723 K for 2 h. The pyridine FT-IR spectra were

na

collected for 1 h with the increase of the desorption temperature from 298 to 523 K. 29Si MAS NMR solid-state spectra were collected on a VARIAN VNMRS-400WB NMR spectrometer with

ur

a frequency of 79.43 MHz, a recycling delay of 60 s, a spinning rate of 3 KHz. The [(CH3)3SiO]8SiO12 was used as the chemical shift reference.

Jo

2.5. Catalytic reactions

The catalytic activity was assessed in a 25 mL flask connected to a water condenser, which

was fixed in a water bath, under magnetically stirring. In a typical process, 50 mg of catalyst, 2 mmol of 2-adamantanone, 4 mmol of H2O2 (65 wt %) or TBHP (70 wt % in water or 5.5 M in decane), 10 mL of chlorobenzene, and 0.5 g of benzonitrile (as a GC internal standard) were 10

mixed in the flask and immediately transferred in water bath at 363 K for different times. Then the mixture was cooled down under the ice bath conditions, thereafter centrifugation to remove the heterogeneous solid catalyst in the system was carried out, and the reaction mixture was analyzed by a Shimadzu GC-14B gas chromatograph (FID detector) equipped with a 30 m DB1 capillary column to determine the conversion and product selectivity. The corresponding organics in the reaction system were identified by a GC-MS instrument of Agilent-

ro of

6890GC/5973MS type. 3. Results and discussion

3.1. Synthesis of Sn-Beta zeolite via interzeolite transformation

-p

Sn-Beta-SAC zeolite was hydrothermally synthesized with the steam-assisted conversion

re

using highly dealuminated FAU-type silicate (Si/Al > 500) and Beta-DA (Si/Al > 1900, 10 wt % with respect to silica source) as silica source and crystallization seeds, respectively, as graphically

lP

illustrated in Scheme 1. For the sake of obtaining highly crystallized Sn-Beta-SAC zeolites as

na

well as decreasing synthesis costs, the synthesis parameters of TEAOH/SiO2 ratio and the substitution contents of TEABr to TEAOH were investigated at 413 K for 3 d. As show in Fig.

ur

S5A, with the TEAOH/SiO2 ratio decreasing from 0.5 to 0.4, the crystallinity of Sn-Beta-SAC sharply decrease. When the TEAOH/SiO2 ratio was below 0.4, the crystallized products were

Jo

amorphous phase, suggesting that the structure-directing agent of TEAOH was crucial during the synthesis of Sn-Beta-SAC. Thus, the TEAOH/SiO2 ratio of 0.5 was chosen as the optimal content in the following experiments. Furthermore, with the purpose to decrease synthesis costs, organic TEABr was utilized to substitute costly OSDA of TEAOH (Fig. S5B). The synthesis was performed by keeping the sum of TEABr and TEAOH molar contents constant ((TEABr + 11

TEAOH)/SiO2 = 0.5). However, it was found that once TEABr was added in the starting gels, the highly crystallized Sn-Beta-SAC could not be obtained, indicating the suitable alkaline environment derived from TEAOH was beneficial to the crystallization of Sn-Beta-SAC zeolite. Hence, the attempt of substitution of TEABr to TEAOH failed. As far as we know, fluoride and/or alkali metal ions were necessary for the hydrothermal synthesis of Sn-Beta zeolite [1,26–30]. Beyond expectation, in this work, Sn-Beta-SAC was successfully hydrothermally synthesized

ro of

under fluoride and alkali metal ions free conditions using siliceous FAU zeolite as silica source by steam-assisted conversion. The detailed investigation would be provided below.

The crystallization process of Sn-Beta-SAC was tracked by XRD characterization. As

-p

demonstrated in Fig. 1Aa, the XRD pattern of initial sample gived series of peaks at 6.3, 10.2,

re

12.1, 15.9, and 23.9o, which was typical characteristic signals for FAU-type topology structure [25,47]. Very weak diffraction peaks corresponding to *BEA structure were observed due to the

lP

small amount of Beta-DA in the initial sample. The FAU zeolite was recrystallized by steam-

na

assisted conversion in the initial gels of 1.0 SiO2 : 0.5 TEAOH : 0.083 SnCl4 with adding 10 wt % Beta-DA seeds at 413 K. The signal peaks corresponding to pristine USY-DA completely

ur

disappeared after the hydrothermal treatment at 413 K for 0.5 d, giving rise to the products of amorphous phase and a low solid yield of 36 wt % (Figs. 1Ab and 1Bb). These results indicated

Jo

that the FAU-type structure was fully collapsed at the beginning of 0.5 d. Subsequently, these dissolved silicate species were reconstructed with the assistance of organic TEAOH and BetaDA seeds. Both the intensities of Bragg diffraction peaks at 7.8 and 22.6o assigned to *BEA framework structure and the solid product yield gradually increased [46]. At the treatment of 3 d, well-crystallized Sn-Beta-SAC was obtained in the absence of any impurity phase (Fig. 1Ae) 12

and at the same time its solid yield was significantly enhanced to 97.3 wt % (Fig. 1Be). Further extending the synthesis time to 8 d, both the crystallinity and solid yield were almost not changed, implying that Sn-Beta-SAC-120 zeolite was fully crystallized via interzeolite transformation from siliceous FAU zeolite without the aid of fluoride and alkali metal ions at 413 K for 3 d. FT-IR spectroscopy was also employed to record the structural evolution of Sn-Beta-SAC-120. With purpose to eliminate the effects of TEA+ in the as-synthesized products, calcination was

ro of

performed for the as-made products prior to test via FT-IR technique. As shown in Fig. 2, at the very beginning, the FT-IR spectrum showed two characteristic bands at 1078 and 1208 cm−1, attributed to the T−O asymmetric stretch of internal linkages and of external linkages,

-p

respectively [48]. Although a certain amount of Beta-DA seeds was introduced into the initial

re

gels, no evident FT-IR bands corresponding to *BEA zeolites was observed, probably because the content was lower than measurement limit of FT-IR instrument and/or the corresponding peak

lP

intensities were too feeble in comparison with these for pristine USY-DA. After heat treatment

na

for 0.5 d, these bands nearly disappeared compared to USY-DA, indicating the silicate species existed in the form of long-range disorder state. Subsequently, what beyond our expectation was

ur

that with the crystallized time prolonging, characteristic bands at 572, 1101, 1231 cm−1, closely associated with 5 membered ring-rich units, T−O asymmetric stretch of internal linkages and of

Jo

external linkages in Beta zeolite, respectively [49], became narrow and their intensities gradually increased. This experiment result suggested that the species in the crystallized products were gradually transformed from long-range disorder state to uniform and rigid condition. When prolonging the synthesis time to 3 d, the hydrothermal products, identified as Beta zeolite by XRD in Fig. 1A, exhibited the characteristic bands of Beta zeolite at 521, 572, 624, 1101, and 13

1231 cm−1 [49,50]. This was also confirmed by the fact that Sn-Beta-SAC-120 and Sn-Beta-F120 possessed similar FT-IR spectra in the framework vibration region (Fig. S6). Additionally, further extending the crystallized time, the IR spectrum almost remained the same. These facts indicated that the Beta framework structure was constructed within 3 d, in good agreement with XRD results in Fig. 1. The size and morphology of the solid products collected after hydrothermal treatment for

ro of

different periods were investigated by SEM. As can be seen from Fig. 3, a number of grooves and voids were observed in the parent USY-DA zeolite, resulting from the steaming process in industrial level to prepare USY zeolite, which was in good consistent with the previous reports

-p

[47]. Upon heat treatment for 0.5 d, the morphology of USY-DA was transformed to bulky

re

aggregation of amorphous phase confirmed by XRD and FT-IR, suggesting that the pristine USYDA was completely dissolved during this periods. After crystallized time of 1 d, sponge-like

lP

samples were observed in the whole region. With the crystallization proceeding (2 d), some

na

nanoparticles began to appear and obvious ravine existed on the aggregates, indicated that the degraded siliceous species were employed as the nutrition for crystal growth of Sn-Beta-SAC-

ur

120 zeolite. At 3 d, only isolated grain-like nanoparticles of 50–150 nm in diameter were observed. Further extending the synthesis time to 8 d, no obvious change in size and morphology

Jo

was noticed. These recorded results were in accordance with these of XRD and FT-IR characterizations.

As revealed in Figs. 4b and S7, Sn-Beta-F-120 hydrothermally synthesized in the fluoride medium possessed the crystals of above 1 μm, which was one order of magnitude larger than SnBeta-SAC-120 prepared by interzeolite transformation (50–150 nm). This result was in good 14

consistent with the observation of low-intense and broad diffraction peaks in the XRD patterns (Fig. S8). The nanosized crystals with a diameter of 50–150 nm were also observed in TEM image, in accordance with the SEM (Fig. 4c). What’s more, the TEM image of Sn-Beta-SAC120 crystals shown clear lattice fringes, further proving its high crystallinity. To illustrate the specific structural connection between FAU- and *BEA-type framework structures, silicalite-1 and all-silica NON were also employed as silica source to attempt this

ro of

hydrothermal synthesis under the same conditions. As shown in Fig. 5, MFI and NON structure were not capable to be transformed to *BEA-type structure under present conditions, implying the close-knit framework relationship between FAU- and *BEA-type topology. Additionally,

-p

when amorphous silica source such as tetraethoxysilane (TEOS) was tried in this synthesis, only

re

amorphous phase was obtained (Fig. S9). On the other hand, it is a long time (generally more than 20 d) that it required for the synthesis of Sn-Beta zeolite using the traditional method [1].

lP

Nonetheless, the well-crystallized Sn-Beta-SAC-120 with a molar Si/Sn ratio of 120 was

na

achieved by interzeolite transformation within only 3 d. The smooth and fast transformation from FAU- to *BEA-type zeolite could be attributed to their structural similarity [51]. The synthesis

ur

of Sn-Beta-SAC was also performed without adding Beta-DA seeds. As shown in Fig. S10A, SnBeta-SAC-120 was also successfully hydrothermally synthesized within 13 d. Compared to the

Jo

addition of zeolite seeds (3 d), the crystallized rate was quite slow, indicating that addition of Beta-DA seeds could accelerate crystallized process of Sn-Beta-SAC. Thus, conclusion could be made that Sn-Beta-SAC was capable to be well-crystallized no matter whether Beta-DA seeds were added in the synthesis systems or not and Beta-DA was only a crystallization promoter, which was similar to the conventional hydrothermal synthesis of Sn-Beta-F in a fluoride medium 15

[28]. These results intensively indicated that the structural relatedness between parent FAU zeolite and desired *BEA zeolite was an indispensable and crucial factor for the formation of final crystallized zeolite crystal (i.e., Sn-Beta-SAC zeolite). At this point, it could be concluded that Sn-Beta-SAC zeolite was readily hydrothermally synthesized through the degradation of pristine USY-DA and recrystallized of locally ordered silicate species to *BEA-type phase under present synthesis conditions. It is important to

ro of

highlight that this hydrothermal synthesis process was carried out without the assistance of fluoride and alkali metal ions, which was significantly different from previous reported synthesis methods [1,26,27]. Normally, Sn-Beta zeolite prepared by hydrothermal synthesis approach

-p

possessed large crystal size (above 500 nm). Surprisingly, Sn-Beta-SAC hydrothermally

re

synthesized by interzeolite transformation was composed of nanosized crystals of 50–150 nm in diameter. As far as we know, the crystal of Sn-Beta-SAC in this work was minimum in size

lP

among all present directly hydrothermal synthesized ones.

na

3.2. Textural properties of Sn-Beta zeolites

As for heteroatom-containing zeolites, their catalytic active sites are usually originated from

ur

isolated heteroatom in the zeolitic framework [2,11]. Hence, the heteroatom contents are a remarkable element for their catalytic application. Herein, the range of Sn contents in Sn-Beta-

Jo

SAC zeolites prepared by interzeolite transformation route was investigated. As illustrated in Fig. S10B and Table 1, highly crystalline Sn-Beta-SAC zeolite with molar Si/Sn ratio of 80–200 was successfully synthesized and no other impurity phase was found as coexistent substance. The full crystallization time of Sn-Beta zeolite was greatly influenced by the Sn contents in the initial gels. When a very small amount of Sn was introduced in the initial gels (Si/Sn = 200), the fully 16

crystallized time for fluoride-assisted method and interzeolite transformation was 6 and 1 d, respectively. With an increased Sn amounts in the gels (Si/Sn = 120), the synthesis times were also extended for the both methods (conventional method, 21 d; interzeolite transformation, 3 d). From these results, it could be inferred that adding Sn species into synthesis gels retarded the construction of Sn-Beta zeolite framework, which was similar to previous reports [32,33]. What’s more, Sn-Beta-SAC zeolite prepared via interzeolite transformation possessed much faster

ro of

crystallized rate in comparison to that hydrothermally synthesized by fluoride-assisted route. More importantly, Sn-Beta-F zeolite with a Si/Sn molar ratio low than 100 in the synthesis gels could not be crystallized by conventional fluoride-assisted method, in accordance with previous

-p

literatures [1]. It was for Sn-Beta-SAC-80 with a high Sn amount of 2.39 wt % (Si/Sn = 81) that

re

the synthesis process of interzeolite transformation proceeded successfully. This may be due to the promotion of degraded locally ordered silicate species derived from pristine USY-DA for

lP

zeolitic nucleation and crystal growth. The similar phenomenon had been reported previously by

na

our group [32]. Further increasing Sn contents (Si/Sn < 80) in the synthesis gels, Beta phase could not be achieved via interzeolite transformation, even prolonging the hydrothermal

ur

treatment time.

The textural properties of Sn-Beta with different Sn contents were shown in Table 1. The Si/Sn

Jo

molar ratio in the initial gel was about equal to that in the ultimate product, indicative of high utilization efficiency of Sn source. The pore volume and specific surface area of Sn-Beta samples were calculated from N2 adsorption-desorption isotherms at 77 K in Fig. S11. The micropore volume for all Sn-Beta with *BEA structure was about 0.2 cm3 g–1, further confirming the wellcrystallized structure as evidenced by XRD in Fig. S10B. The total surface area (600–635 m2 g– 17

1

) and external specific surface area (150–170 m2 g–1) of Sn-Beta-SAC samples prepared by

interzeolite transformation were predictably superior to these (total surface area, 500–550 m2 g– 1

; external specific surface area, 60–75 m2 g–1) of Sn-Beta-F synthesized in a fluoride medium

because of much smaller crystals in size for Sn-Beta-SAC zeolites, as shown in Figs. 3 and 4. 3.3. Hydrophilicity/hydrophobicity and Sn coordination Heteroatom-containing zeolites, possessing metal ions isomorphously substituted in the

ro of

zeolitic framework, are widely applied in series of industrially-relevant processes as heterogeneous solid catalysts [1–5]. In the following part, hydrophilicity/hydrophobicity, Sn coordination state, and Lewis acidity of Sn-Beta-SAC prepared via interzeolite transformation,

-p

which are closely related to their catalytic performances [26,35], are systematically investigated.

re

It was generally accepted that the hydrophobicity of Sn-Beta synthesized with the aid of alkali metal ions such as Na+ was poor because framework silanols were compensated for not only

lP

TEA+ but also alkali metal ions in the zeolite [26,27]. Whereas, Sn-Beta-F zeolites obtained by fluoride-assisted route possessed relatively good hydrophobicity on account of that not only

na

framework defects but also F− in the synthesis systems could be in conjunction with structure-

ur

directing agent of TEA+ occluded in the zeolite [10,32]. Nanosized Sn-Beta-SAC prepared under fluoride and alkali metal ions free conditions should exhibit lower hydrophobicity than bulky Sn-

Jo

Beta-F. Water vapor adsorption isotherms were performed to assess materials hydrophobicity. As shown in Fig. 6, a type II adsorption isotherm was clearly observed for both Sn-Beta zeolite materials [46]. It is generally recognized that zeolitic framework with more hydrophobicity would adsorb less amount of water [52]. In comparison with Sn-Beta-F-120, Sn-Beta-SAC-120 demonstrated similar water vapor adsorption behavior in the region of microporous and more 18

total water vapor adsorption amounts, indicating that the hydrophobicity of Sn-Beta-SAC-120 achieved without the aid of fluoride and alkali metal ions was slightly inferior to that of Sn-BetaF-120 synthesized in a fluoride medium. To further give an in-depth insight into the hydrophobicity issue, 29Si MAS NMR of Sn-Beta zeolites were carried out. As shown in Fig. 7, each spectrum was deconvoluted into five resonances (-101.6, -106.3, -111.1, -115.1, and -120.2 ppm) in the region of -80 to -130 ppm. The

ro of

isotropic chemical shift of -101.6 ppm was ascribed to (SiO)3Si(OH) groups (i.e., Q3) and other ones were assigned to (SiO)4Si groups (i.e., Q4) [33,46]. After normalization and calculation, a higher Q3 species content (8.3 %) for Sn-Beta-SAC-120 than that for Sn-Beta-F-120 (4.7 %) was

-p

obviously observed. This result verified that Sn-Beta-SAC-120 zeolite material possessed

re

slightly more defects sites than Sn-Beta-F-120. At this point, it could be concluded that the hydrophobicity of Sn-Beta-SAC-120 synthesized by interzeolite transformation was slightly

lP

lower than that of Sn-Beta-F-120 obtained via conventional fluoride-assisted method, which was

na

derived from more silanol groups in the former material. Other than hydrophilicity/hydrophobicity, the micro-environment of heteroatoms in

ur

metallosilicates also plays a foremost role in their catalytic applications [41,52]. Normally, the isolated metal ions in the zeolitic framework are closely associated with their catalytic activities,

Jo

whereas bulk metallic oxides in the extra-framework have a detrimental effect [2,36]. Thus, the Sn coordination state of Sn-Beta-SAC zeolites was explored by UV-vis spectra and XPS before used as catalysts. Diffuse reflectance UV–visible (UV–vis) spectroscopy was applied to detect the coordination states of metal ions in Sn-Beta-SAC zeolites through the charge transfer of Sn-O [35]. Fig. 8 19

shows the UV–vis spectra of Sn-Beta-SAC zeolites prepared by interzeolite transformation, with various Sn contents from 0.95 up to 2.39 wt %. The band below 250 nm was assigned to hydrated tetrahedrally coordinated Sn(IV) or polymerized extra-framework Sn species, whereas that ranged from 250 to 350 nm was used as an indicator of Sn oxide species [37,41]. A sharp signal peak centred at 208 nm, along with a very weak shoulder at 231 nm, were obviously observed in all spectra, which was different from the observation of Sn-Beta-F-120 affording only one intense

ro of

band at about 208 nm (Fig. S12). To distinguish tetrahedrally coordinated and polymerized extraframework Sn species in the region of below 250 nm, XPS measurement was adopted to identify this issue (Fig. S13). It was found that the band below 250 nm was assigned to hydrated

-p

tetrahedrally coordinated Sn(IV). In combination with XPS results, they unambiguously implied

re

that Sn ions in Sn-Beta-SAC samples mainly existed in the form of isolated four-fold coordination. On the other hand, no signal above 300 nm was found in all the spectra, further

lP

indicating that no bulky Sn oxide was formed in Sn-Beta-SAC samples [41], even in Sn-Beta-

na

SAC-80 with a high Sn content of 2.39 wt % (Si/Sn = 81). As a result, Sn-Beta-SAC indeed possessed isolated tetrahedrally-coordinated Sn sites and similar Sn type compared to Sn-Beta-F

ur

(evidenced by FT-IR spectra of CD3CN adsorption in Fig. S14). Sn-Beta zeolite was considered to be a state-of-the-art catalyst in Lewis-catalyzed reactions

Jo

[1,11]. Therefore, the Lewis acidity of the Sn-Beta-SAC zeolite prepared in this work was probed before being adopted in corresponding catalytic process. Fig. 9 exhibited the FT-IR spectra of Sn-Beta-SAC containing various Sn contents with adsorbed pyridine. In the case of Sn-BetaSAC-80, the 1445 and 1596 cm−1 bands, associated with hydrogen-bonded pyridine [32], were clearly observed after pyridine desorption at the temperature below 423 K. It also shown 1451, 20

1490, and 1611 cm−1 signal bands corresponding to Lewis acid sites [33]. With the increase of desorption temperature, the intensities of all corresponding bands decreased. However, at the elevated temperature of 523 K, 1445 and 1596 cm−1 bands nearly vanished completely and sole Lewis acid-related peaks were present, revealing the strong interaction between isolated framework Sn sites and pyridine molecules. On the other hand, Sn-Beta-SAC-80, which possessed largest signal intensities of Lewis acid among Sn-Beta-SAC zeolites (Fig. 9B),

ro of

demonstrated higher intensities of Lewis acid-related band at the same temperature by comparing with Sn-Beta-F-120 due to the higher isolated Sn content of the former (Fig. S15). The strength of Lewis acid was qualitatively determined by the ratio of 1451 cm−1 band intensities recorded at

-p

423 and 373 K [32]. The larger value of Sn-Beta-SAC-120 (0.80) than Sn-Beta-F-120 (0.43) was

re

observed (Fig. S15), indicating the higher Lewis acid strength of Sn-Beta-SAC-120. Consequently, the isolated Sn in Sn-Beta-SAC zeolite framework endowed it Lewis acidity with

lP

high strength.

na

From above characterizations and analyses, it further confirmed that it was under fluoride and alkali metal ions free conditions that Sn-Beta-SAC zeolite was rapidly hydrothermally

ur

synthesized via our developed innovative interzeolite transformation protocol. To the best of our knowledge, the crystal size of Sn-Beta-SAC (50–150 nm) was the smallest among present

Jo

hydrothermal ones. More importantly, the Sn contents in Sn-Beta-SAC could achieved to 2.39 wt % (Si/Sn = 81), breaking through the Sn content restriction of conventional approach. In addition, although this resultant Sn-Beta-SAC zeolites possessed hydrophobicity slightly inferior to Sn-Beta-F obtained via traditional fluoride-assisted route, larger amounts of isolated framework Sn4+ sites in the former gave rise to more Lewis acidic sites with high strength, 21

facilitating this zeolite material capable of catalyzing Baeyer-Villiger oxidant of ketones. 3.4. Catalytic performances Baeyer-Villiger (B-V) oxidation of ketones was widely applied in the industrially-relevant field of pharmaceuticals, polymerization, agrochemistry, and so on [25]. In order to give an insight into the superiority of Sn-Beta-SAC zeolite catalyst prepared via innovative interzeolite transformation, including high Sn contents and nanosized crystals, the B–V oxidation of ketones

ro of

is adopted as the model reaction to evaluate catalytic performance of this material.

The B–V oxidation of 2-adamantanone was carried out over Sn-Beta catalysts using aqueous H2O2 as the oxidant at 363 K. The product selectivity was usually as high as 100 % during this

-p

process. This reaction almost could not proceed over blank experiment without adding catalyst

re

into reaction system as well as over Sn-free Beta-SAC, indicating the active sites of B-V oxidation resulted from isolated Sn ions in the zeolite framework. As exhibited in Fig. 10, as for

lP

each catalyst, with the reaction time increasing, an initially fast enhancement for the conversion

na

of 2-adamantanone was observed and then the increase became gradually slow. As analyzed above (vide supra), the hydrophobicity of Sn-Beta-SAC was inferior to that of Sn-Beta-F. Thus,

ur

Sn-Beta-SAC-120 should exhibit lower catalytic performance than Sn-Beta-F-120 in an aqueous reaction under comparable Sn contents conditions. Nonetheless, beyond our expection, Sn-Beta-

Jo

SAC-120 sample showed slightly larger catalytic performance in terms of conversion than SnBeta-F-120 prepared by conventional fluoride-assisted method. It is important to highlight that the nanosized crystal (50–150 nm) of Sn-Beta-SAC-120 zeolite contributed to relatively good diffusion properties compared to bulky microsized Sn-Beta-F-120 (> 1 μm). Additionally, Madon-Boudart test confirmed that diffusion limitation for Baeyer-Villiger oxidation of 222

adamantanone over Sn-Beta-F and Sn-Beta-SAC zeolites existed under the present reaction conditions (Fig. S16). At this point, it could be inferred that this catalytic results were arised from the combinatorial effect of hydrophobicity and diffusion properties, while diffusion properties featured this reaction. This issue would be further discussed in detail in the following part (vide infra). With the Sn contents increasing, in the case of Sn-Beta-SAC-80, the conversion of 2adamantanone further increased, which was higher than that for Sn-Beta-SAC-120. The high

ro of

conversion of Sn-Beta-SAC-80 was likely ascribed to its numerous Lewis acid sites resulting from high isolated framework Sn contents.

As can be seen from above experiment results, when using H2O2 with small molecular sizes

-p

as the oxidant, the discrepancy in catalytic performances for Sn-Beta-SAC and Sn-Beta-F was

re

not so obvious. To further manifest the preponderance of Sn-Beta-SAC zeolite catalyst, especially small crystals, the B-V oxidation of 2-adamantanone was performed with the bulky

lP

oxidant of TBHP. As shown in Table 2, compared with H2O2 system, the catalytic performances

na

for each kind of catalyst in the TBHP system decreased sharply due to the fact that the bulky intermediate substances formed in this system suffered from severe steric restrictions inside the

ur

micropore structure [25,36]. Compared with the benchmark of Sn-Beta-F-120, the conversion and turnover number (TON) of Sn-Beta-SAC-120 increased by 6.6 and 3.3 %, respectively, in

Jo

H2O2 systems. Surprisingly, the difference between Sn-Beta-SAC-120 and Sn-Beta-F-120 in TBHP/decane systems became more evident (conversion, 150.6 %; TON, 141.9 %), which was on account of the fact that the small crystals of Sn-Beta-SAC-120 gived reactants more chance to contact with Sn active sites. Once a little water was introduced into the reaction system, that is, 70 wt % aqueous TBHP was used as the oxidant, the activities of Sn-Beta zeolites decreased 23

dramatically. Some water molecules would adsorb on active Sn sites, preventing substrates of ketones access to zeolitic Sn sites [53]. The increase of ketones conversion was observed with the Sn contents enhancing, which was the same as that in H2O2 system. To account for the diffusion issue, the adsorption and diffusion of 2-adamantanone inside the pore systems of Sn-Beta zeolites were performed using 1,3,5-triisopropylbenzene as a solvent. The adsorption rate was determined from millimoles of 2-adamantanone adsorbed hourly per

ro of

gram of catalyst at 40 min. As shown in Fig. 11, Sn-Beta-SAC-120 clearly revealed higher adsorption rate (0.508 mmol g–1 h–1) in comparison to Sn-Beta-F-120 (0.431 mmol g–1 h–1) in an anhydrous adsorption system. As expected, if adding very little water into the adsorption systems,

-p

the adsorption rate for both Sn-containing Beta zeolite materials decreased significantly.

re

However, the adsorption rate of Sn-Beta-SAC-120 material (0.371 mmol g–1 h–1) was still larger than that of Sn-Beta-F-120 (0.345 mmol g–1 h–1). As literatures reported, water would compete

lP

with reaction substrate for adsorption on framework Sn sites in a aqueous phase, especially for

na

these stannosilicate materials with low hydrophobicity [25,52,53]. Additionally, compared with anhydrous systems, the adsorption rate of Sn-Beta-SAC-120 zeolite decreased by 27.0 % under

ur

aqueous conditions, which was beyond than that (20.0 %) of Sn-Beta-F-120. This analysis result further confirmed that the hydrophobicity of Sn-Beta-SAC-120 was inferior to that of Sn-Beta-

Jo

F-120, in line with the observations of water vapor isotherms and

29

Si MAS NMR. The

conclusion could be made that Sn-Beta-SAC zeolite prepared by interzeolite transformation possessed relatively good diffusion properties compared with Sn-Beta-F synthesized with the assistance of fluoride, which was contributed by the smaller crystal size of Sn-Beta-SAC. In conclusion, compared with Sn-Beta-F with bulky crystal in size, the small crystal size of 24

Sn-Beta-SAC resulted in relatively good diffusion properties, giving high catalytic performances in the B-V oxidation particularly with bulky oxidant of TBHP. Most importantly, the activities for Sn-Beta-SAC-80 with a higher Sn content in the framework, which could not be achieved via traditional fluoride-assisted method, further increased, certifying that Sn-Beta-SAC zeolites hydrothermally synthesized by interzeolite transformation under fluoride and alkali metal ions free conditions are indeed reliable and robust solid Lewis acid catalysts.

ro of

4. Conclusions

It is for the first time under fluoride and alkali metal ions free conditions that highly crystallized Sn-Beta-SAC zeolite is hydrothermally synthesized via degradation of siliceous FAU

-p

zeolite and recrystallization silicate fragments with the steam-assisted conversion at 413 K in a

re

very short period. The framework structure similarity between FAU and Beta zeolite played a vital role in the facile transformation of FAU to Sn-Beta zeolite. What’s more, the upper Sn

lP

contents in resultant Sn-Beta-SAC zeolite could reach to 2.39 wt % (Si/Sn = 81), breaking

na

through the Sn content limitation of Sn-Beta-F synthesized via traditional fluoride-assisted method. To our knowledge, the Sn-Beta-SAC with tetrahetrally coordinated Sn ions possessed

ur

smallest crystal in size (50–150 nm) among all the present hydrohermal synthesized strategies. Although the hydrophobicity of Sn-Beta-SAC zeolite was inferior to Sn-Beta-F, the relatively

Jo

good diffusion properties and relieved steric restrictions for Sn-Beta-SAC, resulting from the smaller crystal size, contributed to high catalytic performances in the B-V oxidation of ketones especially with bulky TBHP as the oxidant. This interzeolite transformation methodology provides an environmentally friendly and alternative route to synthesize Sn-Beta zeolite with nanosized crystal sizes, which will be promising to synthesize other metallosilicate catalyst 25

materials.

Author contributions H. Ma performed the catalyst preparation, characterizations and catalytic tests. M. Li performed the catalytic tests. T. Su performed the data analysis and offered helpful suggestions. Z. Zhu and

ro of

H. Lü designed this study, analysed the data and wrote the paper.

Acknowledgments

We gratefully acknowledge the financial supports from the NSFC of China (21676230 and

Appendix A. Supplementary data

re

-p

21373177).

lP

Supplementary material related to this article can be found, in the online version, at

Jo

ur

na

doi:https://doi.org/

26

References [1] A. Corma, L.T. Nemeth, M. Renz, S. Valencia, Nature 412 (2001) 423–425. [2] P. Wu, T. Tatsumi, T. Komatsu, T. Yashima, J. Phys. Chem. B 105 (2001) 2897–2905. [3] Y. Wang, J.D. Lewis, Y. Román-Leshkov, ACS Catal. 6 (2016) 2739–2744. [4] A. Corma, F.X.L. Xamena, C. Prestipino, M. Renz, S. Valencia, J. Phys. Chem. C 113 (2009) 11306–11315.

ro of

[5] J.D. Lewis, S. Van de Vyver, Y. Román-Leshkov, Angew. Chem. 127 (2015) 9973–9976.

[6] C.M. Osmundsen, M.S. Holm, S. Dahl, E. Taarning, Proc. R. Soc. A 468 (2012) 2000–2016. [7] A. Corma, M.E. Domine, L. Nemeth, S. Valencia, J. Am. Chem. Soc. 124 (2002) 3194–3195.

-p

[8] S. Van de Vyver, C. Odermatt, K. Romero, T. Prasomsri, Y. Román-Leshkov, ACS Catal. 5

re

(2015) 972–977.

[9] E. Mahmoud, J. Yu, R.J. Gorte, R.F. Lobo, ACS Catal. 5 (2015) 6946–6955.

lP

[10] V. Choudhary, A.B. Pinar, S.I. Sandler, D.G. Vlachos, R.F. Lobo, ACS Catal. 1 (2011) 1724–

na

1728.

[11] M.S. Holm, S. Saravanamurugan, E. Taarning, Science 328 (2010) 602–605.

ur

[12] E. Nikolla, Y. Román-Leshkov, M. Moliner, M.E. Davis, ACS Catal., 1 (2011) 408–410. [13] L.L, J. Ding, J. Jiang, Z. Zhu, P. Wu, Chinese J. Catal. 36 (2015) 820–828.

Jo

[14] M. Moliner, Y. Román-Leshkov, M.E. Davis, Proc. Natl. Sci. U.S.A. 107 (2010) 6164–6168. [15] G. Li, E.A. Pidko, E.J.M. Hensen, Catal. Sci. Technol. 4 (2014) 2241–2250. [16] B. Tang, W. Dai, G. Wu, N. Guan, L. Li, M. Hunger, ACS Catal. 4 (2014) 2801–2810. [17] B.C. Bukowski, J.S. Bates, R. Gounder, J. Greeley, J. Catal., 365 (2018) 261–276. [18] Y. Chai, L. Xie, Z. Yu, W. Dai, G. Wu, N. Guan, L. Li, Micropor. Mesopor. Mater. 264 (2018) 27

230–239. [19] N.K. Mal, V. Ramaswamy, P.R. Rajamohanan, A.V. Ramaswamy, Micropor. Mater. 12 (1997) 331–340. [20] N.K. Mal, V. Ramaswamy, S. Ganapathy, A.V. Ramaswamy, Appl. Catal. A: Gen. 125 (1995) 233–245. [21] Q. Guo, F. Fan, E.A. Pidko, W.N. Graaff, Z. Feng, C. Li, E.J. Hensen, ChemSusChem. 6

ro of

(2013) 1352–1356.

[22] G. Liu, J. Jiang, B. Yang, X. Fang, H. Xu, H. Peng, L. Xu, Y. Liu, P. Wu, Micropor. Mesopor. Mater. 165 (2013) 210–218.

-p

[23] H.Y. Luo, L. Bui, W.R. Gunther, E. Min, Y. Román-Leshkov, ACS Catal. 2 (2012) 2695–

re

2699.

[24] A. Corma, M. Teresa, L. Nemeth, M. Renz, Chem. Commun. (2001) 2190–2191.

lP

[25] Z. Zhu, H. Xu, J. Jiang, P. Wu, J. Phys. Chem. C 120 (2016) 23613–23624.

na

[26] C. Chang, H. Je Cho, Z. Wang, X. Wang, W. Fan, Green Chem. 17 (2015) 2943–2951. [27] H. Xu, X. Wang, P. Ji, H. Wu, Y. Guan, P. Wu, Inorg. Chem. Front. 5 (2018) 2763–2771.

ur

[28] C. Chang, Z. Wang, P. Dornath, H. Je Cho, W. Fan, RSC Adv. 2 (2012) 10475–10477. [29] Z. Kang, X. Zhang, H. Liu, J. Qiu, K.L. Yeung, Chem. Eng. J. 218 (2013) 425–432.

Jo

[30] Z. Kang, X. Zhang, H. Liu, J. Qiu, W. Han, K.L. Yeung, Mater. Chem. Phys. 141 (2013) 519–529.

[31] T. lida, A. Takagaki, S. Kohara, T. Okubo, T. Wakihara, ChemNanoMat. 1 (2015) 155–158. [32] Z. Zhu, H. Xu, J. Jiang, Y. Guan, P. Wu, J. Catal. 352 (2017) 1–12. [33] Z. Zhu, H. Xu, J. Jiang, H. Wu, P. Wu, Chem. Commun. 53 (2017) 12516–12519. 28

[34] Q. Meng, J. Liu, G. Xiong, X. Liu, L. Liu, H. Guo, Micropor. Mesopor. Mater. 266 (2018) 242–251. [35] P. Li, G. Liu, H. Wu, Y. Liu, J. Jiang, P. Wu, J. Phys. Chem. C 115 (2011) 3663–3670. [36] Z. Zhu, H. Xu, J. Jiang, Y. Guan, P. Wu, Appl. Catal. A, Gen. 556 (2018) 52–63. [37] J. Dijkmans, D. Gabriëls, M. Dusselier, F. de Clippel, P. Vanelderen, K. Houthoofd, A. Malfliet, Y. Pontikes, B.F. Sels, Green Chem. 15 (2013) 2777–2785.

ro of

[38] J.C. Vega-Vila, J.W. Harris, R. Gounder, J. Catal. 344 (2016) 108–120.

[39] C. Hammond, S. Conrad, I. Hermans, Angew. Chem. Int. Ed. 51 (2012) 11736–11739.

[40] X. Yang, J. Bian, J. Huang, W. Xin, T. Lu, C. Chen, Y. Su, L. Zhou, F. Wang, J. Xu, Green

-p

Chem. 19 (2017) 692–701.

re

[41] J. Dijkmans, J. Demol, K. Houthoofd, S. Huang, Y. Pontikes, B. Sels, J. Catal. 330 (2015) 545–557.

lP

[42] S. Goel, S.I. Zones, E. Iglesia, Chem. Mater. 27 (2015) 2056–2066.

11542–11549.

na

[43] K. Itabashi, Y. Kamimura, K. Lyoki, A. Shimojima, T. Okubo, J. Am. Chem. Soc. 134 (2012)

ur

[44] C. Li, M. Moliner, A. Corma, Angew. Chem. Int. Ed. 57 (2018) 15330–15353. [45] X. Xiong, D. Yuan, Q. Wu, F. Chen, X. Meng, R. Lv, D. Dai, S. Maurer, R. Mcguire, M.

Jo

Feyen, U. Müller, W. Zhang, T. Yokoi, X. Bao, H. Gies, B. Marler, D.E. De Vos, U. Kolb, A. Mini, F. Xiao, J. Mater. Chem. A 5 (2017) 9076–9080.

[46] Z. Zhu, H. Xu, J. Jiang, H. Wu, P. Wu, ACS Appl. Mater. Interfaces 9 (2017) 27273–27283. [47] Z. Zhu, H. Xu, J. Jiang, X. Liu, J. Ding, P. Wu, Appl. Catal. A: Gen. 519 (2016) 155–164. [48] J.C. Jansen, F.J. van der Gaag, H. van Bekkum, Zeolites 4 (1984) 369–372. 29

[49] T. Ikuno, W. Chaikittisilp, Z. Liu, T. Iida, Y. Yanaba, T. Yoshikawa, S. Kohara, T. Wakihara, T. Okubo, J. Am. Chem. Soc. 137 (2015) 14533–14544. [50] B. Wang, M. Lin, J. Yang, X. Peng, B. Zhu, Y. Zhang, C. Xia, W. Liao, X. Shu, Micropor. Mesopor. Mater. 266 (2018) 43–46. [51] H. Jon, K. Nakahata, B. Lu, Y. Oumi, T. Sano, Micropor. Mesopor. Mater. 96 (2006) 72–78. [52] P. Wolf, M. Valla, F. Núñez-Zarur, A. Comas-Vives, A.J. Rossini, C. Firth, H. Kallas, A.

ro of

Lesage, L. Emsley, C. Copéret, I. Hermans, ACS Catal. 6 (2016) 4047–4063.

[53] W.N.P. van der Graaff, C.H.L. Tempelman, G. Li, B. Mezari, N. Kosinov, E.A. Pidko, E.J.M.

Jo

ur

na

lP

re

-p

Hensen, ChemSusChem. 9 (2016) 3145–3149.

30

Figure captions Fig. 1. (A) XRD patterns and (B) yields of calcined solid products during the crystallization of Sn-Beta-SAC for 0 d (a), 0.5 d (b), 1 d (c), 2 d (d), 3 d (e), and 8 d (f). The product yields were quantified from the calcined samples. Other crystallization conditions: SiO2/SnO2 = 120; TEAOH/SiO2 = 0.5; Beta seeds, 10 wt %; temp., 413 K. Fig. 2. FT-IR spectra of calcined solid products during the crystallization of Sn-Beta-SAC for 0

ro of

d (a), 0.5 d (b), 1 d (c), 2 d (d), 3 d (e), and 8 d (f). Other crystallization conditions: see Fig. 1. Fig. 3. Scanning electron micrographs of pristine USY-DA zeolite (a) and products during the crystallization of Sn-Beta-SAC for 0.5 d (b), 1 d (c), 2 d (d), 3 d (e), and 8 d (f). Other

-p

crystallization conditions: see Fig. 1.

Fig. 4. Scanning electron micrographs of Sn-Beta-SAC-120 (a), Sn-Beta-F-120 (b), and

re

transmission electron microscope images of Sn-Beta-SAC-120 (c, d).

lP

Fig. 5. XRD patterns of calcined solid products prepared from highly dealuminated USY-DA (a), all-silica MFI (b), and all-silica NON (c) via steam-assisted conversion. Crystallization

na

conditions: SiO2/SnO2 = 120; TEAOH/SiO2 = 0.5; Beta seeds, 10 wt %; temp., 413 K; time, 3 d.

K.

ur

Fig. 6. Water vapor adsorption isotherms of Sn-Beta-SAC-120 (a) and Sn-Beta-F-120 (b) at 298

Jo

Fig. 7. Solid-state 29Si NMR MAS spectra of Sn-Beta-SAC-120 (A) and Sn-Beta-F-120 (B). The dotted and solid light grey line indicates the recorded and cumulated signals, respectively. Fig. 8. UV-vis spectra of Sn-Beta-SAC samples with Si/Sn molar ratio of 200 (a), 120 (b), and 80 (c). Fig. 9. (A) FT-IR spectra of Sn-Beta-SAC-80 after pyridine adsorption at 298 K for 1 h and desorption at 323 K (a), 373 K (b), 423 K (c), and 523 K (d) for 1 h, respectively. (B) FT-IR 31

spectra of Sn-Beta-SAC with Si/Sn ratio of 80 (a), 120 (b), and 200 (c) after pyridine adsorption at 298 K for 1 h and desorption at 523 K for 1 h. Fig. 10. Dependence of 2-adamantanone conversion on the reaction over Sn-Beta-F-120 (a), SnBeta-SAC-120 (b), and Sn-Beta-SAC-80 (c). Reaction conditions: cat, 50 mg; 2-adamantanone, 2 mmol; H2O2 (65 wt %), 4 mmol; chlorobenzene, 10 mL; temp., 363 K. Fig. 11. Adsorption of 2-adamantanone in liquid-phase conditions over Sn-containing catalysts.

ro of

Sn-Beta-SAC-120 under anhydrous conditions (a), Sn-Beta-F-120 under anhydrous conditions (b), Sn-Beta-SAC-120 under hydrous conditions (c), Sn-Beta-F-120 under hydrous conditions (d). Adsorption conditions: catalyst, 50 mg; 0.5 wt % 2-adamantanone in 1,3,5-TIPB, 2 g; temp.,

Jo

ur

na

lP

re

-p

298 K; water if added, 0.2 g.

32

ro of

Scheme 1. Schematic illustration of the proposed crystallization process for nanosized Sn-Beta zeolite hydrothermally synthesized via interzeolite transformation without the assistance of

Jo

ur

na

lP

re

-p

fluoride and alkali metal ions.

33

Table 1 Textural properties of various Sn-containing Beta samples. Sample

Timea (d)

Structureb

Si/Ald

Sn-Beta-SAC-200

1

*BEA

Sn-Beta-SAC-120

3

Sn-Beta-SAC-80

Pore volume (cm3 g−1)

Si/Sn Gel

Productd

Vemicro

513

200

198

0.21

*BEA

511

120

123

15

*BEA

514

80

Sn-Beta-SAC-70

>30

Amor.c

-

Sn-Beta-F-200

6

*BEA

Sn-Beta-F-120

21

Sn-Beta-F-80

>50

Vfmeso

SSAg (m2 g−1) Shmicro

Seext

0.10

635

468

167

0.20

0.09

630

470

160

81

0.18

0.09

601

449

152

70

-

-

-

-

-

-

∞

200

205

0.21

0.03

546

474

72

*BEA

∞

120

127

0.20

0.04

516

460

60

Amor.c

∞

80

-

-

-

-

-

ro of

Sftot

Indicating hydrothermal treatment time.

b

Identified by XRD technology.

c

Amor. indicates amorphous phase.

d

Determined by ICP analysis.

e

Calculated by t-plot method.

f

Vtotal and Stot, calculated by BET method; Vmeso = Vtotal – Vmicro.

g

Specific surface area (SSA), determined by N2 adsorption at 77 K.

h

Smicro = Stot – Sext.

Jo

ur na

lP

re

-p

a

34

-

T Table 2 Oxidation of cyclic ketone with TBHP over Sn-containing catalysts. Sn-Beta

＋

＋

H2O2

Sn-Beta

＋

H2O

363 K

363 K

TBHP in watera No.

Samples

Si/Sn

1

Sn-Beta-SAC-80

81

6.7

1.6

24.1

2

Sn-Beta-SAC-120

123

5.1

1.9

3

Sn-Beta-F-120

127

2.7

1.1

Conv.c (%)

TONd (h−1)

Conv.e (%)

TONf (h−1)

H2O2 in waterb Conv.g (%)

TONh (h−1)

5.9

96.7

94.2

20.3

7.5

86.6

127.8

8.1

3.1

81.2

123.7

ro of

a

TBHP in decanea

＋

Reaction conditions: cat, 50 mg; 2-adamantanone, 2 mmol; TBHP (70 wt % in water or 5.5 M in decane), 4 mmol; chlorobenzene, 10 mL; temp., 363 K; time, 8 h.

Reaction conditions: cat, 50 mg; 2-adamantanone, 2 mmol; H2O2 (65 wt %), 4 mmol;

The variability was within ± 4.5 %.

e, f

The variability was within ± 3.9 %.

g,h

The variability was within ± 2.0 %.

Jo

ur

na

lP

c, d

re

chlorobenzene, 10 mL; temp., 363 K; time, 2 h.

-p

b

35

A

120

Intensity (a.u.)

f

100

Yield (%)

e d c

5

10

20

25

30

60

20

a 15

80

40

b 0.5

B

0

35

a

b

c

d

Time (d)

e

f

ro of

2 Theta ()

Fig. 1. (A) XRD patterns and (B) yields of calcined solid products during the crystallization of Sn-Beta-SAC for 0 d (a), 0.5 d (b), 1 d (c), 2 d (d), 3 d (e), 8 d (f). The product yields were

-p

quantified from the calcined samples. Other crystallization conditions: SiO2/SnO2 = 120;

Jo

ur

na

lP

re

TEAOH/SiO2 = 0.5; Beta seeds, 10 wt %; temp., 413 K.

36

572

1231

1300

624 521

f e d c b a 1130

960

790

620

Wavenumber (cm-1)

450

ro of

Absorbance (a.u.)

1101

Fig. 2. FT-IR spectra of calcined solid products during the crystallization of Sn-Beta-SAC for 0

Jo

ur

na

lP

re

-p

d (a), 0.5 d (b), 1 d (c), 2 d (d), 3 d (e), and 8 d (f). Other crystallization conditions: see Fig. 1.

37

a

b 500 nm

2 μm

2 μm

c

ro of

d

2 μm

e

f

lP

2 μm

re

200 nm

-p

2 μm

500 nm

na

Fig. 3. Scanning electron micrographs of pristine USY-DA zeolite (a) and products during the crystallization of Sn-Beta-SAC for 0.5 d (b), 1 d (c), 2 d (d), 3 d (e), and 8 d (f). Other

Jo

ur

crystallization conditions: see Fig. 1.

38

a

b 1 μm

1 μm

5 μm

500 nm

c

ro of

d

20 nm

100 nm

Fig. 4. Scanning electron micrographs of Sn-Beta-SAC-120 (a), Sn-Beta-F-120 (b), and

Jo

ur

na

lP

re

-p

transmission electron microscope images of Sn-Beta-SAC-120 (c, d).

39

Intensity (a.u.)

c b

5

10

15

20

25

2 Theta ()

30

ro of

a 35

Fig. 5. XRD patterns of calcined solid products prepared from highly dealuminated USY-DA (a),

-p

all-silica MFI (b), and all-silica NON (c) via steam-assisted conversion. Crystallization

Jo

ur

na

lP

re

conditions: SiO2/SnO2 = 120; TEAOH/SiO2 = 0.5; Beta seeds, 10 wt %; temp., 413 K; time, 3 d.

40

a

3 -1

H2O adsorbed (cm g )

120

80

b 40

0 0.0

0.2

0.4

0.6

0.8

1.0

ro of

P/P0

Fig. 6. Water vapor adsorption isotherms of Sn-Beta-SAC-120 (a) and Sn-Beta-F-120 (b) at 298

Jo

ur

na

lP

re

-p

K.

41

A

B

Q3/(Q3 + Q4) = 4.7 %

ro of

Q3/(Q3 + Q4) = 8.3 %

Fig. 7. Solid-state 29Si NMR MAS spectra of Sn-Beta-SAC-120 (A) and Sn-Beta-F-120 (B). The

Jo

ur

na

lP

re

-p

dotted and solid light grey line indicates the recorded and cumulated signals, respectively.

42

Absorbance (a.u.)

208 231

c b a

200

250

300

350

400

Wavelength (nm)

ro of

a Fig. 8. UV-vis spectra of Sn-Beta-SAC samples with Si/Sn molar ratio of 200 (a), 120

Jo

ur

na

lP

re

-p

(b), and 80 (c).

A

1451

1451

1490

e (a.u.)

e (a.u.)

1596

B

1445

1611

a

43

1611

a

1490

ro of

Fig. 9. (A) FT-IR spectra of Sn-Beta-SAC-80 after pyridine adsorption at 298 K for 1 h and desorption at 323 K (a), 373 K (b), 423 K (c), and 523 K (d) for 1 h, respectively. (B) FT-IR

Jo

ur

na

lP

re

at 298 K for 1 h and desorption at 523 K for 1 h.

-p

spectra of Sn-Beta-SAC with Si/Sn ratio of 80 (a), 120 (b), and 200 (c) after pyridine adsorption

44

ne (%)

100 80

c b a

Sn-Beta

＋ H2O2

＋ H2O

ro of

363 K

Fig. 10. Dependence of 2-adamantanone conversion on the reaction over Sn-Beta-F-120 (a), SnBeta-SAC-120 (b), and Sn-Beta-SAC-80 (c). Reaction conditions: cat, 50 mg; 2-adamantanone,

Jo

ur

na

lP

re

-p

2 mmol; H2O2 (65 wt %), 4 mmol; chlorobenzene, 10 mL; temp., 363 K.

45

-1

Adsorbed ketone (mmol g )

0.4

a b c d

0.3

0.2

0.1

0.0 30

60

Adsorption time (min)

90

ro of

0

Fig. 11. Adsorption of 2-adamantanone in liquid-phase conditions over Sn-containing catalysts.

-p

Sn-Beta-SAC-120 under anhydrous conditions (a), Sn-Beta-F-120 under anhydrous conditions (b), Sn-Beta-SAC-120 under hydrous conditions (c), Sn-Beta-F-120 under hydrous conditions

re

(d). Adsorption conditions: catalyst, 50 mg; 0.5 wt % 2-adamantanone in 1,3,5-TIPB, 2 g; temp.,

Jo

ur

na

lP

298 K; water if added, 0.2 g.

46