Composite catalyst, preparation process thereof, and process for catalyzing the trimerization of butadiene using the composite catalyst

A composite catalyst trimerization of butadiene to 1,5,9-cyclododecatriene consisting of

• (A) a titanium compound catalyst active component, wherein the titanium compound is one or more selected from TiCl4, TiCl2R4-z or TiClz(OR)4-z, wherein Z=1, 2 or 3, OR is alkoxy, R is alkyl having 1-20 carbons,
• (B) an organometallic compound co-catalyst component selected from one or more of methyl lithium, n-butyl lithium, n-hexyl lithium, sec-butyl lithium,
• (C) a sulfoxide compound catalyst-modifying component selected from one or more of dimethyl sulfoxide, thionyl chloride, diphenyl sulfoxide, and trimethylsulfoxonium iodide,
• (D) a monoester compound catalyst-modifying component selected from one or more of the group consisting of methyl p-hydroxybenzoate, ethyl p-hydroxybenzoate, butyl p-hydroxybenzoate, methyl aminobenzoate, ethyl aminobenzoate, butyl aminobenzoate, methyl p-benzenesulfonate, ethyl p-benzenesulfonate, butyl p-benzenesulfonate, methyl salicylate, ethyl salicylate and butyl salicylate, and
• (E) a solvent component selected from one or more of propane, n-butane, isobutane, n-pentane, isopentane, neopentane, n-hexane, cyclohexane, n-heptane, n-octane, benzene, toluene, xylene, 1,5,9-cyclododecatriene.