Hydrophobic aluminosilicate zeolites as highly efficient catalysts for the dehydration of alcohols

    Hydrophobic aluminosilicate zeolites as highly efficient catalysts for the dehydration of alcohols Shaodan Xu, Huadong Sheng, Tao Ye, Dan Hu, Shangfu Liao PII: DOI: Reference:

S1566-7367(16)30053-X doi: 10.1016/j.catcom.2016.02.006 CATCOM 4587

To appear in:

Catalysis Communications

Received date: Revised date: Accepted date:

24 November 2015 3 February 2016 5 February 2016

Please cite this article as: Shaodan Xu, Huadong Sheng, Tao Ye, Dan Hu, Shangfu Liao, Hydrophobic aluminosilicate zeolites as highly efficient catalysts for the dehydration of alcohols, Catalysis Communications (2016), doi: 10.1016/j.catcom.2016.02.006

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ACCEPTED MANUSCRIPT Hydrophobic Aluminosilicate Zeolites as Highly Efficient Catalysts

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for the Dehydration of Alcohols

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a

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Shaodan Xu a,b, Huadong Sheng a, Tao Ye a,c, Dan Hu a, Shangfu Liao a,*

Zhejiang Institute of Quality Inspection Science, Hangzhou 310018, China Tel: +86-0571-85129819;

Key Laboratory of Applied Chemistry of Zhejiang Province, Department of

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b

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E-mail: [email protected]

Chemistry, Zhejiang University, Hangzhou 310027, China

MOE Key Laboratory of Macromolecular Synthesis and Functionalization,

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c

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310027, China.

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Department of Polymer Science and Engineering, Zhejiang University, Hangzhou

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ACCEPTED MANUSCRIPT Abstract: Efficient dehydration of alcohols to olefins, acting as a control step in the upgrading of phenolic biofuel into alkane fuels, is an important topic in biomass

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conversion. Here, we report the design and synthesis of hydrophobic aluminosilicate

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ZSM-5 zeolites by an organosilane-modification approach (ZSM-5-OS). Water-droplet contact angle tests confirm the formation of hydrophobic surface after the modification. Interestingly, the obtained ZSM-5-OS catalysts exhibit excellent

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catalytic properties in dehydration of various alcohols into the corresponding olefins

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in water solvent. The approach reported in this work would be potentially important

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for developing more efficient catalysts for biomass conversion in the future.

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Keywords: ZSM-5 zeolite, dehydration of alcohols, hydrophobic, organosilane

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ACCEPTED MANUSCRIPT 1. Introduction The fast pyrolysis of lignocellulosic biomass, which is regarded as a renewable

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feedstock, has attracted much attention for the production of phenolic bio-oil as a

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promising alternative to fossil fuels [1-8]. However, the direct use of the as-prepared phenolic bio-oil is impossible, because of the unfavorable features of high oxygen content, low energy density, low stability, and high viscosity [9-14]. In order to solve

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these problems, the upgrading of phenolic bio-oil by hydrodeoxygenation strategy has

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been developed to obtain high-quality alkane-oil [10,15]. Typically, the hydrogenation process over combined metal (e.g. Ru, Pt) and acid catalysts (e.g. HCl, acid resins,

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zeolites) contains consecutive steps including hydrogenation of phenolic molecules to

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alcohols, dehydration of alcohols to olefins, and hydrogenation of olefins to alkanes.

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In this process, the hydrogenation and dehydration reactions occurred on the metal and acid sites, respectively. Particularly, the step of acid-catalyzed alcohol

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dehydration is greatly important for the cleavage of C-O bonds, which is reported to be a rate-control step in the bio-oil upgrading process [9]. Therefore, developing highly efficient catalyst for dehydration of alcohols in water solvent is important for obtaining high-quality alkane-oils from biomass [16-20]. Recently, many homogeneous acid catalysts have been found to be active for the dehydration of alcohols, including phosphoric acid and acidic ionic liquids [9, 21]. However, their homogeneous feature produces difficulty in catalyst separation and regeneration from the reaction system. More recently, aluminosilicate zeolites (e.g. ZSM-5, Beta) as typical examples of solid acids have been employed to catalyze the

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ACCEPTED MANUSCRIPT dehydration of alcohols in bio-oil upgrading [22-25]. Because of the obvious advantages of high stability, abundant acidic sites, and heterogeneous feature, zeolites

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are regarded to be one of the most promising catalysts for the dehydration of alcohols.

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However, it should be noted that the catalytic activity of aluminosilicate zeolites still could not satisfy all the requirements of an efficient catalyst, even some methods have already been used to enhance the zeolite activity, high reaction temperature (≥ 150

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C) was still necessary to obtain the olefin products [22, 25].

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In this work, we report an efficient approach method to enhance the catalytic activities of aluminosilicate zeolite in dehydration of alcohols into olefins by

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improving the zeolite hydrophobicity. The hydrophobic zeolites were synthesized by

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an organosilane-modification approach (ZSM-5-OS). The ZSM-5-OS catalysts with

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hydrophobic surface could promote the fast diffusion of water species from the acid sites, and motivate the reaction balance to the formation of olefin products, giving

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10-fold higher activities than the conventional ZSM-5 catalyst. More importantly, the ZSM-5-OS catalyst is stable and shows high activities even after several recycling steps. Furthermore, by combining with Ru nanoparticles, the obtained Ru/ZSM-5-OS catalysts are highly efficient for the direct hydrodeoxygenation of phenolic molecules into alkanes, because of the efficiency of hydrophobic ZSM-5-OS catalysts for dehydration of alcohols, which is a key step in the hydrodeoxygenation processes.

2. Experimental 2.1 Sample preparation

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ACCEPTED MANUSCRIPT All reagents were of analytical grade and used as purchased without further purification. The zeolites are all in H-form.

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Synthesis of ZSM-5 zeolite. As a typical run, 8 ml of tetrapropyl ammonium

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hydroxide (TPAOH, 20 wt%) and 0.09 g of sodium aluminate (NaAlO2) were added into 20 ml of water. After stirring at room temperature for 2 h, 7 ml of tetraethyl orthosilicate (TEOS) was added and the resulted mixture was stirred overnight. Then

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the gel was transferred into an autoclave to crystallize at 180 C for 3 days. After

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filtrating, drying, and calcining at 550 C for 4 h, the ZSM-5 zeolite was obtained. Synthesis of ZSM-5-OS samples. As a typical run, 1g of ZSM-5 was dried at 120

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ºC under vacuum for 3 h, followed by the addition of 50 ml of anhydrous toluene

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containing 1.2 g of organosilane. The mixtures were refluxed overnight and collected

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by rotary evaporation, followed by washing with a large amount of anhydrous toluene and ethanol. The sample obtained was designated as ZSM-5-OS. The experiments

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above were carried out in anhydrous conditions to avoid the reaction between organosilane and H2O. Synthesis of Ru/ZSM-5 and Ru/ZSM-5-OS-C16. As a typical run, 1 g of the ZSM-5 was stirred in 50 ml of RuCl3 solution with desired Ru concentration for 12 h, followed by evaporating the excess water at 80 °C, heating at 100 °C for 12 h, and washing with a large amount of water. Then the solid powder was calcined in air at 400 °C for 2 h, and reduced by H2 at 250 °C for 2 h to obtain Ru/ZSM-5. Ru/ZSM-5-OS-C16 was obtained by modifying Ru/ZSM-5 with n-Hexadecyltrimethoxysilane. By ICP analysis, the Ru loadings were established at

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ACCEPTED MANUSCRIPT 0.78 and 0.81wt% for Ru/ZSM-5 and Ru/ZSM-5-OS-C16, respectively. Additionally, the dispersion of Ru atom (number of Ru atoms on the nanoparticle surface / total Ru

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for Ru/ZSM-5 and Ru/ZSM-5-OS-C16, respectively.

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atoms) was determined by the pulse CO adsorption tests, obtaining 23.3 and 20.1%

2.2 Sample characterization

X-ray diffraction (XRD) data were collected on a Rigaku D/MAX 2550

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diffractometer with Cu KR radiation (=1.5418 Å). Si/Al ratios were determined by

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inductively coupled plasma (ICP) analysis (Perkin-Elmer 3300DV). Nitrogen sorption isotherms were measured using a Micromeritics ASAP 2020 system. The contact

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angles of water and 1-hexene droplets on the solid surface were measured on an

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Optical Contact Angle Meter (SL200KB). Scanning electron microscopy (SEM) was

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performed using a Hitachi SU 1510. FT-IR spectra were recorder on a Bruker 66V FTIR spectrometer. The pulse CO adsorption test was performed on FINETEC

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Finesorb-3010. The adsorption capacity of water and cyclohexanol was tested in a static reactor at room temperature; the solid samples were degased at 180 C under vacuum for 14 h before the test. 50 mg of catalyst was added into a mixture of alcohol (2 mmol) and water (10 ml). Under stirring at room temperature, the concentration of alcohol in water was analyzed by GC analysis using phenol as internal standard. 2.3 Catalytic tests The dehydration reactions were performed in a 100-mL high-pressure autoclave with a magnetic stirrer (900 rpm). The substrate and powder catalyst were mixed in the reactor, then N2 was introduced and kept at desired pressure. The reaction system

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ACCEPTED MANUSCRIPT was heated to a given temperature. After the reaction, the product was taken out from the system and analysed by gas chromatography (GC-17A, Shimadzu, using a flame

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ionization detector) with a flexible quartz capillary column coated with OV-17 and

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FFAP.

The unconverted alcohol substrate and olefin product could be quantified by using dodecane as internal standard. The alcohol conversion and olefin selectivity

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were calculated according to the following equation:

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Conversion = [1 – (mol of unconverted alcohol / mol of alcohol in the starting liquor)] * 100%

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Selectivity = [mol of olefin product / (mol of alcohol in the starting liquor - mol

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of unconverted alcohol)] * 100%

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The hydrodeoxygenation reactions were performed under similar conditions by using H2 in the autoclave. The recyclability of the catalyst was tested by separating it

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from the reaction system by centrifugation, washing with large quantity of ethanol and drying at 100 C for 4 h.

3. Results and Discussion The ZSM-5-OS samples were easily synthesized by modifying the zeolite surface with various organosilane in anhydrous toluene solvent. The samples modified with different organosilanes of dimethyl dimethoxy silane, n-propyltrimethoxysilane, dimethoxydiphenylsilane, and n-hexadecyltrimethoxysilane are denoted as ZSM-5-OS-C1, ZSM-5-OS-C3, ZSM-5-OS-C6, and ZSM-5-OS-C16, respectively.

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ACCEPTED MANUSCRIPT Figure 1A shows the XRD patterns of various synthesized ZSM-5 samples, exhibiting good crystallinities associated with typical MFI structure [26]. Figure 1B shows the

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SEM images of these synthesized ZSM-5 samples, no significant difference in

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morphology was observed before and after the modification treatment. Further analysis show that all ZSM-5 samples have similar surface area (380~415 m2/g, Table 1), Si/Al ratios (33-38, Table 1), and micropore sizes (0.54-0.56 nm, Table S1). These

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the synthesis of ZSM-5-OS samples [26].

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results demonstrated that the structure of ZSM-5 zeolite was well maintained during

Figure 2 shows the FT-IR spectra of the ZSM-5 based samples. Compared the

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spectrum of as-synthesized ZSM-5, the spectra of various ZSM-5-OS samples gave

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significant bands at 2845-2981 cm-1, associating with the C-H bonds of the methyl,

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methene and aromatic groups [27]. Additionally, the ZSM-5-OS-C16 gave additional bands at 779 and 1000 cm-1, associated with the presence of benzene ring [27]. These

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results indicate the successful modification of the organic groups on ZSM-5 zeolite. The loading of organosilane on the samples were studied by total organic carbon (TOC) analysis, obtaining 0.40, 0.33, 0.30, 0.26 mmol/g on ZSM-5-OS-C1, ZSM-5-OS-C3, ZSM-5-OS-C6 and ZSM-5-OS-C16 samples, respectively. Furthermore, the probe reactions of condensation of benzaldehyde with 2-hydroxyacetophenone (CBH) and condensation of benzaldehyde with 1-pentanol (CBP) were performed on the catalysts, which are typical reactions occurring on the external acid sites of ZSM-5 crystals because of the bulky product molecules. Interestingly, the ZSM-5-OS-C1 and ZSM-5-OS-C16 catalysts exhibited much lower substrate conversion than

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ACCEPTED MANUSCRIPT as-synthesized ZSM-5 (See Figure S1 in Supporting Information for details), suggesting the external acid sites of the zeolite crystal are inhibited by the grafting of

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organosilanes. It is noted that the organosilanes should be grafted on the external

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surface of zeolite crystal instead of on the internal framework, because the Sn-OH groups, which reacted with organosilane precursor, are mainly presented on the extern surface. Moreover, we performed water-droplet contact angle test to study the

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hydrophobicity/hydrophilicity of the zeolite samples. The conventional ZSM-5 zeolite

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showed CA of 15, assigning to the hydrophilic surface. Interestingly, after organosilane-modification treatment by dimethyl dimethoxy silane and

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n-propyltrimethoxysilane, the ZSM-5-OS-C1 and ZSM-5-OS-C3 samples showed CA

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of 85 and 88 (Table 1), indicating improvement in the zeolite surface hydrophobicity.

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When dimethoxydiphenylsilan and n-hexadecyltrimethoxysilane were employed in the modification treatment, the obtained ZSM-5-OS-C6 and ZSM-5-OS-C16 showed

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higher CA at 121 and 134 (Table 1), because long-chain alkane groups (C16) and benzene group (C6) are more hydrophobic than the short-chain group (C1 and C3). These results indicate the successfully changed hydrophobicity of the ZSM-5-OS samples by organic group modification method (Figure S2). The study of the catalytic performances of the ZSM-5-OS catalysts started from employing dehydration of cyclohexanol to cyclohexene as a model reaction (Table 2). Interestingly, the ZSM-5-OS catalysts exhibited significantly improved cyclohexanol conversion compared with the conventional ZSM-5 catalyst. For example, as listed in Table 2, the ZSM-5-OS catalysts exhibit cyclohexanol conversion at 56.3-76.0%,

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ACCEPTED MANUSCRIPT much higher than 19.2% over ZSM-5 catalyst under the same reaction conditions. Notably, the ZSM-5-OS-C16 catalyst exhibited the highest cyclohexanol conversion

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(76.0%) than the other ZSM-5-OS catalysts. For comparison, the homogeneous

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H3PO4 catalyst, which is reported to be highly active dehydration catalyst at high temperature (200 C), exhibited a low conversion of 1.2% [21]. Additionally, the conventional acid catalysts, including homogeneous H2SO4 and heterogeneous

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Al-SBA-15 and Amberlyst-15 catalysts all exhibit lower cyclohexanol conversions

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(2.2-19.2%) than ZSM-5-OS-C16. These results indicate the excellent catalytic activities of the organosilane-modified catalysts, especially ZSM-5-OS-C16 catalyst.

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Notably, the turnover frequency (TOF) of ZSM-5-OS-C16 could reach 27.0 h-1 (Figure

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3A), which is 10-fold higher than that (2.5 h-1) of conventional ZSM-5 catalyst.

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Considering that ZSM-5-OS-C16 and conventional ZSM-5 have the same zeolite framework, the superior catalytic activity of ZSM-5-OS-C16 should be attributed to

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the hydrophobic surface, which could efficiently enrich the alcohol substrate and keep water away from the acid sties. These features are favorable for the dehydration reactions, thus promoting the shift of reaction balance to the formation of cyclohexene [21] (Figure S2). We also studied the carbon balance before and after the reaction. After the dehydration of cyclohexanol over ZSM-5-OS-C16 catalyst, by a simple washing with methanol, the carbon balance is analyzed and calculated to be >99.5%. Importantly, the ZSM-5-OS-C16 could be recycled very easily by filtrating from the reaction system, followed by washing and drying. Even in the fifth run, the ZSM-5-OS-C16 catalyst still showed cyclohexanol conversion at 73.4%, which is

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ACCEPTED MANUSCRIPT comparable with the as-synthesized ZSM-5-OS-C16 catalyst (76.0%, Figure 3B). After reaction, the used ZSM-5-OS-C16 catalyst showed a water-droplet CA of 126 (Figure

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3D), which is comparable with that of the as-synthesized catalyst (134, Figure 3C),

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suggesting that the hydrophobic surface is stable during the reaction process. Furthermore, by treating the ZSM-5-OS-C16 catalyst in boiling water for 12 h and filtrating to separate the solid, no organic species were detected by GC analysis in the

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obtained liquor, suggesting no leaching of C16 group. These results confirm the high

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stability and recyclability of ZSM-5-OS-C16 catalyst.

We also studied the catalytic performances of the hydrophobic catalysts in

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dehydration of other alcohols, including cyclopentanol, 2-hexanol, and phenylethyl

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alcohol (Table 2). In all these cases, the ZSM-5-OS-C16 always exhibited much higher

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alcohol conversion (34.4-69.0%) than the conventional ZSM-5 zeolite (4.3-12.2%), indicating the wide substrate scope of ZSM-5-OS-C16 in the dehydration reactions.

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The features of ZSM-5-OS-C16, including wide substrate scope, easy preparation, high stability and recyclability, make it potentially important for the wide application in the future.

The success in alcohol dehydration motivated us to extend the use of ZSM-5-OS-C16 catalyst in the direct hydrodeoxygenation phenol into alkane. The phenol was employed as a bio-oil model molecule (Scheme S1) [9, 21]. By combining with Ru sites, the obtained Ru/ZSM-5-OS-C16 exhibit a cyclohexane yield of 97.9% at 130C in water solvent, which is higher than that (66.4%) over the conventional ZSM-5 supported Ru (Ru/ZSM-5, Figure 3E), and even comparable with the reported

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ACCEPTED MANUSCRIPT highly effective catalysts used at relatively high temperatures (150-220C) [21]. The excellent catalytic performance of ZSM-5-OS-C16 catalyst in phenol

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hydrodeoxygenation is reasonably attributed to the hydrophobic surface, which could

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enhance the activity in cyclohexanol dehydration, a control step in phenol hydrodeoxygenation.

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4. Conclusion

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In summary, the ZSM-5 zeolites with hydrophobic surface were designed and synthesized by an organosilane-modification approach (ZSM-5-OS). The hydrophobic

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ZSM-5-OS catalysts exhibit 10-fold higher catalytic activities than the conventional

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ZSM-5 catalyst, because the hydrophobic surface could efficiently enrich the alcohol

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substrate and keep water away from the acid sties, which are favorable for the dehydration reactions. More importantly, the ZSM-5-OS catalyst is stable and easily

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recyclable. Furthermore, by combining with Ru nanoparticles, the obtained Ru/ZSM-5-OS catalysts are highly efficient for the direct hydrodeoxygenation of phenolic molecules into alkanes, because of the efficiency of hydrophobic ZSM-5-OS catalysts for dehydration of alcohols, a key step in the hydrodeoxygenation processes. It is believed that the approach developed in this work would be potentially important for synthesizing more efficient catalysts for dehydration of biomass feedstocks in the future.

Acknowledgements

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ACCEPTED MANUSCRIPT This work is supported by the Science and Technology Project of General Administration of Quality Supervision, Inspection and Quarantine of the People's

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Republic of China (AQSIQ, No. 2014QK203).

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[27] D.W. Lupo, M. Quack, Chem. Rev. 87 (1987) 181-216.

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Table 1. Dehydration of alcohols to olefins over various catalysts in water solvent.

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Table 2. Catalytic dehydration of alcohols to olefins over various catalysts in water solvent.a

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Figure 1. (A) XRD patterns and (B) SEM images of various ZSM-5 samples. (a)

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Conventional ZSM-5, (b) ZSM-5-OS-C1, (c) ZSM-5-OS-C3, (d) ZSM-5-OS-C6, and

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(e) ZSM-5-OS-C16.

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Figure 2. FT-IR spectra of various samples.

Figure 3. (A) Turnover frequencies (TOFs) of various synthesized catalysts in

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dehydration of cyclohexanol. The reaction conditions are the same to those in Table 2 except reaction time of 20 min. The TOFs are calculated based on the number of Al atoms in the reaction system. (B) Recycle tests of ZSM-5-OS-C16 in the dehydration of cyclohexanol. Water-droplet CA of (C) as-synthesized and (D) recycled ZSM-5-OS-C16 catalyst. (E) Cyclohexane yield of Ru/ZSM-5 and Ru/ZSM-5-OS-C16 in hydrodeoxygenation of phenol to cyclohexane.

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ACCEPTED MANUSCRIPT Table 1. Dehydration of alcohols to olefins over various catalysts in water solvent. Crystal sizes

CA

(m2/g)b

(nm)c

()d

300

15 88

Si/Ala

ZSM-5

--

38

399

ZSM-5-OS-C1

Dimethyl dimethoxy silane (C1)

35

ZSM-5-OS-C3

n-Propyltrimethoxysilane (C3)

ZSM-5-OS-C6

Dimethoxydiphenylsilane (C6)

ZSM-5-OS-C16

n-Hexadecyltrimethoxysilane (C16)

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Organosilane

T

SBET

Sample

290

37

380

309

85

33

415

315

121

35

400

320

134

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388

Molar ratio of Si/Al by (Inductively Coupled Plasma) ICP analysis;

b

BET surface area;

c

Mean sizes of the zeolite crystals, by counting more than 50 crystals in SEM images;

d

Water-droplet contact angle (CA) on the solid surface.

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a

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ACCEPTED MANUSCRIPT Table 2. Catalytic dehydration of alcohols to olefins over various catalysts in water

Selectivity (%)

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Substrate

Product

Catalyst

T(C)

1

ZSM-5

150

19.2

>99.0

2

ZSM-5-OS-C1

150

56.3

>99.0

3

ZSM-5-OS-C3

150

56.7

>99.0

4

ZSM-5-OS-C6

150

67.0

>99.0

5

ZSM-5-OS-C16

150

76.0

>99.0

6

ZSM-5-OS-C16

7 8

10

D

11

TE

12

17 a

AC

16

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13

15

70.7

>99.0

H3PO4

150

1.2

69

H2SO4

150

19.2

97.5

Al-SBA-15

150

2.2

>99.0

Amberlyst-15

150

9.4

>99.0

Benzenesulfonic acid

150

16.9

>99.0

ZSM-5

150

12.2

98.9

ZSM-5-OS-C16

150

69.0

98.1

ZSM-5

150

4.3

>99.0

ZSM-5-OS-C16

150

34.4

>99.0

ZSM-5

165

11.4

>99.0

ZSM-5-OS-C16

165

65.0

>99.0

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9

14

120

b

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Entry

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Conversion (%)

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solvent.a

Reaction conditions: 1 mmol of alcohol, 50 mg of catalyst, 5 ml of water, 3 MPa of N2, reaction time of 20 h. b The data are from Ref. [21].

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(B) a

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(A)

ZSM-5-OS-C1

Intensity

c

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ZSM-5-OS-C6

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ZSM-5-OS-C3

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ZSM-5

d

e

ZSM-5-OS-C16

15 20 25 30 2Theta (Degree)

35

40

D

10

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5

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Figure 1. (A) XRD patterns and (B) SEM images of various ZSM-5 samples. (a) Conventional ZSM-5, (b) ZSM-5-OS-C1, (c) ZSM-5-OS-C3, (d) ZSM-5-OS-C6, and

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(e) ZSM-5-OS-C16.

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2981 2929

IP

SC R

Absorbance

1000 779

2953

ZSM-5-OS-C6 ZSM-5-OS-C3

NU

ZSM-5-OS-C1 ZSM-5

3500

3000

1500

MA

4000

T

2845

ZSM-5-OS-C16

1000 -1

Wave number (cm )

AC

CE P

TE

D

Figure 2. FT-IR spectra of various samples.

20

500

ACCEPTED MANUSCRIPT

60 40 20

Ru/ZSM-5

T

80

Ru/ZSM-5-OS-C16

(D)

SC R

Catalyst

Cyclohexane yield (%)

40

0

0

100

CA=126 

1

2

3 Runs

4

5

0

NU

5

CA=134 

20

ZSM-5

10

60 Conversion (%)

15

ZSM-5-OS-C3

ZSM-5-OS-C1

-1

Catalyst

MA

Figure 3. (A) Turnover frequencies (TOFs) of various synthesized catalysts in dehydration of cyclohexanol. The reaction conditions are the same to those in Table 2

TE

D

except reaction time of 20 min. The TOFs are calculated based on the number of Al atoms in the reaction system. (B) Recycle tests of ZSM-5-OS-C16 in the dehydration

CE P

of cyclohexanol. Water-droplet CA of (C) as-synthesized and (D) recycled ZSM-5-OS-C16 catalyst. (E) Cyclohexane yield of Ru/ZSM-5 and Ru/ZSM-5-OS-C16 in hydrodeoxygenation of phenol to cyclohexane.

AC

TOF (h )

20

ZSM-5-OS-C6

25

(E)

(C)

80

IP

(B)

30 ZSM-5-OS-C16

(A)

21

ACCEPTED MANUSCRIPT

T

Graphical abstract：

AC

CE P

TE

D

MA

NU

SC R

IP

Hydrophobic surface

22

ACCEPTED MANUSCRIPT Research highlights：

IP

T

ZSM-5-OS samples were synthesized by organic-silane modification

SC R

method.

NU

ZSM-5-OS samples have hydrophobic surfaces.

AC

CE P

TE

D

MA

ZSM-5-OS catalysts are efficient for dehydration of alcohols.

23