Development of MeSAPO-5 Molecular Sieves from Attapulgite for

Jan 22, 2015 - The results indicated that MeSAPO-5 catalyst with Si/Al ratio of 0.25 provided much more acid active sites for feasible accessibility o...
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Development of MeSAPO‑5 Molecular Sieves from Attapulgite for Dehydration of Carbohydrates Hui Shao,* Jingjing Chen, Jing Zhong, Yixin Leng, and Jun Wang Jiangsu Key Laboratory of Advanced Catalytic Materials and Technology, School of Petrochemical Engineering, Changzhou University, Changzhou 213164, China ABSTRACT: The dehydration of carbohydrates to 5-hydroxymethylfurfural (HMF) is still a major challenge in the bioenergy industry. In this study, metal-containing silicoaluminophosphate molecular sieves (MeSAPO-5) with different Si/Al ratios were first synthesized from attapulgite by the hydrothermal method and applied to the dehydration of carbohydrate. The morphology, structure, and acid properties of MeSAPO-5 molecular sieves were studied by XRD, SEM, EDX, TG/DTA, pyrolysis IR (Py-IR), and NH3-TPD. The results indicated that MeSAPO-5 catalyst with Si/Al ratio of 0.25 provided much more acid active sites for feasible accessibility of HMF, after partial Al atoms were substituted by Si and Me atoms. The further increase of Si/Al ratio resulted in the decrease of the acidity of the molecular sieves, which significantly influenced their catalytic performance. Over the MeSAPO-5(0.25Si) catalyst, the HMF yield of 73.9% was obtained at 170 °C with 2.0 h. This indicated that MeSAPO-5 molecular sieves were a fairly promising catalyst for the carbohydrates dehydration to HMF. essential to find efficient and economical heterogeneous acids that can be used as catalysts for the conversion of carbohydrates into HMF. Among various heterogeneous catalysts, metal-containing silicoaluminophosphate molecular sieves (MeSAPOs) have attracted extensive attention due to their modifiable acid sites, large surface areas, and great thermostability.18−20 The common method to prepare MeSAPOs is by using conventional chemicals. Although the technology is maturely established and the products are high quality, the cost of the chemicals (containing individual Si and Al) continues to rise with the increased demand for highly active materials. The high production cost limits the real applications of MeSAPOs in industrial production. Up until now, several efforts have been made to synthesize SAPOs from natural minerals to reduce the cost. Many types of SAPOs, such as SAPO-5, SAPO-11, SAPO44,21 SAPO-34,22 have been hydrothermally synthesized using kaolin as the single Si and partial Al source. However, the commercial kaolin is processed to remove metal, which could be a metal source for the framework. Salmasi20 reported that the introduction of transition metal elements into SAPO-34 molecular sieve could improve its catalytic performance due to the acid site modification by Ni and Mg. Therefore, it is promising to prepare low-cost MeSAPOs using transition elements derived from natural minerals. In this work, we first used attapulgite ore containing transition metals as a cheap and abundant mineral source to synthesize MeSAPO-5 molecular sieves (Me = Fe, Mg) by hydrothermal method. The treated attapulgite provided the source for single Si, single Me, and partial Al. The crystal structure, morphology, and acidity of synthesized MeSAPO-5

1. INTRODUCTION The use of biomass resources has attracted significant attention in recent years for reducing our dependence on petroleum sources and the CO2 level in the atmosphere.1,2 However, most of the available biomass is used directly for liquid fuels (e.g., ethanol). Only a small fraction has been used to generate higher-value products.3 Thus, a lot of efforts have been made in producing chemicals from biomass. Among numerous biomassderived chemicals, 5-hydroxymethylfurfural (HMF) has attracted attention as a widely used intermediate and fuel alternative.4 HMF has been synthesized by acid-catalyzed dehydration of carbohydrates and its production has been used to evaluate the efficiency of catalysts and choose proper reaction solvent systems.5,6 In the past few years, the conversion of carbohydrates into HMF has been carried out in monophasic system (water, organic solvents, and ionic liquids) and biphasic system (water−organic mixed solvents) in the presence of various catalysts. Early on, inorganic acids7 and organic acids8 had been employed as homogeneous catalysts. However, homogeneous acid catalysts have serious problems relating to the separation of products, recycling of solvents as well as the corrosion of equipment. In addition, the literature9 revealed that the dehydration of fructose in water−organic solvents could substantially further increase the HMF yield and minimize secondary reaction. Therefore, the use of heterogeneous acid catalysts was proposed. Some heterogeneous acid catalysts have been reported, such as ion exchange resins,10 oxides,11,12 and H-form zeolites.13,14 Nevertheless, the oxides and H-form zeolites still suffered from low yield of HMF. Although ion exchange resins had effective catalysis performance, they were limited to temperatures below 130 °C due to the thermal stability of the resins.4 Recently, ionic liquids15,16 were used due to their excellent performance with dissolving cellulose. Whereas, the high cost of ionic liquids restricts the application. In addition, the solubility of sugar in ionic liquids is relatively low compared to its solubility in water. This limits the extent of feedstock concentration.17 Consequently, it is © 2015 American Chemical Society

Received: Revised: Accepted: Published: 1470

October 27, 2014 January 15, 2015 January 22, 2015 January 22, 2015 DOI: 10.1021/ie504243t Ind. Eng. Chem. Res. 2015, 54, 1470−1477

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Industrial & Engineering Chemistry Research

with 0.1 g of MeSAPO-5 in a mixture of 40 g of aqueous and organic solvents (1:3 (g:g)). The reaction was carried out in a 100 mL round-bottomed flask under N2. The aqueous phase contained 4:6 (g:g) water and dimethyl sulfoxide (DMSO). The organic phase had 7:3 (g:g) methyl isobutyl ketone (MIBK) and 2-butyl alcohol (SBA). An oil bath was used to heat the reaction mixture to the reaction temperature (170 °C) with magnetic stirring. After the reaction finished, aqueous and organic phase were analyzed by HPLC using a C-18 column (Agilent) and UV-detector. A mixture of 7:3 (v:v) methanol:water was used as the mobile phase at a flow rate of 0.8 mL min−1. The yield of HMF was calculated by n + n2 η= 1 × 100% n0

were studied. The catalytic performance of MeSAPO-5 molecular sieves with different Si/Al ratios was investigated in the dehydration of carbohydrates such as fructose, glucose, and sucrose in a biphasic system to examine the possibility of using MeSAPO-5 catalysts to prepare HMF.

2. EXPERIMENTAL SECTION 2.1. Materials. The natural attapulgite ore (Jiangsu Nanda Zijin Technology Group Co., Ltd., China) was ground down into powder and then treated with sedimentation and acidification. Pseudoboehmite (71 wt % Al2O3, Shandong Aluminum Co. Ltd., China) was used as the additional Al source. Orthophosphoric acid (85 wt %, Sinopharm Chemical Reagent Co.Ltd., China) was used as the phosphorus source. Triethylamine (TEA, Sinopharm Chemical Reagent Co., Ltd., China) was used as the template. 2.2. Synthesis of MeSAPO-5. MeSAPO-5 was prepared by hydrothermal method according to preparation process shown in Figure 1. Typically, treated attpulgite (ATP, 60.0 wt % SiO2,

where n1 is the moles of HMF produced in aqueous phase; n2 is the moles of HMF produced in organic phase; n0 is moles of the starting fructose, glucose, or sucrose.

3. RESULTS AND DISCUSSION 3.1. Characterization. The XRD patterns of MeSAPO-5 molecular sieves with different Si/Al ratios are shown in Figure 2. An AFI structure (i.e., 2θ = 7.8°, 12.8°, 14.8°, 21.0°, 22.3°,

Figure 1. Synthetic process of MeSAPO-5 catalysts for dehydration of fructose to HMF.

10.1 wt % Al2O3, 6.4 wt % MgO, 4.8 wt % Fe2O3) was mixed with pseudoboehmite and deionized water for 20 h to form slurry. Then, phosphoric acid and triethylamine were added into the slurry. After aging for 12 h at room temperature, the slurry was sealed into a Teflon-lined reactor and maintained at 180 °C for 24 h. The MeSAPO-5 samples with different Si/Al ratios were synthesized. The raw slurry composition was 1.0Al:1.0P:xSi:0.5TEA:yMg:zFe:50H2O (x = 0.10, 0.25, 0.50, 0.75, 1.00), where y = 0.016, 0.04, 0.08, 0.12, 0.16 and z = 0.006, 0.015, 0.030, 0.045, 0.60 associated with the Si content of ATP. 2.3. Characterization. X-ray diffraction (XRD) experiments were obtained on a Rigaku D/max2500 instrument with Cu Kα radiation (40 kV, 100 mA). Scanning electron microscopy (SEM) images were collected on JSM-6360LA (JEOL) microscope at 15 kV. The chemical compositions for MeSAPO-5 were analyzed by energy dispersive X-ray spectrometry (EDX). Thermal analytical measurement was performed on the sample by means of a TG/DTA Instruments (SDTQ600,TA) under air atmosphere by imposing a heating rate of 5 °C·min−1. The Bro̷ nsted acid and Lewis acid sites of the samples were determined on TENSOR27 FT-IR spectrometer (Bruker). The temperature-programmed desorption of NH3 (NH3-TPD) from the samples were performed on a TPRWin adsorption (Quantachorme) and a Thermo Star MSD (Thermo Electron). 2.4. Dehydration of Carbohydrates to HMF. In a typical reaction protocol, 1 g of fructose, glucose, or sucrose was mixed

Figure 2. XRD pattern of MeSAPO-5 molecular sieves with different Si/Al ratios.

25.8°) was indicated for all samples,23 confirming the formation of MeSAPO-5 molecular sieves. The characteristic peak of MeSAPO-5 increased with the increase of Si content from 0.10 to 0.25. The initial addition of attapulgite led to higher crystallinity of MeSAPO-5, demonstrating that the addition of Si into the raw mixture could reduce activation energy of the formation of MeSAPO-5.24 However, the intensities of MeSAPO-5 gradually decreased with additional increase of attapulgite content. With further increasing Si content, a certain amount of attapulgite was found, according to the typical peaks at about 8.3° and 20.0°. In synthesis processes, the overmuch unreacted ATP split MeSAPO-5 molecular sieve, issuing in the shrinkage of crystal cell. This process was proved by the peak shift of MeSAPO-5 (1.00Si). These results demonstrated that excessive increase of Si atoms in the synthesis gel would destroy the crystal structure of MeSAPO-5. The SEM picture of the MeSAPO-5(0.10Si) molecular sieve showed that the sample had hexagonal columnar shape particles 1471

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Figure 3. SEM images of MeSAPO-5 molecular sieves with different Si/Al ratio of (a) 0.10, (b) 0.25, (c) 0.50, (d) 0.75, and (e) 1.00.

Table 1. Gel and Crystal Compositions for MeSAPO-5 Samples Si/Al ratio

Mg/Al ratio

Fe/Al ratio

sample

gel mole ratio (Al2O3:P2O5: SiO2:MgO:FeO)

crystal compositiona

gel

crystal

gel

crystal

gel

crystal

MeSAPO-5(0.10Si) MeSAPO-5(0.25Si) MeSAPO-5(0.50Si) MeSAPO-5(0.75Si) MeSAPO-5(1.00Si)

1.0:1.0:0.20:0.032:0.012 1.0:1.0:0.50:0.08:0.03 1.0:1.0:1.00:0.16:0.06 1.0:1.0:1.50:0.24:0.09 1.0:1.0:2.00:0.32:0.12

(Al6.55P6.39Si0.64Mg0.20Fe0.07)O2 (Al5.89P5.40Si1.44Mg0.47Fe0.18)O2 (Al5.42P4.99Si2.68Mg0.85Fe0.30)O2 (Al5.07P4.35Si3.55Mg1.12Fe0.40)O2 (Al3.63P3.69Si4.52Mg1.33Fe0.50)O2

0.100 0.250 0.500 0.750 1.000

0.098 0.245 0.494 0.700 1.245

0.016 0.040 0.080 0.120 0.160

0.015 0.039 0.079 0.110 0.199

0.006 0.015 0.030 0.045 0.060

0.006 0.015 0.028 0.039 0.069

a

Analyzed by EDX.

with size of 2 × 12 μm (Figure 3a). As the amount of attapulgite increased, the particles started becoming a quadrilateral columnar shape with a dimension of 5 × 20 μm in 0.25Si. With further increase of the Si content, the quadrilateral columnar unit cell of MeSAPO-5 ruptured, as shown in Figure 3c. In the 0.75Si sample, pillar-like crystals could be seen. The presence of some small fibrous particles in 0.75Si sample,

together with the XRD peaks indicated that there was some unreacted ATP. As seen in Figure 3e, the morphology of MeSAPO-5 with 1.00Si was quite different from that of other MeSAPO-5 samples. The irregular crystals of molecular sieves were observed among the fibrous ATP particles. This was attributed to the presence of excess ATP. 1472

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Industrial & Engineering Chemistry Research The compositions of the starting gel and the calcined MeSAPO-5 powders, as measured by EDX, are shown in Table 1. It can be observed that the chemical compositions for MeSAPO-5(0.10Si), (0.25Si), and (0.50Si) samples were similar to the synthesis gel composition. The result indicated Si, Mg, and Fe ions of attapulgite had been incorporated into the framework. With further increased the Si/Al ratio to 0.75, the concentrations of Si, Mg, and Fe were lower for the crystal rather than in the gel. This revealed the incomplete substitution of excess Si and Me atoms, led to SiO and MeO accumulations in the chaneel. In 1.00Si system, the Si and Me contents of the product increased abnormally. According to the SEM image of MeSAPO-5(1.00Si), the surface of the product was heterogeneous filled with MeSAPO-5 crystal and excess attapulgite. It may explain the increase of Si/Al and Me/Al ratios. Figure 4 showed the result of the thermogravimetric analysis (TG) of MeSAPO-5(0.25Si) molecular sieve. The weight loss

Figure 5. Py-IR spectra of MeSAPO-5 molecular sieves with different Si/Al ratio.

the L acid sites were consumed by Me, and B acid sites were consumed by Si.26 Meanwhile, the decreased intensity of L and B acid sites was attributed to immoderate Me and Si atoms hardly entering into the molecular sieve framework. MeSAPO-5(0.25Si) molecular sieve exhibited two peaks of NH3 desorption (Figure 6). One at ca. 230 °C corresponded to

Figure 4. TG and DTA profile of the MeSAPO-5 molecular sieve with Si/Al ratio of 0.25.

of 4.2% in the range of 40−160 °C was assigned to the loss of water. Because the decomposition temperature of the template TEA centered at 400 °C, a second stage of weight loss centered at 160−500 °C was associated with the removal of template, including thermal desorption and oxidative decomposition of TEA. The weight loss amounts to approximately 6.6%. With further increased temperature, a small weight loss of around 3.0% was likely associated with the further removal of organic residue occluded in the channels and cages of MeSAPO-5. This result suggested that the catalyst had a fine thermal stability. Figure 5 represented FR-IR spectra of pyridine adsorption on MeSAPO-5 samples with different Si/Al ratios. Pyrolysis IR (Py-IR) of MeSAPO-5 samples showed three characteristic bands at 1430−1450, 1480−1500, and 1540−1560 cm−1. According to the literature,25 the band at 1430−1450 cm−1 could be attributed to the adsorbed pyridine at the Lewis (L) acid site, and the band (1540−1560 cm−1) at the Bro̷ nsted (B) acid site, respectively. The pyridine band at 1480−1500 cm−1 could be assigned to B and L acid sites. In addition, the strong band at around 1625 cm−1 was attributed to the adsorbed of pyridine. With increasing of Si/Al ratio from 0.10 to 0.25, the amount of B and L acid sites showed a sharp increase, since enough Si and Me atoms embed the framework of AlPO4−5 molecular sieve by isomorphous substitution. With a further increase of Si content, the gradual decrease in the acid concentration was largely due to structure defects of the molecular sieves with a high Si/Al ratio. It had been known that

Figure 6. NH3-TPD over MeSAPO-5 molecular sieves with different Si/Al ratio.

weak acid sites and the other at ca. 400 °C corresponded to strong acid sites. Indeed, MeSAPO-5(0.10Si) molecular sieve exhibited one peak around 348 °C due to the lack of Lewis acid sites. Compared with MeSAPO-5 (0.10Si), total acidity of the MeSAPO-5 (0.25Si) increased obviously. Total acidity of this MeSAPO-5 (0.25 Si) corresponds to ca. 0.68 mmol/g, whereas the total acidity of MeSAPO-5 (0.10Si) corresponds to ca. 0.35 mmol/g. Therefore, this strong surface acidity of MeSAPO-5 molecular sieve with enough acid sites could be effectively utilized in the dehydration of carbohydrates. 3.3. Dehydration of Carbohydrates to HMF. The catalytic properties of the MeSAPO-5 molecular sieves with various Si/Al ratios were examined in the dehydration of fructose to HMF. The effect of Si/Al ratio on the yield of HMF is shown in Figure 7. As could be seen, it had similar results with the increase of reaction time that the HMF yield increased 1473

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Figure 8. Effect of the initial concentration of carbohydrate on the yield of HMF (40 g of 1:3 (g/g) aqueous/organic phase, 0.10 g of MeSAPO-5 (0.25Si), 170 °C, 2 h).

Figure 7. Effect of Si/Al ratio over MeSAPO-5 molecular sieves on the yield of HMF product (1 g of fructose, 40 g of 1:3 (g/g) aqueous/ organic phase, 0.10 g of MeSAPO-5, 170 °C).

with the reaction time from 0.5 to 2.0 h and the HMF yield decreased after 2.0 h. For the samples with low Si/Al ratio (0.10Si), lower yields of HMF were observed. The generally assumed reaction mechanism of fructose dehydration was first reported by Antal.27 It was considered that fructose degradation began with the structure of the furan ring, and furan ring was transformed into the intermediate of fructofuranose cationic in the presence of H+. Finally, the cyclic intermediates were sequentially dehydrated to the production of HMF. It had been reported that the catalytic activity of H-ZSM-5 on dehydration of carbohydrates to HMF correlated strongly with its high acidity.14 It could hasten the conversion of fructose with strong B acid sites. Meanwhile, the high selectivity of HMF depends on the adequate L acid sites. According to the results of Py-IR and NH3-TPD, the MeSAPO-5(0.25Si) catalyst has abundant L and B acid sites due to modified by Si and Me. This caused an increase of HMF yield. However, with a further increase of the amount of Si, the yield of HMF decreased. This was due to the decrease in the strength of the acid sites. In addition, silica and metallic oxide depositions over MeSAPO-5 molecular sieve led to a suppression of HMF formation and a decrease of HMF yield similar to the effect observed after addition of excess attapulgite. Concentration is an important factor in evaluating the efficiency of the dehydration in practice. The effect on the concentration (w(carbohydrate)/w(aqueous phase)) of different carbohydrates was tested (Figure 8). In the acid-catalyzed dehydration of fructose, the rate of HMF formation from fructose decreased with increase of fructose concentration. As mentioned in the literature,28 this could be attributed to the decrease in the ratio of catalytic active sites (acid sites) to fructose concentration and high concentration of fructose could lead to polymerization. In the case of sucrose, a higher initial concentration (12.5%) was needed to achieve the highest yield (7.7%) as compared to glucose. This confirmed that the conversion of glucose or sucrose to HMF was performed through fructose.29 The mechanism was illustrated in Figure 9. The low yield of HMF was ascribed to the inefficient transition from glucose or sucrose to fructose. We chose the concentration of glucose as 10% for further research on both the yield and economic benefit.

Figure 9. Conversion mechanism of HMF from carbohydrates.

The dehydration of fructose from 0.5 to 3.0 h at 150 to 180 °C was studied in order to determine the effect of reaction time at different temperature on the formation of HMF (Figure 10).

Figure 10. Effect of reaction time at different temperature on the yield of HMF (1 g of fructose, 40 g of 1:3 (g/g) aqueous/organic phase, 0.10 g of MeSAPO-5 (0.25Si)). 1474

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Industrial & Engineering Chemistry Research There seemed to follow the same pattern, that is, the increase of the HMF concentration at the beginning was owing to the hydrolysis of forctose to HMF, and further, the HMF yield decreased. It is generally accepted that HMF is not the final product. With the increase of reaction time, HMF continued to degrade into levulinic acid in the presence of acid catalyst. In addition, the humin would form from fructose self-polymerization and the self-polymerization of HMF also could happen with extension of reaction time. When the reaction was carried out at 150 °C, a yield of 55.7% of HMF was obtained in 2.5 h. Longer reaction time with increased temperature was needed to achieve higher yields (2.5 h at 150 °C, 2.0 h at 160 °C, 2.0 h at 170 °C, 1.5 h at 180 °C). This might due to the faster molecular motions, and faster reaction rates were observed. Nevertheless, higher reaction temperatures not only favored the dehydration of fructose into HMF but also accelerated the formation of byproducts and humins. It had been reported that in a biphasic reaction system the yield of HMF prepered from fructose dehydration sharply increased due to the great extraction effect of organic phase.8 For future study, DMSO was added into the aqueous phase and SBA was added into the organic phases to investigate the effect of additive addition on fructose conversion in the presence of MeSAPO-5 molecular sieve (Figure 11). Considering the

Figure 12. Effect of aqueous/organic phase mass ratio on the yield of HMF product (1 g of fructose, 10 g of aqueous phase, 0.10 g of MeSAPO-5 (0.25Si), 170 °C, 2 h).

to (1) the addition of SBA suppressed self-polymerization of HMF or (2) the reaction shifting to the product side as more HMF was extracted into the organic phase. However, as more organic phase was added, the yield of HMF slightly decreased. The literature14 reported that the effect of organic phase almost approached the saturating value after the volume ratio of MIBK to water increased to 3. This was because as the amount of organic phase increased, the amount of fructose in aqueous phase that was available for the reaction decreased. The effect of the amount of catalyst on the dehydration of fructose is given in Figure 13. Even in the absence of MeSAPO-

Figure 11. Effect of the additive addition on the yield of HMF product (1 g of fructose, 40 g of 1:3 (g/g) aqueous/organic phase, 0.10 g of MeSAPO-5 (0.25Si), 170 °C, 2 h).

proton transfer and water formation from degradation of fructose, DMSO addition could reduce the influence of water to the reaction and avoid the levulinic acid byproduct generated from hydrolyzation of HMF, resulting in the higher yield of HMF.30 However, the necessary water content was needed to form a biphasic system. In addition, the SBA addition could effectively improve the HMF yield because SBA addition could prevent the self-polymerization of HMF. Different amounts of organic phase were added into the aqueous phase to investigate the effect of aqueous/organic phase mass ratio on the conversion of fructose to HMF in the water(DMSO)−MIBK(SBA) system. (Figure 12) Increasing the amount of organic phase led to a significant increase in the yield of HMF. The HMF yield reached a maximum of 73.9% at mass ratio of 1:3.0 (aqueous:organic phase). This might be due

Figure 13. Effect of catalyst usage on the yield of HMF product (1 g of fructose, 40 g of 1:3 (g/g) aqueous/organic phase, 170 °C, 2 h).

5, fructose could be converted to HMF by self-catalyzed dehydration due to the presence of H+ and OH− dissociated from water.31 The yield of HMF could be increased by adding MeSAPO-5 as a catalyst. For instance, the yield HMF reached 73.9% at 170 °C for 2.0 h when 0.100 g of MeSAPO-5 was added. However, with a further increase of the amount of the catalyst over 0.100 g, the yield of HMF would not change. This was because 0.100 g of MeSAPO-5 had provided enough catalytic sites.5 But the other literature12 mentioned that high dosage of catalyst also favored the rehydration of HMF into levulinic acid and other side reactions in the system. 1475

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attapulgite. MeSAPO-5 molecular sieve could act as a catalyst to efficiently convert carbohydrates to HMF. The yield of HMF was greatly affected by Si/Al ratio of catalyst, initial concentration of the starting materials, reaction time, reaction temperature, the mass ration of aqueous/organic phases, and the amount of the catalyst. MeSAPO-5(0.25Si) molecular sieves with abundant Lewis and Bro̷ nsted acid sites exhibited high catalytic activity using the initial concentration of fructose as 10%, giving HMF yield of 73.9% at 170 °C with 2.0 h [w(organic)/w(aqueous) = 3, w(MeSAPO-5)/w(fructose) = 0.100]. The HMF yield increased with increased Si/Al ratio, which suggested that the molecular sieves with a larger amount of acid sites were more effective for the dehydration of carbohydrates. Moreover, the catalyst was easily recycled. MeSAPO-5 molecular sieve could be used as an effective catalyst for the dehydration of carbohydrates.

The recycle of catalyst is of great importance in practice. Figure 14 showed the recycle of MeSAPO-5(0.25Si) catalyst in

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Tel.: +86-519-86330356.

Figure 14. Recycle of the MeSAPO-5 catalyst in the dehydration of fructose (1 g of fructose, 40 g of 1:3 (g/g) aqueous/organic phase, 0.10 g of MeSAPO-5 (0.25Si), 170 °C, 2 h).

Notes

The authors declare no competing financial interest.

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a biphasic system. The results revealed that MeSAPO-5 retained good performance after being used five times at 170 °C for 2.0 h. After three times usage, there was a slightly decrease in the HMF yield. This was attributed to the catalytic sites being covered by organic compounds and the crystal structure being partially destroyed. Table 2 showed the catalytic performances of different reported catalysts, as well as the performance of our MeSAPO-

ACKNOWLEDGMENTS This work is supported by National Natural Science Foundation (21276029), Natural Science Foundation of Jiangsu (BK20131142), Jiangsu Key Laboratory of Advanced Catalytic Materials and Technology (BM2012110), the Perspective Research Foundation of Production Study and Research Alliance of Jiangsu Province of China under Grant BY2014037-15, a project funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD) and the project of overseas research plan for outstanding research groups, young teachers, and principals in Jiangsu Province.

Table 2. Catalytic Performance of Different Catalyst in the Dehydration of Fructose catalyst* HCl TiO2 NPs WO3/ZrO2 PBS (H3PO4assisted) P2O5 MeSAPO-5

solvent system biphasic system biphasic system single system biphasic system ionic liquid system biphasic system

temperature (°C)

reaction time (h)

HMF yield (%)

reference

170

0.07

84.6

8

130

0.25

54.0

1

130

4.0

36.7

10

150

0.5

88.0

32

80

0.5

78.7

15

170

2.0

73.9

this work

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REFERENCES

(1) Dutta, S.; De, S.; Patra, A. K.; Sasidharan, M.; Bhaumik, A.; Saha, B. Microwave assisted rapid conversion of carbohydrates into 5hydroxymethylfurfural catalyzed by mesoporous TiO2 nanoparticles. Appl. Catal., A: Gen. 2011, 409−410, 133. (2) Tong, X.; Li, Y. Efficient and selective dehydration of fructose to 5-hydroxymethylfurfural catalyzed by Bro̷ nsted-acidic ionic liquids. ChemSusChem 2010, 3, 350. (3) Vennestrom, P. N.; Osmundsen, C. M.; Christensen, C. H.; Taarning, E. Beyond petrochemicals: the renewable chemicals industry. Angew. Chem., Int. Ed. 2011, 50, 10502. (4) Qi, X.; Guo, H.; Li, L. Efficient Conversion of Fructose to 5Hydroxymethylfurfural Catalyzed by Sulfated Zirconia in Ionic Liquids. Ind. Eng. Chem. Res. 2011, 50, 7985. (5) Qi, X.; Guo, H.; Li, L.; Smith, R. L., Jr. Acid-catalyzed dehydration of fructose into 5-hydroxymethylfurfural by cellulosederived amorphous carbon. ChemSusChem 2012, 5, 2215. (6) Jadhav, H.; Taarning, E.; Pedersen, C. M.; Bols, M. Conversion of D-glucose into 5-hydroxymethylfurfural (HMF) using zeolite in [Bmim]Cl or tetrabutylammonium chloride (TBAC)/CrCl2. Tetrahedron Lett. 2012, 53, 983. (7) Chheda, J. N.; Roman-Leshkov, Y.; Dumesic, J. A. Production of 5-hydroxymethylfurfural and furfural by dehydration of biomassderived mono- and poly-saccharides. Green Chem. 2007, 9, 342. (8) Salak Asghari, F.; Yoshida, H. Acid-catalyzed production of 5hydroxymethyl furfural from D-fructose in subcritical water. Ind. Eng. Chem. Res. 2006, 45, 2163.

*

TiO2 NPs: TiO2 nanoparticles. PBS: phosphate buffer system.

5 molecular sieve, in different solvent systems. The cost and energy consumption of the dehydration of fructose using MeSAPO-5 as a catalyst were acceptable. More importantly, the recycle of MeSAPO-5 was easily achieved. Considering the development of new catalysts for the dehydration of fructose to HMF, MeSAPO-5 molecular sieve will be a promising candidate for this application.

4. CONCLUSIONS In conclusion, MeSAPO-5 molecular sieves (Me = Fe, Mg) with abundant acid sites were successfully synthesized from 1476

DOI: 10.1021/ie504243t Ind. Eng. Chem. Res. 2015, 54, 1470−1477

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DOI: 10.1021/ie504243t Ind. Eng. Chem. Res. 2015, 54, 1470−1477