Effective conversion of biomass-derived ethyl levulinate into γ-valerolactone over commercial zeolite supported Pt catalysts

Abstract

The synthesis of γ-valerolactone from biomass-derived ethyl levulinate is of great importance for biomass conversion. However, development of efficient catalytic systems which are simple, commercially available, easy for preparation, and large-scale for the hydrogenation of ethyl levulinate to afford γ-valerolactone is still necessary. Here, a series of commercial zeolite supported catalysts were synthesized by using a wet impregnation method for the systemic investigation of the hydrogenation of biomass-derived ethyl levulinate. High yield and selectivity towards GVL were achieved and varied and systematic characterizations including XRD, XPS, TEM and BET were used to investigate these catalysts. The influence of different reaction condition parameters was also investigated and discussed. The construction of zeolite supported catalysts showed broad prospects for the conversion of biomass into biofuels.

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1 Introduction

With the gradual exhaustion of fossil resources and global warming, more attention has been paid to the sustainable conversion of renewable resources.¹ Biomass, which is widespread, cheap, renewable, carbon-neutral and abundant, is known as the only renewable carbon resource which could replace fossil resources for the production of chemicals and fuels.² Among the biomass-derived chemicals, levulinic acid (LA) is regarded as one of the top value added chemicals from biomass.³ It has been reported by our group that liquid acid catalyst, magnetic solid acid catalyst or sulfonated chloromethyl polystyrene solid acid catalyst could catalyze the conversion of biomass to LA.⁴ LA could be converted into a series of useful compounds (e.g. γ-valerolactone (GVL), 2-methyltetrahydrofuran, 1,4-pentanediol, valerate esters, levulinate esters, acrylic acid, aminolevulinate acid, diphenolic acid, acetylacrylic acid, angelilactones, etc.) using LA as starting material.³

Among the derivatives of LA, GVL is a very promising compound with broad application prospects. GVL has the following properties: (1) high boiling point (207–208 °C); (2) nonvolatile; (3) high lower heating value (LHV, 25 MJ kg⁻¹); (4) high flash point (96 °C); (5) high density (1.04 g cm⁻³, 15 °C); (6) appropriate kinematic viscosity (2.1 mm² s⁻¹, 40 °C) compared with diesel (2.5 mm² s⁻¹, 40 °C), which made it featured with stability, low temperature fluidity, low toxicity, degradability, storability for the applications.⁵ GVL could be used as the additive to gasoline, diesel and biodiesel, liquid fuels, intermediate and solvent in chemical and pharmaceutical industry.⁶ A series of valuable chemicals (e.g. levulinate esters, 1,4-pentanediol, dimethyl adipate, succinic acid, caprolactone, pentenoic acid, 5-nonanone) and fuels (valeric esters, alkanes, 2-methyltetrahydrofuran) could be obtained through the derivative relations of GVL.⁶ⁱ For example, 1,4-pentanediol (1,4-PDO) could be obtained through the hydrogenolysis of GVL, which is regarded as the monomer of biodegradable polymers. For instance, Feng et al., Fan et al. and our group reported the hydrogenation of biomass-derived GVL to 1,4-PDO using supported Cu catalysts.⁷ Therefore, it is vital to develop a series of catalytic systems for the conversion of biomass to GVL.

Generally, GVL could be produced through the catalytic hydrogenation–cyclization of LA or its esters. The synthesis of GVL from LA could be carried out over homogeneous or heterogeneous catalysts using formic acid or molecular hydrogen as hydrogen source.⁸ According to the previous reports, homogeneous Ru⁹ and a series of supported heterogeneous catalysts (e.g. Ru, Pd)¹⁰ were efficient for the hydrogenation of LA to GVL under molecular hydrogen atmosphere. Recently, our group reported that Cu-WO₃/ZrO₂-CP-300 could catalyze the conversion of LA to GVL and 94% yield could be obtained.^7b In addition to molecular hydrogen, formic acid could also be used as the hydrogen source for the hydrogenation of LA.¹¹ Horváth and we reported that homogeneous Ru catalysts were efficient for the conversion of LA to GVL.¹² Subsequently, other homogeneous catalysts were reported to be available. For example, our group developed Ir and Fe catalytic systems for the hydrogenation of LA.¹³ Although homogeneous catalysts showed high activity, and the reaction conditions are relatively milder, their inherent shortcomings are obvious. For instance, the preparation of homogeneous catalysts is usually complicated, ligands are mainly necessary for the high performance, and it is difficult to separate the catalysts from the reaction mixture.¹⁴ Therefore, it is significant to develop heterogeneous catalysts for this process. Our group reported the Ru-P/SiO₂ catalyst for hydrogenation of LA using formic acid as hydrogen source and the catalyst could be recycled.¹⁵ Later, Au, Ag, Cu, Ni and Co were found to be efficient for the transformation of LA.¹⁶ Apart from LA, levulinate esters (LE) were confirmed that they could be converted into GVL. Moreover, compared to LA, higher yield of LE could be achieved and levulinate esters are easier to be separated than LA.¹⁷ Therefore, it seems to be more attractive to synthesize GVL from LE. A variety of catalytic systems were confirmed to be efficient for the conversion of LE to GVL using molecular hydrogen or alcohols as hydrogen donor. Metal nanoparticles supported catalysts (e.g. Ru, Pd, Ag, Cu, Ni, Zr) have been reported for the hydrogenation of LE to GVL.¹⁸ Besides, catalytic transfer hydrogenation (CTH) of LE to GVL through Meerwein–Ponndorf–Verley (MPV) reduction using alcohol as hydrogen source was also widely studied. In these cases, alcohols served as both hydrogen donor and reaction solvent. For example, ZrO₂, Zr-beta, ZrO(OH)₂·xH₂O, Ru(OH)_x/TiO₂, Zr-HBA, ZrFeO_x, zirconium-based MOF, Ni–Zr, Cu–ZrO₂ and Hf-beta were successfully applied to the CTH of LE to GVL.¹⁹ Our group also reported that RANEY® Ni could catalyze the hydrogenation of LE.²⁰ However, for the consideration of commercial process, it is still necessary to investigate efficient catalytic systems which are simple, commercial available, easy for preparation, large-scale production for the hydrogenation of LE to afford GVL.

Zeolites have been widely used as solid acid catalysts or catalyst supports in petrochemical industry.²¹ They are very appropriate for catalysis because of their excellent hydrothermal stability and molecular sieving capability. Recently, zeolite-based catalysts were found to be efficient for bio-refinery processes. For instance, aromatic compounds can be catalytically obtained from renewable furan derivatives.²² In consideration of the advantages of zeolite-based catalysts, a series of commercial zeolite supported catalysts were synthesized by wet impregnation method for the systemic investigation of the hydrogenation of biomass-derived ethyl levulinate (EL). To our delight, high yield and selectivity towards GVL could be achieved. Varied and systematic characterizations were used to investigate these catalysts. Finally, for further investigation of these catalysts, the influence of different reaction parameters was also investigated. The construction of zeolite supported catalysts showed their broad application prospects for the conversion of biomass into biofuels.

2 Experimental

2.1 Materials

EL and GVL were provided by Hefei Leaf Energy Biotechnology Co., Ltd (http://www.leafresource.com). Chloroplatinic acid hexahydrate was supplied by Shanxi Kaida Chemical Engineering Co., Ltd. Zeolites supports (e.g. MCM-22, MCM-41, SAPO-34, ZSM-35, ZSM-5, HY, USY, MOR) were purchased from Nankai University Catalyst Co., Ltd.

2.2 Catalyst preparation

All of the zeolites supported Pt catalysts in this work were prepared using the wet impregnation methods. For a typical preparation, 1 wt% Pt/MCM-22, the zeolite MCM-22 (5.0 g) was sufficiently dispersed in 20 ml deionized water named as suspension A, chloroplatinic acid hexahydrate (0.134 g, 0.259 mmol) was dissolved in 10 ml deionized water named as solution B. Solution B was dropped into suspension A with violent agitation at room temperature. The mixture was supposed to stir vigorously for another 24 h. After impregnation, the mixture was transferred to an oven and dried at 110 °C for 12 h to dehydrate. Subsequently, the mixture was reduced in a tube furnace under a N₂/H₂ mixed gas. The flow rates for both gases were 60 ml min⁻¹ while the temperature of the tube furnace was raised from ambient temperature to 400 °C at the rate of 10 °C min⁻¹ and kept at 400 °C for 2 h. After cooling down to room temperature, the reduced catalyst was collected and marked as 1% Pt/MCM-22. The preparation procedures for 1% Pt/MCM-41, 1% Pt/SAPO-34, 1% Pt/ZSM-35, 1% Pt/ZSM-5, 1% Pt/HY, 1% Pt/USY, 1% Pt/MOR were similar to that for 1% Pt/MCM-22.

2.3 Catalyst characterization

The X-ray power diffraction (XRD) patterns of these zeolite supported catalysts were measured by a X'pert (PANalytical) diffractometer at 40 kV and 200 mV. The scanning of diffraction angle ranges from 10 degree to 70 degree with a sampling interval of 0.02 degree.

The X-ray photoelectron spectroscopy (XPS) patterns of the catalysts were measured by a Thermo Scientific Escalab 250-X-ray photoelectron spectrometer using an Al Kα monochromatized source. During the measurement, residual pressure was kept below 1 × 10⁻⁷ Pa. For removing the charge effect, C 1s, which is determined at 284.8 eV, was used as a standard.

The Brunauer–Emmett–Teller (BET) method was used to determine the specific surface areas of the catalysts on a Micromeritics ASAP 2020 analyzer using N₂ physical adsorption at −195.8 °C.

The transmission electron microscopy (TEM) images of the prepared catalysts were obtained from a JEOL-2010 electron microscope. The samples were dispersed in ethanol by ultrasound and then deposited on a Cu girds.

NH₃ temperature programmed desorption (NH₃-TPD) was measured by homemade instrument. For NH₃-TPD, 80.00 mg sample was weighed and put into a quartz tube, which then put into the furnace. Firstly, temperature was raised to 400 °C and held 1 h at Ar atmosphere to remove absorbed gases on sample surface. After cooling down, NH₃ was pumped into the tube for 1 h in order to fully saturate the sample. Then, NH₃ was stopped and Ar was applied to remove excess NH₃ at 80 °C. Finally, sample underwent a programmed desorption with temperature rise from 80 °C to 550 °C at the rate of 10 °C min⁻¹. Desorption of NH₃ was detected by thermal conductivity detector (TCD).

2.4 Catalyst test

The hydrogenation reaction of EL was carried out in a 25 ml autoclave (Anhui Kemi Machinery Technology Co., Ltd., China). In a typical reaction, 1 mmol of EL, 100 mg of catalyst and 12 ml of ethanol were loaded into the autoclave equipped with a magnetic stirrer. Then the reactor was purged with hydrogen for 5 times and the final H₂ pressure was reached a set value such as 6 MPa at ambient temperature. The temperature of the reactor was then raised to a fixed value such as 200 °C and kept for a set period such as 6 h. After the reaction was finished and the reactor was cooled down to room temperature, mixture in the reactor was centrifugated and collected. The supernatant was examined and analyzed by gas chromatograph-mass spectrometer (GC-MS) and gas chromatograph (GC) using a RTX-65 gas chromatographic column, diethylene glycol dimethyl ether was used as the internal standard.

3 Results and discussion

3.1 Characterization of the zeolite supported catalysts

After a series of zeolite supported Pt catalysts were prepared, both X-ray powder diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were employed to determine the element components and crystal formation of these catalysts. The power XRD patterns of zeolite supported Pt catalysts are showed in Fig. 1 and 2. According to the previous reports,²³ the characteristic peaks corresponding to the zeolites could be clearly seen in the XRD patterns in Fig. 1. And the reflection peaks corresponding to metallic Pt phase could be found in the patterns of all the prepared supported Pt catalysts (Fig. 2). The intensity of metallic Pt phase reflection signals was relatively low possibly due to the low loading contents of Pt in the catalysts. Three typical reflection peaks of fcc structure Pt²⁴ (e.g. the crystal face (111), (200) and (220), respectively) could be seen. The unclear Pt reflection peak of some catalysts such as 1% Pt/MCM-22 and 1% Pt/MCM-41 maybe attributed to high dispersion or small particle sizes of Pt nanoparticles (listed in Table 1), which lead to a broadening reflection peaks. To obtain a complete and clear phase data, XPS was used to analysis catalysts with low resolution.

Fig. 1 Characteristic diffraction peaks of zeolites.

Fig. 2 XRD patterns of zeolite supported catalysts.

Table 1 Physico-chemical properties of catalysts

Catalyst	DMP^a/nm	Surface area^b/m^2 g^−1	Pore volume^c/cm^3 g^−1	Pore size^d/nm
a Mean crystal size of the metallic Pt phase, calculated from TEM images.b BET surface area.c BJH desorption cumulative volume of pores between 17.0 Å and 3000.0 Å diameter.d BJH desorption average pore diameter (4V/A).
Pt/MCM-22	5.05	473.88	1.11	29.16
Pt/MCM-41	2.45	427.81	0.11	5.70
Pt/SAPO-34	2.85	313.80	0.02	3.11
Pt/ZSM-35	8.88	266.94	0.17	28.06
Pt/ZSM-5	2.85	330.02	0.08	4.25
Pt/HY	4.62	637.83	0.07	5.02
Pt/USY	6.35	217.39	0.13	2.22
Pt/MOR	2.91	293.53	0.06	7.16

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The X-ray photoelectron spectroscopy (XPS) analysis of 1% Pt/MCM-22 and 1% Pt/MCM-41 is performed to verify the existence of Pt which could not be clearly detected from XRD. It has been reported²⁵ that the B.E. position of Al(III) 2p is 74.8 eV, which is close to that of metallic Pt 4f_5/2 (74.3 eV). Considering that the absolute existence of Pt and the content of Al is higher than Pt, the peak of Al(III) 2p would overlap the peak of metallic Pt 4f_5/2, the existence of Pt could not be determined by the B.E. peak of Pt 4f_5/2. However, it has also been reported²⁵ that the B.E. position of metallic Pt 4f_7/2 is 71.5 eV, which has 2.8 eV band gap with Al(III) 2p and could be easily divided. It could be confirmed from Fig. 3 that the characteristic B.E. peak of metallic Pt 4f_7/2 could be obviously detected for 1% Pt/MCM-22 and 1% Pt/MCM-41, and the B.E. peak of metallic Pt 4f_7/2 for all the other supported Pt catalysts could also be found which are presented in the ESI.†

Fig. 3 XPS in the Pt 4f region for supported Pt catalysts.

TEM images of all the supported Pt catalysts were also investigated in order to obtain the micro-structure images of the Pt nanoparticles and zeolites. It could be determined from the TEM images in Fig. 4 that Pt particles could be clearly see and Pt nanoparticles were dispersed uniformly in all the prepared catalysts with a mean size from 2.45 nm to 8.88 nm. The dimensions of the metallic Pt phase (D_MP) were calculated from Fig. 4 and listed in Table 1. The size distribution of Pt nanoparticles in these catalysts could be found in the ESI.†

Fig. 4 TEM image of (a) Pt/MCM-22 (b) Pt/MCM-41 (c) Pt/SAPO-34 (d) Pt/ZSM-35 (e) Pt/ZSM-5 (f) Pt/HY (g) Pt/USY (h) Pt/MOR.

The Brunauer–Emmett–Teller (BET) analysis was employed to investigate the specific surface area, pore volume and pore size of the catalysts, which is an important part of the physico-chemical properties. The physico-chemical properties of these catalysts were also listed in Table 1. The NH₃-TPD results of the supported Pt catalysts are presented in ESI.†

3.2 Selective hydrogenation of EL

Selective hydrogenation of EL to afford GVL was performed over different zeolite supported Pt catalysts and GC-MS/GC were used for the analysis of the products. The conversion of EL was used as an evaluation standard for the comparison of the catalytic activity of these catalysts. It could be found that when 1% Pt/HY was used for the hydrogenation of EL (Table 2, entry 6), the conversion of EL was only 31.8% and the selectivity towards GVL was just 39.9%, indicating its low activity for this reaction. Similar activity was obtained when 1% Pt/USY was used for the hydrogenation of EL, the conversion of EL and selectivity to GVL were 43.0% and 38.4%, respectively (Table 2, entry 7). A slightly higher conversion of EL could be obtained when 1% Pt/MOR was used for the hydrogenation of EL (Table 2, entry 8), however, the selectivity to GVL was just 41.5%. Although low conversion of EL was received when 1% Pt/SAPO-34 was used, the selectivity toward GVL in this catalytic system reached 81.5%. Actually, according to the previous work, the conversion of EL to GVL included two steps: hydrogenation of EL to form the intermediate 4-hydroxypentanoate (4-HPE) and subsequently the catalytic lactonization of 4-HPE to form GVL. The active Pt nanoparticles in the catalysts would catalyze the hydrogenation of C=O in EL to form 4-HPE, and the acidic zeolite supports were responsible for the lactonization of 4-HPE. The interaction between metallic Pt and zeolite support would influence the hydrogenation activity of Pt nanoparticles, it is hard to distinguish the differences of all the supported Pt catalysts from Table 1. However, according to the XPS results (see ESI†) of 1% Pt/HY, 1% Pt/USY and 1% Pt/SAPO-34, the signals of Pt 4f_5/2 were relatively weaker, in accordance with the low conversions of EL over these catalysts. A higher conversion (e.g. 70.8%) of EL could be reached when 1% Pt/MCM-41 was used, however, the selectivity towards GVL was only 52.5%, which indicated the inefficiency of this catalyst for the conversion of the intermediate 4-HPE to GVL. To our delight, almost full conversion of EL was reached when 1% Pt/MCM-22, 1% Pt/ZSM-35, 1% Pt/ZSM-5 (e.g. 97.6%, 100% and 97.8%, respectively) were used for the hydrogenation of EL, which confirmed the high activity of metallic Pt in these catalysts. Nevertheless, the selectivities towards GVL were different, when 1% Pt/MCM-22 and 1% Pt/ZSM-5 were used for the hydrogenation of EL, the selectivities were 62.1% and 57.1%, respectively, resulting in low yields of GVL. One possible reason for these phenomena was lying in the relative lower acid strength (see ESI†). When 1% Pt/ZSM-35 was used for the hydrogenation of EL, 100% conversion was reached and the selectivity towards GVL was 99.0%, confirmed the high activity of metallic Pt nanoparticle and proper surface acidity of the zeolite support. Obviously, 1% Pt/ZSM-35 was the most efficient catalyst in the list of catalysts, resulting high conversion of EL and high yield of GVL. In order to have a further insight of 1% Pt/ZSM-35, the influence of different reaction parameters on the hydrogenation of EL was also investigated.

Table 2 Selective hydrogenation of EL over various zeolite supported Pt catalysts at 200 °C^a

Entry	Catalyst	Conv./%	Sel./%	Yield/%
a Reaction conditions: 1.0 mmol of EL, 100 mg of zeolite supported Pt catalysts, 12 ml of ethanol, P(H2) = 6.0 MPa, T = 200 °C, t = 6.0 h.
1	1% Pt/MCM-22	97.6	62.1	60.6
2	1% Pt/MCM-41	70.8	52.5	37.2
3	1% Pt/SAPO-34	37.2	81.5	30.3
4	1% Pt/ZSM-35	100	99.0	99.0
5	1% Pt/ZSM-5	97.8	57.1	55.8
6	1% Pt/HY	31.8	39.9	12.7
7	1% Pt/USY	43.0	38.4	16.5
8	1% Pt/MOR	55.6	41.5	23.1

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3.3 Effect of reaction temperature

Temperature is one of the important factors of converting EL into GVL. Herein, a series of experiments with different temperatures were designed in order to investigate the influence between GVL yield and temperature. It can be confirmed from Fig. 5 that temperature greatly influenced EL conversion and selectivity of GVL. When temperature was relatively low, such as 180 °C, the reaction was hard to process. Under this reaction condition, GVL yield was only 30.1% while selectivity was 79.2%, which means not only hydrogenation but also cyclization were not fully accomplished. When temperature rose to 190 °C, yield and selectivity increased to 85.6% and 91.5% respectively. Optimal GVL yield was reached when the temperature reached 200 °C, and all of the reactant was converted, which means higher temperature would accelerate the reaction. However, when temperature further increased, although EL was still fully converted, the yield of GVL was decreased to about 97%, which can attribute to over hydrogenation of GVL.

Fig. 5 Effect of different temperature on the conversion of EL to GVL. Reaction conditions: 1.0 mmol of EL, 100 mg of 1% Pt/ZSM-35, 12 ml of ethanol, P(H₂) = 6.0 MPa, t = 6.0 h.

3.4 Effect of hydrogen pressure

Generally, hydrogen pressure is vital in catalytic hydrogenation reaction. Further experiments about how the hydrogen pressure affects the reaction process were investigated. It can be confirmed from Fig. 6 that selectivity of the reaction less related to hydrogen pressure. High selectivities were obtained while the H₂ pressure changed from 1 MPa to 6 MPa. Even when H₂ was only 1 MPa, the selectivity reached to 93.8%, which is the lowest datum in this test. However, EL conversion was closely connected with H₂ pressure in the reaction. When the hydrogen pressure was 1 MPa, conversion of EL reached 58.3% and GVL yield was just 54.7%. Then, GVL yield increased to 68.7% at a H₂ pressure of 2 MPa. And the value of yield further rose to 72.1% while the pressure reached 3 MPa. It is obvious that conversion of EL positive correlated to the H₂ pressure and reached a maximum of 100% when pressure increased to 6 MPa. This phenomenon may attribute to the reason that higher H₂ pressure lead to a higher H₂ concentration on the surface of the catalyst, thereby accelerating the catalytic process.

Fig. 6 Effect of H₂ pressure on the conversion of EL to GVL. Reaction conditions: 1.0 mmol of EL, 100 mg of 1% Pt/ZSM-35, 12 ml of ethanol, T = 200 °C, t = 6.0 h.

3.5 Effect of solvent

It was reported that oxygen-containing solvents have a strong solvent effect in catalytic hydrogenation from carbohydrates to GVL,¹⁰ⁱ which means the investigation of the effect of solvent is meaningful. Here, different solvents were applied in searching for solvent effect on EL conversion. Reactant conversion rates and GVL yields in common solvents were presented in Fig. 7. It is clear that after the optimal conditions of temperature and hydrogen pressure were selected, changing the solvent did not greatly influence the conversion of EL and selectivity towards GVL. When propanol, isopropanol, tetrahydrofuran were selected, the conversions of EL were almost 100%, however, the yields of GVL reached 86.6%, 81% and 86% respectively, which means although the conversion was held on a high level, selectivity of the reaction was partly influenced by the solvent.

Fig. 7 Effect of solvent on the conversion of EL to GVL. Reaction conditions: 1.0 mmol of EL, 100 mg of 1% Pt/ZSM-35, 12 ml of solvent, T = 200 °C, t = 6.0 h, P(H₂) = 6 MPa.

3.6 Effect of reaction time

Reaction time is of great importance in EL conversion because reactant cannot be fully consumed in a short time while too long reaction time leads to an uneconomical usage of energy and sometimes more by-product. So reactions were restrained at different reaction times in order to discover the effect of reaction time. It can be informed from Table 3 that selectivity was always at a high level. Moreover, the conversion can be accumulated as the reaction time prolonged. At the initial time of the reaction (e.g. 0.5 h), the conversion of EL was only 38.8%. With the prolonging of the time, the conversion was increased and reached 100% at 6 h. Nevertheless, extending time to 10 h led a slight decrease of GVL yield which can also attribute to the over hydrogenation of GVL.

Table 3 Time course of the ethyl levulinate hydrogenation^a

Entry	t/h	Conv./%	GVL yield/%
a Reaction conditions: 1.0 mmol of EL, 100 mg of 1% Pt/ZSM-35, 12 ml of ethanol, T = 200 °C, P(H2) = 6 MPa.
1	0.5	37.7	33.6
2	1	52.2	50.6
3	2	75.2	71.8
4	4	91.3	88.5
5	6	100	99
6	10	100	97

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3.7 Recycle of the catalysts

The stability of the catalysts is of great importance for the commercial process of GVL. To test the stability of 1% Pt/ZSM-35, the catalyst was collected by centrifugation after the reaction and washed with ethanol for several times, and then it was directly reused for the next run. It could be found from Fig. 8 that high selectivity towards GVL was kept after three times. However, the conversion of EL decreased to 90.4% after being used for three times. The yield of GVL after the third run was 84.0%. A possible explanation for this phenomenon was lying in the inevitable substance loss of the catalyst during the recovery process, agglomerate of Pt nanoparticles or deposition of carbonaceous species on the surface of the catalyst, which was in accordance with the previous work.²⁶ The characterization of used 1% Pt/ZSM-35 catalyst was carried out, and compared with fresh catalyst in order to confirm this explanation, which images could be found in ESI.† It could be found from TEM image that Pt nanoparticle showed partly agglomerate, the mean diameter of used catalyst increased to roughly 20 nm. It could be found from the XRD patterns that the metallic Pt characteristic peak could still be found in the used catalyst, while the strength of the peak was slightly weaker, which indicated a possible mass loss of Pt. This phenomenon could also be confirmed from the XPS analysis, which showed a decreased relative peak area of Pt 4f_7/2.

Fig. 8 The recyclability of 1% Pt/ZSM-35. Reaction conditions: 1.0 mmol of EL, 100 mg of 1% Pt/ZSM-35, 12 ml of ethanol, T = 200 °C, t = 6.0 h, P(H₂) = 6 MPa.

4 Conclusions

In conclusion, a series of commercial zeolite supported Pt catalysts were prepared by a wet impregnation method, and used for the investigation of the hydrogenation of biomass-derived EL to GVL. Among these catalysts, 1% Pt/ZSM-35 was found to show the highest activity through the catalyst screening, under optimized conditions, 100% conversion of EL with a high GVL selectivity (99.0%) were achieved. The influence of different reaction parameters on the hydrogenation of EL was also investigated, and the best reaction conditions were 200 °C, 6 MPa H₂, ethanol was found to be the optimum reaction solvent. The stability test of the catalyst showed that 1% Pt/ZSM-35 kept high activity towards GVL after used for at least three times. The current work highlighted the efficient zeolite supported catalysts for the conversion of biomass-derived molecules into biofuels.

Acknowledgements

This work was supported by the 973 Program (2012CB215305, 2012CB215306, 2013CB228103), NSFC (21325208, 21172209, 21272050, 21402181, 21572212), CAS (KJCX2-EW-J02), IPDFHCPST (2014FXCX006), CPSF (2014M561835), SRFDP (20123402130008), Fundamental Research Funds for the Central Universities (WK2060190025, WK2060190033, WK2060190040, WK6030000023), the Key Technologies R&D Programme of Anhui Province (1604a0702027) and Program for Changjiang Scholars and Innovative Research Team in University of the Ministry of Education of China.

Notes and references

1. (a) J. C. Serrano-Ruiz and J. A. Dumesic, Energy Environ. Sci., 2011, 4, 83; (b) E. L. Kunkes, D. A. Simonetti, R. M. West, J. C. Serrano-Ruiz, C. A. Gärtner and J. A. Dumesic, Science, 2008, 322, 417; (c) G. W. Huber, S. Iborra and A. Corma, Chem. Rev., 2006, 106, 4044.
2. (a) P. Gallezot, Chem. Soc. Rev., 2012, 41, 1538; (b) K. Barta and P. C. Ford, Acc. Chem. Res., 2014, 47, 1503; (c) C. Z. Li, X. C. Zhao, A. Q. Wang, G. W. Huber and T. Zhang, Chem. Rev., 2015, 115, 11559; (d) A. Corma, S. Iborra and A. Velty, Chem. Rev., 2007, 107, 2411; (e) M. Mascal, S. Dutta and I. Gandarias, Angew. Chem., Int. Ed., 2014, 53, 1854.
3. Top Value Added Chemicals From Biomass. Volume I: Results of Screening for Potential Candidates from Sugars and Synthesis Gas, Technical report identifier PNNL-14804, Pacific Northwest National Laboratory and the National Renewable Energy Laboratory, August 2004, http://www1.eere.energy.gov/biomass/pdfs/35523.pdf.
4. (a) J. Li, D. J. Ding, L. J. Xu, Q. X. Guo and Y. Fu, RSC Adv., 2014, 4, 14985; (b) D. M. Lai, L. Deng, Q. X. Guo and Y. Fu, Energy Environ. Sci., 2011, 4, 3552; (c) D. M. Lai, L. Deng, J. A. Li, B. Liao, Q. X. Guo and Y. Fu, ChemSusChem, 2011, 4, 55; (d) Z. Yong, Z. Ying and Y. Fu, ChemCatChem, 2014, 6, 753.
5. (a) Á. Bereczky, K. Lukács, M. Farkas and S. Dóbé, Nat. Resour., 2014, 5, 177; (b) Á. Bereczky, K. Lukács, M. Farkas and S. Dóbé, Proceedings of the European Combustion Meeting, 2013, Paper P3-37, ISBN 978-91-637-2151-9.
6. (a) I. T. Horváth, H. Mehdi, V. Fabos, L. Boda and L. T. Mika, Green Chem., 2008, 10, 238; (b) J. C. Serrano-Ruiz, D. J. Braden, R. M. West and J. A. Dumesic, Appl. Catal., B, 2010, 100, 184; (c) J. Q. Bond, D. M. Alonso, D. Wang, R. M. West and J. A. Dumesic, Science, 2010, 327, 1110; (d) J. P. Lange, R. Price, P. M. Ayoub, J. Louis, L. Petrus, L. Clarke and H. Gosselink, Angew. Chem., 2010, 122, 4581; (e) R. Palkovits, Angew. Chem., Int. Ed., 2010, 49, 4336; (f) L. E. Manzer, Appl. Catal., A, 2004, 272, 249; (g) P. G. Jessop, Green Chem., 2011, 13, 1391; (h) I. T. Horváth, Green Chem., 2008, 10, 1024; (i) K. Yan, Y. Y. Yang, J. J. Chai and Y. R. Lu, Appl. Catal., B, 2015, 179, 292.
7. (a) Y. Q. Yang, X. L. Xu, W. J. Zou, H. J. Yue, G. Tian and S. H. Feng, Catal. Commun., 2016, 76, 50; (b) X. L. Du, Q. Y. Bi, Y. M. Liu, Y. Cao, H. Y. He and K. N. Fan, Green Chem., 2012, 14, 935; (c) Q. Xu, X. L. Li, T. Pan, C. G. Yu, J. Deng, Q. X. Guo and Y. Fu, Green Chem., 2016, 18, 1287.
8. F. Liguori, C. Moreno-Marrodan and P. Barbaro, ACS Catal., 2015, 5, 1882.
9. (a) K. Osakada, S. Yoshikawa and T. J. Ikariya, Organomet. Chem., 1982, 231, 79; (b) T. Ohkkuma, M. Kitamura and R. Noyori, Tetrahedron Lett., 1990, 31, 5509; (c) E. V. Starodubtseva and V. A. Ferapontov, Russ. Chem. Bull., 2005, 54, 2374; (d) H. Mehdi, A. Bodor, R. Tuba and I. T. Horváth, Abstr. Paper. Am. Chem. Soc., 2003, 226, U721; (e) C. Delhomme and L. A. Schaper, J. Organomet. Chem., 2013, 724, 297; (f) M. Chalid, A. A. Broekhuis and H. J. Heeres, J. Mol. Catal. A: Chem., 2011, 341, 14; (g) B. Y. Tay, C. Wang, P. H. Phua, L. P. Stubbs and H. V. Huynh, Dalton Trans., 2016, 45, 3558.
10. (a) J. Ftouni, A. Muñoz-Murillo, A. Goryachev, J. P. Hofmann, E. J. M. Hensen, L. Lu, C. J. Kiely, P. C. A. Bruijnincx and B. M. Weckhuysen, ACS Catal., 2016, 6, 5462; (b) Z. P. Yan, L. Lin and S. J. Liu, Energy Fuels, 2009, 23, 3853; (c) S. G. Wettstein, J. Q. Bond, D. M. Alonso, H. N. Pham, A. K. Datye and J. A. Dumesic, Appl. Catal., B, 2012, 117–118, 321; (d) X. C. Kang, W. T. Shang, Q. G. Zhu, J. L. Zhang, T. Jiang, B. X. Han, Z. H. Wu, Z. H. Li and X. Q. Xing, Chem. Sci., 2015, 6, 1668; (e) K. Yan, T. Lafleur, G. S. Wu, J. Y. Liao, C. Ceng and X. M. Xie, Appl. Catal., A, 2013, 468, 52; (f) M. Sudhakar, V. Vijay Kumar, G. Naresh, M. L. Kantam, S. K. Bhargava and A. Venugopala, Appl. Catal., B, 2016, 180, 113; (g) A. S. Piskun, J. E. de Haan, E. Wilbers, H. H. van de Bovenkamp, Z. Tang and H. J. Heeres, ACS Sustainable Chem. Eng., 2016, 4, 2939; (h) C. X. Xiao, T. W. Goh, Z. Y. Qi, S. Goes, K. Brashler, C. Perez and W. Y. Huang, ACS Catal., 2016, 6, 593; (i) Y. Kubo, D. Kakizaki, M. Kogo and Y. Magatani, Supramol. Chem., 2016, 28, 91; (j) Z. P. Yan, L. Lin and S. J. Liu, Energy Fuels, 2009, 23, 3853; (k) J. J. Tan, J. L. Cui, G. Q. Ding, T. S. Deng, Y. L. Zhu and Y. W. Li, Catal. Sci. Technol., 2016, 6, 1469; (l) J. L. Cui, J. J. Tan, T. S. Deng, X. J. Cui, H. Y. Zheng, Y. L. Zhu and Y. W. Li, Green Chem., 2015, 17, 3084; (m) J. J. Tan, J. L. Cui, T. S. Deng, X. J. Cui, G. Q. Ding, Y. L. Zhu and Y. W. Li, ChemCatChem, 2015, 7, 508; (n) Y. Y. Guo, Y. L. Li, J. Z. Chen and L. M. Chen, Catal. Lett., 2016, 146(10), 2041.
11. (a) A. M. Ruppert, M. Jędrzejczyk, O. Sneka-Płatek, N. Keller, A. S. Dumon, C. Michel, P. Sautet and J. Grams, Green Chem., 2016, 18, 2014; (b) B. Banerjee, R. Singuru, S. K. Kundu, K. Dhanalaxmi, L. Y. Bai, Y. L. Zhao, B. M. Reddy, A. Bhaumik and J. Mondal, Catal. Sci. Technol., 2016, 6, 5102; (c) M. Varkolu, V. Velpula, D. R. Burri and S. R. R. Kamaraju, New J. Chem., 2016, 40, 3261; (d) R. R. Gowda and E. Y.-X. Chen, ChemSusChem, 2016, 9, 181; (e) X. L. Du, Q. Y. Bi, Y. M. Liu, Y. Cao and K. N. Fan, ChemSusChem, 2011, 4, 1838.
12. (a) H. Mehdi, V. Fábos, R. Tuba, A. Bodor, L. T. Mika and I. T. Horváth, Top. Catal., 2008, 48, 49; (b) J. M. Tukacs, D. Király and G. Dibó, Green Chem., 2012, 14, 2057; (c) L. Deng, J. Li, D. M. Lai, Y. Fu and Q. X. Guo, Angew. Chem., Int. Ed., 2009, 121, 6651.
13. (a) M. C. Fu, R. Shang, Z. Huang and Y. Fu, Synlett, 2014, 25, 2748; (b) J. Deng, Y. Wang, T. Pan, Q. Xu, Q. X. Guo and Y. Fu, ChemSusChem, 2013, 6, 1163.
14. Z. Yang, Y. Fu and Q. X. Guo, Chin. J. Org. Chem., 2015, 35, 273.
15. L. Deng, Y. Zhao, J. A. Li, Y. Fu, B. Liao and Q. X. Guo, ChemSusChem, 2010, 3, 1172.
16. (a) X. L. Du, L. He, S. Zhao, Y. M. Liu, Y. Cao, H. Y. He and K. N. Fan, Angew. Chem., Int. Ed., 2011, 50, 7815; (b) A. M. Hengne, A. V. Malawadkar, N. S. Biradar and C. V. Rode, RSC Adv., 2014, 4, 9730; (c) A. M. Hengne and C. V. Rode, Green Chem., 2012, 14, 1064; (d) B. Putrakumar, N. Nagaraju, V. P. Umar and K. V. R. Chary, Catal. Today, 2015, 250, 209; (e) P. Balla, V. Perupogu, P. K. Vanama and V. C. Komandur, J. Chem. Technol. Biotechnol., 2016, 91, 769; (f) Q. Xu, X. L. Li, T. Pan, C. G. Yu, J. Deng, Q. X. Guo and Y. Fu, Green Chem., 2016, 18, 1287; (g) V. V. Kumar, G. Naresh, M. Sudhakar, C. Anjaneyulu, S. K. Bhargava, J. Tardio, V. K. Reddy, A. H. Padmasri and A. Venugopal, RSC Adv., 2016, 6, 9872; (h) J. Fu, D. Sheng and X. Y. Lu, Catalysts, 2016, 6, 6; (i) A. M. Hengne, B. S. Kadu, N. S. Biradar, R. C. Chikate and C. V. Rode, RSC Adv., 2016, 6, 59753; (j) V. Mohan, V. Venkateshwarlu, C. V. Pramod, B. D. Raju and K. S. R. Rao, Catal. Sci. Technol., 2014, 4, 1253; (k) V. Molinari, M. Antonietti and D. Esposito, Catal. Sci. Technol., 2014, 4, 3626; (l) K. Jiang, D. Sheng, Z. H. Zhang, J. Fu, Z. Y. Hou and X. Y. Lu, Catal. Today, 2016, 274, 55; (m) H. C. Zhou, J. L. Song, H. L. Fan, B. B. Zhang, Y. Y. Yang, J. Y. Hu, Q. G. Zhu and B. X. Han, Green Chem., 2014, 16, 3870; (n) J. Zhang, J. Z. Chen, Y. Y. Guo and L. M. Chen, ACS Sustainable Chem. Eng., 2015, 3, 1708.
17. (a) M. G. Al-Shaal, W. R. H. Wright and R. Palkovits, Green Chem., 2012, 14, 1260; (b) S. Saravanamurugan and A. Riisager, Catal. Commun., 2012, 17, 71; (c) S. Saravanamurugan, O. N. Van Buu and A. Riisager, ChemSusChem, 2011, 4, 723.
18. (a) J. M. Nadgeri, N. Hiyoshi, A. Yamaguchi, O. Sato and M. Shirai, Appl. Catal., A, 2014, 470, 215; (b) F. Y. Ye, D. M. Zhang, T. Xue, Y. M. Wang and Y. J. Guan, Green Chem., 2014, 16, 3951; (c) J. L. Zheng, J. H. Zhu, X. Xu, W. M. Wang, J. W. Li, Y. Zhao, K. J. Tang, Q. Song, X. L. Qi, D. J. Kong and Y. Tang, Sci. Rep., 2016, 6, 28898; (d) H. Li, Z. Fang and S. Yang, ChemPlusChem, 2016, 81, 135; (e) F. Y. Ye, D. M. Zhang, T. Xue, Y. M. Wang and Y. J. Guan, Green Chem., 2014, 16, 3951.
19. (a) M. Chia and J. A. Dumesic, Chem. Commun., 2011, 47, 12233; (b) X. Tang, L. Hu, Y. Sun, G. Zhao, W. W. Hao and L. Lin, RSC Adv., 2013, 3, 10277; (c) J. Wang, S. Jaenicke and G.-K. Chuah, RSC Adv., 2014, 4, 13481; (d) L. Bui, H. Luo, W. R. Gunther and Y. Román-Leshkov, Angew. Chem., Int. Ed., 2013, 52, 8022; (e) J. Wang, S. Jaenicke and G.-K. Chuah, RSC Adv., 2014, 4, 13481; (f) J. L. Song, L. Q. Wu, B. W. Zhou, H. C. Zhou, H. L. Fan, Y. Y. Yang, Q. L. Meng and B. X. Han, Green Chem., 2015, 17, 1626; (g) Y. Kuwahara, W. Kaburagi and T. Fujitani, RSC Adv., 2014, 4, 45848; (h) X. Tang, X. H. Zeng, Z. Li, W. F. Li, Y. T. Jiang, L. Hu, S. J. Liu, Y. Sun and L. Lin, ChemCatChem, 2015, 7, 1372; (i) X. Tang, H. W. Chen, L. Hu, W. W. Hao, Y. Sun, X. H. Zeng, L. Lin and S. J. Liu, Appl. Catal., B, 2014, 147, 827; (j) H. Li, Z. Fang and S. Yang, ACS Sustainable Chem. Eng., 2016, 4, 236; (k) A. H. Valekar, K.-H. Cho, S. K. Chitale, D. Y. Hong, G. Y. Cha, U.-H. Lee, D. W. Hwang, C. Serre, J. S. Chang and Y. K. Hwang, Green Chem., 2016, 18, 4542; (l) H. Li, Z. Fang and S. Yang, ChemPlusChem, 2016, 81, 135; (m) H. Y. Luo, D. F. Consoli, W. R. Gunther and Y. Román-Leshkov, J. Catal., 2014, 320, 198; (n) Y. Q. Yang, X. L. Xu, W. J. Zou, H. J. Yue, G. Tian and S. H. Feng, Catal. Commun., 2016, 76, 50.
20. Z. Yang, Y. B. Huang, Q. X. Guo and Y. Fu, Chem. Commun., 2013, 49, 5328.
21. (a) E. Taarning, C. M. Osmundsen, X. B. Yang, B. Voss, S. I. Andersen and C. H. Christensena, Energy Environ. Sci., 2011, 4, 793; (b) C. T. Wang, L. Wang, J. Zhang, H. Wang, J. P. Lewis and F. S. Xiao, J. Am. Chem. Soc., 2016, 138, 7880.
22. (a) Y. T. Cheng, Z. P. Wang, C. J. Gilbert, W. Fan and G. W. Huber, Angew. Chem., Int. Ed., 2012, 51, 11097; (b) C. L. Williams, C.-C. Chang, P. Do, N. Nikbin, S. Caratzoulas, D. G. Vlachos, R. F. Lobo, W. Fan and P. J. Dauenhauer, ACS Catal., 2012, 2, 935; (c) C.-C. Chang, H. J. Cho, J. Y. Yu, R. J. Gorte, J. Gulbinski, P. Dauenhauer and W. Fan, Green Chem., 2016, 18, 1368; (d) C. L. Williams, K. P. Vinter, C.-C. Chang, R. Xiong, S. K. Green, S. I. Sandler, D. G. Vlachos, W. Fan and P. J. Dauenhauer, Catal. Sci. Technol., 2016, 6, 178; (e) C. L. Williams, K. P. Vinter, R. E. Patet, C.-C. Chang, N. Nikbin, S. T. Feng, M. R. Wiatrowski, S. Caratzoulas, W. Fan, D. G. Vlachos and P. J. Dauenhauer, ACS Catal., 2016, 6, 2076.
23. (a) S. L. Lawton, A. S. Fung, G. J. Kennedy, L. B. Alemany, C. D. Chang, G. H. Hatzikos, D. N. Lissy, M. K. Rubin, H.-K. C. Timken, S. Steuernagel and D. E. Woessner, J. Phys. Chem., 1996, 100, 3788; (b) K. Suzuki, T. Nishio, N. Katada, G. Sastre and M. Niwa, Phys. Chem. Chem. Phys., 2011, 13, 3311; (c) X. J. Li, X. H. Liu, S. L. Liu, S. J. Xie, X. X. Zhu, F. C. Chen and L. Y. Xu, RSC Adv., 2013, 3, 16549; (d) F. M. Zhang, X. Chen, J. Zhuang, Q. Xiao, Y. J. Zhong and W. D. Zhu, Catal. Sci. Technol., 2011, 1, 1250; (e) A. S. Kovo, O. Hernandez and S. M. Holmes, J. Mater. Chem., 2009, 19, 6207; (f) M. Banu, Y. H. Lee, G. Magesh and J. S. Lee, Catal. Sci. Technol., 2014, 4, 120; (g) S. M. Solyman, N. A. K. Aboul-Gheit, F. M. Tawfik, M. Sadek and H. A. Ahmed, Egypt. J. Pet., 2013, 22, 99; (h) V. Brahmkhatri and A. Patel, Green Chem. Lett. Rev., 2012, 5, 161; (i) Y. Li, Q. Mi and Z. H. Xue, J. Inorg. Mater., 2016, 31, 694; (j) P. Z. Chen, S. Y. Huang, J. J. Zhang, S. P. Wang and X. B. Ma, Front. Chem. Sci. Eng., 2015, 9, 224.
24. G. H. Wang, J. Hilgert, F. H. Richter, F. Wang, H.-J. Bongard, B. Splietho, C. Weidenthaler and F. Schüth, Nat. Mater., 2014, 13, 293.
25. L. H. Nie, A. Y. Meng, J. G. Yu and M. Jaroniec, Sci. Rep., 2013, 3, 3215.
26. (a) M. Y. Chen, C. B. Chen, B. Zada and Y. Fu, Green Chem., 2016, 18, 3858; (b) P. P. Yang, Q. Q. Cui, Y. H. Zu, X. H. Liu, G. Z. Lu and Y. Q. Wang, Catal. Commun., 2015, 66, 55; (c) Y. F. Zhu, X. Kong, H. Y. Zheng, G. Q. Ding, Y. L. Zhu and Y. W. Li, Catal. Sci. Technol., 2015, 5, 4208; (d) J. Jae, W. Zheng, R. F. Lobo and D. G. Vlachos, ChemSusChem, 2013, 6, 1158; (e) X. Kong, R. Zheng, Y. Zhu, G. Ding, Y. Zhu and Y.-W. Li, Green Chem., 2015, 17, 2504.

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Footnotes

† Electronic supplementary information (ESI) available. See DOI: 10.1039/c6ra24323a

‡ These authors equally contributed to the work.

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