Accepted Manuscript

Dry-gel synthesis of hierarchical TS-1 zeolite by using P123 and Polyurethanefoam as template

Ming Bo Yue, Meng Nan Sun, Fei Xie, Dan Dan Ren

PII: S1387-1811(13)00494-0DOI: http://dx.doi.org/10.1016/j.micromeso.2013.09.029Reference: MICMAT 6238

To appear in: Microporous and Mesoporous Materials

Received Date: 29 April 2013Revised Date: 19 September 2013Accepted Date: 21 September 2013

Please cite this article as: M.B. Yue, M.N. Sun, F. Xie, D.D. Ren, Dry-gel synthesis of hierarchical TS-1 zeolite byusing P123 and Polyurethane foam as template, Microporous and Mesoporous Materials (2013), doi: http://dx.doi.org/10.1016/j.micromeso.2013.09.029

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1

Dry-gel synthesis of hierarchical TS-1 zeolite by using P123 and Polyurethane foam

as template

Ming Bo Yue*, Meng Nan Sun, Fei Xie, Dan Dan Ren

Key Laboratory of Life-Organic Analysis, School of Chemistry and Chemical Engineering, Qufu

Normal University, Shandong, China；Tel: 0086-537-4458301; fax: 0086-537-4456301; E-mail:

mingboyue@126.com

Abstract

Hierarchical TS-1 zeolites have been prepared via a rapid dry-gel conversion (DGC) technique from

carbon-titanosilicate composite. The carbon-titanosilicate composite was fabricated by dipping the

silicon source, titanium source and P123 tri-block copolymer into polyurethane (PU) foam, and then

carbonized in situ. The carbon-titanosilicate composite was transformed into TS-1 zeolites by DGC

method with the aid of zeolite seeding gel. The dual carbon templates with different size obtained from

carbonation of P123 and PU were used to direct mesostructure and macroporous architectures

respectively. The resulting samples were characterized by X-ray diffraction, IR spectroscopy, SEM and

N2 adsorption to evaluate the textural properties. The hierarchical zeolites exhibits large pore volumes

(0.3–0.8 cm3 g

-1), hierarchical pore sizes (2–50 nm), and high external surface areas (158–211 m

2 g

-1).

Epoxidation of 1-hexene and cyclohexene were used as probe reaction to survey the catalytic capacity of

the resulted zeolites and this hierarchical zeolite showed well catalytic capacities to epoxidation of

cyclohexene.

Keywords: Hierarchical zeolites; Dry gel conversion; Polyurethane foam; Dual carbon template;

Epoxidation of cyclohexene

1. Introduction

2

Since the discovery of TS-1 zeolites [1], titanosilicate molecular sieves have been attracted much

attention owing to their excellent performance in the selective oxidation of organic compounds with

hydrogen peroxide under mild conditions [2-7]. However, the intricate micropores of the zeolites are not

efficient on the diffusion of bulk reactants and products, which prevent their wide use in fine chemical

and petrochemical processing [8,9]. Recently, much work focused on the improvement of the bulky

molecule diffusion in zeolites. Hierarchical porous zeolites with mesoporosity and/or macroporosity and

nanoscale zeolites with high external surface areas are alternatives to break these diffusion limitations in

the intrinsically molecular-sized micropores of zeolites [10-13]. There are a variety of methods to

prepare hierarchical zeolites, such as acid or alkali leaching treatments of zeolite crystals [14-16], hard

templating method [17-26], soft templating method [27-31], etc. Among these hard templates, carbon

materials (carbon nanotube [17], carbon black [18], mesoporous carbon CMK-1 and CMK-3 [19, 20],

carbon aerogel [21-23], colloid-imprinted carbon [24]) were most widely used to prepare hierarchical

zeolites. Especially, this hard templating method was more suitable to fabricate hierarchical

titanosilicate zeolites comparing with aluminum-containing zeolite due to the special nature of the

titanium in acid or alkali leaching treatments [32-37]. Furthermore, zeolites synthesized by conventional

techniques are usually obtained as powders. To make them suitable for practical applications, zeolites

are usually shaped into large shapes or granules with the help of inorganic binders to avoid excessive

pressure drops in fixed bed reactors and/or dusting problems. The addition of binders may result in

partial blocking of the zeolite pore system and also leads to dilution of the active species. Therefore, it

could be interesting to develop a self-supporting shaped zeolite with both uniform shape and hierarchical

structure. Especially, more attractive applications could be developed if the targeted zeolites were

constructed with hierarchical micro–meso–macropore systems. In this hierarchical structure, macropore

3

systems enhance mass transport, mesopores offer precise selectivity, and microporous zeolitic structure

provides the catalytically active sites.

Polyurethane (PU) foam has controllable skeleton macrostructure and interconnected macropores,

which is perfect well for macrocasting and building macrostructure. The PU foams have been

successfully used as template to prepare macro- and microporous silica, zeolite and bioactive glass

materials monoliths [38-45]. The ordered mesoporous carbon-silica composite monoliths and

hierarchical porous silica with ordered mesostructure were prepared by using polyurethane foam as

macroporous structure director [38, 44]. Nanosized mesoporous silica monoliths were fabricated by

casting the nano-sized silica in the ceramic foam fabricated with polyurethane foam as template [39].

Yoon prepared monolithic zeolite [40] and the aligned 2D arrays of silicalite-1 crystals [42] with

polyurethane foams and aligned polyurethane films as template respectively. Hierarchical porous

bioactive glass scaffolds were synthesized with a polyurethane foam and P123 as co-template [41]. As

reported above, the polyurethane foam can be used as template to prepare the monolith effectively.

Hydrothermal synthesis processes are usually used to convert the amorphous aluminosilicate

precursor to crystalline zeolites. However, limited by the diffusion, the growth rate of zeolite on the

surface was higher than in the inner region of the precursor in the hydrothermal treatment process. So,

the zeolite aggregated on the surface and the zeolite size distribution was not uniform. DGC method is

using steam to assist heating the precursor and converts the amorphous structure to crystal structure.

Compared with hydrothermal synthesis process, the impact of diffusion on zeolite growth rate is

minimized in DGC method, because of higher diffusion rate of gas than that of liquid. In DGC process,

no solid contacts directly with water. Usually, capillary condensation of water vapor enables the surface

of the amorphous silica gel to be covered with a thin layer of water during the steaming treatment.

4

Hence, the zeolitization of the silicate gel begin just in the micro-areas of the precursor gel. So, the

digestion of zeolite precursor and crystallization of zeolite is located in this mico-area, which is favor to

prepare nano-zeolite assembled shaped zeolite. In the synthesis of titanosilicate molecular sieves, it is

important to form tetrahedral Ti and avoid the formation of TiO2 phase. The characteristic crystallization

of DGC method (zeolitization in micro-areas) would favor maintaining the stability of the tetrahedral Ti

in the zeolite precursor.

In this report, we introduce the synthesis of hierarchical micro-meso-macroporous TS-1 architectures

by using the dual carbon templates obtained from carbonation of P123 and PU foam. The PU foam

offered the macroporous structure and the P123 directed the mesoporous structure. The amorphous wall

of titanosilicates was transformed into micropores zeolites via dry gel conversion method.

2. Experimental section

2.1 Material preparation

The chemicals used in this work were sourced commercially and used without further purification.

The polyurethane foam was purchased from Shanghai Changda Foam Co. Ltd.. Tetrapropylammonium

hydroxide (TPAOH, 25% solution) was purchased from Shanghai Cainorise Chemicals Co., Ltd.

Tetraethylorthosilicate (TEOS, AR grade), citric acid (CA, AR grade,) and titanium tetrabutoxide

(TBOT, AR grade) was purchased from the Sinopharm Chemical Reagent Co., Ltd. Pluronic triblock

copolymer P123 (EO20PO70EO20, Mn =5800) was purchased from the Sigma-Aldrich Co.. The seeding

gel was prepared by mixing TPAOH, distilled water, TBOT and TEOS following the molar composition:

0.35TPAOH: 1TEOS: 0.025 TBOT: 20H2O. The typical preparation procedure was as followed: the

TBOT was added dropwise into TPAOH solution under stirring at 0 °C. After hydrolyzing at 0 °C for 60

min, the TEOS was added dropwise and stirred at room temperature for 10 h. Then, the final sol was

5

heated to hydrolyze and alcohols were removed repeatedly at 60 °C. The composition of the final sol

was maintained in the range of 1.0 SiO2: 0.025 TiO2: 0.35 TPAOH: 20 H2O. Then it was transferred into

a Teflon-lined stainless-steel autoclave and treated at 80 °C for 24 h to obtain the seeding gel.

The fabrication of hierarchical TS-1 zeolite was generally divided into two processes: the preparation

of the amorphous carbon-titanosilicate composite and the followed crystallization process by the DGC

method. In the first step, a clear solution was prepared with the molar compositions 1 CA : 1 TEOS :

0.025 TBOT : 20 C2H5OH : 20 H2O : 0.017 P123. The typical preparation procedure was as followed:

10 g P123 and 21 g CA were dissolved in 36 g H2O, and then TEOS and TBOT ethanol solution (20.8 g

TEOS and 0.85 g TBOT were dissolved in 92 g C2H5OH) were successively added to the former P123

solution under vigorous stirring for 2 h to obtain the clear solution. The PU foams were impregnated

with this clear solution and the air bubbles inside the PU foam were removed by frequently squeezing

the foam with a glass rod during the infusion of the sol solution till the foams could not absorb any

solution. And then the infused PU foam was taken out to evaporate the solvent at room temperature in

the drafty closet. This process was repeated for three times to ensure that the foam was filled with the

silica precursors. After drying at room temperature for 48 h, the soaked PU foams were calcined with

protection of N2 at 700 oC for 4 h. And then, the carbon-titanosilicate composite was received and

denoted as TSC. In the second step, the dry TSC monolith was impregnated with the pre-prepared

seeding gel solution for 30 min and then was separated and dried at 60 oC for 10 h to obtain the zeolite

precursor. The zeolite precursor (2.0 g) were put in a polytetrafluoroethylene (PTFE) lined stainless steel

autoclave, containing 5 mL pre-added water at the bottom to produce saturated steam (caution: no solid

contacted directly with water). After heating at 175 oC for different times, the auto clave was cooled to

room temperature and the solid was separated, washed thoroughly with distilled water, dried at 80 oC

6

and finally calcined in air at 550 oC for 5 h to ensure the complete removal of the template. The obtained

sample was denoted TS-xh, where x represents the crystallization time. For comparison with the seeding

gel, the TPAOH was used as director of zeolites. The dry TSC monolith was impregnated with the

TPAOH solution (35%) and then was evaporated at 60 oC to obtain the zeolite precursor. The molar

ratio of TPAOH/SiO2 was fixed to 0.22 in this zeolite precursor, which was kept as same as in the

zeolite precursor obtained with the seeding gel as director. The similar crystallization process was

performed as using the seeding gel as director. The obtained samples were denoted TS-xh-TPAOH,

where x represents the crystallization time. For comparison, conventional TS-1 catalyst was prepared by

the Enichem method [46]. This conventional TS-1 zeolite was prepared with a composition of

0.5TPAOH: SiO2: 0.025TiO2: 0.2H2O2: 35H2O and was autoclaved at 170 oC for 3d.

2.2 Characterization Methods

The X-ray diffraction (XRD) patterns were collected on a Rigaku-Ultima IV diffractometer using Cu

Kα radiation and a nickel filter in the 2θ angle range of 5-35° at 35 kV and 25 mA. The relative

crystallinity was estimated by comparing the five peaks areas (22-28°) of these samples with those peaks

areas of a commercial ZSM-5 sample, purchased from the Catalyst Plant of Nankai University.

Morphological analysis was performed by an S-4800 field emission scanning electron microscope

(FE-SEM, Hitachi, Japan) with an acceleration voltage of 3 kV. Transmission electron microscopy

(TEM) experiments were conducted on TECNAI G2 F30 operating at 300 kV. For the TEM image, the

specimens were dispersed in ethanol and placed on holey copper grids. Infrared tests were performed on

a Fourier Transform Infrared (FTIR) spectrometer (NEXUS 670) using the conventional KBr wafer

technique. UV-visible measurements were performed on a Shimadzu UV-2400PC using the diffuse

reflectance mode with BaSO4 as a reference. Nitrogen adsorption-desorption isotherms was measured at

7

-196 oC on a Quantachrome Autosorb-3B volumetric adsorption analyzer. Before the measurements, the

sample was out-gassed for 4 h at 300 oC. The BET specific surface area was calculated using adsorption

data acquired at a relative pressure (p/p0) range of 0.05-0.22. The total pore volumes were determined

from the amount adsorbed at a relative pressure of 0.99. The micropore and external surface areas as

well as the micropore volume were calculated by the t-plot method. The pore size distribution (PSD)

curves were calculated from the analysis of adsorption and desorption branch of the isotherm using the

Barett-Joyner-Halenda (BJH) algorithm respectively. Thermo gravimetric (TG) and derivative thermo

gravimetric (DTG) analyses were performed using a Perkin-Elmer TGA analyzer with a heating rate of

10 oC · min

-1 from 25 to 800

oC under an air flow. The content of Si and Ti element was determined by

inductively coupled plasma emission spectrometry (ICP) on a Thermo IRIS Intrepid II XSP atomic

emission spectrometer.

2.3 Catalytic Reactions

The epoxidation of 1-hexene and cyclohexene were carried out in a 50 ml three-necked flask fitted

with a condenser. 0.05 g of catalyst, 10 ml of methanol, 10 mmol of 1-hexene or cyclohexene and 10

mmol hydrogen peroxide (30 wt % H2O2 aqueous solution) were successively charged into the reactor.

The reaction was carried out under vigorous stirring and the temperature was controlled at 60 °C with an

oil bath for 2 h. After the reaction, the reactants were cooled quickly, and 0.5 g cyclohexanone (internal

standard) was added to the flask and stirred for 1 min. After removal of the catalyst powder, the reaction

mixture was analyzed using a gas chromatograph (capillary column, FID detector) and with

cyclohexanone as the internal standard. The amount of the unconverted H2O2 was determined with a 0.1

M aqueous solution of Ce(SO4)2 by using a titration method.

3. Results and Discussion

8

Powder XRD was used to monitor the phase structure changes taking place in the DGC process. Fig.

1A gives the XRD patterns of these samples with different crystallization times and the crystallization

curves of this series samples are illustrated in Fig. 2 correspondingly. As seen from Fig. 1A, the wide

dispersive peak of amorphous aluminosilicate at 15-30° disappeared and the diffraction peaks of TS-1

zeolite (MFI type diffraction peaks at 8.06°、8.94°, 23.2°, 23.7°, 24.0°and 24.5°) appeared after 2 h

crystallization. As seen from the crystallization curves (Fig. 2), the crystallization process proceeds more

rapidly. The relative crystallinity of these samples achieved 82% and 96% after 2 h and 24 h

crystallization respectively. The relative crystallinity increased slowly with crystallization process

further prolonging and the relative crystallinity reached 100% after 72 h crystallization. For comparison,

the TPAOH was used as director instead of the seeding gel. As shown of Fig. 1B, the TS-12h-TPAOH

sample only displays 38% relative crystallinity after 12 h crystallization. Even after 24 h heating, the

relative crystallinity of the obtained TS-24h-TPAOH sample just achieves 70%. So, the addition of the

seeding gel promotes the growth of zeolite significantly (Fig. 2). The reason is that the crystallization of

MFI type zeolites can occur on the surface of seeds with a rapid crystallization rate, which promotes the

growth of the zeolite [47].

As shown in the SEM image (Fig. 3A), the TS-0h sample is composed of amorphous particles. After

24 h crystallization, the TS-24h (Fig. 3B) sample is composed of zeolite nanocrystals which overlap

together. The zeolite crystals are around 100-200 nm in this sample. The reason is that the crystallization

of zeolite was carried out on the surface of seed and the amorphous titanosilicate gel converted into

nanosized zeolite in situ.

The nitrogen sorption isotherms are shown in Fig. 4A and the pore size distributions (PSD)

calculated from the desorption branch of the isotherm are illustrated in the Fig. 4B. Table 1 lists the

9

textural properties of these samples. Before steam heating, a type IV isotherm is observed for shaped

precursor (TS-0h) with a widely hysteresis loop at higher relative pressure range of p/p0=0.40-0.95.

Correspondingly, the pore size of this sample distributes widely (Fig. 4B, sample e), which can be

ascribed to the different size fractions of carbon template obtained from P123 and Polyurethane foam.

After steam heating treatment, the mesoporous structures of the obtained samples (from TS-12h to

TS-120h) were still retained. These samples (TS-12h to TS-120h) display a slight uptake of nitrogen and

a small hysteresis loop at higher relative pressure range of p/p0=0.50-1.0, indicating the existence of

some mesopores. However, the pore volume declines from 0.76 (TS-0h) to 0.32 cm3 g

-1 (TS-12h), 0.30

cm3 g

-1 (TS-120h), and the PSD curves of these samples became narrow. The reason can be ascribed to

micropore creation and mesopore shrinkage in the crystallization process. Furthermore, this H4 type

horizontal hysteresis loop could be related to the presence of mesopores embedded in a matrix with pore

mouths of a much smaller size, which means that there are secondary pores in contact with the exterior

by the zeolite channels [48]. A series of secondary pore around 2 nm are shown in the PSD curves (Fig.

4B), and these pores are also observed from TEM images. As seen from Fig. 5D, these secondary pores

formed among the intergrowth crystal. Furthermore, these samples exhibit a pore size distribution in the

range of 4-10 nm radius (Fig. 4B). Especially, the PSDs calculated from the adsorption (Fig. S1) and

desorption branch both give the pore centered around 4 nm, which means that this pore exists truly not

come from the TSE phenomenon [49]. This pore is also confirmed by the transmission electron

microscopy measurements (Fig. 5C). The TEM images of the TS-24h sample confirmed the hierarchical

structure. This pore originated from the carbon, which came from the P123 enwrapped in the zeolite in

the crystallization process. In addition, the carbon originated from Polyurethane foam was also

embedded between the zeolite crystals. When the carbon was removed, the larger pores around 50 nm

10

formed correspondingly (Fig. 5B).

With steam heating treatment prolonging, the microporous volume of the obtained sample,

corresponding to the crystallinity of zeolites, increase from 0.13 (TS-12h) to 0.14 (TS-24h), 0.15

(TS-72h) and 0.15 cm3 g

-1 (TS-120h). These results are consistent with the crystallization curves of this

series samples. The BET specific surface areas and the total pore volumes of these samples are similar

(around 450 m2 g

-1 and 0.35 cm

3 g

-1). Moreover, the mesopore and macropore of these samples (TS-24h,

TS-72h and TS-120h) kept (Fig. 3C), which means that dual carbon templates method can direct

hierarchical structure effectively.

Fig. 6 shows the FTIR spectra of the TS-xh series of samples prepared with different crystallization

times. All samples show adsorption bands at 1080 cm-1

(internal asymmetric stretch), 960 cm-1

, 805 cm-1

(external symmetric stretch), 550 cm-1

and 455 cm-1

(T-O bend). The band at 550 cm-1

is characteristic

FTIR adsorption bands of MFI zeolites with double five-membered rings [50-52]. The intensity ratio of

the 550 and 450 cm-1

bands have been used to assess the formation of MFI zeolite and have been termed

the FTIR crystallinity [50,51]. Despite no TS-1 zeolite peaks appearance in TS-0h XRD diffraction

patterns, the TS-0h sample gives the 550 cm-1

band in FTIR spectra. The reason can be ascribed to the

zeolite seeding gel addition in the precursor. There are double five-member rings among the zeolite

seeding gel, so the TS-0h sample also exhibits the 550 cm-1

band in FTIR spectra. However, the

intensity ratio of the 550 and 450 cm-1

bands of TS-0h sample is the smallest among these five samples,

which is consistent with the lowest crystallinity of the TS-0h sample. The 550 cm-1

band became sharp

as the steam heating time was prolonged to 12 h and 24 h. The intensity ratio of the 550 and 450 cm-1

band of these samples are shown in the Fig. 5. For the samples of TS-0h, TS-2h, TS-6h, TS-12h, TS-24h

and TS-72h, the intensity ratio is 0.12, 0.49, 0.52, 0.54, 0.59 and 0.58 respectively. Based of these

11

results, it is clear that the IR crystallinity of MS-y samples increases with prolonged steaming time,

which is in good agreement with the variation of its micropore volume. At the same time, the band of

960 cm-1

is strengthened after 6 h and become a shoulder after 12 h. Since 960 cm-1

band is the

characteristic of Si-O-Ti bond or Si-O bond perturbed by the presence of Ti atom in the framework of

TS-1. So, the strengthening of 960 cm-1

band means that tetrahedral Ti enters the crystal structure of the

zeolite. The UV-vis diffuse reflectance spectra of these samples also prove this procedure. As shown in

Fig. 7, all of the spectra show a strong absorption band at 210 nm indicating the presence of tetrahedral

Ti coordination species in the framework [53,54]. On the other hand, a shoulder at 275 nm appears in

these samples (Fig. 7, b-e) after steam heating treatment, indicating the presence of higher coordinated

Ti species (in penta- or octahedral coordination) and co-existence of a small extent of tetrahedral Ti sites

[55]. No adsorption band appeared around 330 nm, indicating that no obvious TiO2 phase formed [56].

From the above results, we could conclude that this dry gel conversion method could maintain the

stability of tetrahedral Ti in the obtained zeolites.

Fig. 8 presents TG-DTG curves of titanosilicate carbon composite (TSC) and as-synthesized samples

with different crystallization time, and the TG results of these as-prepared samples are displayed in

Table 2. TG curves can be divided into three zones based on the DTG curves of these samples. The

weight loss in zone I (25-110 oC) corresponded to the removal of physisorbed water. Zone II (110-500

°C) is associated with the thermal decomposition of the structure-directing agent (TPAOH) in the

surface and the micropore of the obtained zeolite. Zone III (500-800 °C) involves the remove of carbon

template by combustion. The weight loss in zone II of TSC sample is 0.9 %, which is much less than

other samples. The reason is that there is no zeolite seeding gel in the TSC sample and this weight loss

may be ascribed to the dehydration of Si-OH. After impregnation of the zeolite seeding gel, TS-0h

12

sample show 29% weight loss in the zone II. The weight ratio of TPAOH to titanosilicate gel (the weight

of sample after calcination at 800 oC) is 0.55. After heating at 175

oC for 6h, the obtained TS-6h sample

exhibits 16.6% weight loss in the zone II. Correspondingly, the weight ratio of TPAOH to titanosilicate

gel decreased to 0.23. With the heating time prolonging, this weight ratio of TPAOH to titanosilicate gel

remains at 0.22. Furthermore, in the TG curves of the TS-0h sample, the weight loss of the zone II

occurred mainly below 300 oC. The other four samples exhibit weight loss (Zone II) mainly in 300-500

°C. The former weight loss (100-300 °C) is associated with the thermal decomposition of the

structure-directing agent (TPAOH) on the surface of amorphous titanosilicate gels. The later weight loss

(300-500 °C) involves the decomposition of TPA+ ions within the micropore of the formed zeolite. So,

the TPAOH was occluded gradually into the micropores of the formed zeolite in the crystallization

process. When the amorphous titanosilicate gels were completely transformed into zeolite crystals, most

TPAOH entered the micropores of the zeolite in this crystallization process. In the TSC sample, the

weight ratio of carbon to titanosilicate gel is 0.25. When the zeolite seeding gel was introduced, this

weight ratio of carbon to titanosilicate gel decreased from 0.25 (TSC) to 0.14 (TS-0h), and this ratio kept

constant within heating process, which means the carbon did not loss in the crystallization procedure.

To survey the catalytic capacity of the resulted hierarchical zeolites, epoxidation of alkenes

(1-hexene and cyclohexene) by using H2O2 as oxidant were used as probe reaction. The conventional

TS-1 zeolite with the same Si/Ti ratio (around 42) as these hierarchical zeolites was synthesized by

hydrothermal method. This conventional TS-1 sample owns high crystallinity (Fig. S1) and is composed

with 200 nm zeolite crystal (Fig. S2). The nitrogen sorption isotherms of this conventional TS-1 is a type

I isotherm, which is the typical isotherm of microporous materials (Fig. 4A). Table 1 lists the textural

properties of these samples. In agreement with the results reported in the literature [56], the conventional

13

TS-1 sample exhibits 20.6% conversion with 94% selectivity of epoxyhexane (table 3). These

hierarchical TS-1 zeolites showed almost the same selectivity of epoxyhexane in the epoxidation of

1-hexene (around 92%). However, the conversion of 1-hexene increased from 11.2% (TS-12h) to 15.8%

(TS-24h). With the crystallinity further increasing, the TS-72h and TS-120h samples exhibited the

higher conversion of 1-hexene (around 20%) than the TS-24h sample. Compared to the TS-1 zeolite

prepared by conventional hydrothermal synthesis, the TS-72h and TS-120h samples with high

crystallinity displayed the same conversion of 1-hexene and did not significantly improve. The reason is

that the 1-hexene can diffuses into the channel of MFI-type materials with small molecular size. So, the

1-hexene conversion was mainly depended on the Ti content of the TS-1 zeolite, and this hierarchical

structure has limited impact on the activity. Correspondingly, the efficiency of H2O2 is similar for these

samples.

Cyclohexene has larger molecular size than 1-hexene, which hardly diffuses into the channel of

MFI-type materials. So, the epoxidation of cyclohexene occurred mainly on the external surface and

near the pore mouth of the zeolite. Therefore, compared with 1-hexene, the conversion of cyclohexene

was much lower with TS-1 as catalyst. As shown of table 3, the conversional TS-1 zeolite exhibits 2.1%

conversion, which was in agree with the results reported in the literature [56]. The selectivity of

epoxycyclohexane, dicyclohexanol and methoxy cyclohexanol was 18%, 35% and 41% respectively.

However, these hierarchical zeolites exhibit higher conversion of cyclohexene. The conversion of

cyclohexene of TS-12h sample reached 2.8% with 28% epoxide selectivity, which was higher than the

conventional TS-1. The TS-72h sample exhibited 4.2% conversion of cyclohexene, which was almost

two times of the conventional TS-1 zeolite. The selectivity of the products also changed regularly. The

selectivity of epoxycyclohexane of these hierarchical zeolites increased from 28% (TS-12h) to 37%

14

(TS-120h), and the selectivity of dicyclohexanol decreased from 26% (TS-12h) to 23% (TS-120h).

However, the electivity of methoxy cyclohexanol was mainly around 34% for these hierarchical zeolites.

Compared with the conversional TS-1 zeolite, the enhancement of cyclohexene conversion may be

attributed to larger external surface area and mesopore structure of these hierarchical TS-1 zeolites,

which offered more active site in contact with the cyclohexene. And this hierarchical structure also

increased the diffusion rate of the epoxycyclohexane and prevented their further conversion. So, the

enhancement of epoxycyclohexane selectivity of these hierarchical zeolites was higher than the

conversional TS-1 zeolite.

4. Conclusions

The hierarchical TS-1 zeolites, composed of nanocrystalline zeolites, with mesoporous and

macroporous structure had been successfully synthesized by dual carbon template method. The

formation of nanocrystalline zeolite was contributed by the addition of seed gel and involved surface

crystallization on the seed. The carbon obtained from carbonation of P123 and PU directed

mesostructure and macroporous architectures respectively. The obtained hierarchical TS-1 zeolites

exhibited well catalytic capacities to epoxidation of cyclohexene.

Acknowledgements

This work is supported by National Science Foundation of China (21003083) and Doctoral

Foundation of Shandong Province (BS2009CL031). M. B. Yue is thankful for the Qufu Normal

University Foundation (XJ200808 and bsqd08041).

Reference:

[1] M. Taramasso, G. Perego and B. Notari, US Patent 4410501, 1983.

[2] A. Corma, M.A. Camblor, P. Esteve, A. Martinez, J. Perez-Pariente, J.Catal. 145 (1994) 151-158.

15

[3] P. Wu, T. Tatsumi, T.T. Komatsu, T. Yashima, J. Catal. 202 (2001) 245-255.

[4] D. R. C. Huybrechts, L. DeBruycker, P. A. Jacobs, Nature 345 (1990) 240-242.

[5] T. Tatsumi, M. Nakamura, S. Negishi, H.Tominaga, Chem. Commun. (1990), 476-477.

[6] S. Bordiga, A. Damin, F. Bonino, G. Ricchiardi, A. Zecchina, R. Tagliapietra, C. Lamberti, Phys.

Chem. Chem. Phys. 5 (2003) 4390-4393.

[7] C. Lamberti, S. Bordiga, A. Zecchina, G. Artioli, G. Marra, G. Spanò, J. Am. Chem. Soc. 123 (2001)

2204-2212.

[8] A. Corma, Chem. Rev. 97 (1997) 2373-2419.

[9] J. X. Jiang, J. H. Yu, A. Corma, Angew. Chem. Int. Ed. 49 (2010) 3120-3145.

[10] M. S. Holma, E. Taarninga, K. Egeblada, C. H. Christensen, Catal. Today 168 (2011) 3-16.

[11] C. W. Jones, K.Tsuji, M. E. Davis, Nature 393 (1998) 52-54.

[12] K. Na, M. Choi, R. Ryoo, Microporous Mesoporous Mater. 166 (2013) 3-19.

[13] Z. L. Hua, J. Zhou, J. L. Shi, Chem. Commun. 47 (2011) 10536-10547.

[14] J.C. Groen, J.C. Jansen, J.A. Moulijn, J. J. Pérez-Ramírez, J. Phys. Chem. B 108 (2004)

13062-13065.

[15] J. C. Groen, J. A. Moulijn, J. J. Pérez-Ramírez, J. Mater. Chem., 2006, 16, 2121-2131.

[16] J. C. Groen, L. A. A. Peffer, J. A. Moulijn, J. Pérez-Ramírez, Chem. Eur. J. 2005, 11, 4983-4994.

[17] A. Boisen, I. Schmidt, A. Carlsson, S. Dahl, M. Brorsona, C. J. H. Jacobsen, Chem. Commun.

(2003) 958-959

[18] C. J. H. Jacobsen, C. Madsen, J. Houzvicka, I. Schmidt, A. Carlsson, J. Am. Chem. Soc. 122 (2000)

7116-7117.

[19] Z. Yang, Y. Xia, R. Mokaya, AdV. Mater. 16 (2004) 727-732.

16

[20] A. Sakthivel, S. J. Huang, W. H. Chen, Z. H. Lan, K. H. Chen, T. W. Kim, R. Ryoo, A. S. T.

Chiang, S.B. Liu, Chem. Mater. 16 (2004) 3168-3175.

[21] Y.Tao, H. Kanoh, K. Kaneko, J. Am. Chem. Soc. 125 (2003) 6044-6045.

[22] Y. Tao, H. Kanoh, K. Kaneko, J. Phys. Chem. B 107 (2003) 10974-10976.

[23] Y. Tao, Y. Hattori, A. Matumoto, H. Kanoh, K. Kaneko, J. Phys. Chem. B 109 (2005) 194-199.

[24] S. Kim, J. Shah, T. J. Pinnavaia, Chem. Mater. 15 (2003) 1664-1668.

[25] W. C. Li, A. H. Lu, R. Palkovits, W. Schmid, B. Spliethoff, F. Schüth, J. Am. Chem. Soc. 127

(2005) 12595-12600.

[26] H. Mori, K. Aotani, N. Sano, H. Tamon, J. Mater. Chem. 21 (2011) 5677-5681.

[27] F. Xiao, L. Wang, C. Yin, K. Lin, Y. Di, J. Li, R. Xu, D. S. Su, R. Schlgl, T. Yokoi, T. Tatsumi,

Angew. Chem. Int. Ed. 45 (2006) 3090-3093.

[28] M. Choi, H. S. Cho, R. Srivastava, C. Venkatesan, D. H. Choi, R. Ryoo, Nature Mater.5 (2006)

718-723.

[29] H. Wang, T. J. Pinnavaia, Angew. Chem. Int. Ed. 45 (2006) 7603-7606.

[30] G. T. Pederson, S. T. Gray, C. A. Woodhouse, J. L. Betancourt, D. B. Fagre, J. S. Littell, E.

Watson, B. H. Luckman, L. J. Graumlich, Science 333 (2011) 328-332.

[31] Y. Zhu, Z. Hua, J. Zhou, L. Wang, J. Zhao, Y. Gong, W. Wu, M. Ruan, J. Shi, Chem. Eur. J. 17

(2011) 14618-14627.

[32] H. Xin, J. Zhao, S. Xu, J. Li, W. Zhang, X. Guo, E.J.M. Hensen, Q. Yang, C. Li, J. Phys. Chem. C

114 (2010) 6553-6559.

[33] Y. Fang, H. Hu, Catal. Commun. 8 (2007) 817-820.

[34] Y. Cheneviere, F. Chieux, V. Caps, A. Tuel, J. Catal. 269 (2010) 161-168.

17

[35] L. H. Chen, X.Y. Li, G. Tian, Y. Li, J. C. Rooke, G.S. Zhu, S.L. Qiu, X.Y. Yang, B.L. Su, Angew.

Chem. Int. Ed. 50 (2011) 11156-11161.

[36] X. Wang, G. Li, W. Wang, C. Jin, Y. Chen, Microporous Mesoporous Mater. 142 (2011) 494-502.

[37] I. Schmidt, A. Krogh, K. Wienberg, A. Carlsson, M. Brorson, C.J.H. Jacobsen, Chem. Commun.

(2000) 2157-2158.

[38] C. Xue, J. Wang, B. Tu, D. Zhao, Chem. Mater. 22 (2010) 494-503

[39] L. Huerta, J. E. Haskouri, D.Vie, M. Comes, J. Latorre, C. Guillem, M. Dolores Marcos, R.

Martínez-Maníz, A. Beltrán, D. Beltrán, P. Amorás, Chem. Mater. 19 (2007) 1082-1088,

[40] Y. Lee, J. S. Lee, Y. S. Park, K. B. Yoon, Adv. Mater. 13 (2001) 1259-1263.

[41] X. Li, X. Wang, H. Chen, P. Jiang, X. Dong, J. Shi, Chem. Mater. 19 (2007) 4322-4326.

[42] J. S. Lee, Y. J. Lee, E. L. Tae, Y. S. Park, K. B. Yoon, Science 301 (2003) 818–821.

[43] Y. J. Lee, K. B. Yoon, Microporous Mesoporous Mater. 88 (2006) 176–186.

[44] C. Xue, B. Tu,; D. Zhao, Adv. Funct. Mater. 18 (2008) 3914– 3921.

[45] C. F. Xue, B.Tu, D. Zhao, Nano Res. 2 (2009), 242–253.

[46] M.G. Clerici, G. Bellussi, U. Romano, J. Catal. 129 (1991), 159-167.

[47] N. Ren, Z. J. Yang, X. C. Liu, J. Shi, Y. H. Zhang, Y. Tang, Microporous Mesoporous Mat. 131

(2010) 103-114.

[48] M. Kruk, M. Jaroniec, Chem. Mater. 13 (2001) 3169-3183.

[49] J. C. Groena, L. A.A Peffera, J. Pérez-Ramı́rez, Microporous Mesoporous Mat. 60 (2003) 1–17

[50] P. A. Jacobs, H. K. Beyer, J. Valyon, Zeolites 1 (1981) 161-168.

[51] J. C. Jansen, F. J. van der Gaag, H. van Bekkum, Zeolites, 4 (1984) 369-372.

[52] G. Coudurier, C. Naccache, J. C. Vedrine, J. Chem. Soc., Chem. Commun. (1982) 1413-1415..

18

[53] X. Wang, X. Guo, Catal. Today 51 (1999) 177-186.

[54] H. Liu, G. Lu, Y. Guo, Y. Guo, Appl. Catal. A 293 (2005) 153-161.

[55] K. Johannsen, A. Boisen, M. Brorson, I. Schmidt, C.J.H. Jacobsen, in: R. Aiello, G. Giordano, F.

Testa (Eds.), Impact of Zeolites and other Porous Materials on the New Technologies at the

Beginning of the New Millennium, Studies in Surface Science and Catalysis, vol. 142, Elsevier,

Amsterdam, 2002, p. 109.

[56] H. Liu, G. Lu, Y. Guo, Y. Guo, Appl. Catal. A 293 (2005) 153-161.

[57] W. Fan, P. Wu, T. Tatsumi, J. Catal. 256 (2008) 62–73.

19

Captions of Figures and Tables

Table 1 Textural property of TSC sample and TS-xh series samples

Table 2 TG results of TSC and as-prepared zeolites

Table 3 Epoxidation of 1-hexene and cyclohexene with H2O2

Fig. 1 XRD patterns of the TS-xh (A) series and the TS-xh-TPAOH (B) series samples.

Fig. 2 The crystallinity variation of the TS-xh (a) series and the TS-xh-TPAOH (b) series samples.

Fig. 3 SEM images of samples (A) TS-0h, (B) TS-24h.

Fig. 4 Nitrogen adsorption desorption isotherms (A) and the Pore size distribution of TS-xh series

samples: calculated from the desorption branches (B). (a) TS-12h, (b) TS-24h, (c) TS-72h, (d) TS-120h,

(e) TS-0h, (f) TS-1 zeolite. The isotherms for samples b, c, d were offset vertically by 20, 40, 60 cm3 g

-1

respectively.

Fig. 5 TEM images of the TS-24h sample.

Fig. 6 IR spectra of the TS-xh series samples: (a) TS-0h, (b) TS-2h, (c) TS-6h, (d) TS-12h, (e) TS-24h,

(f) TS-72h, (g) TS-120h.

Fig. 7 UV-visible spectra of the TS-xh series samples: (a) TS-0h, (b) TS-12h, (c) TS-24h, (d) TS-72h, (e)

TS-120h.

Fig. 8 TG (A) and DTG (B) curves of as-prepared samples: (a) TSC, (b) TS-0h, (c) TS-6h, (d) TS-12h,

(e) TS-24h, (f) TS-120h.

20

Table 1 Textural property of TSC sample and TS-xh series samples

Pore volume (cm3 ·g

-1) Samples Surface area

(m2·g

-1) Total Micropores Mesopores

External Surface

(m2·g

-1)

TSC

TS-12h

TS-24h

TS-72h

TS-120h

TS-1

529

450

502

495

441

387

0.76

0.32

0.36

0.41

0.30

0.19

0.00

0.13

0.14

0.15

0.15

0.14

0.76

0.19

0.22

0.26

0.15

0.05

529

193

211

178

158

56

21

Table 2 TG results of TSC and as-prepared zeolites

sample Zone I Zone II Zone III TPAOH/TSa Carbon/TS

b

TSC

TS-0h

TS-6h

TS-12h

TS-24h

TS-120h

6.3

11.3

1.3

1.3

2.8

2.8

0.9

29.0

16.6

16.4

15.2

15.5

18.6

7.3

10.3

10.0

10.5

10.1

-

0.55

0.23

0.22

0.21

0.21

0.25

0.14

0.14

0.14

0.15

0.14

a Weight ratio of weight loss in zone II (TPAOH) to the weight of sample after calcination at 800

oC

b Weight ratio of zone III (carbon) to the weight of sample after calcination at 800

oC.

22

Table 3 Epoxidation of 1-hexene and cyclohexene with H2O2

1-hexene Cyclohexene

Conv. Selec.a H2O2 (%) Conv. Selec. (%)

c H2O2 (%)

sample Si/Ti

ratio

(%) (%) Conv. Effi. b (%) Epoxide

d Diol

e Ether

f Conv. Effi.

b

TS-12h

TS-24h

TS-72h

TS-120h

TS-1

42.2

43.1

41.8

42.5

42.4

11.2

15.8

20.4

21.3

20.6

91

93

94

93

94

12.7

17.2

22.7

23.4

22.9

88

92

90

91

90

2.8

3.7

4.2

4.3

2.1

28

31

35

37

18

26

28

25

23

35

37

34

33

34

41

3.5

4.7

5.1

5.2

2.7

80

78

83

82

79

a, Epoxide selectivity; b, Efficiency; c, three main products was listed; d, epoxycyclohexane; e, dicyclohexanol; f,

methoxy cyclohexanol.

23

Captions of Figures

Fig. 1 XRD patterns of the TS-xh (A) series and the TS-xh-TPAOH (B) series samples.

Fig. 2 The crystallinity variation of the TS-xh (a) series and the TS-xh-TPAOH (b) series samples.

Fig. 3 SEM images of samples (A) TS-0h, (B) TS-24h.

Fig. 4 Nitrogen adsorption desorption isotherms (A) and the Pore size distribution of TS-xh series

samples: calculated from the desorption branches (B). (a) TS-12h, (b) TS-24h, (c) TS-72h, (d) TS-120h,

(e) TS-0h, (f) TS-1 zeolite. The isotherms for samples b, c, d were offset vertically by 20, 40, 60 cm3 g

-1

respectively.

Fig. 5 TEM images of the TS-24h sample.

Fig. 6 IR spectra of the TS-xh series samples: (a) TS-0h, (b) TS-2h, (c) TS-6h, (d) TS-12h, (e) TS-24h,

(f) TS-72h, (g) TS-120h.

Fig. 7 UV-visible spectra of the TS-xh series samples: (a) TS-0h, (b) TS-12h, (c) TS-24h, (d) TS-72h, (e)

TS-120h.

Fig. 8 TG (A) and DTG (B) curves of as-prepared samples: (a) TSC, (b) TS-0h, (c) TS-6h, (d) TS-12h,

(e) TS-24h, (f) TS-120h.

24

Graphic Abstract

0.0 0.2 0.4 0.6 0.8 1.0

200

250

1 10 100 10000.0

0.2

0.4

Vo

lum

e (

cm3 g

-1 S

TP

)

Pore diameter (nm)

Vo

lum

e (

cm

3 g

-1 S

TP

)

P/P0

25

Highlights

Hierarchically TS-1 zeolites have been prepared via a rapid dry-gel conversion method.

The carbon obtained from carbonation of P123 and PU is used to direct mesostructure and macroporous architectures.

The hierarchical zeolite show good catalytic capacities to epoxidation of 1-hexene and cyclohexene.