Synthesis of mesoporous silica-included heteropolyacids materials and the utilization for the alkylation of phenol with cyclohexene

Accepted Manuscript Synthesis of mesoporous silica-included heteropolyacids materials and the utilization for the alkylation of phenol with cyclohexene Yongxing Yang, Guangqiang Lv, Wei Guo, Limin Zhang PII:

S1387-1811(17)30739-4

DOI:

10.1016/j.micromeso.2017.11.018

Reference:

MICMAT 8653

To appear in:

Microporous and Mesoporous Materials

Received Date: 27 September 2017 Revised Date:

25 October 2017

Accepted Date: 8 November 2017

Please cite this article as: Y. Yang, G. Lv, W. Guo, L. Zhang, Synthesis of mesoporous silica-included heteropolyacids materials and the utilization for the alkylation of phenol with cyclohexene, Microporous and Mesoporous Materials (2017), doi: 10.1016/j.micromeso.2017.11.018. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

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Graphical Abstract

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Synthesis of mesoporous silica-included heteropolyacids materials and the utilization for the alkylation of phenol with cyclohexene

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Yongxing Yanga*, Guangqiang Lvb*,Wei Guoa & Limin Zhangc

School of Chemistry and Chemical Engineering, Shanxi University, Wucheng Road 92,

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Taiyuan, 030006, People’s Republic of China b

School of Chemistry and Pharmaceutical Engineering, Qilu University of Technology, Jinan, 250353, People’s Republic of China

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School of Chemistry and Material Science, Shanxi Normal University, Linfen, Shanxi 041004, People’s Republic of China

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*Corresponding author: Fax: +86 351 7011600; Tel.: +86 351 7011600 , E-mail: [email protected]; [email protected]

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ACCEPTED MANUSCRIPT Abstract Mesoporous silica-included heteropolyacids materials were synthesized and characterized by nitrogen sorption, XRD, FT-IR, TEM and NH3-TPD. Characterization results show that silica

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included heteropolyacids is a kind of Bronsted acid catalyst possessing large surface area, suitable pore structure, appropriate acid strength and high acid density. These materials are used as solid catalysts for the alkylation of phenol with cyclohexene. The mesoporous channel

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facilitates not only the dispersion of Bronsted acidity centers but also the transport of reactant and product molecules, thus leading to a significantly improved catalytic performance. Through

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adjusting the interaction between the support pore channel surface and heteropolyacid acive species, different acidity amount and strength can be obtained, leading to the tunable selectivity to the alkylation of phenol with cyclohexene. The improvement of reusability of silica-included HPA catalyst was related to the uniform dispersion of HPA and the enhanced interaction between

Phenol, Cyclohexene, Lignin, Heteropolyacids, Heterogeneous Reaction

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Keywords:

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HPA and the support. In six cycles of the catalyst, a stable activity could be mainttained.

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ACCEPTED MANUSCRIPT 1. Introduction With the fossil fuel resources gradually dwindling and carbon dioxide emission control more and more stringent, urgent request for renewable energy and materials is drawing in more

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and more research & development effort for the production of transportation fuel and fine chemicals from biomass resource for a sustainable economy for the following decades. Flash pyrolysis of the lignin will yield abundant amount of the phenol and its derivative. Phenol

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derived from lignin biomass sources via flash pyrolysis has been envisaged as an important platform chemical for the biorefinery. Phenol and its derivatives can be applied as platform

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chemicals, precursor for fuel, polymers or solvent [1-3]. By selective hydrogenation, phenol could transform into cyclohexene, which is an idea alkylated agent for coupling reaction. Alkylation of phenol with cyclohexene could result in cyclohexyl phenol and cyclohexyl cyclohexylphenyl ether products. Cyclohexyl phenol is a vital organic chemical compound,

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which could be easily transformed into cyclohexyl cyclohexane after hydrodeoxygenation process. Cyclohexyl cyclohexane process excellent fuel property and could be act as the high value rocket fuel. Cyclohexyl cyclohexylphenyl ether itself could be used as high value blending

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component and directly mixed with commercial liquid transportation fuels. So alkylation of phenol with cyclohexene for cyclohexyl phenol and cyclohexyl cyclohexylphenyl ether

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production is a very potential solution for the clean production to replace the current fossil fuel resources production procedure. It also could achieve the value-added utilization of the limiting lignin biomass resources [4-7]. It is well known that the heterogeneous catalysts display many benefits over homogeneous

catalysts, including convenient separation from catalysis system, catalyst recovery and more compatible with the facilities. So the heterogeneous catalysts system is easily been accepted from practical view. Heteropolyacids (HPAs) are versatile solid acids. They are able to activate many typical and important chemical reaction process[8, 9]. Heteropoly acid catalysts are 3

ACCEPTED MANUSCRIPT tremendous and environment friendly acid catalyst and have ability to tolerate contaminations of oil resources such as water contents and free fatty acids (FFAs) contents. Keggin-type heteropoly acids are easily available and having stable structure while heteropoly acids are included in super acid class, due to these reasons heteropoly acids are considered as best acidic catalysts for

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biodiesel production by catalytic transesterification process[9]. In our previous works[10, 11], Supported-heteropolyacid is easily used as an efficient catalyst for the ethylation of phenol with bioethanol to obtain value-added products[11]. Through adjusting the loading amount, different

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acidity amount and strength can be obtained, leading to the tunable selectivity to the phenol ethylation route and regioselectivity. Silica-included heteropolyaicds were prepared and applied

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in fructose dehydration reaction in aqueous and biphasic system[10]. HSiW/SiO2 and water-MIBK reaction system is effective to get a high fructose conversion and HMF yield. But from practical view, the HPAs solid acids also display many drawbacks. For example, they have inferior catalytic stability and the specific surface area of the HPAs solid acids is commonly not

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high. After reaction, the catalyst is very difficult to separation from catalysis system due the HPAs solid acids solubility in many organic solvent [12]. In order to increase the specific area of HPAs and meanwhile obtain good stability and recyclability, methods for the preparation of

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silica-included HPAs materials have been developed. Post-synthesis grafting method[13] and direct co-condensation sol–gel method[14] are typical methods developed for the preparation of

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silica-included HPAs materials. The typical post-synthesis grafting will result in many disadvantages such as low active species loading, active species leak, which will further result in the worse catalytic performance. And the micropore structure is inevitable due to the absence of the template. The loss of the active species is inevitable due to the harsh reaction condition. The synthesis of novel HPAs catalyst with proper pore channel and good recyclability property is still a very attractive research area. With surfactant assistance, it will be very promising to synthesize HPA materials with

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ACCEPTED MANUSCRIPT ordered mesoporous structure. It could be expected these HPA materials could possess excellent catalytic performance for the alkylation of phenol with cyclohexene. In present work, based on the synthesis method of the silica ordered mesoporous material SBA-15, silica-included H3PW12O40 materials with mesopore channel, high specific surface area(＞800m2/g) and uniform

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pore size distribution were synthesized due to the participation of P123. The resultant materials were acted as solid acid catalysts for the alkylation of phenol with cyclohexene. And the catalytic performance of those materials was investigated for the alkylation of phenol with cyclohexene. It

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was found that these new silica-included HPA materials show remarkably high catalytic activity

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and stability in this reaction system.

2. Experimental 2.1 material synthesis

Phenol (95%), cyclohexene (99%), H3PW12O40 (HPA) and tetraethyl orthosilicate

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(analytical grade) and P123 (MW 5800) were purchased from Aldrich company and Kermel chemical reagent company (Tianjin, China), respectively. All reagents were used as purchased

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without further purification. Silica-included HPAs (denoted as HPA/SiO2 below) with controllable H3PW12O40 loadings (5.0-40 wt%) prepared by a direct sol–gel hydrothermal

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method in the presence of triblock poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) copolymer (Pluronic P123, Sigma). In a typical preparation, P123 was dissolved in ethanol at room temperature, and TEOS was diluted with ethanol. In another container, the desired amount of H3PW12O40 was dissolved with water. The above TEOS/EtOH solution and aqueous H3PW12O40 solution was added dropwise into the P123/EtOH solution, respectively, at room temperature. Stirring was used throughout the process. The acidity of the mixture was controlled at pH 1.0 by HCl. After homogenizing the mixture for 3 h, the clear sol was subjected to hydrothermal treatment at 120 oC for 48 h. The resulting hydrogel was dehydrated (45 oC, 25 5

ACCEPTED MANUSCRIPT Torr, 1h), heat-treated (150 oC, 25 Torr, 5 h), ground into 60-100 mesh, refluxed in boiling absolute ethanol, and then calcined again (150 oC, 25 Torr, 3 h).

2.2. Catalysts characterization and testing

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The nitrogen sorption experiments were performed at 77 K on a Quadrasorb system. XRD patterns of the catalysts were recorded with a Philips PW 3040/00 X’Pert MPD/MRD

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diffractometer using Cu Kα radiation operated at 45 kV and 40 mA. The acidity of the samples was determined by temperature programmed desorption of ammonium (TPD-NH3) and were

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performed in a Micromeritics AUTOCHEM 2910 equipment, loading 100-mg of sample in a quartz U-tube reactor. After removing weakly physisorbed NH3 by flowing helium (50 ml/min) for 30 min, the chemisorbed ammonia was determined TCD by heating at 15 ºC/min up to 800 ºC under the same flow of helium. FTIR spectra (4000~400 cm-1) for different AC samples were

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recorded on a Nicolet Impact 410 FTIR spectrometer (Nicolet Instrument Corporation). The spectra were obtained by scans of 64 with a resolution of 4 cm-1. TEM images of the catalysts

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were taken using a PHILIPS TECNAI 20T instrument, working at 200 kV. In typical procedures, 0.02 mol phenol, 0.03 mol cyclohexene, 40 mL heptane solvent and

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0.5 g catalyst were charged in an 60 mL stainless steel vessel with a Teflon lining and sealed by a screw cap. A thermostatic oil bath was used as heating source. Experiments were conducted at 170-230 oC to investigate the effect of reaction temperature. Samples were filtered with a 0.45 µm syringe filter prior to analysis. All of the data were based on repeated runs. Liquid samples collected at 0.5 h intervals were analyzed off-line by gas chromatograph (SHMADZU, GC2010-plus)

equipped

with

a

flame

ionization

detector

and

an

Rtx-1

(100m×0.25mm×0.5µm) capillary column. 6

PONA

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3. Results and discussion 3.1 Physicochemical characterization of the catalysts Fig 1 shows the nitrogen adsorption-desorption isotherm curves and the mesopore size

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distribution calculated by Barrett-Joyner-Halenda(BJH) method of HPAs/SiO2 samples with different HPA loadings. As shown in Fig.1a, the HPAs/SiO2 samples with different HPA loadings display similar isotherms profile (type IV) and H1 hysteresis loop could be observed clearly. It is

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characteristic for mesoporous materials, which indicates the large pore sizes and unique pore size distributions. The capillary condensation of nitrogen takes place at relative pressure of 0.6-0.8. It

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can be conclude that the mesopore channel is uniform. With the HPA amount in the HPAs/SiO2 samples increasing, the beginning of the capillary condensation of nitrogen for the HPAs/SiO2 samples increase to the higher relative pressure. It can be concluded that the pore size become wide. The mesopore size distribution profile calculated by Barrett-Joyner-Halenda(BJH) method

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of HPAs/SiO2 samples display that the HPAs/SiO2 samples are mesoporous, as shown in Fig 1b. It is well known that the presence of inorganic salt sometimes will significantly enhance the the micelle diameter under certain conditions. Then it will further cause the enlarging of the pore

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channel because of the specific interaction between non-ionic surfactant and metal ions. For current work, the specific interaction between non-ionic surfactant P123 and HPA species could

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form and have the significant effect on the SBET and Vtotal. It is very clearly that the HPAs/SiO2 samples display lower SBET and Vtotal value with HPA loadings increasing, as shown in Table 1. The BET surfaces area of the HPAs/SiO2 samples are around 270-310 m2/g and the total pore volume are around 0.65-0.83 cm3/g. Fig 2 displays the X-ray diffraction pattern results of HPAs/SiO2 samples with different loading. As shown in Fig 2a, the characteristics of the hexagonal mesostructure (p6mm symmetry), (110) and (200) reflections, could not be clearly observed for HPAs/SiO2 samples

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ACCEPTED MANUSCRIPT especially for the higher loading. So it could be inferred that the ordering degree for the pore networks has degraded. As shown in Fig 2b, a broad band centered arounds 2θ=25o is associated to the amorphous silica constructing the mesopore channel walls. No crystalline phases related to HPAs are observed for all the HPAs/SiO2 samples with different loading. This result indicates

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that the particles are too small or well dispersed to be detected by XRD. As reported, XRD detectable HPAs crystal phase is developed on silica surface only above 20 wt% loading. So at high weight loading (40 wt%) of HPAs, mainly fine dispersed species are formed. acidity

of

HPAs/SiO2

samples

with

different

loading

was

studied

by

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The

temperature-programmed desorption of ammonium (NH3-TPD) technique and displayed in Fig 3.

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All the HPAs/SiO2 samples with different loading exhibit the ammonia desorption at two temperatures: a low-temperature peak at about 150-300 oC and a high-temperature peak at 400-600 oC, corresponding to the weak and strong acid sites of the samples, respectively. If the HPA loading become high, the amount of desorbed ammonia of the NH4+ adsorbed on the

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Bronsted acid sites also become high (Table 1); at the same time, the gradually weaker interaction between the HPA species and silica surface with the loading increasing also cause the

increases.

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center of Bronsted acid site peak shift from 485 to 520 oC, indicating the strength gradually

FT-IR spectra of HPAs/SiO2 samples with different loading are shown in Fig.4. The bands at

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1080, 985 and 890 cm-1 which are assigned as to the stretching modes of oxygen atom bond to tungsten and phosphorous, W=O, P-O and W-O-W edge, respectively. These results suggest that the HPAs immobilized in silica by sol-gel method keep the Keggin structure. In all catalysts, it should be noted that the heteropolyacid bands placed between 1000 and 1100 cm-1 is masked with the silica band. However, it is observed that some peaks typical of the Keggin structures of HPAs are overlapped or partially overlapped with the peaks of silica matrix framework in the spectrum of the catalysts prepared by sol–gel method (HPAs-in-SO2). There are four IR bands

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ACCEPTED MANUSCRIPT observed for silica matrix. Bands at 1066 and 795 cm−1 could be assigned to asymmetric stretching, symmetric stretching, and bending modes of Si−O−Si linkages. The absorption peak at 968 cm−1 is due to stretching vibration of Si−OH bond in silica. Fig 5 shows the TEM images of HPAs/SiO2. It can be observed the mesostructure with

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one-dimensional channels and some divided small nanosized HPA particles present inside the pore channel. Electron diffraction indicates that these particles are amorphous. The fine HPA nanoparticles appear as dark substances and disperse very well in the pore channel. By the pore

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channel of the host, the HPA particles size could be confined, which could explain why XRD of

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the HPAs/SiO2 samples did not show any crystalline phases related to the heteropolyacids.

3.2 Catalytic activity

Alkylation of phenol with cyclohexene is a typical Bronsted acid-catalyzed reaction. The acid catalytic activity of as-prepared HPA/SiO2 is evaluated by this reaction. Fig 6a shows the

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phenol conversions as a function of time at 230 oC over all the HPA/SiO2 catalysts. The difference in the conversion curves is significantly clear for all the catalyst. 40% loading displays the highest conversion among the tested catalysts: 80% final conversion reaches after 6 h. The

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highest activity over the 40% loading is a result of the most and strongest Bronsted acidity centers over its surface, which will be active for the alkylation of phenol with cyclohexene. The

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final conversion decreases with the loading decreasing. For high loadings the polyoxometalate is mainly in the form of crystallites while for low loadings it is mainly in the form of isolated species. These isolated species can interact with the surface via one, two, or three silanol groups, with the preferential coordination mode being by three silanol groups. As a consequence of low loadings there are few available protons and the catalyst is inactive. When the loading increases, new species appear on the surface: isolated polyoxometalates linked to silica by one or two bonds (and thus keeping some acidity) and microcrystals of bulk polyoxometalate. The latter

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ACCEPTED MANUSCRIPT ones become predominant at very high loadings, and the size of the microcrystals increases with the loading. More and stronger Bronsted acidity centers could appear over the higher loading surface, which will act as the active sites for the alkylation of phenol with cyclohexene. From the slope rate of conversion curves, the reaction rates are calculated. As shown in Fig

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6b, the reaction rate (based on the catalyst mass) increases with the loading increasing because higher loading could provide more active centers to participate the reaction. But if the reaction rate was calculated based on the HPA amount existing in the catalyst, it could be found that 10

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wt % loading display the highest reaction rate. Although lower loading will benefit for the HPA dispersion over the support surface, HPA is mainly in the form of isolated species. As a

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consequence of lower loadings, there are fewer available protons and the catalyst is more inactive. Higher loading will cause the HPA utilization efficiency decreasing, because more HPA exist in bulky form, leading to low HPA dispersion.

Fig 7 shows the phenol conversions as a function of time at different temperature over

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20% loading. Increasing the reaction temperature had favorably influenced the alkylation of phenol with cyclohexene. The conversion was found to increase substantially with increasing temperature, which suggested that the reaction was intrinsically kinetically controlled. At 170 oC, phenol conversion was

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the

only 25%

but

it

reached

to

60%

at

230 oC

under

same reaction conditions. This remarkable influence of temperature on the phenol conversion be

explained

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could

by

Arrhenius

temperature

dependence of

the

reaction

rate.

Higher temperature can provide more energy to overcome the activation energy barrier. As shown in scheme 1, three types of product are detected during the alkylation of phenol

with cyclohexene: O-alkylated product (cyclohexyl phenyl ether, CPE), C-alkylated products (para-cyclohexyl phenol, p-CP and ortho-cyclohexyl phenol, o-CP), and dialkylated product (cyclohexyl cyclohexylphenyl ether, CCPE). The nonzero curves

confirm that

o-CP,

p-CP and

initial

slope of the selectivity

CPE are primary products, while dialkylated 10

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from

these primary products. It is well known that the O- and

C-alkylation reactions are parallel reactions and there is no isomerization of the O-alkylated product (cyclohexyl phenyl ether) into the C-alkylated isomers (o- and p-cyclohexyl phenol) in

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present work. Fig 8 compares the selectivity of alkylation of phenol with cyclohexene as a function of loading at 230 oC (a) and as a function of temperature over 20% loading (b). The O-alkylated product CPE can be detected and its selectivity increases with the loading increasing,

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but decreases as the reaction temperature increase. For the C-alkylated products, increasing the

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reaction temperature and the loading amount will favor the o-CP selectivity. On the contrary, the p-CP selectivity increases with both the loading and the temperature decreasing. The two-point reaction, which produces the dialkylated product CCPE, cannot be ignored in present work and higher temperature and loading favor CCPE. The alkylation of phenol is generally reported to be

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sensitive to the acid-base natures of the catalytic sites. It has been reported that the C-alkylation of phenol preferentially proceeds at weak acidic or strong basic sites, while the O-alkylation is favored at strong acid site[15]. The acid site could induce the O-alkylation through nucleophilic

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attack of adsorbed phenolate by cyclohexyl cation. As the reaction requires formation of

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cyclohexyl cation for electrophilic attack on either the chemisorbed phenol or the free phenol, the Bronsted acidity centers will act as active sites and its strength will be important. In present work, the acidity strength increases with the loading increasing. So the selectivity of O-alkylated product CPE increases with the loading. Only under higher temperature the weaker acidity centers could be active for the alkylation reaction, so the CPE selectivity is sensitive to the temperature and higher temperature favors O-alkylated reaction route. On the other hand, a Lewis acid is a prerequisite for ether intramolecular rearrangement into C-alkylation product to

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ACCEPTED MANUSCRIPT occur. Due to its exculsive Bronsted acidity over HPA catalyst, the ether intramolecular rearrangement could not take place, which also contributes to the O-alkylation route prevailing. Para-alkylated and ortho-alkylated routes take place simultaneously during C-alkylation.

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The para-and ortho-selectivity was examined within the C-alkylated products. Fig. 8 also displays the regioselecitvity dependency on loading and temperature. The o-CP regioselecitvity increases with the loading and high temperature favors o-CP regioselecitvity. Dominated

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para-alkylated regioselecitvity will be obtained due to the shape-selective effect resulting from

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the micropore channel of HZSM-5 or HBEA. But inside the mesopore channel, the o-CP regioselecitvity can be dominated and is very sensitive to loading, regardless of statistic ratio 0.66. The mechanism of the aromatic ring alkylation has been studied in many literatures. The preferential selectivity of the ortho/para-product compared to thermodynamically stable

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meta-product could be due to the fact that the hydroxyl group on the phenol provides ortho/para directing tendency. Phenol approaches alkylation agent cation on the catalyst surface through its OH group pointing towards the mesopore channel surface, which would help the

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ortho/para-position of phenol molecule more susceptible to the electrophilic reaction with

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alkylation agent cation[16]. Though the -OH group on the phenol is ortho/para directing, the selectivity to the ortho/para -product is a function of loading amount in the present investigation. Effect of adsorption configuration of the substrate over the catalyst surface prove very important factor and must be considered for the phenol alkylation regioselecitvity. The vertical adsorption of the phenate anion prevails over the oxide surface, due to the repulsion between highly nucleophilic O2- anions from HPA and the aromatic ring; moreover, mesoporous channel of the catalysts also benefit to this vertical adsorption mode as compared with micro-zeolites.

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in stronger repulsion, leading to more prevailing ortho-alkylated route. On the other hand, a flatwise configuration may favor the substitution at the para-position in the ring to get

high temperature unfavor para-alkylated route.

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para-alkylated product. Higher temperature will disturb the flatwise adsorption configuration, so

It is well been known that the reusability of HPA catalysts is one of the most crucial

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problems, since the continuous dissolution of HPA in polar medium could induce an obvious deactivation. The reusability of catalysts prepared by different methods was also compared in this paper. After catalytic test for the first time, the catalyst was filtered and used for a second time without further treatment. The catalytic reusability is shown in Fig.9. The supported HPA

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catalyst exhibits an obvious deactivation after 6 cycles: the activity dropped by over 50%. Therefore, it was presumed that the supported HPA catalyst had lost a part of acidity because the HPA molecular on the surface of the support was leached during the reaction. In the case of

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silica-included HPA catalyst, the activity loss after 6 cycles was marginal, the activity dropped by only 12%, suggesting that the HPA species were more firmly immobilized on the surface of

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the support. The improvement of reusability of silica-included HPA catalyst was related to the uniform dispersion of HPA on the support and the enhanced interaction between active sites and the support.

4. Conclusions The mesoporous silica-included heteropolyacids materials are prepared and tested for the alkylation of phenol with cyclohexene to produce renewable cyclohexyl phenol and cyclohexyl cyclohexylphenyl ether from biomass resources. Through adjusting the loading 13

ACCEPTED MANUSCRIPT amount, different acidity amount and strength can be obtained. Both the O/C-alkylation selectivity and the regioselectivity are dependent on the loading amount and temperature. The surface property and adsorption configuration of the substrate over the catalyst surface play vital roles to the regioselectivity. The improvement of reusability of silica-included HPA catalyst was

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related to the uniform dispersion of HPA on the support and the enhanced interaction between active sites and the support.

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Acknowledgements

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

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(NNSFC) (U1610108 & 21403273), the Shanxi Scholarship Council of China (2015-122), the Department of Human Resource and Social Security of Shanxi Province (Y6SW9613B1) and the Department

of

Science

and

Technology

of

Shanxi

Province

(201705D211001&

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201605D211006), Shanxi Provincial Natural Science Foundation of China (201601D011024).

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ACCEPTED MANUSCRIPT References [1] C. Amen-Chen, H. Pakdel, C. Roy, Separation of phenols from Eucalyptus wood tar, Biomass Bioenerg, 13 (1997) 25-37. [2] M. Asadullah, N.S. Ab Rasid, S.A.S.A. Kadir, A. Azdarpour, Production and detailed characterization of bio-oil from fast pyrolysis of palm kernel shell, Biomass Bioenerg, 59 (2013) 316-324. Biomass Bioenerg, 27 (2004) 265-275.

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[3] P. Das, T. Sreelatha, A. Ganesh, Bio oil from pyrolysis of cashew nut shell-characterisation and related properties, [4] H.R. Lobo, B.S. Singh, D.V. Pinjari, A.B. Pandit, G.S. Shankarling, Ultrasound-assisted intensification of bio-catalyzed synthesis of mono-N-alkyl aromatic amines, Biochemical Engineering Journal, 70 (2013) 29-34. [5]

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ACCEPTED MANUSCRIPT Table 1 Physicochemical properties of supports and different loading HPAs/SiO2 TPD(NH3)

Vtotalb (cm3/g)

Pore sizec (nm)

(µmol/g)

5%

310

0.83

11

750

10%

300

0.80

12

1100

20%

285

0.72

13

1300

40%

270

0.65

15

1550

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SBETa (m2/g)

Samples

BET surface area calculated from the adsorption branch of the N2 isotherm

b

Total pore volumes calculated from the N2 adsorption at relative pressure of 0.98

c

Pore size calculated from the adsorption branch using the BJH method

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Figure Captions Fig 1. N2 sorption isotherms of HPAs/SiO2. Fig 2. X-ray diffraction patterns of HPAs/SiO2.

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Fig 3. NH3-TPD profiles of HPAs/SiO2. Fig 4. FTIR of HPAs/SiO2. Fig 5. TEM of 40 wt% HPA/SiO2.

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Fig 6. (a) Phenol conversion versus reaction time over HPAs/SiO2; (b) The correlation between reaction rate and loading.

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Fig 7. (a)Phenol conversion versus reaction time at different temperature. Fig 8. (a) Selectivity dependency on loading; (b) Selectivity dependency on temperature. CPE: cyclohexyl phenyl ether, o-CP: o-cyclohexyl phenol, p-CP: p-cyclohexyl phenol, CCPE: cyclohexyl cyclohexylphenyl ether Fig 9. Reusability comparison of 40 wt% HPA/SiO2 and SiO2-supported HPA

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Scheme 1. Reaction routes of alkylation phenol with cyclohexene.

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ACCEPTED MANUSCRIPT Fig 1 600 (a)

Adsorption amount(ml/g)

5% HPA 10% HPA 20% HPA

500 400

40% HPA

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300 200 100

0.2

0.4

0.6

0.8

P/P0

1.0

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0.0

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0

(b)

20

30

EP

10

40

50

60

Pore diameter (nm)

70

80

AC C

0

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dv/dlog(D)

5% HPA 10% HPA 20% HPA 40% HPA

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ACCEPTED MANUSCRIPT Fig 2

(a)

40% HPA

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Intensity a.u.

20% HPA 10% HPA

Pure SiO2

1

2

2θ θο 3

4

5

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0

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5% HPA

(b)

40% HPA

20

30

40

2θ ο

50

10% HPA 5% HPA

Pure SiO2

60

70

80

AC C

10

EP

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Intensity a.u.

20% HPA

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ACCEPTED MANUSCRIPT

200

300 400 500 600 Temperature oC

700

800

AC C

EP

TE D

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100

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TCD signal (a.u.)

Pure silica 5% HPA 10% HPA 20% HPA 40% HPA

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Fig 3

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ACCEPTED MANUSCRIPT Fig 4

Transmittance a.u.

890 985

110

1080

90

70 1000

1500

AC C

EP

TE D

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Wavenumber cm-1

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Pure silica 5% HPA 10% HPA 20% HPA 40% HPA

80

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100

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ACCEPTED MANUSCRIPT

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Fig 5

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ACCEPTED MANUSCRIPT Fig 6

40%

(a)

80

Phenol conversion %

20%

60

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10%

40

0 0

50

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5%

20

100 150 200 250 300 350 400

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Reaction time min.

0.3

0.03

reaction rate (mmol phenol.g-1 HPA s-1)

reaction rate (mmol phenol.g-1 cat s-1)

(b)

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0.2

0.02

EP

0.01

5

10

20

0.1

40

AC C

Loading wt%

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ACCEPTED MANUSCRIPT Fig 7

60 50 40

170oC

30 20 10 0 0

50

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230oC 210oC 190oC

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Phenol conversion %

70

100 150 200 250 300 350 400

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Reaction time min.

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ACCEPTED MANUSCRIPT Fig 8,

100

o-CP regoselectivity

(a)

60

p-CP

40

CPE CCPE

20

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Selectivity %

o-CP

0 10

20

40

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5

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80

Loading wt%

100

(b)

o-CP regoselectivity

80

o-CP

40

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Selectivity %

60

CPE p-CP

0

EP

20

CCPE

AC C

170

190

210

230

o

Temperature C

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ACCEPTED MANUSCRIPT Fig 9

∆=12%

80 Silica included HPA

40

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60

∆=52%

Supported HPA

20 0 2

3

4 Cycles

5

6

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EP

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1

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Phenol conversion %

100

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ACCEPTED MANUSCRIPT

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Scheme 1

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ACCEPTED MANUSCRIPT Highlights 1. The preparation of mesoporous silica-included heteropolyacids materials 2. Production of renewable cyclohexyl phenol and cyclohexyl cyclohexylphenyl ether

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from biomass resources

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3. The improvement of reusability of silica-included HPA catalyst