Preparation and characterization of a strong solid base from waste eggshell for biodiesel production

Preparation and characterization of a strong solid base from waste eggshell for biodiesel production

G Model JECE 550 1–5 Journal of Environmental Chemical Engineering xxx (2015) xxx–xxx Contents lists available at ScienceDirect Journal of Environm...

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G Model

JECE 550 1–5 Journal of Environmental Chemical Engineering xxx (2015) xxx–xxx

Contents lists available at ScienceDirect

Journal of Environmental Chemical Engineering journal homepage: www.elsevier.com/locate/jece

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Preparation and characterization of a strong solid base from waste eggshell for biodiesel production Danlin Zeng * , Qi Zhang, Shiyuan Chen, Shenglan Liu, Yang Chen, Yongsheng Tian, Guanghui Wang The State Key Laboratory of Refractories and Metallurgy, Hubei Key Laboratory of Coal Conversion and New Carbon Material, College of Chemical Engineering and Technology, Wuhan University of Science and Technology, Wuhan 430081, China

A R T I C L E I N F O

A B S T R A C T

Article history: Received 10 November 2014 Accepted 28 January 2015

A strong solid base catalyst was prepared from waste eggshell by KF modification and thermal treatment. The eggshell catalyst was characterized by Fourier-transform infrared spectra (FT-IR), X-ray diffraction (XRD), scanning electron microscope (SEM) and solid-state nuclear magnetic resonance (NMR) spectroscopy. The characterization results show that potassium hydroxide (KOH) formed from the modification process enhances the basicity and catalytic ability of the catalyst. The solid base catalyst from eggshell (SBES) exhibits excellent catalytic activity and stability in the transesterification reaction, which suggested that this catalyst would be potentially used as a solid base catalyst for biodiesel production. ã 2015 Published by Elsevier Ltd.

Keywords: Solid base Waste eggshell Biodiesel Basicity

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Introduction Eggshells are one of the vast by-products of food processing and manufacturing plants. Most of the waste eggshells are currently stockpiled on-site without any pretreatment. In addition, the emission of odor gas during its biodegradation seriously polluted the environment [1]. Thus, significant attentions were given to the recycling of these waste eggshells. Some researchers reported that the waste eggshell was used to prepare calcium phosphate bioceramics and a low-cost adsorbent for removal of ionic pollutant from the aqueous solution [2,3]. However, few papers have been reported to prepare solid base catalyst using the waste eggshell [4]. For the increasing price of petroleum and the environmental concerns, recyclable and environmental benign energy sources have been widely developed all over the world, in which biodiesel is one of the most promising fuel substitute in the future. As reported, biodiesel has already been commercially produced from renewable resources such as soybean oil by transesterification reaction using homogeneous strong bases or acids as catalysts [5–7]. Although the homogeneous base catalysts can catalyze biodiesel production with the fast reaction speed under mild reaction conditions, it still shows some disadvantages in the practical process. For example, it is hard to separate catalyst from

* Corresponding author. Tel.: +86 2768862181. E-mail address: zdanly[email protected] (D. Zeng).

product [8]. Therefore, many attentions were focused on the solid base catalyst due to its convenience in separation and recycling [9]. The chemical composition of waste eggshell is mainly calcium carbonate as reported by other researcher [10]. Due to its intrinsic pore structure in eggshell surface and the amount in abundance, eggshell is a good raw material for the preparation of fine powder, which might pave the way for its utilization such as porous solid catalyst. In fact, the solid base catalysts derived from eggshell have been reported and prepared by calcinations [4,11,12], the base Q3 strength of those catalysts is not strong enough and subsequently show relatively low activity in the application. Hence, the key questions in these catalysts, such as what method and which mechanism can improve their base strength and further to increase their catalytic activity, are still poorly understood. In this study, a strong solid base catalyst from waste eggshell (SBES) was prepared with chemical and thermal treatment. In addition, this solid base catalyst was also characterized by X-ray diffraction (XRD), Fouriertransform infrared spectra (FT-IR), temperature programmed desorption (TPD), scanning electron microscope (SEM) and solidstate nuclear magnetic resonance (NMR) spectroscopy.

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Experimental

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Sample preparation

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The waste eggshell sample was collected from a canteen of Wuhan University of Science and Technology. The eggshells were washed for three times, and then dried at 120  C for 10 h. The dried

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http://dx.doi.org/10.1016/j.jece.2015.01.014 2213-3437/ ã 2015 Published by Elsevier Ltd.

Please cite this article in press as: D. Zeng, et al., Preparation and characterization of a strong solid base from waste eggshell for biodiesel production, J. Environ. Chem. Eng. (2015), http://dx.doi.org/10.1016/j.jece.2015.01.014

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eggshells were crushed and sieved to the particle size range of 100–150 mm. Particle size analysis was performed by dry sieving with Taylor standard sieves. The solid base catalyst from eggshell was prepared by KF modification and thermal treatment. Typically, 10.0 g of eggshell was immersed in 20 ml KF solution with the designed amount of KF for 5 h, then baked at 120  C for 10 h, followed by calcination at the designed temperature for 12 h in a muffle furnace. The obtained catalyst was preserved in an airtight plastic bottle for further using. The catalyst with KF loading of 25 wt% and calcinations at 800  C was chosen for all the sample characterization. CaO (from eggshell) Q4 was prepared by calcination of the dried eggshell at 800  C for 12 h. CaO (commercial) and MgO (commercial) were purchased from Shanghai Guoyao Company. NaY catalysts were prepared by ion-exchange method using HY (Si/Al = 80, from Nankai University) as the starting material [13]. The ion-exchange process was carried out at 358 K using 100 ml NaOH solution (0.2 M) to exchange 10 g HY zeolite for 0.5 h. After the ion-exchange, the sample was washed thoroughly with deionized water, filtered, dried at 393 K overnight and then calcined in air at 823 K for 10 h. Food-grade soybean oil supplied by commercial supermarket was used to carry out the transesterification reaction. The oil was purified and dried carefully before the catalytic test. According to GC (HP6890) analysis, the fatty acid compositions of the used soybean oil were as follows: palmitic acid, 12.6%; stearic acid, 5.8%; oleic acid, 26.7%; linoleic acid, 48.8%; and linolenic acid, 6.4%. The acid value of the oil was reduced to lower than 0.3 mg KOH/g and the water content below 10 ppm. The average molecular weight of the oil is 850. Sample characterization Surface area and porosity properties of the samples were obtained by N2 adsorption/desorption isotherms on a Micromeritics ASAP 2020 sorption analyzer. The amount of the basic site in the catalyst (Total basicity in Table 1) was determined by the indicator method [14]. The FT-IR spectra were performed on Impact 410, Nicolet Spectrometer with a resolution of 2 cm1. X-ray diffraction was recorded with a Philips X’PERT-Pro-MPD diffractometer. The morphologies and dimensions of the samples were characterized by scanning electron microscope (SEM; Philips XL30). Q5 The basic properties of the catalysts were characterized by the temperature programmed desorption (TPD) of CO2 measurement using a Micromeritics AutoChem II 2920 chemisorption analyzer. The 19F NMR spectra were recorded on a Varian Infinityplus400 spectrometer.

Catalytic reaction procedure

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Transesterification reaction of soybean oil and methanol was performed as follows: at first, a 100 ml round-bottom flask was charged with 30.0 g of soybean oil (34.5 mmol, calculated from the average molecular weight of the rapeseed oil), 12.6 ml methanol and the eggshell catalyst. The mixture was stirred by a magnetic stirrer. All the transesterification reactions were performed under reflux with a water-cooled condenser. After the transesterification reaction was finished, the mixture was cooled in air and placed into a separation funnel, and then the mixture of the glycerol and methanol was separated. The oil phase FAME (fatty acids methyl esters, biodiesel) was quantitative analyzed in the presence of methyl salicylate as internal standard by HP6890 GC with a flame ionization detector (FID). The biodiesel yield was defined as a ratio of the actual weight of FAME (by HP6890 GC) to the theoretical weight of FAME (by calculation on the basis of soybean oil used in the reaction). Repeated experiments of the transesterification reaction were performed to determine the catalytic stability of the catalyst. The catalyst was centrifuged from the mixture, and then directly used for the next cycle. The reaction conditions were used in each cycle as follows: catalyst/oil mass ratio: 2%; methanol/oil molar ratio: 12:1; reaction temperature: 65  C; reaction time 2 h.

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Results and discussion

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Catalyst characterization

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Fig. 1 shows FT-IR spectra of SBES catalyst and eggshell. The strong peak at 1417 cm1 was attributed to carbonate minerals in eggshell [15]. Other two observable peaks at 712 and 875 cm1 were associated with the in-plane deformation and out-plane deformation modes of carbonate groups, respectively [15]. The band at 1390 cm1 in the spectrum of SBES catalyst was assigned to molecular CO2 adsorbed by the basic hydroxyl groups in the catalyst [16]. While no such peak appears in the spectrum of eggshell, which indicated that basic hydroxyl groups was generated via the reaction of KF and CaCO3 by calcination. Fig. 2 illustrates the XRD patterns of the SBES catalyst and eggshell. The diffraction peaks at 29.4 , 36.3 , 43.2 , 47.3 and 48.5 in eggshell spectrum are ascribed to CaCO3 in the eggshell [10]. While in the spectrum of SBES catalyst, the typical peaks at 18.2 , 28.2 , 32.3 , 35.8 and 62.1 are attributed to CaO derived from CaCO3 in the eggshell by calcination [10]. The peaks (19.9 , 40.1, 50.8 , 59.9 and 65.8 ) arising from the crystal of KCaF3 can also be clearly observed, further indicative of occurrence of the reaction between KF and CaCO3 during the calcination process [17,18].

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Table 1 Textural properties and the catalytic performance of the various solid bases. Catalysts

SBET (m2/g)

Vtot (cm3/g)

Total basicity (mmol/g)

Yield (%)

SBES CaO (from eggshell) CaO (commercial) MgO (commercial) NaY

19.96 13.56 11.63 16.35 143.26

0.046 0.034 0.029 0.039 0.087

1.65 0.82 0.88 1.23 0.98

99.1 95.2 93.6 94.2 93.2

SBET, specific surface area from BET method; Vtot, total pore volume. Reaction condition: Catalyst/oil mass ratio: 2%; methanol/oil molar ratio: 12:1; reaction temperature: 65  C, reaction time 2 h.

Fig. 1. FT-IR spectra of (a) eggshell and (b) the SBES catalyst.

Please cite this article in press as: D. Zeng, et al., Preparation and characterization of a strong solid base from waste eggshell for biodiesel production, J. Environ. Chem. Eng. (2015), http://dx.doi.org/10.1016/j.jece.2015.01.014

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Fig. 2. XRD patterns of the (a) eggshell and (b) SBES catalyst. #, !, 5 denote peaks of KCaF3, CaCO3 and CaO, respectively. 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161

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The F single pulse MAS NMR spectrum of SBES catalyst (after calcination), SBES catalyst (before calcination) and pure KF are shown in Fig. 3. The strong signal at 124 ppm in the spectra of SBES catalyst before calcination can be assigned to the KF crystal in the sample [19]. According to the literature, the relatively weak signal at 159 ppm is ascribed to the KCaF3 species that is formed by the reaction of KF with CaCO3 in the eggshell (Fig. 3b) [19,20]. After calcination, the intensity of the signal arising from KCaF3 obviously increases while the signal of KF disappears in the spectra of SBES catalyst (Fig. 3a), which indicated that KF was completely reacted in the calcination process. Thus, based on the FT-IR, XRD and 19F single pulse MAS NMR characterization results, we can infer that KOH and KCaF3 are generated by the reaction of KF with CaO during the sample calcination (Eqs. (1) and (2)). 3KF + CaO = KCaF3 + K2O

(1)

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K2O + H2O = 2KOH

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Fig. 4 shows the TPD profiles of carbon dioxide from the SBES catalyst, eggshell and CaO (commercial). Generally, the high temperature desorption of carbon dioxide results in the strong basicity of the solid base catalysts. The peak at 710  C can be clearly observed in the TPD profiles of all the three samples, which arise from CaO in the samples [21]. Compared with CaO and eggshell, a relatively strong desorption peak at 725  C was also observed in Fig. 4a which indicated that the strength of the basic sites in the

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(2)

Fig. 3. 19F single pulse MAS NMR spectrum of (a) SBES catalyst (after calcination), (b) SBES catalyst (before calcination) and (c) pure KF. The asterisk denotes spinning sidebands.

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Fig. 4. TPD profiles of carbon dioxide from (a) SBES catalyst, (b) eggshell and (c) CaO (commercial).

SBES catalyst is stronger than that of CaO. The characterization results have confirmed the existence of KOH in the catalyst; therefore, these relatively strong basic sites result from the new formed KOH by the reaction of KF with CaCO3. Fig. 5 depicts SEM images of dried eggshell and SBES catalyst. Before calcination, eggshell shows a generally irregular crystal structure. Many pores and pits were distributed over the entire eggshell surface. After calcination at 800  C for 5 h, as shown in Fig. 5b, the crystal structure has been changed and more developed pores are observed, indicative of dramatic increasing in the BET surface area of the SBES catalyst.

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Catalytic reaction

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Effects of preparation conditions on catalytic activity To investigate the effect of the KF loading on biodiesel yield, the transesterification reactions were performed using the SBES catalysts with different KF loading (calcined at 800  C for 12 h). As shown in Fig. 6a, the biodiesel yields increase from 20.3% to 99.1% when the KF loading increases from 10 wt% to 25 wt%. From the above characterization results, it can be concluded that the active sites in the SBES catalysts increase with increasing the KF loading. While when the KF loading is further increased (beyond 25 wt%), the excessive KF will cover the active sites in the catalyst surface [22], which will lead to the biodiesel yield decrease. Therefore, the optimum KF loading of the SBES catalyst is 25 wt%. Calcination temperature is also an important factor on the catalyst activity (Fig. 6b). The reaction of CaO in the eggshell and KF requires calcination process at relatively higher temperature to form some active sites in the catalyst, but on the other side, too higher calcination temperature will reduce the surface area of the catalyst for surface species sintering [23]. Thus, the best calcination temperature in this case is 800  C.

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Activity and stability of the catalyst Table 1 shows the catalytic performance of the transesterification reaction on the various solid base catalysts under the same reaction conditions. Compared with CaO (calcined from eggshell), CaO (commercial), MgO (commercial) and NaY (Si/Al = 80) zeolite [13,24], the SBES catalyst with stronger base strength shows higher biodiesel yield, which is almost similar to that of the homogeneous catalytic system [25]. A comparative study was also made between the SBES catalyst and other typical solid base catalysts. As it can be seen from Fig. 7, the SBES catalyst can be reusable at least 10 times with a nearly 17% conversion drop from 99.1% yield (first time) to 81.1% yield (tenth time). Meanwhile, the biodiesel yield decreases

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Fig. 5. SEM images of (a) dried eggshell and (b) SBES catalyst.

Fig. 6. Effects of (a) KF loading; (b) calcination temperature on activity of the SBES catalyst. Reaction condition: Catalyst/oil mass ratio: 2%; methanol/oil molar ratio: 12:1; reaction temperature: 65  C, reaction time 2 h. 214 215 216 217 218 219

to below 70.0% after 10 times using for CaO (from eggshell) and CaO (commercial), MgO (commercial) and NaY catalysts. The total basicity of the SBES catalyst is 1.65 mmol/g, which is higher than other typical solid base catalysts, therefore, the SBES catalyst shows better catalytic stability than other catalysts under the same reaction condition.

Fig. 7. Effects of repeated use of the SBES catalyst, CaO (E) (CaO from eggshell), MgO (C) (MgO from commercial), CaO(C) (CaO from commercial) and NaY zeolite on biodiesel yield. Catalyst/oil mass ratio: 2%; methanol/oil molar ratio: 12:1; reaction temperature: 65  C; reaction time 2 h.

The chemical stability of the catalysts was carried out by analysis the Ca2+ concentration in the mixture of the glycerol and methanol with atomic emission spectrometry. The results display that Ca2+ concentration in the mixture is 12, 58 and 72 mg/l for SBES, CaO (from eggshell) and CaO (commercial), respectively. The minima leaching Ca2+ concentration of the SBES catalyst reveals that this catalyst is more stable than other two catalysts. Hu et al. [26] reported that the new formed KCaF3 improve the chemical stability of the catalyst, which is in agreement with our findings. In addition, the spent SBES catalyst can be regenerated by calcination at 800  C for 12 h. Based on the above characterization, it can be concluded that the SBES catalyst from the waste eggshell exhibit excellent catalytic activity and stability under the test conditions employed. Hence, this kind of non-toxic, easy preparation and recyclable catalyst appears to be one of the promising solid base catalysts for biodiesel production.

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Conclusions

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In summary, a solid base catalyst was prepared from waste eggshell by KF modification and thermal treatment. The prepared solid acid was characterized by XRD, FT-IR, SEM and solid-state NMR spectroscopy. The characterization results show that the catalyst exhibits stronger basicity than that of CaO. KOH generated in the modification process enhances the basicity and catalytic ability of the catalyst. The SBES catalyst from waste eggshell exhibits excellent catalytic activity and stability in the transesterification reaction.

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Thus, this green solid base catalyst maybe widely used for bidiesel production in chemical industry.

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Acknowledgments

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We acknowledge the financial supports from the National Natural Science Foundation of China (21473126), the Fund of Hubei Provincial Department of Education (B2014094) and the Open Research Fund of Hubei Province Key Laboratory of Coal Conversion and New Carbon Material (WKDM2013010).

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References

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[12]

[13]

[14]

[15]

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[1] W.T. Tsai, K.J. Hsien, H.C. Hsu, C.M. Lin, K.Y. Lin, C.H. Chiu, Utilization of ground eggshell waste as an adsorbent for the removal of dyes from aqueous solution, Bioresour. Technol. 99 (6) (2008) 1623–1629, doi:http://dx.doi.org/10.1016/j. biortech.2007.04.010. 17543519. [2] C. Balázsi, F. Wéber, Z. Kövér, E. Horváth, C. Németh, Preparation of calcium– phosphate bioceramics from natural resources, J. Eur. Ceram. Soc. 27 (2–3) (2007) 1601–1606, doi:http://dx.doi.org/10.1016/j.jeurceramsoc.2006.04.016. [3] W. Zheng, X.M. Li, Q. Yang, G.M. Zeng, X.X. Shen, Y. Zhang, J.J. Liu, Adsorption of Cd(II) and Cu(II) from aqueous solution by carbonate hydroxylapatite derived from eggshell waste, J. Hazard. Mater. 147 (2007) 534–539, doi:http://dx.doi. org/10.1016/j.jhazmat.2007.01.048. 17368932. [4] Z. Wei, C. Xu, B. Li, Application of waste eggshell as low-cost solid catalyst for biodiesel production, Bioresour. Technol. 100 (11) (2009) 2883–2885, doi: http://dx.doi.org/10.1016/j.biortech.2008.12.039. 19201602. [5] G. Vicente, M. Martínez, J. Aracil, Integrated biodiesel production: a comparison of different homogeneous catalysts systems, Bioresour. Technol. 92 (3) 297–305, doi:http://dx.doi.org/10.1016/j.biortech.2003.08.014. (2004) 14766164. [6] M.D. Serio, R. Tesser, M. Dimiccoli, F. Cammarota, M. Nastasi, E. Santacesaria, Synthesis of biodiesel via homogeneous Lewis acid catalyst, J. Mol. Catal. A Chem. 239 (2005) 111–115. [7] P. Morin, B. Hamad, G. Sapaly, M.G. Carneiro Rocha, P.G. Pries de Oliveira, W.A. Gonzalez, E. Andrade Sales, N. Essayem, Transesterification of rapeseed oil with ethanol: I. Catalysis with homogeneous Keggin heteropoly acids, Appl. Catal. A Gen. 330 (2007) 69–76, doi:http://dx.doi.org/10.1016/j. apcata.2007.07.011. [8] H. Bai, X. Shen, X. Liu, S. Liu, Synthesis of porous CaO microsphere and its application in catalyzing transesterification reaction for biodiesel, Trans. Nonferrous Met. Soc. China 19 (2009) s674–s677, doi:http://dx.doi.org/ 10.1016/S1003-6326(10)60130-6. [9] A.P.S. Chouhan, A.K. Sarma, Modern heterogeneous catalysts for biodiesel production: a comprehensive review, Renew. Sust. Energy Rev. 15 (9) (2011) 4378–4399, doi:http://dx.doi.org/10.1016/j.rser.2011.07.112. [10] T. Witoon, Characterization of calcium oxide derived from waste eggshell and its application as CO2 sorbent, Ceram. Int. 37 (8) (2011) 3291–3298, doi:http:// dx.doi.org/10.1016/j.ceramint.2011.05.125. [11] N. Viriya-empikul, P. Krasae, B. Puttasawat, B. Yoosuk, N. Chollacoop, K. Faungnawakij, Waste shells of mollusk and egg as biodiesel production catalysts,

[16]

[17]

[18]

[19]

[20]

[21]

[22]

[23]

[24]

[25] [26]

5

Bioresour. Technol. 101 (10) (2010) 3765–3767, doi:http://dx.doi.org/10.1016/j. biortech.2009.12.079. 20079632. P. Khemthong, C. Luadthong, W. Nualpaeng, P. Changsuwan, P. Tongprem, N. Viriya-empikul, K. Faungnawakij, Industrial eggshell wastes as the heterogeneous catalysts for microwave-assisted biodiesel production, Catal. Today 190 (1) (2012) 112–116, doi:http://dx.doi.org/10.1016/j.cattod.2011.12.024. Y.Y. Wang, H.Y. Chou, B.H. Chen, D.J. Lee, Optimization of sodium loading on zeolite support for catalyzed transesterification of triolein with methanol, Bioresour. Technol. 145 (2013) 248–253, doi:http://dx.doi.org/10.1016/j. biortech.2012.12.185. 23374749. J. Zhu, Y. Chun, Y. Wang, Q. Xu, Attempts to create new shape-selective solid strong base catalysts, Catal. Today 51 (1999) 103–111, doi:http://dx.doi.org/ 10.1016/S0920-5861(99)00012-7. W.T. Tsai, J.M. Yang, C.W. Lai, Y.H. Cheng, C.C. Lin, C.W. Yeh, Characterization and adsorption properties of eggshells and eggshell membrane, Bioresour. Technol. 97 (3) (2006) 488–493, doi:http://dx.doi.org/10.1016/j.biortech.2005.02.050. 15896954. R. Bal, B.B. Tope, T.K. Das, S.G. Hegde, S. Sivasanker, Alkali-loaded silica, a solid base: investigation by FTIR spectroscopy of adsorbed CO2 and its catalytic activity, J. Catal. 204 (2) (2001) 358–363, doi:http://dx.doi.org/10.1006/ jcat.2001.3402. H. Liu, L. Su, Y. Shao, L. Zou, Biodiesel production catalyzed by cinder supported Cao/KF particle catalyst, Fuel 97 (2012) 651–657, doi:http://dx.doi.org/10.1016/ j.fuel.2012.02.002. L. Gao, G. Teng, G. Xiao, R. Wei, Biodiesel from palm oil via loading KF/Ca–Al hydrotalcite catalyst, Biomass Bioenergy 34 (9) (2010) 1283–1288, doi:http:// dx.doi.org/10.1016/j.biombioe.2010.03.023. H. Kabashima, H. Tsuji, S. Nakata, Y. Tanaka, H. Hattori, Activity for basecatalyzed reactions and characterization of alumina-supported KF catalysts, Appl. Catal. A Gen. 194–195 (2000) 227–240, doi:http://dx.doi.org/10.1016/ S0926-860X(99)00370-1. M. Body, G. Silly, C. Legein, J.Y. Buzaré, Cluster models and ab initio calculations of (19)F NMR isotropic chemical shifts for inorganic fluorides, J. Phys. Chem. B 109 (20) (2005) 10270–10278, doi:http://dx.doi.org/10.1021/jp046763g. 16852244. Y.B. Cho, G. Seo, High activity of acid-treated quail eggshell catalysts in the transesterification of palm oil with methanol, Bioresour. Technol. 101 (22) (2010) 8515–8519, doi:http://dx.doi.org/10.1016/j.biortech.2010.06.082. 20621469. L. Wen, Y. Wang, D. Lu, S. Hu, H. Han, Preparation of KF/CaO nanocatalyst and its application in biodiesel production from Chinese tallow seed oil, Fuel 89 (9) (2010) 2267–2271, doi:http://dx.doi.org/10.1016/j.fuel.2010.01.028. M. Kouzu, T. Kasuno, M. Tajika, Y. Sugimoto, S. Yamanaka, J. Hidaka, Calcium oxide as a solid base catalyst for transesterification of soybean oil and its application to biodiesel production, Fuel 87 (12) (2008) 2798–2806, doi:http:// dx.doi.org/10.1016/j.fuel.2007.10.019. A.K. Singh, S.D. Fernando, Transesterification of soybean oil using heterogeneous catalysts, Energy Fuels 22 (3) (2008) 2067–2069, doi:http://dx.doi.org/ 10.1021/ef800072z. F. Ma, M.A. Hanna, Biodiesel production: a review, Bioresour. Technol. 70 (1999) 1–15. S.Y. Hu, Y.P. Guan, Y. Wang, H.Y. Han, Nano-magnetic catalyst KF/CaO–Fe3O4 for biodiesel production, Appl. Energy 88 (2011) 2685–2690.

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