Synthesis and characterization of mesoporous zeolite Y by using block copolymers as templates

Accepted Manuscript Synthesis and characterization of mesoporous zeolite Y by using block copolymers as templates Jun Zhao, Yanchao Yin, Yang Li, Wenyong Chen, Baijun Liu PII: DOI: Reference:

S1385-8947(15)01239-5 http://dx.doi.org/10.1016/j.cej.2015.08.143 CEJ 14139

To appear in:

Chemical Engineering Journal

Received Date: Revised Date: Accepted Date:

4 June 2015 7 August 2015 18 August 2015

Please cite this article as: J. Zhao, Y. Yin, Y. Li, W. Chen, B. Liu, Synthesis and characterization of mesoporous zeolite Y by using block copolymers as templates, Chemical Engineering Journal (2015), doi: http://dx.doi.org/ 10.1016/j.cej.2015.08.143

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Synthesis and characterization of mesoporous zeolite Y by using block copolymers as templates Jun Zhaoa, Yanchao Yina, Yang Lib, Wenyong Chenb, Baijun Liu a∗∗ a State Key Laboratory of Heavy Oil Processing, The Key Laboratory of Catalysis of CNPC, College of Chemical Engineering, China University of Petroleum (Beijing), Beijing 102249, People’s Republic of China b Shandong Qilu Huaxin Hi-tech co., LTD, 1688 Dongmen Road, Zhoucun, Zibo Shandong Province 255300, People’s Republic of China ABSTRACT Mesoporous zeolite Y is directly synthesized using block copolymers (pluronic F127) as templates. The block copolymers guide the aluminosilicate gel to assemble into mesoporous zeolite under its excellent aggregation properties. The samples were characterized by X-ray diffraction (XRD), nitrogen adsorption and desorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM), IR spectra analyses (FT-IR), FTIR spectroscopy of adsorbed pyridine (Py-IR), and temperature-programmed ammonia desorption (NH3-TPD). The results indicated that Meso-USY prepared with templates had a dual mesopores and large mesopore volume of 0.20 cm3·g−1. The acid type over Meso-USY was also modified, and high Brønsted to Lewis ratio was obtained. Their catalytic performance was assessed in a Micro-activity test unite at 733K using light diesel as material raw, Although the Meso-USY showed lower crystallinity and less total acid sites compared to Conv-USY, Meso-CAT prepared from Meso-USY ∗

Corresponding author. Tel: +86 1089733751; Fax: +86 10 89733751. E-mail address: [email protected] 1

presented excellent catalytic performance. Then, it can be concluded that the structural and textural properties of the mesoporous zeolite Y have considerable influence on the catalytic performance. The abundant mesopores volume and appropriate acidity are necessary for the excellent catalytic activity. Keywords：Zeolite Y; pluronic F127; Mesopore; Catalytic cracking. 1. Introduction Zeolite Y is a solid acid catalyst with a FAU type framework topology. It features three-dimension pore channels with SOD cages and possesses highly stable crystalline framework with a large pore opening of 0.74nm×0.74nm [1]. The micropores structure provides large surfaces, strong acid sites, especially excellent shape selectivity for zeolite Y. Because of these properties, zeolite Y plays an important role in chemical industry. However, with the growing lack of resources, the heavy feedstocks are gradually replacing the lighter feedstocks and many large molecules are involved in the reaction. The limited dimensions of the micropores of zeolite Y strongly hinder the diffusion of large molecules and this drawback seriously accelerate the catalyst deactivation in the reaction. To overcome this problem, the reduction of the intracrystalline diffusion path length is a key point. The methodologies include introduction of mesoporoes and decrease the zeolite crystal size [2]. The synthesis of nanosized zeolites is still limited own to its inherent prombles [3]. The difficulty of separation hinders the application of nanosized zeolites. Alternatively, the introduction of mesoporous is a convenient and effective method. In the past decades, there have been a lot of works to improve the diffusion of micropores, such as the synthesis of ordered mesoporous 2

materials (e.g.SBA-15 and MCM-41) [4,5], composites materials [6,7], and hierarchical zeolites [8]. However, ordered mesoporous materials and composites materials usually have low hydrothermal stability and acidity [9]. Hierarchical zeolite has high hydrothermal stability, strong acidity and large mesopore structure, by combining advantages of zeolites crystals and the benefits of mesoporous materials simultaneity. These novel features make it attracted many researchers’ attention. So far, strategy using templates is one of the main methods to prepared hierarchical zeolite. Templates are usually divided into “soft” templates and “hard” templates. For example, “hard” templates include carbon nanotube [10], carbon nanofibers [11], mesoporous carbon [12], carbon aerogel [13], and so on. Surfactants [14], amphiphilic-organosilane [15] and copolymer [16,17] are commonly regarded as “soft” templates. However, due to the special system of zeolite Y synthesis, it is difficult for the “hard” templates to directly graft into the aluminosilicates gel. The combining force between the templates and silicate species is weak, and phase separation occurs easily while the zeolite crystals are forming. To overcome the separation, synthesis process is usually complex and expensive. Block copolymers are often employed as “soft” templates. They are highly commercialized products, got easily and now widely used for the directly synthesis of mesoporous materials. It is general accepted that copolymers have an excellent aggregation property. As the literatures reported, it can form hydrogel network just like “scaffold” in aqueous solution [17,18]. And hierarchical zeolite is synthesized directly through the confined space of network. Zhou et al. [17] employed conventional block copolymers (F127, P123 or Brij series) and directly synthesized mesoporous ZSM-5 zeolites using a steam-assisted crystallization process. Zhou et al [18] used copolymer F127 and cationic surfactant cetyltrimethyl ammonium bromide as co-templates 3

synthesized mesoporous ZSM-5 zeolite through hydrothermal treatment. With the help of block copolymers, the aggregation of crystals creates the larger mesopore channels in zeolites. According previous researches, the synthesis of hierarchically porous zeolite Y using block copolymers as templates has rarely been reported yet. Herein, we report a novel method to prepare hierarchically porous zeolite Y. In this investigation, hierarchical zeolite Y was prepared using pluronic F127 (PEO106-PPO70-PEO106) as templates, and a direct synthetic route of micro/mesoporous zeolite Y had been developed with the assistance of hydrothermal method. In the aqueous solution of the zeolite precursor, the pluronic F127 directed the zeolite precursor species to grow into zeolites with large mesoporosity. As a solid acid catalyst, the mesoporous zeolite Y exhibited excellent catalytic properties in fluid catalytic cracking, reached high gasoline yield and low coke yield. This result proved that the mesopores provided free diffusion pathways for molecules and accelerated the catalyst activation. Briefly, it is a novel and feasible approach for generating large pores in zeolite Y using conventional hydrothermal system, which is not only be used to prepare zeolites for catalysts but also wide applications in other fields. 2. Experimental section 2.1. Preparation of mesoporous zeolite Y Zeolite Y was prepared through hydrothermal method as reported in reference [19]. The precursor solution with zeolite Y was prepared by NaAlO2 (95wt%, Beijing GuoHua Chemical Material Co.), NaOH (96wt%, Beijing Chemical Reagents Company), water glass (28.0wt% SiO2, Lanzhou Petro Chemical Co., Petro China Company Ltd.), and deionized water. All the chemicals were directly used as received without any further purification. The entire aluminosilicate gel for 4

the preparation of Y zeolites had a molar ratio of 0.42Na2O:0.074Al2O3:SiO2:17.13H2O:0.0005 F127. After being stirred for another 1.5 h, the precursor gel was transferred to a stainless steel autoclave and hydrothermally treated at 375K for 24 h. The samples were dried and calcinated at 823K in air flow for 6 h to remove the templates. The final mesoporous zeolite Y was denoted Meso-NaY. For comparison, a reference zeolite Y was obtained using the same process as mesoporous zeolite Y but without the addition of F127. This product was named NaY. 2.2. Preparation of catalysts The previous zeolites (Meso-NaY and NaY) were used as materials and mixed with1.0 M (NH4)2SO4 solution with the ions exchanged. After hydrothermal treatment at 873k for 2h, the zeolites were continually exchanged twice and then dried in air. The resulting products were ultra-stabile zeolite Y and denoted Meso-USY and Conv-USY, respectively. The catalysts were obtained from kaolin (50%), alumina gel (15%), and ultra-stabile zeolite Y (35%), calcinated at 823K for 1 h, crushed, and sieved to 40–60 mesh. The aging of the catalysts (5g) were carried out in water vapor at 1073K for 4 h. The final aged catalysts were named as Meso-CAT and Conv-CAT, respectively. 2.3. Physical and chemical characterization X-ray diffraction (XRD) patterns of the prepared zeolites were recorded on a Bruker AXSD8 Advance X-ray diffractometer using nickel-filtered Cu Ka X-ray radiation at 40 kV and 30 mA. The 2θ range was scanned from 15° to 35° with a scanning rate of 2°/min. The crystallinity of the zeolites was estimated from the reflections of the (hkl)-values of (311), (333), (440), (533), (642), 5

(660), (555) and (664) according to SH/T 0340–1992. The summation of the areas under these peaks was used to quantify the relative crystallinity. The crystallinity of NaY was taken as 100%. Si/Al ratios of the framework of zeolites were obtained from the peak shift of the (555) reflection on a Bruker AXSD8 Advance X-ray diffractometer. The pure silicon (99.999wt%, 2θ=28.443o) was used as the internal standard. The scan range was from 28o to 32o with a rate of 0.05o/min, and the scan step width was 0.02o. The framework Si/Al ratios of all the Y zeolites involved in this work were obtained from the a0 by equation [20] Si/Al ratios =

25.858 − a0 a0 − 24.191

, a0 taken in Å.

The specific surface areas and pore volumes of the zeolites were measured using a Bilder KuboX1000 system at liquid nitrogen temperature. The total specific surface areas were calculated using the Brunauer−Emmett−Teller (BET) equation. The total pore volumes were calculated from the amounts of nitrogen adsorbed at P/P0 = 0.98. The micropore volumes were calculated by the t-plot method. Barrett–Joyner–Halenda (BJH) model were used to obtain pore size distribution from the desorption branches of the isotherms. Scanning electron microscopy (SEM) was used to describe the morphology of the samples on a SU8010 (Hitachi, Japan) apparatus. Transmission electron microscopy (TEM) was used to evaluate the existence of the mesostructure by a JEOL JEM-2100 electron microscope operating at 200 kV. The IR spectra analyses (FT-IR) of the zeolites were performed on a Gangdong FTIR-850 infrared spectrophotometer (Gangdong Sci. &Tech. Development Co., Ltd., China) with a -1

resolution of 1cm . The samples were mixed with KBr (spectroscopy grade). The pyridine IR 6

(Py-IR) was obtained on Magna-IR 560 ESP spectrophotometer. The wafers (diameter 12 mm) were purged in the IR cell at 623K for 2h, and then cooled down to room temperature for pyridine adsorption. Py-IR spectra were recorded in the range of 1700 to 1400 cm-1 at 473K and 623K. Temperature-programmed ammonia desorption (NH3-TPD) of the samples was studied on a TPD/TPR 5079 analyzer. The previously heated samples were exposed to ammonia for 15 min to ensure adsorption saturation. After removing weakly adsorbed ammonia by injecting pure nitrogen at 373K for 1 h, the NH3-TPD profile was recorded from 373 to 873K at a heating rate of 10K min-1. 2.4. Catalytic cracking performance tests Catalytic cracking tests of the catalysts were carried out in a micro-activity test (MAT) unit. Light diesel (Sinopec Corp., Research Institute of Petroleum Processing) was used as feedstock. The catalytic cracking tests were performed under standard conditions. The catalyst loading was 5.0 g, and the reaction temperature was 733 K; 1.56 g of light diesel was injected into the reactor through a syringe tube within 70 s, which was followed by purging nitrogen at 20 ml min-1 for 10min. The products were collected in a gas collector and liquid collector through a cooling bath. The component analyses of the products were performed on a Beifen gas chromatographer equipped with a flame ionization detector and using nitrogen as the carrier gas. The coke deposited on the catalysts after the reaction was quantified by an automatic carbon analyzer (HV-4B, Wuxi Analysis Instruments Inc., People’s Republic of China). 3. Results and discussion

7

3.1. Structural of mesoporous zeolites Reference as NaY, the XRD patterns of the Conv-USY and Meso-USY zeolites (Fig. 1) clearly show a series of characteristic diffraction peaks assigning to the FAU type zeolite. Compared to Conv-USY, the intensity of Meso-USY characteristic reflections is decreased. The relative crystallinity of Conv-USY, quantified from the summation of the eight peaks areas, is 91% (Table 1). The relative crystallinity of Meso-USY is 81%, and decrease 10% referring to Conv-USY. As shown in Fig. 2, the FT-IR spectra are collected in the region of 1800-4000 cm-1 to characterize the framework vibrations of zeolites. The band at 1640 cm-1 belongs to the scissor vibration arising from the proton vibration in the water molecule. The bands at 1050 and 706 cm-1 represent the asymmetric and symmetric stretching vibrations corresponding to the inner TO4 structure (T=Si, Al), respectively, whereas the bands at 1170 and 788 cm-1 represent the asymmetric and symmetric stretching vibrations corresponding to the external TO4 structure (T=Si, Al), respectively. The band at 576 cm-1 is attributed to the double ring external linkage peak associated with the FAU structure [21], which is present in the Meso-USY curve indicating the existence of FAU framework. The band at 460 cm-1 is assigned to the structure-insensitive T-O bending modes to the tetrahedral TO4 structure (T=Si, Al). All characteristic bands of Meso-USY weaken compared to Conv-USY, suggesting the decrease in the crystallinity, which are in agreement with the XRD results.

3.2. Porous structure and morphology of mesoporous zeolites Compared to NaY (Fig. 3a), the nitrogen adsorption-desorption isotherms of Meso-USY and Conv-USY exhibit type IV isotherms with H-IV hysteresis loops (Fig. 3b), indicating the existence of 8

textural mesopores. Notably, the isotherms of Meso-USY exhibit a steep increase at relative pressure P/P0 of 0.85-1.00, referring to Conv-USY. Accordingly, Table 1 illustrates that the Meso-USY sample exhibits a mesopore volume of 0.20 cm3·g−1, which is larger than the mesopore volume of Conv-USY (0.12 cm3·g−1). Compared to Conv-USY (0.28 cm3·g−1), micropore volume of Meso-USY (0.26 cm3·g−1) decreases only a little, which suggests that the formation of mesopores is accompanied by slightly detrimental effect on the micropore structure. So it can be concluded that the addition of templates creates a majority of mesopores. The pore size distribution of Conv-USY zeolite show a bimodal distribution, two peaks appear at ca.3.8 and 10nm. For the Meso-USY zeolite, three peaks appear at ca.3.8, 6.5 and 35nm (Fig. 3c). As the previous literatures reported the 3.8nm peak is an artifact [20,22]. Compared the pore size distribution between Conv-USY and Meso-USY zeolites, it is reasonable to state that the 10 and 6.5 nm peaks are attributed to the hydrothermal treatment to get ultra-stabile zeolites, and the 35nm peak is belonged to the large pore introduced by F127 addition. These conclusions are also in good agreement with previous reports, the 30-50nm peak is ascribed to the prior aggregation–assembly between polymers and zeolite crystals [18,23]. Compared to smaller pores, larger pores play a more important role for the diffusion of reactants and products [24]. Moreover, it can be seen in table 1 that NaY exhibits a surface area of 681 m2g-1, while the Conv-USY is 594 m2g-1 and 2 -1

Meso-USY is 540 m g . So, we can get the result that with the increase of meso pore volume, the surface area of corresponding ultra-stabile zeolites decrease. The crystallite size and morphology of the Conv-USY and Meso-USY are investigated by SEM. As shown in Fig. 4b and d, the average particle size of both samples is about 600-800nm. 9

Comparing the morphology, there are a little difference between the Conv-USY and Meso-USY. More amorphous silica–alumina can be seen in Fig. 4c than Fig. 4a own to the lower crystallinity of Meso-USY. The TEM images of Meso-USY prove the existence of larger and smaller mesoporous. As demonstrated in Fig. 5c, a certain amount of mesopores centered around 35 nm emerge in the crystal of Meso-USY, showing the effective large mesopore formation using F127 as templates. And, if no templates are added into the synthesis system, the obtained Conv-USY do not exhibit the large mesopores (Fig. 5a), As shown in Fig. 5b and d, the smaller mesopores can be seen over Conv-USY and Meso-USY. This is attributed to the defects created in hydrothermal treatment process to get ultra-stabile zeolite.

3.3. Acidic properties of mesoporous samples The acid amount of the catalysts and ultra-stabile zeolites are characterized by temperature programmed desorption using NH3 as the probe molecule. As illustrated in Fig. 6a, the desorption peaks of ammonia at 473K and 623K correspond to weak acid sites and strong acid sites in the samples respectively. The specific area is proportional to the amount of acid sites in the samples and can be calculated by the Gaussian curve-fitting [25]. Compared to Conv-USY, Meso-USY exhibits evidently less total acid sites (Table 2). It may be due to the low crystallinities of Meso-USY (Table 1), resulting in a lower proportion of framework Al species [18,20]. As demonstrated in Fig. 6b, the curves of both catalysts present one desorption peak of ammonia at 473K. The profiles show that the area of Meso-CAT slightly smaller than the Conv-CAT. This is suggesting that the total acid amounts of Meso-CAT less than Conv-CAT (Table 2). Moreover, the data in Table 2 10

reflect that the positions of the two NH3 desorption peaks on the mesoporous samples shift to the low-temperature region, referring as conventional samples. These results indicate that the strength of strong/weak acids decreases, attributed to the addition of the F127. Pyridine IR spectroscopy is used to distinguished the Brønsted and Lewis acid sites in the samples. As listed in Table 2, the amounts of acid sites are evaluated according to equations from the literature [19]. Py-IR results show that the mesoporous samples show a high Brønsted to Lewis ratio (B/L, Table 3). It may probably be ascribed to the addition of templates regulates the ratio of the two acid sites of the mesoporous samples. Although, the total acid amounts of both mesoporous samples (Meso-USY and Meso-CAT) are less than the reference conventional samples (Conv-USY and Conv-CAT). The acidic properties prove that meso-CAT still preserves great amount of acidic sites of the reference Conv-CAT. 3.4. Catalytic cracking property As listed in Table 4, from the catalytic performance over the Conv-CAT without the addition of F127, a micro-activity of 59.67%, yield of gasoline 28.69wt%, and coke of 1.05wt% are achieved. Compared to Conv-CAT, the catalyst Meso-CAT fabricated by Meso-USY using F127 as templates exhibit a better catalytic cracking property. And a micro-activity of 63.00%, yield of gasoline 31.22wt%, and coke of 0.87wt% are presented. This can be understood by considering that the added templates play an important role in the performance of catalytic cracking activity. As previous researches reported [20,24], the acidity and porous structure greatly influence the catalytic property of catalysts. The acidic properties show that Meso-CAT catalyst preserves the majority of acidic sites, which are necessary for catalytic activity. The porous structure of 11

ultra-stabile zeolites reveals that the larger and smaller mesopores coexist in the Meso-USY zeolite, which is used to prepare Meso-CAT catalyst. Mesopores facilitate the transport of the raw materials, promote the products into and out of the zeolites, and shorten the residence time for the products, especially larger ones. All these are beneficial to the less coke yield and higher gasoline yield. Therefore, it is reasonable to understand that the excellent performance of Meso-CAT in catalytic cracking process. The gaseous products mainly consisted of propane, propylene, butane, butylenes, and C5+. The yield of gaseous product did not vary over different catalysts. 3.5. The formation route of mesoporous zeolite Y As shown in Scheme 1, the zeolite Y with two types of mesopore channels (the larger of ca. 35nm and the smaller of ca. 6.5nm) is prepared in a multistep process. At first step, the desired precursor aluminosilicate gel containing zeolite seeds are got through hydrolysis and rearrangement of silicate and aluminate. Then, a solution of F127 is added into the precursor gel. In this case, a large amount of F127 is employed, which favored the formation of the larger mesopore channels. As we know, F127 is a kind of triblock copolymer, which has hydrophobic poly (propylene oxide, PPO) and hydrophilic poly (ethylene oxide, PEO). The hydrophilic ends of F127 could bind to the hydrophilic of zeolite seeds by hydrophilic affinity on the surface of the seeds, and the hydrophilic PEO shells keep a stabilization of the aggregate micelles [18]. As the crystallization conducted, the seeds further grow into zeolite aggregates in the presence of attached F127 micelles, just as the previous reports that the F127 acted as a type of “scaffold” [17] to guide the growth of zeolite crystals. After calcinated in air to remove the templates, the zeolites produce the larger mesoporous (ca.35nm). Under a hydrothermal treatment, some aluminum 12

atoms would be removed from the zeolites. As a result, the corresponding defects would be created in the framework of treated zeolites. The smaller mesopore channels (ca.6.5nm) can be produced with the removal of parts aluminum atoms of zeolite framework. Finally, the aggregation of crystals creates the larger mesopore channels and the hydrothermal treatment generates the smaller mesopore channels. The zeolites with the coexistence of two sets of mesopores were prepared through this route. 4. Conclusion A novel aggregation–assembly method has been developed for the synthesis of the mesoporous zeolite Y with mesopore channels using the triblock copolymers F127 as templates. Two types of mesoporosity are present in the zeolite: smaller mesopores of 6.5nm and larger mesopores of 35nm. Meso-USY sample exhibits large mesopore volume of 0.20 cm3·g−1 and reserves abundant microporosity (micropore volume is 0.26 cm3·g−1), suggesting that the extra-mesopores are created. The addition of F127 not only introduces mesoporous into the zeolites but also regulates the acidity of the mesoporous samples. NH3-TPD results show that the acid amounts of mesoporous are less than conventional samples and the strength of strong/ weak acids decreases, attributed to the addition of the F127. However, the large acidic sites are still preserved over Meso-CAT. The mesopores offer easier transport and are beneficial for the accessibility to active sites, which reduce the formation of cokes and increase the micro-activity and yield of gasoline. These properties encourage Meso-CAT catalyst show better catalytic performance compared with Conv-CAT. This novel aggregation–assembly method is expected to be an efficient strength to produce other mesoporous materials and facilitate the mesoporous 13

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Figure Captions Fig.1. XRD patterns of zeolites (a) NaY (b) Conv-USY (c) Meso-USY Fig.2. FTIR spectra of zeolites (a) NaY (b) Conv-USY (c) Meso-USY Fig.3. N2 adsorption−desorption isotherms and pore size distributions of zeolites (a) NaY (as a reference) (b) Conv-USY and Meso-USY Fig.4. SEM images of (a and b) Conv-USY; (c and d) Meso-USY Fig.5. TEM images of (a and b) Conv-USY; (c and d) Meso-USY Fig.6. NH3-TPD profiles of (a) Conv-USY and Meso-USY; (b) Conv-CAT and Meso-CAT Scheme 1 Proposed route for the formation of mesoporous zeolite Y

17

Table 1 Crystallinity and textural parameters of zeolites Sample

Surface area （m2g-1）

Total pore

Micro pore

Meso pore

volume（cm3 g-1） volume （cm3 g-1） volume （cm3 g-1）

Crystallinity

SiO2/Al2O3

（%）

NaY

681

0.37

0.32

0.05

100

4.47

Conv-USY

594

0.40

0.28

0.12

91

5.73

Meso-USY

540

0.46

0.26

0.20

81

5.74

18

Table 2 NH3-TPD data of the samples

Temperature (K)

Amount (mmol/g)

Sample Weak acid

Strong acid

Weak acid

Strong acid

Total acid

Conv-USY

520

688

0.735

0.520

1.255

Meso-USY

510

674

0.482

0.421

0.903

Conv-CAT

490

613

0.112

0.059

0.171

Meso-CAT

484

606

0.104

0.054

0.158

19

Table 3 Amounts and distribution of the acid sites of zeolites and catalysts

Amount (µmol/g) and distribution of acid site Samples

Total acid(473K)

Media and strong acid(623K)

Bronsted

Lewis

B/L

Bronsted

Lewis

B/L

Conv-USY

523

293

1.79

232

128

1.81

Meso-USY

401

147

2.72

174

60

2.95

Conv-CAT

62

35

1.77

18

10

1.80

Meso-CAT

60

29

2.07

15

7

2.14

20

Table 4 The Micro-Test performance of different catalysts

Catalysts

Product distribution

Yield of

(wt. %)

Gasoline

Micro-activity

Gas composition (wt. %)

Gas

Liquid

Coke

(wt. %)

CH4

C2H6

C2H4

C3H8

C3H6

C4H10

C4H8

C5+

Conv-CAT

59.67

29.93

69.02

1.05

28.69

0.33

0.27

0.87

2.94

20.98

6.40

5.70

62.52

Meso-CAT

63.00

30.91

68.22

0.87

31.22

0.39

0.33

1.03

3.20

21.05

7.46

5.75

60.80

21

Fig. 1. XRD patterns of zeolites (a) NaY (b) Conv-USY (c) Meso-USY

22

Fig. 2. FTIR spectra of zeolites (a) NaY (b) Conv-USY (c) Meso-USY

23

Fig. 3. N2 adsorption−desorption isotherms and pore size distributions of zeolites (a) NaY (as a reference) (b) Conv-USY and Meso-USY

24

a

b

c

d

Fig. 4. SEM images of (a and b) Conv-USY; (c and d) Meso-USY

25

a

c

Fig. 5. TEM images of (a and b) Conv-USY; (c and d) Meso-USY

26

b

d

Fig. 6. NH3-TPD profiles of (a) Conv-USY and Meso-USY; (b) Conv-CAT and Meso-CAT

27

Scheme 1 Proposed route for the formation of mesoporous zeolite Y

28

Highlights


Block copolymers F127 is employed as templates to prepare mesoporous zeolite Y.




Two types of mesoporosity are present in the zeolite: smaller and larger mesopores.




Acidic properties of zeolite were modified, owing to the templates addition.




Both micro-activity and yield of gasoline increased for mesoporous catalyst.