Synthesis of Sn-Containing Nanosized Beta Zeolite As Efficient

Subscriber access provided by Washington University | Libraries

Article

Synthesis of Sn-Containing Nano-Sized Beta Zeolite as Efficient Catalyst for Transformation of Glucose to Methyl Lactate Xiaomei Yang, Ying Liu, Xiaoxin Li, Jinxiu Ren, Lipeng Zhou, Tianliang Lu, and Yunlai Su ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.8b00177 • Publication Date (Web): 22 May 2018 Downloaded from http://pubs.acs.org on May 22, 2018

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 39 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Sustainable Chemistry & Engineering

Synthesis of Sn-Containing Nano-Sized Beta Zeolite as Efficient Catalyst for Transformation of Glucose to Methyl Lactate Xiaomei Yang,*,† Ying Liu,† Xiaoxin Li,† Jinxiu Ren,† Lipeng Zhou,† Tianliang Lu,‡ Yunlai Su†

†

College of Chemistry and Molecular Engineering, and

‡

School of Chemical

Engineering and Energy, Zhengzhou University, 100 Kexue Road, Zhengzhou 450001, People’s Republic of China

*X. Yang. E-mail: [email protected]

ACS Paragon Plus Environment

ACS Sustainable Chemistry & Engineering 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ABSTRACT: Rapid synthesis of Sn-containing nano-sized all silica Beta zeolite was developed in this work. The method employed all-silica Beta (Si-Beta) as parent, which was crystallized in several hours by the hydrothermal method, and incorporated Sn to Si-Beta through grinding with SnCl4·5H2O and subsequent calcination procedure. The prepared Sn-Beta zeolites were analyzed by several methods including XRD, SEM, N2 physisorption, FT-IR spectroscopy of deuterated acetonitrile and pyridine adsorption, UV-vis DR and XPS. The mechanism of incorporation of Sn sites into the framework of zeolite was revealed. The results show that the successful incorporation of Sn sites strongly depends on the crystallinity of the parent Si-Beta. Si-Beta with lower crystallinity (< 90%) had a considerable amount of silanols which provided sites for Sn incorporation into the framework sites. For Si-Beta with higher crystallinity and less silanols, desilication was used to generate more silanols for the incorporation of Sn sites. The prepared Sn-Beta zeolites were effective for the transformation of glucose to methyl lactate (MLA). Its catalytic activity is better than those of Sn-Beta-P prepared by dealumination-stannation of Al-Beta and Sn-Beta-F synthesized through traditional hydrothermal method. Turnover frequency (TOF) was calculated on the amount of framework Sn sites to measure the intrinsic and initial activity of active Sn sites. TOF values varied in the sequence of nano Sn-Beta >> Sn-Beta-F >> Sn-Beta-P. The high MLA yield for nano Sn-Beta is due to its higher mesoporosity. The prepared Sn-Beta zeolite was recycled eight times in the transformation of glucose to MLA without any decrease of catalytic activity. Additionally, the effect of potassium salt on the formation of MLA from glucose over


Page 2 of 39

Page 3 of 39 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Sn-Beta catalyst was studied. KEYWORDS: Beta zeolite, rapid synthesis, glucose, alkyl lactate



Page 4 of 39

INTRODUCTION Metal containing zeolites attract more and more attention as solid Lewis acids with the development of the utilization of biomass resources.1−4 Three-dimensional large-pore (12-membered ring) Sn-containing all silica Beta zeolite (Sn-Beta) exhibits excellent catalytic performance in a variety of important reactions, such as isomerization/epimerization of aldoses,5−8 retro-aldol of hexose/pentose to lactic acid/alkyl

lactate,9−14

Meerwein–Ponndorf–Verley

(MPV)

reduction,15,16

Baeyer–Villiger (BV) oxidation,17,18 aldol-based C-C coupling,19,20 and ring-opening hydration of epoxides.21 Sn-Beta zeolite can be prepared by the hydrothermal synthesis method or the postsynthesis method.2 The former adds Sn precursor to the synthesis gels and then crystallizes the gels to give Sn-Beta zeolite.22,23 The latter method employs aluminosilicate Beta zeolite as the parent through dealumination or desilication to remove some framework atom and then introduction of Sn into the framework via various methods to obtain Sn-Beta zeolite.21,24-29 Through the two methods Sn-Beta zeolite can be prepared successfully; however, the physicochemical properties, especially the micro-environment of Sn4+ sites of the prepared Sn-Beta zeolites are different. For example, the hydrothermally synthesized Sn-Beta zeolite in fluoride media

(Sn-Beta-F) is defect-free

and hydrophobic; whereas the

postsynthesized counterpart is defective and hydrophilic.30−32 The difference in physicochemical properties results in very different catalytic performance for some reactions. A notable example is the retro-aldol reaction of hexose in alcohol to alkyl lactate. Sn-Beta-F exhibits superior performance whereas the postsynthesized Sn-Beta


Page 5 of 39 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


zeolite is inferior for this reaction.11,13 In addition, Sn-Beta-F with less hydrophilic character generally exhibits higher activity and stability for the isomerization of sugars.32 However, synthesis of Sn-Beta zeolite via hydrothermal route in fluoride media is difficult. Sn precursor in the gel retards drastically the nucleation and growth of the crystals, especially at high content of Sn, leading to very long synthesis time. Recently, Tolborg and coworkers studied the hydrothermal preparation of Sn-Beta without the aid of seeds and found that full crystallization of Sn-Beta zeolite with nSi/nSn ratio of ∞, 400, 200, 150, 100 needs 4, 4, 7, 14, 60 days, respectively.22 In order to shorten the preparation time, modified methods using nano seeds,33 dry gel conversion,34,35 Sn–Si mixed oxide composites as materials,36 or interzeolite transformation37 were attempted. In this work, a rapid synthesis method of Sn-Beta zeolite with nano size and fewer defects for efficient transformation of glucose to alkyl lactate was reported. The method uses all-silica Beta (Si-Beta) zeolite as the parent, which can be hydrothermally synthesized in fluoride media in a short crystallization time, and incorporates Sn through condensation of Sn precursor with silanol defect sites of Si-Beta (Scheme 1). The effects of the crystallinity of the parent Si-Beta on the introduction of Sn to Beta framework were studied and the mechanism of introducing Sn sites into the framework was discussed. The prepared Sn-Beta zeolites were characterized by XRD, SEM, N2 physisorption, pyridine FT-IR, deuterated acetonitrile FT-IR, UV-vis DR and XPS and the material was tested as catalyst in the transformation of carbohydrates to alkyl lactate.



Scheme 1. Illustration of the synthesis process of nano-sized Sn-Beta.

EXPERIMENTAL SECTION Synthesis of Sn-Beta Zeolites. The parent Si-Beta zeolites were synthesized according to the procedure reported in literature.22 Dealuminated Beta was used as seed, which was prepared from Al-Beta (nSi/nAl ratio of 38.1, Nankai University Catalyst Co., China) by dealumination with 13 mol L–1 HNO3 solution (20 mL g–1) at 100 oC for 20 h. In a typical synthesis, 69.8 g of tetraethyl orthosilicate (TEOS, AR grade, Aladdin Reagent Co., China) was added dropwise to 107.4 g of aqueous tetraethylammonium hydroxide (TEAOH) solution (25 wt.% aqueous solution, Aladdin Reagent Co., China) under stirring. After TEOS was completely hydrolyzed and the generated ethanol was evaporated, aqueous HF solution (8.9 g, 40 wt.%) was added to form a solid gel. Dealuminated Beta (0.83 g) in H2O (5.8 mL) was added as seed and then the gel was mixed homogeneously. The molar ratio of the gel is SiO2: 0.54 TEAOH: 0.54 HF: 7.5 H2O. The homogeneous gel was divided into several parts, transferred into stainless steel autoclaves with PTFE insert inside and placed to an oven with temperature of 140 oC. After crystallization for desired time, the solid was


Page 6 of 39

Page 7 of 39 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


separated and washed with deionized water for three times. After drying at 100 °C overnight, the powder was heated to 550 °C for 8 h in static air for removal of organic template. The samples were denoted as Si-Beta-xh, where x represents the crystallization time (h). Si-Beta with high crystallinity (Si-Beta-12h) was treated with TEAOH solution (0.3 mol L–1, 10 mL g–1 solution/solid) at 140 oC for 24 h to generate silanol defects. The other procedure is similar with that of the above synthesis of Si-Beta. The treated sample was named as Si-Beta-AT. Sn-Beta zeolites were prepared by grinding calcined Si-Beta-xh or Si-Beta-AT with SnCl4·5H2O (AR grade) in an agate mortar by hand for 1 h. The obtained sample was calcined at 550 oC for 6 h after drying at 100 oC overnight. The obtained Sn-Beta zeolites were named as Sn-Beta-xh, in which theoretical Sn content is 2 wt.%. In addition, a sample with nominal 5 wt.% of Sn was also prepared from Si-Beta-9h, which was denoted as 5Sn-Beta-9h. For comparison, Sn-Beta prepared by hydrothermal route (Sn-Beta-F), Sn-Beta postsynthesized by solid-state ion exchange method (Sn-Beta-P) and SnO2 supported on Si-Beta-9h (SnO2/Si-Beta) were also synthesized. The synthesis procedure of Sn-Beta-F was similar with Si-Beta except that SnCl4·5H2O as a Sn precursor was added and the crystallization time is 15 days. The tin content of Sn-Beta-F analysized by ICP-AES is 1.94 wt.%. The synthesis of Sn-Beta-P was reported in our previous work.13 SnO2/Si-Beta was synthesized through grinding of calcined Si-Beta-9h with SnO2 in a mortar for 1 h and then calcination at 550 oC for 6 h. Sn-Beta-P and



SnO2/Si-Beta also have theoretical Sn content of 2 wt.%. Characterization. The X-ray powder diffraction (XRD) patterns were obtained with a PANalytical X`pert PRO instrument with Cu Kα radiation (λ = 0.15418 nm). The crystallinity of the synthesized zeolites was calculated on the area of the peaks at 2θ of 7.9o and 22.9o. The sorption isotherms of N2 were determined on a Quantachrome Autosorb at –196 oC. Samples were degassed for 3 h at 300 oC before N2 adsorption. Micropore and mesopore size distributions were calculated by Horvath-Kawazoe (HK) method and Barret-Joyner-Halenda (BJH) method, respectively. 29Si MAS NMR spectra were done on a Bruker Avance III spectrometer at a sample spinning rate of 8 kHz. UV-vis DR spectra were collected on an Agilent Technologies Cary Series UV-vis-NIR spectrophotometer. Scanning electron microscopy (SEM) images were obtained on Zeiss-sigma 500. X-ray photoelectron spectroscopy (XPS) was measured on a RBD upgraded PHI-5000C ESCA system (Perkin Elmer) with Mg Kα radiation (hν = 1253.6 eV) operating at 250 W and 14.0 kV. The binding energy of C1s was used as a reference at 284.6 eV. Fourier transform infrared (FT-IR) spectra of -OH region and deuterated acetonitrile (CD3CN) or pyridine adsorbed were recorded on a Bruker Tenser II FT-IR spectrometer. The sample was pressed to a self-supporting wafer (~13 mg) and put into an infrared quartz cell. The wafers were pretreated at 450 oC for 3 h under vacuum to remove water molecule. After the cell was cooled down to 25 oC, the spectrum of hydroxyl region was recorded, which is also used as the background for CD3CN adsorption or pyridine. Subsequently, CD3CN or pyridine vapor was introduced to the quartz cell


Page 8 of 39

Page 9 of 39 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


until the adsorption reached saturation. The spectra of CD3CN were obtained in vacuo at 25 oC for 5 min intervals. For the pyridine FT-IR, the sample was heated to desired temperature under vacuum for half an hour. The spectrum was recorded after the sample was cooled to room temperature. ICP-AES was carried on an iCAP 6000 SERIES instrument. Reaction Procedure. Conversion of carbohydrates to MLA in methanol was performed in a PTFE autoclave (10 mL/80 mL) to study the catalytic properties of the samples. After addition of carbohydrate, catalyst and solvent, the autoclave was sealed and heated to the desired temperature (heating rate, 5 oC min-1) under stirring. The autoclave was quenched in an ice-water mixture when the reaction was finished. After the reaction mixture was diluted with methanol, small aliquots were obtained for quantification. GC-MS was carried out for the identification of the products in the reaction mixture. Pure compounds were also applied as reference for identification of products via GC and HPLC analysis. Analysis of carbohydrates was performed on a Shimadzu LC-20AT HPLC using an Aminex HPX-87H column (300 mm × 7.8 mm) with a refractive index detector. The column temperature was 60 oC with 0.005 mol L–1 H2SO4 (flow rate = 0.5 mL min–1) as mobile phase. Yield of MLA was analyzed on a Shimadzu GC (GC 2104C, FID detector) using an OV-1701 column (30 m × 0.24 mm).

RESULTS AND DISCUSSION Synthesis of the Parent Si-Beta Zeolites. The parent Si-Beta zeolites were hydrothermally synthesized at 140 oC in fluoride media with dealuminated Beta



zeolite as seeds. Figure 1 gives the XRD patterns and the crystallization curve of Si-Beta zeolites before calcination. During the initial time of 12 h, the crystal growth is very fast. The sample is almost entirely amorphous at the time of 3 h and the relative crystallinity is only 6%. The crystallinity increases rapidly to 92% at the time of 12 h. Afterthat the crystallinity increases slowly to 100% at the time of 48 h. The time for full crystallization of Si-Beta is shorter than that reported in literature (4 days) due to the promotion effect of seeds.22 During the whole crystallization, no other crystalline phase is observed except for the *BEA topology of Beta zeolite.

(a)

Intensity (a.u.)

48 h

24 h

12 h 9h 6h 4h 3h 10

20

30

40

50

2θ (°)

100

(b)

80

Crystallinity (%)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

12 h

60 40 20 0 0

10

20

30

40

50

Crystallization time (h)


Page 10 of 39

Page 11 of 39 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 1. (a) XRD patterns for the as-synthesized Si-Beta with different crystallization time, and (b) the corresponding crystallization curve. Silanol defect sites of Si-Beta with different crystallization time were measured with FT-IR spectroscopy of hydroxyl region (Figure 2a). The amount of hydroxyl groups including the external silanols (3738 cm 1)13,25,26,38 and the internal silanols (3520 cm 1)13,24,26 decreases gradually with the increase of crystallization time (Table S1). It suggests that the silanol defect sites of Si-Beta reduced and the connectivity of the framework structure became more integrate as the crystallinity increased. The decrease of the amount of hydroxyl groups is quick at the crystallization time in the range of 4 12 h. When the time was further prolonged, the decrease of the hydroxyl groups is not obvious. Figure 2b shows the plot of the relative amount of hydroxyl groups versus the crystallinity of Si-Beta. The linear correlation between these two parameters was observed. The hydroxyl groups will play an important role for incorporation of Sn4+ to Si-Beta in the next stannation procedure.

29

Si MAS NMR

(Figure S1) further indicates that the amount of Q3 silanols (Si(-OSi-)3OH) decreased rapidly with the increase of crystallization time. Silicate species reacted with silanol defect sites resulting in the growth of crystal.39 On the other hand, these reactive silanol defect sites can provide active sites for incorporation of other heteroatom into the framework of zeolite.



3738

4h 6h 9h 12 h 24 h

(a)

Absorbance (a.u.)

3520

4000

3800

3600

3400

3200

3000

-1

Wavenumber (cm )

(b)

120

Amount of OH (a.u.)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

100

80 2

R = 0.906 60

40 30

40

50

60

70

80

90

100

Crystallinity (%)

Figure 2. (a) FT-IR spectra of hydroxy region of Si-Beta with different crystallization time, (b) the relative amount of hydroxyl groups versus crystallinity of Si-Beta. Synthesis and Characterization of Sn-Beta Zeolites. XRD patterns of Sn-Beta zeolites are presented in Figure 3. The crystallinity of Sn-Beta zeolites decreases as compared to the corresponding parent Si-Beta zeolites (Figure S2 and Table 1). In addition, the crystallinity also decreases with the increase of Sn content. The effect of grinding on the crystallinity of Si-Beta was studied (Figure S3). It can be seen that grinding could result in the decrease of crystallinity. So, the decrease of the crystallinity of Sn-Beta is mainly due to the grinding. For all the samples, no diffraction peaks attributed to SnO2 are observed, indicating that Sn species are highly


Page 12 of 39

Page 13 of 39

dispersed.

5Sn-Beta-9h

Intensity (a.u.)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Sn-Beta-24h

Sn-Beta-12h Sn-Beta-9h Sn-Beta-6h Sn-Beta-4h 10

20

30

40

50

ο

2θ ( )

Figure 3. XRD patterns of calcined Sn-Beta zeolites. Table 1. Relative Crystallinity of Calcined Si-Beta and Sn-Beta Zeolites sample

crystallinity (%)

sample

crystallinity (%)

Si-Beta-4h

32

Sn-Beta-4h

22

Si-Beta-6h

38

Sn-Beta-6h

28

Si-Beta-9h

62

Sn-Beta-9h

49

5Sn-Beta-9h

40

Si-Beta-12h

94

Sn-Beta-12h

61

Si-Beta-24h

100

Sn-Beta-24h

72

SEM images in Figure 4 indicate that Sn-Beta-xh samples (a-f) have the morphology of lump with several hundred nanometers. Many small crumbes adhere to the large lumps. The lumps and the crumbes are formed during grinding because Si-Beta (Figure 4g) has the morphology of capped square bipyramidal (CSBP)



shape.22 The crystal size of all Sn-Beta-xh samples is comparable and at about 300 nm. Sn-Beta-F exhibits plate-like CSBP morphology due to that Sn species in the gel changed greatly the growth rate of different crystal faces.22 The crystal size of Sn-Beta-xh is smaller than Sn-Beta-F (about 1 µm) prepared by hydrothermal route. It has been reported that the crystallization of Sn-Beta zeolite greatly depends on Si/Sn ratio and tin species retard the growth of zeolite crystal.22 The crystal size of Sn-Beta-F prepared by hydrothermal route with crystallization time of 15 days is about 1 µm. For Sn-Beta-xh, its crystal size is determined by the parent Si-Beta. Althougth the crystallization rate of Si-Beta is fast, nano-sized Si-Beta would be given by controlling the crystallization time. After incorporation of Sn to Si-Beta through the condensation of Sn precursor with silanol defect sites, Sn-Beta-xh with nano crystal size was given.


Page 14 of 39

Page 15 of 39 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 4. SEM images of Sn-Beta-4h (a), Sn-Beta-6h (b), Sn-Beta-9h (c), Sn-Beta-12h (d), Sn-Beta-24h (e), 5Sn-Beta-9h (f), Si-Beta-9h (g) and Sn-Beta-F (h).

The results of N2 physisorption of Sn-Beta zeolites are given in Table 2 and Figure S4. Sn-Beta-4h and Sn-Beta-6h with low crystallinity have low surface area and micropore volume. When the crystallization time of the parent Si-Beta was prolonged to 9 h, the values of surface area and micropore volume of Sn-Beta reached a plateau; the increase of surface area and micropore volume is slow with further increasing the crystallization time of the parent Si-Beta. It indicates that Sn-Beta with good crystal purity and high crystallinity can be obtained using Si-Beta with crystallization time of ≥9 h. The adsorption-desorption isotherms of Sn-Beta-4h and Sn-Beta-6h show apparent hysteresis loops and weak micropore characters and the BJH derived pore



Page 16 of 39

distributions exhibit abundant mesopores. It suggests that the two samples are incompletely crystallized and contain considerable amount of amorphous component. The accumulation of the crystals and the amorphous component formed the mesoporous structure. With the increase of the crystallinity of Sn-Beta-9h and Sn-Beta-12h, the surface area and the micropore volume increase accompanying with the decrease of the external surface area and the mesopore volume. The hysteresis loops disappear gradually and the isotherms become type I of microporous material. At the same time, the HK derived pore distribution shows the most probable micropore at 0.71 nm which is consistent with the twelve-membered ring pore size of BEA topology (0.66 × 0.67 nm).40 Table 2. Physical Parameters and Acidity of Sn-Beta Zeolites Lewis acid sample

SBET

external

total

(m2

surface area

volume

–1

pore

mesopore

micropore sites

–1

–1

volume (mL volume –1

–1

(mL (µmol

g )

(m2 g )

(mL g )

g )

g )

Sn-Beta-4h

243

80

0.45

0.37

0.08

61

Sn-Beta-6h

231

64

0.35

0.26

0.09

60

Sn-Beta-9h

422

62

0.33

0.14

0.19

67

Sn-Beta-12h

413

39

0.27

0.08

0.19

–

Sn-Beta-24h

443

55

0.26

0.06

0.20

–

Si-Beta-9h

421

62

0.37

0.16

0.21

–

5Sn-Beta-9h

346

53

0.28

0.13

0.15

98

Sn-Beta-AT

396

48

0.26

0.08

0.18

115

Sn-Beta-P

435

98

0.31

0.14

0.17

143

Sn-Beta-F

496

72

0.31

0.09

0.22

103

a

Calculating according to the equation given in literature.41


g 1)a

Page 17 of 39 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


CD3CN is considered to be an efficient and sensitive probe molecule to detect different Sn sites and their Lewis acidity.42‒44 FT-IR spectroscopy of CD3CN (Figure 5 and Figure S5) was performed to determine the state of Sn in the prepared Sn-Beta zeolites. Sn-Beta-4h, Sn-Beta-6h and Sn-Beta-9h prepared from Si-Beta with lower crystallinity show two absorption peaks at ~2310 and ~2274 cm 1. The band at ~2274 cm 1 is attributed to the vibration of CD3CN adsorbed on silanols.35,43,45 The intensity of this adsorption decreases with the crystallinity of Si-Beta, indicating the reduction of silanol defect sites with prolonging the crystallization time. This coincides with the above results of FT-IR spectroscopy of hydroxyl region. The peak at ~2310 cm

1

is

ascribed to CD3CN adsorbed on the isolated framework tin sites.35,41‒45 The presence of this band strongly suggests tin atom was incorporated in the framework position. However, for Sn-Beta-12h and Sn-Beta-24h prepared from Si-Beta with higher crystallinity, this band is very weak. It implies that the amount of Sn incorporated into the framework is very little. The intensity of the peak at ~2310 cm

1

increased with

the increase of Sn content for 5Sn-Beta-9h, meaning that more Sn atoms were introduced to the framework. The amount of framework Sn sites of prepared Sn-Beta was calculated from CD3CN FT-IR spectroscopy according to the method reported by Gounder and coworkers (Table S2).41 The amount of framework Sn sites for Sn-Beta-4h, Sn-Beta-6h and Sn-Beta-9h is comparable and in the range of 10‒14 µmol g 1 which is lower than Sn-Beta-F. This means more extraframework Sn species in the Sn-Beta prepared by the present method.



2274 0.02

Absorbance (a.u.)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Sn-Beta-4h Sn-Beta-9h Sn-Beta-24h 5Sn-Beta-9h 2310

2340

2320

2300

2280

2260

2240

2220

2200

-1

Wavenumber (cm )

Figure 5. FT-IR spectra of CD3CN adsorption over Sn-Beta-4h, Sn-Beta-9h, Sn-Beta-24h and 5Sn-Beta-9h. The spectra were obtained at room temperature after desorption for 15 min under vacuum. For Sn-Beta zeolites with successful incorporation of Sn sites, detailed characterization was performed further. UV-vis DR spectra of Sn-Beta, Si-Beta and SnO2/Si-Beta are given in Figure 6a and Figure S6. Si-Beta shows very weak absorption. SnO2/Si-Beta with exclusive nonframework Sn species exhibits a weak and wide absorption band. Differently, Sn-Beta samples show a strong absorption at about 200 nm which is ascribed to isolated Sn4+ in tetrahedral coordination.13,27,34 This implies that Sn was introduced to the framework position. Moreover, the intensity of the band becomes strong with the content of Sn, indicating that more Sn was incorporated into the framework. The existing states of Sn species in Sn-Beta-9h and SnO2/Si-Beta are also analyzed by XPS (Figure 6b). Two peaks at 487.8 and 496.1 eV were found for Sn-Beta-9h, which were attributed to Sn 3d5/2 and Sn 3d3/2 photoelectrons of framework tin sites, respectively. Two bands at lower binding energy for SnO2/Si-Beta was found, which


Page 18 of 39

Page 19 of 39

are characteristic of Sn sites of crystalline tin dioxide.21,46,47 The results prove again that Sn was incorporated into the framework position in Sn-Beta-9h.

(a)

Absorbance (a.u.)

Si-Beta-9 h Sn-Beta-9 h 5 wt.% Sn-Beta-9 h SnO2/Si-Beta-9 h

200

300

400

500

600

700

800

Wavelength (nm)

487.8

SnO2/Si-Beta-9h

Intensity (CPS)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Sn-Beta-9h 496.1 1000 Sn 3d3/2

505

500

495

490

(b)

Sn 3d5/2

485

480

475

Binding energy (eV)

Figure 6. (a) UV-vis DR spectra of Sn-Beta-9h, Si-Beta-9h and SnO2/Si-Beta-9h. (b) XPS spectra of Sn 3d in Sn-Beta-9h and SnO2/Si-Beta-9h.

The acidity generated by Sn incorporation into the framework was investigated by FT-IR spectroscopy of pyridine (Figure 7 and Figure S7). Peak at ~1545 cm 1 is not observed, indicating that no Brønsted acid sites present in these samples. The peaks at



1446 and 1598 cm

1

correspond to hydrogen-bonded pyridine,24 which are the only

bands found for SnO2/Si-Beta. For Sn-Beta, other three peaks at 1451, 1491 and 1608 cm 1 are also observed, which are ascribed to the vibration of pyridine on Lewis acid sites.24,48,49 Based on the area of the peak at 1451 cm 1, the density of Lewis acid sites was calculated (Table 2). The density of Lewis acid sites of Sn-Beta-4h, Sn-Beta-6h and Sn-Beta-9h is comparable, which is lower than 5Sn-Beta-9h due to their lower amount of framework Sn.

1451 1446 1608 1598 1491

Absorbance (a.u.)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 20 of 39

4h 6h 9h

SnO2/Si-Beta

1650

1600

1550

1500

1450

1400

-1

Wavenumber (cm )

Figure 7. FT-IR spectra of pyridine adsorbed on Sn-Beta-xh and SnO2/Si-Beta after evacuation at 100 oC for 30 min. Mechanism

of

Sn

Incorporation.

Postsynthesis

method

of

dealumination/desilication-stannation is often used to prepare Sn-Beta zeolite.21,24-28 The method makes Al-Beta dealuminate/desilicate with acid/base to generate vacant T nests and then incorporates Sn to the framework through the interaction of Sn precursor with the silanols. In the present work, Si-Beta synthesized in fluoride media is directly used as the parent for Sn incorporation. The above results indicate that only


Page 21 of 39

Si-Beta without full crystallization (crystallinity lower than 90%) can act as an effective parent for Sn incorporation. Such incompletely crystallized Si-Beta possesses a considerable amount of silanols (Figure 2). It is believed that these silanols can condense with Sn precursor and thus Sn is incorporated into the framework sites. FT-IR spectroscopy of hydroxyl region of Si-Beta-9h and Sn-Beta-9h is shown in Figure 8. The bands at 3738 and 3520 cm−1 represent external and internal silanols, respectively.26,43 The difference spectrum of the two samples clearly shows that these bands decreased in intensity after the reaction of SnCl4·5H2O with Si-Beta-9h, indicating SnCl4·5H2O interacted with silanols and Sn4+ was incorporated into the framework sites.

3738

Absorbance (a.u.)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


3520

(a) (b) (a)-(b) 4000

3800

3600

3400

3200

3000

-1

Wavenumber (cm )

Figure 8. FT-IR spectra of hydroxyl region. (a) Si-Beta-9h, (b) Sn-Beta-9h and their difference spectrum. Stannation of Si-Beta with High Crystallinity to Synthesize Sn-Beta. The above results show that the introduction of tin atom into the framework of Si-Beta with high crystallinity (> 90%) is difficult due to the lack of adequate silanols. According to the mechanism of Sn incorporation, we expect that if more silanols can be generated on



Si-Beta with high crystallinity, Sn will be incorporated into its framework successfully. Our previous work indicates that organic base can make zeolite desilicate and at the same time preserve the crystalline structure well.13 Therefore, TEAOH, a frequently-used structure-directing agent,22,50 was employed to desilicate Si-Beta-12h. After desilication (Si-Beta-AT) the amount of silanols (3738 and 3520 cm 1) increased significantly as can be seen from Figure S8, which offers a condition for Sn incorporation into the framework sites. XRD pattern (Figure S9) shows that Sn-Beta-AT prepared from Si-Beta-AT is in pure *BEA phase but its crystallinity is lower than Sn-Beta-12h. This indicates desilication destroyed the framework structure to some extent. The morphology of Sn-Beta-AT (Figure S10) is similar with Sn-Beta-12h, but there are more small crumbes due to desilication. The result of N2 physisorption in Table 2 shows that the surface area and the pore volume of Sn-Beta-AT are comparable with Sn-Beta-12h. FT-IR spectra of CD3CN on Sn-Beta-AT are given in Figure 9. The much stronger absorption band at ~2276 cm

1

for Sn-Beta-AT than for Sn-Beta-12h (Figure S5)

proves again that a large number of silanols are generated after desilication. In contrast to Sn-Beta-12h, Sn-Beta-AT presents a strong absorption peak at 2312 cm 1, meaning that Sn-Beta-AT has a large amount of framework Sn sites. These results prove the efficiency of the desilication-stannation method for introduction of tin atom into the framework of Si-Beta with high crystallinity. The amount of Lewis acid sites of Sn-Beta-AT determined by pyridine FT-IR spectra (Figure S11) is given in Table 2. The density of Lewis acid of Sn-Beta-AT is higher than those of Sn-Beta-xh prepared


Page 22 of 39

Page 23 of 39

directly from Si-Beta-xh due to its high content of framework Sn.

2312

2276

5 min 10 min 15 min 20 min 25 min 30 min

0.02 Absorbance (a.u.)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


2340

2320

2300

2280

2260

2240

2220

2200

-1

Wavenumber (cm )

Figure 9. FT-IR spectra of CD3CN adsorption on Sn-Beta-AT. The spectra were obtained at room temperature with different desorption time under vacuum. Catalytic Performance. The catalytic property of the prepared Sn-Beta zeolites was studied in the conversion of sugars to alkyl lactates in alcohol, which is a promising and challenging process of biomass transformation.9‒14,51 First, the cheap and abundant glucose was used as a substrate and methanol was used as a solvent. The yield of MLA is shown in Figure 10. Si-Beta and SnO2/Si-Beta gave the same MLA yields as in the blank experiment. Sn-Beta-xh prepared in the present work by stannation of Si-Beta-xh gave much higher MLA yield as compared with SnO2/Si-Beta. It proves that Lewis acid sites generated by the framework Sn sites are the active sites for the transformation of glucose to MLA. The yield of MLA decreased with the increase of the crystallinity; especially for Sn-Beta-12h and Sn-Beta-24h prepared from Si-Beta with crystallinity higher than 90%, no more than 20% of MLA yield was obtained. It has been shown above that only a little amount of Sn was introduced to the framework position for Sn-Beta-12h and Sn-Beta-24h, thus



Page 24 of 39

low MLA yield was given using the two samples as catalyst. Sn-Beta-AT with considerable amount of framework Sn sites and high amount of Lewis acid sites gave much higher MLA yield than Sn-Beta-12h, proving again the important role of framework Sn sites for the formation of MLA. Recently, Hammond group reported that

the

hierarchically

Sn-Beta

zeolite

showed

high

activity

in

Meerwein–Pondorf–Verley transfer hydrogenation of bulky ketone and the mesopore was able to bring exceptional stability as compared with purely microporous Sn-Beta.16 Nanosized Sn-Beta-9h has higher external surface area and larger mesopore volume as compared with Sn-Beta-AT. Therefore, Sn-Beta-9h gave higher MLA yield than Sn-Beta-AT, whereas the density of Lewis acid sites was much higher in the latter. The yields of MLA over Sn-Beta-4h, Sn-Beta-6h and Sn-Beta-9h were also higher than over Sn-Beta-F and Sn-Beta-P. The possible reason is that nano-sized Sn-Beta-xh has higher mesoporosity, and thus most of these sites can be accessed by reactant easily. For Sn-Beta-F, some Sn sites in the inner core of the crystal are difficult to be accessed by glucose. In addition, the larger crystal size and the lower mesopore volume of Sn-Beta-F are disadvantageous for the formation of MLA. Sn-Beta-P synthesized by post-synthesis method has a large amount of silanol defects than Sn-Beta-F as reported in our recent study.13 It was reported that more silanol defects would bring the decrease of reaction rate of the transformation of fructose to C3 compounds although Sn-Beta-P was more active for the isomerization of glucose to fructose.8,13 So, low MLA yield was given on Sn-Beta-P for the transformation of glucose to MLA.


Page 25 of 39

Turnover frequency (TOF) was applied to study the intrinsic and initial activity of active Sn sites. The TOF values for different catalysts calculated based on the amount of framework Sn sites at low MLA yield (Table S2). TOF values varied in the order of nano Sn-Beta-xh >> Sn-Beta-F >> Sn-Beta-P ≈ Sn-Beta-AT. It is almost in accordance with the order of MLA yield at 10 h. The time course on the yield of MLA over Sn-Beta-9h, Sn-Beta-F and Sn-Beta-P is shown in Figure S12. It can be seen that MLA yield over nano-sized Sn-Beta-9h increased significantly in all the reaction time. The yield of MLA over Sn-Beta-F and Sn-Beta-P reached a plateau at a short reaction time. The high MLA yield using Sn-Beta-9h as catalyst is due to its higher mesoporosity as discussed above.

50

40

Yield of MLA (%)

30

20

10

0

Bl an Si k S i -B et O a 2 /S i-B Sn e -B ta et Sn a-4 -B h e Sn ta-6 -B h e Sn ta-B 9h e Sn ta-1 -B 2h e 5S ta-2 n- 4h Be Sn ta-9 -B h et aSn AT -B e Sn ta-F -B et aP

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 10. Reaction results of glucose to MLA over different catalysts. Reaction conditions: glucose (0.124 g), methanol (5 mL), catalyst (80 mg), 0.5 MPa N2, 160 oC, 10 h.



The prepared Sn-Beta-9h with relatively higher crystallinity and better catalytic performance was also studied for the transformation of other carbohydrates to MLA (Table 3). All carbohydrates were completely converted under investigated reaction conditions. The yields of MLA from four hexoses follow the order of sucrose > fructose > glucose > mannose, which is similar with that reported in literature.10 DHA can be easily converted to MLA even at 40 oC as reported previously.12,43 Replacing methanol with ethanol or n-butanol, the yield of alkyl lactate reduced, whereas the alkyl lactate yield using sucrose as substrate is always higher than from glucose. It is ascribed to its gradual degradation and thus low concentration of sugars in the reaction media, which reduced the side reactions.52 Table 3. Yield of Alkyl Lactate from Different Carbohydrates and Solventsa substrate

solvent

yield of alkyl lactate (%)

Fructose

methanol

47

Mannose

methanol

39

Sucrose

methanol

57

DHAb

methanol

80

Glucose

ethanol

29

Glucose

n-butanol

20

Sucrose

ethanol

37

Sucrose

n-butanol

31

a

Reaction conditions: carbohydrate (0.124 g), Sn-Beta-9h (80 mg), alcohol (5 mL),

0.5 MPa N2, 160 oC, 10 h. bReaction conditions: methanol solution of DHA (5 mL, 0.26 mol L−1), catalyst (0.133 g), 40 oC, 24 h.


Page 26 of 39

Page 27 of 39 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


It has been reported that alkali ions can promote the formation of MLA from carbohydrates catalyzed by Sn-containing silicates.11,53 The content of sodium and potassium content in template and nano-sized Sn-Beta was analyzed (Table S3). Main sodium with a few potassium ions was detected in the samples. Further, the effect of the amount of potassium salt (KBr), an efficient promoter among alkali salts,11 on the reaction was studied over Sn-Beta-9h and Sn-Beta-P (Table S4). Potassium salt showed notable promotion effect on the formation of MLA from glucose over Sn-Beta-P while weak promotion effect was found over Sn-Beta-9h. Finally, the reusability of Sn-Beta-9h was investigated. After each run, the sample was washed with methanol, dried, and calcined at 550 oC for 5 h to burn away deposited carbon and used in the next run. As shown in Figure 11, the yield of MLA has no decrease after eight runs. To further study the catalyst stability, the conversion of glucose catalyzed by fresh Sn-Beta-9h and Sn-Beta-9h after recycling for eight runs was done at 160 oC for 1 h; 27% and 28% yield of MLA was given over the two catalysts, respectively. Additionally, a hot filtration experiment was done. Zeolite was separated from the reaction mixture after reaction at 160 oC for 1 h. The yield of MLA had no increase (28%) for another reaction time of 4 h. These proofs indicate that the catalyst is highly stable in the reaction. The reusability of Sn-Beta-9h is superior to Sn-Beta synthesized by hydrothermal route and hierarchical Sn-Beta zeolite in literature.9,13 The high stability of Sn-Beta-9h is attributed to its special distribution of Sn. Large external surface area and the large mesopore volume of Sn-Beta-9h make the tin sites easy to be utilized in the reaction; moreover, the deposited carbon can be



easily removed via calcination to regenerate the active tin sites as compared with Sn-Beta-F. XRD pattern of the reused Sn-Beta-9h is exhibited in Figure S13a, which proves that BEA structure is kept well although the crystallinity decreases slightly. Meanwhile, the peak at 2310 cm

1

in FT-IR spectra of CD3CN adsorption (Figure

S13b) clearly shows that the framework Sn sites are stable during the reaction.

50

40 Yield of MLA (%)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

30

20

10

0 1

2

3

4

5

6

7

8

Reaction runs

Figure 11. Recyclability of Sn-Beta-9h in the conversion of glucose. Glucose (0.372 g), catalyst (0.240 g) and methanol (15 mL) was used. The other reaction conditions are similar with those in Figure 10.

CONCLUSIONS Sn-Beta zeolite with nano size can be prepared rapidly through stannation of all-silica Beta zeolite. The crystallinity of Si-Beta strongly affects the introduction of tin to the framework sites. Si-Beta with lower crystallinity has a considerable amount of silanols which can react with Sn precursor to incorporate Sn into the framework sites. Si-Beta with higher crystallinity possesses less silanols and thus it is difficult for the incorporation of Sn, but a large amount of silanols can be generated by desilication.


Page 28 of 39

Page 29 of 39 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


The nano-sized Sn-Beta zeolites are highly active for the conversion of glucose to MLA. 48% of MLA yield can be obtained, which is higher than over Sn-Beta-P (22%) and Sn-Beta-F (35%). TOF values varied in the order of nano Sn-Beta >> Sn-Beta-F >> Sn-Beta-P. The high MLA yield using nano Sn-Beta as catalyst is due to its higher mesoporosity. The catalyst shows high stability which is used for eight cycles without decrease of MLA yield. Potassium salt showed notable promotion effect on the formation of MLA from glucose over Sn-Beta-P while weak promotion effect was found over nano-sized Sn-Beta-9h.

ASSOCIATED CONTENT Supporting Information Additional results including

29

Si MAS NMR, XRD, N2 physisorption, FT-IR spectra

of CD3CN and pyridine adsorption, FT-IR spectra of hydroxyl region, UV-vis DR spectra, SEM, ICP and some reaction results were listed in the Supporting Information. This material is available free of charge via the Internet at http://pubs.acs.org.

AUTHOR INFORMATION Corresponding Author *Tel.: +86 371 67781780; E-mail addresses: [email protected] Notes The authors declare no competing financial interest.

ACKNOWLEDGMENTS This work was supported by the National Natural Science Foundation of China



Page 30 of 39

(21503192), the State Key Laboratory of Catalysis in DICP (N-16-02), the Outstanding Young Talent Research Fund of Zhengzhou University (1521316006) and the Undergraduate Innovation Education Project of Zhengzhou University (2017cxcy058).

REFERENCES (1) Luo, H. Y.; Lewis, J. D.; Román-Leshkov, Y. Lewis Acid Zeolites for Biomass Conversion: Perspectives and Challenges on Reactivity, Synthesis, and Stability. Annu.

Rev.

Chem.

Biomol.

Eng.

2016,

7,

663−692,

DOI

10.1146/annurev-chembioeng-080615-034551. (2) Dapsens, P. Y.; Mondelli, C.; Pérez-Ramírez, J. Design of Lewis-acid Centres in Zeolitic Matrices for the Conversion of Renewables. Chem. Soc. Rev. 2015, 44, 7025–7043, DOI 10.1039/c5cs00028a. (3) Ferrini, P.; Dijkmans, J.; De Clercq, R.; Van de Vyver, S.; Dusselier, M.; Jacobs, P. A.; Sels, B. F. Lewis Acid Catalysis on Single Site Sn Centers Incorporated into Silica

Hosts.

Coordin.

Chem.

Rev.

2017,

343,

220–255,

DOI

10.1016/j.cct.2017.05.010. (4) Moliner, M. State of the Art of Lewis Acid-Containing Zeolites: Lessons from Fine Chemistry to New Biomass Transformation Processes. Dalton Trans. 2014, 43, 4197–4208, DOI 10.1039/c3dt52293h. (5) Delidovich, I.; Palkovits, R. Catalytic Isomerization of Biomass-Derived Aldoses: A Review. ChemSusChem 2016, 9, 547–561, DOI 10.1002/cssc.201501577. (6) Moliner, M.; Román-Leshkov, Y.; Davis, M. E. Tin-Containing Zeolites Are


Page 31 of 39 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Highly Active Catalysts for the Isomerization of Glucose in Water. Proc. Natl. Acad. Sci. USA. 2010, 107, 6164–6168, DOI 10.1073/pnas.1002358107. (7) Gunther, W. R.; Wang, Y.; Ji, Y.; Michaelis, V. K.; Hunt, S. T.; Griffin, R. G.; Román-Leshkov, Y. Sn-Beta Zeolites with Borate Salts Catalyse the Epimerization of Carbohydrates via an Intramolecular Carbon Shift. Nature Commun. 2012, 3, 1109, DIO 10.1038/ncomms2122. (8) Jiang L.; Zhou, L.; Chao, J.; Zhao, H.; Lu, T.; Su, Y.; Yang X.; Xu, J. Direct Catalytic Conversion of Carbohydrates to Methyl Levulinate: Synergy of Solid Brønsted Acid and Lewis Acid. Appl. Catal. B 2018, 220, 589–596, DIO 10.1016/j.apcatb.2017.08.072. (9) Holm, M. S.; Saravanamurugan, S.; Taarning, E. Conversion of Sugars to Lactic Acid Derivatives Using Heterogeneous Zeotype Catalysts. Science 2010, 328, 602–605, DOI 10.1126/science.1183990. (10) Holm, M. S.; Pagán-Torres, Y. J.; Saravanamurugan, S.; Riisager, A.; Dumesic J. A.; Taarning, E. Sn-Beta Catalysed Conversion of Hemicellulosic Sugars. Green Chem. 2012, 14, 702–706, DOI 10.1039/c2gc16202d. (11) Tolborg, S.; Sádaba, I.; Osmundsen, C. M.; Fristrup, P.; Holm, M. S.; Taarning, E. Tin-containing Silicates: Alkali Salts Improve Methyl Lactate Yield from Sugars. ChemSusChem 2015, 8, 613–617, DOI 10.1002/cssc.201403057. (12) Osmundsen, C. M.; Holm, M. S.; Dahl, S.; Taarning, E. Tin-Containing Silicates: Structure-Activity Relations. Proc. R. Soc. A 2012, 468, 2000–2016, DOI 10.1098/rspa.2012.0047.



Page 32 of 39

(13) Yang, X.; Bian, J.; Huang, J.; Xin, W.; Lu, T.; Chen, C.; Su, Y.; Zhou, L.; Wang, F.; Xu, J. Fluoride-Free and Low Concentration Template Synthesis of Hierarchical Sn-Beta Zeolites: Efficient Catalysts for Conversion of Glucose to Alkyl Lactate. Green Chem. 2017, 19, 692–701, DOI 10.1039/c6gc02437h. (14) Zhang, J.; Wang, L.; Wang, G.; Chen, F.; Zhu, J.; Wang, C.; Bian, C.; Pan, S.; Xiao, F. Hierarchical Sn-Beta Zeolite Catalyst for the Conversion of Sugars to Alkyl Lactates. ACS Sustainable Chem. Eng. 2017, 5, 3123–3131, DOI 10.1021/acssuschemeng.6b02881. (15) Corma, A.; Domine, M. E.; Valencia, S. Water-Resistant Solid Lewis Acid Catalysts: Meerwein–Ponndorf–Verley and Oppenauer Reactions Catalyzed by Tin-Beta

Zeolite.

J.

Catal.

2003,

215,

294–304,

DOI

10.1016/S0021-9517(03)00014-9. (16) Al-Nayili, A.; Yakabi K.; Hammond C. Hierarchically Porous BEA Stannosilicates as Unique Catalysts for Bulky Ketone Conversion and Continuous Operation. J. Mater. Chem. A 2016, 4, 1373–1382, DOI 10.1039/c5ta08709k. (17) Boronat, M.; Concepción, P.; Corma, A.; Renz, M.; Valencia, S. Determination of the Catalytically Active Oxidation Lewis Acid Sites in Sn-Beta Zeolites, and Their Optimisation by the Combination of Theoretical and Experimental Studies. J. Catal. 2005, 234, 111–118, DOI 10.1016/j.jcat.2005.05.023. (18) Dijkmans, J.; Schutyser, W.; Dusselier, M.; Sels, B. F. Snβ-Zeolite Catalyzed Oxido-Reduction Cascade Chemistry with Biomass-Derived Molecules. Chem. Commun. 2016, 52, 6712–6715, DOI 10.1039/c6cc00199h.


Page 33 of 39 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(19) de Vyver, S. V.; Odermatt, C.; Romero, K.; Prasomsri, T.; Román-Leshkov, Y. Solid Lewis Acids Catalyze the Carbon−Carbon Coupling between Carbohydrates and Formaldehyde. ACS Catal. 2015, 5, 972−977, DOI 10.1021/cs5015964. (20) Su, M.; Li, W.; Zhang, T.; Xin, H.; Li, S.; Fan, W.; Ma, L. Production of Liquid Fuel Intermediates from Furfural via Aldol Condensation over Lewis Acid Zeolite Catalysts. Catal. Sci. Technol. 2017, 7, 3555–3561, DOI 10.1039/c7cy01028a. (21) Tang, B.; Dai, W.; Wu, G.; Guan, N.; Li, L.; Hunger, M. Improved Postsynthesis Strategy to Sn-Beta Zeolites as Lewis Acid Catalysts for the Ring-Opening Hydration of Epoxides. ACS Catal. 2014, 4, 2801−2810, DOI 10.1021/cs500891s. (22) Tolborg, S.; Katerinopoulou, A.; Falcone, D. D.; Sádaba, I.; Osmundsen, C. M.; Davis, R. J.; Taarning, E.; Fristrup, P.; Holm, M. S. Incorporation of Tin Affects Crystallization, Morphology, and Crystal Composition of Sn-Beta. J. Mater. Chem. A 2014, 2, 20252–20262, DOI 10.1039/c4ta05119j. (23) Yakimov, A. V.; Kolyagin, Y. G.; Tolborg, S.; Vennestrøm P. N. R.; Ivanova, I. I. Accelerated Synthesis of Sn-BEA in Fluoride Media: Effect of H2O Content in the Gel. New J. Chem. 2016, 40, 4367–4374, DOI 10.1039/c6nj00394j. (24) Li, P.; Liu, G.; Wu, H.; Liu, Y.; Jiang, J.; Wu, P. Postsynthesis and Selective Oxidation Properties of Nanosized Sn-Beta Zeolite. J. Phys. Chem. C 2011, 115, 3663–3670, DOI 10.1021/jp1076966. (25) Dijkmans, J.; Gabriëls, D.; Dusselier, M. de Clippel, F.; Vanelderen, P.; Houthoof, K.; Malfliet, A.; Pontikes Y.; Sels, B. F. Productive Sugar Isomerization with Highly Active Sn in Dealuminated β Zeolites. Green Chem. 2013, 15, 2777–2785,



DOI 10.1039/c3gc41239c. (26) Vega-Vila, J. C.; Harris, J. W.; Gounder, R. Controlled Insertion of Tin Atoms into Zeolite Framework Vacancies and Consequences for Glucose Isomerization Catalysis. J. Catal. 2016, 344, 108–120, DOI 10.1016/j.jcat.2016.09.011. (27) Dapsens, P. Y.; Mondelli, C.; Pérez-Ramírez, J. Alkaline-Assisted Stannation of Beta Zeolite as a Scalable Route to Lewis-Acid Catalysts for the Valorisation of Renewables. New J. Chem. 2016, 40, 4136–4139, DOI 10.1039/c5nj01834j. (28) Hammond, C.; Conrad, S.; Hermans, I. Simple and Scalable Preparation of Highly Active Lewis Acidic Sn-β. Angew. Chem. Int. Ed. 2012, 51, 11736–11739, DOI 10.1002/anie.201206193. (29) Yao, J.; Fu, K.; Wang, Y.; Li, T.; Liu, H.; Wang, J. Hierarchically Porous Sn-β Zeolites via an OSDA-Free Synthesis. Green Chem. 2017, 19, 3214–3218, DOI 10.1039/c7gc01040k. (30) Gounder, R.; Davis, M. E. Beyond Shape Selective Catalysis with Zeolites: Hydrophobic Void Spaces in Zeolites Enable Catalysis in Liquid Water. AIChE J. 2013, 59, 3349–3358, DOI 10.1002/aic.14016. (31) Dijkmans, J.; Dusselier, M., Janssens, W.; Trekels, M.; Vantomme, A.; Breynaert, E.; Kirschhock, C.; Sels, B. F. An Inner/Outer-Sphere Stabilized Sn Active Site in Beta Zeolite: Spectroscopic Evidence and Kinetic Consequences. ACS Catal. 2016, 6, 31–46, DOI 10.1021/acscatal.5b01822. (32) Wolf, P.; Valla, M.; Nunez-Zarur, F.; Comas-Vives, A.; Rossini, A. J.; Firth, C.; Kallas, H.; Lesage, A.; Emsley, L.; Copéret, C.; Hermans, I. Correlating Synthetic


Page 34 of 39

Page 35 of 39 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Methods, Morphology, Atomic-level Structure and Catalytic Activity of Sn-β Catalysts. ACS Catal. 2016, 6, 4047–4063, DOI 10.1021/acscatal.6b00114. (33) Chang, C.; Wang, Z.; Dornath, P.; Cho, H. J.; Fan, W. Rapid Synthesis of Sn-Beta for the Isomerization of Cellulosic Sugars. RSC Adv. 2012, 2, 10475–10477, DOI 10.1039/c2ra21381h. (34) Kang, Z.; Zhang, X.; Liu, H.; Qiu, J.; Yeung, K. L. A Rapid Synthesis Route for Sn-Beta Zeolites by Steam-Assisted Conversion and Their Catalytic Performance in Baeyer–Villiger Oxidation. Chem. Eng. J. 2013, 218, 425–432, DOI 10.1016/j.cej.2012.12.019. (35) Chang, C.; Cho, H. J.; Wang, Z.; Wang, X.; Fan, W. Fluoride-Free Synthesis of a Sn-BEA Catalyst by Dry Gel Conversion. Green Chem. 2015, 17, 2943–2951, DOI 10.1039/c4gc02457e. (36) Iida, T.; Takagaki, A.; Kohara, S.; Okubo, T.; Wakihara, T. Sn-Beta Zeolite Catalysts with High Sn Contents Prepared from Sn–Si Mixed Oxide Composites. ChemNanoMat 2015, 1, 155–158, DOI 10.1002/cnma.201500038. (37) Zhu, Z.; Xu, H.; Jiang, J.; Guan, Y.; Wu, P. Sn-Beta Zeolite Hydrothermally Synthesized via Interzeolite Transformation as Efficient Lewis Acid Catalyst. J. Catal. 2017, 352, 1–12, DOI 10.1016/j.jcat.2017.04.031. (38) Zhu, Z.; Xu, H.; Jiang, J.; Wu, H.; Wu, P. Hydrophobic Nanosized All-silica Beta Zeolite: Efficient Synthesis and Adsorption Application. ACS Appl. Mater. Interfaces 2017, 9, 27273–27283, DOI 10.1021/acsami.7b06173. (39) Burkett, S. L.; Davis, M. E. Mechanism of Structure Direction in the Synthesis of



Pure-Silica Zeolites. 2. Hydrophobic Hydration and Structural Specificity. Chem. Mater. 1995, 7, 1453–1463, DOI 10.1021/cm00056a009. (40) Xu, R.; Pang, W.; Huo, Q. Chemistry of Zeolites and Related Porous Materials. 2nd edition, Beijing, Science Press, 2014, P164. (41) Harris, J. W.; Cordon, M. J.; Iorio, J. R. D.; Vega-Vila, J. C.; Ribeiro, F. H.; Gounder, R. Titration and Quantification of Open and Closed Lewis Acid Sites in Sn-Beta Zeolites that Catalyze Glucose Isomerization. J. Catal. 2016, 335, 141–154, DOI 10.1016/j.jcat.2015.12.024. (42) Roy, S.; Bakhmutsky, K.; Mahmoud, E.; Lobo, R. F.; Gorte, R. J. Probing Lewis Acid Sites in Sn-Beta Zeolite. ACS Catal. 2013, 3, 573−580, DOI 10.1021/cs300599z. (43) Yang, X.; Wu, L.; Wang, Z.; Bian, J.; Lu, T.; Zhou, L.; Chen C.; Xu, J. Conversion of Dihydroxyacetone to Methyl Lactate Catalyzed by Highly Active Hierarchical Sn-USY at Room Temperature. Catal. Sci. Technol. 2016, 6, 1757–1763, DOI 10.1039/c5cy01037c. (44) Wolf, P.; Hammond, C.; Conrad, S.; Hermans, I. Post-Synthetic Preparation of Sn-, Ti- and Zr-Beta: A Facile Route to Water Tolerant, Highly Active Lewis Acidic Zeolites. Dalton Trans. 2014, 43, 4514–4519, DOI 10.1039/c3dt52972j. (45) Otomo, R.; Kosugi, R.; Kamiya, Y.; Tatsumi, T., Yokoi, T. Modification of Sn-Beta Zeolite: Characterization of Acidic/Basic Properties and Catalytic Performance in Baeyer–Villiger Oxidation. Catal. Sci. Technol. 2016, 6, 2787–2795, DOI 10.1039/c6cy00532b.


Page 36 of 39

Page 37 of 39 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(46) Jennings, J. A.; Parkin, S.; Munson, E.; Delaney, S. P.; Calahan, J. L.; Isaacs, M.; Hong, K.; Crocker, M. Regioselective Baeyer–Villiger Oxidation of Lignin Model Compounds with Tin Beta Zeolite Catalyst and Hydrogen Peroxide. RSC Adv. 2017, 7, 25987–25997, DOI 10.1039/c7ra03830e. (47) Mäki-Arvela, P.; Kumar, N.; Diáz, S. F.; Aho, A.; Tenho, M.; Salonen, J.; Leino, A. R.; Kordás, K.; Laukkanen, P.; Dahl, J.; Murzin, D. Y. Isomerization of β-Pinene Oxide over Sn-modified Zeolites. J. Mol. Catal. A 2013, 366, 228–237, DIO 10.1016/j.molcata.2012.09.028. (48) van der Graaff, W. N. P.; Li, G.; Mezari, B.; Pidko, E. A.; Hensen, E. J. M. Synthesis of Sn-Beta with Exclusive and High Framework Sn Content. ChemCatChem 2015, 7, 1152–1160, DOI 10.1002/cctc.201403050. (49) Lu, T.; Fu, X.; Zhou, L.; Su, Y.; Yang, X.; Han, L.; Wang, J.; Song, C. Promotion Effect of Sn on Au/Sn-USY Catalysts for One-Pot Conversion of Glycerol to Methyl Lactate. ACS Catal. 2017, 7, 7274−7284, DOI 10.1021/acscatal.7b02254. (50) He, Z.; Wu, J.; Gao, B.; He, H. Hydrothermal Synthesis and Characterization of Aluminum-Free Mn-β Zeolite: A Catalyst for Phenol Hydroxylation. ACS Appl. Mater. Interfaces 2015, 7, 2424−2432, DOI 10.1021/am507134g. (51) Zhou, L.; Wu, L.; Li, H.; Yang, X.; Su, Y.; Lu, T.; Xu, J. A Facile and Efficient Method to Improve the Selectivity of Methyl Lactate in the Chemocatalytic Conversion of Glucose Catalyzed by Homogeneous Lewis Acid. J. Mol. Catal. A 2014, 388, 74−80, DOI 10.1016/j.molcata.2014.01.017. (52) Pang, J.; Zheng, M.; Li, X.; Song, L.; Sun, R.; Sebastian, J.; Wang, A.; Wang, J.;



Wang, X.; Zhang, T. Catalytic Conversion of Carbohydrates to Methyl Lactate Using Isolated Tin Sites in SBA-15. ChemistrySelect 2017, 2, 309–314, DOI 10.1002/slct.201601752. (53) Elliot, S.; Tolborg, S.; Madsen, R.; Taarning, E.; Meier, S. Effects of Alkali and Counter Ions in Sn-Beta Catalyzed Carbohydrate Conversion. ChemSusChem 2018, 11, 1198–1203, DOI: 10.1002/cssc.201702413.


Page 38 of 39

Page 39 of 39 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


TOC

Synopsis Nano-sized Sn-Beta was synthesized via a simple procedure which exhibited high activity and good stability in the conversion of glucose to methyl lactate.


Synthesis of Sn-Containing Nanosized Beta Zeolite As Efficient

Recommend Documents