Production method of thionyl chloride

The invention belongs to the technical field of chemical production and particularly relates to a production method of thionyl chloride. Synthesis gas produced by sulfur and chlorine through a reaction in a synthesis kettle and sulfur dioxide gas enter a reactor together, and crude thionyl chloride generated through the reaction in the reactor is directly decolorized by a sulfur tank in a gas state and then enters a rectifying tower; a gas phase at the top of the rectifying tower enters a return tank after being condensed, a gas phase in the return tank enters an exhaustion tank through an ejector and is cyclically and mechanically applied to the synthesis kettle, and a qualified product is produced from the middle of the rectifying tower. Thionyl chloride is produced in a fully-closed circulation manner, no wastewater, waste gas or waste residues are discharged, and the product yield basically reaches 100%.