| 1,5,9-cyclododecatriene (CDT) is the main raw material for the synthesis of large ring compounds, which can be used to produce musk, spices, nylon12, flame retardants and cyclic polyols, dodecane etc. The cyclotrimerization of1,3-butadiene over titanium or nickel-based catalyst system is the main method to obtain CDT. Nowadays, technologies relating to CDT production are mainly controlled by developed countries. In this paper, the cyclotrimerization process of1,3-butadiene to CDT on a Ti-based catalyst system, TiCl4/Et1.5AlCl1.5(EASC)/dimethyl sulfoxide (DMSO) was carried out. The effects of the temperature, the molar ratio of Al/Ti, the molar ratio of sulfone/Ti, and the TiCl4concentration were investigated. And on the basis of the three-component catalyst system, a fourth component-the electron donor, such as triphenylphosphine (PPh3), new oxygen-containing electron donors (LA-O-R1, LB-O-R2, Lc-O-R3, R4-O-LD-O-R4, R5-O-LE-O-R5, L-containing elements of C, H etc., R-hydrocarbon substituents) was added to improve the activity and selectivity of the catalyst. Meanwhile, in order to explore the catalytic mechanism of electron donors, several typical electron donors were study by molecular modeling.The experimental results showed that for TiCl4/EASC/DMSO system, under atmospheric conditions, with TiCl4concentration=0.47mmol/L, Al/Ti=30, and sulfone/Ti=1, the catalyst activity was up to6947.3gCDT/(gTi·h) maintaining the high selectivity of CDT (>97%). In the precence of the electron donor, the catalyst system combined with LB-O-R2showed the best performance. Under the optical condition, the activity of this catalyst system was up to23941.7gCDT/(gTi·h), which was3.4times higher than that of the orginal three component catalyst. The molecular modeling results of the combination of Ti3+and electron donors showed that higher activity of the catalytic reaction was related with the shorter coordination bond length of Ti and O, and the relative lower binding energy. |
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