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Hydration of DCPD over sulfonic acid-functionalized SBA-15 catalyst
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Hydration of DCPD over sulfonic acid-functionalized SBA-15 catalyst Yu-Cheng Lin a, Yu-Wei Huang a, Ku-Hsiang Sung b, Tsung-Han Lin a, Soofin Cheng a,* a b
Department of Chemistry, National Taiwan University, Taipei 10617, Taiwan, ROC Chemical Systems Research Division, National Chung-Shan Institute of Science and Technology, Taoyuan 32599, Taiwan, ROC
A R T I C L E I N F O
Article history: Received 16 March 2016 Received in revised form 3 August 2016 Accepted 16 August 2016 Available online xxx Keywords: DCPD Hydration Solid catalyst Mesoporous materials Sulfonic acid SBA-15
A B S T R A C T
Sulfonic acid-functionalized SBA-15 materials (SA-SBA-15) with ordered channeling pores were synthesized by one-pot co-condensation and used to catalyze the hydration of dicyclopentadiene (DCPD). The target product, cydecanol (DCPD-OH) has been used as a modifier for polyester or alkyd resin. Propylsulfonic acid functionalized SBA-15 was found to be more efficient than the silica gel counterpart or arylsulfonic acid functionalized material in catalyzing DCPD hydration to yield DCPD-OH. The DCPD conversion and DCPD-OH yield increased with the decrease in H2O/DCPD ratio. Optimal DCPD conversion and DCPD-OH selectivity were obtained with the molar composition of DCPD:H2O:H+catalyst = 1:30:0.1. ß 2016 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.
Introduction Cyclopentadiene (CPD) and dicyclopentadiene (DCPD) are commercially obtained from coal tar and by steam cracking of Naphtha [1]. DCPD is formed by dimerization of CPD via a reversible Diels–Alder reaction, and the conversion occurs in hours at room temperature. In contrast, DCPD is cracked to the monomer by heating to 180 8C [2]. DCPD can be used as a monomer in polymerization reactions, either in olefin polymerization or in ring-opening metathesis polymerization. As the global oil supply and crude oil price are markedly affected by geo-political events and natural disasters, value-added products of raw petrochemical materials are urgently developed worldwide. Among them, the oxygen containing derivatives, like alcohols, epoxides, and ketones of DCPD have attracted the researchers. Cydecanol (CAS No. 133-21-1, 3a,4,5,6,7,7a-hexahydro-4,7methano-1H-inden-5-ol, briefly termed DCPD-OH) has been used as a modifier for polyester or alkyd resin. It is also a potentially important chemical in the flavor and fragrance industry. It is prepared conventionally by a batchwise, or liquid-phase hydration of DCPD in the presence of concentrated sulfuric acid [3]. Corrosion hazard, difficulties in handling and product separation are the drawbacks of liquid acid catalysts. Most of all, polymeric side
* Corresponding author. Fax: +886 2 33668671. E-mail address: [email protected] (S. Cheng).
products are easily generated in strong acid and also during the distillation procedure of products separation. To overcome these drawbacks, solid acids of easy separation and recyclability are considered. Nafion [4], resins [5], and metal oxides [5,6] have been reported as the catalysts in olefins hydration reaction. However, Nafion is extremely expensive. Talwalkar et al. [5] compared several solid catalysts, including ion-exchange resins, ZSM-5 and b zeolites for DCDP hydration at 90 8C. They found that Amberlyst-15 offered the highest conversion of 4% and cydecanol selectivity is more than 95% in 4.5 h. However, chemical properties of the resins would change as the reaction proceeds, and the surface area and active sites lost during the reaction [5]. Okazaki and Harada [6] performed vapor-phase hydration at 120–220 8C in a conventional flow reactor at an ordinary pressure over various solid acid catalysts, including Amberlyst, Nafion, silica, alumina, aluminosilicate, titanosilicate, and niobic acid. A gaseous mixture of DCPD (11.8 vol%) and H2O (88.2 vol%) was fed to the catalyst bed by using N2 as a carrier gas at a contact time of W/F = 5.9 g h mol1. Among the catalysts, niobic acid heat-treated at 300 8C exhibited the highest catalytic activity. The optimal reaction temperature over niobic acid was 170 8C, which is close to the decomposition temperature of DCPD. However, the catalysts deactivated quickly during the gas phase reaction. The data collected in first 30 min of time-on-stream were used for comparison. Even so, the highest conversion was 17%, and the conversion was extremely sensitive to the reaction temperature. Therefore, solid acid catalysts of high activities are still necessary to be developed for DCPD hydration.
http://dx.doi.org/10.1016/j.jiec.2016.08.013 1226-086X/ß 2016 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.
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Since the discovery of M41S mesoporous silica by the Mobil oil company in 1992 [7], the mesoporous materials with large surface area and pore volume, and narrowly distributed and tunable pore diameters of 2–10 nm have received great attention for their potential applications in adsorption [8,9], catalysis [10–12], and electron-optical devices. Among the mesoporous silica materials, SBA-15 of 2D-hexagonal p6mm pore structure is particularly desirable because of its relatively large pore diameters and higher hydrothermal stability in comparison with MCM-41, its analogue in the M41S family [13]. Functionalities have been introduced onto mesoporous silica materials in order to extend their applications. For example, Ti incorporated MCM-41 and SBA-15 are effective catalysts in epoxidation of large olefin molecules, hydroxylation of aromatic compounds, and photocatalytic degradation of phenol [14,12,15–21]. It is also reported that the Ti-SBA-15 catalyst is more stable under the reaction conditions during the epoxidation than the Ti-MCM-41 catalyst [22,23]. Organic functional groups have also been incorporated onto the mesoporous silica materials by either grafting or co-condensation methods [24–26]. The cocondensation method is often preferred to the post-grafting pathway because it minimizes processing steps and provides a more uniform distribution of the organic functionalities [27]. In addition, one-pot co-condensation synthesis often provides a higher loading of organic functionalities without closing the framework mesopores [28]. The purpose of this study is to develop a solid acid which can take the place of mineral acids in catalyzing DCPC hydration. In consideration of the sizes of reactant and product molecules, SBA15 materials of relatively large pores functionalized with propyland aryl-sulfonic acid groups were studied. The functionalized SBA15 were prepared by one-pot co-condensation and used to catalyze the hydration of DCPD. The optimal conditions in terms of reactant ratio, operation temperature, catalyst weight and solvent were investigated in order to obtain high DCPD-OH yield and selectivity. Experimental Chemicals and reagents All the chemicals were used as received without purification. DCPD was provided by National Chung-Shan Institute of Science and Technology, Taiwan. The composition and purity of DCPD were analyzed by a Perkin Elmer gas chromatograph with mass detector (Clarus 600 GC/MS). Preparation of catalysts Two kinds of sulfonic acid functionalized SBA-15 materials were examined for their catalytic performance in DCPD hydration. Their structures are shown in Scheme 1. The propylsulfonic acidfunctionalized SBA-15 materials with short-channeling pores were synthesized by co-condensation of TEOS and MPTMS in the conventional SBA-15 synthesis solution with the addition of an appropriate amount of Zr(IV) ions and H2O2[12]. In the optimal synthesis condition, 2.0 g of Pluronic P123 (Aldrich, Mn = 5800) and 0.32 g of zirconyl chloride octahydrate (ZrOCl28H2O, Acros) were dissolved in 80 g of 2.0 M HCl (Acros) solution at 35 8C. To this solution 4.2 g of TEOS (Acros) was introduced and hydrolyzed for 2 h, followed by the addition of MPTMS (Acros) and 0.9 g of 35 wt% H2O2 (Showa) aqueous solution. The molar composition of the reactants was 0.017 P123:1 TEOS:0.1 MPTMS:0.05 ZrOCl2:7.9 HCl:9 H2O2:220 H2O. The resulting mixtures were stirred at 40 8C for 20 h and then transferred into a polypropylene bottle and reacted at 90 8C under static condition for 24 h. The solid products were recovered by filtration, washing with ethanol, and dried at room temperature overnight. The P123 template was removed by
Scheme 1. Sulfonic acid-functionalized silica materials.
refluxing with ethanol. Finally, the materials were filtered, washed several times with water and ethanol, and dried at 100 8C. The sample is termed PrSA-SBA-15. Arylsulfonic acid-functionalized SBA-15 was prepared by onepot co-condensation of TEOS and (chlorosulfonylphenyl) ethyltrimethoxysilane (abbreviated CSPTMS, 50% in DCM) following the procedures similar to that mentioned in previous paragraph. The molar composition of the reactants was 0.017 P123:1TEOS:0.1CSPTMS:0.3 H2O2:5.8 HCl:165 H2O. The sample is termed ArSA-SBA-15. In order to examine the effect of ordered pores in silica materials on catalytic performance, propylsulfonic acid groups were anchored on two commercially available silica gels (Merk silica gel 60 and Alfa Aesar silica gel large pore) by grafting method. 2 g of the silica gel was refluxed in 100 mL toluene containing 2 g MPTMS (S/Si molar ratio of 0.3) for 24 h, followed by filtration, washing with ethanol, dried at 50 8C. The thiol groups were oxidized to sulfonic acid groups by mixing the dried powders in 50 mL 35% H2O2 and 3 drops of 18 M sulfuric acid at 35 8C under stirring for 8 h, followed by thoroughly washing till pH neutral. The solid products dried at 100 8C overnight are termed PrSA-Silica I and II, corresponding to Merk and Alfa silica sources, respectively. Characterization Powder X-ray diffraction (XRD) patterns were recorded using a PANalytical X’pert Pro diffractometer with Cu Ka radiation operated at 40 mA and 45 kV. N2 adsorption–desorption isotherms were measured using a Micromeritics Tristar 3000 system at liquid nitrogen temperature (77 K). Before the measurements, the samples were degassed at 473 K for 10 h under vacuum condition (103 Torr). The surface area was calculated by using Brunauer– Emmett–Teller (BET) method. Pore size was determined by Barrett–Joyner–Halenda (BJH) method using the desorption branch of the isotherms. The silica content was determined using thermogravimetric analysis by a Hi–Res TA 2950 analyzer under 60 mL/min air flow and 10 8C min1 ramping rate. The acid amounts in the materials were determined by ion-exchange with NaCl, followed by acid-base titration of the filtrate. In a typical experiment, 0.20 g of the solid was first dried at 50 8C for 1 day and then added to 40 mL 2 M NaCl solution. The suspension was mixed to reach equilibrium for 6 h, and then the solid was filtered and washed with a small amount of water. Finally, the filtrate was titrated by 0.01 M NaOH aqueous solution. Catalytic reaction Liquid phase hydration of DCPD was carried out in a twonecked round bottom flask connected with a reflux condenser and a thermometer. For the test reaction, 1.32 g (0.01 mol) of DCPD and
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5.4–16.2 g (0.3–0.9 mol) of water were mixed under vigorous stirring at 90 8C. 0.5–1 g of the solid acid catalyst was added to start the reaction, and the reaction was run for 8 h or longer. After cooling to room temperature, 10–30 g isopropanol were added, versus different water amounts, as the co-solvent to make sure homogeneous mixing of the products. In addition, 1.08 g (10 mmol) of o-xylene was added as the internal standard. The products were collected by filtering syringe and analyzed by a Shimadzu gas chromatograph (GC) 14B equipped with a RTX-1 capillary column (30 m in length, 0.35 mm in diameter) and a FID detector. The GC analysis condition was set as following: injection port 250 8C, detector port 280 8C, and column temperature from 60 to 280 8C with a ramping rate of 20 8C min1.
surface areas of 589 and 377 m2/g, pore diameters of 5.3 and 7.0 nm, and pore volumes of 0.75 and 0.67 cm3/g, respectively. On the other hand, the silica gel materials (PrSA-Silica I and II) from two commercial brands functionalized with propylsulfonic acid have surface areas of 145 and 393 m2/g, and pore volumes of 0.24 and 0.53 cm3/g, respectively. Moreover, the acid capacities determined by NaOH titration of the filtrates of NaCl-exchanged solids are almost proportional to the surface areas (Table 1). Thus, PrSA-SBA-15 has the highest acid capacity of 0.83 mmol/g, while PrSA-Silica I has the lowest acid capacity of 0.30 mmol/g. Because relatively large weight and volume of PrSA-Silica I is needed to achieve the same acid amount as other three catalysts, this sample is abandoned from further catalytic tests.
Results and discussion
Reactant and product analysis by GC
Catalyst characterization
Because the target product DCPD-OH was not commercially available, it was prepared according to the procedure reported in Ref. [3] by hydration of 25 g DCPD using 75 g 40% H2SO4 as the catalyst at 60 8C for 2 h. The products were a mixture of two immiscible phases in dark brown color, indicating a large amount of polymeric species or coke was formed under such a strong acidic condition. After separating the aqueous phase by a separation funnel, the organic products were extracted with nhexane, followed by solvent evaporation with a rotor-evaporator. The purified DCPD-OH was identified by 1H and 13C NMR spectroscopy and used for making the calibration curve of GC analysis. The DCPD-OH product appeared at GC as a single peak at 5.48 min, as shown in Fig. 2(A). However, the 1H and 13C NMR spectra showed that it was a mixture of mono alcohols resulting from hydration at the six-ring site of DCPD, as shown in Scheme 2. Other than DCPD-OH, GC showed two minor products appeared at about twice of the retention time (10.38 and 10.48 min) of that of DCPD-OH in the organic phase. The masses of these two GC peaks identified by MS analysis to be 282 (Fig. 2(B)), and these minor products were likely the ether product formed by condensation of two DCPD-OH molecules. Using 40% H2SO4 as the catalyst, the area ratio of DCPD-OH/ether was about 65/35. This result implies that dehydration of DCPD-OH can occur in the presence of strong mineral acids.
Small-angle XRD patterns of prepared sulfonic acid functionalized silica materials are shown in Fig. 1(A). Both PrSA-SBA-15 and ArSA-SBA-15 samples show three well-resolved diffraction peaks corresponding to the (100), (110) and (200) planes of 2Dhexagonal p6mm pore structure, and the patterns are akin to that of conventional SBA-15 material [13]. In contrast, the functionalized silica gels have no diffractions in this region. Nitrogen adsorption–desorption isotherms of these materials are shown in Fig. 1(B). PrSA-SBA-15 and ArSA-SBA-15 samples have the characteristic type IV isotherms with H1 hysteresis loop appears at P/P0 of 0.6–0.8, indicating that large mesopores with narrow PSDs are present, akin to the conventional SBA-15 material [13]. On the other hand, one of the silica gel samples, PrSA-Silica I, has no apparent N2 adsorption until P/P0 0.9, probably attributing to the inter-particle voids. The other silica gel sample PrSASilica II also gives type IV isotherm. However, the hysteresis covers a relatively wider range of partial pressure, implying a wide pore size distribution. The BJH pore size distributions shown in Fig. 1(C) confirm these results. The physicochemical properties of these sulfonic acid functionalized silica materials are shown in Table 1. The SBA-15 materials functionalized with propyl- and aryl-sulfonic acid groups have
(B)
(A)
0.16
(C)
2000 0.14
N2 Adsorbed (cm g STP)
1600
(c)
0.12
(0,1461)
(b)
0.88°
-1
(c)
3
1200
1.38° 1.57°
(0,1042) 800
1.69°
0.02
(a) (0,0)
0
1
2
3
2 theta
4
(b)
0.04
(0,547)
(a)
(a)
0.08 0.06
(b)
400 1.46°
(c)
0.10
3
-1
0.83°
(d)
(d)
dv /d (cm g STP)
Intensity (Arbitary unit)
(d)
5
6
0.00
0 0.0 0.2 0.4 0.6 0.8 1.0 1.2
P/P0
2
4
6
8
10
PSD (nm)
Fig. 1. (A) Powder X-ray diffraction patterns, (B) N2 adsorption–desorption isotherms, and (C) BJH pore-size distributions of (a) PrSA-SBA-15, (b) ArSA-SBA-15, (c) PrSA-Silica I, and (d) PrSA-Silica II.
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Table 1 Physicochemical properties of sulfonic acid-functionalized silica materials. Sample
Surface areaa (m2/g)
Pore volume (cm3/g)
Pore diameterb (nm)
Acid capacityc (H+ mmol/g)
PrSA-SBA-15 ArSA-SBA-15 PrSA-Silica I PrSA-Silica II
590 377 145 393
0.75 0.67 0.24 0.54
5.9 7.5 – 5.1
0.83 0.60 0.30 0.52
a b c
Determined by BET method. Determined from the peak position of BJH PSD profiles using the desorption branches of the isotherms. Determined by NaOH titration on the filtrate of NaCl(aq) exchanged samples.
One of the difficulties encountered in olefins hydration is the immiscibility of olefins and water [29,30]. In order to obtain a homogeneous solution of the products for GC analysis, a co-solvent was added to the products. After testing with several solvents, it was found that iso-propanol (IPA) was the best co-solvent. Moreover, IPA of about twice weight of water was needed to achieve homogeneous mixing of all components in the products. The injection port temperature of GC was found to be important for products analysis. On one hand, DCPD was considered to
undergo reverse Diels–Alder reaction to form two CPD molecules at temperatures above 180 8C. On the other hand, the boiling temperature of DCPD-OH is as high as 246 8C. In order to achieve complete evaporation of the product without decomposition of the reactant, the temperature of injection port was varied from 150 to 250 8C. Since no CPD peak was detected even the injection port was raised to 250 8C, it was chosen for the followed analysis. During the process of making calibration curves of DCPD and DCPD-OH using o-xylene as the internal standard, it was noticed
Fig. 2. GC–MS analysis of products formed in DCPD hydration using H2SO4 catalyst: (A) GC profile, (B) mass spectra of GC peaks at retention time (a) 10.47 min, (b) 10.38 min, (c) 5.48 min.
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Table 3 Effect of H2O/DCDP molar ratio on DCPD hydration. H2O/DCPD Molar ratio
30 60 90 30|
Scheme 2. Hydration and polymerization of DCPD in the presence of acid catalysts.
that the slopes of calibration curves changed with the amount of water and IPA added. Therefore, the product analysis was based on the calibration curves made with the mixtures containing water and IPA as those needed for optimal DCPD-OH yield and product dissolution, respectively. The weight ratios for calibration curve of DCPD were DCPD:o-xylene:H2O:IPA = 0.26–1.33:1.06:10.8:20, and those for calibration curve of DCPD-OH were DCPD-OH:oxylene:H2O:IPA = 0.068–0.619:1.06:10.8:20. Catalytic results without co-solvents Sulfonic acid functionalized SBA-15 and silica gel materials are used as the catalysts in DCPD hydration at 90 8C, and the results after 8 h are shown in Table 2. Entries 1–3 compare the catalytic performances of different functionalized silica materials based on the same acid amounts of 0.3 mmol H+ and H2O/DCPD molar ratio kept at 30. The highest DCPD conversion is obtained on SBA-15 functionalized with arylsulfonic acid, while propylsulfonic acid functionalized silica gel gives the lowest DCPD conversion. The result is attributed to the stronger acidic strength of arylsulfonic acid than propylsulfonic acid [30]. However, ArSA-SBA-15 catalyst also gives the lowest yield and selectivity of DCPD-OH. It is noticed that relative larger amount of brown polymeric species or coke are formed over ArSA-SBA-15. These results indicate that DCPD polymerization is likely favored to hydration over ArSA-SBA-15 catalyst. In comparison, propylsulfonic acid functionalized materials of relatively weaker acidic strength are favored catalysts in DCPD hydration. Although PrSA-Silica II and PrSA-SBA-15 have similar catalytic performances, the latter gives slightly higher DCPD conversion and DCPD-OH yield. It is attributed to the well dispersed acidic sites on SBA-15 can provide better accessibility of the reactants and more effectively catalyze the hydration. Moreover, the markedly different acid capacities for functionalized silica gels obtained from different brands demonstrate the difficulties in material control. Therefore, only the catalytic performance of PrSA-SBA-15 is studied hereafter. Entries 2, 4 and 5 in Table 2 show the effect of catalyst weight. Both DCPD conversion and DCPD-OH yield increase with the increase of catalyst weight. It is however surprised to see that the DCPD-OH selectivity dramatically increases when the catalyst
Table 2 Catalytic performance of SBA-15 and silica gel functionalized with sulfonic acid groups in DCPD hydration. Entry Catalyst
ArSA-SBA-15 PrSA-SBA-15 PrSA-Silica II PrSA-SBA-15 PrSA-SBA-15
0.5 0.38 0.58 0.5 1
16.1 10.8 9.4 12.4 16.2
4.6 5.1 4.9 6.0 14.8
DCPD Conv.
DCPD-OH
(g)
(mol)
(%)
Yield (%)
Select. (%)
5.4 10.8 16.2 5.4
0.3 0.6 0.9 0.3
16.2 12.9 10.7 12.2
14.8 10.0 8.4 4.9
91.6 80.1 78.2 40.3
Reaction condition: 1 g PrSA-SBA-15 catalyst, DCPD 1.32 g (0.01 mol), 90 8C, 8 h. | Using 0.001 mol H2SO4(aq) as the homogeneous catalyst.
weight is increased from 0.5 to 1 g. It is also noticed that the colors of used catalysts are different. The color is in deeper brown for the 0.5 g catalyst than 1 g catalyst, indicating that more polymeric species are formed when less amount of catalyst is used. One of possible explanations is that polymerization of DCPD proceeds in a relatively faster rate than DCPD hydration. When a larger quantity of PrSA-SBA-15 catalyst is present, the rate of DCPD hydration increases and less amount of DCPD is left for polymerization. Table 3 shows the results of the catalytic reaction at 90 8C after 8 h with different H2O/DCDP ratios using PrSA-SBA-15 as the catalyst. It can be seen that DCPD conversion and DCPD-OH yield decrease with the increase of H2O/DCDP ratio. The highest DCPD conversion of 16.2% and DCPD-OH yield of 14.8% were obtained when H2O/DCDP molar ratio was 30. It is also noticeable that the DCPD-OH selectivities are quite high over PrSA-SBA-15 catalyst. In the optimal condition, the selectivity can reach up to ca. 92%. In contrast, the DCPD-OH selectivity is only ca. 40% using aqueous H2SO4 of the same acid amount as that of PrSA-SBA-15 as a homogeneous catalyst (entry |). Again, the side products are polymeric species or coke since some precipitates of deep brown color are obtained in the homogeneous catalytic system. The polymeric products are apparently less over the solid catalysts since only the surface of solid turns brown after the reaction. These results demonstrate that PrSA-SBA-15 is favorable to sulfuric acid in giving higher yield and selectivity of DCPA-OH. The results also indicate that excess amount of water may dilute the concentration of DCPD and reduce the rate of DCPD hydration. Accordingly, less amount of water should be used to achieve higher DCPD conversion and DCPD-OH yield. Nevertheless, 5 g of water is almost the minimum amount to have 1 g of PrSA-SBA-15 powders completely immersed. The results of varying the reaction period are shown in Table 4. Notice that H2O/DCPD molar ratio is kept at 60. The DCPD conversion and DCPD-OH yield increase as the reaction period increases. However, the DCPD-OH selectivity decreases from ca. 80–82% to 71% when the reaction is prolonged to 24 h at 90 8C, indicating that more polymerization products are formed after long reaction period. The effect of reaction temperature is shown in Table 5. The DCPD conversion and DCPD-OH yield increase with reaction temperature. However, optimal selectivity is obtained at 90 8C. It was also noticed that the color of the used catalyst turned deeper brown color with the increase of temperature. These results imply that more polymeric species are formed at higher temperatures. Table 4 Effect of reaction period on DCPD hydration.
Wt. of Catal. (g) DCPD Conv. (%) DCPD-OH Yield (%) Select. (%)
1 2 3 4 5
H2O
28.7 47.0 51.8 48.2 91.6
Reaction condition: DCPD 1.32 g (0.01 mol), H2O 5.4 g (0.3 mol), 90 8C, 8 h.
Reaction period (h)
DCPD Conv. (%)
8 14.5 24
12.9 17.5 28.2
DCPD-OH Yield (%)
Select. (%)
10.0 14.4 20.1
80.1 82.4 71.3
Reaction condition: 1 g catalyst, DCPD 1.32 g (0.01 mol), H2O 10.8 g (0.6 mol), 90 8C.
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Table 5 Effect of reaction temperature on DCPD hydration. Temperature (8C)
DCPD Conv. (%)
70 90 100–110 (reflux)
8.3 16.2 33.3
Table 6 Effect of co-solvents on DCPD hydration. DCPD-OH Yield (%)
Select. (%)
5.1 14.8 26.4
61.3 91.6 79.1
Reaction condition: 1 g catalyst, DCPD 1.32 g (0.01 mol), H2O 5.4 g (0.3 mol), 8 h.
Co-solvent/ b.p. (8C)
IPA/82.6 – THF/66
Wt. of co-solvent (g)
5 0 6.5
H2O
DCPD Conv. (%)
Wt. (g)
Mole
2.0 5.4 0.5
0.11 0.3 0.03
6.6 12.4 7.0
DCPD-OH Yield (%)
Select. (%)
4.7 6.0 Trace
73.0 48.2 Trace
Reaction condition: 0.5 g PrSA-SBA-15 catalyst, DCPD 1.32 g (0.01 mol), reflux temperature, 8 h.
In consideration that DCPD hydration and polymerization are two parallel reactions catalyzed by the acid, as shown in Scheme 2, the activation energies of these two reactions can be estimated from the yield rates of DCPD-OH and polymeric species obtained in Table 5 as a function of temperature. Assuming that both reactions are pseudo first order, the Arrhenius plots are obtained and shown in Fig. 3. The activation energy of DCPD hydration is estimated to be 6.13 kJ/mol, while that of polymerization is 2.84 kJ/mol over PrSA-SBA-15 catalyst. The relatively low activation energy of polymerization explains the experimental observation that polymeric species are easily formed in strong acid or when insufficient amount of acid catalyst is present.
Table 7 Reusability of the PrSA-SBA-15 catalyst in DCPD hydration. Run
DCPD Conv. (%)
1 2 3 4 5
16.2 12.1 11.4 10.2 10.8
DCPD-OH Yield (%)
Select. (%)
14.8 7.1 6.0 5.2 4.1
91.6 58.3 52.2 51.3 38.2
Reaction condition: 1 g catalyst, DCPD 1.32 g (0.01 mol), H2O 5.4 g (0.3 mol), 90 8C, 8 h.
Catalytic results with co-solvents Recycling of the SA-SBA-15 catalyst Co-solvents are added in order to have reactants in a miscible liquid phase. Meanwhile, the amount of water can be reduced. However, there are not too many choices of co-solvents in consideration of low boiling point and minimum volume needed. It turns out that two of the most suitable co-solvents are IPA and THF. Table 6 lists the minimum amounts of IPA and THF used to achieve miscible phases of 0.01 mol of DCDP and water. The H2O/DCPD molar ratio can be reduced to 11 with 5 g IPA, while that can be further decreased to 3 with 6.5 g THF. The catalytic results show that DCPD conversions and DCPD yields are lower in the presence of co-solvents. However, higher DCPD-OH selectivity is obtained in IPA than that without cosolvent. In contrast, only trace amount of DCPD-OH is detected in THF, probably due to the relatively low boiling point. Although addition of IPA as co-solvent can ensure the miscibility of DCPD and water, additional evaporation process is necessary for products separation and purification.
The used PrSA-SBA-15 catalyst is easily recycled and regenerated. The solid catalyst collected by filtration was regenerated by heating in a mixture of 250 mL IPA and 15 mL 2 M HCl at 50 8C overnight, filtering again, washing with IPA and ethanol, then drying at 50 8C. The performances of the regenerated catalysts in DCPD hydration up to 4 times of recycling are compared with that of fresh one in Table 7. The DCPD conversion decreases to about three quarters of that of fresh catalyst in the first recycle, while the DCPD-OH yield decreases to about a half of the fresh one. That is attributed to that polymeric species coating on the outer surfaces of the catalyst cannot be thoroughly removed by heating treatment in alcohols. Nevertheless, the decreases in DCPD conversion and DCPD-OH yield become less significant when recycling number increases. Although the catalytic activity of the regenerated SBA15 catalyst cannot be completely recovered due to partially foiling of the active sites by polymeric products, the easy separation of the solid acid catalyst from the products still offers the advantage of avoiding in further polymerization of unreacted DCPD during products separation by distillation. Conclusions
Fig. 3. Arrhenius plots of (A) DCPD-OH hydration and (B) polymerization over PrSASBA-15 catalyst.
Propylsulfonic acid-functionalized SBA-15 material with ordered channeling pores and acid capacities around 1 mmol H+g1 is an efficient catalyst in the hydration of dicyclopentadiene. However, polymerization of DCPD is a parallel side reaction of lower activation energy. Aryl-SA-SBA-15 which has stronger acidic strength is less favorable to Propyl-SA-SBA-15 as the catalyst, giving more polymeric products and lower yield and selectivity of DCPD-OH. PrSA-SBA-15 catalyst is also favorable to sulfuric acid in giving higher yield and selectivity of DCPA-OH. Although adding IPA as the co-solvent can ensure the miscibility of DCPD and water, additional evaporation process is necessary for products separation and purification. Relatively high DCPD conversion and DCPDOH yield can be achieved without co-solvents, and these values increase with the decrease in H2O/DCPD ratio. The optimal DCPD conversion and DCPD-OH selectivity are obtained over Propyl-SASBA-15 at 90–100 8C with the molar composition of DCPD:H2O:H+catalyst = 1:30:0.1. The DCPD conversion of 16.2% and DCPD-OH
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selectivity of 91.6% in 8 h are much higher than those reported by Talwalkar et al. [5] using Amberlyst-15 resin catalyst (ca. 4% DCPD conversion and <35% DCPD-OH selectivity) at the same temperature of 90 8C. The easy separation of the solid acid catalyst from the products offers the advantage of avoiding in further polymerization of unreacted DCPD during products separation by distillation. Acknowledgment Financial support from the National Chung-Shan Institute of Science and Technology, Taiwan (CSIST-1246-V204 (104)) is gratefully acknowledged. References [1] D. Ho¨nicke, R. Fo¨disch, P. Claus, M. Olson, Ullmann’s Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2002. [2] R.B. Moffett, Org. Synth. Coll. 4 (1962) 238. [3] H.A. Bruson, T.W. Riener, J. Am. Chem. Soc. 67 (1945) 723. [4] H. Kasei, Jpn. Patent Kokai 55-19205, 56-59723. [5] S. Talwalkar, P. Kumbhar, S. Mahajani, Catal. Commun. 7 (2006) 717. [6] S. Okazaki, H. Harada, Chem. Lett. 17 (1988) 1313. [7] C.T. Kresge, M.E. Leonowicz, W.J. Roth, J.C. Vartuli, J.S. Beck, Nature 359 (1992) 710. [8] X. Fang, G.E. Frywell, L.Q. Wang, A.Y. Kim, J. Liu, K.M. Kemner, Science 276 (2007) 923.
7
[9] J.M. Sun, H. Zhang, R.J. Tian, D. Ma, X.H. Bao, D.S. Su, H.F. Zou, Chem. Commun. (2006) 1322. [10] A. Corma, Chem. Rev. 97 (1997) 237. [11] S.Y. Chen, J.F. Lee, S. Cheng, J. Catal. 270 (2010) 196. [12] S.Y. Chen, C.Y. Tang, J.F. Lee, L.Y. Jang, T. Tatsumi, S. Cheng, J. Mater. Chem. 21 (2011) 2255. [13] D. Zhao, J. Feng, Q. Huo, N. Melosh, G.H. Fredrickson, B.F. Chmelka, G.D. Stucky, Science 279 (1998) 548. [14] F. Berube, B. Nohair, F. Kleitz, S. Kaliaguine, Chem. Mater. 22 (2010) 1988. [15] A. Wro´blewska, E. Makuch, E. Sokalska, M. Malko, React. Kinet. Mech. Catal. 113 (2014) 519. [16] A. Wro´blewska, Molecules 19 (2014) 19907. [17] A. Wro´blewska, A. Fajdek, J. Wajzberg, E. Milchert, J. Hazard. Mater. 170 (2009), 405–410 A. [18] A. Wro´blewska, E. Makuch, React. Kinet. Mech. Catal. 105 (2012) 451. [19] K. Kulawik, G. Schulz-Ekloff, J. Rathousky´, A. Zukal, J. Had, Collect. Czech. Chem. Commun. 60 (1995) 451. [20] G.D. Lee, S.G. Kim, H.H. Jeong, S.S. Park, S.S. Hong, Solid State Phenom. 124–126 (2007) 1793. [21] L. Yang, Z. Jiang, S. Lai, Ch. Jiang, H. Zhong, Int. J. Chem. Eng. (2014), Article ID 691562, 7 pp.. [22] A. Wro´blewska, E. Makuch, Pol. J. Chem. Technol. 4 (15) (2013) 111. [23] A. Wro´blewska, E. Makuch, J. Adv. Oxid. Technol. 17 (1) (2014) 44. [24] S.-Y. Chen, T. Yokoi, C.-Y. Tang, L.-Y. Jang, T. Tatsumi, J.C.C. Chan, S. Cheng, Green Chem. 13 (2011) 2920. [25] X. Wang, K.S.K. Lin, J.C.C. Chan, S. Cheng, J. Phys. Chem. B 109 (2005) 1763. [26] S. Cheng, X. Wang, S.-Y. Chen, Top. Catal. 52 (2009) 681. [27] A. Walcarius, C. Delacote, Chem. Mater. 15 (2003) 4181. [28] D.J. Macquarrie, D.B. Jackson, Chem. Commun. (1997) 1781. [29] T. Nakato, Y. Toyoshi, M. Kimura, T. Okuhara, Catal. Today 52 (1999) 23. [30] C.-C. Chen, S. Cheng, L.-Y. Jang, Microporous Mesoporous Mater. 109 (2008) 258.
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Hydration of DCPD over sulfonic acid-functionalized SBA-15 catalyst Yu-Cheng Lin a, Yu-Wei Huang a, Ku-Hsiang Sung b, Tsung-Han Lin a, Soofin Cheng a,* a b
Department of Chemistry, National Taiwan University, Taipei 10617, Taiwan, ROC Chemical Systems Research Division, National Chung-Shan Institute of Science and Technology, Taoyuan 32599, Taiwan, ROC
A R T I C L E I N F O
Article history: Received 16 March 2016 Received in revised form 3 August 2016 Accepted 16 August 2016 Available online xxx Keywords: DCPD Hydration Solid catalyst Mesoporous materials Sulfonic acid SBA-15
A B S T R A C T
Sulfonic acid-functionalized SBA-15 materials (SA-SBA-15) with ordered channeling pores were synthesized by one-pot co-condensation and used to catalyze the hydration of dicyclopentadiene (DCPD). The target product, cydecanol (DCPD-OH) has been used as a modifier for polyester or alkyd resin. Propylsulfonic acid functionalized SBA-15 was found to be more efficient than the silica gel counterpart or arylsulfonic acid functionalized material in catalyzing DCPD hydration to yield DCPD-OH. The DCPD conversion and DCPD-OH yield increased with the decrease in H2O/DCPD ratio. Optimal DCPD conversion and DCPD-OH selectivity were obtained with the molar composition of DCPD:H2O:H+catalyst = 1:30:0.1. ß 2016 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.
Introduction Cyclopentadiene (CPD) and dicyclopentadiene (DCPD) are commercially obtained from coal tar and by steam cracking of Naphtha [1]. DCPD is formed by dimerization of CPD via a reversible Diels–Alder reaction, and the conversion occurs in hours at room temperature. In contrast, DCPD is cracked to the monomer by heating to 180 8C [2]. DCPD can be used as a monomer in polymerization reactions, either in olefin polymerization or in ring-opening metathesis polymerization. As the global oil supply and crude oil price are markedly affected by geo-political events and natural disasters, value-added products of raw petrochemical materials are urgently developed worldwide. Among them, the oxygen containing derivatives, like alcohols, epoxides, and ketones of DCPD have attracted the researchers. Cydecanol (CAS No. 133-21-1, 3a,4,5,6,7,7a-hexahydro-4,7methano-1H-inden-5-ol, briefly termed DCPD-OH) has been used as a modifier for polyester or alkyd resin. It is also a potentially important chemical in the flavor and fragrance industry. It is prepared conventionally by a batchwise, or liquid-phase hydration of DCPD in the presence of concentrated sulfuric acid [3]. Corrosion hazard, difficulties in handling and product separation are the drawbacks of liquid acid catalysts. Most of all, polymeric side
* Corresponding author. Fax: +886 2 33668671. E-mail address: [email protected] (S. Cheng).
products are easily generated in strong acid and also during the distillation procedure of products separation. To overcome these drawbacks, solid acids of easy separation and recyclability are considered. Nafion [4], resins [5], and metal oxides [5,6] have been reported as the catalysts in olefins hydration reaction. However, Nafion is extremely expensive. Talwalkar et al. [5] compared several solid catalysts, including ion-exchange resins, ZSM-5 and b zeolites for DCDP hydration at 90 8C. They found that Amberlyst-15 offered the highest conversion of 4% and cydecanol selectivity is more than 95% in 4.5 h. However, chemical properties of the resins would change as the reaction proceeds, and the surface area and active sites lost during the reaction [5]. Okazaki and Harada [6] performed vapor-phase hydration at 120–220 8C in a conventional flow reactor at an ordinary pressure over various solid acid catalysts, including Amberlyst, Nafion, silica, alumina, aluminosilicate, titanosilicate, and niobic acid. A gaseous mixture of DCPD (11.8 vol%) and H2O (88.2 vol%) was fed to the catalyst bed by using N2 as a carrier gas at a contact time of W/F = 5.9 g h mol1. Among the catalysts, niobic acid heat-treated at 300 8C exhibited the highest catalytic activity. The optimal reaction temperature over niobic acid was 170 8C, which is close to the decomposition temperature of DCPD. However, the catalysts deactivated quickly during the gas phase reaction. The data collected in first 30 min of time-on-stream were used for comparison. Even so, the highest conversion was 17%, and the conversion was extremely sensitive to the reaction temperature. Therefore, solid acid catalysts of high activities are still necessary to be developed for DCPD hydration.
http://dx.doi.org/10.1016/j.jiec.2016.08.013 1226-086X/ß 2016 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.
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Since the discovery of M41S mesoporous silica by the Mobil oil company in 1992 [7], the mesoporous materials with large surface area and pore volume, and narrowly distributed and tunable pore diameters of 2–10 nm have received great attention for their potential applications in adsorption [8,9], catalysis [10–12], and electron-optical devices. Among the mesoporous silica materials, SBA-15 of 2D-hexagonal p6mm pore structure is particularly desirable because of its relatively large pore diameters and higher hydrothermal stability in comparison with MCM-41, its analogue in the M41S family [13]. Functionalities have been introduced onto mesoporous silica materials in order to extend their applications. For example, Ti incorporated MCM-41 and SBA-15 are effective catalysts in epoxidation of large olefin molecules, hydroxylation of aromatic compounds, and photocatalytic degradation of phenol [14,12,15–21]. It is also reported that the Ti-SBA-15 catalyst is more stable under the reaction conditions during the epoxidation than the Ti-MCM-41 catalyst [22,23]. Organic functional groups have also been incorporated onto the mesoporous silica materials by either grafting or co-condensation methods [24–26]. The cocondensation method is often preferred to the post-grafting pathway because it minimizes processing steps and provides a more uniform distribution of the organic functionalities [27]. In addition, one-pot co-condensation synthesis often provides a higher loading of organic functionalities without closing the framework mesopores [28]. The purpose of this study is to develop a solid acid which can take the place of mineral acids in catalyzing DCPC hydration. In consideration of the sizes of reactant and product molecules, SBA15 materials of relatively large pores functionalized with propyland aryl-sulfonic acid groups were studied. The functionalized SBA15 were prepared by one-pot co-condensation and used to catalyze the hydration of DCPD. The optimal conditions in terms of reactant ratio, operation temperature, catalyst weight and solvent were investigated in order to obtain high DCPD-OH yield and selectivity. Experimental Chemicals and reagents All the chemicals were used as received without purification. DCPD was provided by National Chung-Shan Institute of Science and Technology, Taiwan. The composition and purity of DCPD were analyzed by a Perkin Elmer gas chromatograph with mass detector (Clarus 600 GC/MS). Preparation of catalysts Two kinds of sulfonic acid functionalized SBA-15 materials were examined for their catalytic performance in DCPD hydration. Their structures are shown in Scheme 1. The propylsulfonic acidfunctionalized SBA-15 materials with short-channeling pores were synthesized by co-condensation of TEOS and MPTMS in the conventional SBA-15 synthesis solution with the addition of an appropriate amount of Zr(IV) ions and H2O2[12]. In the optimal synthesis condition, 2.0 g of Pluronic P123 (Aldrich, Mn = 5800) and 0.32 g of zirconyl chloride octahydrate (ZrOCl28H2O, Acros) were dissolved in 80 g of 2.0 M HCl (Acros) solution at 35 8C. To this solution 4.2 g of TEOS (Acros) was introduced and hydrolyzed for 2 h, followed by the addition of MPTMS (Acros) and 0.9 g of 35 wt% H2O2 (Showa) aqueous solution. The molar composition of the reactants was 0.017 P123:1 TEOS:0.1 MPTMS:0.05 ZrOCl2:7.9 HCl:9 H2O2:220 H2O. The resulting mixtures were stirred at 40 8C for 20 h and then transferred into a polypropylene bottle and reacted at 90 8C under static condition for 24 h. The solid products were recovered by filtration, washing with ethanol, and dried at room temperature overnight. The P123 template was removed by
Scheme 1. Sulfonic acid-functionalized silica materials.
refluxing with ethanol. Finally, the materials were filtered, washed several times with water and ethanol, and dried at 100 8C. The sample is termed PrSA-SBA-15. Arylsulfonic acid-functionalized SBA-15 was prepared by onepot co-condensation of TEOS and (chlorosulfonylphenyl) ethyltrimethoxysilane (abbreviated CSPTMS, 50% in DCM) following the procedures similar to that mentioned in previous paragraph. The molar composition of the reactants was 0.017 P123:1TEOS:0.1CSPTMS:0.3 H2O2:5.8 HCl:165 H2O. The sample is termed ArSA-SBA-15. In order to examine the effect of ordered pores in silica materials on catalytic performance, propylsulfonic acid groups were anchored on two commercially available silica gels (Merk silica gel 60 and Alfa Aesar silica gel large pore) by grafting method. 2 g of the silica gel was refluxed in 100 mL toluene containing 2 g MPTMS (S/Si molar ratio of 0.3) for 24 h, followed by filtration, washing with ethanol, dried at 50 8C. The thiol groups were oxidized to sulfonic acid groups by mixing the dried powders in 50 mL 35% H2O2 and 3 drops of 18 M sulfuric acid at 35 8C under stirring for 8 h, followed by thoroughly washing till pH neutral. The solid products dried at 100 8C overnight are termed PrSA-Silica I and II, corresponding to Merk and Alfa silica sources, respectively. Characterization Powder X-ray diffraction (XRD) patterns were recorded using a PANalytical X’pert Pro diffractometer with Cu Ka radiation operated at 40 mA and 45 kV. N2 adsorption–desorption isotherms were measured using a Micromeritics Tristar 3000 system at liquid nitrogen temperature (77 K). Before the measurements, the samples were degassed at 473 K for 10 h under vacuum condition (103 Torr). The surface area was calculated by using Brunauer– Emmett–Teller (BET) method. Pore size was determined by Barrett–Joyner–Halenda (BJH) method using the desorption branch of the isotherms. The silica content was determined using thermogravimetric analysis by a Hi–Res TA 2950 analyzer under 60 mL/min air flow and 10 8C min1 ramping rate. The acid amounts in the materials were determined by ion-exchange with NaCl, followed by acid-base titration of the filtrate. In a typical experiment, 0.20 g of the solid was first dried at 50 8C for 1 day and then added to 40 mL 2 M NaCl solution. The suspension was mixed to reach equilibrium for 6 h, and then the solid was filtered and washed with a small amount of water. Finally, the filtrate was titrated by 0.01 M NaOH aqueous solution. Catalytic reaction Liquid phase hydration of DCPD was carried out in a twonecked round bottom flask connected with a reflux condenser and a thermometer. For the test reaction, 1.32 g (0.01 mol) of DCPD and
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5.4–16.2 g (0.3–0.9 mol) of water were mixed under vigorous stirring at 90 8C. 0.5–1 g of the solid acid catalyst was added to start the reaction, and the reaction was run for 8 h or longer. After cooling to room temperature, 10–30 g isopropanol were added, versus different water amounts, as the co-solvent to make sure homogeneous mixing of the products. In addition, 1.08 g (10 mmol) of o-xylene was added as the internal standard. The products were collected by filtering syringe and analyzed by a Shimadzu gas chromatograph (GC) 14B equipped with a RTX-1 capillary column (30 m in length, 0.35 mm in diameter) and a FID detector. The GC analysis condition was set as following: injection port 250 8C, detector port 280 8C, and column temperature from 60 to 280 8C with a ramping rate of 20 8C min1.
surface areas of 589 and 377 m2/g, pore diameters of 5.3 and 7.0 nm, and pore volumes of 0.75 and 0.67 cm3/g, respectively. On the other hand, the silica gel materials (PrSA-Silica I and II) from two commercial brands functionalized with propylsulfonic acid have surface areas of 145 and 393 m2/g, and pore volumes of 0.24 and 0.53 cm3/g, respectively. Moreover, the acid capacities determined by NaOH titration of the filtrates of NaCl-exchanged solids are almost proportional to the surface areas (Table 1). Thus, PrSA-SBA-15 has the highest acid capacity of 0.83 mmol/g, while PrSA-Silica I has the lowest acid capacity of 0.30 mmol/g. Because relatively large weight and volume of PrSA-Silica I is needed to achieve the same acid amount as other three catalysts, this sample is abandoned from further catalytic tests.
Results and discussion
Reactant and product analysis by GC
Catalyst characterization
Because the target product DCPD-OH was not commercially available, it was prepared according to the procedure reported in Ref. [3] by hydration of 25 g DCPD using 75 g 40% H2SO4 as the catalyst at 60 8C for 2 h. The products were a mixture of two immiscible phases in dark brown color, indicating a large amount of polymeric species or coke was formed under such a strong acidic condition. After separating the aqueous phase by a separation funnel, the organic products were extracted with nhexane, followed by solvent evaporation with a rotor-evaporator. The purified DCPD-OH was identified by 1H and 13C NMR spectroscopy and used for making the calibration curve of GC analysis. The DCPD-OH product appeared at GC as a single peak at 5.48 min, as shown in Fig. 2(A). However, the 1H and 13C NMR spectra showed that it was a mixture of mono alcohols resulting from hydration at the six-ring site of DCPD, as shown in Scheme 2. Other than DCPD-OH, GC showed two minor products appeared at about twice of the retention time (10.38 and 10.48 min) of that of DCPD-OH in the organic phase. The masses of these two GC peaks identified by MS analysis to be 282 (Fig. 2(B)), and these minor products were likely the ether product formed by condensation of two DCPD-OH molecules. Using 40% H2SO4 as the catalyst, the area ratio of DCPD-OH/ether was about 65/35. This result implies that dehydration of DCPD-OH can occur in the presence of strong mineral acids.
Small-angle XRD patterns of prepared sulfonic acid functionalized silica materials are shown in Fig. 1(A). Both PrSA-SBA-15 and ArSA-SBA-15 samples show three well-resolved diffraction peaks corresponding to the (100), (110) and (200) planes of 2Dhexagonal p6mm pore structure, and the patterns are akin to that of conventional SBA-15 material [13]. In contrast, the functionalized silica gels have no diffractions in this region. Nitrogen adsorption–desorption isotherms of these materials are shown in Fig. 1(B). PrSA-SBA-15 and ArSA-SBA-15 samples have the characteristic type IV isotherms with H1 hysteresis loop appears at P/P0 of 0.6–0.8, indicating that large mesopores with narrow PSDs are present, akin to the conventional SBA-15 material [13]. On the other hand, one of the silica gel samples, PrSA-Silica I, has no apparent N2 adsorption until P/P0 0.9, probably attributing to the inter-particle voids. The other silica gel sample PrSASilica II also gives type IV isotherm. However, the hysteresis covers a relatively wider range of partial pressure, implying a wide pore size distribution. The BJH pore size distributions shown in Fig. 1(C) confirm these results. The physicochemical properties of these sulfonic acid functionalized silica materials are shown in Table 1. The SBA-15 materials functionalized with propyl- and aryl-sulfonic acid groups have
(B)
(A)
0.16
(C)
2000 0.14
N2 Adsorbed (cm g STP)
1600
(c)
0.12
(0,1461)
(b)
0.88°
-1
(c)
3
1200
1.38° 1.57°
(0,1042) 800
1.69°
0.02
(a) (0,0)
0
1
2
3
2 theta
4
(b)
0.04
(0,547)
(a)
(a)
0.08 0.06
(b)
400 1.46°
(c)
0.10
3
-1
0.83°
(d)
(d)
dv /d (cm g STP)
Intensity (Arbitary unit)
(d)
5
6
0.00
0 0.0 0.2 0.4 0.6 0.8 1.0 1.2
P/P0
2
4
6
8
10
PSD (nm)
Fig. 1. (A) Powder X-ray diffraction patterns, (B) N2 adsorption–desorption isotherms, and (C) BJH pore-size distributions of (a) PrSA-SBA-15, (b) ArSA-SBA-15, (c) PrSA-Silica I, and (d) PrSA-Silica II.
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Table 1 Physicochemical properties of sulfonic acid-functionalized silica materials. Sample
Surface areaa (m2/g)
Pore volume (cm3/g)
Pore diameterb (nm)
Acid capacityc (H+ mmol/g)
PrSA-SBA-15 ArSA-SBA-15 PrSA-Silica I PrSA-Silica II
590 377 145 393
0.75 0.67 0.24 0.54
5.9 7.5 – 5.1
0.83 0.60 0.30 0.52
a b c
Determined by BET method. Determined from the peak position of BJH PSD profiles using the desorption branches of the isotherms. Determined by NaOH titration on the filtrate of NaCl(aq) exchanged samples.
One of the difficulties encountered in olefins hydration is the immiscibility of olefins and water [29,30]. In order to obtain a homogeneous solution of the products for GC analysis, a co-solvent was added to the products. After testing with several solvents, it was found that iso-propanol (IPA) was the best co-solvent. Moreover, IPA of about twice weight of water was needed to achieve homogeneous mixing of all components in the products. The injection port temperature of GC was found to be important for products analysis. On one hand, DCPD was considered to
undergo reverse Diels–Alder reaction to form two CPD molecules at temperatures above 180 8C. On the other hand, the boiling temperature of DCPD-OH is as high as 246 8C. In order to achieve complete evaporation of the product without decomposition of the reactant, the temperature of injection port was varied from 150 to 250 8C. Since no CPD peak was detected even the injection port was raised to 250 8C, it was chosen for the followed analysis. During the process of making calibration curves of DCPD and DCPD-OH using o-xylene as the internal standard, it was noticed
Fig. 2. GC–MS analysis of products formed in DCPD hydration using H2SO4 catalyst: (A) GC profile, (B) mass spectra of GC peaks at retention time (a) 10.47 min, (b) 10.38 min, (c) 5.48 min.
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Table 3 Effect of H2O/DCDP molar ratio on DCPD hydration. H2O/DCPD Molar ratio
30 60 90 30|
Scheme 2. Hydration and polymerization of DCPD in the presence of acid catalysts.
that the slopes of calibration curves changed with the amount of water and IPA added. Therefore, the product analysis was based on the calibration curves made with the mixtures containing water and IPA as those needed for optimal DCPD-OH yield and product dissolution, respectively. The weight ratios for calibration curve of DCPD were DCPD:o-xylene:H2O:IPA = 0.26–1.33:1.06:10.8:20, and those for calibration curve of DCPD-OH were DCPD-OH:oxylene:H2O:IPA = 0.068–0.619:1.06:10.8:20. Catalytic results without co-solvents Sulfonic acid functionalized SBA-15 and silica gel materials are used as the catalysts in DCPD hydration at 90 8C, and the results after 8 h are shown in Table 2. Entries 1–3 compare the catalytic performances of different functionalized silica materials based on the same acid amounts of 0.3 mmol H+ and H2O/DCPD molar ratio kept at 30. The highest DCPD conversion is obtained on SBA-15 functionalized with arylsulfonic acid, while propylsulfonic acid functionalized silica gel gives the lowest DCPD conversion. The result is attributed to the stronger acidic strength of arylsulfonic acid than propylsulfonic acid [30]. However, ArSA-SBA-15 catalyst also gives the lowest yield and selectivity of DCPD-OH. It is noticed that relative larger amount of brown polymeric species or coke are formed over ArSA-SBA-15. These results indicate that DCPD polymerization is likely favored to hydration over ArSA-SBA-15 catalyst. In comparison, propylsulfonic acid functionalized materials of relatively weaker acidic strength are favored catalysts in DCPD hydration. Although PrSA-Silica II and PrSA-SBA-15 have similar catalytic performances, the latter gives slightly higher DCPD conversion and DCPD-OH yield. It is attributed to the well dispersed acidic sites on SBA-15 can provide better accessibility of the reactants and more effectively catalyze the hydration. Moreover, the markedly different acid capacities for functionalized silica gels obtained from different brands demonstrate the difficulties in material control. Therefore, only the catalytic performance of PrSA-SBA-15 is studied hereafter. Entries 2, 4 and 5 in Table 2 show the effect of catalyst weight. Both DCPD conversion and DCPD-OH yield increase with the increase of catalyst weight. It is however surprised to see that the DCPD-OH selectivity dramatically increases when the catalyst
Table 2 Catalytic performance of SBA-15 and silica gel functionalized with sulfonic acid groups in DCPD hydration. Entry Catalyst
ArSA-SBA-15 PrSA-SBA-15 PrSA-Silica II PrSA-SBA-15 PrSA-SBA-15
0.5 0.38 0.58 0.5 1
16.1 10.8 9.4 12.4 16.2
4.6 5.1 4.9 6.0 14.8
DCPD Conv.
DCPD-OH
(g)
(mol)
(%)
Yield (%)
Select. (%)
5.4 10.8 16.2 5.4
0.3 0.6 0.9 0.3
16.2 12.9 10.7 12.2
14.8 10.0 8.4 4.9
91.6 80.1 78.2 40.3
Reaction condition: 1 g PrSA-SBA-15 catalyst, DCPD 1.32 g (0.01 mol), 90 8C, 8 h. | Using 0.001 mol H2SO4(aq) as the homogeneous catalyst.
weight is increased from 0.5 to 1 g. It is also noticed that the colors of used catalysts are different. The color is in deeper brown for the 0.5 g catalyst than 1 g catalyst, indicating that more polymeric species are formed when less amount of catalyst is used. One of possible explanations is that polymerization of DCPD proceeds in a relatively faster rate than DCPD hydration. When a larger quantity of PrSA-SBA-15 catalyst is present, the rate of DCPD hydration increases and less amount of DCPD is left for polymerization. Table 3 shows the results of the catalytic reaction at 90 8C after 8 h with different H2O/DCDP ratios using PrSA-SBA-15 as the catalyst. It can be seen that DCPD conversion and DCPD-OH yield decrease with the increase of H2O/DCDP ratio. The highest DCPD conversion of 16.2% and DCPD-OH yield of 14.8% were obtained when H2O/DCDP molar ratio was 30. It is also noticeable that the DCPD-OH selectivities are quite high over PrSA-SBA-15 catalyst. In the optimal condition, the selectivity can reach up to ca. 92%. In contrast, the DCPD-OH selectivity is only ca. 40% using aqueous H2SO4 of the same acid amount as that of PrSA-SBA-15 as a homogeneous catalyst (entry |). Again, the side products are polymeric species or coke since some precipitates of deep brown color are obtained in the homogeneous catalytic system. The polymeric products are apparently less over the solid catalysts since only the surface of solid turns brown after the reaction. These results demonstrate that PrSA-SBA-15 is favorable to sulfuric acid in giving higher yield and selectivity of DCPA-OH. The results also indicate that excess amount of water may dilute the concentration of DCPD and reduce the rate of DCPD hydration. Accordingly, less amount of water should be used to achieve higher DCPD conversion and DCPD-OH yield. Nevertheless, 5 g of water is almost the minimum amount to have 1 g of PrSA-SBA-15 powders completely immersed. The results of varying the reaction period are shown in Table 4. Notice that H2O/DCPD molar ratio is kept at 60. The DCPD conversion and DCPD-OH yield increase as the reaction period increases. However, the DCPD-OH selectivity decreases from ca. 80–82% to 71% when the reaction is prolonged to 24 h at 90 8C, indicating that more polymerization products are formed after long reaction period. The effect of reaction temperature is shown in Table 5. The DCPD conversion and DCPD-OH yield increase with reaction temperature. However, optimal selectivity is obtained at 90 8C. It was also noticed that the color of the used catalyst turned deeper brown color with the increase of temperature. These results imply that more polymeric species are formed at higher temperatures. Table 4 Effect of reaction period on DCPD hydration.
Wt. of Catal. (g) DCPD Conv. (%) DCPD-OH Yield (%) Select. (%)
1 2 3 4 5
H2O
28.7 47.0 51.8 48.2 91.6
Reaction condition: DCPD 1.32 g (0.01 mol), H2O 5.4 g (0.3 mol), 90 8C, 8 h.
Reaction period (h)
DCPD Conv. (%)
8 14.5 24
12.9 17.5 28.2
DCPD-OH Yield (%)
Select. (%)
10.0 14.4 20.1
80.1 82.4 71.3
Reaction condition: 1 g catalyst, DCPD 1.32 g (0.01 mol), H2O 10.8 g (0.6 mol), 90 8C.
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Table 5 Effect of reaction temperature on DCPD hydration. Temperature (8C)
DCPD Conv. (%)
70 90 100–110 (reflux)
8.3 16.2 33.3
Table 6 Effect of co-solvents on DCPD hydration. DCPD-OH Yield (%)
Select. (%)
5.1 14.8 26.4
61.3 91.6 79.1
Reaction condition: 1 g catalyst, DCPD 1.32 g (0.01 mol), H2O 5.4 g (0.3 mol), 8 h.
Co-solvent/ b.p. (8C)
IPA/82.6 – THF/66
Wt. of co-solvent (g)
5 0 6.5
H2O
DCPD Conv. (%)
Wt. (g)
Mole
2.0 5.4 0.5
0.11 0.3 0.03
6.6 12.4 7.0
DCPD-OH Yield (%)
Select. (%)
4.7 6.0 Trace
73.0 48.2 Trace
Reaction condition: 0.5 g PrSA-SBA-15 catalyst, DCPD 1.32 g (0.01 mol), reflux temperature, 8 h.
In consideration that DCPD hydration and polymerization are two parallel reactions catalyzed by the acid, as shown in Scheme 2, the activation energies of these two reactions can be estimated from the yield rates of DCPD-OH and polymeric species obtained in Table 5 as a function of temperature. Assuming that both reactions are pseudo first order, the Arrhenius plots are obtained and shown in Fig. 3. The activation energy of DCPD hydration is estimated to be 6.13 kJ/mol, while that of polymerization is 2.84 kJ/mol over PrSA-SBA-15 catalyst. The relatively low activation energy of polymerization explains the experimental observation that polymeric species are easily formed in strong acid or when insufficient amount of acid catalyst is present.
Table 7 Reusability of the PrSA-SBA-15 catalyst in DCPD hydration. Run
DCPD Conv. (%)
1 2 3 4 5
16.2 12.1 11.4 10.2 10.8
DCPD-OH Yield (%)
Select. (%)
14.8 7.1 6.0 5.2 4.1
91.6 58.3 52.2 51.3 38.2
Reaction condition: 1 g catalyst, DCPD 1.32 g (0.01 mol), H2O 5.4 g (0.3 mol), 90 8C, 8 h.
Catalytic results with co-solvents Recycling of the SA-SBA-15 catalyst Co-solvents are added in order to have reactants in a miscible liquid phase. Meanwhile, the amount of water can be reduced. However, there are not too many choices of co-solvents in consideration of low boiling point and minimum volume needed. It turns out that two of the most suitable co-solvents are IPA and THF. Table 6 lists the minimum amounts of IPA and THF used to achieve miscible phases of 0.01 mol of DCDP and water. The H2O/DCPD molar ratio can be reduced to 11 with 5 g IPA, while that can be further decreased to 3 with 6.5 g THF. The catalytic results show that DCPD conversions and DCPD yields are lower in the presence of co-solvents. However, higher DCPD-OH selectivity is obtained in IPA than that without cosolvent. In contrast, only trace amount of DCPD-OH is detected in THF, probably due to the relatively low boiling point. Although addition of IPA as co-solvent can ensure the miscibility of DCPD and water, additional evaporation process is necessary for products separation and purification.
The used PrSA-SBA-15 catalyst is easily recycled and regenerated. The solid catalyst collected by filtration was regenerated by heating in a mixture of 250 mL IPA and 15 mL 2 M HCl at 50 8C overnight, filtering again, washing with IPA and ethanol, then drying at 50 8C. The performances of the regenerated catalysts in DCPD hydration up to 4 times of recycling are compared with that of fresh one in Table 7. The DCPD conversion decreases to about three quarters of that of fresh catalyst in the first recycle, while the DCPD-OH yield decreases to about a half of the fresh one. That is attributed to that polymeric species coating on the outer surfaces of the catalyst cannot be thoroughly removed by heating treatment in alcohols. Nevertheless, the decreases in DCPD conversion and DCPD-OH yield become less significant when recycling number increases. Although the catalytic activity of the regenerated SBA15 catalyst cannot be completely recovered due to partially foiling of the active sites by polymeric products, the easy separation of the solid acid catalyst from the products still offers the advantage of avoiding in further polymerization of unreacted DCPD during products separation by distillation. Conclusions
Fig. 3. Arrhenius plots of (A) DCPD-OH hydration and (B) polymerization over PrSASBA-15 catalyst.
Propylsulfonic acid-functionalized SBA-15 material with ordered channeling pores and acid capacities around 1 mmol H+g1 is an efficient catalyst in the hydration of dicyclopentadiene. However, polymerization of DCPD is a parallel side reaction of lower activation energy. Aryl-SA-SBA-15 which has stronger acidic strength is less favorable to Propyl-SA-SBA-15 as the catalyst, giving more polymeric products and lower yield and selectivity of DCPD-OH. PrSA-SBA-15 catalyst is also favorable to sulfuric acid in giving higher yield and selectivity of DCPA-OH. Although adding IPA as the co-solvent can ensure the miscibility of DCPD and water, additional evaporation process is necessary for products separation and purification. Relatively high DCPD conversion and DCPDOH yield can be achieved without co-solvents, and these values increase with the decrease in H2O/DCPD ratio. The optimal DCPD conversion and DCPD-OH selectivity are obtained over Propyl-SASBA-15 at 90–100 8C with the molar composition of DCPD:H2O:H+catalyst = 1:30:0.1. The DCPD conversion of 16.2% and DCPD-OH
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selectivity of 91.6% in 8 h are much higher than those reported by Talwalkar et al. [5] using Amberlyst-15 resin catalyst (ca. 4% DCPD conversion and <35% DCPD-OH selectivity) at the same temperature of 90 8C. The easy separation of the solid acid catalyst from the products offers the advantage of avoiding in further polymerization of unreacted DCPD during products separation by distillation. Acknowledgment Financial support from the National Chung-Shan Institute of Science and Technology, Taiwan (CSIST-1246-V204 (104)) is gratefully acknowledged. References [1] D. Ho¨nicke, R. Fo¨disch, P. Claus, M. Olson, Ullmann’s Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2002. [2] R.B. Moffett, Org. Synth. Coll. 4 (1962) 238. [3] H.A. Bruson, T.W. Riener, J. Am. Chem. Soc. 67 (1945) 723. [4] H. Kasei, Jpn. Patent Kokai 55-19205, 56-59723. [5] S. Talwalkar, P. Kumbhar, S. Mahajani, Catal. Commun. 7 (2006) 717. [6] S. Okazaki, H. Harada, Chem. Lett. 17 (1988) 1313. [7] C.T. Kresge, M.E. Leonowicz, W.J. Roth, J.C. Vartuli, J.S. Beck, Nature 359 (1992) 710. [8] X. Fang, G.E. Frywell, L.Q. Wang, A.Y. Kim, J. Liu, K.M. Kemner, Science 276 (2007) 923.
7
[9] J.M. Sun, H. Zhang, R.J. Tian, D. Ma, X.H. Bao, D.S. Su, H.F. Zou, Chem. Commun. (2006) 1322. [10] A. Corma, Chem. Rev. 97 (1997) 237. [11] S.Y. Chen, J.F. Lee, S. Cheng, J. Catal. 270 (2010) 196. [12] S.Y. Chen, C.Y. Tang, J.F. Lee, L.Y. Jang, T. Tatsumi, S. Cheng, J. Mater. Chem. 21 (2011) 2255. [13] D. Zhao, J. Feng, Q. Huo, N. Melosh, G.H. Fredrickson, B.F. Chmelka, G.D. Stucky, Science 279 (1998) 548. [14] F. Berube, B. Nohair, F. Kleitz, S. Kaliaguine, Chem. Mater. 22 (2010) 1988. [15] A. Wro´blewska, E. Makuch, E. Sokalska, M. Malko, React. Kinet. Mech. Catal. 113 (2014) 519. [16] A. Wro´blewska, Molecules 19 (2014) 19907. [17] A. Wro´blewska, A. Fajdek, J. Wajzberg, E. Milchert, J. Hazard. Mater. 170 (2009), 405–410 A. [18] A. Wro´blewska, E. Makuch, React. Kinet. Mech. Catal. 105 (2012) 451. [19] K. Kulawik, G. Schulz-Ekloff, J. Rathousky´, A. Zukal, J. Had, Collect. Czech. Chem. Commun. 60 (1995) 451. [20] G.D. Lee, S.G. Kim, H.H. Jeong, S.S. Park, S.S. Hong, Solid State Phenom. 124–126 (2007) 1793. [21] L. Yang, Z. Jiang, S. Lai, Ch. Jiang, H. Zhong, Int. J. Chem. Eng. (2014), Article ID 691562, 7 pp.. [22] A. Wro´blewska, E. Makuch, Pol. J. Chem. Technol. 4 (15) (2013) 111. [23] A. Wro´blewska, E. Makuch, J. Adv. Oxid. Technol. 17 (1) (2014) 44. [24] S.-Y. Chen, T. Yokoi, C.-Y. Tang, L.-Y. Jang, T. Tatsumi, J.C.C. Chan, S. Cheng, Green Chem. 13 (2011) 2920. [25] X. Wang, K.S.K. Lin, J.C.C. Chan, S. Cheng, J. Phys. Chem. B 109 (2005) 1763. [26] S. Cheng, X. Wang, S.-Y. Chen, Top. Catal. 52 (2009) 681. [27] A. Walcarius, C. Delacote, Chem. Mater. 15 (2003) 4181. [28] D.J. Macquarrie, D.B. Jackson, Chem. Commun. (1997) 1781. [29] T. Nakato, Y. Toyoshi, M. Kimura, T. Okuhara, Catal. Today 52 (1999) 23. [30] C.-C. Chen, S. Cheng, L.-Y. Jang, Microporous Mesoporous Mater. 109 (2008) 258.
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