Method of selectively synthesizing di-tert-butyl trithioether

The invention provides a method of selectively synthesizing di-tert-butyl trithioether. The di-tert-butyl trithioether is synthesized through a one-step process from isobutene, sulfur and hydrogen sulfide as raw materials under a high pressure. The product ingredient shows almost normal distribution from tert-butyl mercaptan, di-tert-butyl monothioether until di-tert-butyl heptathioether although the reaction belongs to atomic economy reaction and the conversion almost reaches 100%, wherein the molar percentage of di-tert-butyl dithioether is only 30-40%. In the presence of a phase transfer catalyst, the di-tert-butyl poly-thioether mixture is processed in a sodium sulfide water solution, wherein low thioethers and high thioethers are subjected to a disproportionation reaction, thereby selectively obtaining the di-tert-butyl trithioether. The molar percentage of the di-tert-butyl trithioether in the product is more than 90%, so that a process of pressure-reduced rectification for separating the trithioether i