To provide various metal nanoparticles having a flocculation protective material comprising an alkyne compound or an alkene compound to which the flocculation protective material is not firmly coupled, and in which active sites are not clogged with the flocculation protective material, and to provide a method for producing the same.

A flocculation protective agent comprising an alkyne compound or an alkylene compound, one or more kinds of metallic compounds selected from Ru, Co, Rh, Ni, Pd, Pt, Os, Ag and Au (in the case the metallic compound is one kind, Pd is excluded), and a reducing agent are reacted, so as to produce metal nanoparticles. Further, using the metal nanoparticles produced by the above method as a catalyst, an alkane compound or an alkene compound in which an alkyne compound as a reaction matrix is hydrogenated in the presence of hydrogen or a compound donating hydrogen is produced.

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