Method for preparing n-butene polymer by using olefins from industrial waste C4 products

The invention relates to a method for preparing n-butene polymer by using olefins from industrial waste C4 compounds. The method comprises the following steps of: preparing a complexing initiating agent by taking aluminum choride, halogenated hydrocarbon, boron trifluoride, and organic solvent, wherein the mole ratio of the aluminum choride to the halogenated hydrocarbon to the boron trifluoride is 1:0.5 to 0.8 to 1.0, and the mass of the organic solvent is 1.7 to 4.5 times that of the aluminum choride; adding the prepared complexing initiating agent of which the weight is 0.9 to 7.0 percent of that of the industrial waste C4 compounds to carry out a polymerization reaction to obtain crude n-butene polymer, and weighting the crude n-butene polymer; selecting cyclohexane serving as a thinning agent of which the mass is 0.8 to 1.5 times that of the crude n-butene polymer; and carrying out atmospheric distillation on 10.0 percent of caustic soda solution serving as a terminator of which the mole number is 2.0 to 5.0 times that of the aluminum choride in the complexing initiating agent to obtain n-butene polymer products. The method has the advantages that: the method adopts the complexing initiating agent with high activity, and polymerizes over 90 percent of olefin into target products even if the n-butene content of the waste C4 compounds is low; the residual is mostly saturated alkane after polymerization; and thus, environmental pollution of burning oil is greatly improved.