Acid-tolerant intermetallic cobalt–nickel silicides as noble metal-like catalysts for selective hydrogenation of phthalic anhydride to phthalide

Chemoselective hydrogenation of phthalic anhydride is regarded as the most promising route for producing downstream high-performance phthalide. A series of intermetallic cobalt–nickel silicide catalysts embedded in a carbon matrix (CoxNi2−xSi@C) with acid-tolerance prepared by microwave-assisted chemical vapor deposition have been investigated in this reaction system. Activity measurements show a remarkable positive synergistic effect, forming a volcano-shaped plot over the nominal Co metal fraction for CoxNi2−xSi@C catalysts with a peak at x = 1.5, which corresponds to a 4.5-fold enhancement of the yield of phthalide over Co2Si@C and a 2.0-fold enhancement over the Ni2Si@C monometallic silicide catalysts, which can be correlated with the interaction of cobalt–nickel and metal–silicon bonds. In addition, the cobalt-rich bimetallic silicide exhibits an equal activity to the reference noble metal catalysts (Au, Pd, and Pt) and a significantly higher activity than transition metal catalysts. Moreover, the bimetallic silicide as an intermetallic compound catalyst has demonstrated robust acid corrosion resistance compared to the corresponding metal catalysts.