T. Geng et al. / Chinese Chemical Letters 21 (2010) 1020–1024
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Table 2
Impact of catalyst amount on the reaction rate.
Catalyst amount
AV of 4 h (mgKOH/g)
AV of 5 h (mgKOH/g)
AV of 6 h (mgKOH/g)
AV of filtered (mgKOH/g)
1%
2.91
2.91
3.07
2.90
2.28
2.12
2.02
2.12
1.96
1.89
1.81
1.75
1.68
1.62
1.55
1.58
0.75%
0.5%
0.25%
Notes: Reaction conditions: 190 8C, n(stearic acid):n(triethanolamine) = 1.8. Preparation conditions of ZS/SBA-15(6): ZS loading 20%, calcined at
˚
200 C for 2 h.
Table 3
The re-use of the 20%ZS/SBA-15(6).
Recycling times
AV of 4 h (mgKOH/g)
AV of 5 h (mgKOH/g)
AV of 6 h (mgKOH/g)
AV of filtered (mgKOH/g)
1
2
3
4
5
2.90
2.91
3.07
2.90
3.23
2.12
2.12
2.02
2.12
2.68
1.75
1.72
1.75
1.79
1.89
1.58
1.60
1.64
1.65
1.73
Notes: Reaction conditions: 190 8C, n(stearic acid):n(triethanolamine) = 1.8, catalyst dosage (based on mass of raw material) 0.25%. Preparation
conditions of ZS/SBA-15(6): ZS loading 20%, calcined at 200 8C for 2 h.
4 nm), and the pore diameter of 20%ZS/SBA-15(9) was larger than the size of tri-esteramine molecules (about 7 nm).
Compared with the commonly used H3PO3, 20%ZS/SBA-15(6) not only can improve the conversion of stearic acid,
but also makes the total content of mono- and di-esteramine increase by 8%.
The effect of catalyst amount on the esterification was studied. As shown in Table 2, the reaction rate did not
decrease along with the reduction of the catalyst amount. This indicated that a small amount of the catalyst in the
esterification reaction could have a good catalytic activity. Therefore, the catalyst amount should be reduced to 0.25%.
At present process of EA, hypophosphorous acid was commonly used as a catalyst. However, the catalyst was
difficult to separate from the product and could not be used repeatedly. In addition, the residue of catalyst in the
product would impact its application. The 20%ZS/SBA-15(6) could be removed by filtration and could be reused.
According to Table 3, when 20%ZS/SBA-15(6) was reused for five times, the catalytic activity of the catalyst did not
decrease obviously. This illustrated that 20%ZS/SBA-15(6) had good stability and was an efficient catalyst for the
esterification of stearic acid and TEA.
3. Conclusion
Solid acid catalyst ZS/SBA-15(6) not only could speed up the reaction rate and increase the content of mono- and
di-esteramine in comparison with hypophosphorous acid, but also had good stability and could be reused for at least
five times. Therefore, it could be used as catalyst to replace conventional hypophosphorous acid for the synthesis of
EA. In addition, high catalytic activity and selectivity of ZS/SBA-15(6) could be achieved by adjusting the surface
area, pore diameter and ZS loading.
Acknowledgments
We thank the National 11th Five-Year Technology Support Project (No. 2007BAE52B00), Natural Science
Foundation of Shanxi (No. 2008021017) and China Research Institute of Daily Chemical Industry for fund support.
References
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[3] S. Mishra, V.K. Tyagi, J. Oleo Sci. 56 (2007) 269.