Chlorobenzene hydrodechlorination on bimetallic catalysts prepared by laser electrodispersion of NiPd alloy

NiPd bimetallic systems were for the first time synthesized by laser electrodispersion (LED) of the Ni₇₇Pd₂₃ alloy target followed by the deposition of produced bimetallic particles on a TEM copper grid and alumina granules. Selective area energy-dispersive analysis confirms the bimetallic nature of NiPd particles deposited on a TEM copper grid. Their mean size is 1.0 nm according to TEM. XPS data demonstrate that under deposition on alumina granules (total metal content of 0.005 wt.%), nickel in bimetallic particles nearly completely oxidizes to Ni²⁺ species predominantly in the form of aluminate. At the same time major part of palladium (84%) exists in Pd⁰ but oxidizes to Pd²⁺ (80%) during 6 months storage in air. Both metals are deposited on the external surface of alumina granules and localized in the same areas. In situ reduction of both metals by H₂ in the catalytic cell of XPS spectrometer is hindered. Nickel is not reduced even at 450°C, confirming the formation of NiAlO_x, whereas palladium is reduced at higher temperatures compared to a similar monometallic catalyst. Nevertheless, NiPd/Al₂O₃ catalyst is more efficient in gas-phase chlorobenzene hydrodechlorination at 150–350°C than Ni/Al₂O₃ and even Pd/Al₂O₃, and much more stable. The difference may be caused by the formation of new active sites due to the contact between Pd⁰ and NiAlO_x-modified support, and the protective action of spinel reacting with HCl by-product.