PILs-XSS : 1,2-dibromoethane ; PILs-XST : 1,3-dibromopropane ; PILs-XSO : 1,4-dibromobutane ; PILs-XSP : 1,5-dibromopentane ; PILs-XSQ : 1,6-dibromohexane ;
Reaction conditions : catalyst PILs dosage2.5wt %, CO2pressure1.5MPa, reaction temperature100 °C, reaction time4h, methanol / PO molar ratio3 : 1, transesterification catalyst Na2CO3dosage 3wt %.
The activities of a series of PILs/Na2CO3 catalysts are compared in Table 2. By comparing the catalytic activities of the same series of bromides, it was found that the chain was longer, the catalytic activity was lower. In the process of producing catalysts, it was found that the chain was longer, the hardness of the synthesized spherical particles was lower. Therefore, 1,2 - dibromoethane was reasonable as a raw material.
3.4 Investigation of reusability
In addition to the high requirements for the catalytic activity of organic catalysts, sustainable utilization is equally important in production, which determines whether continuous production can be achieved. Therefore, the reusability of PILs-XSS was evaluated under the optimal conditions ( PILs-XSS dosage 2.5wt %, CO2pressure 1.5MPa, reaction temperature 100 °C, reaction time 4h, methanol / PO molar ratio 3: 1, Na2CO3 dosage 3wt % ). As shown in Fig. 8, The catalytic activity of PILs-XSS was not significantly decreased after five consecutive cycles. The spherical state of the catalyst did not also changed. This indicated that the catalyst had a strong mechanical strength and recyclability.