Enhancing the Catalytic Activity and Selectivity of PdAu/SiO₂ Bimetallic Catalysts for Dodecahydro- N-ethylcarbazole Dehydrogenation by Controlling the Particle Size and Dispersion

The design and development of catalysts for dodecahydro-N-ethylcarbazole (12H-NECZ) dehydrogenation restrict the achievement of the cyclic hydrogenation/dehydrogenation process. In this work, the M/SiO₂ (M = Pt, Pd, Ru, Rh, Au) and bimetallic PdAu/SiO₂ catalysts are prepared, and their catalytic performances are measured. By XRD, XPS, HRTEM, and CO pulse chemisorption, we find that the alloy structure is not generated and the average particle size increases with the improvement of the Au amount in the bimetallic catalysts. Besides, the catalytic performance can be enhanced dramatically with introducing a small amount Au. Pd₃Au₁/SiO₂ exhibits the best catalytic performance with the complete conversion, 94.9 selectivity to NECZ, and 5.7 wt % hydrogen release amount. The TOF values are up to 240.7 min^-1, 2.26 times higher than that of Pd/SiO₂. The qualitative and quantitative analyses indicate that 4H-NECZ dehydrogenation is the rate-limiting step. It can be proposed that controlling the particle size and dispersion of the PdAu/SiO₂ bimetallic catalysts will bring a significant enhancement of catalytic performance.