The invention relates to a continuous-pressure-changing rectification method and a device for preparing
medicine-level
sulfoxide chloride. With the adoption of the pressure-changing rectification method, an indirect sequence of carrying out heavy component removal and then carrying out light component removal is adopted as a rectification sequence, so that the
decomposition of
sulfoxide chloride at high temperature is reduced;
sulfur is coarsely mixed with raw materials,
sulfur is mixed with
tower top gas of a heavy component removal
tower, and a low-boiling-point substance, namely
sulfur dichloride which is hard to remove, is fundamentally converted into a high-boiling-point substance, namely
sulfur monochloride which is easy to remove, due to multistep sulfur adding; and a catalyst is added, so that the
dissolution rate and
reaction rate of the sulfur are accelerated. The heavy component removal
tower is subjected to normal-pressure operation; and a light component removal tower is subjected to depressurized operation. The
energy consumption of operation is reduced, and the
decomposition reaction of the
sulfoxide chloride hardly carries out under depressurized conditions, so that the probability that the color and luster of products are polluted by
sulfur dichloride is greatly reduced, high-purity and colorless sulfoxide chloride products are produced from tower bottoms, and the content is over 99.9%.