Preparation method of double-ion type crude oil desalting demulsifier

The invention relates to a preparation method of a double-ion type crude oil desalting demulsifier. The preparation method specifically comprises the following steps: (1) carrying out esterification modification on polyethylene glycol monomethyl ether; (2) preparing glycidyl dimethyl alkyl ammonium chloride; (3) preparing quaternary ammonium carboxymethyl chitosan; (4) making the modified polyethylene glycol monomethyl ether react with the quaternary ammonium carboxymethyl chitosan to obtain a polyethylene glycol monomethyl ether grafted quaternary ammonium carboxymethyl chitosan. The double-ion type crude oil desalting demulsifier takes natural macromolecular compounds of chitosan as raw materials, thereby having many advantages of wide sources, naturalness, no toxicity, sustainability, good product bio-compatibility and degradation and the like. The prepared demulsifier is good in demulsification and dehydration effects, furthermore, demulsifier molecules contain a large number of carboxyl alkyl groups and