The invention discloses a preparation method for catalytic synthesis of 4,4'-diaminostilbene. The preparation method comprises the following steps: with a
superparamagnetic nanoparticle loaded
ionic liquid as a catalyst, subjecting
chlorobenzene and
thionyl chloride to a Friedel-Crafts reaction under the action of the catalyst, after the reaction is completed, additionally adding a catalyst recovered by a
magnetic field, pouring out a reaction solution, dropwise adding a saturated
sodium bicarbonate solution into the reaction solution until the pH value of the solution is adjusted to be neutral, then carrying out stirring, filtering the material liquid while the material liquid is hot, cooling a filtrate to 0-5 DEG C for crystallizing, carrying out filtering so as to obtain 4,4'-dichlorodiphenyl
sulfoxide, dissolving the 4,4'-dichlorodiphenyl
sulfoxide into glacial
acetic acid, adding
hydrogen peroxide for an oxidation reaction, carrying out cooling after the reaction is finished, andcarrying out filtering so as to obtain 4,4'-dichlorodiphenyl
sulfone. According to the invention, the
chlorobenzene is used as a reaction
raw material and a
solvent; no
solvent impurities are not mixed; meanwhile, simple process, low cost and few impurities are achieved; an obtained product is high in purity and has a content of 99.2% or above; the content of a 2,4'-isomer is smaller than 0.1%; the yield reaches 90% or above; and the preparation method provided by the invention is good in economic benefit and applicable to industrial production.