low-cost synthesis of titanium silicalite-1 (ts-1) with highly catalytic oxidation performance...

Low-Cost Synthesis of Titanium Silicalite‑1 (TS-1) with HighlyCatalytic Oxidation Performance through a Controlled HydrolysisProcessXiujuan Deng, Yuning Wang, Lu Shen, Haihong Wu, Yueming Liu,* and Mingyuan He

Shanghai Key Laboratory of Green Chemistry and Chemical Processes, Department of Chemistry, East China Normal University,North Zhongshan Road 3663, Shanghai 200062, China

*S Supporting Information

ABSTRACT: Titanium silicalite-1 (TS-1) has been successfully synthesized in ultralow molar ratio of TPAOH/SiO2 by two-step and multistep hydrolysis process, where the molar ratio of tetrapropylammonium hydroxide/silica (TPAOH/SiO2) could bereduced to 0.08 and 0.065, respectively. Combined characterization of X-ray diffraction (XRD), N2 adsorption−desorption,scanning electron microcopy (SEM), Fourier transform infrared spectroscopy (FT-IR), UV−vis spectroscopy, and thermalgravimetric (TG) analysis shows that currently synthesized TS-1 samples have the typical “blackberry” morphology, and theparticle size is around 300−400 nm, similar to that of the conventional TS-1 synthesized at a high molar ratio of TPAOH/SiO2(>0.18). Additionally, currently synthesized TS-1 exhibits excellent catalytic oxidation performance in epoxidation of alkene andammoximation of ketone, even better than that of conventional TS-1. Obviously, fast hydrolysis of a small part of TEOS at a highconcentration of TPA+ in the first step induces more nuclei, which in turn accelerates crystallization in the subsequent step.Therefore, effective utilization of TPAOH to build the TS-1 framework is significantly increased. This strategy can greatly reducethe synthesis cost of TS-1, which is suitable for synthesis of TS-1 on an industrial scale.

1. INTRODUCTIONTitanium silicate-1 (TS-1), an active and environmentallyfriendly catalyst, has been widely used as a heterogeneousoxidation catalyst in various processes, such as epoxidation ofalkenes, oxidation of alkanes and alcohols, hydroxylation ofaromatics, and ammoximation of ketones using aqueous H2O2solution as a mild oxidant.1−3 Among these reactions,ammoximation of cyclohexanone, epoxidation of propylene,and hydroxylation of phenol have been successfully carried outindustrially.3

Physicochemical properties of TS-1 including purity,crystallinity, loading of framework Ti(IV), surface hydro-phobicity, particle size, and morphology play a crucial role inthe catalytic oxidation reactions.4−17 To synthesize TS-1 withhigh performance, it is necessary to integrate the several factorsabove. It is worth mentioning that high catalytic activity isobtained with nanosized TS-1 particles of ca. 300 nmcomposed of the aggregated primary crystallites (about 20−30 nm) with blackberry morphology,18,19 while larger TS-1particles (>1 μm) show much lower activity due to the diffusionlimitation of organic molecules. However, synthesis of TS-1with high catalytic activity has to use tetrapropylammoniumhydroxide (TPAOH) as the template with a molar ratio ofTPAOH/SiO2 larger than 0.25,1,3,12,14−16,20 which is propitiousto form nanosized TS-1 particles. To cut the cost of thesynthesis of TS-1, many efforts have been devoted to the use ofinexpensive small organic amine as template instead ofexpensive TPAOH. Although the use of inexpensive smallorganic amine to replace expensive TPAOH, such as TPABr,ammonia, diethylamine, hexanediamine, ethylenediamine, n-butylamine, is a promising strategy to synthesize low-cost TS-1,these materials only showed medium chemical reactivity in the

catalytic oxidation reaction in most cases much lower than thatof TS-1 synthesized using TPAOH as template.21−25 It is worthnoting that although a large amount of TPAOH is used in thehydrothermal synthesis, only a small amount of TPA+ cations isoccluded in the channel of TS-1 crystallites (at most 4molecules per unit cell), corresponding to a minimum molarratio of TPA+/SiO2 of ∼0.042.26,27 Therefore, synthesis of high-performance TS-1 at a low concentration of TPAOH is highlypossible as proposed here.From the aspect of industrial application and green

chemistry, preparation of TS-1 with superior catalytic proper-ties by a cheaper and more environmentally friendly process isstrongly desirable. Herein, we carried out hydrothermalsynthesis of TS-1 with a lower ratio of TPAOH/SiO2 in two-step and multistep hydrolysis processes by finely tuning thenucleation and growth step during crystallization. In the firststep, the relatively high TPAOH/SiO2 ratio provides highalkalinity for fast hydrolysis and condensation of silica speciesand thus leads to formation of more secondary building units(SBUs) and/or even nuclei. These SBUs and/or nuclei favorformation of small TS-1 crystallites in the subsequent step.That makes maximum use of TPA+ and prevents furtheraccretion of the crystal in the low ratio of TPAOH/SiO2. Thesample shows good activity in the oxidation of alkene andammoximation of ketone compared to the conventional TS-1synthesized under a higher ratio of TPAOH/SiO2. This processgreatly reduces consumption of the expensive TPAOH to

Received: September 12, 2012Revised: December 25, 2012Accepted: December 30, 2012Published: December 30, 2012

Article

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produce high-performance TS-1, which will promote industrialapplication of TS-1.

2. EXPERIMENTAL SECTION2.1. Source of Chemicals and Materials. Tetraethyl

orthosilicate (TEOS) was from Sinopharm Chemical ReagentCo., Ltd.; tetrabutyl orthotitanate (TBOT) was from ChinasunSpecialty Products Co., Ltd.; tetrapropylammonium hydroxide(TPAOH) was from Sinopec Co., Ltd.; allyl chloride (ALC)was from Alfa Aesar (Tianjin) Chemical Co., Ltd.; 1-hexene(97%) was from J&K Scientific Ltd.; cyclohexanone, tert-butanol, H2O2 (about 30 wt %), and NH3 were all industrial-grade reagents (Shanghai Lingfeng Chemical Reagent Co. Ltd.,China).2.2. Preparation of T-TS-1-x-y and Conventional C-TS-

1-x. A typical synthesis of TS-1 (named T-TS-1-x-y) in a two-step hydrolysis method is as follows.In the first step, a mixture of partial TEOS and all TBOT was

added dropwise into TPAOH solution under stirring at roomtemperature. After hydrolyzing at 323 K for 30 min andremoving alcohols by evaporation at 353 K, the obtained clearsol has the following molar composition: 1.0SiO2:(0.33−0.75)TiO2:xTPAOH (x = 0.08−0.18):18 H2O.In the second step, when the sol was cooled down, the

remaining TEOS was added dropwise. Then the final sol washeated to hydrolyze and alcohols were removed repeatedly.The composition of the final sol was maintained in the range of1.0SiO2:0.33TiO2:yTPAOH (y = 0.065−0.12):18 H2O. Then itwas transferred into a Teflon-lined stainless-steel autoclave andcrystallized at 443 K for 2 days. Afterward, the product wasrecovered by filtration, washed with distilled water, dried at 363K overnight, and finally calcined at 823 K for 6 h.When partial TEOS was added into the solution in the first

step and then the mixture of remanent TEOS and all TBOTwas added dropwise in the second step, the synthesized samplewas named T′-TS-1-x-y.The first-step synthesis in the multistep hydrolysis method is

the same with the two-step hydrolysis method. In the sequencestep, the remaining TEOS hydrolyzes while the remainder isadded dropwise into solution (sample named M-TS-1-x-y).Conventional TS-1 (named C-TS-1-x) was synthesized

through a one-step hydrolysis process,1,28 basically accordingto the procedures of the first step of T-TS-1-x-y. The molarcomposition of the final sol is 1.0SiO2:0.33TiO2:x TPAOH (x= 0.08−0.18):18 H2O2.3. Characterization Methods. X-ray diffraction (XRD)

patterns were collected on a Rigaku Ultima IV diffractometerusing Cu Kα radiation and a nickel filter in the 2θ angle rangefrom 5° to 35° at 35 kV and 25 mA. Scanning electronmicroscopy (SEM) images were taken on a Hitachi S-4800microscope. Thermogravimetric and differential thermalanalyses (TG-DTA) were performed on a METTLERTOLEDO TGA/SDTA851e apparatus from room temperatureto 1073 K at a heating rate of 10 K min−1 in air. UV−vis spectrawere recorded on a Shimadzu UV-2400PC spectrophotometerusing BaSO4 plate as a reference. FT-IR spectra were measuredon a Thermo Scientific Nicolet Nexus 670 Fourier transforminfrared spectrometer using the KBr technique (3 wt % TS-1 inKBr). Inductively coupled plasma (ICP) atomic emissionspectroscopy was performed on a Thermo IRIS Intrepid II XSPatomic emission spectrometer. Surface area was measured byN2 adsorption at 77 K on an Autosorb Quantachrome 02108-KR-1 analyzer after evacuation at 573 K for 5 h.

2.4. Catalytic Reactions. Epoxidation of alkene (1-hexeneand ALC) with H2O2 was carried out in a 50 mL round-bottomed flask equipped with a reflux condenser. It was mixedwith 50 mg of catalyst, 10 mL of solvent (methanol), 10 mmolof alkene, and 10 mmol of H2O2 (30 wt % aqueous solution)under vigorous stirring at 333 K for 2 h. The product of thereaction was analyzed on an Agilent GC-7890A gas chromato-graph equipped with a DB-WAX capillary column (30 m × 320μm × 0.25 μm) and an FID detector using cyclohexanone as aninternal standard. The amount of residual H2O2 wasdetermined by titration with 0.05 M Ce(SO4)2 solution.Ammoximation of cyclohexanone was carried out in a

continuous slurry reactor.29 A suitable amount of TS-1 powder(3.2 g), 73 g of t-BuOH aqueous solution (85 wt %), and 24 gof H2O were added in the reactor and heated under stirring at349 K. The molar ratio of H2O2/ketone was 1.1, and the molarratio of NH3/ketone was 1.7. The organic products wereanalyzed by GC (the same condition with 1-hexene oxidation)to calculate conversion of cyclohexanone and the selectivity ofoxime. The content of unconverted H2O2 was determined byiodometric titration with 0.1 M Na2S2O3 solution.

3. RESULTS AND DISCUSSION3.1. Preparation and Characterization of TS-1 with

Different TPAOH/SiO2 Ratio. 3.1.1. Comparison betweenthe Conventional Synthesis System and the Two-StepHydrolysis Method. Figure 1 shows the X-ray diffraction

(XRD) patterns of the T-TS-1-x-y and C-TS-1-x samples. Allsamples show typical MFI phase as reported in the literature.1

In the case of C-TS-1-x, the relative crystallinity of TS-1appreciably decreases with the TPAOH/SiO2 ratio lowering.However, T-TS-1-0.18-y shows no obvious loss of crystallinitywith the final TPAOH/SiO2 ratio of y decreasing, as shown inFigure 1e−g. Even T-TS-1-0.18-0.08 is highly crystallized.

Figure 1. XRD patterns of the uncalcined TS-1 samples at differentTPAOH/SiO2 ratio: (a) C-TS-1-0.18, (b) C-TS-1-0.12, (c) C-TS-1-0.10, (d) C-TS-1-0.08, (e) T-TS-1-0.18-0.12, (f) T-TS-1-0.18-0.10, (g)T-TS-1-0.18-0.08.

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Moreover, the yield of solid product obtained by theconventional or two-step hydrolysis method is more than 90%.The Ti coordination state of TS-1 is investigated with UV−

vis spectroscopy (Figure 2). All T-TS-1-x-y and C-TS-1-0.18

samples show similar spectroscopy, where tetrahedral Ti (210nm) dominates, octahedral Ti (260 nm) is hardly observed, anda small amount of anatase (330 nm) is present. Furthermore,the band at 960 cm−1 in IR spectra indicates the presence of Tiatoms in tetrahedral coordination within the silicalite frame-work30,31 (Figure S1, Supporting Information). Meanwhile,there is a typical band near 550 cm−1 observed in IR spectra,which is due to the stretching vibration of structural doublefive-membered rings. All these data suggest that most of the Tiatoms have been incorporated into the framework to formisolated tetrahedral Ti(IV) species.31

SEM images of TS-1 prepared by two-step hydrolysis and theconventional method are displayed in Figure 3. Compared with

C-TS-1-x, T-TS-1-x-y presents remarkable changes in particlesize and morphology. As the ratio of TPAOH/SiO2 increasesfrom 0.08 to 0.18, the particle size of C-TS-1-x decreases fromabout 3−4 μm to 300 nm (Figure 3a−c). Meanwhile, C-TS-1-xexhibits different morphology from the coffin particles (Figure3c) to round-shaped conglomeration (Figure 3a and 3b). Thisis related to the ratio of TPAOH/SiO2 varying. Duringformation of colloidal sol, the low TPAOH/SiO2 ratio easilydecelerates the nucleation rates, forms less nuclei, and thusleads to larger crystals.32 However, the particle size change of

T-TS-1-x-y ranges from 400 (TPAOH/SiO2 = 0.12) to 900 nm(TPAOH/SiO2 = 0.08) (Figure 3d−f). In the same ratio ofTPAOH/SiO2, the particle size of T-TS-1-x-y is smaller than C-TS-1-x. This further proves that the two-step hydrolysismethod does accelerate the nucleation rate.As shown in Figure 4, the TG curve of T-TS-1-0.18-0.08 is

quite different from those of both C-TS-1-0.18 and C-TS-1-

0.08, indicating different states of TPAOH in these samples. C-TS-1-0.08 and C-TS-1-0.18 exhibit two main weight loss peakscentered at about 473 and 653 K in TG curves (Figure 4a and4b). The peak at 473 K originates from decomposition ofTPA+, which is physically adsorbed on the particle externalsurface, while the peak at 653 K is attributed to decompositionof TPA+ tightly filled in the pore channel of the zeoliteframework.33 The weight loss of C-TS-1-x owing todecomposition of TPAOH increases with increasingTPAOH/SiO2 ratio. The minimum theoretical amount ofTPAOH required to crystallize TS-1 corresponds to TPA+/SiO2 = 0.042.26 When the ratio of TPA+/SiO2 is greater than0.042 in the sol, some of the excessive TPAOH would beadsorbed at the surface of zeolite in the case of C-TS-1-0.18and C-TS-1-0.08. It is interestingly noted that T-TS-1-0.18-0.08shows only one weight loss peak at 653 K, while the peak at473 K in C-TS-1-x assigned to decomposition of physicallyadsorbed TPA+ cations scarcely exists, and the weight loss of T-TS-1-0.18-0.08 at 653 K (11.2%) is similar to C-TS-1-0.18sample (10.9%). The result of TG analysis implies thatTPAOH molecules in the synthesis of T-TS-1-x-y are fullyused as template. However, in the conventional synthesis of TS-1, only part of the TPAOH molecule involves nucleation andcrystallization of TS-1, which indicates that the two-stephydrolysis system improved effective utilization of TPAOH asstructure-directing agents (SDA).The textural properties of TS-1 samples are tested by N2

adsorption/desorption measurement. T-TS-1-0.18-0.08 exhibitshigher BET surface area (452 m2 g−1) and microporous porevolume (0.19 cm3 g−1), similar to that of C-TS-1−0.18 (461 m2

g−1, 0.18 cm3 g−1) synthesized at a high concentration ofTPAOH, however, much larger than that of C-TS-1-0.08 (386m2 g−1, 0.09 cm3 g−1) at a low concentration of TPAOH.

Figure 2. UV−vis spectra of the calcined TS-1 samples at differentTPAOH/SiO2 ratio: (a) C-TS-1-0.18, (b) T-TS-1-0.18-0.12, (c) T-TS-1-0.18-0.10, (d) T-TS-1-0.18-0.08.

Figure 3. Representative SEM images of the calcined TS-1 samples atdifferent TPAOH/SiO2 ratio: (a) C-TS-1-0.18, (b) C-TS-1-0.12, (c)C-TS-1-0.08, (d) T-TS-1-0.18-0.12, (e) T-TS-1-0.18-0.10, (f) T-TS-1-0.18-0.08.

Figure 4. TG curves of the uncalcined TS-1 samples: (a) C-TS-1-0.18,(b) C-TS-1-0.08, (c) T-TS-1-0.18-0.08.



3.1.2. Synthesis of TS-1 with Lower TPAOH/SiO2 inMultistep Hydrolysis Process. To understand the hydrolysisprogress in depth, the controlled multistep hydrolysis strategyis designed to synthesize TS-1 with high performance. Weobserved that, under a low ratio of TPAOH/SiO2 = 0.08, theparticle size of M-TS-1-0.18-0.08 is about 300−400 nm (Figure5a), much smaller than that of T-TS-1-0.18-0.08 synthesized by

the two-step hydrolysis method (Figure 3f, 800−900 nm). Evenunder a lower ratio of TPAOH/SiO2 = 0.065 small particles(Figure 5b, about 400 nm) could be produced by the multistephydrolysis method, while TS-1 could not be obtained by theconventional method. The above results imply that themultistep hydrolysis strategy is also suitable to synthesizehigh-performance TS-1 at a low concentration of TPAOH.3.2. Incorporation of Active Ti Sites in the Synthesis.

The coordination environment of active titanium plays animportant role in the catalytic activity of titanosilicate molecularsieves.4,33 The UV−vis spectra in Figure 6 provide direct

evidence on the coordination geometry of Ti atoms in C-TS-1-x and T-TS-1-0.18-0.08. All samples show the main absorptionat 210 nm, which represents tetrahedrally coordinated Ti in theframework. In the UV−vis spectra of C-TS-1-x, the absorptionat 330 nm is observed with a Si/Ti ratio of about 30 (Figure6a), while it disappears with a low amount of Ti (e.g., Si/Ti =60, Figure 6b). In the two-step synthetic protocol, TBOT couldbe added either in the first step or in the second step. The peakof 330 nm is not observed in both cases, as shown in Figure 6c

and 6d. Interestingly noted, the Ti coordination state does notchange with different feeding sequence of TBOT but dependson the molar ratio of Si/Ti in the final composition.

3.3. Crystallization Mechanism of TS-1 Zeolite. Tounderstand why the two methods led to different particle sizesin the same ratio of TPAOH/SiO2, it is necessary to make theircrystallization mechanism clear. Figure 7 shows the crystal-

lization curves for different synthesized systems. At a high ratioof TPAOH/SiO2 = 0.18, the rates of nucleation andcrystallization are very quick in the conventional system(Figure 7a). The relative crystallinity reaches >95% aftercrystallization at 443 K for 2 h. Crystallization proceeds fast, sothe nuclei would possibly congregate to elliptical particles.When the concentration of TPAOH decreased, a longerinduction and crystallization period are observed for C-TS-1-0.08 (Figure 7b). This indicates that the rates of nuclei andgrowth are significantly reduced, so that large particles (about3−4 μm) finally formed. Obviously, at a TPAOH/SiO2 ratio of0.08, the two-step hydrolysis method (Figure 7c) acceleratesnucleation and crystallization compared with C-TS-1-0.08. Inthe first-step hydrolysis, high TPAOH concentration leads tohydrolysis and condensation of TEOS faster, which benefitsformation of enough nuclei. When remaining TEOS is added,the presence of nuclei catalyzes its further condensation.Compared with C-TS-1-0.08, more nuclei exist in the crystalsystem, shortening the nucleation time and acceleratingcrystallization.Nucleation and growth of zeolite is a quite complicated and

an unpredictable process. Many comprehensive and thoroughinvestigations are conducted in the hydrothermal synthesis ofzeolite.35−37 It has been widely accepted that more nuclei resultin smaller size particles and vice versa. Figure 8 exhibits thegrowth process of TS-1 under different conditions. First, TEOSis hydrolyzed to a structural unit through catalysis of OH−. Atthe same time the units rearrange around TPA+ and thencondense to nuclei. A lower concentration of OH− leads to aslower rate of nucleation, indicating less nuclei formation.Therefore, the precursor sol includes nuclei and someamorphous phase.32 In the case of C-TS-1-x, a low TPAOH/SiO2 ratio leads to a slow rate of nucleation and growth andthus large regular lump crystals under hydrothermal conditions(Figure 8a). More nuclei are formed at a high ratio of TPAOH/SiO2 (Figure 8b) and then congregate to secondary particles(about 30−40 nm). In addition, particles with a rough surfaceare formed finally. However, in the two-step hydrolysis system(Figure 8c), a large quantity of nuclei are formed in a high ratio

Figure 5. SEM images of the calcined TS-1 samples: (a) M-TS-1-0.18-0.08, (b) M-TS-1-0.18-0.065.

Figure 6. UV−vis spectra of the calcined TS-1 samples obtained underdifferent conditions: (a) Si/Ti = 30, C-TS-1-0.18; (b) Si/Ti = 60, C-TS-1-0.18; (c) Si/Ti = 60, T-TS-1-0.18-0.08, Ti source added in thefirst step; (d) Si/Ti = 60, T′-TS-1-0.18-0.08, Ti source added in thesecond step.

Figure 7. Crystallization curves of TS-1 samples under differentconditions: (a) C-TS-1-0.18, (b) C-TS-1-0.08, (c) T-TS-1-0.18-0.08.



of TPAOH/SiO2 at a very short time. Upon addition ofremnant TEOS, autocatalytic nucleation could occur due to thenuclei formed in the first step as “seed”, which significantlyreduces the amount of TPAOH used. More nuclei includingthose formed during both steps can lead to aggregate tosecondary particles with reduced size.37 Therefore, at a lowconcentration of TPAOH, the high-performance TS-1 withblackberry morphology is obtained.3.4. Catalytic Activity. The catalytic activity of TS-1

depends on the amount of framework Ti, particle size, andrelative crystallinity. All samples are crystallized well and have asimilar Si/Ti ratio of 30 and framework Ti coordination, whilethe particle size is varied. C-TS-1-x shows different activity inalkenes expoxidation (data listed in Table S1, SupportingInformation). Conversion of alkene decreases from ∼25.0% to12.0% for 1-hexene and from ∼75% to 32.6% for ALC withparticle size increasing (Table S1, Supporting Information, Nos.1−6). When the particle size of TS-1 is less than 300−400 nm,its oxidation activity reaches a high level and does not changedistinctly, consistent with previous reports.18,19 Due to thesmall particle size, T-TS-1-x-y (Table S1, SupportingInformation, Nos. 8−10) and M-TS-1-x-y (Table S1,Supporting Information, Nos. 11 and 12) show higheroxidation activity than the corresponding C-TS-1-x synthesizedat the same ratio of TPAOH/SiO2 in the final clear sols. Theactivity of T-TS-1-0.18-0.10 (Table S1, Supporting Informa-tion, No. 9) is as high as that of C-TS-1-0.18 (Table S1,Supporting Information, No. 2). Moreover, it is worthmentioning that M-TS-1-0.18-0.065 (Table S1, SupportingInformation, No. 12) has a similar oxidation activity to C-TS-1-0.18, which is prepared at a TPAOH/SiO2 ratio of 0.065, closeto the theoretical ratio of 0.042 for synthesis of TS-1.26

Besides the high catalytic activity in the oxidation of olefins,the lifetime and recycling of catalyst is another extremelyimportant parameter to evaluate catalyst performance. Figure 9shows that T-TS-1-0.18-0.10 exhibits a similar ammoximationlifetime of about 106 h with that of C-TS-1-0.18. The

conversion and oxime selectivity of the ammoximation underoptimized conditions reach >97% and ca. 100%, respectively. Insummary, TS-1 synthesized through controlled hydrolysisprocessing at an extremely low concentration of TPAOHshows high catalytic oxidation performance, even better thanthat of conventional TS-1 zeolites.

4. CONCLUSIONTS-1 zeolite has been successfully synthesized under a low ratioof TPAOH/SiO2 via a two-step or multistep hydrolysismethod. The morphology and particle size are adjustable bycontrolling the TPAOH/SiO2 ratio in synthetic sols. In the firststep, a high ratio of TPAOH/SiO2 leads to hydrolysis andcondensation of TEOS faster, which benefits formation ofenough nuclei. When remaining TEOS is added, the nucleiformed in the first step as seeds further catalyze the nucleationand crystallization of TS-1. Therefore, the amount of TPAOHas template is significantly decreased. Currently, TS-1synthesized in this study shows comparable catalytic activitiesin epoxidation of alkenes and ammoximation of ketone withconventional TS-1. On the basis of the obtained high-

Figure 8. Scheme of possible crystallization process: (a) low amount of TPAOH (C-TS-1-0.08), (b) high amount of TPAOH (C-TS-1-0.18), (c)high amount of TPAOH for hydrolysis, low TPAOH amount for crystallization (T-TS-1-0.18-0.08).

Figure 9. Ammoximation of cyclohexanone on different TS-1 samples:(a) C-TS-1-0.18, (b) T-TS-1-0.18-0.10.



performance TS-1 at the same product yield, the molar ratio ofTPAOH/SiO2 can be 0.10 and 0.08 in the two-step andmultistep hydrolysis method and the amount of TPAOHreduced about 44% and 55% compared with the conventionalmethod, respectively. Thus, this method is a cheaper and moreenvironmentally friendly process, which will promote theindustrial application of TS-1. In addition, the synthesisprotocol should be applicable to prepare other types of zeoliteswith varied topological structures, such as beta (BEA), ZSM-11(MEL), MCM-22 (MWW), etc., which are also synthesized at ahigh concentration of organic structure-directing agents.

■ ASSOCIATED CONTENT

*S Supporting InformationIR spectra of samples and catalytic results in alkeneepoxidation. This material is available free of charge via theInternet at http://pubs.acs.org.

■ AUTHOR INFORMATION

Corresponding Author*Tel./Fax: 86-21-62232058. E-mail: [email protected].

NotesThe authors declare no competing financial interest.

■ ACKNOWLEDGMENTS

The authors gratefully acknowledge financial support from theNational Science Foundation of China (20973064), NationalKey Technology R&D Program (2012BAE05B02), Science andTechnology Commission of Shanghai Municipality(12JC1403600), and Shanghai Leading Academic DisciplineProject (B409).

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low-cost synthesis of titanium silicalite-1 (ts-1) with highly catalytic oxidation performance...

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