Preparation and purification methods of quaternary ammonium salt type dimeric surfactant

The invention relates to a preparation method capable of improving the composition obtained by recycling hydrocarbon, and belongs to the field of preparation of a quaternary ammonium compound. The preparation method comprises the following steps of mixing alpha-alkyl halide and N, N, N', N'-tetramethylethylenediamine at the mole ratio of (2-3):1, and stirring at 50-90 DEG C for 8-16 hours, thereby obtaining the quaternary ammonium salt type dimeric surfactant. A purification method comprises the following steps of recrystallizing a crude product of the quaternary ammonium salt type dimeric surfactant obtained by the preparation method by using a solvent, then drying so as to obtain a white powdery solid which is the purified quaternary ammonium salt type dimeric surfactant. According to the preparation and purification methods of the quaternary ammonium salt type dimeric surfactant, a method of cooking in one pot is adopted, so that the inconvenience caused by charging step by step is prevented. Other reaction solvents are not added in the synthesis process, so that the production cost is reduced greatly, and the technological process is shortened; the synthesized surfactant is very high in productivity, is good in performance, and can be used for producing detergents, foam drilling fluids and displacement agent for tertiary oil recovery and the like.