Synthesis of Tailored Egg-Shell Pd@Al₂O₃ Catalyst for Catalytic Hydrogenation of 2-Alkylanthraquinone

Abstract

Egg-shell Pd@Al2O3 is the most common catalyst for the catalytic hydrogenation of 2-alkylanthraquinone on the industrial scale because of their virtues of maximizing the utilization of the precious metal. The palladium particles preformed by microemulsion method were deposited onto the alumina which differ from the hydrophobic nature and textural properties. In this method polyoxyethylene(7–8) octylphenyl ether was used as surfactants, from which palladium metal nanoparticles (ca. 2.3–2.5 nm) exhibit a narrower size distribution and higher extent of palladium reducibility compared with the typical Pd@Al2O3 currently used in industrial plants. Transmission electron microscopy, digital microscopy, H2–O2 titration, and other chemisorptions results clearly indicate that both the polarity of the support surface and preformed vacancy of the shell thickness affect the palladium migration process, which further determines its final aggregation in the egg shell. Extensive particles were found to be aggregated when palladium ions–water solution was typically employed, yet highly dispersed palladium particles were observed when the microemulsion method was applied due to the inhibition effect on the migration and aggregation process of primary particles. In the obtained 0.3%Pd@Al2O3 pretreated with polyoxyethylene(7–8) octylphenyl ether/cyclohexane microemulsion, a sharp active metal boundary and high dispersion of palladium were observed and hence, the obtained catalyst exhibited profitable activity, selectivity, and product distribution for 2-ethylanthraquinone hydrogenation.

Pd Nanoparticles on SBA-15 Containing F for 2-Ethyl-Anthraquinone Hydrogenation: Effects of Hydrophobicity

“…Catalyst supported on polyaniline coated SiO 2 showed higher selectivity than unmodified Pd/SiO 2 catalyst [27]. Bai et al proposed that hydrophobic surface of support could facilitate the dispersion of Pd particles and prevent them from aggregation [28]. In our previous work, Pd catalysts supported on organosilane functionalized SBA-15 by the grafting and co-condensation method, and carbon modified SBA-15 by transforming P123 inside SBA-15 channels were prepared and presented excellent activity [29][30][31].…”

Highly Dispersed Pt Catalysts on Hierarchically Mesoporous Organosilica@Silica Nanoparticles with a Core–Shell Structure for Polycyclic Aromatic Hydrogenation

“…The choice of the catalyst is critical in the hydrogenation of PAHs, as it can significantly affect the adsorption and dissociation energy barriers required for hydrogen activation . Noble metal nanoparticles (NMNPs), e.g., Pt, − Pd, − and Au, , are regarded as the promising catalysts for hydrogenation reactions, and more and more researchers are interested in the study of their performance. One of the challenges of NMNP hydrogenation is agglomeration of active metals, which finally results in the consequent loss in activity due to their high surface energy .…”

Fast, Large-Scale, and Stable Preparation of η-Al2O3 Microspheres by Fully Utilizing N,N-Dimethylformamide at Room Temperature

“…The particle sizes of alumina have effects on the recovery and inactivation of the catalyst in the liquid-phase catalytic reaction. , Therefore, the preparation of hierarchical activated alumina of micron size has attracted a lot of attention. Meanwhile, micron-sized-sphere-based catalysts are a good choice to increase their mechanical strength and reduce their fluid resistance. , Moreover, the alumina-supported noble-metal catalyst generally shows an egg-shell-like structure, and the spherical supports are more advantageous for the high dispersion distribution of the noble metals on their surface. , Therefore, the preparation of spherical alumina can effectively improve its application prospect. The cheap NaAlO 2 solution, as the most important intermediate of the Bayer process for the production of metallurgical grade alumina, is also an ideal aluminum source for the preparation of chemical alumina with special functions. , γ-Al 2 O 3 microspheres with particle sizes of ca.…”

“…15,18 Moreover, the alumina-supported noble-metal catalyst generally shows an egg-shell-like structure, and the spherical supports are more advantageous for the high dispersion distribution of the noble metals on their surface. 19,20 Therefore, the preparation of spherical alumina can effectively improve its application prospect. The cheap NaAlO 2 solution, as the most important intermediate of the Bayer process for the production of metallurgical grade alumina, is also an ideal aluminum source for the preparation of chemical alumina with special functions.…”