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Synthesis of vegetable oil based polyol with cottonseed oil and sorbitol derived from natural source
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Chinese Chemical Letters 22 (2011) 1289–1292 www.elsevier.com/locate/cclet
Synthesis of vegetable oil based polyol with cottonseed oil and sorbitol derived from natural source Lian Kun Jia, Li Xiang Gong, Wen Jiao Ji, Cheng You Kan * Department of Chemical Engineering and Key Laboratory of Advanced Materials of Education Ministry, Tsinghua University, Beijing 100084, China Received 30 March 2011 Available online 28 July 2011
Abstract In order to prepare the polyol with all bio-based components as raw materials, cottonseed oil was first epoxidized by peroxyformic acid generated in situ from hydrogen peroxide and formic acid, and the cottonseed oil based polyols with variable hydroxyl value were then prepared by the ring-opening of epoxidized cottonseed oil with sorbitol, which is a multi-functional hydroxyl compound derived from a natural source. The chemical structure of the products was characterized with FTIR analysis, and the residual epoxy oxygen content and hydroxyl value of the polyol versus the ring-opening time were investigated. # 2011 Cheng You Kan. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved. Keywords: Vegetable oil; Sorbitol; Polyol; Epoxidation; Ring opening reaction
Since petroleum is rapidly consumed and unrenewable, bio-based materials have received great attention in recent years. Vegetable oil based polyols, which are relatively cheap, environmentally friendly and renewable, have been used to replace or partially replace conventional polyols derived from petroleum in many fields such as the polyurethane manufacture and fine chemicals. There are several methods to prepare vegetable oil based polyols [1– 3], including epoxidation of vegetable oil followed by ring opening reaction, hydroformylation, ozonolysis, etc. As the most economical and the safest route, the epoxidation of vegetable oil followed by ring-opening reaction has been intensively studied. The investigations to the first step of epoxidation have been very all-sided because of the important application of epoxidized vegetable oil as a plastifier in plastic industry [4]. As for the second step of ringopening reaction, most of investigations were focused on the selection of catalyst system and the application of small alcohols derived from petroleum as the ring opening reagents [5,6]. In this study, in order to increase the bio-based components in vegetable oil based polyols, sorbitol, a multi-functional hydroxyl compound derived from a natural source was selected as a ring opening reagent to react with epoxidized cottonseed oil to prepare cottonseed oil based polyols. The reactions and chemical structure of the products were investigated preliminarily by FTIR, epoxy oxygen content and hydroxyl value.
* Corresponding author. E-mail address: [email protected] (C.Y. Kan). 1001-8417/$ – see front matter # 2011 Cheng You Kan. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved. doi:10.1016/j.cclet.2011.05.043
1290
L.K. Jia et al. / Chinese Chemical Letters 22 (2011) 1289–1292
1. Experimental Cottonseed oil and sorbitol were provided by Zhuhaijiahe Cereal and Oil Co. Ltd. Aqueous HCOOH (88 wt%), aqueous H2O2 solution (30 wt%), aqueous HBF4 solution (40 wt%) and all other chemicals for analytical purpose were of analytical grade from Jingcheng Chuangqi Chemical Reagent Co. Ltd and used as supplied. Cottonseed oil based polyols were prepared through the following two steps as shown in Scheme 1: (1) Epoxidation—epoxidation of cottonseed oil was carried out in a 500-mL four-necked round-bottom flask equipped with a thermometer, a mechanical stirrer, a condenser and a dropping funnel. 160 g of cottonseed oil and 24 g of aqueous HCOOH (88 wt%) were introduced into the flask and heated in a water bath. When the temperature of the system reached about 50 8C, 160 g of aqueous H2O2 solution (30 wt%) was drop-wise added into the flask in 10 min, and the reaction was continued further first for 1 h at 55 1 8C and then for 5 h at 60 1 8C. (2) Ring-opening reaction—cottonseed oil based polyols were synthesized by the ring-opening of the epoxidized cottonseed oil with sorbitol in the presence of tetrafluoroboric acid. The molar ratio of epoxy group to sorbitol was 1, and the concentration of the catalyst was 0.5 wt% of the total weight of the epoxidized oil and sorbitol. Sorbitol was first dissolved in a small amount of water and added into a 250 mL three-neck round-bottom flask equipped with a mechanical stirrer, a condenser and a thermometer. When the system was heated to 60 1 8C in a water bath, the catalyst and epoxidized cottonseed oil were added to the flask, and the reaction was continued further for the desired time. Before performing the characterization, the unreacted sorbitol was removed by water extraction and the products were further purified by vacuum distillation. The epoxy oxygen content and the hydroxyl value of the purified products were determined according to GB/T 1677-2008 and HG/T 2709-95, respectively. The IR spectra were recorded on a Fourier transformation infrared (FTIR) spectrometer (NICOLET 560, USA) by coating the products on KBr salt plates. 2. Results and discussion FTIR spectra of cottonseed oil, epoxidized cottonseed oil and cottonseed oil based polyols prepared by ringopening of the epoxidized cottonseed oil with sorbitol are shown in Fig. 1. It is clear that the peak related to carbon– carbon double bonds from cottonseed oil at 3008 cm 1 disappeared upon epoxidation and the epoxy groups were found in epoxidized cottonseed oil (doublet at 823 cm 1 and 843 cm 1), indicating that all of the carbon–carbon double bonds were turned into epoxy groups. After the ring-opening reaction, the characteristic peaks of epoxidized cottonseed oil weakened and hydroxyl band at about 3467 cm 1 became prominent. The relationship between the residual epoxy oxygen content in the cottonseed oil based polyols and the ringopening reaction time is given in Fig. 2. As expected, the residual epoxy oxygen content of the product decreased from 5.40% to 2.69% when the reaction time prolonged to 7 h, which means that the ring-opening reaction was linearly dependent on the reaction time. However, when the reaction time was over 7 h, the viscosity of the reaction system increased rapidly, and the content in the flask was gelled because of high crosslinking.
R1 HC CH R
C O
R1 CH CH
CH2
R' OH
O
O
O
R
C
O
CH2
R1 CH CH R'
O (1) R2
HC HC
R
C O
CH
R C O O
cottonseed oil
R C
Epoxidiation
O R3 HC HC
R2 CH CH
CH2
O
CH
R3
H C O
R
C
O
CH2
O
epoxidized cottonseed oil
R, R1, R2, R3 are alkyls with differnt number of carbon atoms
O
CH2
R C
O
CH
O
CH2
O R3
H C
H C
R'
OH
R C O
cottonseed oil based polyol
R' is the residue segment of sorbitol
Scheme 1. Synthetic route of cottonseed oil based polyol.
C
OH
R2 CH CH Ring opening reaction
O H C
(2)
O R
L.K. Jia et al. / Chinese Chemical Letters 22 (2011) 1289–1292
1291
Fig. 1. FTIR spectra of cottonseed oil, epoxidized cottonseed oil and cottonseed oil based polyol.
Fig. 2. The residual epoxy oxygen content of cottonseed oil based polyols versus ring-opening reaction time.
Table 1 Influence of the ring-opening reaction time on the consumption of epoxy groups and the hydroxyl values of cottonseed oil based polyols. Time (h)
Consumption of epoxy groups (mol%)
Hydroxyl value (mg KOH/g)
2 4 5 6 7
13.3 25.4 37.4 38.2 50.2
52.5 75.8 76.8 78.1 90.6
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L.K. Jia et al. / Chinese Chemical Letters 22 (2011) 1289–1292
The consumption of epoxy groups in the ring-opening reaction can be calculated based on the residual epoxy oxygen content in the polyols, and results are given in Table 1. It is clear that the consumption of epoxy groups increased with the reaction time, and 50.2% of epoxy groups were reacted with sorbitol at 7 h. The hydroxyl values of cottonseed oil based polyols at different reaction times are given in Table 1. The hydroxyl value gradually increased with the increase of ring-opening reaction time, and reached 90.6 mg KOH/g at 7 h. Assuming all of the consumed epoxy groups were reacted with sorbitol in equal mole ratio of epoxy and sorbitol and no side reaction took place, the maximal hydroxyl value of the product should be 312 mg KOH/g. The difference between experimental and theoretical values was mainly due to the crosslinking side reactions, which consumed some of hydroxyl groups. When the reaction time was over 7 h, excessive crosslinking made the viscosity of the reaction system too high to measure the hydroxyl value of the product. In summary, the vegetable oil based polyols with variable hydroxyl values were synthesized by epoxidizing of cottonseed oil followed by ring-opening reaction of the epoxidized oil with sorbitol. Further investigations such as the effect of reaction time on the structure and molecular weight of polyols and the method to increase hydroxyl value are ongoing in our lab. References [1] [2] [3] [4] [5] [6]
Z. Petrovic, I. Javni, A. Guo, US Patent 6,433,121. A. Guo, D. Demydov, W. Zhang, J. Polym. Environ. 10 (2002) 49. Z. Petrovic, W. Zhang, I. Javni, Biomacromolecules 6 (2005) 713. A. Adharyu, S.Z. Erhan, Ind. Crops Prod. 15 (2002) 247. B. Lin, L.T. Yang, H.H. Dai, J. Am. Oil. Chem. Soc. 85 (2008) 113. H.H. Dai, L.T. Yang, B. Lin, J. Am. Oil. Chem. Soc. 86 (2009) 261.
Chinese Chemical Letters 22 (2011) 1289–1292 www.elsevier.com/locate/cclet
Synthesis of vegetable oil based polyol with cottonseed oil and sorbitol derived from natural source Lian Kun Jia, Li Xiang Gong, Wen Jiao Ji, Cheng You Kan * Department of Chemical Engineering and Key Laboratory of Advanced Materials of Education Ministry, Tsinghua University, Beijing 100084, China Received 30 March 2011 Available online 28 July 2011
Abstract In order to prepare the polyol with all bio-based components as raw materials, cottonseed oil was first epoxidized by peroxyformic acid generated in situ from hydrogen peroxide and formic acid, and the cottonseed oil based polyols with variable hydroxyl value were then prepared by the ring-opening of epoxidized cottonseed oil with sorbitol, which is a multi-functional hydroxyl compound derived from a natural source. The chemical structure of the products was characterized with FTIR analysis, and the residual epoxy oxygen content and hydroxyl value of the polyol versus the ring-opening time were investigated. # 2011 Cheng You Kan. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved. Keywords: Vegetable oil; Sorbitol; Polyol; Epoxidation; Ring opening reaction
Since petroleum is rapidly consumed and unrenewable, bio-based materials have received great attention in recent years. Vegetable oil based polyols, which are relatively cheap, environmentally friendly and renewable, have been used to replace or partially replace conventional polyols derived from petroleum in many fields such as the polyurethane manufacture and fine chemicals. There are several methods to prepare vegetable oil based polyols [1– 3], including epoxidation of vegetable oil followed by ring opening reaction, hydroformylation, ozonolysis, etc. As the most economical and the safest route, the epoxidation of vegetable oil followed by ring-opening reaction has been intensively studied. The investigations to the first step of epoxidation have been very all-sided because of the important application of epoxidized vegetable oil as a plastifier in plastic industry [4]. As for the second step of ringopening reaction, most of investigations were focused on the selection of catalyst system and the application of small alcohols derived from petroleum as the ring opening reagents [5,6]. In this study, in order to increase the bio-based components in vegetable oil based polyols, sorbitol, a multi-functional hydroxyl compound derived from a natural source was selected as a ring opening reagent to react with epoxidized cottonseed oil to prepare cottonseed oil based polyols. The reactions and chemical structure of the products were investigated preliminarily by FTIR, epoxy oxygen content and hydroxyl value.
* Corresponding author. E-mail address: [email protected] (C.Y. Kan). 1001-8417/$ – see front matter # 2011 Cheng You Kan. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved. doi:10.1016/j.cclet.2011.05.043
1290
L.K. Jia et al. / Chinese Chemical Letters 22 (2011) 1289–1292
1. Experimental Cottonseed oil and sorbitol were provided by Zhuhaijiahe Cereal and Oil Co. Ltd. Aqueous HCOOH (88 wt%), aqueous H2O2 solution (30 wt%), aqueous HBF4 solution (40 wt%) and all other chemicals for analytical purpose were of analytical grade from Jingcheng Chuangqi Chemical Reagent Co. Ltd and used as supplied. Cottonseed oil based polyols were prepared through the following two steps as shown in Scheme 1: (1) Epoxidation—epoxidation of cottonseed oil was carried out in a 500-mL four-necked round-bottom flask equipped with a thermometer, a mechanical stirrer, a condenser and a dropping funnel. 160 g of cottonseed oil and 24 g of aqueous HCOOH (88 wt%) were introduced into the flask and heated in a water bath. When the temperature of the system reached about 50 8C, 160 g of aqueous H2O2 solution (30 wt%) was drop-wise added into the flask in 10 min, and the reaction was continued further first for 1 h at 55 1 8C and then for 5 h at 60 1 8C. (2) Ring-opening reaction—cottonseed oil based polyols were synthesized by the ring-opening of the epoxidized cottonseed oil with sorbitol in the presence of tetrafluoroboric acid. The molar ratio of epoxy group to sorbitol was 1, and the concentration of the catalyst was 0.5 wt% of the total weight of the epoxidized oil and sorbitol. Sorbitol was first dissolved in a small amount of water and added into a 250 mL three-neck round-bottom flask equipped with a mechanical stirrer, a condenser and a thermometer. When the system was heated to 60 1 8C in a water bath, the catalyst and epoxidized cottonseed oil were added to the flask, and the reaction was continued further for the desired time. Before performing the characterization, the unreacted sorbitol was removed by water extraction and the products were further purified by vacuum distillation. The epoxy oxygen content and the hydroxyl value of the purified products were determined according to GB/T 1677-2008 and HG/T 2709-95, respectively. The IR spectra were recorded on a Fourier transformation infrared (FTIR) spectrometer (NICOLET 560, USA) by coating the products on KBr salt plates. 2. Results and discussion FTIR spectra of cottonseed oil, epoxidized cottonseed oil and cottonseed oil based polyols prepared by ringopening of the epoxidized cottonseed oil with sorbitol are shown in Fig. 1. It is clear that the peak related to carbon– carbon double bonds from cottonseed oil at 3008 cm 1 disappeared upon epoxidation and the epoxy groups were found in epoxidized cottonseed oil (doublet at 823 cm 1 and 843 cm 1), indicating that all of the carbon–carbon double bonds were turned into epoxy groups. After the ring-opening reaction, the characteristic peaks of epoxidized cottonseed oil weakened and hydroxyl band at about 3467 cm 1 became prominent. The relationship between the residual epoxy oxygen content in the cottonseed oil based polyols and the ringopening reaction time is given in Fig. 2. As expected, the residual epoxy oxygen content of the product decreased from 5.40% to 2.69% when the reaction time prolonged to 7 h, which means that the ring-opening reaction was linearly dependent on the reaction time. However, when the reaction time was over 7 h, the viscosity of the reaction system increased rapidly, and the content in the flask was gelled because of high crosslinking.
R1 HC CH R
C O
R1 CH CH
CH2
R' OH
O
O
O
R
C
O
CH2
R1 CH CH R'
O (1) R2
HC HC
R
C O
CH
R C O O
cottonseed oil
R C
Epoxidiation
O R3 HC HC
R2 CH CH
CH2
O
CH
R3
H C O
R
C
O
CH2
O
epoxidized cottonseed oil
R, R1, R2, R3 are alkyls with differnt number of carbon atoms
O
CH2
R C
O
CH
O
CH2
O R3
H C
H C
R'
OH
R C O
cottonseed oil based polyol
R' is the residue segment of sorbitol
Scheme 1. Synthetic route of cottonseed oil based polyol.
C
OH
R2 CH CH Ring opening reaction
O H C
(2)
O R
L.K. Jia et al. / Chinese Chemical Letters 22 (2011) 1289–1292
1291
Fig. 1. FTIR spectra of cottonseed oil, epoxidized cottonseed oil and cottonseed oil based polyol.
Fig. 2. The residual epoxy oxygen content of cottonseed oil based polyols versus ring-opening reaction time.
Table 1 Influence of the ring-opening reaction time on the consumption of epoxy groups and the hydroxyl values of cottonseed oil based polyols. Time (h)
Consumption of epoxy groups (mol%)
Hydroxyl value (mg KOH/g)
2 4 5 6 7
13.3 25.4 37.4 38.2 50.2
52.5 75.8 76.8 78.1 90.6
1292
L.K. Jia et al. / Chinese Chemical Letters 22 (2011) 1289–1292
The consumption of epoxy groups in the ring-opening reaction can be calculated based on the residual epoxy oxygen content in the polyols, and results are given in Table 1. It is clear that the consumption of epoxy groups increased with the reaction time, and 50.2% of epoxy groups were reacted with sorbitol at 7 h. The hydroxyl values of cottonseed oil based polyols at different reaction times are given in Table 1. The hydroxyl value gradually increased with the increase of ring-opening reaction time, and reached 90.6 mg KOH/g at 7 h. Assuming all of the consumed epoxy groups were reacted with sorbitol in equal mole ratio of epoxy and sorbitol and no side reaction took place, the maximal hydroxyl value of the product should be 312 mg KOH/g. The difference between experimental and theoretical values was mainly due to the crosslinking side reactions, which consumed some of hydroxyl groups. When the reaction time was over 7 h, excessive crosslinking made the viscosity of the reaction system too high to measure the hydroxyl value of the product. In summary, the vegetable oil based polyols with variable hydroxyl values were synthesized by epoxidizing of cottonseed oil followed by ring-opening reaction of the epoxidized oil with sorbitol. Further investigations such as the effect of reaction time on the structure and molecular weight of polyols and the method to increase hydroxyl value are ongoing in our lab. References [1] [2] [3] [4] [5] [6]
Z. Petrovic, I. Javni, A. Guo, US Patent 6,433,121. A. Guo, D. Demydov, W. Zhang, J. Polym. Environ. 10 (2002) 49. Z. Petrovic, W. Zhang, I. Javni, Biomacromolecules 6 (2005) 713. A. Adharyu, S.Z. Erhan, Ind. Crops Prod. 15 (2002) 247. B. Lin, L.T. Yang, H.H. Dai, J. Am. Oil. Chem. Soc. 85 (2008) 113. H.H. Dai, L.T. Yang, B. Lin, J. Am. Oil. Chem. Soc. 86 (2009) 261.