The present invention relates to a method for synthesizing halogenated
biphenyl, wherein one halogenated
aniline of 4-bromium-2-fluoroaniline or 2, 4-difluoro
aniline or 2-fluoroaniline or 4-fluoroaniline or the like, and the
benzene are used as the principal
raw material under a acidic condition, the
trichloroacetic acid, the
anhydrous magnesium sulphate and homemade composite catalyst containing
copper or
zinc or iron are added into a same reactor, and a diazotization reaction and a
coupling reaction are completed synchronously. The invention also discloses a method for preparing a homemade composite catalyst containing a
metal, including the steps: adding the
dimethylformamide into a reactor, filling the
nitrogen to protect, adding 0.1-1.0
equivalent weight ammonium formate, 0.5-1.0
equivalent weight N, N, N', N'-tetraphenyl
ethylene diamine and 0.1-0.3
equivalent weight CuCl2 or ZnCl2 or FeCl3 and 0.01-0.03 equivalent weight PdCl2, then mixing and heating until 30-60 DEG C, agitating thoroughly and holding for 15-24 hours, cooling, filtrating and
vacuum drying, the composite catalyst containing a
metal will be obtained. By means of using a same reactor, the halogenated
biphenyl may be prepared by the diazotization and the
coupling reaction completed in one same step, the yield is more than 85% by the halogenated
aniline. The product content achieves 99.5%, the production period is shortened greatly, the equipment production capacity is improved, the
energy consumption and
material consumption are all reduced, and the work intensity of workers is alleviated greatly, thus the method of the invention is very suitable for an industrialization great production.