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tert‑butyl alcohol on ionic liquid-immobilized SBA-15 with different pore sizes
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Alkylation of phenol/tert–butyl alcohol on ionic liquid-immobilized SBA-15 with different pore sizes Tingshun Jiang∗, Minglan Fang, Yingying Li, Qian Zhao, Liming Dai School of Chemistry and Chemical Engineering, Jiangsu University, Zhenjiang 212013, Jiangsu, China
a r t i c l e
i n f o
Article history: Received 23 April 2017 Revised 12 September 2017 Accepted 19 September 2017 Available online xxx Keyword: Mesoporous SBA-15 molecular sieve -SO3 H immobilized ionic liquids Immobilized SBA-15 Alkylation Phenol
a b s t r a c t Mesoporous SBA-15 molecular sieves with different pore sizes were obtained using n-hexane as a micelle expander and NH4 NO3 as structure adjuvant and used as support materials. The -SO3 H immobilized environmentally Brӧnsted acidic ionic liquids were synthesized. Supported ionic liquids acid catalysts (1IL@SBA-15 (5, 8, 12 nm)) were prepared by impregnation method and their physicochemical properties were characterized by FT-IR, TG-DSC, N2 physical adsorption, XRD, SEM and TEM. The catalytic activities of the synthesized acid catalysts were investigated by the alkylation of phenol with tert–butyl alcohol (TBA). The effect of amount of IL supported, weight hour space velocity (WHSV), reactant mole ratio, reaction temperature, pore size of SBA-15 on the conversion of phenol and selectivity to products were investigated. Compared to 1-IL@SBA-15 (5 nm) and 1-IL@SBA-15 (12 nm), 1-IL@SBA-15 (8 nm) exhibited the best phenol conversion up to 85.5% at 80 °C, suggesting that with the same content ionic liquid of catalysts, SBA-15 (8 nm) as support have remarkable catalytic activity and selectivity. © 2017 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.
1. Introduction The alkylated phenols are generally prepared using the alkylation reaction of phenol with tert–butyl alcohol (TBA), mainly 2t–butyl phenol (2-TBP), 4-t–butyl phenol (4-TBP), 2,4-di-t–butyl phenol (2,4-DTBP) and 2,6-di-t–butyl phenol (2,6-DTBP), which were widely used in synthetic resins, dyes, pesticide intermediates, gasoline additives, ultraviolet absorbent, gasoline additives and the thermal stabilizers [1–6] and so on. The catalysts used for the tert–butylation of phenol include Lewis acids like BF3 and FeCl3 [7], Brӧnsted acids like H2 SO4 , HF, H3 PO4 , and HClO4 [8], molecular sieves [6], mesoporous materials [9,10], zeolites [2,3], cationexchange resin [11], near critical as well as super critical water [12], heteropoly acids [10], solid sulfanilic acids [13]. Inorganic liquid acid catalysts are easy to cause equipment corrosion and environmental pollution, and solid acid catalysts have the disadvantages of deactivation by coking. Although cation-exchange resins exhibited a good performance, poor thermal stability and easy to scale are also major problem [14]. During the last few decades, ionic liquids (ILs) have been widely used, for the reasons that it is an environmentally friendly green solvent and catalyst. An immobilized alkane sulfonic acid group ILs with strong Brӧnsted acid has attracted much attention [15], and
∗
Corresponding author. E-mail address: [email protected] (T. Jiang).
exhibited high catalytic activity in numerous applications [16–19]. For example, Gui et al. have first reported that a series of immobilized ionic liquids can catalyze alkylation of phenol with TBA with high conversion and selectivity to 2, 4-DTBP at suitable reactant ratio [20]. Nevertheless, the expensive and large dosages of ILs restrict their applications. Moreover, it is difficult to separate and recover from the reaction [21]. In order to overcome these problems, a useful method could be used to support immobilized ILs on high surface area materials [22–25]. By this means, homogeneous catalytic reactions of ILs transform into the heterogeneous catalytic reactions. It is beneficial to achieve high catalyst efficiency by reducing the consumption of ILs and recycling it [26–28]. Mesoporous SiO2 materials such as SBA-15 represent suitable support for various catalysts [29–32]. Previously, the -SO3 H immobilized ILs onto SBA-15 has been investigated by testing the catalytic activity with the esterification of ethylene glycol and acetic acid. It could be found that structure-activity relationships were often studied by bulk and surface structures under catalytic reaction conditions [33], while few other characteristics such as internal pore size were taken into account. Hence, varying the pore size of the support material was investigated to determine structure-activity relationships in this work. In the present work, SBA-15 with different pore sizes and -SO3 H immobilized Brӧnsted acidic ionic liquids were synthesized. The IL supported 1-IL@SBA-15 (5, 8, 12 nm) acid catalysts were prepared by the impregnation method and their catalytic activities were evaluated by the alkylation of phenol with
https://doi.org/10.1016/j.jtice.2017.09.029 1876-1070/© 2017 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.
Please cite this article as: T. Jiang et al., Alkylation of phenol/tert–butyl alcohol on ionic liquid-immobilized SBA-15 with different pore sizes, Journal of the Taiwan Institute of Chemical Engineers (2017), https://doi.org/10.1016/j.jtice.2017.09.029
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Transmittance/(%)
A
SBA-15(5nm) 1-IL@SBA-15(5nm)
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2000 3000 Wavenumber(cm-1)
1-IL@SBA-15(5nm)
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4000
1-IL@SBA-15(12nm)
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2000 3000 Wavenumber(cm-1)
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Fig. 1. FT-IR spectra of IL, SBA-15 (5 nm), 1-IL@SBA-15 (5 nm), 1-IL@SBA-15 (8 nm) and 1-IL@SBA-15 (12 nm).
tert–butyl alcohol. We discussed in detail the effect of amount of IL supported, WHSV, reactant mole ratio, reaction temperature and pore size of SBA-15 on the phenol conversion and product selectivity. 2. Experimental 2.1. Materials Tetraethyl orthosilicate (TEOS, 99%) and poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (Pluronic P123) were used as sources for silicon and the structure-directing agent, respectively. Moreover, 1, 3-propane sultone, N-Methylimidazole, concentrated sulfuric acid (H2 SO4 ), toluene, methanol and diethyl ether were also used in preparation of ionic liquids. All the reagents were of analytical grade and were purchased from Shanghai Chemical Reagent Co., Ltd. 2.2. Synthesis of the -SO3 H immobilized ionic liquids [34] 1, 3-propane sultone (12.21 g, 0.1 mol) was fully dispersed in 50 ml dried toluene and N-methylimidazole (8.209 g, 0.1 mol) was added dropwise in ice bath. Then, the mixture was stirred for 4 h at 30 °C. After the reaction completed, the reaction mixture was filtered and washed three times with diethyl ether, and dried under high vacuum to produce 1-propyl sulfonic group-3-methyl imidazole. Equimolar concentrated sulfuric acid was added dropwise to 1-propyl sulfonic group-3-methyl imidazole (20.4 g, 0.1 mol) and stirred for 2 h at 80 °C to form the ionic liquid. Then, it was washed respectively with toluene and ethyl ether, and the result was obtained under vacuum to produce1-propyl sulfonic group-3methyl imidazole hydrogen sulfate ([Ps-mim]HSO4 ), which was denoted as IL in this work. 2.3. Preparation of SBA-15with different pore sizes Mesoporous SBA-15 with a pore size of ∼5 nm was prepared according to the Ref. [35]. 4.0 g of P123 and 20 ml of 37 wt.% concentrated hydrochloric acid were dissolved in 120 ml of deionized water until the solution became clear. Then, 9 ml of tetraethyl orthosilicate was added to the solution. After stirring for 24 h at 35 °C, the mixture was aged under static conditions and constant pressure at 100 °C for 48 h. After cooling to ambient temperature, the solid product was filtered, washed with distilled water, dried overnight in an oven. The template agent was removed by calcination at 550 °C for 5 h. The resultant material was denoted as SBA15 (5 nm).
Mesoporous SBA-15 with pore size of ∼8 nm and ∼12 nm was prepared according to the Ref. [36]. 4.0 g of P123 and 20 ml of 37 wt.% concentrated hydrochloric acid were dissolved in 120 ml of deionized water until the solution became clear. Then, 0.0968 g NH4 NO3 was added into the clear solution. 1 ml and 4 ml of nhexane was respectively added to the solution and stirred for another 2 h before adding 9 ml of tetraethylorthosilicate. After being stirring for 24 h at 20 °C, the mixture was aged under static conditions and constant pressure for 48 h at 100 °C. After cooling to ambient temperature, the solid product was filtered, washed with distilled water, dried overnight in an oven. The template agent was removed by calcination at 550 °C for 5 h. The resultant materials were denoted as SBA-15 (8 nm) and SBA-15 (12 nm), correspondingly.
2.4. Supporting of the -SO3 H immobilized ionic liquids on SBA-15with different pore sizes 0.8, 1 or 1.2 g of [Ps-mim]HSO4 (denoted as IL) was dispersed in 5 ml of anhydrous methanol to become clear, which was added dropwise to 1 g of SBA-15 (X nm) (X stands for pore sizes, X = 5, 8 and 12) in 50 ml of anhydrous methanol, stirred at room temperature for 3 h. Catalysts of n-IL@ SBA-15 (X nm) (n represents the quality of IL loading per gram SBA-15) were prepared by evaporating the methanol solvent. Then, the catalysts were dried in vacuum at 50 °C.
2.5. Characterization FT-IR spectra was recorded on a Nexus FT-IR 470 spectrometer made by Nicolet Corporation using KBr pellets in the frequency range of 40 0 0–40 0/cm. Thermal gravimetric analysis (TGA) was conducted on a STA 449C simultaneous DSC-TGA from ambient temperature to 800 °C at a heating rate of 10 °C/min in air. The N2 adsorption–desorption isotherms were measured at −196 °C with a NOVA20 0 0e analytical system made by Quantachrome Corporation (USA). The data were analyzed by the BJH and BET methods. Powder XRD spectra were performed with a Rigaku D/MAX 2500PC instrument with Cu Kα radiation (λ = 0.15418 nm). The tube voltage was 40 kV, while the current was 50 mA. XRD patterns were recorded with scan step of 0.02° from 0.5° to 5° (2θ ) at a speed of 1°/min. Transmission electron microscopy (TEM) microphotographs were carried out on a Philips TEMCNAI-12 with an acceleration voltage of 120 kV. Scanning electron microscopy (SEM) morphologies of samples were observed on a Philips XL-30ESEM.
Please cite this article as: T. Jiang et al., Alkylation of phenol/tert–butyl alcohol on ionic liquid-immobilized SBA-15 with different pore sizes, Journal of the Taiwan Institute of Chemical Engineers (2017), https://doi.org/10.1016/j.jtice.2017.09.029
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DSC/(mW/mg) 1.5
TG/% 100
1-IL@SBA-15 (5nm)
A 90
14.8%
80
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60
60
50
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50
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TG/%
0 29.5%
-2
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-4
DSC/(mW/mg) 2
TG/%
100 C
1.2-IL@SBA-15(5nm)
D
90
22.3%
0
80
1-IL@SBA-15(8nm) 22.8%
0
80
70
36.6%
70
42.3%
60
60
-2
50
-2
50
40 30
21.8%
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35.9%
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B
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TG/%
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3
40 -4
100 200 300 400 500 600 700
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-4
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Temperature/°C
DSC/(mW/mg) 2
TG/%
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E
21.4%
1-IL@SBA-15(12nm)
80
0
70
37.3%
60
-2
50 40 30
100 200 300 400 500 600 700
-4
Temperature/°C Fig. 2. TG-DSC curves of 1-IL@SBA-15 (5 nm), 0.8-IL@SBA-15 (5 nm), 1.2-IL@SBA-15 (5 nm), 1-IL@SBA-15 (8 nm) and 1-IL@SBA-15 (12 nm) samples.
2.6. Catalytic experiment The alkylation reaction of phenol with tert–butyl alcohol was carried out in an automated stainless steel fixed-bed continuous reactor. Before the reaction, the catalysts were dried in vacuum at 50 °C overnight. In each run, 0.5 g of catalyst with particle sizes ranging from 240 to 245 μm was placed in a reactor tube. The reactant mixture of phenol and tert–butyl alcohol with different mole ratios was delivered to the reactor using a piston-type pump (WO109-1B) at a flowing rate of 50 mL/min using nitrogen as the carrier gas, and it goes through the premixer. Then, the preheated
reactant mixture with a flowing nitrogen entered into the catalyst bed to process alkylation reaction. The product stream coming out of the reactor is collected at every 2 h interval. The products were analyzed by SP-20 0 0 gas chromatograph fitted with a SE-54 capillary column coupled with FID. 3. Results and discussion 3.1. FT-IR analysis The FT-IR spectra of IL, SBA-15 (5 nm) and 1-IL@SBA-15 (5 nm) samples were shown in Fig. 1A to conform the supporting of IL
Please cite this article as: T. Jiang et al., Alkylation of phenol/tert–butyl alcohol on ionic liquid-immobilized SBA-15 with different pore sizes, Journal of the Taiwan Institute of Chemical Engineers (2017), https://doi.org/10.1016/j.jtice.2017.09.029
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SBA-15(12nm)
200 100 0 0.0
1-IL@SBA-15(12nm)
0.2
0.4 0.6 0.8 Relative Pressure(p/p0)
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Fig. 3. N2 adsorption–desorption isotherms and pore size distribution curves of various samples.
Table 1 Structure properties for various samples. Sample
SBET (m2 /g)
Dpore a (nm)
Vpore a (cm2 /g)
SBA-15 (5 nm) SBA-15 (8 nm) SBA-15 (12 nm) 0.8-IL@SBA-15 (5 nm) 1-IL@SBA-15 (5 nm) 1.2-IL@SBA-15 (5 nm) 1-IL@SBA-15 (8 nm) 1-IL@SBA-15 (12 nm)
567 650 503 96 78 54 95 57
5.4 7.9 12.1 6.8 7.2 8.0 8.2 12.3
0.77 1.07 0.85 0.19 0.16 0.11 0.21 0.21
a Total pore size and pore volume of various samples were calculated from BJH adsorption branch.
on the SBA-15(5 nm). As illustrated in Fig. 1A, SBA-15 (5 nm) displayed a strong adsorption peak at 1058/cm associated with antisymmetric stretching vibration of the silica framework. The band approximately at 800/cm is aroused by the vibration of Si–O–Si bond. The small band at about 970/cm is assigned to immobilized (Si–OH) bond and the SiO–H groups are shown by the very broad IR absorption band in the 30 0 0–370 0/cm region [37]. For the IL sample, the absorption bands at 3153/cm and 3113/cm were attributed to the stretching vibration of the C–H bond on imidazole, and the characteristic peak at 1575/cm belonged to the adsorption peak of the imidazole ring. The adsorption peaks at 1060/cm and 1172/cm were associated with the vibration of SO3 H and HSO4 − . The bands at 2960/cm, 2858/cm and 1459/cm were aroused by stretching and bending vibration of C–H bond on the methyl. Similar characteristic peaks of IL can also be observed on the 1-IL@SBA-15 (5 nm), indicating that the IL has been loaded on the SBA-15 (5 nm). Due to SBA-15 (5 nm), SBA-15 (8 nm) and SBA-15 (12 nm) with similar chemical structure, all the above
mentioned can be derived from the FT-IR spectra of 1-IL@SBA-15 (8 nm) and 1-IL@SBA-15 (12 nm), which was shown in Fig. 1B. All of the above show that the IL has been supported on SBA-15 with different pore sizes successfully. 3.2. TG-DSC analysis The TG-DSC analysis was carried out to investigate the thermal stability of 1-IL@SBA-15 (5 nm), 0.8-IL@SBA-15 (5 nm), 1.2-IL@SBA15 (5 nm), 1-IL@SBA-15 (8 nm) and 1-IL@SBA-15 (12 nm). As shown in Fig. 2A, the thermogravimetric curve of 1-IL@SBA-15 (5 nm) showed that an initial mass loss of 14.8% from 25 °C to 265 °C because of the evaporation of physical adsorbed water, and the dehydration of silanol groups. A significant weight loss of 35.9% can be detected in the temperature range of 265 °C–600 °C mainly because the organic structure of supports and the residual organic template decomposed. Also, the same tendency were observed in 0.8-IL@SBA-15 (5 nm), 1.2-IL@SBA-15 (5 nm), 1-IL@SBA-15 (8 nm) and 1-IL@SBA-15 (12 nm), showed in the Fig. 2B, C, D and E, respectively. And the second weight losses were 29.5%, 42.3%, 34.7% and 37.3%. It was noted that the amount of second weight loss increased with the increase of addition of ionic liquid and the enlargement of pore diameter also increased that amount. The residual silica weight of the sample at 600 °C was used as reference for determining the total organic loading. 3.3. Nitrogen adsorption–desorption analysis The N2 adsorption–desorption isotherms and pore size distribution curves of SBA-15 with different pore sizes and IL@SBA15 samples are presented in Fig. 3A–C. All the materials showed typical type IV isotherms, indicative of mesoporous material with
Please cite this article as: T. Jiang et al., Alkylation of phenol/tert–butyl alcohol on ionic liquid-immobilized SBA-15 with different pore sizes, Journal of the Taiwan Institute of Chemical Engineers (2017), https://doi.org/10.1016/j.jtice.2017.09.029
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B
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Intensity (a. u.)
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C
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Intensity(a. u.)
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Intensity (a. u.)
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1.2-IL@SBA-15(5nm) 1-IL@SBA-15(5nm)
SBA-15(12nm) 0.8-IL@SBA-15(5nm)
1-IL@SBA-15(12nm)
2
4 6 8 2 Theta(degrees)
2
10
4 6 8 2 Theta(degrees)
10
Fig. 4. XRD patterns of various samples.
clear H1-type adsorption–desorption hysteresis loops. The hysteresis range was nearly parallel for SBA-15 (5 nm) and SBA-15 (8 nm) indicating regular shaped pores. N2 isotherms for SBA-15 (12 nm) showed a slight broadening of the hysteresis loop. The narrow H1type hysteresis loop of SBA-15 with different pore sizes is maintained after the supporting of IL. Fig. 3 also showed the pore size distribution derived from BJH analysis resulting in three different pore sizes of ∼5 nm, ∼8 nm and ∼12 nm. The corresponding textural properties including the specific surface areas and pore sizes calculated by the BET and BJH methods are summarized in Table 1. As it can be seen from the SBA-15 (5 nm), there is a gradual reduction of the BET surface area and pore volume with the increase of IL content, which suggested at least a partial deposition of IL on the pore walls. On the other hand, with the increasing of the IL content loaded on SBA-15 (5 nm), the pore size increased from 6.8 to 8.0 nm, suggesting that the IL layer over the mesoporous channels, but the external deposition of the IL over the mesostructured silica particles that would block the entrance of pores [38]. Further, it is noted that in terms of the same loadings of IL, the pore size of 1-IL@SBA-15 (8 nm) and 1-IL@SBA-15 (12 nm) have a slightly increasing compared with the pure silicaous SBA-15 (5 nm) and SBA-15 (8 nm) supports. These differences indicated that the appropriate increase of carrier pore size can reduce the blockage of deposition. 3.4. XRD analysis The XRD patterns of SBA-15 with different pore sizes, 1-IL@SBA15 and SBA-15 (5 nm) with different IL loading content samples are presented in Fig. 4A–D. It could be found that all samples in the range of 2θ = 0.5–3° have three clear diffraction peaks attributed to the (1 0 0), (1 1 0) and (2 0 0) characteristic diffraction peaks of
SBA-15. This result indicated that whenever the pore size of SBA15 was enlarged or the IL was introduced, the resulting IL@SBA15 samples had mesoporous structure, but the peak intensities declined greatly. This may be due to the occupation of ionic liquid in the pore structure [39]. Also, it was noted that diffraction peak position of the SBA-15 (8 nm) and SBA-15 (12 nm) supports has a shift to lower 2θ . This shift is associated to the presence of large pore size on these samples. The IL impregnated on SBA-15 with different pore sizes for various catalytic materials provokes a relevant decrease in the intensity of the diffraction peaks, demonstrating the deterioration of the mesoporous ordering. Besides these, we can also note from Fig. 4D that the mesoporous ordering of the resulting IL@SBA-15 (5 nm) sample decreased with the increase of IL content introduced in SBA-15 (5 nm) sample, but the three samples still maintained the mesoporous framework. 3.5. TEM analysis The TEM images of SBA-15 (5 nm), SBA-15 (8 nm), SBA-15 (12 nm) and 1-IL@SBA-15 (5 nm) are shown in Fig. 5A–F. As can be seen from the images, all the samples exhibited well-defined ordered 2D-hexagonal mesoporous structure after enlarging the pore size of SBA-15 or loading the IL of which, Fig. 5A, B, C and D are viewed along perpendicular directions, Fig. 5E and F are viewed along parallel directions. Moreover, we found from Fig. 5A that the pore size of SBA-15 is about 5.29 nm, which is nearly in agreement with the N2 adsorption–desorption diameter analysis. In the image of SBA-15 (8 nm) and SBA-15 (12 nm), the pore size is increased to 8.43 nm and 11.96 nm with the increase of pore-expanding agent n-hexane, respectively. Moreover, the SBA-15 (5 nm) supporting the IL material show typical rod-shaped particles of mesoporous materials in Fig. 5D. That suggests the IL loaded onto the SBA-15 (5 nm)
Please cite this article as: T. Jiang et al., Alkylation of phenol/tert–butyl alcohol on ionic liquid-immobilized SBA-15 with different pore sizes, Journal of the Taiwan Institute of Chemical Engineers (2017), https://doi.org/10.1016/j.jtice.2017.09.029
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Fig. 5. TEM images of various samples (A) SBA-15 (5 nm); (B) SBA-15 (8 nm); (C) SBA-15 (12 nm); (D) 1-IL@SBA-15 (5 nm); (E) SBA-15 (5 nm); (F) 1-IL@SBA-15 (5 nm). (A), (B), (C) and (D) viewed along perpendicular directions, (E) and (F) viewed along parallel directions. The insert in Fig. 5A showed the selected area electron diffraction (SAED) of SBA-15.
Please cite this article as: T. Jiang et al., Alkylation of phenol/tert–butyl alcohol on ionic liquid-immobilized SBA-15 with different pore sizes, Journal of the Taiwan Institute of Chemical Engineers (2017), https://doi.org/10.1016/j.jtice.2017.09.029
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Table 2 Alkylation of phenol with tert-butyl alcohol in different amount of IL catalysts. Conversion (%) Selectivity (%) 2-TBP 4-TBP 2,4-DTBP 2,6-DTBP 0.8-IL@SBA-15 (5 nm) 60.5 1-IL@SBA-15 (5 nm) 76.3 1.2-IL@SBA-15 (5 nm) 77.4
36.7 32.1 30.8
17.2 8.7 5.0
41.6 50.3 51.7
4.5 8.9 12.5
Reaction conditions: 0.5 g catalyst, n( tert -butanol) /n(phenol) = 2:1, WHSV = 2/h, time = 2 h, reaction temperature = 80 °C.
without destroying the pore channel of mesoporous materials. Furthermore, as shown in the insert in Fig. 5A, the SAED pattern clearly suggested the SBA-15 material belonged to the amorphous phase, the result agreed with the Ref. [40,41]. Fig. 6 presents the SEM images of several samples including the SBA-15 (5 nm), SBA15 (8 nm), SBA-15 (12 nm) and1-IL@SBA-15 (5 nm). These images show some short rods with uniform size aggregated together. Also, Fig. 6D showed that introduction of IL in IL@SBA-15 (5 nm) catalyst less influenced the morphology of the parent SBA-15 support. 3.6. Catalytic activity 3.6.1. Effect of amount of IL supported onto SBA-15 (5 nm) on phenol conversion and product selectivity The alkylation of phenol with tert–butyl alcohol was carried out with HYPERLINK "mailto: 0.8-IL@SBA-15 (5 nm), 1-IL@SBA-15 (5 nm) and HYPERLINK "mailto: 1.2-IL@SBA-15 (5 nm). The obtained results are listed in Table 2. It is observed from Table 2 that the selectivity to 2-TBP and 2, 4-DTBP was high as compared to 4-TBP and 2, 6-DTBP. On the other hand, with increase of IL loading amount onto SBA-15 (5 nm), the conversion of phenol and the selectivity for 2,4-DTBP and 2,6-DTBP also increased. At the same
80 60
Phenol 2TBP 4TBP 2,4DTBP 2,6DTBP
80 60
40
40
20
20
0
1.0
1.5 2.0 2.5 ntert-butanol : nphenol
3.0
Product selectivity/%
Catalysts
Phenol conversion/(mol%)
Fig. 6. SEM images of various samples (A) SBA-15 (5 nm); (B) SBA-15 (8 nm); (C) SBA-15 (12 nm); (D) 1-IL@SBA-15 (5 nm).
0
Fig. 7. Effect of mole ratio of tert-butyl alcohol with phenol on phenol conversion and product selectivity over 1-IL@SBA-15 (5 nm) catalyst (Reaction condition: WHSV = 2/h, time = 2 h, temperature = 80 °C).
time, the selectivity for 2-TBP and 4-TBP decreased. Furthermore, when the amount of IL increased from 0.8 g to 1 g, phenol conversion increased from 60.5% to 76.3%, while the amount of IL increased from 1 g to 1.2 g, phenol conversion slightly increased. Hence, the 1-IL@SBA-15 (5 nm) catalyst was chosen as the detail study. 3.6.2. Effect of mole ratio of tert–butyl alcohol to phenol on phenol conversion and product selectivity The effect of different mole ratios of tert–butyl alcohol with phenol on phenol conversion and product selectivity over 1IL@SBA-15 (5 nm) catalyst at 80 °C was shown in Fig. 7. It is seen from the figure that the phenol conversion and 2, 4-DTBP, 2, 6DTBP selectivity increased as the mole ratio of tert–butyl alcohol
Please cite this article as: T. Jiang et al., Alkylation of phenol/tert–butyl alcohol on ionic liquid-immobilized SBA-15 with different pore sizes, Journal of the Taiwan Institute of Chemical Engineers (2017), https://doi.org/10.1016/j.jtice.2017.09.029
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T. Jiang et al. / Journal of the Taiwan Institute of Chemical Engineers 000 (2017) 1–10 Table 3 Recyclability of three kinds of pore size catalysts. Catalysts
Experimental run
Conversion (%)
Selectivity (%) 2-TBP
4-TBP
2,4-DTBP
2,6-DTBP
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1 2 3 4 5 1 2 3 4 5 1 2 3 4 5
76.3 74.0 69.7 59.2 51.6 85.5 84.2 81.3 76.7 65.4 67.2 60.3 55.8 49.5 42.2
32.1 33.1 35.5 40.7 44.5 20.4 21.7 24.6 31.6 36.9 38.4 41.0 42.9 47.7 54.3
8.7 10.3 12.8 16.6 19.3 3.9 5.0 7.5 9.5 12.3 14.0 17.3 18.1 20.4 22.2
50.3 49.2 45.7 37.6 32.8 59.0 58.3 55.1 49.9 44.1 42.0 37.5 35.4 30.1 22.7
8.9 7.4 6.0 5.1 3.4 16.7 15.0 12.8 9.0 6.7 5.6 4.2 3.6 1.8 0.8
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0
Fig. 8. Effect of different WHSVs on phenol conversion and product selectivity over 1-IL@SBA-15 (5 nm) catalyst (reaction condition: ntert -butanol /nphenol = 2:1, time = 2 h, temperature = 80 °C).
with phenol increased from 1 to 2 and the highest phenol conversion was achieved at the mole ratio of 2:1 of tert–butyl alcohol with phenol. Further, the phenol conversion, and 2, 4-DTBP, 2, 6DTBP selectivity decreased with increase in the mole ratio of tert– butyl alcohol with phenol from 2 to 3. This trend in phenol conversion and product selectivity indicated that increased amount of tert–butyl alcohol led to more single-alkylation of phenol and tert– butyl alcohol, further reacted into 2,4-DTBP and 2,6-DTBP, which is favorable for the conversion of phenol and the selectivity for 2,4DTBP and 2,6-DTBP. Whereas the excessive use of tert–butyl alcohol can cause the formation of byproducts by intermolecular dehydration. Hence, the optimum TBA to phenol mole ratio is 2:1 at 80 °C. 3.6.3. Effect of weight hour space velocity on phenol conversion and product selectivity The effect of weight hour space velocity (WHSV) on phenol conversion and product selectivity over 1-IL@SBA-15 (5 nm) catalyst was investigated and the results are summarized in Fig. 8. It is evident that the phenol conversion decreased from 76.3% to 46.8% with increase of WHSV from 2/h to 5/h. This significant change may be attributed to that the contact time of the reactants with catalyst is shortened with the increase of WHSV, resulting in the reducing of phenol conversion. Furthermore, it is observed that with the increase of WHSV from 2/h to 5/h, the selectivity to 2TBP and 4-TBP has a remarkable increase. On the contrary, the selectivity to 2, 4-DTBP and 2, 6-DTBP decreased with the increase
of WHSV from 2/h to 5/h. This is probably due to the faster reaction rate of single-alkylation and the relatively lower reaction rate of multi-alkylation. 3.6.4. Effect of reaction temperature and pore size of support on phenol conversion and product selectivity A series of reactions were conducted in the temperature range of 60–100 °C using the IL supported on carriers with different pore sizes as catalysts. The conversion of phenol decreased significantly beyond 100 °C since the dealkylation reaction became prominent as reported by earlier researchers [42]. However, at low temperature, the selectivity of dialkylate product was suppressed [43] and the extent of reactions was restricted by mass transfer limitations [44]. So the reaction temperature range from 60 °C to 100 °C was studied in this experiment. Fig. 9A summarizes the results of 1IL@SBA-15 (5 nm) catalyst obtained for the alkylation reaction conducted in the temperature range of 60–100 °C up to 2 h of reaction time. With increase in temperature from 60 °C to 80 °C, the conversion of phenol increased from 57.7% to 76.3%. Beyond 80 °C, there is a decrease in phenol conversion. The selectivity to 2,4-DTBP and 2,6-DTBP is highest at the temperature of 80 °C, accompanied with the selectivity to 2-TBP and 4-TBP is the lowest. All of this may be owing to that when the alkylation reaction controlled by kinetics, heating is an advantage to the reaction at the relatively low temperature range. The alkylation reaction is reversible exothermic reaction. The reaction temperature continues to increase, the phenol conversion and selectivity of 2, 4-DTBP decrease. This may be attributed to the control of thermodynamics and the dealkylation is dominant at higher temperature. On the other hand, it is notably found that the pore diameter of the support plays an important role influencing the catalytic activity. Fig. 9 shows a comparison of the conversion of phenol and the selectivity of products at the temperature range of 60–100 °C. The coverage of theoretical IL was similar for all samples. However, a significant difference between all 1-IL@SBA-15 (5, 8, 12 nm) was the curvature of the surface in the pores. The pore structure of mesoporous SBA-15 (5, 8, 12 nm) corresponded to that of hollow cylinders. Thus, the curvature of the walls of these cylinders decreased with larger pore size. Further, arrangement of the IL along the inner surface of pores with different pore sizes led to an increasing distance between the IL at larger pore size. The increased effective distance of the IL theoretically resulted in a lower phenol conversion and products selectivity [45]. However, the experimental results showed that in contrast to the samples of 1-IL@SBA15 (5 nm) and 1-IL@SBA-15 (12 nm), 1-IL@SBA-15 (8 nm) was not
Please cite this article as: T. Jiang et al., Alkylation of phenol/tert–butyl alcohol on ionic liquid-immobilized SBA-15 with different pore sizes, Journal of the Taiwan Institute of Chemical Engineers (2017), https://doi.org/10.1016/j.jtice.2017.09.029
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Fig. 9. Effect of different reaction temperatures and pore sizes of supports on phenol conversion and product selectivity over different catalysts (reaction condition: ntert -butanol /nphenol = 2:1, WHSV = 2/h, time = 2 h). (A) 1-IL@SBA-15(5 nm); (B) 1-IL@SBA-15(8 nm); (C) 1-IL@SBA-15(12 nm).
a significant influence on the product distribution, showing the highest phenol conversion and 2, 4-DTBP selectivity. It can be attributed that the extremely narrow pore of SBA-15 (5 nm) hinders the diffusion of the reactants.
-SO3 H immobilized ionic liquids to choose SBA-15(8 nm) as suitable supports to the application of phenol alkylation.
3.7. Recyclability of catalyst
Financial support from Project supported by the National Natural Science Foundation of China (51572115) and Project supported by the Graduate Science Research Innovation Program Foundation of the Jiangsu Higher Education Institution of China (KYLX15_1040) are gratefully acknowledged.
The recyclability of different catalysts was listed in Table 3. As shown in Table 3, for 1-IL@SBA-15 (5 nm) and 1-IL@SBA15 (12 nm), we found that the phenol conversion has obviously changed just repeated two or three times. This may be attributed to the following: one reason is that the unreacted reactants or products were diffused into the narrow mesoporous material channels. The other one is due to the part of supported IL that could be lost after several repetitions in relatively large pore size. 4. Conclusions The -SO3 H immobilized ionic liquids supported on three different pore sizes of well-ordered SBA-15 (5, 8, 12 nm) was successfully synthesized by impregnation method. The alkylation of phenol with tert–butyl alcohol was carried out over several IL@SBA-15 (5, 8, 12 nm) acid catalysts. The results showed that 1- IL@SBA-15 (8 nm) exhibited good catalytic activity for the alkylation of phenol with tert–butyl alcohol with the highest phenol conversion of 85.5% and 2,4-DTBP selectivity of 60.0% at the temperature of 80 °C and alcohol to phenol molar ratio of 2:1. It could be conclusion that the -SO3 H functionalized ionic liquids supported onto the SBA-15 materials with small pores are easy to block the pore and hinder the diffusion of the reactants resulting in decreasing of phenol conversion and product selectivity. So, it is essential for
Acknowledgments
References [1] Sakthivel A, Badamali SK, Selvam P. Para-selective tert-butylation of phenol over mesoporous H-AlMCM-41. Microporous Mesoporous Mater 20 0 0;39:457–63. [2] Krishnan AV, Ojha K, Pradhan NC. Alkylation of phenol with tertiary butyl alcohol over zeolites. Org Process Res Dev 2002;6:132–7. [3] Zhang K, Zhang HB, Xu GH. Alkylation of phenol with tert-butyl alcohol catalyzed by large pore zeolite. Appl Catal A 2001;207:183–90. [4] Changler K, Deng F, Dillow AK. Alkylation reaction in near-critical water in the absence of acid catalysts. Ind Eng Chem Res 1997;36:5175–9. [5] Sato T, Sekiguchi G, Adschiri T, Arai K. Non-catalytic and selective alkylation of phenol with propan-2-ol in supercritical water. Chem Commun 2001;17:1566–7. [6] Sumbramanian S, Mitra A, Satyanarayana CVV, Chakrabarty DK. Para-selective butylation of phenol over silicoaluminophosphate molecular sieve SAPO-11 catalyst. Appl Catal A 1997;159:229–40. [7] Shinde AB, Shrigadi NB, Samant SD. Tert-butylation of phenols using tert-butyl alcohol in the presence of FeCl3 -modified montmorillonite K10. Appl Catal A 2004;276:5–8. [8] Carltion AA. Alkylation of phenol with tert-butyl alcohol in the presence of perchloric acid. J Org Chem 1948;13:120–2. [9] Sakthivel A, Dapurkar SE, Gupta NM, Kulshreshtha SK, Selvam P. The influence of aluminium sources on the acidic behavior as well as on the catalytic activity of mesoporous H-AlMCM-41 molecular sieves. Microporous Mesoporous Mater 2003;65:177–87.
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[10] Bhatt N, Sharma P, Patel A, Selvam P. Supported 12-tungstophosphoricacid: an efficient and selective solid acid catalyst for tert-butylation of phenol and cresols. Catal Commun 2008;9:1545–50. [11] Rajadhyaksha RA, Chaudhari DD. Alkylation of phenol and pyrocatechol by isobutyl alcohol using superacid catalysts. Ind Eng Chem Res 1987;26:1276–80. [12] Chandler K, Liotta CL, Eckert CA, Schiraldi D. Tuning alkylation reactions with temperature in near-critical water. AIChE J 1998;44:2080–7. [13] Adam F, Hello KM, Ali TH. Solvent free liquid-phase alkylation of phenol over solid sulfanilic acid catalyst. Appl Catal A 2011;399:42–9. [14] Harmer MA, Sun Q. Solid acid catalysis using ion-exchange resins. Appl Catal A 2001;221:45–62. [15] Cole AC, Jensen JL, Ntai I, Tran KT, Weave KJ, Forbes DC, et al. Novel Bronsted acidic ionic liquids and their use as dual solvent-catalysts. J Am Chem Soc 2002;124:5962–6. [16] Forbes DC, Weaver KJ. Bronsted acidic ionic liquids: the dependence on water of the Fischer esterification of acetic acid and ethanol. J Mol Catal A 2004;214:129–32. [17] Gu Y, Shi F, Deng Y. Esterification of aliphatic acids with olefin promoted by Bronsted acidic ionic liquids. J Mol Catal A 2004;212:71–5. [18] Gui J, Cong X, Liu D, Zhang X, Hu Z, Sun Z. Novel Bronsted acidic ionic liquid as efficient and reusable catalyst system for esterification. Catal Commun 2004;5:473–7. [19] Elavarasan P, Kondamudi K, Upadhyayula S. Kinetics of phenol alkylation with tert-butyl alcohol using sulfonic acid functional ionic liquid catalysts. Chem Eng J 2011;166:340–7. [20] Gui JZ, Ban HY, Cong XH, Zhang XT, Hu ZD, Sun ZL. Selective alkylation of phenol with tert-butyl alcohol catalyzed by Bronsted acidic imidazolium salts. J Mol Catal A 2005;225:27–31. [21] Valkenberg MH, Castro CD, Holderich WF. Immobilization of ionic liquids on solid supports. Green Chem 2002;4:88–93. [22] Amarasekara AS, Owereh OS. Synthesis of a sulfonic acid functionalized acidic ionic liquid modified silica catalyst and applications in the hydrolysis of cellulose. Catal Commun 2010;11:1072–5. [23] Liu FJ, Wang L, Sun Q, Zhu LF, Meng XJ, Xiao FS. Transesterification catalyzed by ionic liquids on superhydrophobic mesoporous polymers: heterogeneous catalysts that are faster than homogeneous catalysts. J Am Chem Soc 2012;134:16948–50. [24] Ding W, Zhu W, Xiong J, Yang L, Wei A, Zhang M, et al. Novel heterogeneous iron-based redox ionic liquid supported on SBA-15 for deep oxidative desulfurization of fuels. Chem Eng J 2015;266:213–21. [25] Wang B, Zhang J, Zou X, Dong H, Yao P. Selective oxidation of styrene to 1,2-epoxyethylbenzene by hydrogen peroxide over heterogeneous phosphomolybdic acid supported on ionic liquid modified MCM-41. Chem Eng J 2015;260:172–7. [26] Rostamnia S, Gholipour B, Hosseini HG. Metal-and halogen-free hydrogensulfata ionic liquid/SBA-15 as catalyst in clean oxidation of aromatic and aliphatic organic sulfides with aqueous hydrogen peroxide. Process Saf Environ 2016;100:74–9. [27] Rostamnia S, Hassankhani A, Hossieni HS. Brӧnsted acidic hydrogensulfata ionic liquid immobilized SBA-15:[MPIm][HSO4 ]@SBA-15 as an environmentally friendly, metal- and halogen-free recyclable catalyst for Knoevenagel-Michael– cyclization processes. J Mol Catal A 2014;395:463–9. [28] Rostamnia S, Xin HC. Simultaneous application of ultrasonic irradiation and immobilized ionic liquid onto the SBA-15 nanoreactor (US/[MPIm]CI@SBA-15): a rubust, recyclable, and useful combined catalytic system for selective and waste-free Kabachnik Fields reaction. J Mol Liquids 2014;195:30–4.
[29] Doustkah E, Rostamnia S. Single site supported N-sulfonic acid and N-sulfamate onto SBA-15 for green and sustainable oxidation of sulfides. Mater Chem Phys 2016;177:229–35. [30] Rostamnia S, Lamei K, Pourhassan F. Generation of uniform and small particle size of palladium onto the SH-decorated SBA-15 pore-walls: SBA-15/(SH)XPd-NPY as a recoverable nanocatalyst for Suzuki-Miyaura coupling reaction in air and water. Rsc Adv 2014;5:1033. [31] Rostamnia S, Doustkhah E. Covalently bonded zwitterionic sulfamic acid onto the SBA-15 (SBA-15/PrEn-NHSO3 H) reveals good Brӧnsted acidity behavior and catalytic activity in N-formylation of amines. J Mol Catal A 2016;411:317–24. [32] Rostamnia S, Rahmani T, Xin HC. Pd(PrSO3 )@SBA-15 and Pd-NPs(PrSO)@SBA-15 hybrid material: a highly active, reusable, and selective interface catalyst for C-X activations in air and water. J Ind Eng Chem 2015;32:218–24. [33] Yang JB, Zhou LH, Guo XT, Li L, Zhang P, Hong RY, et al. Study on the esterification for ethylene glycol diacetate using supported ionic liquids as catalyst: catalysts preparation, characterization, and reaction kinetics, process. Chem Eng J 2015;280:147–57. [34] Liu S, Xie C, Yu S, Liu F. Dimerization of rosin using Brӧnsted-Lewis acidic ionic liquid as catalyst. Catal Commun 2008;9:2030–4. [35] Zhao DY, Feng JL, Huo QS, Melosh N, Fredrickson GH, Chmelka BF, Stucky GD. Triblock copolymer syntheses of mesoporous silica with periodic 50 to 300 angstrom pores. Science 1998;279:548–52. [36] Wang S, Huang Y, Li J. A novel method for synthesis of large-pore mesoporous molecular sieve SBA-15. J S Cent Univ Natl 2010;29:5–8. [37] Dindar MH, Yaftian MR, Hajihasani M, Rostamnia S. Refinement of contaminated water by Cr(Ⅵ), As(Ⅴ) and Hg(Ⅱ) using N-donor ligands arranged on SBA-15 platform; batch and fixed-bed column methods. J Taiwan Inst Chem E 2016;67:325–37. [38] Martinez F, Morales G, Martin A, Griekan R. Perfluorinated Nafion-modified SBA-15 materials for catalytic acylation of anisole. Appl Catal A 2008;347:169–78. [39] Zhou B, Yu DH, Xia JJ, Tang SS, Liu WM, Huang H. Immobilization of porcine pancreatic lipase onto ionic liquid modified mesoporous silica SBA-15. Biochem Eng J 2010;53:150–3. [40] Miah AT, Bharadwaj SK, Saikia P. Surfactant free synthesis of gold nanoparticles within meso-channels of non-functionalized SBA-15 for its promising catalytic activity. Powder Technol 2017;315:147–56. [41] Araújo MM, Silva LKR, Sczancoski JC, Orlandi MO, Longo E, Santos AGD, et al. Anatase TiO2 nanocrystals anchored at inside of SBA-15 mesopores and their optical behavior. Appl Surf Sci 2016;389:1137–47. [42] Yadav GD, Doshi NS. Alkylation of phenol with methyl-tert-butyl ether and tert-butanol over solid acids: efficacies of clay-based catalysts. Appl Catal A 2002;236:129–47. [43] Jong JI. The alkylation of phenol with isobutene. Recueil 1964;83:469–76. [44] Gu Y, Shi F, Deng Y. SO3 H-functionalized ionic liquid as efficient, green and reusable acidic catalyst system for oligomerization of olefins. Catal Commun 2003;4:597–601. [45] Zubrzycki R, Ressler T. Influence of pore size of SBA-15 on activity and selectivity of H3 [PMo12 O40 ] supported on tailored SBA-15. Microporous Mesoporous Mater 2015;214:8–14.
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Alkylation of phenol/tert–butyl alcohol on ionic liquid-immobilized SBA-15 with different pore sizes Tingshun Jiang∗, Minglan Fang, Yingying Li, Qian Zhao, Liming Dai School of Chemistry and Chemical Engineering, Jiangsu University, Zhenjiang 212013, Jiangsu, China
a r t i c l e
i n f o
Article history: Received 23 April 2017 Revised 12 September 2017 Accepted 19 September 2017 Available online xxx Keyword: Mesoporous SBA-15 molecular sieve -SO3 H immobilized ionic liquids Immobilized SBA-15 Alkylation Phenol
a b s t r a c t Mesoporous SBA-15 molecular sieves with different pore sizes were obtained using n-hexane as a micelle expander and NH4 NO3 as structure adjuvant and used as support materials. The -SO3 H immobilized environmentally Brӧnsted acidic ionic liquids were synthesized. Supported ionic liquids acid catalysts (1IL@SBA-15 (5, 8, 12 nm)) were prepared by impregnation method and their physicochemical properties were characterized by FT-IR, TG-DSC, N2 physical adsorption, XRD, SEM and TEM. The catalytic activities of the synthesized acid catalysts were investigated by the alkylation of phenol with tert–butyl alcohol (TBA). The effect of amount of IL supported, weight hour space velocity (WHSV), reactant mole ratio, reaction temperature, pore size of SBA-15 on the conversion of phenol and selectivity to products were investigated. Compared to 1-IL@SBA-15 (5 nm) and 1-IL@SBA-15 (12 nm), 1-IL@SBA-15 (8 nm) exhibited the best phenol conversion up to 85.5% at 80 °C, suggesting that with the same content ionic liquid of catalysts, SBA-15 (8 nm) as support have remarkable catalytic activity and selectivity. © 2017 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.
1. Introduction The alkylated phenols are generally prepared using the alkylation reaction of phenol with tert–butyl alcohol (TBA), mainly 2t–butyl phenol (2-TBP), 4-t–butyl phenol (4-TBP), 2,4-di-t–butyl phenol (2,4-DTBP) and 2,6-di-t–butyl phenol (2,6-DTBP), which were widely used in synthetic resins, dyes, pesticide intermediates, gasoline additives, ultraviolet absorbent, gasoline additives and the thermal stabilizers [1–6] and so on. The catalysts used for the tert–butylation of phenol include Lewis acids like BF3 and FeCl3 [7], Brӧnsted acids like H2 SO4 , HF, H3 PO4 , and HClO4 [8], molecular sieves [6], mesoporous materials [9,10], zeolites [2,3], cationexchange resin [11], near critical as well as super critical water [12], heteropoly acids [10], solid sulfanilic acids [13]. Inorganic liquid acid catalysts are easy to cause equipment corrosion and environmental pollution, and solid acid catalysts have the disadvantages of deactivation by coking. Although cation-exchange resins exhibited a good performance, poor thermal stability and easy to scale are also major problem [14]. During the last few decades, ionic liquids (ILs) have been widely used, for the reasons that it is an environmentally friendly green solvent and catalyst. An immobilized alkane sulfonic acid group ILs with strong Brӧnsted acid has attracted much attention [15], and
∗
Corresponding author. E-mail address: [email protected] (T. Jiang).
exhibited high catalytic activity in numerous applications [16–19]. For example, Gui et al. have first reported that a series of immobilized ionic liquids can catalyze alkylation of phenol with TBA with high conversion and selectivity to 2, 4-DTBP at suitable reactant ratio [20]. Nevertheless, the expensive and large dosages of ILs restrict their applications. Moreover, it is difficult to separate and recover from the reaction [21]. In order to overcome these problems, a useful method could be used to support immobilized ILs on high surface area materials [22–25]. By this means, homogeneous catalytic reactions of ILs transform into the heterogeneous catalytic reactions. It is beneficial to achieve high catalyst efficiency by reducing the consumption of ILs and recycling it [26–28]. Mesoporous SiO2 materials such as SBA-15 represent suitable support for various catalysts [29–32]. Previously, the -SO3 H immobilized ILs onto SBA-15 has been investigated by testing the catalytic activity with the esterification of ethylene glycol and acetic acid. It could be found that structure-activity relationships were often studied by bulk and surface structures under catalytic reaction conditions [33], while few other characteristics such as internal pore size were taken into account. Hence, varying the pore size of the support material was investigated to determine structure-activity relationships in this work. In the present work, SBA-15 with different pore sizes and -SO3 H immobilized Brӧnsted acidic ionic liquids were synthesized. The IL supported 1-IL@SBA-15 (5, 8, 12 nm) acid catalysts were prepared by the impregnation method and their catalytic activities were evaluated by the alkylation of phenol with
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Please cite this article as: T. Jiang et al., Alkylation of phenol/tert–butyl alcohol on ionic liquid-immobilized SBA-15 with different pore sizes, Journal of the Taiwan Institute of Chemical Engineers (2017), https://doi.org/10.1016/j.jtice.2017.09.029
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Fig. 1. FT-IR spectra of IL, SBA-15 (5 nm), 1-IL@SBA-15 (5 nm), 1-IL@SBA-15 (8 nm) and 1-IL@SBA-15 (12 nm).
tert–butyl alcohol. We discussed in detail the effect of amount of IL supported, WHSV, reactant mole ratio, reaction temperature and pore size of SBA-15 on the phenol conversion and product selectivity. 2. Experimental 2.1. Materials Tetraethyl orthosilicate (TEOS, 99%) and poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (Pluronic P123) were used as sources for silicon and the structure-directing agent, respectively. Moreover, 1, 3-propane sultone, N-Methylimidazole, concentrated sulfuric acid (H2 SO4 ), toluene, methanol and diethyl ether were also used in preparation of ionic liquids. All the reagents were of analytical grade and were purchased from Shanghai Chemical Reagent Co., Ltd. 2.2. Synthesis of the -SO3 H immobilized ionic liquids [34] 1, 3-propane sultone (12.21 g, 0.1 mol) was fully dispersed in 50 ml dried toluene and N-methylimidazole (8.209 g, 0.1 mol) was added dropwise in ice bath. Then, the mixture was stirred for 4 h at 30 °C. After the reaction completed, the reaction mixture was filtered and washed three times with diethyl ether, and dried under high vacuum to produce 1-propyl sulfonic group-3-methyl imidazole. Equimolar concentrated sulfuric acid was added dropwise to 1-propyl sulfonic group-3-methyl imidazole (20.4 g, 0.1 mol) and stirred for 2 h at 80 °C to form the ionic liquid. Then, it was washed respectively with toluene and ethyl ether, and the result was obtained under vacuum to produce1-propyl sulfonic group-3methyl imidazole hydrogen sulfate ([Ps-mim]HSO4 ), which was denoted as IL in this work. 2.3. Preparation of SBA-15with different pore sizes Mesoporous SBA-15 with a pore size of ∼5 nm was prepared according to the Ref. [35]. 4.0 g of P123 and 20 ml of 37 wt.% concentrated hydrochloric acid were dissolved in 120 ml of deionized water until the solution became clear. Then, 9 ml of tetraethyl orthosilicate was added to the solution. After stirring for 24 h at 35 °C, the mixture was aged under static conditions and constant pressure at 100 °C for 48 h. After cooling to ambient temperature, the solid product was filtered, washed with distilled water, dried overnight in an oven. The template agent was removed by calcination at 550 °C for 5 h. The resultant material was denoted as SBA15 (5 nm).
Mesoporous SBA-15 with pore size of ∼8 nm and ∼12 nm was prepared according to the Ref. [36]. 4.0 g of P123 and 20 ml of 37 wt.% concentrated hydrochloric acid were dissolved in 120 ml of deionized water until the solution became clear. Then, 0.0968 g NH4 NO3 was added into the clear solution. 1 ml and 4 ml of nhexane was respectively added to the solution and stirred for another 2 h before adding 9 ml of tetraethylorthosilicate. After being stirring for 24 h at 20 °C, the mixture was aged under static conditions and constant pressure for 48 h at 100 °C. After cooling to ambient temperature, the solid product was filtered, washed with distilled water, dried overnight in an oven. The template agent was removed by calcination at 550 °C for 5 h. The resultant materials were denoted as SBA-15 (8 nm) and SBA-15 (12 nm), correspondingly.
2.4. Supporting of the -SO3 H immobilized ionic liquids on SBA-15with different pore sizes 0.8, 1 or 1.2 g of [Ps-mim]HSO4 (denoted as IL) was dispersed in 5 ml of anhydrous methanol to become clear, which was added dropwise to 1 g of SBA-15 (X nm) (X stands for pore sizes, X = 5, 8 and 12) in 50 ml of anhydrous methanol, stirred at room temperature for 3 h. Catalysts of n-IL@ SBA-15 (X nm) (n represents the quality of IL loading per gram SBA-15) were prepared by evaporating the methanol solvent. Then, the catalysts were dried in vacuum at 50 °C.
2.5. Characterization FT-IR spectra was recorded on a Nexus FT-IR 470 spectrometer made by Nicolet Corporation using KBr pellets in the frequency range of 40 0 0–40 0/cm. Thermal gravimetric analysis (TGA) was conducted on a STA 449C simultaneous DSC-TGA from ambient temperature to 800 °C at a heating rate of 10 °C/min in air. The N2 adsorption–desorption isotherms were measured at −196 °C with a NOVA20 0 0e analytical system made by Quantachrome Corporation (USA). The data were analyzed by the BJH and BET methods. Powder XRD spectra were performed with a Rigaku D/MAX 2500PC instrument with Cu Kα radiation (λ = 0.15418 nm). The tube voltage was 40 kV, while the current was 50 mA. XRD patterns were recorded with scan step of 0.02° from 0.5° to 5° (2θ ) at a speed of 1°/min. Transmission electron microscopy (TEM) microphotographs were carried out on a Philips TEMCNAI-12 with an acceleration voltage of 120 kV. Scanning electron microscopy (SEM) morphologies of samples were observed on a Philips XL-30ESEM.
Please cite this article as: T. Jiang et al., Alkylation of phenol/tert–butyl alcohol on ionic liquid-immobilized SBA-15 with different pore sizes, Journal of the Taiwan Institute of Chemical Engineers (2017), https://doi.org/10.1016/j.jtice.2017.09.029
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DSC/(mW/mg) 1.5
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1-IL@SBA-15 (5nm)
A 90
14.8%
80
100
60
60
50
-0.5
50
DSC/(mW/mg) 2
100 90
40
100 200 300 400 500 600 700 Temperature/oC
TG/%
0 29.5%
-2
100 200 300 400 500 600 700 Temperature/°C
-4
DSC/(mW/mg) 2
TG/%
100 C
1.2-IL@SBA-15(5nm)
D
90
22.3%
0
80
1-IL@SBA-15(8nm) 22.8%
0
80
70
36.6%
70
42.3%
60
60
-2
50
-2
50
40 30
21.8%
70
35.9%
0.0
40
0.8-IL@SBA-15(5nm)
B
80
0.5 70
DSC/(mW/mg) 2
TG/%
90
1.0
3
40 -4
100 200 300 400 500 600 700
100 200 300 400 500 600 700
-4
Temperature/°C
Temperature/°C
DSC/(mW/mg) 2
TG/%
100 90
E
21.4%
1-IL@SBA-15(12nm)
80
0
70
37.3%
60
-2
50 40 30
100 200 300 400 500 600 700
-4
Temperature/°C Fig. 2. TG-DSC curves of 1-IL@SBA-15 (5 nm), 0.8-IL@SBA-15 (5 nm), 1.2-IL@SBA-15 (5 nm), 1-IL@SBA-15 (8 nm) and 1-IL@SBA-15 (12 nm) samples.
2.6. Catalytic experiment The alkylation reaction of phenol with tert–butyl alcohol was carried out in an automated stainless steel fixed-bed continuous reactor. Before the reaction, the catalysts were dried in vacuum at 50 °C overnight. In each run, 0.5 g of catalyst with particle sizes ranging from 240 to 245 μm was placed in a reactor tube. The reactant mixture of phenol and tert–butyl alcohol with different mole ratios was delivered to the reactor using a piston-type pump (WO109-1B) at a flowing rate of 50 mL/min using nitrogen as the carrier gas, and it goes through the premixer. Then, the preheated
reactant mixture with a flowing nitrogen entered into the catalyst bed to process alkylation reaction. The product stream coming out of the reactor is collected at every 2 h interval. The products were analyzed by SP-20 0 0 gas chromatograph fitted with a SE-54 capillary column coupled with FID. 3. Results and discussion 3.1. FT-IR analysis The FT-IR spectra of IL, SBA-15 (5 nm) and 1-IL@SBA-15 (5 nm) samples were shown in Fig. 1A to conform the supporting of IL
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800
200
0
10 20 Pore diameter(nm)
30
SBA-15(5nm)
100
1-IL@SBA-15(5nm)
0.2
0.4 0.6 0.8 Relative Pressure(p/p0)
Volume absorbed (cm3/g)
0 0.0
600 500
SBA-15(8nm)
0
300
20
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SBA-15(8nm)
200 1-IL@SBA-15(8nm)
100 0 0.0
1.0
10
Pore Diameter (nm)
400
0.2
0.4 0.6 0.8 Relative Pressure(p/p0)
1.0
C
600 500
B
700 dV/dD
Volume absorbed (cm3/g)
300
SBA-15(Z5nm)
dV/dD
400
A dV/dD
Volume absorbed (cm3/g)
500
SBA-15(12nm)
400 0
10 20 Pore Diameter (nm)
300
30
SBA-15(12nm)
200 100 0 0.0
1-IL@SBA-15(12nm)
0.2
0.4 0.6 0.8 Relative Pressure(p/p0)
1.0
Fig. 3. N2 adsorption–desorption isotherms and pore size distribution curves of various samples.
Table 1 Structure properties for various samples. Sample
SBET (m2 /g)
Dpore a (nm)
Vpore a (cm2 /g)
SBA-15 (5 nm) SBA-15 (8 nm) SBA-15 (12 nm) 0.8-IL@SBA-15 (5 nm) 1-IL@SBA-15 (5 nm) 1.2-IL@SBA-15 (5 nm) 1-IL@SBA-15 (8 nm) 1-IL@SBA-15 (12 nm)
567 650 503 96 78 54 95 57
5.4 7.9 12.1 6.8 7.2 8.0 8.2 12.3
0.77 1.07 0.85 0.19 0.16 0.11 0.21 0.21
a Total pore size and pore volume of various samples were calculated from BJH adsorption branch.
on the SBA-15(5 nm). As illustrated in Fig. 1A, SBA-15 (5 nm) displayed a strong adsorption peak at 1058/cm associated with antisymmetric stretching vibration of the silica framework. The band approximately at 800/cm is aroused by the vibration of Si–O–Si bond. The small band at about 970/cm is assigned to immobilized (Si–OH) bond and the SiO–H groups are shown by the very broad IR absorption band in the 30 0 0–370 0/cm region [37]. For the IL sample, the absorption bands at 3153/cm and 3113/cm were attributed to the stretching vibration of the C–H bond on imidazole, and the characteristic peak at 1575/cm belonged to the adsorption peak of the imidazole ring. The adsorption peaks at 1060/cm and 1172/cm were associated with the vibration of SO3 H and HSO4 − . The bands at 2960/cm, 2858/cm and 1459/cm were aroused by stretching and bending vibration of C–H bond on the methyl. Similar characteristic peaks of IL can also be observed on the 1-IL@SBA-15 (5 nm), indicating that the IL has been loaded on the SBA-15 (5 nm). Due to SBA-15 (5 nm), SBA-15 (8 nm) and SBA-15 (12 nm) with similar chemical structure, all the above
mentioned can be derived from the FT-IR spectra of 1-IL@SBA-15 (8 nm) and 1-IL@SBA-15 (12 nm), which was shown in Fig. 1B. All of the above show that the IL has been supported on SBA-15 with different pore sizes successfully. 3.2. TG-DSC analysis The TG-DSC analysis was carried out to investigate the thermal stability of 1-IL@SBA-15 (5 nm), 0.8-IL@SBA-15 (5 nm), 1.2-IL@SBA15 (5 nm), 1-IL@SBA-15 (8 nm) and 1-IL@SBA-15 (12 nm). As shown in Fig. 2A, the thermogravimetric curve of 1-IL@SBA-15 (5 nm) showed that an initial mass loss of 14.8% from 25 °C to 265 °C because of the evaporation of physical adsorbed water, and the dehydration of silanol groups. A significant weight loss of 35.9% can be detected in the temperature range of 265 °C–600 °C mainly because the organic structure of supports and the residual organic template decomposed. Also, the same tendency were observed in 0.8-IL@SBA-15 (5 nm), 1.2-IL@SBA-15 (5 nm), 1-IL@SBA-15 (8 nm) and 1-IL@SBA-15 (12 nm), showed in the Fig. 2B, C, D and E, respectively. And the second weight losses were 29.5%, 42.3%, 34.7% and 37.3%. It was noted that the amount of second weight loss increased with the increase of addition of ionic liquid and the enlargement of pore diameter also increased that amount. The residual silica weight of the sample at 600 °C was used as reference for determining the total organic loading. 3.3. Nitrogen adsorption–desorption analysis The N2 adsorption–desorption isotherms and pore size distribution curves of SBA-15 with different pore sizes and IL@SBA15 samples are presented in Fig. 3A–C. All the materials showed typical type IV isotherms, indicative of mesoporous material with
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B
A
SBA-15(5nm)
110 200
Intensity (a. u.)
100
110 200
Intensity (a. u.)
100
SBA-15(8nm)
1-IL@SBA-15(5nm)
2
1-IL@SBA-15(8nm)
4 6 8 2 Theta(degrees)
2
10
4 6 8 2 Theta(degrees)
10
D
C
200
Intensity(a. u.)
110 200
110
100
100
Intensity (a. u.)
5
1.2-IL@SBA-15(5nm) 1-IL@SBA-15(5nm)
SBA-15(12nm) 0.8-IL@SBA-15(5nm)
1-IL@SBA-15(12nm)
2
4 6 8 2 Theta(degrees)
2
10
4 6 8 2 Theta(degrees)
10
Fig. 4. XRD patterns of various samples.
clear H1-type adsorption–desorption hysteresis loops. The hysteresis range was nearly parallel for SBA-15 (5 nm) and SBA-15 (8 nm) indicating regular shaped pores. N2 isotherms for SBA-15 (12 nm) showed a slight broadening of the hysteresis loop. The narrow H1type hysteresis loop of SBA-15 with different pore sizes is maintained after the supporting of IL. Fig. 3 also showed the pore size distribution derived from BJH analysis resulting in three different pore sizes of ∼5 nm, ∼8 nm and ∼12 nm. The corresponding textural properties including the specific surface areas and pore sizes calculated by the BET and BJH methods are summarized in Table 1. As it can be seen from the SBA-15 (5 nm), there is a gradual reduction of the BET surface area and pore volume with the increase of IL content, which suggested at least a partial deposition of IL on the pore walls. On the other hand, with the increasing of the IL content loaded on SBA-15 (5 nm), the pore size increased from 6.8 to 8.0 nm, suggesting that the IL layer over the mesoporous channels, but the external deposition of the IL over the mesostructured silica particles that would block the entrance of pores [38]. Further, it is noted that in terms of the same loadings of IL, the pore size of 1-IL@SBA-15 (8 nm) and 1-IL@SBA-15 (12 nm) have a slightly increasing compared with the pure silicaous SBA-15 (5 nm) and SBA-15 (8 nm) supports. These differences indicated that the appropriate increase of carrier pore size can reduce the blockage of deposition. 3.4. XRD analysis The XRD patterns of SBA-15 with different pore sizes, 1-IL@SBA15 and SBA-15 (5 nm) with different IL loading content samples are presented in Fig. 4A–D. It could be found that all samples in the range of 2θ = 0.5–3° have three clear diffraction peaks attributed to the (1 0 0), (1 1 0) and (2 0 0) characteristic diffraction peaks of
SBA-15. This result indicated that whenever the pore size of SBA15 was enlarged or the IL was introduced, the resulting IL@SBA15 samples had mesoporous structure, but the peak intensities declined greatly. This may be due to the occupation of ionic liquid in the pore structure [39]. Also, it was noted that diffraction peak position of the SBA-15 (8 nm) and SBA-15 (12 nm) supports has a shift to lower 2θ . This shift is associated to the presence of large pore size on these samples. The IL impregnated on SBA-15 with different pore sizes for various catalytic materials provokes a relevant decrease in the intensity of the diffraction peaks, demonstrating the deterioration of the mesoporous ordering. Besides these, we can also note from Fig. 4D that the mesoporous ordering of the resulting IL@SBA-15 (5 nm) sample decreased with the increase of IL content introduced in SBA-15 (5 nm) sample, but the three samples still maintained the mesoporous framework. 3.5. TEM analysis The TEM images of SBA-15 (5 nm), SBA-15 (8 nm), SBA-15 (12 nm) and 1-IL@SBA-15 (5 nm) are shown in Fig. 5A–F. As can be seen from the images, all the samples exhibited well-defined ordered 2D-hexagonal mesoporous structure after enlarging the pore size of SBA-15 or loading the IL of which, Fig. 5A, B, C and D are viewed along perpendicular directions, Fig. 5E and F are viewed along parallel directions. Moreover, we found from Fig. 5A that the pore size of SBA-15 is about 5.29 nm, which is nearly in agreement with the N2 adsorption–desorption diameter analysis. In the image of SBA-15 (8 nm) and SBA-15 (12 nm), the pore size is increased to 8.43 nm and 11.96 nm with the increase of pore-expanding agent n-hexane, respectively. Moreover, the SBA-15 (5 nm) supporting the IL material show typical rod-shaped particles of mesoporous materials in Fig. 5D. That suggests the IL loaded onto the SBA-15 (5 nm)
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Fig. 5. TEM images of various samples (A) SBA-15 (5 nm); (B) SBA-15 (8 nm); (C) SBA-15 (12 nm); (D) 1-IL@SBA-15 (5 nm); (E) SBA-15 (5 nm); (F) 1-IL@SBA-15 (5 nm). (A), (B), (C) and (D) viewed along perpendicular directions, (E) and (F) viewed along parallel directions. The insert in Fig. 5A showed the selected area electron diffraction (SAED) of SBA-15.
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Table 2 Alkylation of phenol with tert-butyl alcohol in different amount of IL catalysts. Conversion (%) Selectivity (%) 2-TBP 4-TBP 2,4-DTBP 2,6-DTBP 0.8-IL@SBA-15 (5 nm) 60.5 1-IL@SBA-15 (5 nm) 76.3 1.2-IL@SBA-15 (5 nm) 77.4
36.7 32.1 30.8
17.2 8.7 5.0
41.6 50.3 51.7
4.5 8.9 12.5
Reaction conditions: 0.5 g catalyst, n( tert -butanol) /n(phenol) = 2:1, WHSV = 2/h, time = 2 h, reaction temperature = 80 °C.
without destroying the pore channel of mesoporous materials. Furthermore, as shown in the insert in Fig. 5A, the SAED pattern clearly suggested the SBA-15 material belonged to the amorphous phase, the result agreed with the Ref. [40,41]. Fig. 6 presents the SEM images of several samples including the SBA-15 (5 nm), SBA15 (8 nm), SBA-15 (12 nm) and1-IL@SBA-15 (5 nm). These images show some short rods with uniform size aggregated together. Also, Fig. 6D showed that introduction of IL in IL@SBA-15 (5 nm) catalyst less influenced the morphology of the parent SBA-15 support. 3.6. Catalytic activity 3.6.1. Effect of amount of IL supported onto SBA-15 (5 nm) on phenol conversion and product selectivity The alkylation of phenol with tert–butyl alcohol was carried out with HYPERLINK "mailto: 0.8-IL@SBA-15 (5 nm), 1-IL@SBA-15 (5 nm) and HYPERLINK "mailto: 1.2-IL@SBA-15 (5 nm). The obtained results are listed in Table 2. It is observed from Table 2 that the selectivity to 2-TBP and 2, 4-DTBP was high as compared to 4-TBP and 2, 6-DTBP. On the other hand, with increase of IL loading amount onto SBA-15 (5 nm), the conversion of phenol and the selectivity for 2,4-DTBP and 2,6-DTBP also increased. At the same
80 60
Phenol 2TBP 4TBP 2,4DTBP 2,6DTBP
80 60
40
40
20
20
0
1.0
1.5 2.0 2.5 ntert-butanol : nphenol
3.0
Product selectivity/%
Catalysts
Phenol conversion/(mol%)
Fig. 6. SEM images of various samples (A) SBA-15 (5 nm); (B) SBA-15 (8 nm); (C) SBA-15 (12 nm); (D) 1-IL@SBA-15 (5 nm).
0
Fig. 7. Effect of mole ratio of tert-butyl alcohol with phenol on phenol conversion and product selectivity over 1-IL@SBA-15 (5 nm) catalyst (Reaction condition: WHSV = 2/h, time = 2 h, temperature = 80 °C).
time, the selectivity for 2-TBP and 4-TBP decreased. Furthermore, when the amount of IL increased from 0.8 g to 1 g, phenol conversion increased from 60.5% to 76.3%, while the amount of IL increased from 1 g to 1.2 g, phenol conversion slightly increased. Hence, the 1-IL@SBA-15 (5 nm) catalyst was chosen as the detail study. 3.6.2. Effect of mole ratio of tert–butyl alcohol to phenol on phenol conversion and product selectivity The effect of different mole ratios of tert–butyl alcohol with phenol on phenol conversion and product selectivity over 1IL@SBA-15 (5 nm) catalyst at 80 °C was shown in Fig. 7. It is seen from the figure that the phenol conversion and 2, 4-DTBP, 2, 6DTBP selectivity increased as the mole ratio of tert–butyl alcohol
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T. Jiang et al. / Journal of the Taiwan Institute of Chemical Engineers 000 (2017) 1–10 Table 3 Recyclability of three kinds of pore size catalysts. Catalysts
Experimental run
Conversion (%)
Selectivity (%) 2-TBP
4-TBP
2,4-DTBP
2,6-DTBP
1-IL@SBA-15(5 nm)
1 2 3 4 5 1 2 3 4 5 1 2 3 4 5
76.3 74.0 69.7 59.2 51.6 85.5 84.2 81.3 76.7 65.4 67.2 60.3 55.8 49.5 42.2
32.1 33.1 35.5 40.7 44.5 20.4 21.7 24.6 31.6 36.9 38.4 41.0 42.9 47.7 54.3
8.7 10.3 12.8 16.6 19.3 3.9 5.0 7.5 9.5 12.3 14.0 17.3 18.1 20.4 22.2
50.3 49.2 45.7 37.6 32.8 59.0 58.3 55.1 49.9 44.1 42.0 37.5 35.4 30.1 22.7
8.9 7.4 6.0 5.1 3.4 16.7 15.0 12.8 9.0 6.7 5.6 4.2 3.6 1.8 0.8
1-IL@SBA-15(8 nm)
1-IL@SBA-15(12 nm)
Phenol 2TBP 4TBP 2,4DTBP 2,6DTBP
80 60
80 60
40
40
20
20
0
2
3 4 WHSV(h-1)
5
Product selectivity/%
Phenol conversion/(mol%)
Reaction condition: 0.5 g catalyst, n( tert -butanol) /n(phenol) = 2:1, WHSV = 2/h, time = 2 h, reaction temperature = 80 °C.
0
Fig. 8. Effect of different WHSVs on phenol conversion and product selectivity over 1-IL@SBA-15 (5 nm) catalyst (reaction condition: ntert -butanol /nphenol = 2:1, time = 2 h, temperature = 80 °C).
with phenol increased from 1 to 2 and the highest phenol conversion was achieved at the mole ratio of 2:1 of tert–butyl alcohol with phenol. Further, the phenol conversion, and 2, 4-DTBP, 2, 6DTBP selectivity decreased with increase in the mole ratio of tert– butyl alcohol with phenol from 2 to 3. This trend in phenol conversion and product selectivity indicated that increased amount of tert–butyl alcohol led to more single-alkylation of phenol and tert– butyl alcohol, further reacted into 2,4-DTBP and 2,6-DTBP, which is favorable for the conversion of phenol and the selectivity for 2,4DTBP and 2,6-DTBP. Whereas the excessive use of tert–butyl alcohol can cause the formation of byproducts by intermolecular dehydration. Hence, the optimum TBA to phenol mole ratio is 2:1 at 80 °C. 3.6.3. Effect of weight hour space velocity on phenol conversion and product selectivity The effect of weight hour space velocity (WHSV) on phenol conversion and product selectivity over 1-IL@SBA-15 (5 nm) catalyst was investigated and the results are summarized in Fig. 8. It is evident that the phenol conversion decreased from 76.3% to 46.8% with increase of WHSV from 2/h to 5/h. This significant change may be attributed to that the contact time of the reactants with catalyst is shortened with the increase of WHSV, resulting in the reducing of phenol conversion. Furthermore, it is observed that with the increase of WHSV from 2/h to 5/h, the selectivity to 2TBP and 4-TBP has a remarkable increase. On the contrary, the selectivity to 2, 4-DTBP and 2, 6-DTBP decreased with the increase
of WHSV from 2/h to 5/h. This is probably due to the faster reaction rate of single-alkylation and the relatively lower reaction rate of multi-alkylation. 3.6.4. Effect of reaction temperature and pore size of support on phenol conversion and product selectivity A series of reactions were conducted in the temperature range of 60–100 °C using the IL supported on carriers with different pore sizes as catalysts. The conversion of phenol decreased significantly beyond 100 °C since the dealkylation reaction became prominent as reported by earlier researchers [42]. However, at low temperature, the selectivity of dialkylate product was suppressed [43] and the extent of reactions was restricted by mass transfer limitations [44]. So the reaction temperature range from 60 °C to 100 °C was studied in this experiment. Fig. 9A summarizes the results of 1IL@SBA-15 (5 nm) catalyst obtained for the alkylation reaction conducted in the temperature range of 60–100 °C up to 2 h of reaction time. With increase in temperature from 60 °C to 80 °C, the conversion of phenol increased from 57.7% to 76.3%. Beyond 80 °C, there is a decrease in phenol conversion. The selectivity to 2,4-DTBP and 2,6-DTBP is highest at the temperature of 80 °C, accompanied with the selectivity to 2-TBP and 4-TBP is the lowest. All of this may be owing to that when the alkylation reaction controlled by kinetics, heating is an advantage to the reaction at the relatively low temperature range. The alkylation reaction is reversible exothermic reaction. The reaction temperature continues to increase, the phenol conversion and selectivity of 2, 4-DTBP decrease. This may be attributed to the control of thermodynamics and the dealkylation is dominant at higher temperature. On the other hand, it is notably found that the pore diameter of the support plays an important role influencing the catalytic activity. Fig. 9 shows a comparison of the conversion of phenol and the selectivity of products at the temperature range of 60–100 °C. The coverage of theoretical IL was similar for all samples. However, a significant difference between all 1-IL@SBA-15 (5, 8, 12 nm) was the curvature of the surface in the pores. The pore structure of mesoporous SBA-15 (5, 8, 12 nm) corresponded to that of hollow cylinders. Thus, the curvature of the walls of these cylinders decreased with larger pore size. Further, arrangement of the IL along the inner surface of pores with different pore sizes led to an increasing distance between the IL at larger pore size. The increased effective distance of the IL theoretically resulted in a lower phenol conversion and products selectivity [45]. However, the experimental results showed that in contrast to the samples of 1-IL@SBA15 (5 nm) and 1-IL@SBA-15 (12 nm), 1-IL@SBA-15 (8 nm) was not
Please cite this article as: T. Jiang et al., Alkylation of phenol/tert–butyl alcohol on ionic liquid-immobilized SBA-15 with different pore sizes, Journal of the Taiwan Institute of Chemical Engineers (2017), https://doi.org/10.1016/j.jtice.2017.09.029
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B
60
40
40
20
20
60
70 80 90 Temperature/oC
100
0
Phenol conversion/(mol%)
60
80
Phenol 2TBP 4TBP 2,4DTBP 2,6DTBP
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80 60
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0
60
70 80 90 Temperature/oC
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Product selectivity/%
Phenol 2TBP 4TBP 2,4DTBP 2,6DTBP
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Product selectivity/%
Phenol conversion/(mol%)
A
0
9
0
Phenol 2TBP 4TBP 2,4DTBP 2,6DTBP
80 60
80 60
40
40
20
20
0
60
70 80 90 Temperature/oC
100
Product selectivity/%
Phenol conversion/(mol%)
C
0
Fig. 9. Effect of different reaction temperatures and pore sizes of supports on phenol conversion and product selectivity over different catalysts (reaction condition: ntert -butanol /nphenol = 2:1, WHSV = 2/h, time = 2 h). (A) 1-IL@SBA-15(5 nm); (B) 1-IL@SBA-15(8 nm); (C) 1-IL@SBA-15(12 nm).
a significant influence on the product distribution, showing the highest phenol conversion and 2, 4-DTBP selectivity. It can be attributed that the extremely narrow pore of SBA-15 (5 nm) hinders the diffusion of the reactants.
-SO3 H immobilized ionic liquids to choose SBA-15(8 nm) as suitable supports to the application of phenol alkylation.
3.7. Recyclability of catalyst
Financial support from Project supported by the National Natural Science Foundation of China (51572115) and Project supported by the Graduate Science Research Innovation Program Foundation of the Jiangsu Higher Education Institution of China (KYLX15_1040) are gratefully acknowledged.
The recyclability of different catalysts was listed in Table 3. As shown in Table 3, for 1-IL@SBA-15 (5 nm) and 1-IL@SBA15 (12 nm), we found that the phenol conversion has obviously changed just repeated two or three times. This may be attributed to the following: one reason is that the unreacted reactants or products were diffused into the narrow mesoporous material channels. The other one is due to the part of supported IL that could be lost after several repetitions in relatively large pore size. 4. Conclusions The -SO3 H immobilized ionic liquids supported on three different pore sizes of well-ordered SBA-15 (5, 8, 12 nm) was successfully synthesized by impregnation method. The alkylation of phenol with tert–butyl alcohol was carried out over several IL@SBA-15 (5, 8, 12 nm) acid catalysts. The results showed that 1- IL@SBA-15 (8 nm) exhibited good catalytic activity for the alkylation of phenol with tert–butyl alcohol with the highest phenol conversion of 85.5% and 2,4-DTBP selectivity of 60.0% at the temperature of 80 °C and alcohol to phenol molar ratio of 2:1. It could be conclusion that the -SO3 H functionalized ionic liquids supported onto the SBA-15 materials with small pores are easy to block the pore and hinder the diffusion of the reactants resulting in decreasing of phenol conversion and product selectivity. So, it is essential for
Acknowledgments
References [1] Sakthivel A, Badamali SK, Selvam P. Para-selective tert-butylation of phenol over mesoporous H-AlMCM-41. Microporous Mesoporous Mater 20 0 0;39:457–63. [2] Krishnan AV, Ojha K, Pradhan NC. Alkylation of phenol with tertiary butyl alcohol over zeolites. Org Process Res Dev 2002;6:132–7. [3] Zhang K, Zhang HB, Xu GH. Alkylation of phenol with tert-butyl alcohol catalyzed by large pore zeolite. Appl Catal A 2001;207:183–90. [4] Changler K, Deng F, Dillow AK. Alkylation reaction in near-critical water in the absence of acid catalysts. Ind Eng Chem Res 1997;36:5175–9. [5] Sato T, Sekiguchi G, Adschiri T, Arai K. Non-catalytic and selective alkylation of phenol with propan-2-ol in supercritical water. Chem Commun 2001;17:1566–7. [6] Sumbramanian S, Mitra A, Satyanarayana CVV, Chakrabarty DK. Para-selective butylation of phenol over silicoaluminophosphate molecular sieve SAPO-11 catalyst. Appl Catal A 1997;159:229–40. [7] Shinde AB, Shrigadi NB, Samant SD. Tert-butylation of phenols using tert-butyl alcohol in the presence of FeCl3 -modified montmorillonite K10. Appl Catal A 2004;276:5–8. [8] Carltion AA. Alkylation of phenol with tert-butyl alcohol in the presence of perchloric acid. J Org Chem 1948;13:120–2. [9] Sakthivel A, Dapurkar SE, Gupta NM, Kulshreshtha SK, Selvam P. The influence of aluminium sources on the acidic behavior as well as on the catalytic activity of mesoporous H-AlMCM-41 molecular sieves. Microporous Mesoporous Mater 2003;65:177–87.
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[10] Bhatt N, Sharma P, Patel A, Selvam P. Supported 12-tungstophosphoricacid: an efficient and selective solid acid catalyst for tert-butylation of phenol and cresols. Catal Commun 2008;9:1545–50. [11] Rajadhyaksha RA, Chaudhari DD. Alkylation of phenol and pyrocatechol by isobutyl alcohol using superacid catalysts. Ind Eng Chem Res 1987;26:1276–80. [12] Chandler K, Liotta CL, Eckert CA, Schiraldi D. Tuning alkylation reactions with temperature in near-critical water. AIChE J 1998;44:2080–7. [13] Adam F, Hello KM, Ali TH. Solvent free liquid-phase alkylation of phenol over solid sulfanilic acid catalyst. Appl Catal A 2011;399:42–9. [14] Harmer MA, Sun Q. Solid acid catalysis using ion-exchange resins. Appl Catal A 2001;221:45–62. [15] Cole AC, Jensen JL, Ntai I, Tran KT, Weave KJ, Forbes DC, et al. Novel Bronsted acidic ionic liquids and their use as dual solvent-catalysts. J Am Chem Soc 2002;124:5962–6. [16] Forbes DC, Weaver KJ. Bronsted acidic ionic liquids: the dependence on water of the Fischer esterification of acetic acid and ethanol. J Mol Catal A 2004;214:129–32. [17] Gu Y, Shi F, Deng Y. Esterification of aliphatic acids with olefin promoted by Bronsted acidic ionic liquids. J Mol Catal A 2004;212:71–5. [18] Gui J, Cong X, Liu D, Zhang X, Hu Z, Sun Z. Novel Bronsted acidic ionic liquid as efficient and reusable catalyst system for esterification. Catal Commun 2004;5:473–7. [19] Elavarasan P, Kondamudi K, Upadhyayula S. Kinetics of phenol alkylation with tert-butyl alcohol using sulfonic acid functional ionic liquid catalysts. Chem Eng J 2011;166:340–7. [20] Gui JZ, Ban HY, Cong XH, Zhang XT, Hu ZD, Sun ZL. Selective alkylation of phenol with tert-butyl alcohol catalyzed by Bronsted acidic imidazolium salts. J Mol Catal A 2005;225:27–31. [21] Valkenberg MH, Castro CD, Holderich WF. Immobilization of ionic liquids on solid supports. Green Chem 2002;4:88–93. [22] Amarasekara AS, Owereh OS. Synthesis of a sulfonic acid functionalized acidic ionic liquid modified silica catalyst and applications in the hydrolysis of cellulose. Catal Commun 2010;11:1072–5. [23] Liu FJ, Wang L, Sun Q, Zhu LF, Meng XJ, Xiao FS. Transesterification catalyzed by ionic liquids on superhydrophobic mesoporous polymers: heterogeneous catalysts that are faster than homogeneous catalysts. J Am Chem Soc 2012;134:16948–50. [24] Ding W, Zhu W, Xiong J, Yang L, Wei A, Zhang M, et al. Novel heterogeneous iron-based redox ionic liquid supported on SBA-15 for deep oxidative desulfurization of fuels. Chem Eng J 2015;266:213–21. [25] Wang B, Zhang J, Zou X, Dong H, Yao P. Selective oxidation of styrene to 1,2-epoxyethylbenzene by hydrogen peroxide over heterogeneous phosphomolybdic acid supported on ionic liquid modified MCM-41. Chem Eng J 2015;260:172–7. [26] Rostamnia S, Gholipour B, Hosseini HG. Metal-and halogen-free hydrogensulfata ionic liquid/SBA-15 as catalyst in clean oxidation of aromatic and aliphatic organic sulfides with aqueous hydrogen peroxide. Process Saf Environ 2016;100:74–9. [27] Rostamnia S, Hassankhani A, Hossieni HS. Brӧnsted acidic hydrogensulfata ionic liquid immobilized SBA-15:[MPIm][HSO4 ]@SBA-15 as an environmentally friendly, metal- and halogen-free recyclable catalyst for Knoevenagel-Michael– cyclization processes. J Mol Catal A 2014;395:463–9. [28] Rostamnia S, Xin HC. Simultaneous application of ultrasonic irradiation and immobilized ionic liquid onto the SBA-15 nanoreactor (US/[MPIm]CI@SBA-15): a rubust, recyclable, and useful combined catalytic system for selective and waste-free Kabachnik Fields reaction. J Mol Liquids 2014;195:30–4.
[29] Doustkah E, Rostamnia S. Single site supported N-sulfonic acid and N-sulfamate onto SBA-15 for green and sustainable oxidation of sulfides. Mater Chem Phys 2016;177:229–35. [30] Rostamnia S, Lamei K, Pourhassan F. Generation of uniform and small particle size of palladium onto the SH-decorated SBA-15 pore-walls: SBA-15/(SH)XPd-NPY as a recoverable nanocatalyst for Suzuki-Miyaura coupling reaction in air and water. Rsc Adv 2014;5:1033. [31] Rostamnia S, Doustkhah E. Covalently bonded zwitterionic sulfamic acid onto the SBA-15 (SBA-15/PrEn-NHSO3 H) reveals good Brӧnsted acidity behavior and catalytic activity in N-formylation of amines. J Mol Catal A 2016;411:317–24. [32] Rostamnia S, Rahmani T, Xin HC. Pd(PrSO3 )@SBA-15 and Pd-NPs(PrSO)@SBA-15 hybrid material: a highly active, reusable, and selective interface catalyst for C-X activations in air and water. J Ind Eng Chem 2015;32:218–24. [33] Yang JB, Zhou LH, Guo XT, Li L, Zhang P, Hong RY, et al. Study on the esterification for ethylene glycol diacetate using supported ionic liquids as catalyst: catalysts preparation, characterization, and reaction kinetics, process. Chem Eng J 2015;280:147–57. [34] Liu S, Xie C, Yu S, Liu F. Dimerization of rosin using Brӧnsted-Lewis acidic ionic liquid as catalyst. Catal Commun 2008;9:2030–4. [35] Zhao DY, Feng JL, Huo QS, Melosh N, Fredrickson GH, Chmelka BF, Stucky GD. Triblock copolymer syntheses of mesoporous silica with periodic 50 to 300 angstrom pores. Science 1998;279:548–52. [36] Wang S, Huang Y, Li J. A novel method for synthesis of large-pore mesoporous molecular sieve SBA-15. J S Cent Univ Natl 2010;29:5–8. [37] Dindar MH, Yaftian MR, Hajihasani M, Rostamnia S. Refinement of contaminated water by Cr(Ⅵ), As(Ⅴ) and Hg(Ⅱ) using N-donor ligands arranged on SBA-15 platform; batch and fixed-bed column methods. J Taiwan Inst Chem E 2016;67:325–37. [38] Martinez F, Morales G, Martin A, Griekan R. Perfluorinated Nafion-modified SBA-15 materials for catalytic acylation of anisole. Appl Catal A 2008;347:169–78. [39] Zhou B, Yu DH, Xia JJ, Tang SS, Liu WM, Huang H. Immobilization of porcine pancreatic lipase onto ionic liquid modified mesoporous silica SBA-15. Biochem Eng J 2010;53:150–3. [40] Miah AT, Bharadwaj SK, Saikia P. Surfactant free synthesis of gold nanoparticles within meso-channels of non-functionalized SBA-15 for its promising catalytic activity. Powder Technol 2017;315:147–56. [41] Araújo MM, Silva LKR, Sczancoski JC, Orlandi MO, Longo E, Santos AGD, et al. Anatase TiO2 nanocrystals anchored at inside of SBA-15 mesopores and their optical behavior. Appl Surf Sci 2016;389:1137–47. [42] Yadav GD, Doshi NS. Alkylation of phenol with methyl-tert-butyl ether and tert-butanol over solid acids: efficacies of clay-based catalysts. Appl Catal A 2002;236:129–47. [43] Jong JI. The alkylation of phenol with isobutene. Recueil 1964;83:469–76. [44] Gu Y, Shi F, Deng Y. SO3 H-functionalized ionic liquid as efficient, green and reusable acidic catalyst system for oligomerization of olefins. Catal Commun 2003;4:597–601. [45] Zubrzycki R, Ressler T. Influence of pore size of SBA-15 on activity and selectivity of H3 [PMo12 O40 ] supported on tailored SBA-15. Microporous Mesoporous Mater 2015;214:8–14.
Please cite this article as: T. Jiang et al., Alkylation of phenol/tert–butyl alcohol on ionic liquid-immobilized SBA-15 with different pore sizes, Journal of the Taiwan Institute of Chemical Engineers (2017), https://doi.org/10.1016/j.jtice.2017.09.029